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Black pictures with ZWO 120mm-s

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#1 anwenet

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Posted 20 March 2018 - 06:27 PM

My issue is the I am getting black picture. I tried in many application, same results - black
I started with 1 second exposure and all the way to 120... nothing.. just black.
When I install this little lens which came with ZWO 120mm-s, I get a picture in all applications.
And when I remove the lens and attach 2” or 1.25” adapter and attach to my telescope — black picture.

I tried playing with focus, all the way in and out.
When I take it out of telescope and point to outside light... I would think I should get something... nope.. black picture

What am I missing here?

#2 photoracer18

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Posted 20 March 2018 - 07:14 PM

What are you doing to focus the camera? I mean really get it in focus. I am sure the little lens is fixed at infinity focus so that is why it shows something. You need to find the focus point by looking at images as they come off the camera. I am sure the camera has something in the way of a focusing technique. Neither all the way in or out will be in focus, you have to find the focus point of your system yourself. Maybe a focusing mask on the front or some other method. With a flip mirror you can do it with a par-focalized eyepiece in the upper position, even in daylight. That is the way the older Meade cameras worked and why the camera came the a 1.25" ring so you could lock the camera and eyepiece focus down to the same point. Nowadays most use programs to get focus lock.

#3 frito

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Posted 20 March 2018 - 08:03 PM

i have a asi120mc, it will be nothing but black unless you get it near focus. likely whatever your trying to use to get it in focus with doesn't have the correct spacing range to bring it into focus. if you put it into a scope in daytime indoors you should at least see the image turn white if the scope is aimed at a white wall etc once its somewhere in the wide ballpark of being in focus. 



#4 rgsalinger

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Posted 20 March 2018 - 11:37 PM

Astronomy software has to stretch images so that they can be displayed on a monitor. That can result in black images when you are both underexposed and over exposed. So, the first thing to do is to inspect the black exposures and see what the actual ADU values are.

 

However, this really does sound like a focus problem. If you rack all the way out and cannot see anything at any point along the way then you either need a couple of spacers (common) or you are going to need to put a positive lens in front of the camera. Carefully pull the camera away from the scope while looking at your monitor. If you keep it reasonably centered you might see something an inch or two out. If you never see anything then your focal point is too close - get a positive lens.

 

Finally, make sure that you have a bright star in the FOV of the camera, it's really easy to go right through focus with one of these and a bright star stays visible even when it gets "big".

 

Rgrds-Ross




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