Edge HD Focal Reducer
Posted 19 July 2010 - 07:36 AM
I find it hard to believe that they came out with a scope that is "almost" perfect for imaging but is restricted to f/10mm-f/11mm.
Posted 19 July 2010 - 07:52 AM
I used the Siebert Optics Galaxy Viewer, a 6.3 focal reducer for binoviewers, in my Tele Vue Bino Vue. Also, I use the focal reducer setting in my Siebert 5 position Power Mag Wheel, as well as the focal reducer setting in my EarthWin system with no problem, but then I'm strictly visual. I used the EarthWin reducer setting with single eyepeices, also. I have not tried a conventional screw-into-the-visual-back FR.
Posted 19 July 2010 - 08:19 AM
It's good to hear that you are able to use regular FR's for visual use with your Edge HD. There is hope.
Posted 19 July 2010 - 09:08 AM
Posted 19 July 2010 - 11:12 AM
reducer (which does not have a built-in flattener), and
found that it had serious edge correction issues with my
9.25" EdgeHD. I used it as AP intended it, with their
SCT adapter. Celetron recommends 5.25" spacing between
the Schott flattener and the chip of a CCD or DSLR. How
that would translate to the use of a reducer with it, I'm
not sure. What I do know, and have posted proof of in
another thread, is that varying the spacing creates real
edge correction problems (it also changes the spherical
correction visually, much more that the same spacing change
would on a non-EdgeHD Celestron).
I've got a feeling that trying to use a focal reducer in
conjunction with a field flattener is creating fits for the
optical designers at Celestron, which is why we have not
seen one yet. At this point, anyone wanting to do SCT
imaging at anything other than F/2 (with HyperStar) or
native F/10 with the EdgeHD, would be better served using
a standard SCT with a reducer/corrector. It appears to be
more than just an issue of having a reducer that does no
field-flattening. In theory, a properly spaced reducer with
no field-flattening properties should work with the EdgeHD
flattener, but if that was all there was to it, I would
expect Celestron would have one available already. It may
be that a specially designed reducer may be needed (which
may even mean a specially designed unit for each size
Posted 19 July 2010 - 11:18 AM
I wish I could use my DSLR with the Hyperstar/9.25" HD but I have a feeling that I wont be able to.
Posted 19 July 2010 - 02:44 PM
won't be too heavy for it, and the obstruction of the
camera will not pose an issue. I got this from Dean at
Starizona. It will work with Hyperstar and the DSLR when
it comes out for the 9.25" (none available now) later in
Posted 19 July 2010 - 02:58 PM
Posted 19 July 2010 - 05:27 PM
Celestron has virtually nothing to do with the Hyperstar product, this is all Starizona's game. Celestron talks up the concept of fastar and makes scopes with fastar compatible secondonaries, that's about the extent of it.
Posted 20 July 2010 - 04:00 PM
Posted 21 July 2010 - 05:16 PM
Posted 21 July 2010 - 06:38 PM
They are f/6.2mm focal reducers in the Lepus Series:
"Lepus 0.62X Telecompressor Lens
New 4-element telecompressor for use with new well-corrected SCT designs including the Meade ACF and Celestron EdgeHD optical tube assemblies. With a longer back-focus over 100mm, the Lepus 0.62X is capable of fully illuminating a 22mm diagonal CCD. Can be used with any filter wheel/camera combinations with room to spare and can also be used with DSLR cameras. Optimal back focus distance is maintained by new Lepus line of camera mounts. Contact Optec for camera-specific mount."
They sell for $199.00 and need a specific camera mount that sells for $95.00. Part #19407. They are listed on Optec's price list but no information yet on the website.
Here are two pictures that he sent me.
The back end of an 11" Edge HD with the FR and camera mount:
A shot taken with that setup without flat fields:
Jeff is going to send me a processed image when the processing is complete.
This looks promising.
Posted 21 July 2010 - 07:04 PM
Posted 21 July 2010 - 08:03 PM
Posted 22 July 2010 - 03:26 PM
AIUI the ACF is coma free but has a curved focal plane while the ED is both coma free and has a flat focal plane.
How can one FR correct for the curved focal plane in one case and the flat focal plane in the other?
Posted 23 July 2010 - 07:11 AM
Posted 23 July 2010 - 10:22 AM
The only reason the flat was not applied was simply that I forgot it until after I had switched to f/10 for a comparison shot. Jeff did ask me to apply a flat that I got through nearly-identical setup the following weekend, which I did, and it did a nice job of eliminating the lighter center. I am at work now or I would post that shot, if I can remember after getting home I will do so. Jeff does have that shot now also.
Overall, I have been quite happy with the image quality using Optec's FR. Next up is to try the same thing all over again using their TCF-Si focuser, which is being delivered today!
Here's hoping the Ohio skies cooperate over the next few weeks...
-- Pat Freeman
Posted 23 July 2010 - 10:57 AM
Looking forward to having you as another active participant!
clear enough skies
Posted 23 July 2010 - 02:17 PM
Posted 23 July 2010 - 02:56 PM