SharpCap Forums

Question: do I miss a lot of signal when only using around 15% of the histogram? When I try the method in this great video, so with the left side of the white line close to the left side and the right side of the white line at around 50%, I get way to bright captures with way way to much noise.
I do get results though when the right side of the whits line is at around 15%. But now wondering if I miss a lot of signal because of that.

Check you havent got the mini histogram auto stretched .... there's three small buttons on the right hand side of the mini-histrogam. Hover help will tell you what they do. The top one is the auto stretch. The middle one is to reset so there is no stretch. And the bottom one saves the image on screen to a file in the sharpcap folder. Always click the reset button (middle button) on that mini histogram before you start stacking.

If you had reset the histogram then there will be a straight line going right across the histogram from bottom left to top right.

If you have done all that and the histogram is falling to the bottom horizontal line at around 50% as you say ... but the image is way too bright still on the screen, then you should check the display settings on the right hand menu bar as it could be you've turned up the gamma way to far. Leave those at their default settings.

Cheers.

There is no auto stretching and Reset is done.
And I don't have Gamma settings, I have a Zwo ASI385MC camera.
I have attached 2 simulated screenshot. Ignore all the other settings, the histogram simulates what I get at night.
Histo1 is with the right side at 50%. I get lots of noise then.
Histo2 is what I get when the noise is good enough for for stacking I use DeeSkyStacker for that.

Hi,


If you look at how the peak of your histogram aligns with the coloured bars above, you can see that there is a significant amount of histogram that is in the orange region – this means that you are not running long enough exposures to operate your sensor in a way that minimises the effect of read noise. Really want the bulk of the histogram peaks to be to the right of the end of the orange section of bar.

Do note however that really you should try changing to 16 bit mode – that will probably cause the orange region to shrink considerably to the left. By continuing to work in eight bit mode you are giving up information.

Cheers, Robin

Robin
Sorry for the confusion, but the whole screen is just a test setup during the day. Normally it is the way you describe it and it is all in the green part and set to 16 bit

These screenshots are only to show the histograms: that with the white line ending at 50%, I get noise similar as shown and no amount of stacking can remove that. And with the white line at around 15 to 20%, then it is workable for me.
So the question is if I am at 15 to 20% at the end of the white line, but have a good shape in the line ... will I miss things in comparison to the video where the white line ends at 50% with all the settings you described.

Hi,

As long as the histogram peaks clear the orange parts of the smart histogram bars then you don't gain any extra by moving the peak further to the right.

There is an awfully long, and somewhat mathematical, explanation of why this is true in this thread - viewtopic.php?f=35&t=456

Cheers, Robin

Hi Robin

Will read that for sure ... maybe I skip the formulas
My main observing place (balcony at home) has a very diverse atmosphere being it in the city. One constant is Bortle 8, so for me interestingon exposure times. Allready did notice that without a LP filter of some sort, exposures of 60 seconds ia the max. 90 is possible but after stacking 100 captures or more, the light pollution is starting to show.

Menno