ORION Trapezium, November 2025, Vol. 51, Issue 11.

Vol. 51, Issue 11 https://zenodo.org/records/17613257 Fri 14 Nov 2025 JD2460994 ORION | Trapezium . A Monthly Publication of the ORION Astronomical Society Comet C/2025 A6 Lemmon, imaged by Don Spong at TAO on the evening of Monday Nov. 3, 2025, using a Celestron Edge HD telescope and a ZWO533MCPro camera. The comet was in Ophiuchus, visual magnitude ca. 4.8, at a distance of 0.87 AU from Earth. This is a stack of ~100 30-second frames. . Table of Contents 3 4 6 7 13 23 24 26 32 32 34 40 45 58 62 65 67 70 72 73 75 76 77 79 Ab initio Page Three Astronomy: “Astrocamera Safety Net” ……….………..……………..……… About ORION and TRAPEZIUM ……..……….……………...…………...……................ Messages from ORION President’s Message - Don Spong …………………………………….....….……..……..… TAO Director’s Message / Observatory Way - David Fields .…………………....……… ORION Board Meetings ElCantarito - Rob Fowler ……………………………..…….….. ORION Monthly Meetings ORION Monthly Meeting Format ….……………..……………….…….….……....……… ORION Meeting 19 Nov 2025: Lunar Impact Flash Project - Richard Piety ……….. ORION Last Month: Astronomy at the Obed WSR - Joshua Gray .…..……….....….… Events and Calendars, Sky Maps and Occultations Star, Moon, Comet and Meteorgazing at TAO in 2025 ……….………..….…..….….... TAO Public Stargazing: A Note Regarding Scheduling and Access in 2025 ..…..……. Public Stargazes in Nov & Dec 2025; TAOCalendars…………….…...……...…….……. Public Stargaze of 18 Oct 2025 - Ted Barnes ……………………………………………… The 623 Chimaera Campaign. Mon/Tue 20/21 Oct 2025 - Ted Barnes ………………… Private Public Stargaze of Mon 03 Nov 2025 - Ted Barnes …………………...…...…… The Evening Sky Map / Nov 2025 .…………………………….………….……..………...... Astrophotography The Comets of November: C/2025 A6 Lemmon and R2 Swan - Don Spong ..…….… Milky Way from the Grand Canyon - Don Spong ………………………………………… Appendices Astronumerology ……………………………………..…………………………………..…… The 80 Brightest Stars ………………………………….……………………………..……… Notable Star-Pair Angles …………………………..…………………………….…..……… Exeunt Poetica .………………………………………….…..………………….….……………..…… ORION and TAO General Information (and links) ………………………………..……... Trapezium back issues online …………………………………….……….……..…...…..… Fin du Journal …….…………………………………………………………………....…….. Page Three Astronomy The ORION Astronomical Society is a science and astronomy group founded in April 1974 by scientists from the United States Department of Energy facilities at Oak Ridge, Tennessee. We primarily serve the communities of Oak Ridge and Knoxville and the counties of Anderson, Knox, and Roane. ORION’s mission is to support scientific research, teaching, and astronomical activities in East Tennessee. We hold monthly public meetings at the Oak Ridge RSCC Campus, and are active at TamkeAllan Observatory (TAO), hosting public events, sharing knowledge of the skies, and helping to provide intellectually stimulating programs. ORION works to share the wonders of the cosmos and the culture of science. ORION members include scientists, engineers, technicians, IT experts, artists, students, and others with varied talents and expertise. Over half of ORION members own telescopes, many are amateur radio operators, and some have expertise in astrophotography. ORION has working relationships with several organizations, including museums and other amateur astronomy groups. Membership is open to individuals who will actively contribute their time and ideas. The annual membership fee is $20, and student discounts are available. There is no charge for our newsletters and publications, or for participation in most ORION activities. TRAPEZIUM is a monthly publication of the ORION Astronomical Society. The issue date is the Friday preceding the monthly ORION meeting, chosen to provide timely information regarding the planned Program. From March 2025 we have attempted to produce a somewhat shorter version of the Trapezium, which would still include important information regarding the monthly ORION presentation, as well as information regarding Public Stargazes and other notable events relating to ORION and TAO. The information removed includes a list of the brighter active supernovae, an observers’ equipment section, and personal “Meet ORION” mini-biographies. However we concluded that some components, such as a separate Astrophotography section, are so important for a publication on amateur astronomy that one really cannot justify excluding them. So, the new Trapezium is only somewhat shorter, by about 20 pages. ORION Board and Officers: President: Don Spong VP and Program Chair: David Fields Secretary, IT: Rob Fowler Treasurer: Bob Edwards Editor: Ted Barnes ORION Speaker POC: Richard Piety Member w/o Portfolio: Art Allison 4 Messages from ORION We’re getting into the winter viewing season, with crisp, cool weather and hopefully clear skies. Orion and the Pleiades are some of the most popular viewing objects this time of year. Who knows, maybe this will be the winter when we’ll get to see the red supergiant Betelgeuse finally go supernova. Keep your eyes peeled. We still also have a plethora of interesting comets to keep track of, including the mysterious and controversial 3I/ATLAS. November 6 is the full moon (Beaver moon – this is when beavers build their shelters), and the new moon will be on November 20, with November 22-23 a good dark sky weekend. A variety of planets are now visible, including Neptune, Saturn, Jupiter and Uranus. Saturn’s rings are very edge-on and narrow – they will not be that way again for another 15 years. The sun continues to be at solar maximum. November meteor showers include the Taurids (November 11 – 12) and the Leonids (November 16 – 17); however, the moon may still be fairly bright for the Taurids. We have quite a number of comets to look for: C/2025 A6 Lemmon, C/2025 R3 Swan, 3I/ATLAS (back in the northern hemisphere around December 5), C/2025 K1 ATLAS in Leo (magnitude 10.5) and 210P/Christensen in Libra (magnitude 11.8). Deep space objects of interest for November include Andromeda (M31) and its two companions, (M32 and M110); the Veil Nebula in Cygnus; the North American Nebula (NGC 7000); the Blinking Planetary Nebula (NGC 6826) in Cygnus; the Blue Snowball in Pegasus; the Helix Nebula (NGC 7293) in Aquarius; the double cluster (NGC 869 and 884) in the constellation Aquila; globular cluster M15 in Pegasus; the Ghost Nebula (Sh2-136) in Cepheus, the Pleiades (M45), the Bubble Nebula (NGC 7635) in Cassiopeia; NGC 7331 and Stephan’s quintet, and finally M33 in Andromeda. I wish you clear skies and good viewing! 