Last night was crystal clear and cold in Canberra so I took advantage of it to do some more testing of the Pentax 200mm lens.
With the 200mm lens stopped down from F2.5 to F3 (a half stop only) I first took 4hrs 15min worth of Halpha data in 10 and 15min subs of the Tarantula region of the LMC:
130k image:
http://www.pbase.com/strongmanmike20...69298485/large
550K image:
http://www.pbase.com/strongmanmike20...98485/original
Then in the last hour before dawn I managed to get 40min worth on The Rosette before the sky got too light:
110K image:
http://www.pbase.com/strongmanmike20...69299821/large
550K image:
http://www.pbase.com/strongmanmike20...99821/original
Overall I was very happy with the evenings run. The lens is obviously quite good particularly in Halpha even with an almost wide open aperture - here is the setup:
http://www.pbase.com/strongmanmike20...69199959/large
I was using the AP for autoguiding with the SX external guide head connected to the SXV-H9 and the average errors throughout the night were < 0.1 pixels or about 0.27" - not that a 200mm lens needed this sort of accuracy of course. Having a pristene sharp star image to guide on seems to help.
Have a nice rest of the weekend
Mike