General settings and help on a galaxy

[CKP]

Firstly, I think this sub forum should be called the CKP forum 😆 

Is there a general settings guide on what to use for different targets.

I'm guessing the settings for galaxies would be different to nebula and probably clusters too?

I've done some reading and watched some videos on galaxy eaa and quickly realised m51 is the goto galaxy for tutorials, is it the easiest? These people make it look easy!

I went out last night and tried to get an image of m51 with its spiral arms, not for photo quality but just to watch the image get clearer on each stacked frame.

I got m51 centered and played with the exposure and gain. Everything went out the window and I settled on 10 second exposure and 200 gain. It looked the best settings on screen.

After 20 frames, there were no arms visible, the image looked the same as when I first started the stack. I saved the image to see if I could play with it more.

Once I loaded it onto my phone, I could see a little of the structure of the arms, not much but I couldn't see this while it was stacking? 

Is there something wrong I'm doing wrong?

I've attached a photo which amazes me. I know it's basic to most so I want to learn and understand how to get better.

20 x 10 seconds exposure and 200 gain.

[happy-kat]

20 frames is not very many but you can make out m51, have a look and see how many frames other people generally use for this type of imaging. If you are using sharpcap pro you could have a look at the sensor analyser tool which can be run when it's daytime it works out what settings for your camera. It will be interesting to read your replies as they'll help me too.

 

[CKP]

I know I make alot of posts on the most basic things but I hope it helps others the same as it's helping me. 

I guess I got hung up on the amount of frames I used compared to the amount some people are using in the videos.

I haven't got sharpcap pro yet, I thought I'd ust get used to the basics first. 

[M40]

I think thats a great picture 👌 200 seconds later and you have a galaxy in the bag. Can you let us know what software you are using as we could then give you a few pointers as to settings.

I use ASIlive and then play with the settings until I am happy. Picture below gives you an indication of settings in ASIlive but I tend to go for one target and then just keep playing until I get the best I can, that picture is a simple screenshot I think about 210 seconds similar to yours.

. 

 

Another thing to consider is light and how it is affecting your picture. On your telescope I think you can get a sock that encloses the open section of the tube?? not sure but may be worth a search or two in the section on the site.

 

[Martin Meredith]

Hi

I don't know what software you're using but I wonder how much histogram manipulation you're doing? This will have a much greater effect than changing the individual sub exposure.

Here's a single 15s sub of M51 with little or no histogram manipulation

(all images from 8" f4 reflector + Lodestar X2 mono guide camera on non-guided alt-az mount)

and here's the same data with a different 'stretch' (sometimes called 'curves', or adjusting the 'mid point')

If you're not seeing any improvement with stacking, then perhaps the software is failing to align from one frame to the next? You will definitely see some improvement from 1 to 2 subs, then from 2 to 4, etc. Each doubling will create the the same amount of improvement.

Even so, if you don't manipulate the histogram appropriately, you won't necessarily see much improvement from stacking. Here's 4 subs stacked using no manipulation:

so barely any change from the single sub case. Here's the same 4 subs with a proper stretch:

and the improvement from the one sub case is obvious.

If your software allows you to save individual subs and then reload them later (many do), you could explore the histogram controls at leisure rather than during the rare clear nights... 

cheers

Martin

 

[CKP]

57 minutes ago, M40 said:

I think thats a great picture 👌 200 seconds later and you have a galaxy in the bag. Can you let us know what software you are using as we could then give you a few pointers as to settings.

I use ASIlive and then play with the settings until I am happy. Picture below gives you an indication of settings in ASIlive but I tend to go for one target and then just keep playing until I get the best I can, that picture is a simple screenshot I think about 210 seconds similar to yours.

. 

 

Another thing to consider is light and how it is affecting your picture. On your telescope I think you can get a sock that encloses the open section of the tube?? not sure but may be worth a search or two in the section on the site.

 

Thanks M40,

The software I'm using is sharpcap. 

I tried asilive last night and it was just white noise. I had to turn the brightness right down to get a darker background but then got lost trying to work it out.

