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Focal Reducers Starizona SCT Corrector III vs Meade f6.3

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#26 Rydeen 98

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Posted 28 March 2020 - 11:02 AM

Just to clarify completely, is that 55mm to the shoulder of the 42mm T-thread? If so, we can add another 55mm. This 55mm being the sum of about 11mm in your "T-ring" and 44mm of flange distance for Canon EOS. So a total of 110mm?



It's the full length of the adapter where it connects to the SCT threads of the focal reducer to where it threads into the t-ring. Is the sensor really that deep into the camera body? I never knew that and never accounted for it.

Edited by Rydeen 98, 28 March 2020 - 11:02 AM.


#27 Lumix.guy

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Posted 28 March 2020 - 11:26 AM

It's the full length of the adapter where it connects to the SCT threads of the focal reducer to where it threads into the t-ring. Is the sensor really that deep into the camera body? I never knew that and never accounted for it.

Yes, it really is that deep for DSLR cameras due to the reflex mirror box.  Each brand varies by a few millimeters.  Mirrorless cameras (lacking the mirror box) have a much shorter flange distance in the range of about 20mm.  My ASI1600MC-Cool camera has a flange distance of only 6.5mm!

 

T-ring back focus.jpg

 

 


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#28 UKalwayscloudy

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Posted 31 March 2020 - 03:01 AM

I’m shooting raw on the Z6 and converting to tiff to feed to DSS. Previously it was a direct conversion via Apple
Preview but now I am doing it in Lightroom with the desaturation for the flats as an intermediate step between import as Z6 raw and output as TIF.. The colour artefacts I’m referring to are not LP and have more of an annular quality.

But I’ll certainly check for an update to DSS and see
If can handle the the raw Z6 files directly and what happens if I input all the file types that way.

#29 RichA

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Posted 02 April 2020 - 01:49 AM

Yes and you can see that field of view difference in my two posted luminance images.  Since the Starizona is so sensitive to back focus distance  it is not very flexible with it's placement and f6.3 seems to be the spec for 9.25 and 11 inch scopes and 8 inch scopes will be slightly higher with Starizona claiming f6.8.  I'll have to run my image through Astrometry.net and see what my setup gives me.

 

UPDATE: Ran my image through Astrometry.net and calculated my Starizona image to be f6.9.  I also ran the Meade f6.3 reducer image which gave f5.6 meaning my back focus distance wasn't correct.  I was using the standard Meade t-adapter which I assumed had the right back focus distance.  I guess it didn't and may have contributed to some of the observed abberations. Still the Starizona produced a significantly sharper image with better details within the comparable flat field areas of the image.

Thats a major speed difference.  The Celestron is likely working as well as a more expensive unit at the same speed would do, if there is such a thing. 


Edited by RichA, 02 April 2020 - 01:51 AM.


#30 Rydeen 98

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Posted 03 April 2020 - 07:30 AM

Thats a major speed difference. The Celestron is likely working as well as a more expensive unit at the same speed would do, if there is such a thing.


I'd have to test it out at the appropriate back focus distance for a better comparison.

I've discovered something that I don't like about the Starizona. My old Canon died so I replaced it with an ASI294mc-pro. The Starizona needs a really long back focus distance of 90.3 mm. With the DSLR sensor in the back of the camera body the overall length wasn't too bad and I could image pretty close to the NCP without crashing. Now the ASI has the sensor in the front followed by the TEC housing. The whole thing sticks off my OTA by about 9 inches. It will definitely crash into the forks if I'm not careful. That's a case for using a GEM mount. I like my forks though, especially permanently mounted in my observatory.

#31 UKalwayscloudy

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Posted 04 April 2020 - 04:28 AM

The Starizona runs at 0.8 reduction on a C6. 1200mm at f/8. Which is slower but I just image for longer on a CEM40 whose payload is many times the C6 weight.  And until I got the CEM all my cameras were running into the base of the Evolution mount. Never happens now!



#32 Rydeen 98

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Posted 05 April 2020 - 05:26 PM

Despite the super long back focus, I'm still very happy with my results using the Starizona and ASI294mc pro.  I have a lot to learn using a dedicated astrocam but my first light on M42 was quite nice.  I just have to be careful not to crash into the forks.

