Quote:
Originally Posted by Zubenel
HI David , I would be interested if I knew it would reach focus. I have a ATM ultra low profile crayford focuser. I have a type 4 12mm Nag that focuses nicely and a 24.5mm Meade 67degree Superwide afov that is at the bottom of my focuser range and just get's it in. a 35mm Pan also sits in the range. If you have any of these and could measure to confirm you may have a sale.  |
See
http://www.televue.com/engine/TV3b_p...4#.UzDRAKiSy5I and look at column F.
The filed stop location of the 12NT4 is 0.78" below the top of the 2" skirt whereas that of the 22NT4 is 0.29" above. That is a 1.07" difference.
I find though that if you use the 12NT4 in 1.25" mode and the 22NT4 is obviously 2" only you will have less of a focus difference. Tele Vue sell a 2" barrel extension that works very well with the 12NT4 if you want to use in 2" mode.
The issue you may have is whether you can rack in the focuser enough for the 22NT4. You can work this out from the Tele Vue specs. and by measuring the height of the 12NT4 from the top of the 2" focuser where the 2"-1.25" adaptor sits. Remember to take into account any difference the adaptor makes if it is recessed for example.
If you are already using your 12NT4 as a 2" (without barrel extension) then you must ensure you have 1.07" focuser travel available inward. I cannot use my 12NT4 in 2" mode since I do not have enough outward travel hence the barrel extension but in 1.25" mode and a thick 10mm 2"-1.25" adaptor it is fine and I end up racking in further and closer to the field stop of my other eyepieces.