6 President’s Message (cont.) - Don Spong 7 David Fields October 2025 The photo on the left shows our new road sign for Roane State’s Tamke-Allan Observatory (TAO). Traveling West on Caney Creek Road from Roane County Park, the sign appears on the left just after crossing Joiner Hollow Road. TAO offers Public Stargazes to the community on the 1st and 3rd Saturday of each month, weather permitting. Our usual schedule for the summer is to open at 8:30 pm and continue to nominally 10:30 pm -- later when the sky and attendance encourage this. Opening time changes according to the season, and a good guide is to arrive at the observatory about sunset, when weather is encouraging. These Stargazes are supported by local astronomy clubs, especially ORION members and friends, and benefit our students and community. Our TAO Stargazes are usually well attended, with a full classroom of visitors for evening astronomy lectures. TAO Public Stargazes and Special Events TAO Director’s Message / Observatory Way : What are rulers and Sky Rulers? Where do we carry them? A ruler is a tool for measurement of linear distance. Measurement can be a tool for understanding. We can define a Sky Ruler as a tool for measuring angular separation of objects in the sky. Let’s explore the need, the history of celestial angular measurement, and possible design for a modern Sky Ruler. In general, a ruler is useful only when it is in the hands of the user. For a hiker with a map, the ruler is in his hand with his map and compass. For a designer or engineer, the ruler is on his desk. For a medical technician, the same. The ORION Sky Ruler * * This is a reprint of the October 2025 article. This photo shows a plastic ruler that ORION gave to RSCC students and ORION members a few years ago, together with another of my favorite astronomy rulers: Astronomy Rulers For an astronomer, the sky ruler must be close at hand – in his/her pocket, or hidden on a reticle in his telescope eyepiece, or be part of a computer program. Once a telescope is aligned with the sky the astronomer may rely on the computer for many things, but if there is no computer, the astronomer needs the Sky Ruler in his pocket So, how may we obtain or design such a ruler? And how do we get it into the hands of ORION members and TAO students? The Sky Ruler should also present physical constants, show linear measurements (inches and cm), be inexpensive so we can give away as many as we like, identify ORION as a research-oriented group of enthusiastic, fact-oriented astronomers, and delight ORION members and students. This was the challenge I posed to our ORION board last Monday. We’re still thinking about this, so let us know your suggestions. Meanwhile, here are some background thoughts. Observatory Way (cont.) The ORION ruler (above) fulfilled several purposes. It was a nice Christmas gift to ORION members and students, plus it introduced students in my Astronomy classes to the idea that ‘measurements’ are important. It also introduced the metric system. It was an example of how ORION helps the college, in additional to helping the students with astronomy, and introducing astronomy and the night sky at our TAO stargazes. I wished many many times that it included much more information, but we found a nice price, provided that we kept the information short and simple. The TVIW ruler (in the image below) provided a perspective on the distance to the closest star systems, and presented some of the physical constants that define our system of units. These were both useful rulers, but they had disadvantages. The ORION ruler was durable, but too costly to give away in large numbers. TVIW ruler was made of cheap cardboard, but the TVIW ruler was inexpensive, so many were distributed. Both were good rulers, but they did not give a sense of measuring the sky – they were not actual “Sky Rulers.” A disadvantage of both rulers was that at a length of 6.5,” they didn’t easily fit into a shirt pocket or a wallet. What rulers might avoid these issues? Here are two examples, and I usually carry both: Observatory Way (cont.) Special-purpose rulers often have special functions that convert linear measures to other values, such as those for engineers (left, for a folded triangular ruler for dimensional scaling) and for medical technicians (right). Stardate: 2025.06.30 David presented Kevin with a gift ORION T-Shirt. David brought up shop type measurements he intends to do on the Meade. The group went on discuss various theoretical topics. Mention of 4 visitors who showed up at TAO and new member Kevin Wilson David brought up calendar access. Discussed problem with rotation of glow dome lid. Watch for migration of wheel axels. One axel migrated in and caused the lid to bind. Stardate: 2025.07.07 In attendance were Don, Ted, David, Art, Rob and visitor John Rather. Conversations opened with Ted discussing digitizing the occultation substacking project. David discussed a lightstrip project and possible application in the dome. Ted collected info for this month's Trapezium. David discussed attendance at the Sat July 5 Public Star Gaze, was 12, give or take. David discussed the testing we did on the Meade and saw no alignment errors. Stardate: 2025.07.14 In attendance were David, Ted, Art and Rob. Ted shared some mathematical analysis of the recent occultation data. David brought up potential dates for the next Friendship Star Gaze. We discussed the next ORION lecture and whether to zoom it or not. We discussed possibly having a news feature at ORION lectures. Stardate: 2025.07.21 In attendance were David, Don, Ted, Art, Rob... and guest John. Dave led the discussion with Rob's absence. Dave mentioned that Saturday night’s public star gaze was successful, with around 8 visitors. We discussed the recent lecture and the unplanned move to the computer classroom. The general consensus is that it went well. Dave will be away on August 2nd, the next star gaze. Ted brought up details of participation in the Tuesday night / Wednesday morning occultation. Stardate: 2025.07.28 In attendance were David Fields, Ted Barnes, Art Alison and Rob Fowler We will probably have a public star gaze at TAO on 8/2/2025, public or private depending on weather and Noah's decision. 8/12/2025 Perseid meteor shower a probable star gaze. 16 ORION Board Meetings (cont.) Stardate: 2025.07.28 Our Library display will expire soon. David will inquire if we can keep it another month or if we need to clean it out this month. If it has to come down, Ted & Rob have agreed to remove the contents. Stardate: 2025.08.04 Present were Don, Ted, Rob, Art and guest John Rather. Ted shared his most recent results and submission to IOTA that we have been re-evaluating. Don won’t be present for the August ORION meeting. We believe John Cliff is August's speaker. We discussed various lightning phenomenon We also discussed the Big Bang theory and John Rather's book. Stardate: 2025.08.11 Present were Don, Ted, David, Art, Rob and guests Richard Piety and John Rather. Ted reported on some of his recent results with IOTA’s python scripts and graphing. Rob reported on visiting Lily Bluff's Star Party at Wartburg, where he met Joshua, Gareth and Owen. Don told us of a new 16 bit color astro camera he just bought, a ZWO ASI2600MCP. John told us of an experience with a pro telescope. Richard just bought a QHY174M-GPS camera for recording timed asteroid occultations. We discussed weather regarding the Perseid meteor / stargaze, 8:30pm Tuesday, but the weather is deteriorating. There is a possible occultation on 8/23/25. Star date: 2025.08.18 In attendance were Ted, David, Art, Rob and guests John Rather and Richard Piety. David spoke to Courtney at AMSE about our ORION display. We have been invited to keep it set up for a while longer. We discussed possibly tracking 3I/ATLAS to get a pic, having an unscheduled observation evening. Star Date: 2025.08.25 In attendance were Dave, Ted, Richard and Rob. Ted shared the results of the recent asteroid occultation. David visited the K-25 interpretive center and described the layout. He said they are interested in us bringing a star party to that location. David noticed that one of the new pads in collecting water. Rob suggested a modified a port-a-potty as a camouflage telescope cover. Calling it "Astro-Johnny: Smelling like Roses!" 