View Single Post
  #1  
Old 12-10-2007, 07:01 AM
iceman's Avatar
iceman (Mike)
Sir Post a Lot!

iceman is offline
 
Join Date: Sep 2004
Location: Gosford, NSW, Australia
Posts: 36,799
Question Various focal length scopes for deep space imaging

So i'm wondering what I should consider next for expanding the range of options for deep-space imaging with my 350D.

Currently:

- I have a Saxon ED80, focal length 600mm f/7.5. Good for fairly large objects or wider starfields but not so great for smaller objects, as they cover a very small area on the camera chip.
- I'm getting a WO 0.8x reducer, which will give me a focal length of 480mm and a focal ratio of f/6. Again, good for large, wide objects or wider starfields.

But what if the object is small and I want a closer view..

- I could get a 2" 2x barlow, giving me a focal length of 1200mm, but slowing the scope down to f/15.. meaning longer exposures are required.
- I could use a 2" 2x barlow in combination with the WO reducer to give me around 960mm focal length but still very slow at f/12.

So what about a newt then? A 6" or 8" newt would give me similar focal lengths (800-1000mm). The advantages include a larger aperture, and a faster focal ratio (f/5 or f/6 usually) which means I can use much shorter exposures. (and look at what Garyh and Ezystyles (Eric) do with their 6" and 10" newts!! )


Sounds all good?

I guess there are some disadvantages. I'd also need:
- An MPCC to reduce the coma,
- A set of rings/dovetail to hold it on the EQ6,
- Some sort of piggyback system for the ED80 or cheapo refractor to guide with (although I still need to do this with the ED80 on its own for guiding).

So, more cost. Probably more hassle. And do I really want to delve deeper into deep space imaging? I'm not sure yet

Anyway i'm just thinking out loud so your opinions and suggested are most welcomed.

Cheers
Reply With Quote