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ZWO ASI120MM not viewing planets

PostPosted: Sat Jun 30, 2018 4:14 pm
by Suttonrog
Hello. My first visit.
I thought that it was time to introduce the grandkids to astronomy, so I bought a really cheap 90mm GOTO Mak, not expecting very much.
I can’t use it outside yet as it is not dark enough while the kids are up, so I decided to practice from my living room and was very surprised when I got viewable images of the moon, Jupiter and its moons, Saturn and it’s rings etc. (even though it was not fully dark and through glass and the London smog)
So I bought a ZWO ASI 120MC. At prime focus the view is similar to my 10mm eyepiece. I started on a TV aerial about a mile away in daylight and it worked. Set up on the moon and got some good video.
Pointed at Jupiter, Saturn and Mars and nothing appears.
I thought that focus or alignment must be off, but going back to the 10mm eyepiece they were still centred.
Is there not enough light from a planet to trigger the camera? I have tried all the exposure and gain settings to no avail.
Any ideas gents and ladies?

Re: ZWO ASI120MM not viewing planets

PostPosted: Mon Jul 02, 2018 12:12 am
by Zippy
Hi and welcome to the forum.

Presumably you are using your camera in full manual mode?
I have not got fully into AP yet but I am aware your settings for Jupiter vs the Moon will be totally different. The moon is so bright your camera settings will be more akin to to daylight photography. Plus your focus will probably need altering as Jupiter is so far away compared to the moon.

Because of the low amount of light reflected from Jupiter you will need to have your camera set between ISO 800 and ISO 1600. Then you will need to experiment with long exposures.
Try increasing your exposure time gradually to about 3 or 4 seconds.

If you want to take frames with longer exposure you will need to be using a tracking mount.
I doubt you will get good results if you try videoing Jupiter because normal video has very short exposure times. You may have to take many, many long exposure stills and then use software to stack and convert the stills into a video clip.

Hope this helps.
Regards Geo.

Re: ZWO ASI120MM not viewing planets

PostPosted: Mon Jul 02, 2018 12:29 am
by Zippy
BTW a quick Google of your camera says that it is capable of long exposures up to 1000 seconds.
Not sure what ISO settings it will do though?
But if you continue to struggle with it you may want to ask your question in a user group dedicated to your camera. ... s/messages

Re: ZWO ASI120MM not viewing planets

PostPosted: Thu Jul 12, 2018 1:01 pm
by The Man with the Corrugated Iron Roof
The only thing I can think of is that Jupiter is much smaller than the Moon and finding it can be a real struggle at times with a webcam-type camera. I don't think it is to do with brightness, as Jupiter is very bright and very easy to over-expose. Although the Moon is brighter, Jupiter's brightness is spread out over a very small area, so the overall effect is about the same.

Re: ZWO ASI120MM not viewing planets

PostPosted: Fri Jul 13, 2018 7:35 pm
by Aratus
Suttonrog wrote:Pointed at Jupiter, Saturn and Mars and nothing appears.

Since you are observing in a less than dark sky, are you getting a white sky, blue sky or black sky when you see nothing? That might give a clue. These cameras have very narrow fields of view, so don't use any barlows (to begin with anyway). You might have to slowly spiral out from where you think it should be to find it. Jupiter will only require a short exposure time of much than less than a second.