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TS flattener 2” for 6” f/5 refractor

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#1 The Ardent

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Posted 28 June 2020 - 12:00 PM

I’m looking for a good FF for a 6” f/5 Jaegers refractor. How is this one? 
 

TS-Optics REFRACTOR 1.0x Flattener and Field Corrector - 2" connection

 

https://www.teleskop...Anschluss.html 

 

 

For use with Baader 2” Amici DX2 plus  21 Ethos. 

 

https://agenaastro.c...gonal-2456120/ 

 

The stars at the edge of the Ethos are sharp, just don’t focus at exactly the same as the center. A tiny bit difference. Not much an issue with 82 degree Naglers. Does a FF correct for this? 
 

 

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#2 213Cobra

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Posted 28 June 2020 - 12:55 PM

The effective optical path of the Baader Amici is 80mm. Keep that in mind. The TSFlat2 should solve your FC problem so long as you can position the FF 111mm in front of the eyepiece field stop. You have up to +/-5% slop for visual. From the TS website:

 

The recommended distances from the M48x0.75 thread to the corrector
In principle this rule applies: the shorter the refractor´s focal length, the longer the working distance to the sensor has to be.

♦ focal length < 450 mm: 128 mm
♦ focal length 450-490 mm: 123 mm
♦ focal length 500-550 mm: 118 mm
♦ focal length 560-590 mm: 116 mm
♦ focal length 600-690 mm: 113 mm
♦ focal length 700-800 mm: 111 mm
♦ focal length ab 800 mm: 108 mm

An underrun or an overrun of the distance of up to 5% has no visible effect on the sharpness in the field of sensors with formats up to APS-C. With larger sensors, the tolerance is reduced to 1-2%.

 

In many cases it's enough to simply screw the TSFlat into the filter threads in the nosepiece of the diagonal. If you can't get within +/-5% of the distance spec, then you can use threaded spacers to adjust. The 21mm Ethos has its field stop recessed 0.38" (or 9.652mm) above the shoulder, so your Ethos + Amici effective optical length is almost 90mm compared to using an eyepiece with the field stop at for below the shoulder.

 

Phil


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#3 drd715

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Posted 28 June 2020 - 01:09 PM

F-5 is challenging for an eyepiece or a camera. Getting a flat field from a steep light cone is the challenge. Trying to match a flattener generically to a scope is not always successful. Each separately has a designed function of it's own. Sometimes it can work, but you should check with the flattener designer to see if they recommend their flattener. 




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