Imaging comets in the twilight

Blog the previous nights viewing. Link to images on the gallery or simply describe what you observed the night before. Leave the technical and howto in another forum.
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rwilkinson
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Location: Bolton

Imaging comets in the twilight

Post by rwilkinson » Sat May 09, 2020 11:50 am

Last night I got some more images of the demise of comet 2019 Y4 (ATLAS), which began to disintegrate last month.
It was also a test of imaging a comet low down in the evening twilight, as a practice for C/2020 F8 (SWAN) later this month.

Sunset was only at 20:53, so it wasn't that dark by 10pm, but I could just see Polaris in my polar-scope and Capella for alignment and focussing.
I got my first image of the comet at 10:15, when the sky background was so light that I had to limit my exposures to 30-sec:
c2019y4_8may_30s.jpg
Comet 2019 Y4 on 8-May. 40x 30-sec with Mx716 on C8 at f/3.5.
c2019y4_8may_30s.jpg (44.07 KiB) Viewed 5350 times

But by 10:40 it was dark enough to increase the exposures to 60-sec:
c2019y4_8may_60s.jpg
Comet 2019 Y4 on 8-May. 26x 60-sec with Mx716 on C8 at f/3.5.
c2019y4_8may_60s.jpg (50.25 KiB) Viewed 5350 times

By the time I packed up at 11:15 this comet was still 27 degrees above the horizon, whereas SWAN will only be around 15 degrees at 11pm on the 28th - but it should be much brighter...

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rwilkinson
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Posts: 1423
Joined: Mon Oct 12, 2009 7:47 pm
Location: Bolton

Re: Imaging comets in the twilight

Post by rwilkinson » Mon Jun 01, 2020 1:32 pm

As it turned out, by the end of May Comet SWAN was fragmenting and so had faded considerably, as shown in this image from 28th May:
https://fg-kometen.vdsastro.de/pix/2020 ... 052020.htm

It took me four attempts to find a location for my tripod where I could aim low enough to reach the comet's position - I ended up on the patio, hard against the fence. Even from this position I had just a few minutes around 11pm before the comet disappeared behind the trees.
swanset.jpg
Stack of 32x 10 & 15-sec images aiming low in the NNE.
swanset.jpg (31.08 KiB) Viewed 3414 times
(The "bright" star near the middle of this image is HD32296 , which is only magnitude 6.5!)

As well as the twilight (with the Sun only 9 degrees below the horizon), I was also aiming directly over my neighbours' brightly-lit conservatory, so I had little hope of detecting the faint comet. However careful examination of my image shows a definite smear in the expected position:
c2020f8_31may.jpg
20x 10 & 15-sec images with Hx916 on TS70ED at f/4.1.
c2020f8_31may.jpg (201.49 KiB) Viewed 3414 times

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