M42

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#33 carolinaskies

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Posted 05 April 2020 - 08:47 PM

Interesting conversation and information.  

I've got the older Japan made Meade & Celestron 6.3's as well as the 3.3 Meade.  

Coming from the film days the standard 105mm distance I believe was a combination of the photo-adapter to film plane (now sensor plane with CMOS/CCD) for the Minolta SRT101 which would provide the reduction to 6.3 for the F/10.  

With so many different cameras now and sensors typically APS-C or smaller the advice by the Celestron engineers is correct. 
Trial and error imaging to find the sweet spot for your particular system. 
This can clear up many of the problems seen and should result in reasonable results.  Not saying the more expensive R/Cs arent' better, but it would be better to know you're getting the best out of what you've got already. 

The Starizona SCT III adapter is taller than the standard M&C adapters which can cause clearance issues for some fork mounted scopes.  Though i'd love to own one, for the price i'd just as soon put the money toward a RASA unless I planned extensive imaging at that focal length.  

I bought my LX200 Classic 8" 6.3 in 1997/8 so I wouldn't have to always use the reducer with my film cameras. Now I'm in the process of deforking and plan to put it on my NEQ6 for the upcoming season.  I did use the 6.3 adapter to get down th F/4 years ago, but it had issues with full frame film camera vignetting due to the small 24mm image circle. With these newer chips that won't be near the problem it was.   


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#34 chuckscap

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Posted 10 April 2020 - 10:42 AM

I have an Orange C14 with a 2" Feathertouch Crayford focuser on it.  I'm looking for high quality reducer I can use with the focuser.   Would the Alan Gee fit that bill?

 

Thanks!

 

Chuck



#35 DuncanM

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Posted 10 April 2020 - 01:48 PM

I have an Orange C14 with a 2" Feathertouch Crayford focuser on it.  I'm looking for high quality reducer I can use with the focuser.   Would the Alan Gee fit that bill?

 

Thanks!

 

Chuck

Are you doing AP? If yes then look at the Starizona SCT reducers.



#36 Lumix.guy

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Posted 14 April 2020 - 02:59 PM

I had a long discussion with Celestron tech support about this reducer Backfocus question. The figure of 105cm is the distance to the sensor if you buy the standard Celestron adapter parts for non Edge SCTs. The 105mm is also the recommended distance for the 8in Edge with reducer. That’s true but is actually not relevant to the non Edge SCTs.

If also seen recommendations on some reseller web sites suggesting 85mm with a margin of error. When I pressed Celestron on this the following emerged.

1. The 105mm is the distance at which the reducer is designed to give you try the 0.65 reduction factor. People who have plate solved on images have found that the 0.65 scale might actually be obtained somewhere very slightly different but only with variations of a handful of mm.

2. There is no guarantee that you will get optimal edge to edge image quality at 105. Celestron tech support said I should experiment with my particular config to find the best distance for IQ.

My interpretation of this is that with the product being sold as a 0.65 the 105 is what makes it give you what it says on the tin.

I just read the manual for Celestron's Radial Guider and it mentions they designed it (the Radial Guider) to provide the optimum back focus for the Celestron 6.3 Reducer/Corrector.  I measure that to be about 105mm!



#37 Astro1

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Posted 21 April 2020 - 02:45 PM

Sputnick

Like you I have converted to the ASI 294 MC pro and my initials thoughts are its great , but I use it with an original ( black tube ) C11 and whilst its great when used with the Focal reducer I also get the annoying bright ring in the centre of the image if I try and use it at the C11 's native Focal length or if I use a powermate.

Has anybody found a work around for this , I have tried different spacing form the rear of the scope but this seems to make little difference.

Attached one of my flats which clearly shows the issue.

I am guessing that the C11 Edge design has resolved this issue ?

#38 DuncanM

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Posted 21 April 2020 - 06:17 PM

I've had the Corrector III attached to my Celestron C6 for a short while and am really pleased with it. On my C6 the reduction is about 0.8 and Starizona make the different effective focal lengths clear on the web page for it. So I am on 1220mm and this looks about right. 

 

Initially, but not now, I was disappointed with the level of vignetting. It seems to me that the area of full illumination is well short of the claimed circle of illumination of 27mm diameter, but while that is true I've been able to push it a lot with flats. 

