Smart Histogram always way too dark, no matter what

[Menno555]

Okay, either I do something wrong or the Smart Histogram doesn't like me or my setup I posted bout this before but I just don't get it why it is not working for me.

I do the procedure with the little brain and that gives no problems. I choose for example 30 seconds minimum, 60 seconds maximum, 10% Read Noise Limit, 60 minutes stacking time and Max Dynamic Range.
I apply the suggested settings (or settings that are suggested in the line shown in the Smart Histogram tab) and always the whole histogram is totally on the left, showing only small, tiny lines. So narrow that is almost impossible to see. This is always like that.
When I use the Smart Histogram settings (with or without flats and darks), the result is a very, very dark captures. A program like DeepSkyStacker can do absolutely nothing with it. Autostakkert can but I have to crank up the brightness there to it's maximum to select stars.
When I open the stack in Photoshop, literary nothing can be done with it: some stars and the object are there and can be made visible but only after 6 or 7 Level and Curves actions (normally 2 or 3) ... but it really is of no use because only very little data is there.
Using version 3.2.6366.0 on Windows 10 but it was the same like 6 or 7 versions ago.
This with a Zwo ASI385MC (latest drivers installed) in Bortle 8.

And just in case, I did another sensor analysis. The green crosses were in a straight line but I don't know how to read the other data and if that is okay or not for this camera? See screenshot.

ASI385MC_sensor_test.jpg (140.62 KiB) Viewed 1893 times

[admin]

Hi,

there isn't anything stopping you from using longer exposures than those suggested by smart histogram (as long as your mount tracking and guiding can cope with the longer exposures), particularly if you need to do so to get the frames to align and stack.

The values suggested by the smart histogram are those where there is practically no more improvement to be had in the detail in the faintest parts of the final stacked image by increasing the exposure further. For instance, if smart histogram suggests 60 second exposures, you will get essentially the same quality final stacked image from following the smart histogram instructions and taking one hour of one minute exposures and stacking those as you would if you instead took one hour's worth of 15 minute exposures. Of course for the 15 minute exposure option you probably need a new (and much more expensive) mount, better guiding, a more deeply called camera, etc.

The whole idea of smart histogram was to try to fight against the problem of a number of users on various forums continously suggesting that longer exposures were the only way to get better images. If Smart Histogram says 60s is long enough and someone on a forum is telling you that you need to take 5 or 10 minute subs to see more nebulosity then Smart Histogram is correct and the forum user is talking rubbish...

Hope this helps,

Robin

[oopfan]

Menno,

Robin is correct. I have to use longer exposures because my CCD has Read Noise of 5.3 electrons. So when you see me using 90s it is because of that. One other thing that affects my decision-making is how faint the target is with respect to the sky background (my Bortle class). If I am trying to capture a target at the limits of my seeing conditions then I will use a longer exposure in order to get a better signal-to-noise ratio per frame. I think that is where Smart Histogram and I deviate. Smart Histogram considers only the sky background but I consider both the sky background and the target's surface brightness. Call me a nutcase but I have always believed that if I can't see the DSO in a single subframe then I might want to reconsider imaging it. I know that people will disagree with me on that. I like bright images. If I am going to devote hours upon hours to a target then I only want to invest time into worthy targets. Of course there are exceptions to this rule but it is up to you.

Brian

[Menno555]

Thanks Robin

But I still don't understand why I see nothing when I use the Smart Histogram settings? Even the lightning-symbol is almost showing nothing then.
Also more confused now: you write:

"The values suggested by the smart histogram are those where there is practically no more improvement to be had in the detail in the faintest parts of the final stacked image by increasing the exposure further."

But for me there are no details when using the Smart Histogram, I must either increase the exposure time or the gain dramatically before something is showing.
Don't get me wrong: I can use SC just fine and do follow that "more but shorter captures"-rule myself
I just don't get it why there is such a huge difference in what the Smart Histogram is suggesting and what I end up with. I just want to try it, it's one of the reasons why I did get Pro

[oopfan]

Menno,

I just want to add that the topic of "exposure selection" is one that frustrates the vast majority of people entering astrophotography. I have no doubt that many people have given up on it because of it. Robin's Smart Histogram puts an end to that frustration. Robin should win an award for it, if he hasn't already. I just want to say that you have freedom. Use Smart Histogram as a stepping off point and then experiment from there.

Brian

[oopfan]

Menno,

I am sorry but I don't keep up with everything you post so let me understand something. Was there any time when you were happy? If true then what has changed? New camera? New location? If everything is the same then did things start going wrong when you upgraded to a new SC version? I'm sorry that you have Bortle 8 skies. It can be very challenging. I know another person on the forum with the same and it frustrates the daylights out of him.

Brian

[Menno555]

Thanks Brian.

I myself don't know anything (or understand it) about "Read noise of 5.3 electrons" or any of those terms. I tried to read and understand here and on other sites, but it's way over my head. Story of my life: I work with dangerous chemicals, managed start-ups for pharmaceutical departments, can describe complex reactions in the finest detail. But all self taught, deviced my own ways to understand. I am just the embodiment of an autodidact
But the same goes for me: if I can see a bit of the object in 1 subframe, I will try. Although, M97 was an exception and that turned out great

But thanks for the clarification. So in fact it comes down to that the Smart Histogram works but only under certain circumstances?
Maybe it's of use to mention that somewhere? Because as it is described now, it looks like it always works. Hence my confusion.

Menno

[Menno555]

Menno,

I am sorry but I don't keep up with everything you post so let me understand something. Was there any time when you were happy? If true then what has changed? New camera? New location? If everything is the same then did things start going wrong when you upgraded to a new SC version? I'm sorry that you have Bortle 8 skies. It can be very challenging. I know another person on the forum with the same and it frustrates the daylights out of him.

Brian

Ah no, not anything of that! Believe me, I LOVE SharpCap, always happy with it!! Maybe it's my English that describes it wrong or a poor choice of words. I just want to understand things and also understand why something is not working. If I sound degrading or angry or unhappy ... that is really and has never been the case. Sorry if I looked like that
And nothing changed, it's been there like that when I started 2 months ago

Menno

[oopfan]

Menno,

Don't mischaracterize what I said. Please answer the question: Were you ever happy with your images? I remember your M97 and how pleased you were with it. So what has changed? Camera? Bortle class? If neither then can you point to a version of SharpCap where it seemed to go wrong? If you can't then there is a distinct possibility that with your success that you are now trying to push the envelope but your skies just can't deliver.

Brian

[oopfan]

Menno,

I see. It's just that if you are asking for help then you need to give a definitive timeline of what happened.

Brian