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Xiga

21P/Giacobini-Zinner: 49 mins with a D5300 and 80ED

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Went out on Sunday night to try and get some OIII for the Veil Nebula Bi-Colour Mosaic I’m currently working on. It ended up being a largely frustrating night though as I was fighting a big, bright full moon (in hindsight not the smartest decision I’ve ever made in fairness, lol). Factor in just enough intermittent clouds to exacerbate the issue even more, and when it finally set behind the neighbour’s house at 03:30am I was feeling pretty glum and was about to pack up for the night when I suddenly thought, what the heck, let’s try for a quick capture of 21P!

As it was fairly low to the East, I had to disconnect all the cables and carry the whole rig to the other side of the house and re-do Polar Alignment, PHD calibration and focus. I did think about not guiding, as I knew the exposures were going to be short, but it just feels wrong not to guide these days so I decided to do it anyway just for peace of mind if nothing else. So I started capturing around 04:15ish and as astro-dark was due to finish shortly after 5am I decided to just do 40 subs of 90s each using the IDAS-D1 filter (we have streetlights nearby).

Went in to grab a quick 60 mins of shuteye, except I overslept and didn’t wake until 06:30, so was then in a mad rush to pack up and get ready for work! Which meant I forgot to get Flats, but thankfully I was able to re-use the master Flat from my M13 image from a few months back and it seemed to work just fine ?

Processing this one was interesting to say the least. This is my first comet, so I had to do some research beforehand. These days I always do my stacking in APP, but I had to go old-school and use DSS for this one due it’s special Comet-only stacking mode. So I did 2 stacks, a regular Median one just for the stars, and a 2nd Kappa-Sigma one aligned on the Comet (and using the same reference frame as the Median stack). Some subs were badly affected by intermittent clouds, so I could only stack 33 out of the 40 subs (and tbh 33 was really pushing it, quality-wise). I processed each one separately in PS and then layered in just the comet on top using the ‘Screen’ blending mode. I actually wasn’t aware there was red nebulosity in the background until I started stretching, and it certainly would have been easier to process had it not been there, lol. As expected, I have had to use quite a bit of NR compared to my normal amount, due to the pitiful amount of exposure to work with. Hopefully it doesn’t look too bad but let me know if you think it needs more or less of anything in particular. Of course, there’s only so far you can ever go with just 49 mins of data at hand.

As the capture was done in such a rush, I didn’t bother worrying about the framing. I just input the co-ordinates into SGP and let it centre on the object for me. But having now worked out where in the sky this is, and looking at the FoV, I can see that had I rotated the camera 90 degrees then the Cone Nebula would have been in the frame. I actually haven’t imaged the Cone before, so I think this winter I will make a point of imaging it in it’s own right, and then I can re-use it to make a much more interesting version of this image with a much better background. Fun times!

C&C welcome as always. And thanks for looking! ?

21P-GZ Combined v1.jpg

 

Edit: Decided to make a few changes, so here's v2:

1313345757_21P-GZCombinedv2.thumb.jpg.f0bbe74e9d1d5cacb65bf0605d4cd978.jpg

 

Edited by Xiga
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Excellent job, I really like this image, especially given the relatively limited data set. Great use of an otherwise frustrating night!

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Good catch Ciaran, it disappeared from view here for a while, must check to see if it's reappeared high enough to image.

Dave

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4 hours ago, PhotoGav said:

Excellent job, I really like this image, especially given the relatively limited data set. Great use of an otherwise frustrating night!

 

4 hours ago, Davey-T said:

Good catch Ciaran, it disappeared from view here for a while, must check to see if it's reappeared high enough to image.

Dave

Thanks Gav & Dave! ? 

Hmm, just looking at this again. Do you think the stars look too dull? I tried really hard not to over-stretch them, and I did do a bit of star reduction too, but I wonder if the image would have a bit more 'pop' if they stood out more?

I might have another play this evening ? 

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Great image! You can always add more data to the background later on. Tonight it's going to be close to the Rosette

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56 minutes ago, moise212 said:

Great image! You can always add more data to the background later on. Tonight it's going to be close to the Rosette

Thanks Alex!

Ooh it would have been good to get it in the same FoV of the Rosette. I did the Rosette last winter, a combination of the 2 would have been cool! But there's no way I'm staying up that late again to shoot it. One day of sleep deprivation was more than enough, lol.  

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5 hours ago, moise212 said:

You go to sleep now, you wake up at 3 :)

Oh if only it were so easy ?

Alas, with a little one at home there's little to no chance of me getting to bed before himself! Also, i do all my imaging from my parents house, which is a 30 min drive away, so adds yet more time to the whole procedure (especially on a week night). 

I'm quite happy to stay up to 3am shooting an object and go to work on a few hours sleep, but this one is just too late (or early!) for me, unless it falls on a weekend. So i'll just have to make do with what i've got i think ?

