Secondary mirror size for 30 telescope.(Photography).
Hi, Can anyone help me?
I was talking to a few chaps at Astrofest on the weekend and was pointed to ice in space.
I wanted to know what size secondary mirror I would theroricialy need to turn my f (4.818) Dob into a photographically scope? For visual it has a 4.5 inch secondary currently.
I've been looking at an equatorial platform from Tom O (USA) as well and wondering if the f ratio 4.818 is going to be a major disadvantage? The EQ has a provision for a plug in guider eg ST4.
Just playing with the figures at present.
Thanks.
Depends how big the chip is and how much vignetting you are prepared to accept... A 5" secondary would be fine for a small chip, but you would need a 6" if you intend to cover something like a 16003
A more complicated alternative if you wanted to keep your secondary, use a low profile focuser that gets the CCD chip closer to the mirror.
Downside is you will have to extend your truss rods by the same distance that you gained to achieve focus.
In essence, the type 2 Paracorr can be used for both Visual and imaging without the need to change your pole length! I have the type 1 sadly but am looking to change it at some point.
Not sure if you're already aware, but check out some of Alex Cherney's deep sky images using his 22" SDM. Most shots are stacks of just 15 second subs!
The EQ from equatorial platforms ? They look nice.
