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Focal Reducers Starizona SCT Corrector III vs Meade f6.3

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#1 Rydeen 98

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Posted 29 January 2020 - 05:21 PM

I recently acquired a Starizona SCT corrector III for my 8 inch LX200 Classic EMC.  I was kind of getting the itch to upgrade to a CPC0800 Deluxe HD but then I ready many comments suggesting that the Starizona focal reducer could get a standard SCT pretty close to the Edge HD and ACF optics.   Well, despite the positive reviews I didn't find a lot of images.  So here's my unscientific test between the Starizona and the Meade f6.3 reducer.  I've attached two luminance images, one for each of the focal reducers and my final image which is definitely one of my best since starting this hobby.   The two luminance images were just given an ABE and STF Autostretch in PixInsight.   I'm definitely happy with the Starizona.  The field curvature and coma issues are nearly gone.  No more need to crop my APS-C images (well except in the case of subs that don't overlay perfectly over multiple sessions.)

 

Meade made in China f6.3 Focal Reducer/Field Flattener

Meade Lum

 

Starizona SCT Corrector III

Starizona Lum
 
I'm particularly proud of the dark nebulosity I managed to capture in the finished image which I took over the course of two nights.  This is approximately 5 hours integration with a Canon T3i Full Spectrum camera at ISO 800.

 

Finished image with Starizona Corrector

Horsehead Nebula

 


Edited by Rydeen 98, 29 January 2020 - 06:08 PM.

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#2 junomike

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Posted 29 January 2020 - 05:46 PM

Looks like you get what you pay for although the Meade does a great job considering the price.



#3 Rydeen 98

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Posted 29 January 2020 - 05:55 PM

Looks like you get what you pay for although the Meade does a great job considering the price.

Agreed. The Meade was like $80 when I got it and the Starizona is $399 plus $60 for the camera adapter plus another $25 if you don't already have a 2 inch visual back.  It did satiate my appetite for a $3000 telescope upgrade though.


Edited by Rydeen 98, 29 January 2020 - 06:06 PM.


#4 Eddgie

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Posted 29 January 2020 - 06:11 PM

About 15 years ago, Roland Christen designed a corrector for Baader. It is called the Alan Glee.

 

This corrector made a standard C8 into an f/5.9 system with very good coverage over a 35mm frame. 

 

I am surprised that more people never used it.   

 

 

 

Imaging Use:  Of course, the Alan Gee Telecompressor Mark II also delivers the ultimate photographic image.  Whether for film or CCD imaging, this telecompressor will produce a sharp, flat field, with the minimum vignetting possible. Coverage for 35mm photography is superb, delivering the sharpest wide-field images possible from your SCT.   

The Alan Glee even mounted up in the baffle the way the EdgeHD optics corrector does.  Hmmmmm. 

 

 

Anyway, happy the Starizona works well!  That is the most important thing.


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#5 Rydeen 98

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Posted 29 January 2020 - 06:51 PM

About 15 years ago, Roland Christen designed a corrector for Baader. It is called the Alan Glee.

 

This corrector made a standard C8 into an f/5.9 system with very good coverage over a 35mm frame. 

 

I am surprised that more people never used it.   

 

 

The Alan Glee even mounted up in the baffle the way the EdgeHD optics corrector does.  Hmmmmm. 

 

 

Anyway, happy the Starizona works well!  That is the most important thing.

I did come across posts regarding that FR.  Seems like another good option but being mounted inside the baffle, it would not be easily removable right?  I still do like to work at f10 for the small targets.  I shot Stephan's Quintet this past summer.  I'm definitely into a wide variety of field of views.



#6 tjz

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Posted 29 January 2020 - 10:40 PM

I finally got fed up with the lousy results from my Celestron f/6.3 reducer and got a Starizona SCT III. It sure is a pricey piece of glass, but seems well made. I've not done a lot of side-by-side comparison, but I can say I am very pleased with the better stars I get from the SCT III now. One thing to note is that plate solving shows the SCT III to be closer to an f/7.2 reduction on my Celestron C8, so you won't get quite as wide a field as with the Celestron/Meade ones at f/6.3. But I'll take the round stars any day over the slightly narrower field of view and slower optics.

