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Old 20-01-2022, 08:51 PM
Stephane
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Thor's Helmet

Hi all,

My coma issues are finally fixed I think. Do I still need a millimeter do you think? I am overall pleased with this image taken on the full moon in narrowband. Obviously more integration time would be great though…

Two editions. Lighter and darker background. I prefer the lighter, although some strange gradients start to appear. Please provide some feedback so that I can continue learning.

Many thanks,
Stéphane

Camera: ZWO ASI294mc
Filter: Optolong L-Extreme
Integration: 3h10’
Calibration: 50D, 30F, 50DF
Processed in Pixinsight, Gimp, Adobe Lightroom
Attached Thumbnails
Click for full-size image (IMG_7890.jpg)
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Click for full-size image (IMG_7891.jpg)
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Last edited by Stephane; 20-01-2022 at 09:48 PM.
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Old 20-01-2022, 08:57 PM
AdamJL
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Very good
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Old 20-01-2022, 09:25 PM
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ChrisV (Chris)
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That's really nice!
I'd be extremely happy with that. Done a great job sorting out the coma too
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Old 20-01-2022, 10:04 PM
Startrek (Martin)
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Stephane,
Great effort on such a difficult dim target plus a moon lit sky
Well done indeed !!
Maybe check your focus through the capture , looks a tad out on some of the bigger stars
Cheers
Martin
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Old 21-01-2022, 07:19 AM
RyanJones
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Very nice capture Stephane. You’ve got your coma pretty well sorted so well done. There is what appears to be marginal over correction on the left side but I can’t pick it on the right so if this isn’t cropped at all it will be a slightly off center optical axis. That’s only if you want to get really picky though.

The gradients you got are probably because of the moon being so full so that’s an easy one to avoid.

Also just be careful labeling an image taken on a OSC camera with a dual band filter as ‘ narrowband ‘. You might upset some of the purists lol

All together a great job Stephane. Well done 👍
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Old 21-01-2022, 08:34 AM
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Nice capture Stephane . Good to see someone has clear skies. I will need to buy a volcanic ash filter i think the sky is rubbish here at the moment.
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Old 21-01-2022, 12:14 PM
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Nice work Stephane
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Old 21-01-2022, 01:10 PM
Stephane
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Thanks all for the kind words.

Martin, I find achieving perfect focus challenging. I remember your diffraction spike tip, but still finding it difficult. I will continue practicing and will aim to get the lowest HFR possible.

Ryan, I also noticed the slight overcorrection in the top left corner. This image was cropped, but I didn’t notice anything in the uncropped version. I will keep an eye on it. If it does need a mm or two shaved off, I could remove the thin ring on the coma corrector. Also, thanks for the dual band terminology correction.

Thanks again for the tips. Please don’t hesitate to go hard on me. It’s the only way to improve.

Clear skies,
Stéphane
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Old 21-01-2022, 02:32 PM
RyanJones
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I have an 8 inch bahtinov mask that I no longer use to help with your focusing if you like Stephane. Remember your OTA will change length every few degrees of ambient so you need to keep refocusing throughout your session unless the temperature stays stable.
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Old 21-01-2022, 04:03 PM
Startrek (Martin)
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Quote:
Originally Posted by Stephane View Post
Thanks all for the kind words.

Martin, I find achieving perfect focus challenging. I remember your diffraction spike tip, but still finding it difficult. I will continue practicing and will aim to get the lowest HFR possible.

Ryan, I also noticed the slight overcorrection in the top left corner. This image was cropped, but I didn’t notice anything in the uncropped version. I will keep an eye on it. If it does need a mm or two shaved off, I could remove the thin ring on the coma corrector. Also, thanks for the dual band terminology correction.

Thanks again for the tips. Please don’t hesitate to go hard on me. It’s the only way to improve.

Clear skies,
Stéphane
Stephane,
There’s a load of different ways to focus which all do the job
I use a ZWOEAF focuser with remote handcontroller ( I use a 5m long TRRS 4 conductor cable to allow my ZWOEAF HC to sit on my workstation desk next to the laptop both outdoors in Sydney and in my NexDome down South. Then use APT to capture 15 sec subs on my focus Star near your intended target. APT has a zoomed in thumbnail to view your focus star. You need a program that can zoom in at 5x or 10x , that way you can see the diffraction spikes and Star core get tighter and tighter until your happy. I used this method the same way in my DSLR days with BYEOS.Once your focused and framed you can check your subs throughout the night session by checking the zoomed in Thumbnails on any star in the field of view.Initial focusing takes me about 5 to 10 mins.
Antiquated, yes but it works for me and I rarely have an out of focus image to be honest
Cheers
Martin
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Old 21-01-2022, 05:17 PM
Stephane
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Martin, thanks for the suggestions. I'm glad it takes you a good 5-10 minutes, because it usually takes me a good 10 minutes. Tonight, I will focus on a nearby bright star, and then re-focus some time later once temperature has dropped a few degrees. Hopefully that will improve focus.

Ryan, I was thinking of getting one 3D printed by a friend, but I would rather get the real thing! Feel free to private message me with details (price, pickup suburb,...). Thanks.
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