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  #1  
Old 07-12-2018, 04:00 PM
assbutt94
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Orion Nebula Defect

Hi, I've recently "Completed" my astrophotography setup, finally getting a guide-scope and whatnot. Any way, I figured I'd start on something easy and interesting and try get some good capture time of the Orion Nebula.

Anyway, I've come to find that the star Hatysa located within the boundaries of the nebulousness is causing a lopsided Halo defect that I'm not sure how to handle.

Pointing closer to Hatysa causes the halo to shrink but causes the nebula to be framed less than ideally, where nebulousness is now also being effected by vignetting.

Here is a single example of 40 or so stacked 3min subs, darks + flats. I cropped a lot of my vignetting but haven't done any editing.

Click image for larger version

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Im using a Celestron 8se OTA, 0.63x focal reducer, Astronomik CLS CCD filter followed by the celestron CRing thingo to mount my DSLR.
Im thinking maybe the Light pollution filter is bouncing light back to my focal reducer but that's a stab in the dark (get it hahaha).

Happy for any input and critique. Hoping to collect some more data tonight to add to this, perhaps more 3 min exposures at ISO 1600 (same as this) to get more subs and later on ill take some with lower ISOs to better show detail in the centre and then have a crack at aligning it with photoslop

Cheers!

EDIT: Cant get the image to display for some reason. Always have this problem...
EDIT2: Got it

Last edited by assbutt94; 07-12-2018 at 04:57 PM.
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  #2  
Old 07-12-2018, 04:35 PM
Gavin1234
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So it appears on the same star, even when it’s framed differently I.e. it’s not moisture on part of your imaging train?

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  #3  
Old 07-12-2018, 04:54 PM
assbutt94
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Quote:
Originally Posted by Gavin1234 View Post
So it appears on the same star, even when it’s framed differently I.e. it’s not moisture on part of your imaging train?

To attach an image to these posts they have to be under 500mb
Yes, I've had it happen to other stars before, Even when I wasn't using a focal reducer and they would be out of frame, the halo would encroach in. I dont think it's moisture as I dont think it's getting cold enough for any to form and I havent seen any evidence of moisture drying on glass.
I no longer suspect it's light bouncing forward from my LPF as thinking back, it's happened without the FR.

Also worked out adding photos
Click image for larger version

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  #4  
Old 07-12-2018, 04:59 PM
Paulyman (Paul)
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That’s a reflection of the star, I get exactly that shaped reflection on my Evolution 6 when close to a bright star such as Alnitak. Can’t help with how to deal with it in processing unfortunately as I’m still starting out on that as well. But I’m sure someone will be along to help with that. Good luck, image looks good despite the reflection.
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  #5  
Old 07-12-2018, 05:08 PM
Startrek (Martin)
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If your in suburban Sydney ( bortle 7 to 8 sky ) and using a DSLR ( which I do Canon 600D) I find capturing lots of short exposures without the filter gives you a better outcome when stacking and post processing
Try 40 to 60 subs @ 25 to 40 sec with ISO 800, you still capture enough data
Iíve tried 5 minute, 3 minute , 2 minute and 1 minute subs at ISO 400 / 800 and the end result is to much noise and a massive blown out core which you canít clean up
Your DSLR sensor temperature with long subs is probably around 39 to 45 degrees but at short subs with pause and delay it should be sitting around 32 to 35 degrees, this does help
With shorter subs you can try layering in your post processing as well ( Iím still learning this feature )
Hopefully tonight Iím going for 60 x 30 sec subs and 15 darks at ISO800
Good luck !
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  #6  
Old 07-12-2018, 05:43 PM
assbutt94
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Quote:
Originally Posted by Startrek View Post
If your in suburban Sydney ( bortle 7 to 8 sky ) and using a DSLR ( which I do Canon 600D) I find capturing lots of short exposures without the filter gives you a better outcome when stacking and post processing
Try 40 to 60 subs @ 25 to 40 sec with ISO 800, you still capture enough data
I’ve tried 5 minute, 3 minute , 2 minute and 1 minute subs at ISO 400 / 800 and the end result is to much noise and a massive blown out core which you can’t clean up
Your DSLR sensor temperature with long subs is probably around 39 to 45 degrees but at short subs with pause and delay it should be sitting around 32 to 35 degrees, this does help
With shorter subs you can try layering in your post processing as well ( I’m still learning this feature )
Hopefully tonight I’m going for 60 x 30 sec subs and 15 darks at ISO800
Good luck !
I used to take subs in the exposure lengths you've suggested as i bought the equipment i needed slowly and was unguided for a long time. My camera's ISO provides a similar SNR as a 600D at ISO800 (going by DXOmark anyway).
I haven't edited a 3min exposure yet, but just opening the stack in photoshop seems like it will need less editing to have more detail than any of my short exposure stacks. Granted my first attempt at editing was those short exposures of Orion, so maybe I could do that data a bit more justice.
Hopefully I may even be able to use them to layer onto the longer subs like you've suggested.

I thought that the heat would be the same at the end of varying length exposures, as the camera uses the exact same method to count and process the information the sensor collects.
I'll slap a temperature probe from a cheap set of multi-meters on the camera tonight because now I'm curious and I need help not falling asleep.
I have a 25s pause between exposures, and I keep the screen off so that is doesn't generate heat.

Im also in Sydney, the sky's look good tonight, Good luck!

Quote:
Originally Posted by Paulyman View Post
That’s a reflection of the star, I get exactly that shaped reflection on my Evolution 6 when close to a bright star such as Alnitak. Can’t help with how to deal with it in processing unfortunately as I’m still starting out on that as well. But I’m sure someone will be along to help with that. Good luck, image looks good despite the reflection.
Thanks!
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