Orange Tube C8, Tasco 7te-5, 4" Criterion Dynascope, Jason/Towa 313
Nikon Action Extreme & Pentax WPii Binoculars
At my club, everything one could want up to 18"
Quote:Is the cat's-eye shaped field stop in sharp focus or blurry?
Quote:There is definitely a problem somewhere.
Quote:Can you see anything out of place looking through the tube without diagonal and eyepiece?
Quote:My baffle tube is melted, probably from solar viewing somehow I guess. Not bad, I marked it with a B in this picture. But check yours for any damage:
Quote:...the above photo is a Coyote at about 200 feet.
Quote:Joe a star test may show a problem... Try it without the diagonal first.
Quote:Your not concerned with optical quality right now just the optical alignment.
Quote:I don't know what the 3 little screws are for. I think you are right though collimation.If I remember right the meniscus lens up front just has 3 tiny little set screws holding it in the tube, I don't think any adjustments can be made there but a blow to the meniscus could knock it out of alignment very easily.All these things will show up in a star test.I went back and looked at your photos and I'm not sure what is holding the meniscus in the black tube. I don't see the set screws on the outside.Robert
Charlie NR1Q - Retired USAF Optica b/c 76x1200, Swift 831, Sears 6339-A, Sans & Streiffe 618, Mayflower 816 Astro Optical S5, Monolux 4380, Space Scope 60x910, Tasco 7T, Aerolite 859, HyScore 417, Manon 60/700 Cartonesque 60x1000, Sears 4451, 6331, Tasco 9VR 50mm HyScore #457, Unitron 105, Tasco 66TE, Tasco Terrastro 50/600, Tasco Deluxe 50/600, Bushnell Space Rover 50/500 40mm Asahi Jupiter, Astro Optical R-41, 40mm SPI #523 Optica b/c LN-4E
Quote:Is there an official way to collimate these old C90s? I saw the retrofit way described in this thread, but would happily try something easier first. Images of stars are not sharp. Daytime images are partly clear, partly slightly fuzzy in different parts of the field (not due to objects being at different distances). Seems it should be able to be better than it is. What a lesson in the importance of contrast! Images are bright, but not vivid, the compromise for having so small a scope. Fun gizmo. Hate the finder. Even a tiny scope needs a right angle finder. Needs a good tripod and mount. Any recommendations? Homebuilt is in the budget, but Vixen Porta Mini might be great. Other ideas? Something lightweight and portable, good for birding or light astronomy.
Uncle Rod Uncle Rod's Astroblog: http://uncle-rods.blogspot.com/
Quote:Believe me, collimating these little scopes is not for the faint of heart, and it is fairly rare for one to be out of collimation.
Quote:You can't tell by how "sharp" stars are, you must observe the diffraction rings of a just slightly out of focus star under good seeing with said star centered.
Compustar C14 Leo Henzl's Custom C8(VP Sales Celestron) Celestar C8 6" Refractor Adv. GT mount 6" F5 Omni XLT Newt. LXD-75 F4 Imaging SN8 Meade 8" F6 Newtonian Dynamax DX6 Criterion RV-6 ETX-90 Astro Meade 2045 4" SCT B&L 4000 Vixen/Celestron 80mm F11 JC Penny 60mm AZ/ALT Refractor 1963 60mm 15-60 B&L Spotter Binos 25x100 8X40 20x80 Arcturus Bino-Viewer
"Head" proprietor of the Toilet Observatory.
Quote:Joe,You can get an LAR here:http://www.cncsupplyinc.com/index.htm?etxstuff.htm for $29.95 plus shipping.I bought one for my black C90 earlier this year and it works fine.
Quote:Have you also tried peering into the exit pupil from a rakish off-axis angle?... this has the effect of you viewing the optical system from the focal surface but offset toward the field edge... look into the exit pupil from an angle near or equal to the semi-angle of the eyepiece's apparent FOV...