I will have to have a look for the sock, when I played with the finished image I could see light creeping in, maybe from a nearby streetlight.

[CKP]

1 hour ago, Martin Meredith said:

Hi

I don't know what software you're using but I wonder how much histogram manipulation you're doing? This will have a much greater effect than changing the individual sub exposure.

Here's a single 15s sub of M51 with little or no histogram manipulation

(all images from 8" f4 reflector + Lodestar X2 mono guide camera on non-guided alt-az mount)

and here's the same data with a different 'stretch' (sometimes called 'curves', or adjusting the 'mid point')

If you're not seeing any improvement with stacking, then perhaps the software is failing to align from one frame to the next? You will definitely see some improvement from 1 to 2 subs, then from 2 to 4, etc. Each doubling will create the the same amount of improvement.

Even so, if you don't manipulate the histogram appropriately, you won't necessarily see much improvement from stacking. Here's 4 subs stacked using no manipulation:

so barely any change from the single sub case. Here's the same 4 subs with a proper stretch:

and the improvement from the one sub case is obvious.

If your software allows you to save individual subs and then reload them later (many do), you could explore the histogram controls at leisure rather than during the rare clear nights... 

cheers

Martin

 

Thanks Martin,

I'm using sharpcap.

I haven't really played with the histogram much as I don't really understand yet. The one thing I did do was move the black level up to the start of the peaks.

The way you've explained it makes it seem like thats the direction I need to be going in.

[CKP]

@M40 or anyone using asilive...

When you open up the software and turn the camera on, after the first exposure does the image on the screen show stars on a dark background?

When I do it, the screen looks like white noise and I can barely see the stars behind it.

This does not seem right, I'm sure its the settings but I gave up on it simply because I also have sharpcap.

I watched a video with someone using it and showing how simple the userface is, but he started with shining stars on a black background. 

I would like to use it but don't know where to start?

[M40]

I haven't yet managed to start with a dark background, there is always a level of noise.

I am still very much in the baby steps stage which is why I tend to select one target and then keep playing with the settings. Like you, I downloaded sharpcap plus other software and realised that I need to learn one of them so at the moment I am sticking with ASIlive but I can see me switching to sharpcap later because of the other tools within it.

There is a fair amount of noise in the background of my pictures which I try and minimise through the settings but my next step is to start taking dark and flat frames and incorporate them, this action will, as I understand it, help to remove noise from the camera. Have a look through some of the others pictures and in particular, look at the info around which pictures include darks/flats/bias frames and which do not. All the best.

 

[CKP]

I'm also going to start one target at a time I think.

The image of m57 I did a few nights ago was beginners luck I think!

 

Edited August 8, 2022 by CKP

[CKP]

@Martin Meredith

Does your image have darks? i played around last and i seem to be going backwards. I have to do post processing to see details.

I think I did 33 stacks and tried to play with the mid level as well as the black level, but I couldn't bring out any detail?

Should a short exposure have a higher gain and a longer exposure have a lower gain? When I processed it, the brighter the image the more detail has come through. The image seems to get brighter on a higher gain, if I remember correctly.

 

[Martin Meredith]

No, mine didn't have darks, but they won't resolve this issue in any case.

Did you save any FITS files from your last session? If not, that's the thing to do next, because then you can reload them or someone on the forum can take a look to see if its an image manipulation issue or if its a gain/exposure/other capture problem.

 

[CKP]

40 minutes ago, Martin Meredith said:

No, mine didn't have darks, but they won't resolve this issue in any case.

Did you save any FITS files from your last session? If not, that's the thing to do next, because then you can reload them or someone on the forum can take a look to see if its an image manipulation issue or if its a gain/exposure/other capture problem.

 

Is the fits file the written file that has these setting values inside? I think I still have the file, I'll have a look when I get back home.

How do I save the images on sharpcap?

When I press save it saves a single image?

I need to save the individual images so I can learn how to do it.