17 ORION Board Meetings (cont.) Star Date: 2025.09.01 In attendance were David Fields, Ted Barnes, Art Alison and Rob Fowler. And visitor David Allred. David Fields fixed the internet with at TAO and treated several ant colonies. The skies were good from 9pm to Midnight. Discussed an upcoming eclipse in Sydney Australia in 2 years. Ted spoke to the programmer of Occult Watcher [Hristo Pavlov] who helped him troubleshoot a bug. IOTA Annual meeting is next week on zoom. Star Date: 2025.09.08 In attendance were David Fields, Ted Barnes, Rob Fowler, Don Spong, Art Alison and Richard Piety. We has a successful Moon-gaze at TAO last night. Ted discussed his occultation studies. He was successful with one last night Sunday 2025.09.07. Richard attempted it too but has not analyzed his results yet. We had a new guest last night, Art’s friend Deirdre Akin. She joined the astroluncheon as well. Star Date: 2025.09.15 In attendance were David Fields, Ted Barnes, Don Spong, Rob Fowler and Richard Piety. We discussed concerns over who is coordinating speakers going forward. Tentatively, we believe Gareth Davies is our September speaker. We discussed news about the cosmic interloper 3I/Atlas and new spectral data. 18 ORION Board Meetings (cont.) ORION Board Meeting at the ElCantarito Mexican Restaurant, Oak Ridge, Mon 22 Sep 2025. L to R: Ted Barnes, David Allred, David Fields, Richard Piety, Rob Fowler, and Gareth Davies. Star Date: 2025.09.22 In attendance were David Fields, Ted Barnes, Robert Fowler, Richard Piety and guest, David Alred. Gareth Davis, Art Allison, and Don Spong arrive later. Ted and Richard discussed results of a recent occultation. Richard caught 2 new occultations recently. David expressed concerns over the success of last Saturday's Stargaze. He felt distracted and so thought it did not go well. But several of us thought it went very well. Gareth Discussed cosmic interloper 3I/Atlas, and its tail having recently turned green. Richard Piety confirmed that the ORION website is badly out of date. To support Public Star gazes, David discussed having teams of 2 to operate the Meade. Gareth talked about an astrophysicist, David Butler, who has a Youtube channel. Star Date: 2025.09.29 In attendance were Don, Ted, David, Richard, Art and Robert. Ted told us about his visit to New Mexico and the skies at Cloudcroft. David asked about an abstract for October’s guest speaker, Joshua from OBED. We discussed possibly meeting at TAO on Wednesday or Thursday. Star Date: 2025.10.06 In attendance were David Fields, Don Spong, Ted Barnes, Rob Fowler & Art Allison. David suggested we create something as a giveaway to members and students. He suggested a plastic ruler to help people understand angles. He also discussed making a custom planisphere. We discussed using Night Sky Network to coerce dues compliance. Art took up the challenge of creating a new giveaway / print project. Although this month’s speaker is confirmed, no details have been communicated. Etymology needed for the expressions “cattiewumpus” and “whackadoodle.” ORION Board Meetings (cont.) 19 Star Date: 2025.10.13 In attendance were Don Spong, Ted Barnes, David Fields, Rob Fowler and Richard Piety. •Winter Solstice is December 21, recommending having our winter solstice party on Saturday, Dec 20th. Possible locations: High Places Church. Don also suggested El Toro, a new Mexican restaurant in Oak Ridge. There is also a Chinese buffet, Hong's Asian Bistro, near Kroger's that might be possible. •David offered suggestions about a gift for TAO members. He showed an eclipse viewer he designed. •We discussed problems with the Meade mount and possible solutions. We also discussed adding a guide scope. •We discussed having a new Speaker POC and potential speaker for November. Richard volunteered to be acting Speaker POC for a while and see how it works out. Star Date: 2025.10.20 In attendance were David, Don, Art and Rob. •Don got a photo of Comet C/2025 R2 Swan at the recent stargaze. We had a large turnout at the star gaze because of a homeschool group. Attendance was around 30 or so. •Rob & Ted plan to go to TAO tonight to observe a 3am occultation. •We discussed plans for a Christmas/Solstice party. David and Don will check on the availability of 2 restaurants. •We discussed who is the key person for each of the various ORION social media assignments. •There is no official speaker chosen for November's meeting. ORION Board Meetings (cont.) 20 Star Date: 2025.10.27 In attendance were David Fields, Don Spong, Ted Barnes, Rob Fowler and Art Allison. Ted shared results from the most recent asteroid occultation, asteroid Chimaera. Considering 12/17 for the xmas party. Don & Rob shared details of 2 locations. David is designing a 3d joke. It's deep. Star Date: 2025.11.03 In attendance were Dave Fields, Don Spong and Robert Fowler •Discussed was the weather for a planned visit to TAO tonight. Agreed on a cut off of 4:30 pm to decide if weather permits. •David showed a printable planesphere for a youth project. •Don mentioned a new mini clamshell dome designed for small telescopes like the see-star. We also discussed how a See-Star is designed to be used remotely. •Rob asked if we have a speaker for this coming lecture. No specific was forthcoming. Star Date: 2025.11.11 In attendance were David Fields, Ted Barnes, Richard Piety, Rob Fowler, Don Spong, and guest John Rather. Art joined late. •We met at noon in deference to the "Lunar Flashes" zoom call at 3pm. Richard shared some general info about their mission. •Richard also mentioned a potential speaker, Fred Schumacher. •Ted bought a 2 inch moon filter to aid at public star gazes. •Richard and David discussed the general state of our web presence. ORION Astronomy has a website & a facebook page and Tamke-Allan Obs also has a website & facebook page. •We decided to go back to the bring your own beverage & covered dish for the xmas/solstice party. Possible dates? Sat 12/13. ORION Board Meetings (cont.) 21 ORION Monthly Meetings ORION Monthly Meeting Format Meeting Venue: City Room (A-111), just inside the main entrance, Coffey/McNalley Bldg., Oak Ridge Campus, Roane State Community College. 