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...
20237
careysub
May 2, 2012 4:47 pm
Do you know the exact focal length? That would tell us if it was the same mirror. It doesn't matter is this particular mirror is not up to snuff (I'll be...
20238
dobson 2005
pierredesvaux
May 2, 2012 5:12 pm
For Hubble Optics mirrors or similar ones with 2 plates, the best is to make two vertical weefle-trees. For each weefle tree, put 2 rollers or ball bearings,...
20239
careysub
May 2, 2012 5:59 pm
Thanks - I think the vertical whiffle tree you refer to is the same as the pivot arm scheme I was beginning to settle on. A pivoting arm, with pivoting...
20240
careysub
May 2, 2012 10:08 pm
I just did a check of refiguring prices - and even if I had the mirror refigured by Steve Swayze (which in my book makes it premium) the combined cost of the...
20241
Tim Ulmer
tsulmer1
May 3, 2012 12:54 am
Yep. I bought a 16" HO and had it refigured to premium (0.97 strehl) and took care of the turned down edges etc. HO price plus refiguring was about 1/2 (HO...
20242
careysub
May 3, 2012 1:01 am
Who did your refiguring?...
20243
atmpob
May 3, 2012 2:05 am
3683 mm give or take 10mm. I forgot to get the exact ROC during Foucault testing. I would have gone back except the astig and surface roughness were the...
20244
Tim Ulmer
tsulmer1
May 3, 2012 3:39 am
Tony at Owl Optics. Apparently the Hubble sandwich mirrors are harder than normal to refigure for various reasons attributed to the sandwich structure. So...
20245
careysub
May 3, 2012 4:42 am
The label on the box says 71.39", which would correspond to 3627mm, so I would say not. One can discount their "S-Ratio" but I think their F.L. is likely...
20246
skies2clear
May 3, 2012 1:20 pm
That would seem worth it, however, how good is the substrate on these HO mirrors I wonder? I have no idea, but just curious whether it really is worth doing...
20247
careysub
May 3, 2012 11:31 pm
My thought - I guess I'll be finding out......
20248
Tim Ulmer
tsulmer1
May 3, 2012 11:33 pm
I have a 14" that I'm happy with. My 16 that was refigured tested excellent, but I haven't installed it yet. I have high expectations though... Tim in...
20249
careysub
May 3, 2012 11:36 pm
I will post an account of what I find, and what happens to this mirror regardless of how it turns out to do my part to avoid sampling bias (perhaps bad mirrors...
20250
Denis
denisbroad56
May 9, 2012 9:34 pm
Hi I'm thinking about getting a 25+ inch dob but one topic that I can't find much info on is the process of installing the heavy mirror into the mirror box. ...
20251
C. Starks
cstarsnc
May 9, 2012 10:00 pm
Hi Denis, You didn't mention the thickness you plan to have, but if it is 2", then a 25" mirror will be heavy (F/5 Pyrex is 73 lbs.). I have a 20" F/5 mirror,...
20252
gsbertrand@...
g7l12e5n14
May 9, 2012 10:08 pm
Hi there When I clean my 25" mirror , yes it is a 2 person job , there is room but mirror should be on a small angle . And I have one rule , it doesn't matter...
20253
starryskyn
May 10, 2012 4:08 am
I have the 25 Obsession. The last time its mirror was lowered into the box, it was fairly easy for two of us, clearance was no problem. You can make a net of...
20254
Tim Ulmer
tsulmer1
May 10, 2012 5:46 am
I don't lower my mirrors into any mirror box. My mirrors are installed in the mirror cell while it is outside of the mirror box. Once installed in the cell,...
20255
Neil
lowentress
May 10, 2012 8:41 am
I totaly agree, My homemade telescopes have a desgn where the bottom of the mirror box with the mirror can be unbolted easily and the rest of the mirror box...
20256
Ross Sackett
rsackett00
May 10, 2012 12:56 pm
I use an improvised "cake stand" to load the mirror. In the plywood back of the mirror box I drill three large equidistant holes (this step isn't necessary...
20257
Steve Truittsm
stephmac20016
May 10, 2012 4:26 pm
Cool. Sent from my iPhone ... [Non-text portions of this message have been removed]...
20258
Robert Houdart
rhoudart
May 10, 2012 7:31 pm
Hello everybody, The 1100 mm telescope project we commenced in 2007 is taking a second start after nearly 4 years of interruption. See the web page for the...
20259
Shane LaPierre
ctastronomer
May 10, 2012 7:35 pm
Robert, I have been waiting to see the result of this for a while... although I am sure not as much as you! Thanks for posting this milestone, and glad you...