 

Clear skies!


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#7 Rydeen 98

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Posted 30 January 2020 - 07:25 AM

I finally got fed up with the lousy results from my Celestron f/6.3 reducer and got a Starizona SCT III. It sure is a pricey piece of glass, but seems well made. I've not done a lot of side-by-side comparison, but I can say I am very pleased with the better stars I get from the SCT III now. One thing to note is that plate solving shows the SCT III to be closer to an f/7.2 reduction on my Celestron C8, so you won't get quite as wide a field as with the Celestron/Meade ones at f/6.3. But I'll take the round stars any day over the slightly narrower field of view and slower optics.

 

Clear skies!

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.


Edited by Rydeen 98, 30 January 2020 - 09:24 AM.


#8 charlesgeiger

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Posted 31 January 2020 - 08:37 PM

Can one use the Alan Gee or the Starizona III for visual?  And will the Alan Gee fit the baffle tube of the C11 correctly?

Charlie 



#9 Rydeen 98

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Posted 01 February 2020 - 12:31 AM

Can one use the Alan Gee or the Starizona III for visual? And will the Alan Gee fit the baffle tube of the C11 correctly?
Charlie

From what I've read, the Starizona is more for imaging because of its very limited back focus tolerance. The Alan Gee seems to be good for both. I will still keep my Meade 6.3 reducer around as it was just fine for visual. When I'm doing visual it's mostly at the native f10 or Barlowed even higher so I wouldn't even use a FR.

Edited by Rydeen 98, 01 February 2020 - 09:48 AM.


#10 Traveler

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Posted 01 February 2020 - 02:36 AM

Looks like you get what you pay for although the Meade does a great job considering the price.

+1 



#11 George N

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Posted 01 February 2020 - 03:08 PM

Can one use the Alan Gee or the Starizona III for visual?  And will the Alan Gee fit the baffle tube of the C11 correctly?

Charlie 

I don't know about the Starizona lens -- but I just downloaded the manual for the Alan Gee - and it says that a 2-inch diagonal and 2-inch eyepieces would work better than using the Gee. They do however recommend it for use with certain binoviewers - that allow connecting the Gee right to the binoviewer.

 

However - in a very recent answer to a Q&A on their website Baader says they are working on a new version of the Alan Gee that is designed to be easier to use with 2-inch focuser or their 2-inch click-lock 'visual back' part for Celestron SCTs. They hope to have it for sale Spring 2020. I take it that the lens will be the same, while the new unit will have a different cell setup.

 

I'm looking for various 'solutions' for deep sky imaging with my new non-edge C9.25. I have both a DSLR and 6303e chip CCD. The Gee manual recommends not using a sensor larger than APS -- so that seems to rule-out my CCD camera, or one of the new Canon mirrorless astro cameras.



#12 ChrisGTS

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Posted 03 February 2020 - 03:47 PM

I have a related question. With my Celestron 6.3 reducer, it produces a very pronounced bright spot in the center of the field of view (when the histogram is stretched), which can be resolved with some effort in processing, but which is very annoying during live stacking. Is the Starizona corrector better in terms of field illumination being more even?

(I am using an ASI294 MC-Pro)


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#13 Rydeen 98

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Posted 03 February 2020 - 09:38 PM

I have a related question. With my Celestron 6.3 reducer, it produces a very pronounced bright spot in the center of the field of view (when the histogram is stretched), which can be resolved with some effort in processing, but which is very annoying during live stacking. Is the Starizona corrector better in terms of field illumination being more even?
(I am using an ASI294 MC-Pro)


I'm not sure about that bright spot as I've not observed that with my Meade. The Meade and Celestron look identical and are probably just rebranded from the same Chinese manufacturer (I don't know this for sure but it wouldn't surprise me). The Starizona spec is a 27 mm imaging circle suitable for up to APS-C sensors. I don't see any uneven illumination.

