I cant see any downside to removing / reducing the boundary layer: It does a few things: 1) Helps cool the mirror faster 2) Helps keep dew from...
20206
garyk9rx
Apr 21, 2012 3:42 pm
correct me if I'm wrong but I think you're missing the biggest reason of them all... when Bryan Greer had published his article regarding mirror cooling my...
20207
Tim Ulmer
tsulmer1
Apr 21, 2012 6:26 pm
Gary wrote: the fact that this boundary layer exists says that the mirror is hotter than its surroundings The existence of the boundary layer says nothing...
20208
walter kennison
walterkennison
Apr 21, 2012 9:21 pm
Had to read all of this twice :)  The heat of the mirror and differential creates the boundry layer,, the cooling effect of the mirror and its inside...
20209
ceroxyd
Apr 21, 2012 10:27 pm
I'm from Germany and new on the list, but I'am reading here for a while. Here in Germany we are on short supply on thik mirror-blanks and so we use Schott...
20210
walter kennison
walterkennison
Apr 21, 2012 11:28 pm
neat design,, wish i was better in german...  polishing with an interferometer how is that done,,, is it an active process or periodic checks  wally ...
20211
garyk9rx
Apr 22, 2012 1:50 am
I'd agree entirely - it might be semantics but of course there is a layer of transitional air - I call it boundary layer - that has to exist if the mirror is...
20212
Tim Ulmer
tsulmer1
Apr 22, 2012 3:17 am
Gary, I think your post helped me understand what Wally maybe have been saying - and it's different than what I have been trying to explain. 1) If I...
20213
walter kennison
walterkennison
Apr 22, 2012 3:36 am
your absolutely right,,, the boundry layer exist,as in aviation,,, nevertheless its effect on the mirror and optics is dependent on the humidity and...
20214
Robert Bunge
bungerob
Apr 22, 2012 4:15 am
I'm likely barking up a different, and perhaps wrong tree here. I'm guessing most of us store our large dobs (ok, I'm defining this as something with a mirror...
20216
Neil
lowentress
Apr 22, 2012 9:11 am
Hi Kai Very interesting to see what has been done there with 25mm Borofloat, Do you know of people in Germany using the Suprax glass disks that are made there...
20217
garyk9rx
Apr 22, 2012 2:27 pm
Having a 30 in an observatory that is one thing I had always planned on doing. Putting in a portable AC unit with a hose to the mirror box with some sort of...
20218
walter kennison
walterkennison
Apr 22, 2012 2:44 pm
I would like to bring something up again,,, when we think of equalibrium ,,, we can separate two issues,,,and approach them separately for common denominators...
20220
ceroxyd
Apr 22, 2012 2:56 pm
Hallo Walter, it's done with Dale Easons OpenFringe Software. Interferometric test after every polishing session. It's very intuitiv und straight forward. ...
20221
atmpob
Apr 22, 2012 4:49 pm
For several years I have had a 16 x 1 inch mirror with a fan on the back and small 1 inch fans that blow across the font and so had not noticed the following...
20222
nwstars2002
Apr 23, 2012 2:16 am
I am traveling to Germany June 2 and will be in Berlin for the transit of Venus, do you know if there is a public viewing event scheduled for Berlin? Kevin, in...
20223
Neil
lowentress
Apr 23, 2012 9:13 am
Hi I prefer F5 because I think it is more feasable for me to reach a very accurate mirror surface 1/8 pv or better at F5 rather than F4 or even F4.5 I also...
20224
abellhunter
Apr 23, 2012 7:38 pm
BigDob group, this spring a 28" f4.1 Starmaster w/Kennedy optics has been installed in a new astro village 30mi south of Silver City, New Mexico. Last night...
20225
Ali Khan
ak6666666
Apr 24, 2012 3:11 am
Very impressive collection of pictures!...
20226
careysub
May 1, 2012 11:18 pm
The Cruxis Mirror Edge Support Calculator shows that two-point mirror edge support performs nearly as well as a 180 degree cable sling, with similar degrees of...
20227
Jan van Gastel
janvangastel
May 2, 2012 6:24 am
It is much easier and better to make supports that support the mirror exactly at the COG plane then making the 'line supports' you suggest, because for such...
20228
Robert Houdart
rhoudart
May 2, 2012 8:22 am
Jan is spot on. With a cylinder support, how can you guarantee that the support is perfectly distributed over the thickness of the mirror? Take into account...
20229
tsulmer1
May 2, 2012 9:18 am
Hey everyone. I have acquired some PTFE strips 1/8" thick x 1" wide x 9 ft long. I can cut these into any length you desire. And if you need 3/4" wide, I...
20230
dobson 2005
pierredesvaux
May 2, 2012 10:09 am
As for edge supports, having tried many systems, including cable slings, I now use 2 ball bearings, the axis of which is horizontal. In this case, the contact...
20231
Jan van Gastel
janvangastel
May 2, 2012 10:17 am
Another solution is to place the supports on the part of the mirror cell that moves with the mirror when collimating. They will always stay in place that way....
20232
careysub
May 2, 2012 11:47 am
... Yes, I built a 13.1" mirror cell that does exactly that also. Here is the key motivation for this question: sandwich mirrors. Hubble Optics or Normand...
20233
careysub
May 2, 2012 12:34 pm
I just unboxed the newly arrived Hubble Optics 18" mirror and find that the bottom mirror disk is smaller than the top disk. It the top is 18", then the...
20234
Robert Houdart
rhoudart
May 2, 2012 12:39 pm
If a support at the COG is impossible, you can directly support the edge of the front and back plate if you make sure that the load is correctly distributed...
20235
Nils Olof Carlin
nilsolofcarlin
May 2, 2012 2:20 pm
Carey, ... cylindrical supports, would seem to support mirrors quite accurately for the tests to be useful. There have been many very good replies already....
20236
atmpob
May 2, 2012 4:13 pm
I just did an interferometry test on an 18 inch HO mirror and I was worried about how to support it on the test stand. Turns out the mirror had much more...
