Ulhas, I don't think that you will be able to control the depth that accurately. I would go as close as possible but leaving it slightly on the shallow side....
Hi Jacques, Yes you can do this but there is a real high chance of striae in the resultant blanks, this comes from re-melting glass, it's just a fact of life ...
G'day all, I'm in the design stage for my scope and observatory. The scope is a DK Cass. 12.5" F16 with f4 primary. I have the optics, however the original...
H Hi.I have been making telescops for 15yrs or so and will enjoy this . But not computers? Today if you want to build yer own scope it"s easy .Go back to 1989...
A fork wouldn't be a bad solution as it's not hard to make the fork as strong as it needs to be. Anther option might be some form of English yoke or horseshoe...
... Lowrey ... Awesome! I'm betting Jimi doesn't drive an sub-compact car though. Will there be oxygen available due to altitude at the focuser cage? Jimi,...
Hi All, Sorry to ask this here, but I need a bit of help with a new application I'm trying to implement on one of my websites, so if some one wants to give me...
Hi all, would it be worth the effort to make a test flat (12") for auto collimation test? I thinking for one to optimise the DK mirror set spacing I have. I...
No, a solar filter will not be flat enough. Making a quality 12" flat is no small task and I wouldn't think it would really be worthwhile for a single project....
... "Flat" is actually not super important for an auto-collimator, from what others tell me the math works out that the flat must be flat to within something...
Tony, " all you need to know is the is roc of the primary and secondary and the level of correction on the primary." Well, the secondary is n:4 and the...
What's N:4? I need the radius of curvature of the secondary. The primary-secondary spacing is very sensitive to that figure. The only easy way you can get that...
Tony, I'm sorry but my English is less than perfect (have a chuckle...) What I mean the secondary magnification is 4 times, the original spec is f16 for the...
... You might have a look at: http://users.rcn.com/rflrs/twomirrors.htm It would indicate that you need the system f/# (you have that), the secondary ...
I just listed a 15" F/4.5 blem on eBay. The mirror has a small chip in the edge. Otherwise, it's brand new with a fresh enhanced aluminum coating. Here's a...
I had bought a Jaegers 4.25" F:8 mirror back in the 1970s when I knew nothing. But 15 years or so later I temp rigged it in some shipping tubing and a pipe &...
Ok, given all that and figuring on a back focus distance of 200mm from the front surface of the primary I get the following: Effective focal length = 5080 mm ...
Thanks Tony, if I get a spherometer (?) perhaps I can confirm the roc's but how to evaluate the "primary conic" ?? This is the reason for me to try to find a...
... As long as you have the spherometer, why not measure th RoC of the secondary as well. Then, letting S = r2/r1 (pretending both are positive), T = M * S /...
That spherical 4" F/10 will work ok but it won't be a match for a top quality APO. Even at F/10 it still needs a touch of correction to really get the most out...
I think your best bet would be to set it up with an artificial star. It would need to be at least 100mtrs away and should be a hole that is smaller than the...
That sort of mirror interests me too. The rayleigh limit for a 4ins spherical mirror is F7 ie 1/4 wave error in the wave front. F10 should be well over the...
... I've put a star next to everything that changes. Rather then trying to get a large flat maybe you can find someone locally who makes mirrors and get the...
The spherical version has a Strehl ratio of about 0.90 on axis (mirror alone, not including the obstruction effects) but the diffraction limited FOV is very...
There is on other thing to keep in mind about these so called spherical mirrors. That is they will not be perfect spheres. At least the Jaeger I tested from...
Dale, Very sorry! At least you got one offer that I recall. Would you like to measure my quartz? I'm not using it until next year. The 4" is not coated so I...
Yes an f10 mirror is reall good as the first scope I made was a 10 inch f10 newtonion (only because I came across a 10in tool and blank) and that scope still...
OK I get it, using glass solar filter for testing mirrors is not a good idea. But how about using them for optical window? For Newtonian and Cassegrains. ...