[Martin Meredith]

I can't comment on Sharpcap as I've never used it (doesn't work on the Mac) -- perhaps someone else can comment. What you want though is not the 'saved as seen' (or whatever it is called) but the actual FITs file(s) corresponding to each sub, or the single FITs file corresponding to the stacked image. There will be some settings written in the header but those don't matter much at the moment. By inspecting the actual data in the image it will be possible to see if it is a capture issue (camera problem, gain setting too low, exposure too low, etc) or a manipulation issue (poor choice of stretch, blackpoint etc), which I'd suggest is the first thing to sort out.

[CKP]

I've had a look for the fitts files and found the spec info. I have also added the photos for reference.

I think the less stacked image come out better, I guess I messed up badly on the second attempt!

Stack_16bits_13frames_208s.CameraSettings.txtStack_16bits_13frames_208s.fitsStack_33frames_440s.CameraSettings.txt

[Martin Meredith]

Thanks for providing the FITs from the stack. If you have a single sub that would also be informative.

Bearing in mind that my software doesn't handle OSC particularly well, the best I could obtain was this:

The highest signal is in the green channel

The signal quality is lower than I'd expect for a 208s total exposure unless you live in a light-polluted area (the black point is pretty high, suggesting a lot of light pollution). You can get around this to some extent by stacking more images. Counter-intuitively, I'd be tempted to lower the gain a little so as to increase the range of intensities in the image.

Edited August 9, 2022 by Martin Meredith
typo

[CKP]

I'll have to save the next attempt using every save option.

What is OSC?

Do you play with the different colours until you get the desired result?

I do have a fair bit of light pollution living in a built up town and having a lamppost close by.

EDIT : would you recommend extending the exposure from 20 seconds to 30 seconds and add more stacking as well as lowering the gain?

Edited August 9, 2022 by CKP

[Elp]

OSC = one shot colour as in RGB colour camera so called because it produces a "finished" colour image in one shot.

Eeva from what I understand works exactly like astrophotography, you're taking individual images and stacking them to improve the result, so the longer over you spend on a target the better it'll become. APers spend hours on single targets but I guess that's why eeva exists to bridge that gap between ap and visual. You need to choose settings to suit, the targets, your own personal environmental shooting conditions which you'll generally have to work out, light pollution, direction of shooting etc.

Some galaxies and especially star clusters tend to be bright compared to nebulae so you can generally resolve detail between 10-60 seconds (tracking dependent), nebulae from my experience have to be imaged from 60s bare minimum (unless it's Orion) and the limit goes into many minutes before it becomes redundant exposing single subs any longer.

Camera setting general guide, lower gain = higher read noise (from camera sensor), higher dynamic range (higher bit rate = more shades of grey/colour information that can be defined from black to white/full colour saturation), higher full well depth = amount of electrons that can accumulate on a sensor pixel before it becomes fully saturated. Higher gain = everything described above comes down including the read noise but at the cost of lower dynamic range and full well capacity. 

You'll need to experiment but as a general start many people use unity gain which is recommended by the camera manufacturer as a kind of medium between the two extremes.

If you've got light pollution filling the sensor image you'll have no choice but to lower the exposure time and stack more images to average out what you want to capture (signal) from the light pollution, better yet, relocate your equipment away from the light pollution if you can.

Edited August 9, 2022 by Elp

[CKP]

There is alot more to it than just point at a target and hit the stack button!

So, the best option would be to start with a lower exposure and gain and run a few stacks. See how it looks and then try adjusting gain and exposure before playing with the histogram?

A quick look on google says that my camera doesnt have unity gain, so I guess it's going to be a question of trial and error.

[CKP]

I had another go last night, practice makes perfect and all that.

I went for 30 second exposures, but after 9 minutes it started ignoring frames saying last xx frames couldn't align. Is this to do with tracking?

Also, I saved the raw files but when I loaded them onto sharpcap they were black and white, there was no histogram to play with?

I did also take an image of Albireo, just to see if it would show the split and the colours too.

[oldfruit]

If you look up on the EEVA discussion Tiago Ferreira, he has posted some excellent tutorials. He also uses Sharpcap which is useful.