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Please recommend OAG under 29mm for ASI174mm-mini

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#1 Master_Shake

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Posted 26 March 2020 - 02:46 AM

I am looking for an OAG with a large prism to take advantage of the ASI174mm-mini sensor size.  I plan on using this with the Starizona .65 FF/FR once i get it and will need 57mm backspace for train.  The max length it can be is 29mm.  It is difficult to find information on prism size.  I just bought the Teleskop Service TSOAG27 to replace the ZWO OAG.  I incorrectly interpreted the length of OAG for an M48.  I thought it was 27mm but instead it is 33mm, putting me over where i need to be.   

 

I am looking for a first-hand recommendation on what i can use.  Thank you.


Edited by Master_Shake, 26 March 2020 - 02:47 AM.


#2 Kaydubbed

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Posted 26 March 2020 - 09:01 AM

It's tough. I know. I was really disappointed when I found my imx174 had that porthole effect on my ZWO OAG. You will need at least a 12mmx12mm prism to avoid vignetting and I don't think one exists that isn't the Celestron OAG, which of course is out of your specs. The Orion Thin OAG comes close, but you will still get vignetting. I haven't been able to find the size of that prism but anecdotes on CN show that the vignetting is still there with the OTOAG, but much less than the ZWO. 



#3 Master_Shake

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Posted 26 March 2020 - 08:00 PM

bummer. I was afraid to hear this.  Thanks for you input.




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