Best laser collimator

I also find that a laser (the LaserMax in this case) is quicker and more
convenient, particularly at night. (And this is quite helpful, since I
tend to do most of my observing at night.) I also appreciate being able
to make adjustments without running back and forth between the primary
and secondary.

On the other hand, I recognize that there are limitations with some of
the laser methods, including errors that may be caused by misalignment
of the laser itself and/or the focuser. I have tried using a Barlow
lens in front of the laser, as discussed last year in S&T, and this does
seem to enhance the results.


I'm wondering whether anyone has tried the following variation:
(Incidentally, when I posted this note, all the paragraphs and
indents were carefully aligned. If it goes as usual, it will look like
a mess when posted on the ng, for which I apologize in advance.)

Step A. - Make initial collimation alignment with a cheshire, or
autocollimator.

Step B - Fine-tune the alignment by a careful star-test, carefully

correcting any misalignment until a good pattern is observed.

Step C - Insert the laser collimator into the well-collmated scope.
(Make no adjustments to either the primary or secondary.)
Observe the laser pattern resulting from this alignment.
(In this case, it's a circle positioned within a pattern of
hatched, perpendicular cross-lines, visible on any
flat surface positioned perpendicular to the OTA and
spaced from the open end.) Assuming that the laser collimator is not
precisely accurate, the "spot" or shadow would not be perfectly
centered, but would be somewhat deviated from the exact
center of the cross-lines.

Step D - Observe and record or remember the exact position of the
spot under those conditions, including the number of hatch marks
by which it is deviated from the center in the horizontal and
vertical directions. (E.g., record the delta or deviation entailed.

Step E. - When using the laser for collimation in the future,
position the spot at the deviated position observed in Step D rather
than the centered position. - In other words, enter the appropriate
correction to eliminate most of the errors that may arise due to
physical misalignment of the laser or the focuser, etc.

Although the above process may appear to be somewhat involved and time
consuming, once the error corrections are determined, future use of the
laser would be just as convenient as the normal, non-corrected
procedure. Incidentally, if you question why I haven't used the method
and why I'm not reporting my results, I'm in the Houston area, and we
haven't had clear, or comfortable weather when I was free to observe
for many weeks.)

Jim



Chris L Peterson wrote:
On 7 Jul 2003 21:52:51 -0700, (Jack Schmidling) wrote:


There is absolutely nothing you can do better with a laser than with a
simple peephole and spot on the mirror.


I prefer using a laser, and find it lets me collimate much faster, because I can
perform the entire procedure from the back of the telescope. My arms aren't 5
feet long, and all of the eyepiece methods require moving back and forth. So
while I agree that the laser doesn't give any better results (or worse) I do
think the differences in procedure may be useful to some.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

One further step should probably be noted. - The initial alignment of
the secondary, which in my case (after centering in the viewfinder) is
an adjustment of the secondary alignment screws to bring the reflected
spot into coincidence with the transmitted spot, would be done as usual
prior to making the primary adjustment as described below. I've tried
to modify the outline below. However, I don't think that the secondary
adjustment is needed as often.

Jim


I also find that a laser (the LaserMax in this case) is quicker and more
convenient, particularly at night. (And this is quite helpful, since I
tend to do most of my observing at night.) I also appreciate being able
to make adjustments without running back and forth between the primary
and secondary.

On the other hand, I recognize that there are limitations with some of
the laser methods, including errors that may be caused by misalignment
of the laser itself and/or the focuser. I have tried using a Barlow
lens in front of the laser, as discussed last year in S&T, and this does
seem to enhance the results.


I'm wondering whether anyone has tried the following variation:
(Incidentally, when I posted this note, all the paragraphs and
indents were carefully aligned. If it goes as usual, it will look like
a mess when posted on the ng, for which I apologize in advance.)

Step A. - Make initial collimation alignment with a cheshire,
or autocollimator.

Step B - Fine-tune the alignment by a careful star-test, carefully
correcting any misalignment until a good pattern is observed.

Step C - Insert the laser collimator into the well-collmated scope.
(Make no adjustments to either the primary or secondary.)
Observe the laser pattern resulting from this alignment.
(In this case, it's a circle positioned within a pattern of
hatched, perpendicular cross-lines, visible on any
flat surface positioned perpendicular to the OTA and
spaced from the open end.) Assuming that the laser
collimator is not precisely accurate, the "spot" or shadow would not
be perfectly centered, but would be somewhat deviated from
the exact center of the cross-lines.

Step D - Observe and record or remember the exact position of the
spot under those conditions, including the number of hatch
marks by which it is deviated from the center in the horizontal
and vertical directions. (E.g., record the delta or
deviation entailed.

Step E. - When using the laser for collimation in the future,
make initial adjustments of the secondary as usual. For adjustment of
the secondary, align as usual, For the primary, position
the spot at the
deviated position observed in Step
D rather than the centered position. - In other words, use the correction
factor to eliminate most of the errors that may
arise due to physical misalignment of the laser or the focuser, etc.

