Gain and noise in solar imaging

Discuss solar related topics.
Post Reply
User avatar
Ben Cartwright SASS
Orion Spur Ambassador
Articles: 0
Offline
Posts: 654
Joined: Fri May 17, 2019 10:39 am
4
Location: SE New England
Status:
Offline

TSS Awards Badges

TSS Photo of the Day

Gain and noise in solar imaging

#1

Post by Ben Cartwright SASS »


I know that this has been discussed before but here goes again

up until now when I am imaging with my ASI174mm I keep the gain at 150 and then adjust gamma, 1-4 for surface and up to 100 for proms, normally on proms I run it about 95-100 but often do extra runs at 90 or whatever gives me a darker sky but doesn't lose much if any of the proms I set the speed to get the exposure I want, usually running 15 or 20 milliseconds and 50 or 60 fps for the surface and up to 50 milliseconds or higher and 25 or 30 fps for proms.
I usually shoot 500 frames for a prom and stack 25 or 50 of them (mostly 50 frames stacked), sometimes will go 1000 frames on a prom but not often. For the surface I shoot 1,000 or 2,000 frames once in a while more and again stack about 50 or sometimes 100 frames.
I seem to get good exposures and low noise.

On CN, yes CN and their gurus, they are saying you should set your milliseconds to no more than 10 ms and they often or usually use 4 milliseconds (MS) and then adjust the gain for the exposure they want and DON'T use gamma at all. Sharpcap 4 doesn't have gamma so you don't have a choice I use Sharpcap 3. They also are saying only do one exposure, that for the surface and try to pull the proms out in post processing.

First I have found that with two exposures one for the surface and one for the proms, I get better results on the proms.

The last two days I did a test, on Sunday I used 10 MS for everything and then on Monday I used 4 MS for everything. I had to run my gain up around 300 for the proms and in the low 200's for the surface.
I then compared the stacked images from Autostakkert of the proms against images I took with 150 or less gain. The results as I expected from my time as a professional photographer and current published Nature Photographer, is the higher the gain (or ISO on cameras) the MORE NOISE (grain).
The more noise the less detail!

It is an unscientific test, just comparing by eye, but to me shooting at 4 to 10 ms and high gain has more noise.

I seem to remember that John never shoots over 30 fps, what does everyone shoot at? milliseconds/gain/ frames per second?
I might not always be right but I am never wrong, once I thought I was wrong, but I was mistaken...

Ferengi Rule of Acquisition #59
Free advice is seldom cheap

"Sometimes having is not so pleasing as wanting, it's not logical but it is true"
Commander Spock

Canon DSLR's R7, R6II, 5D, 7D2, 90D 21 lenses incl. 100-400L mk ii, 70-200L mk iii f/2.8, RF600/11
Lunt LS50 DS, LS80 DS, Lunt 102ED, Stellarvue SV80 APO, Orion ST80, 127 MAK, Skywatcher Evostar 120ED, 102 MAK, Celestron 8" Edge HD, 102AZ
Skywatcher EQ6-R Pro
ZWO ASI071MC-cool, ASI174mm, ASI174mm-cool, ASI178MC-cool, ASI290 mini, ASI120MM-S, ASI120MC Revolution Player One mm (178 chip)
User avatar
Lowjiber
Orion Spur Ambassador
Articles: 2
Offline
Posts: 975
Joined: Tue Apr 30, 2019 12:30 pm
4
Location: Las Vegas, Nv, USA
Status:
Offline

TSS Awards Badges

TSS Photo of the Day

Re: Gain and noise in solar imaging

#2

Post by Lowjiber »


Wow Jeff! :) You sure opened a big can-of-worms with that post. LOL

If we're only talking prom shots, I'm literally all over the place. Like you, I use SharpCap 3.0 because higher versions don't allow for gamma control... I've had lots of discussions with Sam Wen about that and we remain in total disagreement about it.

I'll note that I keep accurate records of every shot I take. Here's the data from an image that was the image-of-the-day on Solar Chat last fall. (The Q @ -2 is the Quark setting.)
Screenshot 2021-10-19 060203.jpg
In my non-professional opinion, gamma adjustment simply alters the transition of black-to-white in the shot. (I usually watch the histogram when adjusting gamma... Keeping balance across the "scale". My typical prom gamma is usually around 65.

A similar argument can be made from too much gain. Driving gain too high will induce more noise in/around the prom than can be removed in post-shot processing. My typical prom shot will have a gain pretty close to 116 on average.

Exposure: I shoot most proms around 60ms while my surfaces are around 10ms. I work hard to get my histogram at around 80% to avoid any clipping on the "white side". I'll note here that a "typical" surface shot has and exposure of 10ms with gain = 100 and gamma = 20. (Surfaces are much easier to shoot. LOL)

What all that drivel means is not really clear. I'll note that my seeing here in the desert is usually much better than yours simply because my humidity is usually in single-digits in the fall/winter months. I'd be interested to see what other solar imagers use... Keeping in mind that you & I are using the 174 and others data may vary depending on their cameras.

Thanks for bringing this up. It makes at least good food-for-thought.:)

Clear Skies
John (Urban Astronomer) Apertura AD10 Dob; XLT 150 Dob; XLT 120EQ; Lunt Solar 60 PT/B1200; ES AR102; SW Pro 100ED; 2 SW Pro 80ED's; 90mm Eq; WO Z-61; SW 90mm Virtuso Mak; 2 Orion ST-80's; Quark-C; Cams: Polemaster, ASI120MM-S, ASI174MM & ASI174MM-C
User avatar
Ben Cartwright SASS
Orion Spur Ambassador
Articles: 0
Offline
Posts: 654
Joined: Fri May 17, 2019 10:39 am
4
Location: SE New England
Status:
Offline

TSS Awards Badges

TSS Photo of the Day

Re: Gain and noise in solar imaging

#3

Post by Ben Cartwright SASS »


I have never looked at my histogram, I think I will start or at least check it out. I expose to get what I "think" is right.

