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Feedback requested - HyperStar C8 Markarian's Chain

Astrophotography
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#1 ts298

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Posted 14 May 2021 - 04:10 PM

I'm green, with under 20 images under my belt. So I'm drinking from the fire hydrant, so to speak. But I'm wondering what can make the biggest improvements in my imaging... including changes I may not even realize I should be making.

 

I imaged Markarian's Chain last night from my Bortle 7/8 sky in New Jersey. I'm imaging from my driveway, with bright house and street lights about 50 feet away. In all of my images, I get wild gradients. APP does an amazing, but not nearly perfect job of removing them, as you can see in the right half of my image.

 

While I know that the sky glow from being between NYC and Philly probably has the most effect on the gradients, I'm wondering if you advise relocating to my back yard, where the glare of the neighborhood lights is significantly blocked; or if I should pack up and drive 5 minutes to a public space where there are no lights; or if my HyperStar is simply going to soak up all the ambient light no matter what? Perhaps a slower refractor would be the better way to go? Or maybe I should reduce my exposure time on the HyperStar? I use 30s for essentially every target now. When I was doing 60s I was blowing out stars, so I moved to 30s to recover star colors. But now I'm wondering if I should go even shorter.

 

Brighter stars look bloated... not sure whether I should blame my exposure time, the optical limits of the HyperStar (not that I've reached them) or the very, very fine touch needed to focus with the HyperStar. Again, another issue that makes me wonder if I should just go to a slower refractor that's easier to focus and harder to blow out stars with.

 

I'm aware that my OSC camera is suboptimal in my polluted skies, but time on clear nights is very hard to come by for me. That's how I ended up with this "lazy man's" setup and philosophy.

 

I processed in APP. I did a very rough post-processing in APP as well because I have no PhotoShop knowledge. So much to learn...

 

IMAGE: https://imgur.com/a/aQnWmVI

 

Scope: C8

Reducer: HyperStar (f1.9, 388 mm)

Camera: ASI294 MC Pro

Filter: Optolong L-Pro

Mount: AVX

Guiding: No

Acquisition software: ASI Air Pro

Lights: 30s x 120 (1 hour total)

Darks: 20

Flats: 10 (0.0015 seconds)

Dark Flats: 20

Bias: 100 (0.001 seconds)

Processing and post-processing: APP for OS X


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#2 06AwzIyI

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Posted 14 May 2021 - 04:33 PM

Right off the bat, I would try imaging with zero gain (assuming you're currently using unity) and run the optimal exposure calculator in SharpCap against your sky (you ARE using SharpCap aren't you? grin.gif ) and see where that gets you. At f/1.9 and unity gain, optimal exposure time is going to be way too short to deal with. The alternative is to use zero gain, take advantage of the full well capacity, and more manageable exposure time.


Edited by 06AwzIyI, 14 May 2021 - 04:35 PM.


#3 hornjs

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Posted 14 May 2021 - 04:52 PM

For the 294mc pro, I would avoid bias frames at all costs.  Plenty of threads on here about the camera issues with exposures that short.  

Eliminate bias frames

Up you exposures on the Flat frames to > 3 seconds.  

I think you will see an improvement with that already.


Edited by hornjs, 14 May 2021 - 05:00 PM.


#4 bobzeq25

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Posted 14 May 2021 - 05:31 PM

Faster optics are better in light pollution.  I bought a C8 RASA specifically for my Bortle 7 skies.

 

I use 10 second lights.  Below is a sample.  650X10".  Gain zero.

 

The LPro is hurting you.  Using no filter is better.  None was used below.

 

Imagur won't let me see your whole image.  The small sliver I could see was not bad.

 

Pleadies 2019 V3_smaller.jpg

 

 



#5 audioengr

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Posted 14 May 2021 - 06:55 PM

I agree, don't use this filter with the Hyperstar. Only from the rear-cell.  However, you should be using an IR/UV cut filter inside the Hyperstar with your camera.  I use the Baader cut filter.

 

I think a long Astrozap dew shield may help keep some light from bouncing around in the OTA.  I always use one with my 8" OTA.

 

Use the smart histogram in SharpCap Pro to determine your optimum exposure time to prevent overexposure.  I have the ASI294MC camera and I always set it for gain of 121 for captures.  This is a good place to start based on the noise graph.

 

I also use APP, including the gradient removal, star color tool and even the stretch, sharpening, saturation and contrast.  The gradient tool requires a lot of practice, but it is quite good.  Sometimes I use it twice on the same image.  The APP stretch is also a good starting point.  Look at both the linear and log histograms to determine how much linear stretch is optimum for the Tiff file.  You should have a little gap to the left of the hump so you can do curves later.  I use either PI or PS to do the final processing, including curves, saturation, levels, noise removal etc..  I highly recommend PS and the Astronomy Tools action set that works inside it.


Edited by audioengr, 15 May 2021 - 10:37 AM.


#6 ts298

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Posted 14 May 2021 - 10:09 PM

The teaching here is very valuable... thank you all... and thanks in advance to those who may have more to add later.
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#7 sctbrd

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Posted 14 May 2021 - 11:52 PM

+1 for using no filter, at least as a beginner. It cuts ALOT of light. See what you can get without it. If I have issues, I usually start from the easiest settings/setup, and move on from there. Once you get some results you can graduate to the filter.

 

I havent used my L-enhance filter yet on my hyperstar, but it is a different animal than normal frames with a DSLR... useful info:

 

https://forums.sharp...opic.php?t=3254

 

Try a dew shield to reduce glare- get some flat black semirigid plastic and wrap it around the end of your scope and see what it does.

Or find a shadier place.


Edited by sctbrd, 14 May 2021 - 11:58 PM.


#8 bobzeq25

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Posted 15 May 2021 - 12:13 AM

+1 for using no filter, at least as a beginner. It cuts ALOT of light. See what you can get without it. If I have issues, I usually start from the easiest settings/setup, and move on from there. Once you get some results you can graduate to the filter.

 

I havent used my L-enhance filter yet on my hyperstar, but it is a different animal than normal frames with a DSLR... useful info:

 

https://forums.sharp...opic.php?t=3254

 

Try a dew shield to reduce glare- get some flat black semirigid plastic and wrap it around the end of your scope and see what it does.

Or find a shadier place.

The LEnhance will work well with Hyperstar.  On emission nebulae, _only_.

 

Using an LP filter on everything is not good.  But they do have their place.  It's not on galaxies or reflection nebula, but on emission nebulae.

 

The Jellyfish with my C8 RASA, and an NBX filter (a close relative of the LEnhance, but optimized for fast systems.)

 

https://www.sciencec...filters/nbx.htm

 

Jellyfish, SH2-249 -small.jpg


Edited by bobzeq25, 15 May 2021 - 12:19 AM.



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