Quote:
Originally Posted by David Fitz-Henr
A fabulous image Marc! You would probably need a mosaic of 6 panels if you were to image at the standard C11 f/10 ratio in order to cover the same field of view! It must be extremely challenging to hold collimation at f/1.8 as well; I would imagine that you may need to re-collimate periodically as the scope tracks the same object across the sky?
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Thanks David.

Yeah the C11 is pretty useless at prime unless you like narrowfield 'a la Fred'

. I like widefield and this is like a super lens. Just a 25kg one... Retaining collimation will be a challenge over time I suspect. Although in one imaging session once the mirror is locked, focus shift through the CF parts is very minimal. The orginal body would contract in the cold within half an hour. I'm already working on a better system to tilt the primary so I can do it in the dark as often as possible.
Quote:
Originally Posted by dvj
I have never seen a decent image done with the Hyperstar system. This one is excellent! With such fast f-ratio, extremely fine adjustments are needed for collimation and or tip-tilt. You are very close indeed. I also like this image scale. Well done.
jg
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Thanks John.

There are some pretty cool Hyperstar shots on the web but you've got to dig them out. Mostly in your neck of the woods.
It's a demanding rig and a big learning curve but it's fun to use. What I like most is viewing faint stuff in a 5s focusing run (even through a dense Ha filter) to center the targets. It gathers an insane amount of light in such a short time. It's also pretty forgiving on guiding with the QHY9 on an image scale of 2.21 arc seconds per pixel. The field is uncropped 2.1 x 1.5 degrees. You'd get the same on any typical 5-6" F/5 system.
SCT have very good resolution on axis but a field curvature like a salad bowl and a very small usable imaging circle. The Hyperstar field although not perfect is somehow flatter. The main advantage is that data acquisition is very very fast. Imaging sessions can be very productive if like me you can live with
good enough as just that.