 

 

The C-6 introduces more vignetting because of it's smaller baffle tube diameter; optimal illumination will be with a C-11/C-14/Meade 10/12in which have ~55mm+ baffle tube diameters.


Edited by DuncanM, 21 April 2020 - 06:20 PM.

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#39 UKalwayscloudy

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Posted 22 April 2020 - 05:53 AM

Agreed, but with those I think the larger corrector would be the better choice.

 

The C-6 introduces more vignetting because of it's smaller baffle tube diameter; optimal illumination will be with a C-11/C-14/Meade 10/12in which have ~55mm+ baffle tube diameters.



#40 DuncanM

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Posted 22 April 2020 - 02:02 PM

Agreed, but with those I think the larger corrector would be the better choice.

With an APSC or smaller sensor the SCTIII should be sufficient. For a full frame sensor then the Starizona LF FR would be better.


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#41 gfunkernaught

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Posted 13 July 2020 - 10:56 AM

With an APSC or smaller sensor the SCTIII should be sufficient. For a full frame sensor then the Starizona LF FR would be better.


Hi I have a full frame sensor, 43mm diagonal, and I use it with my 8" SCT and the Celestron f/6.3 reducer with decent results. Would it be possible to use the large format reducer with an 8" SCT? Even if I used adapters, would the image circle still fill my sensor?

#42 gfunkernaught

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Posted 16 July 2020 - 01:40 PM

Scratch my post. Called someone at Starizona and they did some ray tracing tests and the results were poor.

#43 UKalwayscloudy

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Posted 04 May 2021 - 01:13 AM

Just thought I’d come back to this. I’ve been using my C6 with the Starizona Corrector III and have switched over to a dedicated astrocam. I’m using the Altair 26C which is aps-c and an properly correcting with flats. I’ve also worked on the OTA and have painted the inside of the baffle tube, and put it in solid tube rings ngs with a top dovetail to minimise flexure to where I have the guide scope. I am really pleased with the results I am getting now.

I’m pondering an upgrade to a C8 or 9.25, but keeping the Starizona in place. A bit more aperture to get the focal ratio down a little and the magnification up a little would help me, and the larger baffle tubes would help. Meantime here’s a C6 image with the Starizona

https://www.astrobin...feie52/?nc=user

#44 Borodog

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Posted 04 May 2021 - 10:36 AM

I know this is an old thread that's been resurrected, but looking at the original images, I don't see any curvature or or coma with the Meade reducer. I see elongation, but it's azimuthal, not radial. That points to a different issue.

 

Edit to add: In fact you can see a hint of it in the Starizona shot as well.


Edited by Borodog, 04 May 2021 - 10:38 AM.


#45 Paul AZ

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Posted 25 July 2021 - 12:41 AM

I know this is an old thread that's been resurrected, but looking at the original images, I don't see any curvature or or coma with the Meade reducer. I see elongation, but it's azimuthal, not radial. That points to a different issue.

 

Edit to add: In fact you can see a hint of it in the Starizona shot as well.

I have to agree that I don't see the added benefit considering the cost. I have been looking online to figure out what is best, Celestron f/6.3 focal reducer/corrector, Baader Alan Gee Mark II Telecompressor or the Starizona. Unless you are a pixel peeper Eyecrazy.gif, at least from my simple observations, I just can't see a difference that would prompt me to sink more money for something beyond the Celestron FR. thinking1.gif

 

I tried hard and opened the two images in separate tabs and clicked back and forth to see if anything popped out. scratchhead2.gif Aside from the darker head on the Starizona image, not much else stood out for me. I have another few days to return the Celestron, but looks like I am just going to keep it. I have 2 of them, one for each SCT so definitely more economical. waytogo.gif

 

I will admit that I myself have yet to take any photos with the Celestron FR, but I have looked though it with my CPC800 and really enjoyed the views. Once the weather improves and I have my imaging scope all set up I will see what kind of results I get. My prior images, back from 2019, were with an Meade f/12 6 inch Mak Cass with no reducer, so I expect that I should get better results with the C9.25 and the Celestron FR in less time per frame. grin.gif

 

***Well this morning I had a change of heart and I am returning 1 of the Celestron FR, only a few days left to return, and ordered the Starizona SCT Corrector IV - 0.63X Reducer / Coma Corrector from High Point Scientific. The difference in cost is about 2 dinners out so why take a chance with the Celestron FR since I have yet to test it photographically and this is a much better investment since it lasts.grin.gifwaytogo.gif


Edited by Paul AZ, 25 July 2021 - 08:28 AM.

