Up to date comet elements

[John O’Neill]

Hi,

I was observed Comet ATLAS 2019 Y1 last night (2020 Apr 17 at 08:40 UT) and I noticed it appeared 15′ SE from its plotted position as plotted in Guide 9.1. Skytools 4 showed the same plotted position as Guide. I did the automatic elements update in both programs. I saw the comet near TYC 4029 714, while the programs plotted it near HIP 4239. The path of the comet on ‘Astrosite’ in the Netherlands was more in agreement with my observation.

Did anybody else notice this. Unless I made a blunder, I wonder are the MPC orbital elements out of date?

Please see the attachment, the red arrow shows my observed position.

John

Attachments:

1. 

   atlasY1-position.jpg
   

[Nick James]

John,

Yes, the current orbit from MPC for C/2019 Y1 (ATLAS) gives positions which are off by 5′.2 in RA and 12′.8 in Dec.

The position from JPL Horizons is much closer.

Mid time: 2020-04-15 20:23:52, S up.

[Derek Robson]

Hi John

That is an interesting observation – paying good attention to the detail in your observation, when you were unaware the prediction was out by a certain amount.   I made some quick un-tracked images of the comet the morning earlier 16/4/20 between 04:28 – 05:02 UT.   I was just curious as to whether I could find it. I’d been spending time previously on comets Y4 and T2, but noticed this comet Y1 listed on Heavens Above, so I thought I’d see if I could find it.  I was fighting against the bluing sky and should have went out earlier to try.  But it didn’t take long to find it by trial and error imaging the area.  I spotted a green ball against the dark bluish sky, so I thought that has to be it.  So ran off a few shots.  I’ll stack and post later.  I will assume that it will appear in the wrong position.  

Derek

[John O’Neill]

Hi Nick & Derek,

Yes, that’s a relief, JPL Horizons gave a better position. Please see the attachment for a JPL Horizons overlay in Guide 9.1 every hour (UT). By the way, when I checked JPL Horizons, the comet was in fact near TYC 4029 694, not TYC 4029 714.

I look forward to your images, Derek. It was a nice object visually in my 28 cm SCT at 80x, much better than C/2019 Y4 ATLAS.

Thanks, John

[Derek Robson]

Images taken with a Tamron 70-300 mm f5.6 lens and Canon 1100D on fixed tripod.

[Derek Robson]

Thanks for the map. (I’m not familiar with Guide 9).

In the images I uploaded, the comet is near the star HIP 3887 (the star shown by red cross), but my copy of Stellarium, with comet data updated at the time of posting ((choosing “Import orbital elements in MPC format“) ~04:00 UT, 19/04/2020), for time and date 04:55 UT 16/04/2020, also seems to be a bit out.  The comet on the map is still shown further away than what I imaged it at.  Map ref: Stellarium. 

[John O’Neill]

Hi,

Derek, that’s a nice photo from a fixed tripod. It’s good to see a Tamron lens still in use, I used one many years ago on my Olympus film camera. What focal length setting did you use?

The position in your photo is consistent with JPL Horizons. It would appear Stellarium uses the MPC comet elements.

John

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