Lookin' for guidance

Astrophotography: share your photos & discuss techniques
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Pete
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Joined: Fri Jun 13, 2003 9:03 pm

Lookin' for guidance

Unread post by Pete »

M42 season is once again upon us. This wonderous object is difficult to image due to its brilliant center, which will usually "burn out" the Triangulum area. One solution is to combine short exposure frames with long exposure frames. Anyone know how to do this?

Do I simply take an hour's worth of long exposure and 15 minutes of short exposures, and then what? Does one process them as two groups and then combine the results of the 2 groups? Or does one stack all raw frames together? Or is it necessary to combine using PhotoShop? I've never mastered PhotoShop layers and am hoping to avoid that approach.
Pete P.
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AstroGeek
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Re: Lookin' for guidance

Unread post by AstroGeek »

Pete,

You need a long exposure to capture the full globe of nebulosity. This will burn out the core, and details cannot be recovered.

This is a series of 3-minute exposures:
ORION LONG.jpg
ORION LONG.jpg (7.64 MiB) Viewed 594 times

And you need some much shorter exposures, being cautious NOT to over-expose the centre.

This is a stack of 30-second exposures:
ORION SHORT.jpg
ORION SHORT.jpg (1.96 MiB) Viewed 594 times
Then the two are blended together via Photoshop. Any version will do and it's not very complicated.
Collect the best two images you can with multiple exposures of long and short duration.
Either you can watch an example of the procedure on YouTube here:

https://www.youtube.com/watch?v=tMbcgsTIV1g

OR I can show you how it's done during a meet-up with adult beverages.

From the pics shown above, I was able to process them into this result:
Orion Nebula Wide-Field IMPROVED copy 2.jpg
Orion Nebula Wide-Field IMPROVED copy 2.jpg (1.97 MiB) Viewed 594 times
Steve L
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Pete
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Re: Lookin' for guidance

Unread post by Pete »

Darn. I've struggled with Layers for 20 years and still haven't figured them out. Hoped to avoid them.
Pete P.
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menardre
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Re: Lookin' for guidance

Unread post by menardre »

I believe that you are supposed to develop 2 masters..one short exposure and one long. Then combine them.

I find it easier to mask the bright area around trapezium and work on it separate from the remaining nebula.

Here is an image of M42 that I just reprocessed in Pixinsight using a few newer Pixinsight tools. This was 137 two minute exposures using a ZWO ASI071 on 5 inch refractor.

Roger
M42_Orion Nebula-1.jpg
M42_Orion Nebula-1.jpg (6.46 MiB) Viewed 585 times
Roger M.
Celestron CPC1100 EDGE, Stellarvue 130T refractor dual mounted on iOptron CEM120 on permanent pier mounted in Observatory. Imaging camera ZWO ASI2600 OSC, guide camera Lodestar or ZWO ASI290MM.
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Pete
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Re: Lookin' for guidance

Unread post by Pete »

Nice Roger. Wish I could take such long exposures. As for bright galaxy cores, currently I just lasso the core in PS and process it separately.
Pete P.
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