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Equipment Discussions >> Cats & Casses

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Jeff Smith
professor emeritus


Reged: 04/06/10

Loc: Chicago
Edge HD Focal Reducer
      #3930821 - 07/19/10 08:36 AM

Any tried any focal reducers with their Celestron Edge HD's? I know Celestron is planning on coming out with a dedicated FR but has anybody tried using one of theirs? Would a screw-in FR work?
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.


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Fred1
Carpal Tunnel
*****

Reged: 09/19/07

Loc: Somewhere in the Orion Spur
Re: Edge HD Focal Reducer new [Re: Jeff Smith]
      #3930836 - 07/19/10 08:52 AM

Actually, it's Fastar compatible, so it's not restricted to f10 as the Fastar configures for f2.

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.


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Jeff Smith
professor emeritus


Reged: 04/06/10

Loc: Chicago
Re: Edge HD Focal Reducer new [Re: Fred1]
      #3930859 - 07/19/10 09:19 AM

I have a 9.25" Edge HD and a Canon 450D. Celestron does not suggest using a DSLR for their Fastar scopes under 11" so I am probably out of luck there.
It's good to hear that you are able to use regular FR's for visual use with your Edge HD. There is hope.

Edited by Jeff Smith (07/19/10 09:20 AM)


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Starhawk
Space Ranger
*****

Reged: 09/16/08

Loc: Tucson, Arizona
Re: Edge HD Focal Reducer new [Re: Jeff Smith]
      #3930926 - 07/19/10 10:08 AM

Talk to Starizona. Celestron doesn't make any optics to go on a fastar interface anymore.

-Rich


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Jeff Smith
professor emeritus


Reged: 04/06/10

Loc: Chicago
Re: Edge HD Focal Reducer new [Re: Starhawk]
      #3930943 - 07/19/10 10:15 AM

Rich, I'm not looking for a Fastar setup. I was looking at an Optec reducer. It does not have a flattener built in so I was wondering if it would work with a 9.25" Edge HD. http://www.optcorp.com/product.aspx?pid=105-172-173-10164

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Thomas A Davis
Pooh-Bah


Reged: 03/25/05

Re: Edge HD Focal Reducer new [Re: Jeff Smith]
      #3931150 - 07/19/10 12:12 PM

I think the real issue is spacing. I tried the AP .75X
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
EdgeHD SCT).

Tom


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Jeff Smith
professor emeritus


Reged: 04/06/10

Loc: Chicago
Re: Edge HD Focal Reducer new [Re: Thomas A Davis]
      #3931162 - 07/19/10 12:18 PM

Good points. I would have thought that a focal reducer with no correction of any kind would work if the astronomer was able to get the camera the proper distance from the back of the scope. I have read that Celestron will have different sizes of FR's when they come out.
I wish I could use my DSLR with the Hyperstar/9.25" HD but I have a feeling that I wont be able to.

Edited by Jeff Smith (07/19/10 12:19 PM)


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Thomas A Davis
Pooh-Bah


Reged: 03/25/05

Re: Edge HD Focal Reducer new [Re: Jeff Smith]
      #3931588 - 07/19/10 03:44 PM

I wouldn't worry about using a DSLR with the 9.25". It
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
the year.

Tom


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Jeff Smith
professor emeritus


Reged: 04/06/10

Loc: Chicago
Re: Edge HD Focal Reducer new [Re: Thomas A Davis]
      #3931613 - 07/19/10 03:58 PM

That's good news. I wan't worried about weight really. I was under the impression that Celestron and Starizona did not suggest using a DSLR with Fastar/Hyperstar on a scope under 11".

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mclewis1
Thread Killer
*****

Reged: 02/25/06

Loc: New Brunswick, Canada
Re: Edge HD Focal Reducer new [Re: Jeff Smith]
      #3931861 - 07/19/10 06:27 PM

That's because currently the only product under the C11 Hyperstar is the C8 Hyperstar, and DSLRs (even the small ones) are quite large compared to the C8 secondary.

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.


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Jeff Smith
professor emeritus


Reged: 04/06/10

Loc: Chicago
Re: Edge HD Focal Reducer new [Re: mclewis1]
      #3933796 - 07/20/10 05:00 PM

Makes sense. We'll see what Starizona comes up with for the 9.25". I'm not sure I want to spend that kind of money though. I would rather use a focal reducer in the back of the scope. It's tough imaging at f/10mm for me. I was hoping someone had tried out one of thier existing FR's and found it to work with the Edge HD.

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Jeff Smith
professor emeritus


Reged: 04/06/10

Loc: Chicago
Re: Edge HD Focal Reducer new [Re: Jeff Smith]
      #3935423 - 07/21/10 12:47 PM

I am going to call Optic about this: http://www.optecinc.com/astronomy/nguw_070.htm

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ewave
Pooh-Bah
*****

Reged: 05/16/09

Loc: northwest NJ
Re: Edge HD Focal Reducer new [Re: Jeff Smith]
      #3936023 - 07/21/10 06:16 PM

Optec mostly for CCD chips no bigger than 18mm, too small for SLRs

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Jeff Smith
professor emeritus


Reged: 04/06/10

Loc: Chicago
Re: Edge HD Focal Reducer new [Re: ewave]
      #3936128 - 07/21/10 07:38 PM

Actually, I talked to Jeff Dickerman at Optec and had a great conversation with him about this. They now make a FR specifically for the Celestron Edge HD and Meade ACF series.
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.


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ewave
Pooh-Bah
*****

Reged: 05/16/09

Loc: northwest NJ
Re: Edge HD Focal Reducer new [Re: Jeff Smith]
      #3936167 - 07/21/10 08:04 PM

Hope so....it looks close to the recommended 5.25 inches from schott lens to camera sensor. Still for CPSC sized sensors, it is about a 27mm light cone.

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Jeff Smith
professor emeritus


Reged: 04/06/10

Loc: Chicago
Re: Edge HD Focal Reducer new [Re: ewave]
      #3936262 - 07/21/10 09:03 PM

Jeff told me that it would be at 22mm for my DSLR but he also said that flats would be necessary based on the pics he has seen.

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Chris Rowland
professor emeritus


Reged: 02/28/05

Re: Edge HD Focal Reducer new [Re: Jeff Smith]
      #3937794 - 07/22/10 04:26 PM

What puzzles me about the Optec FR is how it can be OK for both the ACF and ED scopes.

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?

Chris


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bradisback
member


Reged: 01/05/10

Re: Edge HD Focal Reducer new [Re: Chris Rowland]
      #3938815 - 07/23/10 05:10 AM

+1 Chris

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Jeff Smith
professor emeritus


Reged: 04/06/10

Loc: Chicago
Re: Edge HD Focal Reducer [Re: bradisback]
      #3938923 - 07/23/10 08:11 AM

Good point. I may call Jeff back later today and get a clarification.

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bradisback
member


Reged: 01/05/10

Re: Edge HD Focal Reducer [Re: Jeff Smith]
      #3939005 - 07/23/10 09:13 AM

It would be nice!!

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