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Thanks for all the comments. But don't forget one thing these shots are all taken at F 2.8, which is as you know twice as fast as F4, four times as fast as F5.6 and eight times as fast as F8 and so on. To record this dim nebula at the same signal with F8 say would take an exposure of 8X6=48 minutes or sum (rather than average) eight exposures of six minutes each.
To record an image of a point source (ie star) depends purely on aperture size and is independant of F ratio. To record an extended source F ratio is the main consideration and is independant of focal length.
What I want do do with the 5DH is to make large moderately detailed mosaics with the 300mm lens so that all the images we see at higher magnification and detail can be seen relative to their environment.
Here a small pic of Alpha, Omega and Beta Centaurus and if you look carefully Cent A. and a shadow of a bit of tree. Also the Jewel Box.
Bert
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