#14 DuncanM

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Posted 04 February 2020 - 01:13 AM

I recently acquired a Starizona SCT corrector III for my 8 inch LX200 Classic EMC.  I was kind of getting the itch to upgrade to a CPC0800 Deluxe HD but then I ready many comments suggesting that the Starizona focal reducer could get a standard SCT pretty close to the Edge HD and ACF optics.   Well, despite the positive reviews I didn't find a lot of images.  So here's my unscientific test between the Starizona and the Meade f6.3 reducer.  I've attached two luminance images, one for each of the focal reducers and my final image which is definitely one of my best since starting this hobby.   The two luminance images were just given an ABE and STF Autostretch in PixInsight.   I'm definitely happy with the Starizona.  The field curvature and coma issues are nearly gone.  No more need to crop my APS-C images (well except in the case of subs that don't overlay perfectly over multiple sessions.)

 

Meade made in China f6.3 Focal Reducer/Field Flattener

 

 

Starizona SCT Corrector III

 
 
I'm particularly proud of the dark nebulosity I managed to capture in the finished image which I took over the course of two nights.  This is approximately 5 hours integration with a Canon T3i Full Spectrum camera at ISO 800.

 

Finished image with Starizona Corrector

Hi. I think you need to change the permissions to allow viewing the full sized images in your CN photo gallery.



#15 Rydeen 98

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Posted 04 February 2020 - 08:29 AM

Hi. I think you need to change the permissions to allow viewing the full sized images in your CN photo gallery.


Changed the album settings. I think they should be accessible now. I didn't realize it was set to private. Thanks for letting me know.
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#16 UKalwayscloudy

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Posted 21 February 2020 - 08:58 AM

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. 

 

It does improve the star shapes massively compared to the standard Celestron one (which I think is identical to the Meade). It does not do away with some of the artefacts from bright stars near the edges. 

 

I've actually settled into taking shots on full frame but with a 1:1 crop and flats. I centre my target carefully so it is in the sweet central zone. I've only been using it a short while but I've attached my flats for full frame. 1:1 (24mm by 24mm) Nikon DX, and an initial test shot of Orion taken with 14 usable images on a very windy night. It should be clear which is which. 24x24mm is just about usable but there will inevitably be worse signal/noise in the corners. The Orion needs a lot more light shots and the image is blurred from wind buffeting (only about 5 of the 14 light frame were good). 

 

I think this is a totally different animal from the standard Meade/Celestron 6.3. The Celestron is a basic focal reducer that really targets a field of view enlargement of 1/0.63 rather than doing some serious correction. The supposed backfocus distance sometimes stated of 105cm is really the target to get that reduction, and is not necessarily the point of best image quality. The Starizona is a targeted at image quality, has a much more precise back focus requirement and you get whatever reduction emerges for your particular SCT. 

 

I'm trying to use it beyond its specified imaging circle in that test shot of Orion. DX or APS-C is better as can be seen from the flat, and you could probably avoid flats completely (dirt aside) if you were shooting on a 16mm square or smaller. 

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#17 Lumix.guy

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Posted 19 March 2020 - 12:22 PM

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.

Rydeen,

I'm quite interested in what back focal distance provided the f/5.6 with the Meade 6.3 reducer.  Many have said the optimum back focus is 105mm, but I have also read (and personally calculated) the proper back focus for f/6.3 should be about 83mm (assuming the focal length of the reducer to be about 225mm which is what I measure for my Celestron 94175).

Thanks,

John



#18 UKalwayscloudy

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Posted 28 March 2020 - 02:02 AM

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. Maybe the numbers around 85 have emerged from someone else experimenting. I was homing on on a number in the 90a and then the Starizona arrived with the precise Backfocus requirement.

The Starizona BF appears to be targeted at maximum image quality. The magnification that emerges depends on your scope and I’m getting around the expected 0.8
On my C6.

