I'm using my 600mm ED80 for imaging with DSLR mounted on it. Was recommended this because it has a bigger aperture and I know it's a very popular and highly recommended scope for widefield imaging. So I have used my 900mm ED100 with SPC900NC webcam and PHD for guiding. I've only been able to attempt this setup a couple of outings due to weather.
I
was having trouble keeping the guide star in the box on PHD initially. Did a much better alignment last time, and actually did get some decent exposures, but in PHD the star was constantly moving outside the guide "box" and the application was beeping and flashing while it tried to get it back on track.
I am sufficiently inexperienced to know if this is normal or not, but last night I was thinking that it could be that 900mm is too long a focal length and the stars are moving too much, even more than the imaging scope (600mm).
On one hand this could be a good thing. Means that PHD Guiding will be much more sensitive to movement and the resulting images in my DSLR should be better for it.
On the down side, not sure if it's due to the smaller aperture or the narrower field of view, but seems hard to actually find guide stars in the PHD window.
I was thinking that perhaps a wider guide scope with bigger aperture might show more potential guide stars. Something like
this Orion ShortTube 80 Guide Scope I saw for AU$259.
What is your opinion? Should I get this guide scope, or keep using the ED100? If I get it, should I keep the ED100 or sell it to pay for the guide scope? I do intend to get something like a 9.25" reflector in the future.