Posts Made By: Arthur Simen

I appreciate all of the useful information that Floyd and others have
provided on Astromart regarding the AT 8” RC. I received mine about
one month ago and I am reasonably happy with it so far.

I am thinking about whether to replace the focuser with a Feathertouch
FTF2015BCR focuser. A lot has been written about problems with the stock
focuser but I have not seen any direct evidence that the focuser affects
performance of the scope. On the one hand, the focuser does clearly have
flexure. When I apply torque to the drawtube the focuser feels loose. In
comparison to the William Optics Megrez 72 that I use as a guidescope the
AT focuser is somewhat looser and flexes in a clunky fashion whereas the
WO focuser flexes in a smooth and progressive fashion with increasing
torque. My camera and filter wheel (QSI 540ws) are heavy enough (just
over three pounds) to induce a small degree of sag with the drawtube
extended to achieve focus. I am not sure how much this slight sag is
affecting my images.

This leaves me wondering how much flexure is too much and how rigid is
the Feathertouch focuser in comparison to the stock focuser?

I just added a William Optics Field Flattener/Reducer III and a QSI WSG off axis guider upgrade to my AT 8” RC and QSI 540 camera. This added a few pounds to the load on the focuser (I am still using the stock focuser). I had a chance to test these new components a few days ago on IC410 and NGC281. The images show increasingly elongated stars with increasing distance from the center of the frame, but only at the top of the frame. The stars in the bottom corners are perhaps somewhat flattened (see attached). Prior to my adding the WO III and OAG the stars were much rounder throughout the frame.

Is this likely due to misalignment of the reducer/flattener due to flexure from the increased load on the focuser?

That is very nice!

I am curious as to which of the TeleVue reducers you are using. Is it
#NPR-1073 "0.8x Reducer for NP Scopes", #RFL-4087 "0.8x Reducer/Flattener for 102 Scopes", or #TRF-2008 "400-600mm 0.8x R/F"?