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I bought a 4x Powermate, now how do I get things in focus with it?

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#1 ImNewHere

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Posted 19 October 2018 - 05:06 PM

I bought a 4x Powermate and went to use it last night trying for Saturn and Mars with both my Pentax K3 DSLR and my Samsung Mini with a Pentax adapter on it. I couldn't get ti to focus on my 8RC even with an extra 2 inch extension in there, so rather than wasting time I simply stuck my 2.5x barlow on it and used that. That brings me to my question, which is what is the required backfocus to bring it into focus? I'm only using a 1 inch extension ring between the focuser and scope. With a 2 inch extension tube on my 2.5x Luminos barlow and ATFF2 flattener I got things in focus no problem using the moon. I definitely want to attempt using this next night we have skies like we did, and if need be with my ASI178MC. Thanks for any advice.



#2 B 26354

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Posted 19 October 2018 - 05:28 PM

Don't really have an answer for you, except to say that I need to use two ~37mm long extension tubes when I'm attaching my Olympus E-M1 and non-reducing FF to my ES 102CF... but when I use the ES 2X Focal Extender (minus the FF) with it, through trial-and-error, I discovered that I have to add two more ~37mm long extension tubes, to reach focus. That's a  pretty serious difference. Can't imagine what a 4X will require.   shocked.gif



#3 h2ologg

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Posted 20 October 2018 - 04:37 PM

Add more extension tubes for back focus!  If you need more front focus, like most of my home built reflectors matched with Powermates, I had to purchase their “T” adapters (PTR-4201 PMT-4201 T-Ring Adapter is for the 4x PM) thus tying the ADC to the camera and removing the “eyepiece” portion of the PM.

 

Also you might want to remove the field flattener if your using one (again for front focus). The field of view we’re shooting for planets is generally so small that you won’t see any field curvature in your images.

 

Good luck.

 

Dan




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