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AR 2770 and AR2771 0n 8/13/2020

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#1 PhotonJohn

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Posted 14 August 2020 - 01:30 AM

AR 2770 and 2771 with companion.  Captured with a Lunt LS 60mm hydrogen alpha scope in single stack mode, 3X barlow and ZWO ASI 174mm camera. Images are rotated and inverted.  Not very impressive size wise but good to practice on. Tried a different capture method today. In SharpCap I set my gain at  zero and raised the exposure till the histogram was at 80 percent. What effect would this have on my capture?  Is it ok to do this?  It seemed to work ok.  Still struggling to get an even blending near the limb. Could also bring out the proms a little.  I use ImPPG for smoothing. All suggestions welcome. Click for full size, it's a much better image. 

 

AR 2770

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  • S81320aipcjpg.jpg

Edited by PhotonJohn, 14 August 2020 - 02:22 AM.

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#2 PhotonJohn

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Posted 14 August 2020 - 01:31 AM

S81320aipcjpg (2).jpg

 

 


Edited by PhotonJohn, 14 August 2020 - 01:59 AM.

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#3 PhotonJohn

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Posted 14 August 2020 - 01:33 AM

AR 2771

 

S813202aipc (2)jpg.jpg

 

 

 

 


Edited by PhotonJohn, 14 August 2020 - 02:03 AM.

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#4 PhotonJohn

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Posted 14 August 2020 - 01:35 AM

S813202aipc (3)jpg.jpg

 

 


Edited by PhotonJohn, 14 August 2020 - 02:05 AM.

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#5 rigel123

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Posted 14 August 2020 - 06:31 AM

Nice ones John!


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#6 bigdob24

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Posted 14 August 2020 - 06:32 AM

Nice images 


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#7 MalVeauX

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Posted 14 August 2020 - 06:52 AM

Nice capture John!

 

Setting your gain to zero and just raising exposure (via exposure time) will result in you allowing a long exposure time, this is ok  to a point, but after about 10ms or so, you start to have a long enough exposure time to capture the motion blur of the seeing as literal blur in your image, you can push it if seeing is very steady, to 12ms, 16ms, etc, if seeing is super, super steady. This is rare though. And longer than that you will get a blurry capture due to recording the movement blur of seeing in your image. There's no benefit to not using gain at this scale, once you stack a handful of frames, the signal to noise ramps up and the noise itself is reduced heavily.

 

Very best,


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#8 hopskipson

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Posted 14 August 2020 - 12:25 PM

Nice capture John!

Setting your gain to zero and just raising exposure (via exposure time) will result in you allowing a long exposure time, this is ok to a point, but after about 10ms or so, you start to have a long enough exposure time to capture the motion blur of the seeing as literal blur in your image, you can push it if seeing is very steady, to 12ms, 16ms, etc, if seeing is super, super steady. This is rare though. And longer than that you will get a blurry capture due to recording the movement blur of seeing in your image. There's no benefit to not using gain at this scale, once you stack a handful of frames, the signal to noise ramps up and the noise itself is reduced heavily.

Very best,


How much gain would be too much? Sometimes I worry when I start approaching 200+ gain.
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#9 PhotonJohn

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Posted 14 August 2020 - 03:13 PM

How much gain would be too much? Sometimes I worry when I start approaching 200+ gain.

The way I figure too much gain in SharpCap is when the capture histogram shows clipping. My captures are usually set between 80 or 90% on the histogram. Don't know if this is too much. Maybe Marty will tell us.



#10 hopskipson

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Posted 14 August 2020 - 03:24 PM

The way I figure too much gain in SharpCap is when the capture histogram shows clipping. My captures are usually set between 80 or 90% on the histogram. Don't know if this is too much. Maybe Marty will tell us.

Yes John that would be too much gain!  My question goes more to when I'm double stacking with a barlow and I have the exposure set at 10ms, to get an acceptable histogram fill of 80-90% I have to raise the gain to 200+ in Firecapture.  I have a feeling that too much gain will introduce too much noise or perhaps cause other problems like decreasing the dynamic range.


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#11 PhotonJohn

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Posted 14 August 2020 - 03:43 PM

Yes John that would be too much gain!  My question goes more to when I'm double stacking with a barlow and I have the exposure set at 10ms, to get an acceptable histogram fill of 80-90% I have to raise the gain to 200+ in Firecapture.  I have a feeling that too much gain will introduce too much noise or perhaps cause other problems like decreasing the dynamic range.

When I use SharpCap and shoot at 10ms my gain is set around 200. I also use a 3X barlow and double stack. At this point in my learning curve everything is experimental.


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