Rural central lower Michigan
16" F/12 R-C with optics figured by Paul Jones mounted on Byers Research Grade Series II mount with Gemini II GOTO housed in 11.5' Sirius Observatory; C11 on G11;a few Ethoi and other longer focal length Televue eyepieces in the 2" format; a 6" F/10 refractor for which I made the achromatic objective.
Quote:By the way, this method works better on a Cassegrain with spider vains than on one without, because coinciding the spider vains with their reflections is much more precise than just monitoring the concentricity of the "doughnut".
"A telescope is either good or cheap, not both" - but sometimes you get lucky!
“I am the only person to ever ace a 1951 USAF resolution test. My 'to observe' list says 'done'. I do not use charts or atlases when I starhop; men do not use maps. One of my sketches won an SBIG deep sky imaging contest. I am the life of star parties I have never attended. I never say anything looks like a faint fuzzy - not even a faint fuzzy. Pilots aim green laser pointers at me. Don Pensack proofreads my CN forum posts.” - The Most Interesting Astronomer in the Universe
Leica 8x20; Nikon Action 7x35; Vixen Apex Pro 8x42; Orion 15x63; Docter Nobilem 15x60
WO Megrez II 80 FD / APM 107mm f/6.5 / Mewlon 210 on DM-6 + Berlebach Planet
Quote:Thanks and credit to Fred at Texas Nautical for this procedure that he developed.Here is the procedure,You get a 2ft.x2ft. piece of white paper board and drilled a 3/8" hole in the center. You then set up the OTA on my mount pointed directly at you at eye level with the sec. mirror holder. This is about 50 or so inches away and look straight down the OTA at the center of the back of the sec.you will see the spider vanes and then the spider vanes reflected in the primary mirror.As you look at them if you are the right distance you will see what looks like a black doughnut which is the baffle tube. Now that you see it position yourself the correct distance to super impose the sec. holder into the black ring which is the baffle tube - primary ring nut, sit where the sec. holder and the pri. baffletube and nut are the same size, you move father away the ring nut appears larger and conversely smaller when you get closer..Now this sounds crazy until you look at the OTA this way then it will make sense. Once you see what I have described you can take the white paper board and hold it close to your face as you look through the hole in it into the axis of the scope.The white will make it easy to see the spider vanes and the pri. baffle-retaining ring nut.As you look down the optical axis you will see two complete sets of spider vanes, one set is the actual vanes the other set is the vanes reflected in the primary. Ok we are at the point of checking collimation, does the vanes align directly which each other or are they offset be sure you are looking straight down the center of the optical axis by keeping the sec. holder in the center of the prim. baffle-ringnut. On mine the three vanes would appear as six until I got it coll.You have to be steady as you do this then when you determine which direction your reflected vanes must be shifted to be in line with the actual vanes you can use the col. screws to make the adjustments.On mine the screws opposite of the of the direction I wanted to move the toward I would tighten..After you adjust it and see which way it the reflected image of the vanes move it will be easier to get them to line up. It helps to have a light illuminating the white paperboard and a light illuminating the back of the sec. mirror holder. This will require patience but once you get the hang of it you will be able to coll. the Mewlon almost perfectly while sitting comfortably indoors.I hope this helps Dane