Paracorr blues

I dont know about you guys but my visuable Paracorr is driving me nuts.Let me explain.When I collimate my Dob I can get everything to line up after laser ,sight tube ,chesire and autocollimator.Then I perform a lasered barlow procedure with Paracorr and its at least off 5mm at the diagonal faceplate.This is indicating the Paracorr is throwing it off.When I look at the construction of the Paracorr all I see is the introduction of 2 more piece of equipment in the light path to introduce misalignment ,the tube plus the loose tunable body wich is not a very tight fit can be turned and locked in many different spots.I guess the flip side is to not used one and put up with coma.Any one else having the same problems ?


thanks

gerry

>>>After final alignment using a star and NO Paracorr, how does the image look when the Paracorr is inserted: Any degradation?
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Yes, this is the question. Assuming that the laser is properly aligned and that the scope is collimated, I think it is not necessary to assume that pointing the laser through the Paracorr should hit the center...

When I thought my 1.25 inch Paracorr was slightly off for similar reasons, I Emailed Steve White of TV and he said it does not matter....

jon

While its a little bothersome, I don't think it really matters
much. It appears that your Paracorr is slightly tilted, but
it will have almost no effect on the eyepiece image quality.
This is because the eyepiece is right next to the Paracor
optics, so any tilt makes only a very small linear
displacement from the eyepiece optical axis. On the other
hand when you put the laser in there and shine it on the
diagonal mirror, there is a much larger lever arm, and it
exagerates the offset.

Yes I find theres a slight degradation if I put back in the paracorr.I guess mine might be an older model (no compression ring) and there is alot of slop in the twisting body wich makes it inconvenient during a session when I swap eyepieces.It seems everytime I swap I cannot lock it in the same way.Its not repeatable.My initial question was just to see if someone out there is experiencing the same thing and if theres a work around this problem.

thanks

gerry

I don't know, I find the paracorr virtually useless with my 14.5" f/4.5 optics. Coma doesn't seem to be much of a problem anyway. I don't think my paracorr has even left the eyepiece case in a year or two. JDBraddy

GERRY LEVAC said:

I dont know about you guys but my visuable Paracorr is driving me nuts.Let me explain.When I collimate my Dob I can get everything to line up after laser ,sight tube ,chesire and autocollimator.Then I perform a lasered barlow procedure with Paracorr and its at least off 5mm at the diagonal faceplate.This is indicating the Paracorr is throwing it off.When I look at the construction of the Paracorr all I see is the introduction of 2 more piece of equipment in the light path to introduce misalignment ,the tube plus the loose tunable body wich is not a very tight fit can be turned and locked in many different spots.I guess the flip side is to not used one and put up with coma.Any one else having the same problems ?


thanks

gerry