7:00 pm Eastern, 3rd Wednesday of each month. Our monthly meetings (except for December, a dinner) generally proceed as follows: •Welcome •Announcements •Invited Presentation and Discussion •Awarding of the Mug •Astrophotography / Special Presentations The nominal start time is 7:00 pm Eastern, on the 3rd Wednesday of the month. The beginning of the meeting will usually include announcements of general interest. Meetings typically continue until around 9:00 pm. Please plan to stay until the end. Hopefully we will all enjoy the astrophotography and other special topics discussed in the latter part of the meeting. Remote Viewing: A live Zoom session will usually be open during the ORION Monthly Meeting, at the link: https://us02web.zoom.us/j/88528735960?pwd=KzY4bnBHcjlhTzg3L3pOcjY0TFovUT09 or https://bit.ly/42apGxX Meeting ID: 885 2873 5960 Passcode: 716689 23 24 How to observe Lunar Impact Flashes (LIFs) Preparing for an observing campaign during the Geminids 2025 Lunar impact flashes (LIFs) are generated when a meteoroid, a solid object in the Solar System (typical sizes are centimeters to decimeters in diameter), hits the lunar surface at many kilometers per second and makes a small crater. Part of the energy of the impact is converted into a short flash, which can be observed with telescopes and a video camera. The aim of this project is to gather observations of lunar impact flashes around the time of the maximum of the Geminid meteoroid stream, from 12 to 14 Dec 2025. This will help train amateur astronomers in the skills of observing Lunar Impact Flashes. It will prepare them for a citizen science program to support the ESA LUMIO CubeSat mission, due to launch in 2028. LUMIO will observe LIFs against the lunar far-side, whilst orbiting around the so-called Lagrange point, L2, of the Earth-Moon system. Earth-based telescopic observations are needed during the LUMIO mission to help compare and calibrate near and far-side impact flash rates. But it is important that we start forming observing teams now to be ready for the mission in 2 years time. We would like as much video coverage of the night or earthshine portion of the Moon as possible from around the world, to demonstrate the useful capabilities of amateur astronomers to contribute to scientific studies. Because of issues O R I O N October 15 P r o g r a m Title: Lunar Impact Flash Project (Recorded Zoom Meeting) Abstract: Speaker (Host): Richard Piety ORION Meeting Speaker POC LIF Project participant 25 O R I O N October 15 P r o g r a m Title: Lunar Impact Flash Project (Recorded Zoom Meeting) Speaker (Host): Richard Piety ORION Meeting Speaker POC LIF Project participant Because of issues with false flashes from cosmic rays, artificial objects sunglint etc., we strongly encourage simultaneous observations from widely geographically separated observers. This is an excellent way to discriminate true flashes from the noise. The study of these impact flashes will help us to better constrain the impact rate of these small objects on the Moon. This is relevant for future human exploration of the Moon - we will want to know how many objects, and more importantly impact ejecta, might hit a Moon base, lander, rover, or a spacecraft orbiting the Moon. It is also important for science as newly formed craters have and will be discovered, that are linked to specific impact flashes. Observing these impact flashes can be done with equipment that many amateur astronomers have access to. Impact flashes have been observed with telescopes as small as 13 cm aperture. Of course, larger aperture scopes, permit fainter (and more frequent) flashes to be detected. Successful recordings have been done with analog Watec or digital ASI type cameras capable of videoing the night side of the Moon at least 10 frames per sec and capable of recording starts down to magnitude 10 at these frame rates. The typical time between detectable impact flashes is a few hours but as there is a strong meteor shower on during 12-14 Dec, we would expect to capture a few impacts during this time. Authors: Detlef Koschny, TUM, Tony Cook, U. of Aberystwyth, Lisa Maria Alessi, IMATI-CNR. Abstract text Copyright © 2025 IMATI-MI, Laboratorio Sistemi Informativi Multimediali. Abstract (cont.): We enthusiastically invite visitors to attend our Public Stargaze events, held at our darksky site, the Tamke-Allan Observatory (TAO) near Kingston, Tennessee. These events are intended especially for visitors, so our buildings and facilities will be open, and there will be astronomy talks as well as public skywatching. In Jan-Jun 2025 we plan to hold fixedcalendar public Stargaze events on the 1st and 3rd Saturday of each month. These weekend events are especially appropriate for families. We also hold public special events, such as a “Full Moonrise,” with associated Moon Music, and the occasional comet watch. The annual Perseid Meteor watch in mid-August is especially popular. The precise dates of many of these events depend on the local weather conditions, and cannot be specified definitively long in advance. As an approximate guide, see the TAOCalendar pages following. Once a date is finalized we usually confirm it through the ORION online message site ORION [email protected]. Likely and unlikely dates for TAO events may be inferred from the weather predictions at TAO by Clear Sky Charts (cleardarksky dot com) and Astrospheric (astropheric dot com). Please confirm event dates before proceeding to TAO. In view of the rather challenging approach road to TAO, “Observatory Way,” first-time visitors should plan to arrive before dark. Driving instructions are given at: https:// www.roanestate.edu/pages/obs/visit.htm Some instructions follow, since people may be unfamiliar with procedures for stargazing at a dark-sky site. ORION members are invited to arrive early with their telescopes and mounts, to prepare for evening observing and to share refreshments. Please bring a red flashlight, or a headband with a red-light option. Visitors who wish to acquire red lights or red-light headbands for observing may find them at many commercial amateur astronomy sites, such as https:// www dot high pointscientific dot com. The “Lepro LE” LED Headlamp, model 3200008, available from Amazon for about $10 (Aug. 2024) is a personal favorite. This is rechargeable and has separate red and white led buttons, with several brightness settings. A caution: For amateur astronomy, brighter lights are NOT preferred, and WHITE lights are highly discouraged. Please use only red lights while the Stargaze is in progress. Parking is available on site; on entering TAO stay to the right, and please use the parking area below and right (Southwest) of the TAO buildings and observing area, near the treeline. And PLEASE NO HEADLIGHTS ON SITE. Visitors are encouraged to interact with ORION astronomers who have set up and may be operating telescopes and other astronomical equipment. We enjoy public discussions, and regard this sharing of information as a primary goal of our organization. Visitors are welcome to coffee and other refreshments. v. 4 Mar 2024 (Trapezium) Star, Moon, Comet and Meteorgazing at TAO in 2025 TAO Public Stargazing: A Note Regarding Scheduling and Access in 2025 In 2025 we are reverting to an earlier schedule of having our Public Stargaze nights on every first and third Saturday. Of course this assumes good weather; if the weather is not suitable, a changed schedule will be announced on the group site ORIONastronomy @ groups.io. We decided that the previous (2024) schedule of a once-monthly Public Stargaze was insufficient, and having a Moon visible in some phase other than close to New gives our visitors an obvious and interesting object for viewing. During Daylight Savings Time (mid-March through early November) we plan to hold our Public Stargaze events over the hours of approximately 8:00 pm - 11:00 pm, with some nominal variation. If it is already dark when you arrive, please dim your headlights on the TAO grounds, follow the right branch of the access road, and park to the right of the TAO building, near the treeline. Note: Parking in or near the elevated flat observing area at the front (East) of the TAO building is reserved for astronomers who are bringing their equipment. Additional information for visitors may be found on the previous page and following two pages of this issue. 