[RickS (Rick)]

Originally Posted by sil

What do you want to shoot?

That's definitely the #1 question you need to answer. Starting with planetary vs deep sky. If the choice is deep sky then you need to think about what sort of objects, field of view and image scale you need.

Originally Posted by multiweb

The higher the QE the more sensitive your camera is and it will depend on wavelength so you can find the curves online for your chip model. 80% is very good. Mine is ~50%

Just one point of caution on QE: some manufacturers supply a graph showing absolute QE which is what Marc is talking about above; other manufacturers supply a graph showing relative QE. A relative QE graph will show you how the sensitivity of the camera varies with wavelength but won't allow you to compare actual QE with a different camera.

Originally Posted by Jasp05

Full well capacity is the depth of the pixel to record signal before being saturated. Is a small well capacity a bad thing? There can be some quite large differences in this parameter. Example being an ASI1600mm has 20k full well but an asi294MC PRO has nearly 64k. 3 times the capacity..

Deep wells are useful with a camera that has high read noise when you'll want to do long exposures. Shallow wells are fine with a low read noise camera and short subs, and this combination is less demanding on your guiding.

Originally Posted by Jasp05

How much does actual Pixel count affect the images? as in Megapixels. Does more Pixels make the image seem smoother with more detail? (With the understanding that more pixels generally means smaller pixel size and more exposure time required).

More pixels will give you an image that looks better at larger sizes and also provides the option to crop and still have something left. As you say, this will come at the cost of slower imaging.

When you think about pixel count and sensor size you need to also take the scope into consideration. If you have long focal length then larger pixels will be a better match. For a short focal length refractor then smaller pixels will give you more detail. This needs to be considered in terms of your overall imaging goals (type of objects, desired field of view, desired level of detail = image scale.)

Originally Posted by Jasp05

And is read noise / dark current a major factor for a beginner? looking at the stats of the ZWO cameras these 2 parameters don't seem to vary a whole lot. somewhere between 1.2 & 2e. So I'm going to say it's not a huge priority?

The length of time for individual subs of good quality increases with the square of the read noise, so it is a consideration especially if you want to do short subs. CCDs typically have much higher read noise than the CMOS cameras you have been looking at. Note that even CMOS cameras can have high read noise if you run them at low gain settings.

Originally Posted by Jasp05

Budget is a bit tight at the moment.(Around $1k ) But I think I would spend the extra if it was going to make a worthwhile difference. I hear alot of good things about the ASI1600mm PRO but I also see ALOT of them for sale. So not sure what to make of that.

The ASI1600mm is a good camera if it suits your needs. I'm using one and the only thing I'd like is a much bigger version of the sensor I wouldn't use it on one of my long focal length scopes but for camera lenses and short focal length refractors it is a great fit.

I'd recommend trawling around Astrobin taking a look at pics taken with some of the cameras you are interested in. Take note of the other gear used and the amount of integration time. That might give you some ideas...

Cheers,
Rick.