From memory there is a paper by Couder on the subject but pass on where and when I read it. Seems that anything affects the light in the central spot. It went...
... Hi Phil, It kinda depends on the size and weight of the DOB, but what I do is use one of those target shaped bubble levels to level my groundboard. I am...
I'm always a bit queasy about papers like that Tony. Shading must be one aspect but if the diffraction spikes can be seen the light has to come from some...
The main impression that I took from the paper is that vane area and shape is what really matters. Taking everything they state at face value the best choice...
Thanks to Tony for posting that paper. The other day I was trying to use OpenFringe to predict the performance of the MMT we talked about recently. To test...
at the time a made my curve spider I do not know howto only ear soembody speaking about and my version is a bit new I only made a circle of 12 inch ( my...
In ATMJ #11 (reprinted in WillBell's tbe best of ATMJ vol 1, p.385, if anyone has it) is an article by Suiter and Zmek, "A Dialogue on Spider Diffraction"...
... It turns off I wasn't off by a factor of two, so my corrected diagrams are wrong. To interpret them correctly, consider them to be from an 8" scope...
A great advantage of extremely thin vanes or wires, and unachievable with curved vanes due to physical limits, is that as the vanes are made thinner the...
Mark, ... I could probably push it to .001 of the primary diameter. The R implementation of FFT isn't constrained to powers of 2 in size, but the upper limit...
That's right, the energy is less and it's spread over a much larger area making it's impact on extended object contrast very low indeed. I've wanted to do a...
Steve, You should be able to find what you need here: http://apollo.sese.asu.edu/ Tony BigEye Optics ... From: "Stephen Koehler" <s.c.koehler@...> To:...
Hi Guys I I feel a bit reluctant to join in this discussion mainly because all you guys seem to really know your stuff, but there is one thing that i would...
I can think of a couple of reasons. First is cost, you can't use just any old bit of glass for this. It has to be optically clear and uniform and have a good...
Mick, ... Here are some reasons I can think of: pros: - gets rid of diffraction spikes from the spider - perhaps keeps primary cleaner cons: - expensive to...
Mark, Thinner is better... maybe not. You not only have to make sure the wires are strong enough to hold the load, they have to be strong enough to make...
Mark, That is not at all a dumb question. This is sometimes done. A glass plate holding a secondary is called an optical window. An additional benefit is that...
So in short it causes more problems than it solves and thats without mentioning the cost. Well i just had to ask. Cheers guys Mick ... From: Al Germaine To:...
Not that it causes more problems. It's that there's a trade off. Some people use them. Al ... - how measured? ... will ... an 8" ... simulation, ... have a...
I think I should mention that for larger scopes, wire makes less sense because the load goes up with the cube of the size, so the wire diameter outpaces the...
The main thing is cost. It doesn't have to be flat but the thickness needs to be very even and it needs to be made of a decent optical glass. The surface can...
Getting IR coating done can be a big issue. A lot of companies will try to charge you well over $1000 for something like that. You have to hunt around and find...
lol....geeezzz....read IR as AR please. Tony ... From: "Tony Gondola" <acgna@...> To: <atm_free@yahoogroups.com> Sent: Wednesday, July 02, 2008 8:59 AM...
Hello I was running the excellent simulation program 'Diffract' to compare the shadows I see on my 158 mm f 4.5 mirror,when a doubt arose. In diffract which...
I don't know if any one on here knows how AR was done some time ago but I would love to know too. I've tried searching several times. It seems it can be done...
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