Longer focal length scope

[ChrisIS]

I need some Telescope advice please. May as well think about it while I can't go out.

So I have an Eq6-gt mount, and I have used with camera lenses mainly up to a 600mm f4 (which is 150mm in telescope terminology and high quality glass) there is much debate if scopes of the same focal length are better, but the evidence seems to suggest there isn't much in it. So no point getting something in a similar or shorter focal length, my camera lenses do other things during the day so are here to stay.

I can add a 1.4x converter to make it a 840mm without much loss of imaging quality and a 2x to make it 1200mm f8 but at that point it does start to struggle a bit to stay sharp. 

Galaxies this spring make me think I do need something with a longer focal length as an option.

I want something for imaging only with an Asto modified 5d mkii so a full frame sensor which I either need to consider, or get a astro camera that will deal with a scope with a smaller imaging circle.

I don't mind paying for something decent, it's a real waste having to upgrade, learnt that with lenses and they make equivalent telescopes look cheap.

I've read lots, and haven't really narrowed it down. I remember the immense frustration of getting everything I have to work together and I don't currently need to worry about mysteries like back focus, collimation etc I just plug it all together having cobbled together the right spacers and scope rings to deal with a lens, then shout at the software until it all plays nicely.

I've included an example of where I am on my journey so far. I

Edited April 10, 2020 by Cornelius Varley
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[jambouk]

I would list the targets you are thinking of, think if you want to start guiding, think if you want to use filters (how sensitive is the camera to Ha), how are you planning to focus, is this a semi-permenant set up or taken down each night.

I think the potential targets is The first thing I’d think about. Then look on astrobin for these targets and see what scopes and integration times are used. That may help narrow things down.

James

[MarkAR]

Might be worth having a look at Altair Astro offerings, they have kit suitable for full frame DSLR.