Old 03-04-2018, 06:44 AM
garymck (Gary)
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Join Date: Aug 2005
Location: Geelong
Posts: 685
Scope Choice

I'm a bit unsure of my choice of next scope.

I have 2 scopes for wide field - an Esprit 100 and a Quattro 8"F4. However neither of these is suitable for galaxy or planetary nebula imaging. My C11, whilst a superb planetary imager and visual scope, is not a great scope for an APSC chip, even with a corrector.

I am unsure of choice of scope for smaller objects and am looking for advice.

Meteoblue says my average seeing in Geelong is around 1-1.5 arc secs, however I reckon it is worse than that, but assuming 1.5 arc secs, I'll need to image at around .5-.6 arc secs/pixel to capture detail on the mythical best night of the year.

A 12" f4 GSO truss newt will give me .82 secs/pixel with my ASI071 Pro

A 10" F8 GSO RC will give me .49 at F8, and .66 at F6

A 12 F8 GSO RC will give me .41 at F8 and .55 at F6

Which scope would be the best choice for higher resolution imaging?
Is going to 12" over 10" really worth it?

Could I image at F8 with the newt by using a barlow/powermate?

I really like how fast F4 sucks photons, but people seem to indicate that for smaller targets F ration is less important (F ratio myth?)

I was going to buy a 150mm Esprit, but figured it really didn't give me that much over my current scopes.

As an outlier, what about a Skywatcher F5 300mm newt - dirt cheap at $1400? My Mesu would easily carry it?


Last edited by garymck; 03-04-2018 at 06:58 AM.
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Old 03-04-2018, 01:33 PM
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Slawomir (Suavi)
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Join Date: Sep 2014
Location: Proserpine
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Michael Sidonio is doing VERY well with his 12" Newtonian and at 0.84"/pixel.

I feel going higher than that (less arcseconds per pixel) may be of little benefit to resolution from your location.
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