Yes, it seems like the way to do it. It does, however, only align the focuser to the secondary mirror holder, not to the seoondary mirror itself. Final collimation on a starfield is stil necessary. CS
So far is not aligment because only rotations are involved. The centre of Cuverture of the primary gives one point of the axis , but it dosent determine the axis. For that it will need to find the focus of the primary mirror. ( 3 parallele lasers centried to the mirror . the crossing position of the 3 lasers will determine the primary focus. Why? because we don't know if the primary mirror is fully concentric to baffle. it might have an offset ans gives a tilt of the axis or a parallele axis to the one from the baffle. The focuser can be tilt to coincinde its axis to one position of the primary axis. With the 3 lasers you could check if the laser beam by the focuser coincides to the crossing position or a bit a sidev of it . But because this is no possible translaltion at the back of the telescope to align the focuser with 2 positions , thie focuser is correct for one position. What can be done, ionce the focuser is pointing the centre of curvature, is to see if the laser beam is passing the center of the support of the secondary mirror. Because the manufacturer has already optimised this center acording the primary mirror and not the tube of the telescope. Why? because a RC telescope is working with very tiny tollerence regarding the position of the surfaces of the two mirrors less than 0.1mm. The light waves must arrive at the same time accordinf the radial position, on the secondary mirror to remove the coma. When you tilt the secondary , we must be sure the mechanical rotation of the secondary mirror is align to the axis of the primary mirror . Anyway. Here we use the method to point the secondary mirror with the laser to align it by reflection, to the focuser . But is fine for one position , the one of the target. This video shows how you should setup the focuser touching the secondary mirror once you have pointing the centre of curvature of the primary mirror. But by no means this technic is not for collimated the telescope for observing the Sky with the best star image the telescope can offer with the RC configuration. At least I enjoy the video because the good skills of the youtuber with his telescope. I suppose his method is the one you can use for having a good compromise when you don't have an interfometer at home ...
Thank you for your comments, and my apologies for not getting back to you earlier. I'm not sure I follow all of your arguments, but I do agree that my process is a little crude and naturally limited by the equipment I own. While the method for finding the optical axis of the primary is sound, I think, as only a point on the axis will reflect a focused image back on itself, using the laser for aligning the focuser will only point the focuser at that point; it will not make sure that the focuser is actually on the axis if it is not precisely centered. It is, however, a good approximation, and in the end the proof is in the pudding as they say, or in this case, in the stars. The final collimation will always have to be done evaluating the images of the stars.
When adjusting the focuser to be aligned with the optical axis of the primary mirror, the laser is inserted into the focuser and the laser is projected onto the cardboard. I was a little confused by this because I wondered if the secondary mirror holder would block the laser from reaching the cardboard, or is it actually going through the hole that holds the secondary mirror?
Yes, when the secondary mirror holder and the screw is removed the laser goes through the hole for the center screw. If it doesn't the focuser and possibly the primary mirror is very much out of alignment. :)
@@flemmingsastro, ah, thank you for clearing up that confusion. I just upgraded my focuser to the Baader Diamond Steeltrack and also got the tilting plate. My laser collimator arrives today, so I will be aligning everything using your instructional video.
Hello. Thanks for the really good video. I have read that the distance between the primary und secondary mirror is cruxial. How do you collimate the right distance or is it not important? Greetings from Germany :)
Hello. Good question, which means that it is hard to answer conclusively. Platesolving your image will tell you the focal length (FC) provided you have entered the correct pixel size and sensor dimensions into your acquisition software, and the FC of an RC scope is very sensitive to the mirror distance. A single millimeter change in the distance will change the FC of the scope by several millimeters. However, you cannot be absolutely sure that your particular optical system performs best at the exact FC specified by the manufacturer. In my experience the collimation of the mirror angles is way more important for the image quality than the last millimeter of mirror distance. Right now my scope, which is not perfectly collimated yet (I'm still working on it) is at 1621mm focal length, where the nominal FC is 1624. When everything else is perfect, I may experiment with distance again, but until then I'm not worrying about it. Greetings and CS
Thanks for the video! I noticed that the adjustments for the primary mirror are only done on the tilter. Do we have to adjust the primary mirror adjustment screws too?
I first align the focuser with the primary mirror, using the focuser tilting ring. When that is done, I mount the secondary and align the primary mirror to the donut in the middle of the secondary mirror using the screws on the back of the telescope proper. This moves the mirror and the focuser as a unit. In order to see the center donut you find its reflection in the primary mirror looking through the front of the telescope. Maybe watch that part of the video again? Lastly I adjust the secondary until the laser dot is returned to the center of the laser target. If you cannot find the reflection of the secondary's center donut in the primary mirror then your telescope is probably mounted with a primary baffle extention, which you need to unscrew and remove from the tube. Some earlier versions of the scope did not have this baffle extension.
It came with the scope when I bought it second hand, so I can't be absolutely sure, but I believe it is this one www.teleskop-express.de/en/adaptors-10/adapters-tilting-327/ts-optics-m90-tilting-adapter-flange-for-astrophotography-4272