33 34 TAO Public Stargazes in November: Sats 01 & 15 Nov 2025 Sunset 6:43 pm Civ dusk 7:10 pm Ast dusk 8:10 pm Moonrise 4:23 pm Moonset* 3:31 am *02 Nov Sat 01 Nov 2025 Waxing Gibbous Moon. Bright Moon during this event. Sunset 6:32 pm Civ dusk 6:59 pm Ast dusk 8:01 pm Moonrise 3:56 am Moonset 4:04 pm Sat 15 Nov 2025 Waning Crescent Moon. No Moon visible during this event. Moon illum. 79% Moon illum. 19% TAO Public Stargazes in December: Sat 06 & 20 Dec 2025 Sunset 6:25 pm Civ dusk 6:54 pm Ast dusk 7:57 pm Moonrise 8:10 pm Moonset* 11:35 am *07 Dec Sat 06 Dec 2025 Waning Gibbous Moon. Bright Moon during this event. Sunset 6:26 pm Civ dusk 6:55 pm Ast dusk 7:58 pm Moonrise 9:31 am Moonset 6:52 pm Sat 20 Dec 2025 Waxing Crescent Moon. No Moon visible during this event. Moon illum. 96% Moon illum. 0% TAO Calendars Jan-Jun & Jul-Dec 2025; Nov & Dec 2025 The principle public events for visitors at TAO are the Public Stargazes, held at TAO during 2025 on the 1st and 3rd Saturday of each month. These are listed in the “Public Fixed Events” TAO Calendar for six month periods, currently Jul-Dec 2025. These appear on the two pages immediately following. Additional notable events will be included in monthly “Special Events” TAOCalendars. These include public events that do not have a fixed date long in advance, such as the International Friendship Stargaze in Oak Ridge, and special TAO events such as Asteroid Occultations, Meteor Showers, Full Moonrises, Lunar (and other) Eclipses, Comet Watches, and perhaps the occasional musical event. These “Special Events” calendars for the current and subsequent months appear after the two six-month “Public Stargaze” calendars. The facilities in the TAO buildings onsite will be open to the public during the “Public Fixed Events,” and will also usually be available when TAO is open to the public for some of the “Special Events.” Please inquire regarding whether TAO will be open to the public for any “Special Event” you may wish to attend, since some may be restricted. We will of course always try to accommodate enthusiastic visitors. We recommend checking a TAO website such as http://www. roanestate.edu/obs before visiting, to confirm that listed events will proceed as planned; weather conditions for example may require a cancellation or change of date. 35 date event details start end Sat 04 Jan 2025 1st Sat Stargaze 7:00 pm 10:00 pm Sat 18 Jan 2025 3rd Sat Stargaze 7:00 pm 10:00 pm Sat 01 Feb 2025 1st Sat Stargaze 7:00 pm 10:00 pm Sat 15 Feb 2025 3rd Sat Stargaze 7:00 pm 10:00 pm Sat 01 Mar 2025 1st Sat Stargaze 7:00 pm 10:00 pm Sat 15 Mar 2025 3rd Sat Stargaze 7:00 pm 10:00 pm Sat 05 Apr 2025 1st Sat Stargaze 8:00 pm 11:00 pm Sat 19 Apr 2025 3rd Sat Stargaze 8:00 pm 11:00 pm Sat 03 May 2025 1st Sat Stargaze 8:00 pm 11:00 pm Sat 17 May 2025 3rd Sat Stargaze 8:00 pm 11:00 pm Sat 07 Jun 2025 1st Sat Stargaze 8:00 pm 11:00 pm Sat 21 Jun 2025 3rd Sat Stargaze 8:00 pm 11:00 pm TAOCalendar Public Stargaze Jan-Jun 2025 These 2025 TAO Public Stargaze events are scheduled for fixed calendar days during the weekend, which will hopefully prove convenient for many visitors with families, especially those bringing younger astronomers. Cancellations often take place in Winter and Spring, due to cold or icy conditions, or overcast and rainy skies. www.roanestate.edu/obs www.ORIONinc.org v. 07 Jun 2025 cancelled cancelled cancelled cancelled cancelled cancelled cancelled cancelled cancelled date event details start end Sat 05 Jul 2025 1st Sat Stargaze 8:30 pm 11:30 pm Sat 19 Jul 2025 3rd Sat Stargaze 8:30 pm 11:30 pm Sat 02 Aug 2025 1st Sat Stargaze 8:30 pm 11:30 pm Sat 16 Aug 2025 3rd Sat Stargaze 8:30 pm 11:30 pm Sun 07 Sep 2025 “1st Sat” Stargaze 8:00 pm 11:00 pm Sat 20 Sep 2025 3rd Sat Stargaze 8:00 pm 11:00 pm Sat 04 Oct 2025 1st Sat Stargaze 7:30 pm 10:00 pm Sat 18 Oct 2025 3rd Sat Stargaze 7:30 pm 10:00 pm Mon 03 Nov 2025 “1st Sat” Stargaze 7:00 pm 10:00 pm Sat 15 Nov 2025 3rd Sat Stargaze 7:00 pm 10:00 pm Sat 06 Dec 2025 1st Sat Stargaze 6:30 pm 10:00 pm Sat 20 Dec 2025 3rd Sat Stargaze 6:30 pm 10:00 pm These 2025 TAO Public Stargaze events are scheduled for fixed calendar days during the weekend, which will hopefully prove convenient for many visitors with families, especially those bringing younger astronomers. Cancellations often take place in Winter, due to cold or icy conditions, or overcast and rainy skies. www.roanestate.edu/obs www.ORIONinc.org v. 24 Jun 2025 TAOCalendar Public Stargaze Jul-Dec 2025 cancelled cancelled moved moved www.roanestate.edu/obs www.ORIONinc.org date event details start end Sat 01 Nov 2025 1st Sat Public Stargaze 7:00 pm 10:00 pm Sun 02 Nov 2025 End of DST 2025 1:00 am Wed 05 Nov 2025 Full Moon 08:19 am Eastern Sat 15 Nov 2025 3rd Sat Public Stargaze 7:00 pm 10:00 pm Thu 20 Nov 2025 New Moon 01:47 am Eastern TAOCalendar Special Events (all times Eastern) Nov 2025 www.roanestate.edu/obs www.ORIONinc.org date event details start end Thu 04 Dec 2025 Full Moon 06:14 pm Eastern Sat 06 Dec 2025 1st Sat Public Stargaze 6:30 pm 10:00 pm Ddd nn Dec 2025 Festival of the Winter Solstice 6:00 pm t.b.a. Fri-Mon 12 -15 Dec 2025 Lunar Impact Flash (LIF) Campaign 00:49 am 12 Dec 2025 06:09 am 15 Dec 2025 Fri 19 Dec 2025 New Moon 08:43 pm Eastern TAOCalendar Special Events (all times Eastern) Dec 2025 Public Stargaze of Sat 18 Oct 2025 - Ted Barnes A surprisingly large group of home schoolers arrives at TAO. 8:13 pm, Sat 18 Oct 2025. Sunset 6:59 pm Civ dusk 7:25 pm Ast dusk 8:25 pm Moonrise 5:03 am Moonset 5:37 pm Sat 18 Oct 2025 Moon illum. 