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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 |
#2
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Best laser collimator
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 |
#3
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Best laser collimator
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 |
#4
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Best laser collimator
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 |
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