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#46 Echolight

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Posted 25 July 2021 - 12:14 PM

Certainly the image scale in the first post is bigger with the Starizona.



#47 Brazzabeans

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Posted Today, 03:37 PM

I have to agree that I don't see the added benefit considering the cost. I have been looking online to figure out what is best, Celestron f/6.3 focal reducer/corrector, Baader Alan Gee Mark II Telecompressor or the Starizona. Unless you are a pixel peeper Eyecrazy.gif, at least from my simple observations, I just can't see a difference that would prompt me to sink more money for something beyond the Celestron FR. thinking1.gif

I tried hard and opened the two images in separate tabs and clicked back and forth to see if anything popped out. scratchhead2.gif Aside from the darker head on the Starizona image, not much else stood out for me. I have another few days to return the Celestron, but looks like I am just going to keep it. I have 2 of them, one for each SCT so definitely more economical. waytogo.gif

I will admit that I myself have yet to take any photos with the Celestron FR, but I have looked though it with my CPC800 and really enjoyed the views. Once the weather improves and I have my imaging scope all set up I will see what kind of results I get. My prior images, back from 2019, were with an Meade f/12 6 inch Mak Cass with no reducer, so I expect that I should get better results with the C9.25 and the Celestron FR in less time per frame. grin.gif

***Well this morning I had a change of heart and I am returning 1 of the Celestron FR, only a few days left to return, and ordered the Starizona SCT Corrector IV - 0.63X Reducer / Coma Corrector from High Point Scientific. The difference in cost is about 2 dinners out so why take a chance with the Celestron FR since I have yet to test it photographically and this is a much better investment since it lasts.grin.gifwaytogo.gif



#48 Brazzabeans

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Posted Today, 03:37 PM

I have to agree that I don't see the added benefit considering the cost. I have been looking online to figure out what is best, Celestron f/6.3 focal reducer/corrector, Baader Alan Gee Mark II Telecompressor or the Starizona. Unless you are a pixel peeper Eyecrazy.gif, at least from my simple observations, I just can't see a difference that would prompt me to sink more money for something beyond the Celestron FR. thinking1.gif

I tried hard and opened the two images in separate tabs and clicked back and forth to see if anything popped out. scratchhead2.gif Aside from the darker head on the Starizona image, not much else stood out for me. I have another few days to return the Celestron, but looks like I am just going to keep it. I have 2 of them, one for each SCT so definitely more economical. waytogo.gif

I will admit that I myself have yet to take any photos with the Celestron FR, but I have looked though it with my CPC800 and really enjoyed the views. Once the weather improves and I have my imaging scope all set up I will see what kind of results I get. My prior images, back from 2019, were with an Meade f/12 6 inch Mak Cass with no reducer, so I expect that I should get better results with the C9.25 and the Celestron FR in less time per frame. grin.gif

***Well this morning I had a change of heart and I am returning 1 of the Celestron FR, only a few days left to return, and ordered the Starizona SCT Corrector IV - 0.63X Reducer / Coma Corrector from High Point Scientific. The difference in cost is about 2 dinners out so why take a chance with the Celestron FR since I have yet to test it photographically and this is a much better investment since it lasts.grin.gifwaytogo.gif



#49 Brazzabeans

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Posted Today, 03:48 PM

Oops!
I’m new to this forum and wasn’t familiar with the format!
I was hoping to quote Paul AZ then ask a question!
Hopefully Paul picks up on this question?

I have owned a 12” Meade sct (lx200) for many years and use it for AP along with the other scopes I have, I also have 2 Meade 6.3fr/ff 1 of which seems to be the shorter focal length versions produced when production moved to China. I also have the Alan gee version, non of which give me satisfactory edge images with my Atik 383 sensor
Did you get your Starizona focal reducer and how does it compare?

Thanks in advance for any reply

Cheers
Bryan


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