Why so? Why are edges more vulnerable? Photoelectric effect?? Coating gets a charge from UV or something, pointed edges get greater charge density and some...
Hi Ali: Sorry. I should have given some detail on failure along a boundary. It's simply a matter of air, contaminants and moisture having direct access to the...
Thanks Ed, Stephen, James, Thats a lot of information. So the bottom line i gather is: it may not be worth the trouble or the expense to get a silver coating...
This group was not known to me until I looked up what a MPCC was; and sure as shootin' I really am glad to find it! You see, I was part of the FIRST group of...
If you haver ever rinsed a mirror then set it on edge to dry you will know the answer to this question and response. The water will start sheeting off the...
You might try looking for another group of Indian telescope makers, we've had a few here from time to time reporting on their successes, or look for help at a...
Concerning visible astigmatism in the Ronchi test, down anyone have a rough method of estimating the degree of deformation in waves? I'm not talking about the...
Tony, ... That's an interesting question. I assume you are testing a sphere, so the lines are straight. If the primary astigmatism is oriented at 45 degrees...
Stephen, Thanks for taking a look at this. Both approaches would be workable but I prefer inside/outside focus distances as that's not subjective. I see a lot...
somebody is able to tel me a lind of howto for ronchi test Where to place the ronchi where to place the ccd the setup resume in fact I read for long time but...
Tony, ... I agree that inside/outside focus distance is the way to go. If you're looking at mirrors for refiguring, then you are dealing with paraboloids,...
Stephen, For a general quick look I use a 100 LPI grating. I don't often see "s" shaped lines unless the astig. is very pronounced. A more common effect is ...
Thanks Ken, There are two commercial outfits here in Bangalore who aluminise. One of them does a poor job ive seen the coating is not uniform and there seems...
Jacques, On Tue, Nov 4, 2008 at 12:31 PM, Jacques Savard ... I'm not sure I understood all of your message, but Peter Smith has a very extensive site on the...
... wrote: The Ronchi screen replaces the Knife Edge in your Focault tester. To use it to find the null you move the stage just like with the KE and as the...
...of New Perspectives on Newtonian Collimation is now available. Information is available here: http://homepage.mac.com/vicmenard/telescopes/index.html The...
... You will get several answers but here is mine. I have a 3 point on my 10 inch F5 1 inch thick plate glass mirror and it seems to work fine. If I were to...
I'm building a 12'' dobsonian and I'll make a 9 point flotation system, so I believe you can also make a 9, but 6 will still be ok because your mirror is thin....
6 points http://www.atmsite.org/contrib/Holm/Plop_optimized_cells/design_space.html With 3 points, there is a chance you might see some observable deformation....
Leandro, IMO, you should use "Plop" to determine the wavefront error you can expect from a given mirror cell. I would not accept an error due to the cell that...
Hi Al, I'm using Plop and the 'Automatic Cell Desgin' for 6 point cell gives Visible PV error 4.82494e-06 Visivle RMS error 8.81301e-07 for 10"/1" f/D 4.7...
I get Visible RMS Error = 1.18643e-06 with P-P Error =5.59148e-06 for a six point cell My RMS is about twice yours, I don't know why. Perhaps you did the new ...
Hello I have come across a source in India where I can get thin , 3-5 mm thick , meniscus first surface mirror.These apparently are used in some opthalmologic...
Hi Ulhas, Alan Adler has made a computer program which calculates what is required in flexing the mirror. It is DOS program, for today's standards antiquated...
maybe you can find help ehere http://storm.prohosting.com/~lisaphot/gil/flex/index.htm they make a lot of but be carfull it could become a catanaway also jack...
Hi, I do not think you can get a useful image from such a thin mirror. Perhaps if you are keeping to very low magnification. It would be very sensitive to...
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