8% Waning Crescent Moon. No Moon was visible during this event. The word was that TAO would be open for this event by 7 pm, which sounded promising to those who liked to arrive early to set up their equipment. However there was also a suggestion from David that we arrive by 7:15 pm to discuss our plans for the evening, since a large number of scouts would likely arrive. I had updated an asteroid talk in the afternoon, so I felt ready to entertain an enthusiastic group of youngish visitors. Surely all adolescents like asteroids. However However it developed that the scouts had apparently postponed their visit, since the weather was overcast. Another group however did plan to appear, this being a group of homeschooled kiddies. OK that sounds fine, too. All kids like telescopes, right? However the numbers were not quite as expected. First quite a few arrived with their parents, and came into the classroom and found places to sit. We don’t exactly have an excess of chairs, but we did our best to accommodate them. Public Stargaze of Sat 18 Oct 2025 (cont.) Our SRO audience lining the wall. Initially we appeared to be doing ok, and David began a welcome address, which evolved into a talk about Sky Rulers. This was regularly interrupted as more and more kiddies arrived, seemingly doubling and even tripling the initial numbers. I was concerned about their comfort, as the room was now basically standing room only. Normally one might expect an overflow crowd to populate the outside for views of the sky, but the sky was unfortunately overcast, so everyone appeared happy to stay inside for the lectures. I had prepared a talk about the asteroid occultation we had observed at TAO, and people seemed happy to hear about asteroids. I assumed that the kiddies associated them with dinosaurs. In any case our large audience (of perhaps 25) seemed quite happy. 41 48 Path of the shadow of asteroid 623 Chimaera through the local region during the 3:16 am Eastern occultation of 21 Oct 2025. Image from Occult Watcher. The center of the path is a green line, with the expected shadow edges in red. The TAO site is indicated, and the parallel faint grey chords show the transverse locations of other observers on the asteroid’s profile. The Chimaera Campaign. (cont.) TAO 49 Position of asteroid 623 Chimaera in Andromeda at the time of the occultation. 3:16:42 am Eastern, 21 Oct 2025. Image from TheSkyX. Mirach 623 Chimaera Peg Psc The Chimaera Campaign. (cont.) Scheat Alpheratz Markab Algenib Almaak There is an interesting phenomenon at TAO, which is that sporadic visitors will arrive hoping to participate in astronomy even when there has been no announcement of a public event, especially on notably clear, dark nights. This evening we had five visitors, despite there being no official announcement of TAO being open! The first visitor, James McCarthy, was looking for a site where it might be possible to view the two comets (Lemmon and Swan) which had been in the news of late. These are early evening objects which are currently just at naked-eye magnitudes, so we could at least tell him where they might be found. He was quite knowledgeable about astronomy and we encouraged him to visit TAO in future, but he had just sold his residence and was moving to Idaho in the very near future, so that was that. Next to appear was a young couple who were interested in seeing the Orion meteors, and were happy to remain in their car, and accidentally turned on their lights surprisingly often. Rob then volunteered to drive to civilization and return with some drinks and snacks; coffee especially appealed to me. While Rob was gone another car appeared wirh two women and two dogs, who also left their lights on initially, and called to me (Ted) by name. I assumed I knew them from some past astronomy event, but they had actually just encountered Rob on our access road, who encouraged them to visit TAO. They were on a major driving holiday from New York City (!), and were looking for a location where they might view the night sky. As it developed they were very enthusiastic about astronomy, and had many questions for us. When Rob returned he used the Meade to show them views of Saturn, the Orion Nebula and other sights, and they enjoyed discussing Jersey. I showed them my observing setup, and explained tonight’s asteroid occultation. Their little dogs remained unfriendly throughout. While Rob had been out looking for supplies I had recalibrated my own PHD2 guiding program (which I think actually made it worse; it had been running very well earlier in the evening). I had earlier finished my CPWI alignment by accepting the program’s offer to run ASPA (the All Star Polar Alignment routine), which I normally decline, to save time and effort. According to the CPWI program’s numbers, ASPA vastly improved my polar alignment, so the PHD2 guiding corrections now appeared much less significant. I was well rewarded by my careful, leisurely alignment on 10 stars “from scratch” earlier that evening, these being Alioth, Mirfak, Caph, Mirach, Edasich, Eltanin, Vega, Albireo, Rasalhague and Nunki, after I had initially aligned the mount’s platform on Polaris. We also worked on off-axis guiding on the Meade, and tried to get it to work using PHD2, but I had no experience with this technique, so we mainly learned that the obvious PHD2 parameter guesses didn’t appear to work. Rob will likely benefit from future online background reading regarding how to implement this technique on the Meade. The Chimaera Campaign. (cont.) 51 With the departure of our visitors around midnight we settled in for the long wait until 3:16 am and the occultation, Rob experimenting with Meade control, and me doing “station keeping” at my 8” ORION Ritchey-Chrétien Astrograph. As the event would take place high in the West, near Alt@Azi = 63o@278o, one might think that one could find a bright star near the faint target star and simply let the system guide on that bright star through the evening. As the target star was close to Mirach (b And), it might seem the obvious choice. However this was not feasible, as is clear from the Alt-Azi position of the target star through the night: Time Eastern target star position (Alt@Azi) 09:00 pm 20 Oct 42o @ 72o 10:00 pm 53o @ 77o 11:00 pm 65o @ 82o midnight 21 Oct 78o @ 88o 01:00 am 89o @ 165o 02:00 am 78o @ 272o 03:00 am 66o @ 278o event: 03:16:42 am 62.4o @ 279.0o 04:00 am 54o @ 283o Ouch! Since the target star would evidently pass very close to the zenith, reaching a maximum Alt of 89.45o just before 1:01 am, trying to guide on the event region through the night clearly invited a disaster, with a coordinate singularity and a possible mountOTA collision. I instead decided on the less dramatic procedure of slewing to a position of roughly Alt@Azi = 40o@275o, where I would hop between bright stars, waiting for the occultation region to approach. Accordingly I hopped between Markab and Scheat, and then the higher-Alt pair Algenib and Alpheratz, as the night passed. Around 1am a new complication arose. Dew! Who could have anticipated dew late on a cold October night? What an oversight! Soon my work table and keyboards were damp, and it grew worse as the early morning hours progressed. My computer monitors misted over, and I had to remove their red plastic sheets. I used most of a role of paper towels I had fortunately brought in trying to keep the work areas, the OTA and its light shield dry. As we passed 2:30 am they were all very damp. Guiding was now failing after a few secondsI found condensation The Chimaera Campaign. (cont.) 52 Looking back to the East before the event, one can see Orion, Sirius and Procyon at right, and at upper left Gemini, featuring a bright Jupiter. 