Which camera for live feed?

[emadmoussa]

I'm not sure this is the right place to ask. 

I was asked if I can deliver a live feed of the moon, DSOs, planets, etc, to a group of kids in a different country over the internet. 

I don't have much experience with cameras and my budget is a bit tight. What camera can be hooked to the scope that can do, say, live exposures, comfortably pick up meteorites, satellites, or even flying witches on sticks?  

Is this camera any good? ZWO ASI 120MM USB 2.0 Mono Camera   

[vlaiv]

Quite a bit of different requirements packed into it.

Pretty much any sort of camera / scope will do for live feed of the moon. Depending on scope focal length / camera sensor size, you will be capable of either having whole moon in frame, or just a part of it. Moon is bright enough so you don't have to worry about longer exposures - regular video feed will be ok.

Same goes for planets, well at least Venus, Mars, Jupiter and Saturn - but you will need long focal length scope to have video feed that can actually display any features (like Venus phases, Jupiter belts, or Saturn rings). Atmosphere will play significant part in quality here.

DSOs are different story - you want here something resembling EAA (well it is one way EAA is done). You will need at least couple of seconds exposures, and you will need to feed not real time video, but rather progressive stack of subs. You will start by creating single sub and each additional sub will be stacked to output (so not streaming each individual sub, but rather first sub, then first + second, first+second+third, and so on. This means that you will probably be unable to display any DSO in short period of time and you will need at least couple of minutes of this sort of signal gathering to get anything worth displaying. Luckily since technique is progressive - kids can be entertained while more and more features pop into view. If you are doing any sort of presentation, you can make things more interesting by explaining features of DSO (like size, formation, type, what ever) while it is slowly coming into view. Here key is to use as much aperture at short focal length (match focal length to camera pixel size - aim for somewhere around 1.5"-2.5"/pixel), also include proper calibration of frames - if using CMOS cameras, master dark and master flat is all you'll need.

Meteors, satellites are again different thing all together. Most scopes have too narrow FOV to be able to display those. You need either very high quality mount to be able to track them at high speeds that they are moving (in case of Satellites, where trajectory is known), or need different approach altogether - look into "all sky cameras". Again this has less to do with camera and more to do with lens - you need very short focal length lens (like 10-20mm) and wide FOV. That way you can stream all sky view and they will be able to spot satellite / meteor streaks when they happen.

ASI 120MM is capable of doing all of this, but for each use case you will need different software / scope / lens and technique.

[emadmoussa]

Thank you! That's informative.