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ZWO ASI 120MC-S - cannot see anything


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New to this so please bear with me and apologies if this has been asked before

I fitted a ZWO ASI 120MC-S camera to my 4" reflector telescope in the hope of being able to image Jupiter\Saturn last night with no luck

Downloaded the drivers and ASCOM software from the ASI website which all seem to work fine as I could image a nearby street light with the camera attached to the telescope and get a clear focused image on the laptop

But couldn't see anything when looking at Jupiter and then later on at Saturn - could observe them fine through the eyepieces but just a black image on the laptop even after refocusing on the street light and pointing at Jupiter\Saturn

Any advice would be much appreciated as I have a 200P on order so would like to get the camera working for when this arrives and before Jupiter disappears for a while

many thanks

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Firstly the streetlight will be much too close to focus on. What you should do is to point at a very bright star (use an eyepiece to centre) then attach the camera and play with the exposure controls until you can see it on the laptop. Then focus the camera using the telescope focuser. When you are happy that the focus is ok, swing back to Jupiter/Saturn and adjust the exposure again.


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This could be a number of things but lets get the most obvious of the two out of the way first:

Focus: If your focus is a fair bit off, you won't see anything. As the focus moves closer to the focus zone, you will see diffuse rings which will get smaller as you come closer to focus until, eventually, they will resolve into the things that you are trying to see. The focus point of a star or planet is significantly different to anything that you focus on in your local surroundings so if you have focused on a street lamp, you will need to refocus on a star or planet.

The second thing is the length of your exposure: if it's too short, you won't see anything. If you are trying to live view with video, your gain will need to be turned up and if you are trying to capture a still image, the exposure will need to be at least a few seconds long to see stars. Planets are closer and therefore brighter, so exposures for planets tend to be shorter.

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I'd also suggest that  you didn't manage to point accurately enough at Jupiter to get Jupiter onto the small imager chip.

You have to align your finder and the imager very accurately on say a moon crater.

The act of swapping between an eyepiece and the camera will likely throw you off target.


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