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i think i messed up. on barlow choice..advice

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#1 1hander

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Posted 11 February 2019 - 08:01 PM

i wanted to go with ES cuz a friend has them and i got to look thriough them and thought they looked good, but i dont have anything to compare them to ..

 

i started with a 1.25"..6.6 and a 20mm eyepieces... it will focus with 6.6 but not with the barlow under the eyepiece. theoretically i should get close to 139x , so with the barlow, its still below maximum useful magnification..

it needs more in focus...

 

right now im using the

M63  WO camera rotator

with a WO M63 to 2" behind it..

then a 2" ES diagonal

then a WO 2" to 1.25" rotolock on the eyepiece side of the diagonal

 

so that stack is to thick i think... 

if i remove the rotolock and just hold the 6.6mm/2x barlow stack just about 5-10mm lower in the diagonal it will come to focus..

 

so...if remove the rotator and M54 to 2"adaptor stack and just go with an M63 to 2" visual back, this will remove 20mm from the stack, is that usually the way this would be remedied..

or by using a thinner 2"to1.25" adaptor on the eyepiece side of the diagonal instead of the rotolock

or is it possible that i will need to do both of the above.. 

 

it possible that what i recieved with the OTA  was just not setup for visual, but setup for imaging..

 

rick


Edited by 1hander, 11 February 2019 - 08:10 PM.


#2 photoracer18

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Posted 11 February 2019 - 09:06 PM

OK starting over. Remove everything that you don't need. Also the Barlow may need to go between the telescope and the diagonal. That will raise a 2x Barlow to at least 2.75x.

Edited by photoracer18, 11 February 2019 - 09:11 PM.


#3 1hander

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Posted 11 February 2019 - 11:45 PM

your absolutely right, im an idiot...i took off the rotator and put on just the m63 to 2" visual, and voila...geeez 



#4 gnowellsct

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Posted 12 February 2019 - 11:20 PM

In focus and back focus are operational issues.  It's really annoying to find you've invested in a high end apo and it doesn't really have the focus travel you need.  One just sort of assumes everything will be OK.  That's usually true, but not always.



#5 1hander

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Posted 13 February 2019 - 03:29 PM

once i removed the rotator, it would focus with the 6.5 and 2x barlow at about 15mm out travel..so it still has lots of room to focus well past its useful magnification..i got lucky, but as you said i was wondering how one figures out if an OTA has the necessary travel to focus with the extreme ends of eyepiece focal lengths... 

 

cuz ive seen the aftermarket focusers that have like 2 inches only of focus travel.. some 2.5 ... i just got lucky this time. 



#6 aeajr

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Posted 14 February 2019 - 06:23 PM

It seems you are interested in AP.  This forum is for visual astronomy so I am going to move it to the imaging forum for better exposure to the right people. 




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