On a dry day we are at 60% humidity!! I am also shooting between 10:30 and 12:30 this time of year with the sun low over a house behind me and right over a factory 300 yards away. My skies are very turbulent!

I will be going out today at 10:30 am, not much going on but want to try the 102ED and if it is too unstable the SV80 APO. APO's aren't needed for solar but it is what I have.

wind is 10-15 with gusts to 30 mph and temps around 45 degrees

I also will interested in what people are doing.

BTW I got the Daystar Flat Cap for solar flats, it is GREAT!
I might not always be right but I am never wrong, once I thought I was wrong, but I was mistaken...

Ferengi Rule of Acquisition #59
Free advice is seldom cheap

"Sometimes having is not so pleasing as wanting, it's not logical but it is true"
Commander Spock

Canon DSLR's R7, R6II, 5D, 7D2, 90D 21 lenses incl. 100-400L mk ii, 70-200L mk iii f/2.8, RF600/11
Lunt LS50 DS, LS80 DS, Lunt 102ED, Stellarvue SV80 APO, Orion ST80, 127 MAK, Skywatcher Evostar 120ED, 102 MAK, Celestron 8" Edge HD, 102AZ
Skywatcher EQ6-R Pro
ZWO ASI071MC-cool, ASI174mm, ASI174mm-cool, ASI178MC-cool, ASI290 mini, ASI120MM-S, ASI120MC Revolution Player One mm (178 chip)
User avatar
Lowjiber
Orion Spur Ambassador
Articles: 2
Offline
Posts: 975
Joined: Tue Apr 30, 2019 12:30 pm
4
Location: Las Vegas, Nv, USA
Status:
Offline

TSS Awards Badges

TSS Photo of the Day

Re: Gain and noise in solar imaging

#4

Post by Lowjiber »


Ben Cartwright SASS wrote: Tue Oct 19, 2021 2:01 pm BTW I got the Daystar Flat Cap for solar flats, it is GREAT!
How does that compare with shooting an out-of-focus flat? I've "tinkered" with several methods and have found a simple turn of the focus knob works as well as things like trash bags, saran wrap, etc.
John (Urban Astronomer) Apertura AD10 Dob; XLT 150 Dob; XLT 120EQ; Lunt Solar 60 PT/B1200; ES AR102; SW Pro 100ED; 2 SW Pro 80ED's; 90mm Eq; WO Z-61; SW 90mm Virtuso Mak; 2 Orion ST-80's; Quark-C; Cams: Polemaster, ASI120MM-S, ASI174MM & ASI174MM-C
User avatar
Ben Cartwright SASS
Orion Spur Ambassador
Articles: 0
Offline
Posts: 654
Joined: Fri May 17, 2019 10:39 am
4
Location: SE New England
Status:
Offline

TSS Awards Badges

TSS Photo of the Day

Re: Gain and noise in solar imaging

#5

Post by Ben Cartwright SASS »


does out of focus work on full disk?
I might not always be right but I am never wrong, once I thought I was wrong, but I was mistaken...

Ferengi Rule of Acquisition #59
Free advice is seldom cheap

"Sometimes having is not so pleasing as wanting, it's not logical but it is true"
Commander Spock

Canon DSLR's R7, R6II, 5D, 7D2, 90D 21 lenses incl. 100-400L mk ii, 70-200L mk iii f/2.8, RF600/11
Lunt LS50 DS, LS80 DS, Lunt 102ED, Stellarvue SV80 APO, Orion ST80, 127 MAK, Skywatcher Evostar 120ED, 102 MAK, Celestron 8" Edge HD, 102AZ
Skywatcher EQ6-R Pro
ZWO ASI071MC-cool, ASI174mm, ASI174mm-cool, ASI178MC-cool, ASI290 mini, ASI120MM-S, ASI120MC Revolution Player One mm (178 chip)
User avatar
Solsearcher Canada
Orion Spur Ambassador
Articles: 0
Offline
Posts: 713
Joined: Mon May 20, 2019 12:24 am
4
Location: Ontario Canada
Status:
Offline

TSS Photo of the Day

Re: Gain and noise in solar imaging

#6

Post by Solsearcher »


When you consider the variables that are involved with Ha solar imaging how can any one method be the correct one across the board ??
When someone is sharing information they are stating what works well for them with the equipment they are using . There are a multitude of options and combinations available for Ha solar filters and scopes as well as camera options and the options in the software to operate them .
Although some information may be questionable I have found good information that has helped me on all of the forums over the years .
Showing us that suggestions on another forum did not work for you is beneficial for those using equipment similar to your's and makes a good discussion .
I am not a fanboy of any of the forums but personally was disappointed to see a group of solar imagers on another forum called out as "experts and Guru's" because you do not agree with their methods . Sorry but I can not jump on this band wagon , there is nothing positive about bashing another forum . We are all just trying to do the best we can with what we have .
Solar scopes (Coronado Ha) 60mm double stack , 90mm double stack , 150mm single stack .
W/L scope Williams Optic Megrez 110mm / Lunt herschel wedge .
Night scope Celestron 9.25 XLT
Mounts HEQ6 , HEQ5 , Losmandy G8
Post Reply

Create an account or sign in to join the discussion

You need to be a member in order to post a reply

Create an account

Not a member? register to join our community
Members can start their own topics & subscribe to topics
It’s free and only takes a minute

Register

Sign in

Return to “Solar”