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SkyWatcher Esprit 150mm APO backfocus.

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#1 nitesky

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Posted 26 November 2020 - 12:05 PM

I currently have an Esprit 100mm. I've been imaging with it for a few years and have the ZWO 8 position FW, ZWO OAG, and ZWO ASI1600mm Pro cooled. I just received my new Esprit 150mm APO. I have installed a Moon Lite focuser on the 150 as I did with the 100. I was checking when ordering the focuser about if I'd need a different adaptor for the 150's field flatner or other spacers. I learned that the 150 field flatner and my 100 are the same size so my adaptor ring from the focuser to the field flatner will work. Perhaps the gentleman was referring to just the one adaptor but I got the feeling that he meant I'd be good to go.

 

I know that the Esprit 100 had a back focus to the sensor of 63 mm if my memory serves me right. I saw in the Esprit 150 it is 100mm?  I wouldn't think my current spacing would work. 

 

Anyone with a 150mm using same or close to same image train as I described above and what space(s) and their sourcing? IF this has already been presented, I'm sorry, point me to the appropriate thread, please. I did a search but didn't find what I believe I was looking for.

 

Thanks

Paul



#2 skyward_eyes

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Posted 26 November 2020 - 05:22 PM

On the Esprit we provide a spacer ring that threads onto the flattener and brings the threads down to M48 for mounting the M48 Canon adapter.

From these M48 threads the back focus is now 55mm for all the Esprits. If you’ve got your set up adapted to that M48 thread the back focus will be the same.

If you want to thread direct to the field flattener then you would be able to use all the back focus of the corrector but you would need a custom adapter/spacer.

#3 nitesky

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Posted 26 November 2020 - 06:06 PM

Well maybe I'm in luck then. The Moonlite focuser has 68mm threads. I purchased their 68mm to M48 adaptor That is the same arrangement on my Esprit 100. 

 

I'm looking at the 150mm user manual, page 3. The spacer you refer to, is it #4, field flatner extender tube for DSLR or are you referring to #6 Thread on Field flatner adaptor? 

 

Please confirm which adaptor #4 or #6, you are calling a spacer.

 

Paul



#4 skyward_eyes

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Posted 26 November 2020 - 06:18 PM

Yea #4 spacer.

#5 nitesky

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Posted 26 November 2020 - 06:51 PM

Ok thanks. I'll have to look to see when I get home what the threads are that connect in my image train now. Yep, otherwise I'll need a custom adaptor.

 

Paul



#6 nitesky

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Posted 28 November 2020 - 07:11 AM

Somehow, I had enough extra coupler 'parts' that I believe I've been able to use the focus extension spacer between my  field flatner and OAG.  I'm going to try it out this evening to verify the results edge-to-edge.  Thanks for the information.  

 

Image included.

 

Paul

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#7 SimonMiller

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Posted 29 November 2020 - 05:30 PM

Somehow, I had enough extra coupler 'parts' that I believe I've been able to use the focus extension spacer between my  field flatner and OAG.  I'm going to try it out this evening to verify the results edge-to-edge.  Thanks for the information. 

How much back focus (looks a lot)? I have (just) two 5mm extensions and a 21mm extension around an OAG (19mm).




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