Quote:
Originally Posted by The_bluester
I have been really considering a RASA 8" to pair with my ASI294, the focal length is more or less the same as my little ED72 so about the same FOV and the 72mm does do pretty well and with enough subs the undersampling can be fairly well recovered using drizzle processing. I don't imagine the RASA being any different in that regard. but at F2 I could do in under 2 minute subs what I am getting out of the 72mm in 5 minute subs. It would make it possible to get in single good night the equivalent integration wise of around ten hours exposure time that I am doing now!
What has stopped me so far (Aside from finances) is not having found a great number of images yet without significant "Issues" Tilt and Focus being the most obvious. At F2 I wouldn't consider one without motorised focus, and also with the small critical focus zone that F2 implies I imagine they will be very, very sensitive to sensor tilt issues.
I have recently found a couple of images on astrobin that indicate those issues can be conquered and I am still pretty tempted. People are doing NB with them too with the ASI1600 and a now available modified filter drawer to enable quick filter changes, but flat frames are an issue as dust bunnies would change with every filter change. I think if you had an obs and a list of targets you could get around that for automated imaging by shooting a number of targets in a night with a single filter so you can shoot and apply one set of flats to the whole night, then change filters for the next night and go again. It is either that or no flat frames, or sitting up with it changing filters and shooting flats all night!
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The faster the scope the more sensitive to sensor tilt seems to be true.
I don't think simply changing the filters would render your flats invalid.
A filter wheel does just that anyway. A lot of the dust bunnies are from dust on the sensor glass not the filters.
200mm aperture is pretty tempting if it can be managed with the right camera. Perhaps one shot colour is the go and a light pollution filter if its being used in a light polluted area and stick to the brighter objects of which there are quite a few.