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So i decided to do a bit more processing on this (i've added it to the 1st post). 

I pushed the data a bit more (getting close to 'too much' territory now i think) with a further Arcsinh stretch. The stars have grown in size, but they've kept most of their colour so i don't mind so much. I boosted the saturation in the reds too, to bring out the nebulosity a bit more, i added a tad more NR and finally settled on a higher black point (the previous one was too low i think). Oh, and i did a bit more star reduction too, to hopefully let the comet stand out a bit more too.

What do you guys think. Better? Worse? I'm tending towards Better, but the eyes can play tricks at this time of night! ?

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The nebulosity adds to it so better I think, just hanging around here to see if it rises before the clouds arrive.

Dave

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Well it's 3.30am and I can't see a sign of 21P/GZ I've got it framed in the DSLR with the Rosette on the right so according to Stellarium it should be in the middle of the frame, must be washed out by the Moon, no nebulosity visible in the Rosette either and that usually shows up in a 30 second image.

Guess I'll try another night, did see a nice bright slow moving meteor overhead, wonder if anyone caught if on their all sky camera.

Dave

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8 minutes ago, Davey-T said:

Well it's 3.30am and I can't see a sign of 21P/GZ I've got it framed in the DSLR with the Rosette on the right so according to Stellarium it should be in the middle of the frame, must be washed out by the Moon, no nebulosity visible in the Rosette either and that usually shows up in a 30 second image.

Guess I'll try another night, did see a nice bright slow moving meteor overhead, wonder if anyone caught if on their all sky camera.

Dave

It should be visible. These are 60s subs.

image.thumb.png.10298107bde4fd859dab3713f4675c31.png

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4 hours ago, Davey-T said:

Well it's 3.30am and I can't see a sign of 21P/Z

I got up a couple of mornings ago Dave and couldn’t see anything with the Tak despite careful positioning with Sky Safari. I also blamed the moon but I also assume it’s faded a little now. 

Kerry 

Edited by kerrylewis

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Here's one 30sec' frame Canon 60Da WOZ61 with (I think)  Rosette cluster NGC2237 on the right compared to Stellarium it should be somewhere near the centre.

Dave

21PGZ-27-09-18.thumb.png.c40c8b804e710e00a920014c0f3476b0.png

21P-27-09-18-2.PNG.ac82fcaea0b7e99def1b4ed3e856cbcc.PNG

 

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2 hours ago, Davey-T said:

Here's one 30sec' frame Canon 60Da WOZ61 with (I think)  Rosette cluster NGC2237 on the right compared to Stellarium it should be somewhere near the centre.

Dave

21PGZ-27-09-18.thumb.png.c40c8b804e710e00a920014c0f3476b0.png

21P-27-09-18-2.PNG.ac82fcaea0b7e99def1b4ed3e856cbcc.PNG

 

That's strange alright. 

One possible suggestion is that Stellarium could be off from the comet's true position? When I did mine on Monday morning, I first got the co-ordinates from Stellarium and input them into SGP, but when I took a quick 30 sec exposure I couldn't see it with any certainty in the image. So I then went on to the website below and got up to the minute precise co-ordinates, which were different to Stellarium. When i tried centering on these new co-ordinates in SGP, the scope did do a pretty small slew, and when I took anther 30 sec exposure there was no doubt that there it was smack bang in the middle.

https://theskylive.com/21p-info

 

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27 minutes ago, Xiga said:

That's strange alright. 

One possible suggestion is that Stellarium could be off from the comet's true position? When I did mine on Monday morning, I first got the co-ordinates from Stellarium and input them into SGP, but when I took a quick 30 sec exposure I couldn't see it with any certainty in the image. So I then went on to the website below and got up to the minute precise co-ordinates, which were different to Stellarium. When i tried centering on these new co-ordinates in SGP, the scope did do a pretty small slew, and when I took anther 30 sec exposure there was no doubt that there it was smack bang in the middle.

https://theskylive.com/21p-info

 

I second this.

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It might be worth updating the solar system small body orbit data or similar in Sky Safari / Stellarium before looking for 21P. I found that it moved after a data update and I also found that I could find it in the telescope after the update!

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32 minutes ago, PhotoGav said:

It might be worth updating the solar system small body orbit data or similar in Sky Safari / Stellarium before looking for 21P. I found that it moved after a data update and I also found that I could find it in the telescope after the update!

You are right Gav - in my case I was perhaps relying to much on Sky Safari. However it has been spot on every other time that I have tried it hence my complacency? 

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1 hour ago, PhotoGav said:

It might be worth updating the solar system small body orbit data or similar in Sky Safari / Stellarium before looking for 21P. I found that it moved after a data update and I also found that I could find it in the telescope after the update!

Yes, Sky Safari and Stellarium have had a difference of opinion on comet positions before.

Dave

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