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Mystery comets

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nickjames's picture
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Mystery comets

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.

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Mystery comets

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.

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Star fields

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.

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positions

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

 

 

 

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Processing

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?

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Astrometry.net has no

Astrometry.net has no problems with star trails, so it was an easy task.

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Star Trails

Thats really worth knowing. I have previously steered clear of trying to solve images with severely trailed stars assuming it would say "Sorry guv, no stars in here".

Stop Press: seems to depend on the aspect ratio of the trails. The longer a trail  is compared to its width the less likely it is to solve. Still worth knowing that Astrometry.net can be quite tolerant.

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Processing

Duplicate posting... sorry.

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Lars/Paul, That's a great

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/

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Astrometry

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.

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Arend-Roland

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 15.9

The 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.

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Three mystery comets solved

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 degs

Print 3
Comet C/1969Y1 Bennett
1970 May 6th at approx 04.40UT
Up is 358 degrees E of N
FOV 13 x 9.18 deg

Print 4
Comet C/1969Y1 Bennett
1970 May 4th at approx 01.15UT
Up is 358 degrees E of N
FOV 13 x 9.18 deg

Would someone like to check out my conclusions?
Can't help with observers though!

Peter

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Checking your work

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! 

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Print 8

Print 8 is also Arend-Roland.  Time of exposure is already given on the rear of the print.

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At sixes and sevens

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.

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I've updated the article with

I've updated the article with the results so far. Great stuff.

Nick.

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Print 5

I suggest this is 96P/Machholz 1 at approx 1970/06/04 23:00 UT 

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Print 1

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.

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Confirmation

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.

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Print 6

Following on from Paul:

I suggest this is C/1969 Y1 (Bennett) at around 1970/04/12 02:00 UT.

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fun

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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Prints 9 to 11

8P/Tuttle in Nov 1966?

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David,

David,

I think these are definitely Burnham. Stefan Beck has suggested dates and times. I've updated the page with the latest info although I may have missed some. Independent confirmation would be good.

Nick.

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Burnham end of April 1960 - Sky Safari

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Prints 6 and 7

Following on from Paul. Defo Bennett. Print 6, morning of 11 Apr 1970; print 7, morning of 10 Apr 1970. I may be wrong, but the bright star to the right of the comet in print 6 may be omicron And, with 2 And even further to the right.