#15521 Jul 21, 2006
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> Reviewing some previous threads on this list as well as on other
lists > still leaves me wondering if a 20" truss RC could be managed by an
> AP1200GTO. Would appreciate hearing from anyone with direct
experience > with such a setup, thanks.
I'm using a home made 18" f/12.6 (F=5700mm) truss tube classical
cassegrain on my older AP1200GTO and am getting fine results so long
as the wind is light (~5mph) or non-existent. The telescope weighs
about 120# with full instrument load on it, possibly a tad less.
I believe that a 20" Truss tube RC such as the RCOS one would work
about as well on the mount, but both are basically approaching the
here's a recent shot from my 18"/ap1200gto:
I am getting stars in the low 2s this week with the good seeing I've
been experiencing and that is for 30 minute subexposures and guiding
is conventional (ie non-AO7) guiding.
One person mentioned to me that my star diameters were smaller and my
nebula better resolved than images of the same object taken with a
20" RCOS in Mayhill, NM and a 16" RCOS at Kitt Peak. It is too bad
those images were shot in RGB or LRGB because it make them a bit
harder to compare since narrowband filters greatly attenuate star
intensity so they have stars in their images that do not appear in
mine. Still FWHMs of stars and nebular resolution can still be
Obviously seeing usually is the deciding factor and I'd like to see
the performance of the respective systems in side by side test at the
same time in the same location. But with the limited data I have so
far I think I am 'in the hunt' so to speak.
By the way my mirror has a chip out of it about 4" square due to an
unfortunate accident a year and a half ago, but it seems to be
working well nonetheless.
I am happy with the AP1200s ability to handle my load though.