Quote:
Originally Posted by AlexN
It all added up to a very nice image thats for sure Dennis.. I must say the ST7 did a very good job at F/19. The sensitivity of the ST7 over your 40D would have been a big help! It would be very interesting to see the results from the 40D on a bright nebula... Something like the Tarantula core, or M20. I would think that
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Hi Alex
Ahh, yes, the bliss of cooled, sensitive sensors!
I’m still in an auto guiding daze at the moment! Previously I had been struggling with side by side auto guiding at focal lengths of over 1500mm, using the WO 66mm Petzval as the guide scope. Now it seems, I may be able to auto guide at 3450mm for 10 mins although it’s early days yet and I need to consolidate everything to make sure that the systems “new” behaviour hasn’t just been a lucky fluke.
Over the months of experimenting and trials, I made the following changes to my side by side set up:
Imaging ‘scope:- Removed brass compression ring in Moonlite focuser as it tended to seat just on the edge of the safety undercuts on my various 2” adapters.
- Increased the number of clipping points on the mount and side by side plate to better route all my cables to minimise drag
Guide scope:- Drilled side by side plate to mount the 3 point adjustable guide rings closer to the imaging ‘scope.
- Increased separation between guide rings – one close to lens cell, the other almost on the focuser.
- Removed all focus tube extenders from guide scope.
- Replaced grub screw based adapter with a Baader 1 ¼” rotating clamp adapter.
- Fitted a WO 1.25” diagonal to reduce cantilever at focuser.
In addition:- I went through the entire system and checked all nuts, bolts, fasteners, etc and at one stage noticed that my Moonlite focuser had some slight rotational play, having worked loose over the years.
- I keep the system slightly heavy against the direction of the RA drive and carefully balance the system before each session.
- Adjusted backlash in RA axis.
- I also tweaked the parameters in PHD Guiding, reducing guide corrections to 50% to minimise the potential for over correcting.
All in all, it has been quite a herculean endeavour as I somewhat simplistically though that just owning an EM200 conferred upon me the right to obtain round stars, straight out-of-the-box!
Cheers
Dennis