[AZ-Observing] Re: Guide Scope vs. Off-Axis Guiders and DSLR Imaging
- From: Tim Jones <tjmac@xxxxxxxxxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Mon, 3 Jan 2011 17:37:25 -0700
On Jan 3, 2011, at 4:03 PM, Jim Waters wrote:
> Would it be worthwhile to try off-axis guiders again? Would I be able to get
> enough light from the pick-off prism to guide off of? If so; what off-axis
> guider should I try?
To answer your second question first - OAGs are about the same. But then
again, many OAGs get a bad rap because of incorrect camera configuration. It's
really all about your camera setup. However, most OAGs will provide plenty of
starlight for a good guiding program (I use PHD) so long as you can get the
camera to focus.
> I am trying to reduce the overall complexity of my imaging set up and would
> like to eliminate my 70mm guide scope and any induced flexure.
Why do you believe that you're suffering from flexure? How is your guide scope
mounted onto your main scope? Are you using the simple tension screws in your
guide scope's focuser, or are you using a threaded extender?
> I am currently shooting through an 80mm ED scope and 8" f/4 scope and using a
> second scope for guiding with an Orion AutoGuider. I am concerned with
> flexure in my setup. The last time I used an off-axis guider was with my
> Meade LX200. I found it impossible to guide because my guide start looked
> like 'seagulls' and were hard to locate.
The Orion guide camera should be light weight enough so that the default
focuser pressure screws should be up to the task, but organizations like
ScopeStuff offer some very helpful extension tubes. Speaking of which, the
first thing that I recognized with my setup was the fact that getting the
cameras focused was the most under-advertised of issues in Astrophotography.
Once I got my hands on some extenders, both my main camera and my guide camera
focus properly and my life became so much simpler.
Have you tried focusing your cameras on a terrestrial object during the day -
say a street light a few blocks away? It's not infinity, but it will let you
see if you can get your camera to focus. I suspect that once you get your
guide camera to focus, you'll have fewer issues and can move forward.
HTH,
Tim
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