[APML] choosing a guidescope

[Craig McIntyre <craigmcintyre@optushome.com.au>]

G'day,

I have been doing wide field astrophotography for a while now (still
haven't got around to posting any images!) and am starting to look
towards prime focus on my C8. My initial attempts have all been poorly
tracked - a result of using an off axis guider, faint guide stars, and
not enough patience to guide manually. So I'm starting to think about
getting a guide scope to at least make the guiding a bit easier. A few
questions though:

1. Assuming that the guiding is spot on, am I still going to suffer
trailed images due to mirror flop on the C8? Can this be eliminated by
making sure the mount doesn't cross the meridian during an exposure? I'm
not particularly keen to go back to OAGs...

2. Shooting prime focus at 2000mm f10, what is the recommended focal
length for a guide scope? I have half an eye on an Orion 80mm f7.6
(~600mm fl) apo that could also serve as an imaging scope. Is the focal
length on this just too short for guiding a C8?

3. Is there anything else I should look for in a guidescope?

I also don't want to spent too much money on a guidescope. The Orion
above is attractive to me because it can also be used as a nice visual
instrument or for photography as well, and it's at a good price. I found
some good shots taken through it here: 
http://www.liquidfusion.com.au/astro/ed80/ed80pics.htm

Eventually I want to add an autoguider to my rig, but in the mean time
I'm guiding by a Mk1 human eyeball <g>.

Cheers,
Craig.

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