I've never been there but the gregorian has much to offer really. A simple definitive test for the 2ndry with no shadow guessing at all. All gained by a tube...
I would only ever use a slit and a sensible hole size in a foucault tester. That way the source is adjustable and diffraction effects can be made use of when...
Planewave in the U.S. makes CDKs and use a 3 element Keller corrector to give a wide flat field. They are typically about f/6. I've been considering making one...
My understanding is that on a Newtonian scope the primary image plane is 10 mm further from the primary mirror with the MPCC compared to without the MPCC, and...
I've got a 12.5" F/24 DK Cass. in the BigEye shop right now. These are reasonably easy to make with an under-corrected primary and spherical, convex secondary....
I've recently experienced the problem with shorter focal lengths for visual use. I've read about it in several places. I've been using an f9 apo for some time....
Hi Tom, you peaked my interest in knowing the difference in backfocus when using the MPCC. I am currently making an adapter to try the MPCC on my 8" C8 F1.9...
Not too long ago I saw an add somewhere for a Telrad mount extension that moves the Telrad farther from the OTA. I've been looking for the add in all of my...
Hi Tony, Gregorian? Who would want that? An right side up image? Yuck! VBG IMO the Gregorian does offer the advantage of the easier task making the concave...
Since I'm on the commercial side I always tend to look at designs in terms of not only optical performance but also in terms of fabrication time and customer...
... How would the diffraction effects be useful? I have only ever seen them make the Foucault image dim and flatten out and create rings close to the edge. ...
Thanks Richard! I am making a 10" Newtonian and the difference in backfocus would mean f/3.9 verses f/4.1 for me, and whether or not I have to cut 0.25" off...
Hi all - planning to buy scope for subj purpose.Thinking of Maxutov for portability (or other folded optic design). want to be able to see Jupiters bands and...
John, Singlemode or multimode refers to the number of ways the light can go through the fiber. It all has to do with the ratio between optical width of the...
Hi Tom, by adding antireflection coated optics like the MPCC you limit your UV utility for the Newt to ~350nm. One of the minor reasons I am building another...
Richard, You might take a stroll over in the new Yahoo Astrograph group for some ideas. Your 10" f/3.6 mirror would make a dandy primary for a Rosin...
Whew... Now that we all have a college edumakation on single and multi-modes, let me just say that I use fiber optical cables at work to feed signals, 2-way,...
The useless diffraction effect is the ring that can appear on the rim of a mirror just prior to total extinction making it difficult to see what's going on...
Well, I guess the nature of light really hasn't changed over the years. The standard shop tests that most of us use are certainly adequate to produce a high...
Kind of minds me of a forum topic a long time ago (a different group). It was about the best way to cut foam for eyepiece boxes. Went on for weeks, freezing,...
this (((((((((Sometimes the KISS principle is the best.))))))) is probaly and english expresstion can you more elaborated on just for my personal instruction ...
I'm very sorry, Ken, if it is taken too far for you. John asked about the difference and I tried to explain. It is just not as simple as you suggest it to be. ...
That is the hartman photographic test just done with a digital camera. Think it's a bit over the top with hole size and number though and could be improved. ...
ok okOK lot of reading and experiment to do for week THANK ALOT TONY jack 47'N 71'W ... produce ... edge, ... With ... chopped ... locating ... from ... ...
Me thinks KISS needs to be modified a bit. Keep is simple but just as complicated as needed to do the job to what ever lack of perfection is wanted. John PS I...
Hi John, It seems to be working fairly well as is. Even though the holes are small there's enough light if you use A DSLR to capture the image. The only real ...
