Quote:
Originally Posted by Ramius
Still one question on Hyperstar. David mentioned they can be a headache. With that focal length i assume its not guiding related so what is the issue?
Bill
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Just my experience that while guiding is very much easier (often not used at all), small errors in collimation, secondary alignment, sensor tilt can be troublesome causing poor star shapes or other image defects. This will get progressively more influential the bigger you go in aperture or sensor size, and it also depends on how fussy you are for that kind of thing.
For a small 6” sct, which probably has an effective aperture similar to a 4” frac, these difficulties will be minimal, but I’m just not sure why you wouldn’t just use a short focal length frac which will give much better quality images, much simpler to set up, and probably a similar overall cost. Your mileage may vary, as they say, but just my 2c. Now once you go to an 8” sct or larger, with a Hyperstar, you’ve now got a system that (while still bringing the above challenges) a refractor will struggle to match in light gathering ability and speed. And also, you can use it at native focal length for planetary shots.