Need help buying a new monochrome camera for my C11

[Chrb1985]

Hi!

Its been some time since my last post now.

I finaly decided to build my own pier/mount for my neq6 pro. I also sold my trusted ZWO ASI174mm and i just thought i would buy the ZWO ASI290mm.

Turns out its not that easy.. After scouering the forums and using formulas and calculators i find that for the c11s f10 its impossible to get sampling with 2x barlow in fact the 290 is worse than the 174 for my scope..

So im really lost here. what should i do? When i use the calculator it says that 290 is ok for planetary with 2x if i have a good mount but it leads to over sampling. and on the zwo website it is some pictures from the chile obeservatory where they use 290mm on a cassegrain with f17 i think it is, the pictures a crystal clear...

I attached a screenshot where i use one of the baader combinations to acheive f17 with my scope. if i assemble my barlow to acheive f17 and buy the 290mm will this work out good? or is it best to not use barlow at all? Is it still okay with the 29mm than? I really need help guys..

[Cosmic Geoff]

The recommended f-ratio for planetary imaging with a scope depends on the pixel size in the camera.  This is often overlooked.  With a pixel size of 2.9um (as in the ASI462MC, for instance), this will match a f10 SCT, depending on whose advice you are following.

The ASI290mm and the ASI462mm are quite similar except for some details of the performance.

In practice I found that the ASI462 worked well with my f10 203mm SCT without a Barlow lens and adding a Barlow conferred no benefit.  New and more advanced cameras are introduced frequently. (The ASI462MC is already discontinued.)

[PeterCPC]

Also consider the ASI662.

[Fegato]

I'm no planetary expert, but I read that for planetary imaging there's a formula which suggests you go for an F ratio that is 5x your pixel size.

See this thread on CN - https://www.cloudynights.com/topic/675179-“optimal-focal-ratio”-equation-and-question/

For the 290 that would be F/14.5.  I thought that a 2x barlow with your F/10 would make it F/20?  I would think this may be a bit much. I have the same issue with my C8, and would try a 1.5x barlow plus an ADC if I could ever  get round to it.

[newbie alert]

Where you place your sensor also dictates your focal length, which in turn alters your f ratio...  Having perfect sampling won't  automatically turn your images into Damien peach quality overnight..