Comet 21P/Giacobini-Zinner - 2018-09-06 - Time Lapse

[PhotoGav]

I set the alarm for 2am this morning and was delighted to see that the forecast was right and the sky was perfectly clear. So I collected a colleague and together we headed up to the Marlborough College Blackett Observatory to hunt down Comet 21P/Giacobini-Zinner with the 158 year old Thomas Cooke 10" refractor housed there. The scope has a GoTo system fitted to its big old mount (making it the oldest computerised telescope... in the world!!!) and it certainly did its stuff perfectly. I entered the comet's coordinates from Sky Safari and it slewed straight to it, brilliant - I can assure you that doesn't always happen so easily with that scope! I proceeded to shoot a series of photos of the comet - two runs of 45 frames each. Exposure was 16 seconds at ISO 6400 with my Canon EOS 1Dx. I refocussed between runs, hence the jump in the video.

Here is the time lapse of Comet 21P passing through Auriga on 2018-09-06 between UT 02:11:00 and 03:14:00 at a speed of around 22 km/s across our line of sight.

 

 

 

[Davey-T]

Superb animation Gav, well done.

How much of the full frame of the camera does the scope cover ?

Dave

[Galen Gilmore]

Very nice time-lapse! I was thinking about imaging 21P on Friday, any tips for imaging it?

[PhotoGav]

35 minutes ago, Davey-T said:

Superb animation Gav, well done.

How much of the full frame of the camera does the scope cover ?

Dave

Thanks Dave. There is very slight vignetting in the corners, so it appears to cover the full frame of the 1Dx. The biggest problem was drift in the mount over the hour or so of imaging. There is no guiding of any sort and I wasn't going to start trying to manual guide the beast! As a consequence I have cropped into the area of image that is shared across all frames, which thankfully is plenty big enough to make it work.

36 minutes ago, Galen Gilmore said:

Very nice time-lapse! I was thinking about imaging 21P on Friday, any tips for imaging it?

Just give it a go and see what happens! I used a short exposure of 16 seconds, as much because of the mount inaccuracy as anything, with a high ISO of 6400 to get a bit of detail in the comet. I set the intervalometer to take 45 frames with a 20 second pause between shots, this was to allow time for the in camera Long Exposure Noise Reduction (i.e. Dark subtraction) to take place. I pressed start and then left it well alone! I went outside while it was clicking away to marvel at the beauty of such a clear night. Had the good fortune to see five meteors, including one fireball with a spectacular smoke trail! Good luck!

[Davey-T]

It's forecast to reach maximum of mag 7 on 8th / 13th this coming week so will hopefully have another go at it before it fades.

Talking of meteors it produces the Draconoinds in October, supposed to be bright and slow moving relatively.

Dave

[Galen Gilmore]

19 minutes ago, PhotoGav said:

Thanks Dave. There is very slight vignetting in the corners, so it appears to cover the full frame of the 1Dx. The biggest problem was drift in the mount over the hour or so of imaging. There is no guiding of any sort and I wasn't going to start trying to manual guide the beast! As a consequence I have cropped into the area of image that is shared across all frames, which thankfully is plenty big enough to make it work.

Just give it a go and see what happens! I used a short exposure of 16 seconds, as much because of the mount inaccuracy as anything, with a high ISO of 6400 to get a bit of detail in the comet. I set the intervalometer to take 45 frames with a 20 second pause between shots, this was to allow time for the in camera Long Exposure Noise Reduction (i.e. Dark subtraction) to take place. I pressed start and then left it well alone! I went outside while it was clicking away to marvel at the beauty of such a clear night. Had the good fortune to see five meteors, including one fireball with a spectacular smoke trail! Good luck!

How long of an exposure do you think could be achieved before the comet starts trailing? I want to be able to get as long of exposures as possible so I don't have to manually stack 50 frames.

[PhotoGav]

55 minutes ago, Davey-T said:

It's forecast to reach maximum of mag 7 on 8th / 13th this coming week so will hopefully have another go at it before it fades.

It’s heading down through Auriga past some lovely open clusters over the next week or so, which would make some good pics. If conditions allow, I might well have another go.

41 minutes ago, Galen Gilmore said:

How long of an exposure do you think could be achieved before the comet starts trailing? I want to be able to get as long of exposures as possible so I don't have to manually stack 50 frames.

Well, it’s travelling at about 4.4 arcmin per hour, so you can work it out for your image scale. As for manually stacking, that sounds unnecessary - what software are you using? I used Astro Pixel Processor to register all the frames.

[Galen Gilmore]

10 minutes ago, PhotoGav said:

It’s heading down through Auriga past some lovely open clusters over the next week or so, which would make some good pics. If conditions allow, I might well have another go.

Well, it’s travelling at about 4.4 arcmin per hour, so you can work it out for your image scale. As for manually stacking, that sounds unnecessary - what software are you using? I used Astro Pixel Processor to register all the frames.

I use DSS stacker normally, but that only stacks based on star alignment. I would have to do it in photoshop otherwise.

[PhotoGav]

9 minutes ago, Galen Gilmore said:

I use DSS stacker normally, but that only stacks based on star alignment. I would have to do it in photoshop otherwise.

Keep the total exposure short enough and star alignment will be good for the comet too. If you align on the comet with a very long total exposure time you will see star trailing. I’m sure there is a software package that will do that for you, but I can’t remember which one it is. I’ve never tried to do a long exposure of a comet, so am not the best person to advise you anyway! A separate post in the right place will get some good responses I’m sure. 

[happy-kat]

DSS will stack on comet too, there is a comet stacking function

[Davey-T]

1 hour ago, Galen Gilmore said:

I use DSS stacker normally, but that only stacks based on star alignment.

What HK said above.

Dave

[Galen Gilmore]

1 hour ago, happy-kat said:

DSS will stack on comet too, there is a comet stacking function

 

41 minutes ago, Davey-T said:

What HK said above.

Dave

Ah ok thanks, didn't know.

I will try it out.

[Ouroboros]

Brilliant video and marvellous information about the scope you use. 

Sounds like you got the better skies I had earlier in the night in north Cornwall.  

I had just finished some imaging in Cygnus with my SW ED80 when I turned my attention to the comet sometime after 2:00pm. I couldn't see it with bins so I decided to see if I could see it photographically. Below is a cropped 60 second ISO 1600 test shot.  Just as I decided it was worth taking a series of shots the skies clouded over. Duh!!!

 

[Special K]

Thanks for posting, it's brilliant!  I started observing quite late (after 4) with a mere 6" frac.   Visually it was not far off what we see here but the tail wasn't nearly as obvious as your time lapse.  Nice to see it tracking across the star fields!!!

[PhotoGav]

@Ouroboros thank you, I feel your pain - there is nothing more irritating than Astronomicus Interruptus courtesy of the Sky-Gods. You managed to grab a nice pic there though, well done!

Thank you @Special K - it is a good visual object too, so obviously a comet. It just makes me think of all those 19th century gentlefolk hunting for undiscovered comets. The excitement of finding a new fuzzy patch that does actually move relative to the stars must have been quite something!