2:36 am Eastern, 21 Oct 2025 The Chimaera Campaign. (cont.) seconds, and I found condensation covering the guidescope’s front lens. I dried it as best I could and put the lens cap back on the guidescope, hoping to save a guiding capability for the event itself if needed. I was now quite worried about condensation on the OTA’s primary mirror, especially when the OTA would be elevated to the higher Alt where the event would occur. Occasionally we were helped by a light breeze, but the condensation seemed to return, “wetter” with each encounter. This was becoming a disaster. As we entered the final 30 minutes before 3:16 am I simply had to ignore these problems and proceed approximately as planned. I slewed the OTA out of the safer, dryer lower Altitudes, up to “d And” at 2:45 am, and then still higher to Mirach at 3:00 am. At least SharpCap’s plate solve and resync function had been working on most attempts; this was valuable in confirming my location. I then did a “Go To (RA, Dec)” slew to the target area, and at 3:08 am noted that I could see the tiny close pair of target star and asteroid in the field. (They were of very similar brightness, according to Occult Watcher having magnitudes of 13.8 for the asteroid, and 13.9 for the target star.) The field stars matched my little sketch map, albeit inverted as usual. I just had to survive the next few minutes. 53 Next yet another potential disaster arose. Rob yelled at me from the glow-dome where he pointed his laser into the sky, illuminating a low layer of fog overhead drifting up from Watts Bar Lake. Great. I think I replied “I don’t wish to know that.” since I already had enough problems. But there were admittedly already hints of fog in the air. Just a few minutes to go … Rob came over to watch developments. After I pointed out the nice starand-asteroid close pair still visible on my damp display screen, at 3:15:00 am as planned I hit the Start Capture button on SharpCap. I had set SharpCap to record a 400-frame SER movie of longish 500ms@Gain480 frames, with the maximum camera gain chosen to aid in recording these two faint 14th magnitude objects. This would record the period 3:15:00 - 3:18:20 am, with the predicted occultation midpoint of 3:16:42 am hopefully being close to the middle of the SER movie file. Perhaps unnecessarily (and recklessly?) I captured 1920x1200 full frames, each about 2.3 MB. Also, a few days earlier I had attached an 0.75x photoreducer to the QHY174MGPS camera, so I was recording a field about 31’ x 19’ in extent, somewhat larger than usual. About 5 minutes before the occultation the asteroid and star could no longer be separated visually, and we watched this combined image on the screen as SharpCap was capturing the frames. The question was, would we see any dimming during the occultation as the asteroid eclipsed the target star, and the combined 13.1-magnitude source dimmed to a single 13.8-magnitude asteroid? We watched the image carefully as the predicted occultation time approached. Then it arrived, and you could easily see the pointlike object drop considerably in brightness. It remained dimmed for about 2 seconds, and then came back to full brightness. We had seen a 13.9-magnitude star being occulted “live” on the screen! We were now very happy and enthusiastic people. Despite the many complications we had seen the event, and once SharpCap finished its task, we had recorded it as well! The Chimaera Campaign. (cont.) 54 A lightcurve plot from the SER image file, generated by Pymovie, showing the brightness of the target star UCAC4 626-004193 (blue), a brighter comparison star (green), and an empty field region (red). The occultation takes place near the middle of the plot, as planned. On 25 Oct my UVa colleagues used the PyOTE fitting program to find a solution with the highest SNR, with disappearance and reappearance times [Eastern] and a duration (with 1s error bars) of D = 03:16:40.21(6), R = 03:16:42.13(6), and dur = 1.92(2) secs. The disappearance time was about 1 to 2 seconds earlier than predicted, depending on the reference. Success! target star UCAC4 626-004193 comparison star no star The Chimaera Campaign. (cont.) 55 This is a single 4sG400 exposure centered on 3:22:58 am Eastern, 21 Oct 2025, 6m17s after the occultation. The pair is g-mag 13.9 target star UCAC4 626-004193 (L) and mag 13.8 asteroid 623 Chimaera (R), at a separation of ~ 4 px, consistent with the expected separation of about 4.0” at the time of this image. The bright star is the type G5 g-mag 7.8 star SAO 54610, at a distance of 2’10” from Chimaera. In this image N is up and E is left. The Chimaera Campaign. (cont.) 623 Chimaera target star, UCAC4 626-004193 SAO 54610 56 Of course the evening didn’t end with the successful observation and imaging of the occultation. Afterwards there was the requisite period of sitting around admiring the sky, and feeling good about everything. For future reference, fog from Watts Bar Lake doesn’t necessarily dissipate immediately after the astrophotography ends. In this case it continued to thicken as we packed our equipment, and by about 4pm only a few bright stars were still visible through the fog. Hand lasers could be used to identify fog layers, see image below. We had been very lucky with the timing of the occultation. A fog layer at TAO illuminated by a hand laser. 3:30 am Eastern, 21 Oct 2025 The Chimaera Campaign. (cont.) 57 The final results of this campaign will depend on an analysis by the UVa group, once they have results from all the participating observers. As of 23 Oct 2025, 7 of the 19 stations listed by Occult Watcher as participants had reported their preliminary observed occultation durations, ranging from 3.5 secs near the midline to 1.7 secs at 21.9 km from the midline. Our result from TAO of about 1.9 secs at 18.0 km from the midline appears roughly consistent with the other results reported to date. Once the results of the individual sites and their associated occultation timing datasets have been reviewed by the collaboration in a careful reanalysis, they plan to release accurate results for the extent of 623 Chimaera, together with an approximate profile of the asteroid. The expectation is that these results will be published in several months. This will undoubtedly be a great improvement over the previous estimate of a diameter of ca. 44 km, apparently from one observation of an earlier occultation. The most amusing of the observers’ brief comments reported in Occult Watcher to date is that of David Durham, from a station at -8.4 km from midline. He reports: “No observation – Chased off site by Indian Reservation police.” The Chimaera Campaign. (cont.) 64 Astrophotography Many comets have been passing through the inner solar system recently. I’ve been fortunate to be able to get to TAO on clear nights to image two of these: C/2025 R2 Swan, imaged on October 18, and C/2025 A6 Lemmon, imaged on November 3. C/2025 A6 Lemmon was low near the horizon in the West on November 3 (dipping below the horizon around 8:30 pm), and C/2025 R2 Swan was higher, toward the South, on October 18. These images were made using my Celestron Edge HD, ZWOAM5 mount, Hyperstar attachment, ZWO533MC Pro camera, Williams optics guide scope, and ZWO220MM guide camera, all controlled by my ZWO ASIAIR. Around 100 30-second images were stacked for C/2025 A6 Lemmon, and 31 30-second images for Swan. C/2025 