Quote:
Originally Posted by Dennis
Hi Mike
Thanks for the nice words of encouragement!
I’d like to think it is the artistic side in me, following the proportions of the Golden Mean to create the perfectly balanced composition but alas, you’ve hit the nail on the head, it’s the size of the TC211 guide chip, a paltry 192x164 pixels that tends to dictate where the target will appear on the main chip. 
I did get to use Gerald’s SBIG ST4000XCM on the last evening at the Qld Astrofest and I was absolutely spoiled with the ST237-sized 640x480 guide chip! 
I have tried my hand at off-axis guiding but at focal lengths of over 1500mm, I haven’t been too successful yet, with maybe 1/3 of the frames showing signs of slight elongation, so I would need to do some more analysis and work to chase this down. 
In the meantime, I quite happy poodling along with the ST7 and learning how to process mono data before I join you big boys in the rarefied, stratospheric realms of megapixel LRGB imaging, with it’s plethora of challenges to overcome; the sheer expense being one major hurdle right now. 
Cheers
Dennis |
Funnily enough I have rarely been aware of any issues with piggyback guiding. Whether with my 600mm FL ED80, 1500mm+ FL 12" LX200GPS (fork mounted!) or the 1140mm FL AP on the laser guided NJP
I have done nothing but piggyback guiding. Of course I have rarely gone over 10min exposures so perhaps at 2000mm+ FL and over 10min exposures there may indeed be an issue with differential flexure but still, I think self guide is waaaaaay overated. The vast majority of high end users don't self guide anyway for exactly the reasons you are finding. I use a rather sensitive SXV-h9 which has a good sized chip for guiding (9mm X 6.7mm) and I have NEVER had to move the guide scope to find a guide star..?
Have you tried piggyback guiding?
Mike