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Equipment Discussions >> Cats & Casses

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bilgebay
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Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: Edge HD Focal Reducer new [Re: Rick R.]
      #5049249 - 02/01/12 04:54 AM

Glad to have been of help.

We are fighting with snow here so, no hope for the Lunar X this month.

Cheers


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Rick R.
journeyman


Reged: 12/05/11

Loc: center of known universe
Re: Edge HD Focal Reducer new [Re: bilgebay]
      #5054500 - 02/04/12 01:43 AM

Quote:

Glad to have been of help.

We are fighting with snow here so, no hope for the Lunar X this month.

Cheers




Hey Sedat,

We have been wishing for a little snow this season and may have a little coming, though right now the skies are very clear and observing has been great. Hang in there the skies will clear!

Thanx again.

regards,
Rick


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bilgebay
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Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: Edge HD Focal Reducer new [Re: Rick R.]
      #5938052 - 06/24/13 01:41 PM

Hi group,

It's time to bring this thread back to surface



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bilgebay
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Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: Edge HD Focal Reducer new [Re: bilgebay]
      #5938085 - 06/24/13 02:03 PM

The image on the left was shot by Jerry Lodriguss recently, using a C11 Edge scope and Canon 550D camera. He used the Edge HD 1100 Celestron reducer with 0.7x compression ratio. However, as you can see, the amount of vignetting is too much. Jerry measured this to be 33% with a linear stretch.

The image on the right was shot by me on September 2011, using a C11 Edge scope and again a Canon 550D camera. The reducer I used was the Astro-Physics CCDT67, with 0.675x compression ratio. There is much less vignetting with this reducer, Jerry found out that the vignetting was 16% after linear stretch.

While creating this side by side comparison picture I have used the Screen Transfer Function's autostretch utility in Pixinsight.

I thought this would be useful for some of you guys.

Meanwhile, now that I have sold my C11 Edge and have a new C8 Edge, I will start testing the CCDT67 reducer's compatibility with C8 Edge. If you own a C8 Edge and desperately need a reducer for your scope, please check back this space.

Several members have tried this reducer with C8 and reported negatively. With all due respect to their efforts, I want to give this glass another chance for C8 Edge scopes. I will hopefuly have some results for you early next week.

Clear skies

Sedat


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BullTerrier
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Reged: 03/09/13

Re: Edge HD Focal Reducer new [Re: bilgebay]
      #5938107 - 06/24/13 02:16 PM

A newbie here. Has anyone noticed that on the Celestron Website, there is no Focal Reducer for the 9.25 ? They sell ones for the 8, 11, 15, but there isn't one for the 9.25. Am I missing something ?

Thanks
Martin


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BullTerrier
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Reged: 03/09/13

Re: Edge HD Focal Reducer new [Re: BullTerrier]
      #5938110 - 06/24/13 02:18 PM

A newbie here. Has anyone noticed that on the Celestron Website, there is no Focal Reducer for the 9.25 ? They sell ones for the 8, 11, 15, but there isn't one for the 9.25. Am I missing something ?

Sorry, in my prior post, I forgot to include the word EDGE.
9.25 Edge


Thanks
Martin


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wolfman_4_ever
Pooh-Bah


Reged: 07/15/11

Loc: El Segundo, Ca, So. Cal
Re: Edge HD Focal Reducer new [Re: BullTerrier]
      #5938119 - 06/24/13 02:22 PM

There is no Celestron 9.25" reducer yet.


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Footbag
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Reged: 04/13/09

Loc: Scranton, PA
Re: Edge HD Focal Reducer new [Re: BullTerrier]
      #5938124 - 06/24/13 02:24 PM

Quote:

A newbie here. Has anyone noticed that on the Celestron Website, there is no Focal Reducer for the 9.25 ? They sell ones for the 8, 11, 15, but there isn't one for the 9.25. Am I missing something ?

Sorry, in my prior post, I forgot to include the word EDGE.
9.25 Edge


Thanks
Martin




That is the case for now. The 11 and 14's came out first, the 8's are shipping soon and the 9.25's will be introduced sometime in the future.


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freestar8n
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Reged: 10/12/07

Re: Edge HD Focal Reducer new [Re: bilgebay]
      #5938147 - 06/24/13 02:32 PM

Hi-

Can you do a plate solve of each image to determine the true focal reduction?

Also, are you sure the Edge reducer wasn't connected to the camera with something that acted as a choke point? The vignetting looks fairly abrupt in that image - which suggests something close to the sensor is doing the vignetting.

Frank


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bilgebay
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Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: Edge HD Focal Reducer new [Re: freestar8n]
      #5938183 - 06/24/13 02:57 PM

Hi Frank,

Here is the results for the M51 image:

*****
Iteration 4, delta = 0.966 arcsec (2.1 pixels)
Image center ...... RA: 13 29 19.315 Dec: +47 06 24.37
Resolution ........ 0.46 arcsec/pix
*****

Image Plate Solver script version 1.6
===============================================================================
Referentiation Matrix (Gnomonic projection = Matrix * Coords[x,y]):
+0.000000776898 +0.000127805018 -0.222925255323
-0.000127780650 +0.000000887374 +0.329934548791
+0.000000000000 +0.000000000000 +1.000000000000
Resolution ........ 0.460 arcsec/pix
Rotation .......... -90.379 deg
Focal ............. 1927.86 mm
Pixel size ........ 4.30 um
Field of view ..... 39' 45.0" x 26' 30.0"
Image center ...... RA: 13 29 19.315 Dec: +47 06 24.37
Image bounds:
top-left ....... RA: 13 28 00.242 Dec: +47 26 09.49
top-right ...... RA: 13 28 02.632 Dec: +46 46 24.92
bottom-left .... RA: 13 30 36.963 Dec: +47 26 20.59
bottom-right ... RA: 13 30 37.414 Dec: +46 46 35.90
===============================================================================

Edit: Corrected the camera pixel size and re-solved the plate

Edited by bilgebay (06/24/13 04:38 PM)


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bilgebay
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Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: Edge HD Focal Reducer new [Re: bilgebay]
      #5938207 - 06/24/13 03:18 PM

For some reason Pixinsight is giving me a hard time for the M13 image ??? Working on it.

