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2" Barrel extender to fit HoTech "Field Flattener

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#1 CJM

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Posted 24 January 2013 - 03:51 AM

Hi, can anyone out there give me directions on where to find a 2" barrel extender with male thread to fit into 48mm female threaded end on my 2" HoTech field flattener and provide an additional 20mm back focus which Iam short of.
Have my modified canon 350D rebel connected to field flattener inserted into 80mm focuser draw tube of my AT111 EDT Apo I cannot quite get focus.
Any help will be greatly appreciated.
Thanks
Chris (CJM) :help:

#2 Jon Isaacs

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Posted 24 January 2013 - 04:37 AM

Hi, can anyone out there give me directions on where to find a 2" barrel extender with male thread to fit into 48mm female threaded end on my 2" HoTech field flattener and provide an additional 20mm back focus which Iam short of.



Just to be clear:

Do you need "backfocus" or do you need more "outward" focuser travel. Backfocus is "inward focuser travel".

Jon

#3 cjc

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Posted 24 January 2013 - 10:21 AM

Cheapest is Baader Hyperion fine tuning rings which come in 14mm and 28mm. Smaller changes can be made with empty 2" filters.

#4 CJM

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Posted 01 February 2013 - 05:23 AM

Hi Jon, I run out of outward focus travel (full 80mm wound out and short by about 15mm to bringing into focus.Note: I have my right angle eye piece extender on the Canon XT.

Hope this clarifies things for you.

#5 achronut

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Posted 01 February 2013 - 03:48 PM

How do you like you Hotech ff? I use the AT2FF and get good results with my AT111EDT. I use this plus an empty 2" filter cell, and parfocal ring like this as a stop.
In seqeunce: camera - AT2FF - filter cell - parfocal ring around barrel extension.

#6 CJM

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Posted 01 February 2013 - 04:45 PM

Have only looked through it during testing of focusing ability with canon Rebel 350D attached including eye piece extender on Canon and after drawing the flattener back out of focuser tube by 15mm - this when I finally got focus.
Have the correct back focus of 55mm for canon and flattener set up but will use a 2" threaded tube extension to sort things out.
As for eye viewing I got good clarity of Jupiter's cloud rings so should be able to do better with multiple and long exposure shots once I get the extension tube.






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