Quote:
Originally posted by ving
my aperture mask is 80mm bringing mine to f15. it fits nicely in between the spdier vains so there is no obstruction. I always use it for my doubles, planets and moon observing as it gives better contrast on bright objects
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Something not quite right with your scope if thats the case. If we were talking Andrews 20" which uses a 7" off axis mask I would agree as the 7" unobstructed aperture has plenty of resolving power and will cut through the seeing a lot better than 20" of aperture if the seeing is poor. With an 8" scope full aperture should beat the masked view almost all the time.
Maybe your scope is not quite collimated correctly ? Are you using just a laser to collimate ? If not how are you collimating it? Have you centred the secondary under the focuser and squared the focuser to the optical axis ?
Have you star tested the scope ? What is the star test like ? Is any astigmatism present, the GS scopes are notorius for having overtight secondary holders which introduce astigmatism and this will affect your full aperture views.
I would be looking for another solution to the problem than an off-axis mask with an 8" scope.
CS- John B