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freestar8n
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Re: Edge HD Focal Reducer new [Re: bilgebay]
      #5938260 - 06/24/13 03:50 PM

Hi-

Well m51 looks very close to f/7, so it isn't a case of the spacing being too big and the f/ratio too far below f/7. One source on the web said the pixels on the 550d have a pitch of 4.3um, which is slightly different from your value but not by much - and I get f/6.88 - which should be fine I think.

On one hand I don't think there would be much impact from that vignetting after applying a flat - especially since it is way in the outer edge of the frame. But at the same time it is similar to what happened to me when I used a spacer with a dslr on an Edge 8 that was a little too narrow inside. So I hope whatever spacer he used between the reducer and the camera was wide enough on the inside and didn't itself cause vignetting.

Finally - the other main difference between reducers is just how small the stars are across the field when it is well guided. So if you have an image with ~2" stars in the center of the field, you would want to make sure they are nearly that small away from the center - independent of vignetting. You can use a flat to reduce vignetting, but it won't make the stars smaller.

Frank


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bilgebay
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Reged: 11/06/08

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Re: Edge HD Focal Reducer new [Re: freestar8n]
      #5938271 - 06/24/13 03:58 PM

OK, I give up! Pixinsight didn't like Jerry's file. I have uploaded it to dropbox, maybe you can plate solve it with something else.

Here is the link to the file. It should be downloadable shortly.


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bilgebay
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Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: Edge HD Focal Reducer new [Re: freestar8n]
      #5938295 - 06/24/13 04:13 PM

Frank you are absolutely correct regarding the pixel size. Probably I remembered some other camera's pixel size. Thanks for correcting.

I will ask Jerry about the components in his imaging train.


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freestar8n
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Re: Edge HD Focal Reducer new [Re: bilgebay]
      #5938315 - 06/24/13 04:24 PM Attachment (20 downloads)

Hi-

I was able to solve the image in Maxim and it is very similar at 0.44" per pixel. But when I debayered it and converted it to grayscale, I don't see very dramatic vignetting. Here is a graph of a diagonal line from the corner in toward the center - and it shows very little increase - which is more what I expected. So I'm not sure what's going on but it seems ok to me.

Frank


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bilgebay
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Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: Edge HD Focal Reducer new [Re: bilgebay]
      #5938316 - 06/24/13 04:24 PM

Perseverance helped this time. Here are the plate solve results for the M13 image

Image Plate Solver script version 1.6
===============================================================================
Referentiation Matrix (Gnomonic projection = Matrix * Coords[x,y]):
-0.000122811693 +0.000009493992 +0.302979127650
-0.000009533706 -0.000122880945 +0.237701263605
+0.000000000000 +0.000000000000 +1.000000000000
Resolution ........ 0.444 arcsec/pix
Rotation .......... -4.444 deg
Focal ............. 1999.54 mm
Pixel size ........ 4.30 um
Field of view ..... 38' 27.5" x 25' 37.0"
Image center ...... RA: 16 41 40.973 Dec: +36 28 58.52
Image bounds:
top-left ....... RA: 16 43 11.689 Dec: +36 43 12.04
top-right ...... RA: 16 40 00.472 Dec: +36 40 13.02
bottom-left .... RA: 16 43 20.987 Dec: +36 17 38.78
bottom-right ... RA: 16 40 10.811 Dec: +36 14 40.73
===============================================================================


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bilgebay
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Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: Edge HD Focal Reducer new [Re: bilgebay]
      #5938325 - 06/24/13 04:30 PM

OK, here is the M51 sub for you, again uploaded to dropbox. Can you please analyse that as well ?

This will help all the C11 Edge users for sure.

Thank you for your contribution Frank.

Edited by bilgebay (06/24/13 04:37 PM)


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freestar8n
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Re: Edge HD Focal Reducer new [Re: bilgebay]
      #5938333 - 06/24/13 04:33 PM

Hi-

I'd be happy to look at it - but I think you need to fix the link you provided for m51.

Thanks,
Frank


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bilgebay
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Reged: 11/06/08

Loc: Turkiye - Istanbul and Marmari...
Re: Edge HD Focal Reducer new [Re: freestar8n]
      #5938341 - 06/24/13 04:37 PM

Oooop! Should be OK now.

Thanks


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freestar8n
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Re: Edge HD Focal Reducer new [Re: bilgebay]
      #5938361 - 06/24/13 04:51 PM Attachment (15 downloads)

Ok - I get 0.46"/pixel which is very similar, and I see little vignetting. I can't tell the exact percentage without having bias frames to subtract, so that I know where the "zero" is. But both images appear to be dominated by skyglow so I don't think it matters much and there is just gradual vignetting toward the corners - which is what I expected with that size sensor.

So - they both seem ok to me in terms of vignetting.

Frank


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