Re: [APML] Film and OAG Questions

["William R. Mattil" <wrmattil@ix.netcom.com>]

GARY HATFIELD wrote:

> Hello,
>     I bought a roll of Fuji Superia 800 and was shooting with it at a 
> festival today.  I didn't use all 36 exposures and was wondering if 
> this film is any good for astrophotography.  I've forgotten what it 
> actually said on the film cannister itself, but on the film tube it 
> came in it reads--Fuji Superia CZ135-36 800 ISO.  Just wondering if 
> it's worth my time to finish the roll under the stars or not.

Gary,

Unless its the old Fuji film it probably isn't all that great.

>     I have a Lumicon 2" Easy Guider and the (Lumicon) recommended 3X 
> Prism Diagonal.  I guide with a 10mm illuminated reticle.  I'm using a 
> 480mm f/6 80mm achromat.  My problem is not so much in finding a 
> guidestar (although that is a challenge at times), but having one 
> bright enough that I can actually see well enough to guide with, 
> without having to use averted vision.

I feel your pain here.

>   Is there a reason for using a prism instead of a star diagonal?  I 
> realize having a 3X magnification is going to make the guiding easier 
> and more accurate, but would I get brighter guide stars by using a 
> star diagonal and 2X barlow?

In my configuration the only recourse was the 3x diagonal. I did not 
have a bunch of focus range available. And I can assure you that the 3x 
diag makes it a lot easier to get good images. But a lot harder to get 
good guidestars.

>   Would I be able to focus the guidestar with this set-up?  The sky 
> here is socked in or I would try it out.  I'd appreciate any thoughts 
> or knowledge anyone might bestow upon me.


As I mentioned with the limited focus range of a Newtonian I could not. 
I used the OAG both with and without the 3x diagonal and preferred it 
with. But with a refractor things could be vastly different. I was using 
a lot more f/l too. That adds additional complexity. But I think that 
the diagonal will add too much distance and create a problem getting 
focus at the film plane.


Regards

Bill


-- 

William R. Mattil  :  http://www.celestial-images.com


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