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M15 new try

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#1 bignerdguy

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Posted 10 August 2020 - 03:45 PM

Ok, so i am finding doing clusters to be a challenge as every time i take shots the centers are ALWAYS over exposed.  I tried to get around this by doing 20 second subs but that still was too much.  Next time i will try around 5 seconds and see what happens.  This shot is a combination of around 125x - 20 second exposures aligned, stacked, and dark/flat/bias adjusted in MaximDL. Processing was done mostly in MaximDL this time as i am still learning how the processing features work and only had to make a few minor exposure corrections in Photoshop to reduce some of the noise from the black background.

 

M15.jpg



#2 ELDavis

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Posted 10 August 2020 - 03:58 PM

I had a similar problem when converting from 32 bit to 16 bit in Photoshop. Now I export from DSS in 16 bit before importing to Photoshop.


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#3 F.Meiresonne

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Posted 10 August 2020 - 04:04 PM

My limited experience learned me however they don't need long subs..to get a descent image.

 

and not even many subs ...

 

What kind of scope did you use?



#4 bignerdguy

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Posted 10 August 2020 - 06:45 PM

My limited experience learned me however they don't need long subs..to get a descent image.

 

and not even many subs ...

 

What kind of scope did you use?

I used the Meade 8" mentioned in my signature.



#5 bignerdguy

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Posted 10 August 2020 - 06:46 PM

I had a similar problem when converting from 32 bit to 16 bit in Photoshop. Now I export from DSS in 16 bit before importing to Photoshop.

These get taken directly in 16-bit.  the camera doesn't do 32 bit images. in fact i think its a stretched 14-bit (canon 60D) but i could be wrong about that.



#6 ELDavis

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Posted 10 August 2020 - 07:10 PM

D you use DSS? The autosave in DSS is 32 bit.



#7 Michael Harris

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Posted 11 August 2020 - 07:28 PM

I have learned that this problem is called “high dynamic range”, the classic example being the Andromeda Galaxy. Exposures that bring out faint details in the periphery of the galaxy are overwhelmed by the bright central core. There are processing tricks to overcome this but I have not mastered them yet. I took a bunch of globular cluster images the other night so I guess I am goong to find out! Overall this is a nice image. i really like globular clusters, they are fascinating.



#8 bignerdguy

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Posted 11 August 2020 - 08:18 PM

I have learned that this problem is called “high dynamic range”, the classic example being the Andromeda Galaxy. Exposures that bring out faint details in the periphery of the galaxy are overwhelmed by the bright central core. There are processing tricks to overcome this but I have not mastered them yet. I took a bunch of globular cluster images the other night so I guess I am goong to find out! Overall this is a nice image. i really like globular clusters, they are fascinating.

Yeah for that what you do is take two sets of photos.  one at the longer time frame and one at a shorter one, then using HDR methods combine them to make a single frame with both high and low light levels combined so you can see the core while also seeing the fainter outer edges with no blurring or over exposure.  there are software packages that can automate this but so far i havent learned how to do that anywhere except photoshop and that takes doing.  Still working on it though.



#9 ELDavis

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Posted 12 August 2020 - 10:47 AM

I am finding it hard to believe that a 20 second exposure would be this overexposed at F10, 0r even at F 6,3

(if you are using a focal reducer.)

I have enclosed two  images taken from a stack of 120 second exposures at F 5.4.

The first one I converted the DSS autosave 32 bit image in PS to 16 bit. The second image I exporter from DSS in 16 bit format before importing into PS. World of difference. I have to believe your problems are from processing rather than overexposure

M13 -2.jpg M13.jpg

 

 

 



#10 bignerdguy

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Posted 14 August 2020 - 01:13 PM

Yeah partly it is processing and partly because i was apparently using the wrong filter which was allowing WAY too much IR light to pass. I am using a filter wheel and i just discovered last night that Slots 1 and 4 were reversed, that is, i had a V-Fringe filter in slot 1 and i was talking photos with this which causes the light pollution and IR glow to swamp the sensor badly enough to make my flats and lights almost useless.  I plan to correct this with new photos tonight of M16 using the LPR filter this time.  I swapped the two back to where i thought they were supposed to be in the first place. It was a #smackshead kind of moment... DOH!


Edited by bignerdguy, 14 August 2020 - 01:14 PM.



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