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Sharpcap live stack problem

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#1 skydivephil

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Posted 09 February 2018 - 06:09 PM

I lied the live stacking app in Shaprcap 3.0 . The problem is it didn't seem to do anything. I thought the picture would get brighter and see more detail. But nothing really happened. 

 

I have made a video of what I saw. Its below :

https://vimeo.com/255117467

 

Any tips much appreciated. 



#2 roelb

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Posted 09 February 2018 - 06:20 PM

I suppose that when you have only stars in the FOV their will no big change while stacking.

If you capture a DSO you must see building up the image with each stack.


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#3 neaptide

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Posted 09 February 2018 - 06:27 PM

What was the object you were observing? I notice you are using a gain of 133. Depending on what you are looking at this may not be high enough in combination with 7 second exposures. You should be using a higher gain of 300-350 until you are sure you are on target and then adjust gain and exposure time until your happy with the image you are getting. The live stack tab shows your are stacking exposures so that’s good. You should go to the histogram tab and adjust the histogram once you confirm you are stacking. This will really help bring out the faint details in your image. 

 

Sharpcap takes a little while to get used to. There’s a lot of info and settings to digest at first but after a few sessions it really is an easy program to work with. Keep at it and ask questions. 

 

As roelb suggests, if you are just looking at a sparse area of sky with just a few stars you will not see much of a difference with stacking. Try a bright object like M42 to start with. 


Edited by neaptide, 09 February 2018 - 06:31 PM.

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#4 gun4hire

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Posted 09 February 2018 - 08:28 PM

+1 gain too low. Seems like I need over 300 gain to see anything, but that is with a 224 chip.

 

Unless there is a DSO hiding in there we can't see and more stars in the background. You may just be seeing the stars that are potentially visible and stacking won't reveal something that ain't there.

 

gun----- my opinion is worth 1/4 a cent.


Edited by gun4hire, 09 February 2018 - 08:34 PM.


#5 MartinMeredith

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Posted 10 February 2018 - 03:03 AM

Stacking won't necessarily make objects brighter since the displayed intensities are (typically) normalised unless you use sum stacking. What it will do is improve the signal to noise ratio. Combined with normalisation this means you will see a reduction of the background. If there are faint objects lurking in the background they will become visible (not brighter -- they were there all the time but swamped by noise).

 

In your video it looks like your black point is set quite high, perhaps clipping some of the background (and any faint DSOs, assuming they are present). If you set the black point lower so that you can see some noise in the background you then ought to see a reduction in that noise as a result of stacking. I typically start with the black point set low for this reason. As others have said, if you only have stars then you might not see much of an improvement (but there are nearly always fainter stars visible).

 

Cheers

 

Martin


Edited by MartinMeredith, 10 February 2018 - 03:03 AM.

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#6 skydivephil

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Posted 10 February 2018 - 04:54 AM

Thanks guys will give this a go and let you know 




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