Friday, April 1, 2011
I'm pleased to report that, overall, I found the reducer to produce very satisfying images, resulting in a reduction factor of 0.69x. See http://www.pbase.com/wjshaheen/optec_lepus_062x_focal_reducer_testing for full scale test images as well as an f/10 baseline image.
Update 24-Apr-2011: I resumed testing after resolving several issues having to do with the baseline - i.e., SCT collimation, guide-camera flexure and focuser flexure (yes, the Feather Touch focuser resulted in a slight drift, which was not mirror shift).
Visit http://www.pbase.com/wjshaheen/optec_lepus_062x_focal_reducer_testing and see the 4 images of M57 (Ring Nebula) taken this date - on the bottom row.
Some coma is noticeable in the lower left corner only and may be due to a tilted plane, which itself may be the result of, again, the leading edge of the reducer stopping at the edge of the internal field flattener. This is being researched with the vendor.
On another note, I have a professional source whose contact at Celestron indicates they will be releasing a reducer this summer. It will have a respectable back-focus (90 to 110 mm) but may not have the coverage originally desired. It will however cover an APS size chip and certainly the 8300.
Update on the question of the reducer possibly not seating squarely (the leading edge of the reducer stopping at the edge of the internal field flattener), I just received word from Optec that they "have developed a different mounting configuration for the Edge HD scopes. For the C11 HD and C9.25 HD scopes a spacer is required to keep the lens housing from touching the Edge HD retaining ring." . (At the time I ordered mine from OPT, they had the former version in stock.)
Optec is sending me the new lens and housing gratis and I will be testing it in about a week.
As an aside, I've replaced the ST-8300M with a QSI-583wsg - solves a host of flexure issues up and down the imaging train as well as with any mirror flop or guidescope flexure. The Starlight Xpress Lodestar connects easily to the QSI's guideport, given the standard C-mount adapter) and so far I've had no problem locating a guidestar.
Here's the image from 3/28/2011 (prior to collimating):
This is from last night (after collimating):
(Feel free to explore the Original sizes.)
And, here is the side-by-side comparison:
Further, here's an excellent paper on how to collimate:
I for one will never sell collimation short again.
Bill I have to admit I've frequently given collimation (aligning the optics of a telescope) the short-shrift in my haste to produce an image. But, after examining the NGC3628 photos taken lately and some visual viewing the other night, I took another set of images after doing a "proper" collimation.*