Although the above process may appear to be somewhat involved and time
consuming, once the error corrections are determined, future use of the
laser would be just as convenient as the normal, non-corrected
procedure, though perhaps not quite as accurate as a careful star test adjustment.
Incidentally, if you question why I haven't used the method
and why I'm not reporting my results, I'm in the Houston area, and we
haven't had clear, or comfortable weather when I was free to observe for
many weeks.)

Jim



Chris L Peterson wrote:

On 7 Jul 2003 21:52:51 -0700, (Jack Schmidling) wrote:


There is absolutely nothing you can do better with a laser than with a
simple peephole and spot on the mirror.



I prefer using a laser, and find it lets me collimate much faster,
because I can
perform the entire procedure from the back of the telescope. My arms
aren't 5
feet long, and all of the eyepiece methods require moving back and
forth. So
while I agree that the laser doesn't give any better results (or
worse) I do
think the differences in procedure may be useful to some.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

One further correction. - The initial adjustment of the secondary is
normally done by aligning the reflected spot with the marked center of
the primary. - This should be done initially, immediately following set
up of the scope.



Jim Cate wrote:
One further step should probably be noted. - The initial alignment of
the secondary, which in my case (after centering in the viewfinder) is
an adjustment of the secondary alignment screws to bring the reflected
spot into coincidence with the transmitted spot, would be done as usual
prior to making the primary adjustment as described below. I've tried
to modify the outline below. However, I don't think that the secondary
adjustment is needed as often.

Jim


I also find that a laser (the LaserMax in this case) is quicker and
more convenient, particularly at night. (And this is quite helpful,
since I tend to do most of my observing at night.) I also appreciate
being able to make adjustments without running back and forth between
the primary and secondary.

On the other hand, I recognize that there are limitations with some of
the laser methods, including errors that may be caused by misalignment
of the laser itself and/or the focuser. I have tried using a Barlow
lens in front of the laser, as discussed last year in S&T, and this
does seem to enhance the results.


I'm wondering whether anyone has tried the following variation:
(Incidentally, when I posted this note, all the paragraphs and
indents were carefully aligned. If it goes as usual, it will look
like a mess when posted on the ng, for which I apologize in advance.)

Step A. - Make initial collimation alignment with a cheshire,
or autocollimator.

Step B - Fine-tune the alignment by a careful star-test, carefully
correcting any misalignment until a good pattern is observed.

Step C - Insert the laser collimator into the well-collmated scope.
(Make no adjustments to either the primary or secondary.)
Observe the laser pattern resulting from this alignment.
(In this case, it's a circle positioned within a pattern of
hatched, perpendicular cross-lines, visible on any
flat surface positioned perpendicular to the OTA and spaced
from the open end.) Assuming that the laser collimator is
not precisely accurate, the "spot" or shadow would not be
perfectly centered, but would be somewhat deviated from the
exact center of the cross-lines.
Step D - Observe and record or remember the exact position of the
spot under those conditions, including the number of hatch
marks by which it is deviated from the center in the
horizontal and vertical directions. (E.g., record the
delta or deviation entailed.

Step E. - When using the laser for collimation in the future,
make initial adjustments of the secondary as usual. For
adjustment of

the secondary, align as usual, For the primary,
position the spot at the
deviated position observed in Step

D rather than the centered position. - In other words, use
the correction factor to eliminate most of the errors that
may arise due to physical misalignment of the laser or the
focuser, etc.

Although the above process may appear to be somewhat involved and time
consuming, once the error corrections are determined, future use of
the laser would be just as convenient as the normal, non-corrected
procedure, though perhaps not quite as accurate as a careful star test
adjustment.

Incidentally, if you question why I haven't used the method

and why I'm not reporting my results, I'm in the Houston area, and we
haven't had clear, or comfortable weather when I was free to observe
for many weeks.)

Jim



Chris L Peterson wrote:

On 7 Jul 2003 21:52:51 -0700, (Jack Schmidling) wrote:


There is absolutely nothing you can do better with a laser than with a
simple peephole and spot on the mirror.




I prefer using a laser, and find it lets me collimate much faster,
because I can
perform the entire procedure from the back of the telescope. My arms
aren't 5
feet long, and all of the eyepiece methods require moving back and
forth. So
while I agree that the laser doesn't give any better results (or
worse) I do
think the differences in procedure may be useful to some.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Jack Schmidling wrote:

I no nothing about a projected holographic target but I find with the
Orion laser I just bought that there is a great deal of uncertainty
about the final adjustments.

One has to put a rather dim and small spot in the center of a very
bright, large and mushy one and this requires luck. Everytime I do it
and then check with the peep hole, it is rarely exactly centered.

Hi, Jack -

I have the Orion unit as well and have no problems with it. However,
before I used it the first time I covered the face of it (where the light
emerges) with retroreflective white tape with a hole for the laser. The
result is that the reflected dot is almost exactly as bright as the laser
itself as seen from the mirror end of my 10" (254mm) f/6.5 Dob. So
adjusting the primary collimation bolts is trivially easy and takes only a
few seconds.

The "dim" spot is probably due to its reflecting off a black anodized
surface. Try the above - I think you'll like the change a lot!

Jim Horn, Sonoma County, California