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As a bit of a brain-teaser here are few comet-related mystery images to clear out the cobwebs after an excess of Christmas cheer. In the process of scanning comet prints for our section archive Martin Mobberley came across a number of prints which were not sufficiently well marked for us to make a good guess at the object, observer or date. These prints are set out here:
https://britastro.org/node/20231
Digital planetarium programs should allow us to make an unambiguous ID for the object and date. Observers may be a bit more difficult to identify but some digging in the archives may help to determine where people were on particular dates.
There are no prizes for getting the correct answers apart from the undying admiration of your Comet Section Director. Please post any potential IDs to this thread.
May I take the opportunity to wish you all a happy Christmas and let us hope for clear skies and a bright comet in 2020.
A little Christmas Quiz? 🙂
I do not know the dates or names of the comets, but If it can be of any help I can give the RA and DEC positions of the pictures.
I’m no good at identifying comets but I do know how to drive a plate solver. A local install of astrometry.net with the Gaia-DR2 database turns up the following for “Plate 1”.
RA,Dec = (111.067,63.945), pixel scale 20.1561 arcsec/pix.
Field center: (RA,Dec) = (111.072006, 63.929675) deg.
Field center: (RA H:M:S, Dec D:M:S) = (07:24:17.281, +63:55:46.828).
Field size: 3.21749 x 4.45504 degrees
Field rotation angle: up is 114.772 degrees E of N
Field parity: neg
Eyeball astrometry of the image gives a J2000 position for comet’s nucleus as 07:04:43.7, +63:26:31. Please feel free to precess that to B1950 if it helps identify the comet.
Looks like it might be clear again tonight. If so, solving the remaining prints will give me something to do while waiting for the photons to come in.
Here are some of the positions
Print 1
Center of picture is RA 07h 24m 23s Dec +63˚ 55’ 43” East is up.
Print 2
Center of picture is RA 02h 12m 24s Dec +66˚ 18’ 07” North is up
Print 5
Center of picture is RA 02h 14m 06s Dec +67˚ 33’ 51” North is up.
Print 6
Center of picture is RA 22h 49m 25s Dec +41˚ 53’ 58” East is up.
Bright star just to te right of comet is 2 And.
Print 7
Center of picture is RA 22h 35m 16s Dec +39˚ 41’ 38” East is up. The image is inverted.
Same field as print 6
Print 8
Center of picture is RA 08h 19m 23s Dec +61˚ 42’ 24s WSW is up. Field is 45’ x 58’
Bright star above comet is HD 68988
Print 9
Center of image is RA 20h 26m 30s Dec +59˚ 30’ 47” East is up.
Print 11
Center of image is RA 20h 46m 31s Dec +57˚ 27’ 25” East is up. Same field as print 9
I was wondering how you did that. In the earlier pictures the stars were starlike but images 9-11 contained significantly trailed stars. Is astrometry.net really that forgiving/tolerant or did you extract some positions manually as a text list?
Lars/Paul, That’s a great start with the plate solving. Now we just need to know which comets passed through those points to get the observation date and time. More difficult will be identifying the observers!
I too am surprised that astrometry.net is so good with trailed stars/
Lars didn´t post the precise positions of the comet nucleus. I could do so but don´t know if he intends doing so and I don´t really want to duplicate his efforts. If you have even a rough guess at the epoch for each plate the precise position should nail down the date and time of mid-exposure to a few minutes.
After a happy hour or two with Astrometry.net and JPL Horizons I’ve come up with these solutions:
Print 2
Comet C/1969Y1 Bennett
1970 May 23rd at around 00.00hrs + or – 1hr UT
Up is 7.61 degrees E of N
FOV 12.8 x 9.21 degsPrint 3
Comet C/1969Y1 Bennett
1970 May 6th at approx 04.40UT
Up is 358 degrees E of N
FOV 13 x 9.18 degPrint 4
Comet C/1969Y1 Bennett
1970 May 4th at approx 01.15UT
Up is 358 degrees E of N
FOV 13 x 9.18 degWould someone like to check out my conclusions?
Can’t help with observers though!Peter
This the JPL ephemeris of Comet C/1956 R1 (Arend-Roland) for the night of 1957-05-19/20
1957-May-19 21:00 A 07 03 54.81 +63 27 41.3
1957-May-19 21:10 A 07 03 57.35 +63 27 39.2
1957-May-19 21:20 A 07 03 59.89 +63 27 37.1
1957-May-19 21:30 07 04 02.43 +63 27 35.0
1957-May-19 21:40 07 04 04.97 +63 27 32.9
1957-May-19 21:50 07 04 07.50 +63 27 30.8
1957-May-19 22:00 07 04 10.05 +63 27 28.7
1957-May-19 22:10 07 04 12.59 +63 27 26.5
1957-May-19 22:20 07 04 15.13 +63 27 24.4
1957-May-19 22:30 07 04 17.67 +63 27 22.3
1957-May-19 22:40 07 04 20.21 +63 27 20.1
1957-May-19 22:50 07 04 22.76 +63 27 18.0
1957-May-19 23:00 07 04 25.30 +63 27 15.9The crude position I gave earlier suggests that mid-exposure was close to 21:35 UT.
Lars: do you have precise postions for the other plates? If so, please post them and I’ll happily do the detective work. If not. it will take me a little time.
Each of plates 6 & 7 are of Bennett, taken mid-April 1970. Can´t be more accurate without better astrometry.
Incidentally, http://www.icq.eps.harvard.edu/bortle.html is an invaluable resource. I use Norton’s 2000 to convert Bortle’s constellation names into approximate RA/Dec for comparing with plate solutions given by Lars.
Peter, I’ve had a look in Sky Safari and you are right.
P2, the brightest star in the frame is Segin, epsilon Cas
P3, ” ” gamma Cas
P4, ” ” gamma Cas
Nicely placed comets!
I suggest this is C/1956 R1 (Arend-Roland) at approx 1957/05/20 01:00 UT. Sky Safari places the comet at that time 07 04 55 +63 26 46 J2000.
Good to see someone is checking my work to guard against errors. I should do the same for that of other workers.
My earlier post gave a time of 1957-May-19 21:35. Agreement is satisfactory.
This was funny.
Astrometric.net was a fine tool, and I have passed some time today checking (=finding) the positions on Atlas Stellarum.
I look forward to the final results form the pro guys.
A merry christmas to all.
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