R2 Swan – imaged at TAO October 18 The Comets of November - Don Spong The Comets of November (cont.) C/2025 A6 Lemmon – imaged at TAO November 3 Milky Way from the South rim of the Grand Canyon looking North During the week October 21 to 26 I was in Arizona attending my 59th high school reunion. We had arranged as part of the trip to spend one night (October 24) at the Grand Canyon. The nighttime skies there were phenomenal, with better views of the Milky Way than I have ever seen at dark sky sites in Tennessee. Below are two images I took of the Milky Way from the South Rim, where we stayed. These were done using a Sony alpha 7-III mirrorless camera with a 12mm lens on a tripod. I took about twenty 25-second exposures and stacked them using the software Sequator. The first image is looking to the northern end of the Milky Way and the second is looking to the southern end. Milky Way from the Grand Canyon - Don Spong Milky Way from the South rim of the Grand Canyon looking South Milky Way from the Grand Canyon (cont.) 69 Appendices Astronumerology - tb Some numbers are quoted to several-digit accuracy where appropriate. Exact numerical relationships are indicated as such. 1 ly = 1 ly (Julian) = exactly 9 460 730 472 580. 8 km = 63 241. 077 084 … AU c = speed of light = exactly 299 792 458 m/s = exactly  1 ly/yr. 1 AU = exactly 149 597 870. 7 km 1 parsec (pc) = 3. 261 598 … light years (ly) 1 yr (Julian) = exactly 365.25 d = exactly 31 557 600 s 1 d = exactly 86 400 s distance to a Cen A = 1.346(2) pc = 4.390(8) ly distance to the center of the galaxy ~ 8 kpc ~ 25 kly (considerable uncertainty) 1 nm = 1 nanometer = 10-9 m exactly Ha wavelength = 656.2 nm + 0.5 change in magnitude = exactly 101/5 x fainter = 1. 584 893 … x fainter + 1 change in magnitude = exactly 102/5 x fainter = 2. 511 886 … x fainter + 2 change in magnitude = exactly 104/5 x fainter = 6. 309 … x fainter + 2.5 change in mag = exactly 101 x fainter = 10 x fainter + 3 change in mag = exactly 106/5 x fainter = 15. 848 … x fainter + 4 change in mag = exactly 108/5 x fainter = 39. 810 … x fainter + 5 change in mag = exactly 102 x fainter = 100 x fainter + 6 change in mag = exactly 1012/5x fainter = 251. 188 … x fainter + 7.5 change in mag = exactly 103 x fainter = 1000 x fainter + 8 change in mag = exactly 1016/5 x fainter = 1584. 893 … x fainter + 10 change in mag = exactly 104 x fainter = 10 000 x fainter + 20 change in mag = exactly 108 x fainter = 100 000 000 x fainter Brightness is proportional to 1 / distance2 10 x more distant = exactly 102 x fainter = + 5 change in magnitude 102 x more distant = exactly 104 x fainter = + 10 change in mag 103 x more distant = exactly 106 x fainter = + 15 change in mag Absolute magnitude Mabs is the brightness as seen from a distance of 10 pc. Mabs (our sun) = 4.83 17th mag is about 1 optical photon / cm2 s ( Barnes’s rule  ). 70 Astronumerology (cont.) Some numbers are quoted to several-digit accuracy where appropriate. Exact numerical relationships are indicated as such. R.A. = RA = Right Ascension = the angle f around the celestial polar axis, usually quoted in hours, minutes, and seconds (h m s); analogous to longitude. Dec = Declination = the angle q above the celestial equator, usually quoted in degrees, minutes, and seconds ( ° ' " ); analogous to latitude. The RA (f) and Dec (q) angles, together with a reference epoch such as J2000.0, specify an object’s direction in the sky. A unit length vector (“unit vector”) h pointing towards an object in the sky (“on the celestial sphere”) in terms of RA (f) and Dec (q) angles is given by h = cos(q) cos(f) x + cos(q) sin(f) y + sin(q) z = C (c x + s y) + S z The arc angle Q12 between any two directions in the sky h1 and h2 (or any two stars) using the dot product formula and some obvious abbreviations, satisfies cos(Q12) = sin(q1)sin(q2) + cos(q1)cos(q2)cos(f1-f2) = S1S2 + C1C2c1-2 1 degree = p/180 radians = 1.745 10-2 radians 1 arcmin = p/10800 radians = 2.909 10-4 radians 1 arcsec = 1 asec = p/648000 radians = 4.848 10-6 radians 1 mas = 10-3 asec = 4.848 10-9 radians 1 asec @ 1 km = 4.848 mm 1 asec @ 1 AU = 725.3 km 1 asec @ 1 pc = 1.0000 AU 1 mas @ 1 kpc = 1.0000 AU Image scale [asec/px] = 206.3 * pixel size[mm] / focal length [mm] JD = Julian Date (Astronomer’s calendar) = a simple count of days starting at noon UT on Monday 1 Jan 4713 BC. That date and time was the start of Julian Day 0. The current JD can be inferred from the value on the cover of the Trapezium. 71 1 Sirius 02 Canopus 03 alpha Centauri A 04 Arcturus 05 Vega 06 Capella 07 Rigel 08 Procyon 09 Archenar 10 Betelgeuse 11 beta Centauri 12 Altair 13 alpha Crucis 14 Aldebaran 15 Antares 16 Spica 17 Pollux 18 Fomalhaut 19 Deneb 20 Mimosa 21 Regulus 22 Adhara 23 Castor 24 Shaula 25 Gacrux 26 Bellatrix 27 Elnath 28 Miaplacidus 29 Alnilam 30 Regor 31 Alnair 32 Alnitak 33 Alioth 34 Dubhe 35 Mirfak 36 Wezen 37 Sargas 38 Kaus Australis 39 Avior 40 Alkaid 8.709 0.0054 309. 16. 4.395 0.0083 36.72 0.22 25.04 0.069 42.81 0.26 863. 78. 11.46 0.051 139.4 3.4 498. 63. 392. 24. 16.73 0.049 322. 16. 66.64 1.05 554. 94. 250. 13. 33.78 0.09 25.13 0.09 1410 200 279. 23. 79.30 0.67 405. 7.0 50.68 0.032 571.2 7.5 88.56 0.43 252.4 10.2 133.9 1.9 113.2 0.43 1980 540 1120 110 101.0 0.66 736. 106. 82.55 0.42 122.9 2.2 506. 13. 1610 300 300. 41. 143.3 1.5 605. 47. 103.9 0.79 41 Menkalinan 42 Atria 43 Alhena 44 Peacock 45 Alsephina 46 Mirzam 47 Polaris 48 Alphard 49 Hamal 50 Diphda 51 Mizar 52 Nunki 53 Menkent 54 Alpheratz 55 Mirach 56 Rasalhague 57 Algieba 58 Kochab 59 Saiph 60 Denebola 61 Algol 62 Tiaki 63 Muhlifain 64 Aspidiske 65 Suhail 66 Alphecca 67 Mintaka 68 Sadr 69 Eltanin 70 Schedar 71 Naos 72 Almach 73 Caph 74 Izar 75 alpha Lupi 76 epsilon Centauri 77 Dschubba 78 Larawag 79 eta Centauri 80 Merak 81.1 0.46 390.6 7.0 109.3 8.2 178.8 5.1 80.6 0.78 492.7 16.4 432.6 6.3 180.3 1.8 65.8 0.33 96.3 0.46 81.1 0.93 227.8 4.6 58.8 0.21 97.0 1.01 197.4 6.7 48.6 0.77 130.1 2.7 130.9 0.63 974. 37. 35.9 0.21 89.9 3.47 177.0 4.0 130.2 1.5 765.6 18.0 544.5 10.0 77.2 1.79 692.5 85. 1830 270 154.3 0.7 231.5 8.2 1080 40 393.0 49. 54.7 0.35 235.9 8.4 464.6 11. 427.5 27. 491.2 66. 63.7 0.27 305.7 6.0 84.5 2.5 The 80 brightest stars (c/o Wikipedia), and their distances from Earth in light years, with errors (from Gaia data, or Simbad if needed as an alternative). The 80 Brightest Stars 73 Schedar Caph 5 -0.085 1.7 Betelgeuse Alnitak 10 0.017 0.17 Capella Castor 30 -0.023 0.077 Procyon Mirzam 30 -0.094 0.31 Elnath Alnilam 30 -0.096 0.32 Alpheratz Caph 30 0.060 0.20 Aldebaran Pollux 45 0.013 0.029 Betelgeuse Algol 50 -0.033 0.066 Alnitak Naos 50 -0.049 0.098 Pollux Alioth 60 0.065 0.11 Gacrux Alphard 60 -0.001 0.002 Regulus Bellatrix 70 -0.030 0.043 Sirius Mirfak 80 -0.094 0.12 alpha_Centauri Regulus 90 0.057 0.063 Vega Denebola 90 -0.065 0.072 Fomalhaut Caph 90 0.006 0.007 Deneb Alnilam 120 0.059 0.049 Menkent Mintaka 120 0.000 0.000 Sirius Alphecca 135 -0.089 0.066 Aldebaran Antares 170 -0.021 0.012 Notable star pairs (from the set of the 80 brightest stars listed above) that are close to a multiple of 5o separation. The angles are in degrees. Notable Star-Pair Angles Q Dq defect (%)