I’m summary what I think is that

For Celestron or Meade the 105 gets you the 0.65. Optimal IQ may be elsewhere, possibly 85 -+15% as Ts optic suggest. For Starizona optimal IQ is at 90.3 though I add about 1/3 my filter thickness to that as I have Baader UFC between the reducer and my camera.

Edited by UKalwayscloudy, 28 March 2020 - 02:02 AM.


#19 UKalwayscloudy

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Posted 28 March 2020 - 02:08 AM

In fact I came on here to ask if folks using DSLR or other colour cameras desaturate their flats before stacking. I’ve just tried this with a camera lens and it helped a lot so I am am going to try it here. I’ve been having odd problems with colour variation from the middle to the edge and passing my flats through LR and desaturating before sending them to DSS made a massive improvement.

#20 Rydeen 98

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Posted 28 March 2020 - 08:12 AM

Rydeen,
I'm quite interested in what back focal distance provided the f/5.6 with the Meade 6.3 reducer. Many have said the optimum back focus is 105mm, but I have also read (and personally calculated) the proper back focus for f/6.3 should be about 83mm (assuming the focal length of the reducer to be about 225mm which is what I measure for my Celestron 94175).
Thanks,
John

Apologies, as I keep forgetting to go out and measure this. I'll find my old Meade t-adapter and measure it today.





In fact I came on here to ask if folks using DSLR or other colour cameras desaturate their flats before stacking. I’ve just tried this with a camera lens and it helped a lot so I am am going to try it here. I’ve been having odd problems with colour variation from the middle to the edge and passing my flats through LR and desaturating before sending them to DSS made a massive improvement.

I always calibrate my RAW images before debayering and never had any issues like you are describing. Debayering is the last step before I stack. I've never actually heard of anyone trying to calibrate debayered color images. That could be your issue.

Edited by Rydeen 98, 28 March 2020 - 08:15 AM.


#21 UKalwayscloudy

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Posted 28 March 2020 - 09:47 AM

I’m using Nikon Z6 so am doing no debayering but am starting with files with inherent colour for all lights flats and darks.

#22 Rydeen 98

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Posted 28 March 2020 - 10:26 AM

I’m using Nikon Z6 so am doing no debayering but am starting with files with inherent colour for all lights flats and darks.


I'm not familiar with that camera but are you saying it cannot shoot raw format images? I would imagine you have to change your file save settings and pick raw format instead of JPEG, Tiff or whatever else it might be set to.

#23 Rydeen 98

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Posted 28 March 2020 - 10:36 AM

Rydeen,
I'm quite interested in what back focal distance provided the f/5.6 with the Meade 6.3 reducer. Many have said the optimum back focus is 105mm, but I have also read (and personally calculated) the proper back focus for f/6.3 should be about 83mm (assuming the focal length of the reducer to be about 225mm which is what I measure for my Celestron 94175).
Thanks,
John


Okay measured the mead t-adapter and it's only 55 mm plus the distance into the Canon T3i cavity. Sounds like it's pretty far from ideal.

#24 Lumix.guy

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Posted 28 March 2020 - 10:47 AM

AFAIK almost all modern DSLR (and mirrorless) cameras can capture raw files and DSS reads/decodes most of them properly with automatic debayering by LIBRAW.  LIBRAW is updated often to support new cameras, but I'm not sure if it supports the Z6.  If it does, you might still need to update your DSS to get the latest support for your camera.

 

I can share my personal experience using raw files from my Panasonic G9.  Initially I used Adobe's DNG converter to convert my camera raw files into DNG format (which is compatible with LR and DSS), but I had issues that the debayering was not working properly.

 

Now I use my camera raw files directly and don't have any issue with color debayering.

 

I don't know what UKalwayscloudy's color gradient issue is, but generally we've all seen gradients when shooting from urban areas (skyglow).



#25 Lumix.guy

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Posted 28 March 2020 - 10:51 AM

Okay measured the mead t-adapter and it's only 55 mm plus the distance into the Canon T3i cavity. Sounds like it's pretty far from ideal.

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?




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