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Which focal reducer (fr), and fr/field flattener should I use?

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#1 PhotonHunter1

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Posted 30 June 2022 - 06:03 PM

Hi everyone, I just received my ES 102 APO Triplet FCD-100 series refractor which comes with the 2.5 Hex Focuser. I would like to direct connect my ASI2600MM-Pro camera/EFW to the focusing draw tube vs. using the focusing ring. I'm interested in recommendations for a Field Flattener, and a Field Flattener/Focal Reducer. My search has led me to the follow two options for FF/FR:

  • The Explore Scientific 3" Field Flattener / 0.7x Focal Reducer which ES recommends using with their 127mm refractor
  • The Starizona Apex ED-L / 0.65x Focal Reducer & Field Flattener (2" barrel) which I've been told will work with the 2.5 Hex Focuser, with the appropriate adapter

 

The only Field Flattener option I've found is the Explore Scientific 2" Field Flattener - FFEDAPO-01.

 

Are there any other other FR, and FF/FR options that I may have missed in my search?

 

Thanks in advance for your help.



#2 rgsalinger

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Posted 30 June 2022 - 06:52 PM

I would use the one that the factory recommends always in any situation as a good general rule.

 

However, if you personally call Starizona and Dean tells you that his reducer will work then that's a viable option.

 

The more radical the reduction the smaller the image circle. Are both of these rated for an APS-C chipped camera? 

 

 

Also, you're using a mono camera so make sure that you are confident that you have sufficient back focus in either case. 

 

Rgrds-Ross



#3 PhotonHunter1

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Posted 30 June 2022 - 08:01 PM

Thanks Ross. I did call Starizona and they confirmed the Apex-L would work and confirmed the adapter I would need to connect the 2" barrel to the 2.5" focus tube. I'll have to re-read but I do not recall them stating one way or the other if these were rated for APS-C chips. However, I have to believe they are as I was using the Hotech SCA and the Stellaravue SFFR-102 (both 2" barrels) with my 102 APO Triplet Essential Series (I upgraded to get the Hoya glass and the beefier Crayford 2.5 Hex Focuser).




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