Madukar, I have not seen any progress reports on figuring your mirror lately. Any work still being done on it? Dale Eason...
21350
art.bianconi
Jun 4, 2012 11:53 pm
Prior discussions regarding the need for Blanchard grinding have me wondering what it is I might do on my own with one of my mirror grinding benches to create...
21351
Madhukar Bhatia
madhukar_bhatia
Jun 6, 2012 6:42 am
Hi Dale, Thanks for checking. I have been very busy with my son's college admissions and haven't got much time to work on the mirror. I have got a few sessions...
21352
Orly
orly_andico
Jun 6, 2012 10:48 am
Any updates on this? the Edmund Optics 2" x 2" hot mirror is only $49 - much less than what Newport is asking. I'm also thinking of getting into this because...
21353
Mark Christensen
mjcw500@att.net
Jun 6, 2012 3:27 pm
If I was going to try this (I'm largely a Newt Man right now) I'd buy an Orion (or other) 1.25 inch flip mirror and replace the mirror with one of the hot...
21354
art.bianconi
Jun 7, 2012 5:36 pm
Applying Stepper Motors- Application Questions You Must Answer and Things to Watch Out For Live Presentation: Tuesday, June 26, 2012, 2:00 pm ET Sponsored By:...
21355
art.bianconi
Jun 9, 2012 4:41 pm
When an opportunity came to purchase some new, name brand (Hasselblad), large camera filters at a very good price, I grabbed it for use on my refractor. ...
21356
atmpob
Jun 9, 2012 7:59 pm
Why don't you try an experiment and see? You can even try it during the daylight on a faw away object. Choose a high power eyepiece and try them them out....
21357
art.bianconi
Jun 9, 2012 9:06 pm
Dale suggested: "Why don't you try an experiment and see? " Hi Dale! I do not trust my visual accuity for the test you suggest. I figured that a side by side...
21358
Francis Smith
smithgene69
Jun 9, 2012 10:23 pm
Good idea Dale, but by far the most distortion free conditions for me has been well after dark, when the air is still, and over lawn that was perhaps tree...
21360
farleyhillbilly
Jun 10, 2012 3:32 am
... One last go at this. Amateur Telescope Making Book 1- Ingalls A. G. http://bib.tiera.ru/b/78674 Amateur Telescope Making Book 2- Ingalls A. G. ...
21361
Mark Christensen
mjcw500@att.net
Jun 10, 2012 7:01 pm
Art, The closer the filters are to the image plane, the less critical they are. So if you put the filters right in front of the camera, after all the optics,...
21362
atmpob
Jun 10, 2012 7:55 pm
If you can not see any difference then for you they are fine and there is no issue. Seems to me if you can trust your visual accuity to make that kind of test...
21363
atmpob
Jun 10, 2012 8:06 pm
One does not need distortion free conditions. Poor quality filters will add to the stack of aberrations and reduce the power that can be used even more than...
21364
trulyyours05
Jun 10, 2012 8:48 pm
Dale, there are a couple of problems with this example. First, ordinary window glass is relatively horrible, I mean really bad, as optical glass. Second, the...
21365
farleyhillbilly
Jun 10, 2012 9:42 pm
... Homebuilt Reflector Telescopes by Sam Brown http://www.scribd.com/doc/16653338/Homebuilt-Reflector-Telescope...
21366
art.bianconi
Jun 11, 2012 12:54 am
Hi Mark! You wrote:". . . . . if you put the filters right in front of the camera . . . . " These are 77 mm filters Mark and were purchased for use ahead of...
21367
Ali Khan
ak6666666
Jun 11, 2012 5:08 am
filter at ep end gives much less distortion. ... From: atmpob <atmpob@...> Subject: [atm_free] Re: Filter Quality: Astronomy filters versus photography...
21368
Jan van Gastel
janvangastel
Jun 11, 2012 12:03 pm
A mirror should have a surface as smooth as possible. But how rough is too rough, or stated otherwise: is visible in the eyepiece as a los of contrast. I...
21369
atmpob
Jun 11, 2012 1:44 pm
The point was not to compare window glass to optical filters but to demonstrate how poor filters add to the seeing problems. Dale Eason...
21370
farleyhillbilly
Jun 12, 2012 12:30 am
... Dont know if you would be interested in this, but, there is an art glass workshop/ supplier that has didymium glass sheet for 29$ for 4lb. Glassblowers...
21371
Mel Bartels
Mel_Bartels
Jun 12, 2012 2:06 am
It's a little rough. Hard to quantify at the eyepiece, but I wouldn't accept if my mirror. It would be instructive to see an interferogram to see how much the...
21372
trulyyours05
Jun 12, 2012 2:24 am
I get what you mean. Al...
21373
Jan van Gastel
janvangastel
Jun 12, 2012 7:21 am
Will that not ruin the figure? It has a Strehl of 0.972 now (measured interferometrically) and I wouldn't like to have to start all over again. Jan ...
21374
mbartels@...
Mel_Bartels
Jun 12, 2012 8:09 pm
... Hopefully not! The idea is to smooth the figure without changing it. I've had very good luck with this approach. I go all the way down to 20 second...
21375
Jan van Gastel
janvangastel
Jun 12, 2012 8:42 pm
OK. Do I do this with a full size lap, or is it also possible wit a sub diameter lap (sub diameter would be easiest, because I have laps from 100 to 220 mm ...
21376
mbartels@...
Mel_Bartels
Jun 12, 2012 10:43 pm
... As a general rule, larger laps tend to produce smoother surfaces. If attempting a sub-dia lap, then scallop or star the edges. Yes, wire brush or press the...
21377
art.bianconi
Jun 13, 2012 3:56 pm
Of all the techniques taught to me by master mirror makers, the one that proved to have the most dramatic effect on surface quality was speed. Moving a tool...
21378
Jan van Gastel
janvangastel
Jun 13, 2012 5:18 pm
My parabolizing speed (on the machine) is 51 strokes per minute. I can slow it down easily with my variabel frequency drive. The larger the mirror, the faster...
21379
Mark Whitaker
tnut55
Jun 13, 2012 5:34 pm
That's pretty high. In the Zambuto figuring example for a 12.5" mirror, the eccentric is typically less than 20 strokes per minute with larger laps and maybe...
