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Old 17-04-2024, 09:41 PM
Geochron (Jon)
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GUM12 region wide field

Hi folks,

Here is my current progress on a wide field image of the GUM12 nebula region, including the Vela supernova remnant and the tiny (on this scale) pencil nebula NGC2736 down at the bottom right. The area shown represents approx 9 x 6 degrees.

This is 22hrs (Ha 6, O 10, S 6) shown in HSO palette which I find easier to process than SHO, and probably more pleasing to the eye? Just over half of the exposures were from a dark sky site, the rest from Melbourne.

Samyang 135mm lens, ASI 2600MM, Antlia 3nm filters. Stacked and combined in APP with star reduction and Selective colour adjustments in Photoshop on separated star/starless layers followed by Noise Exterminator.

The stars look a little dodgy towards the margins but this seems like an unavoidable trade-off when using camera lenses which were likely originally never intended for astrophotography.

https://www.iceinspace.com.au/forum/...1&d=1713353602

full sized image here:
https://www.dropbox.com/scl/fi/hnq9r...4yyyxveya&dl=0

thanks for looking

cheers, Jon
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Old 18-04-2024, 07:43 AM
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Ryderscope (Rodney)
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Excellent. A fascinating area to explore and to work with different compositions and colour pallets. Thanks for sharing
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Old 18-04-2024, 10:00 AM
Dave882 (David)
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Great image! Itís amazing how huge this region is and so much to take in
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Old 18-04-2024, 11:53 AM
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strongmanmike (Michael)
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I agree with Rodney, a veritable Mr Squiggle area this one, with many possibilities in terms of presentation, framing and colour palette.

Nice job

Mike
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Old 18-04-2024, 03:17 PM
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Retrograde (Pete)
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Very nice image of this faint region, Jon!

Quote:
Originally Posted by Geochron View Post
The stars look a little dodgy towards the margins but this seems like an unavoidable trade-off when using camera lenses which were likely originally never intended for astrophotography.
I wonder whether you need some extra backfocus given the filter in the optical path (usually 1/3 of the filter difference), especially if you are running the lens at a pretty fast f-ratio? Perhaps you've already allowed for this, but I remember my first test image with the Samyang 135, filter & astrocamera had pretty bad stars around the edge.
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Old 18-04-2024, 08:37 PM
Geochron (Jon)
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I can certainly try that Pete but I always seem to have problems mostly at the top left corner rather than across the frame. I am also rather suspicious of the ZWO camera lens adapter which seems have a bit of remnant wobble ie the lens is not an entirely firm fit. Maybe I have a dud unit there?

cheers, Jon
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Old 18-04-2024, 09:16 PM
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Retrograde (Pete)
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Quote:
Originally Posted by Geochron View Post
I can certainly try that Pete but I always seem to have problems mostly at the top left corner rather than across the frame. I am also rather suspicious of the ZWO camera lens adapter which seems have a bit of remnant wobble ie the lens is not an entirely firm fit. Maybe I have a dud unit there?

cheers, Jon
If it's just one part of the image it could well just be tilt. I run my Samyang at f2.8 & at that f-ratio everything needs to be just so much more stringent. What might work fine at f6 can be terrible at f2.8 & I don't think those lens adapters are the finest examples of mechanical precision (I use one too). You can try shims made from foil etc or buy commercial ones.
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