Baader laser colli

[jonpugh114]

Hello,

I'm trying to find out whether the latest Baader laser collimator is effective on SCT's. As far as I can tell, many competing collimators aren't up to the task so I was wondering whether anyone has had any success with this model?

Cheers

Jon

[BT Technologies]

Hello Jon.. My personal experience with laser collimators for SCT's is that they will get you in the "ballpark" but still require actual fine tuning of the collimation via a star test.

[Spoonsize]

I agree with what Brian says....AND...I've been told that one has to do an accuate collimation the "old" method, and then insert the laser collimater into the SCT, and make note of where the laser pattern forms. Then, when one suspects the SCT is out of collimation, insert the laser device and return the collimation pattern to the original spot.
IMHO>>>It's just as easy to collimate the same way all the time, and spend the money on something else...
Steve

[djgares]

I agree with Steve and Brian. I use a laser on my Newt, but a set of Bob's Knobs and a star test seems like the way to go for my SCT. Just drive a centered star out of focus, then tweak the scope left/right and up/down till the diffraction rings are as concentric as possible. That "sweet spot" in your field of view will be off-center, so then drive the star home to the middle of the field with the collimation knobs. A few iterations with a couple of eyepieces will get you there. If you're picky you can aim at a star near your planned targets to compensate for mirror flop differences when aiming east vs. west.

One Baader ad says your must remove and center-mark your secondary to use their laser on an SCT. Geez, I wouldn't have the guts to do it and surely your warranty would be voided.

I think some SCT lasers require you to point the tube horizontal to project rings on a target. Then your primary could be tilted differently than normal, albeit slight. Always star test to validate your laser collimation. My Newt laser loses its own collimation, and the factory folks can't seem to get it perfect. I've taken to swiveling it in the focuser to traverse a tiny arc, the center of which is where the dot is supposed to be (but isn't).

I'm not good enough to estimate wavefront error, but the star test even reveals simple bugs. Last night I found my flip-mirror diagonal was vignetting my eyepiece. I think I had extended the eyepiece too far when I parfocalized it with my camera. Defocused rings were "chopped" square on the top or bottom when a star was placed near the upper and lower edge of the field. Sure enough, the edges were dimmed when compared to another diagonal. The star test is the way to go.

Clear Skies,
David Gares
www.djgares.com

[djgares]

I agree with Steve and Brian. I use a laser on my Newt, but a set of Bob's Knobs and a star test seems like the way to go for my SCT. Just drive a centered star out of focus, then tweak the scope left/right and up/down till the diffraction rings are as concentric as possible. That "sweet spot" in your field of view will be off-center, so then drive the star home to the middle of the field with the collimation knobs. A few iterations with a couple of eyepieces will get you there. If you're picky you can aim at a star near your planned targets to compensate for mirror flop differences when aiming east vs. west.

One Baader ad says your must remove and center-mark your secondary to use their laser on an SCT. Geez, I wouldn't have the guts to do it and surely your warranty would be voided.

I think some SCT lasers require you to point the tube horizontal to project rings on a target. Then your primary could be tilted differently than normal, albeit slight. Always star test to validate your laser collimation. My Newt laser loses its own collimation, and the factory folks can't seem to get it perfect. I've taken to swiveling it in the focuser to traverse a tiny arc, the center of which is where the dot is supposed to be (but isn't).

I'm not good enough to estimate wavefront error, but the star test even reveals simple bugs. Last night I found my flip-mirror diagonal was vignetting my eyepiece. I think I had extended the eyepiece too far when I parfocalized it with my camera. Defocused rings were "chopped" square on the top or bottom when a star was placed near the upper and lower edge of the field. Sure enough, the edges were dimmed when compared to another diagonal. The star test is the way to go.

Clear Skies,
David Gares
www.djgares.com

[richwood]

My own experience is that any single dot laser collimator will not work well with most SCTs. The problem is that the primary mirror is generally not that well collimated and is not adjustable. it also suffers from variable alignment due to mirror flop which can vary in amount from unit to unit. Thus the secondary needs to be adjusted to a compromise position in order to compensate for inaccuracies in the primary position.

A fully collimatable system such as the 200mm Vixen units or a classical cassegrain should be able to have the secondary zeroed by a laser collimator. The star test would then be used to collimate the primary mirror.

With any laser collimator one thing that should be done is to check the alignment of the collimator itself. If it draws a circle on the wall when rotated in a machinist's "V" block or on the primary mirror when installed in a Newtonian and rotated in the focuser then the collimator itself needs collimation. I have machined and aligned several of my own as well as checked a number of commercial laser collimators for club members. Several of the commercial units have not been well aligned.

richwood

[BT Technologies]

Excellent information Rich. I owned a Intes Micro Maksutov which had a fully adjustable primary as well as the secondary. I was never able to get your typical SCT type laser collimator to work perfectly and always simply relied on the tried and true star test to "tweak" the optics for perfect collimation.

It is definitely true that even the collimators themselves need to be adjusted properly in order to work. I had 3 different units and ALL of them were not properly collimated. When holding the unit in a V-Block and rotating it, the laser dot moved a significant amount.

I still believe that laser collimators have their place but for me, I have used them to get the alignment "in the ballpark" followed up by a star test for final adjustments.

Originally Posted by richwood

My own experience is that any single dot laser collimator will not work well with most SCTs. The problem is that the primary mirror is generally not that well collimated and is not adjustable. it also suffers from variable alignment due to mirror flop which can vary in amount from unit to unit. Thus the secondary needs to be adjusted to a compromise position in order to compensate for inaccuracies in the primary position.

A fully collimatable system such as the 200mm Vixen units or a classical cassegrain should be able to have the secondary zeroed by a laser collimator. The star test would then be used to collimate the primary mirror.

With any laser collimator one thing that should be done is to check the alignment of the collimator itself. If it draws a circle on the wall when rotated in a machinist's "V" block or on the primary mirror when installed in a Newtonian and rotated in the focuser then the collimator itself needs collimation. I have machined and aligned several of my own as well as checked a number of commercial laser collimators for club members. Several of the commercial units have not been well aligned.

richwood

[Gary Beal]

Originally Posted by BT Technologies

I still believe that laser collimators have their place but for me, I have used them to get the alignment "in the ballpark" followed up by a star test for final adjustments.

And another thought was to get or make an artificial star, for tweaking on those cloudy nights. I did and it gets me real close, with just the merest tweak needed on the real thing.
Gary