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SCT reducer/correctors: Celestron 0.63 vs. Baader Alan Gee vs. Starizona SCT Corrector?

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#1 DMach

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Posted 20 April 2019 - 04:26 AM

Any opinions on the pros and cons of the various reducer/corrector options available for SCTs?

 

In particular I'm wondering whether the Baader Alan Gee and/or Starizona SCT Corrector are worth the extra $$$?

 



#2 junomike

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Posted 20 April 2019 - 05:47 AM

It depends on what you're going to be using it with (CCD/chip size).  All those above will illuminate small sensors but will Vignette larger sensors (and long F/L eyepieces).

If your OTA is threaded for the 3.25" adapters (Edge 9.25, C11, C14) then this will handle a 42mm Image Circle

I've always wanted to try the LF with a 31T5 and see if there's any Vignetting?

 

Just noticed the Alan Gee is only recommended for the 8" SCT however I think it's fine for F10 SCT's,



#3 DMach

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Posted 20 April 2019 - 08:38 AM

It depends on what you're going to be using it with (CCD/chip size).  All those above will illuminate small sensors but will Vignette larger sensors (and long F/L eyepieces).

If your OTA is threaded for the 3.25" adapters (Edge 9.25, C11, C14) then this will handle a 42mm Image Circle

I've always wanted to try the LF with a 31T5 and see if there's any Vignetting?

 

Just noticed the Alan Gee is only recommended for the 8" SCT however I think it's fine for F10 SCT's,

Thanks Mike.

 

I did also see the large format Starizona, but personally I'm looking for something that I can place after a R&P/Crayford style focuser ... so I've pretty much accepted this will mean using a sensor that's less than full size.

 

On Baader's web site the specs do state '8" Schmidt-Cassegrains' but reading the instruction manual they state 'fits into 8" and larger Schmidt-Cassegrain' and list applications for larger OTAs.

 

However, whereas some vendor web sites state the Alan Gee has a 'usable illuminated field diameter of 32 mm', Baader's manual states it has a '15mm optimal imaging circle'. That is indeed on the small side.

 

The Starizona SCT Corrector II, on the other hand, claims a 'nominal image circle of 27mm' ... which might be the safer bet with my ASI294 (4/3 format). Assuming that 27mm has no/minimal vignetting ...


Edited by DMach, 20 April 2019 - 08:39 AM.



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