Does anyone use these materials, I'm looking for a 10" dia. blank and wonder if there are any reasonably priced sources? Thanks Don...
14480
gyouman
gyouman...
Oct 1, 2009 7:43 pm
goggle zerodur and astrosital. all kinds of info on properties and sources. ... -- Glen Youman Penryn, California http://www.astrophotos.net...
14481
Astronomer Bilal
astronomerbi...
Oct 2, 2009 6:10 pm
Hello I have started making my 8" 19mm mirror grinding project. I have done almost 1.5 hours of work until now but I havent seen a curve or depression yet in...
14482
Vladimir Galogaza
vgalogaza
Oct 2, 2009 7:16 pm
Hi Bilal, ... Please describe your grinding procedure so that somebody can comment on it. Regards Vladimir....
14483
Mark Whitaker
tnut55
Oct 2, 2009 8:08 pm
Someone else commented on this but I'll ask as well. What abrasive are you using? What type of hogging stroke are you using? What are you using as a tool? ...
14484
glasspusher2001
Oct 2, 2009 8:46 pm
What are low cost sources for Pyrex blanks? I can think of William Bell and Newport Glass. United Lens is more expensive. Don...
14485
Exitar01@...
exitar01
Oct 2, 2009 8:48 pm
try gotgrit.com ... From: glasspusher2001 <glasspusher2001@...> To: atm_free@yahoogroups.com Sent: Fri, Oct 2, 2009 1:46 pm Subject: [atm_free] Pyrex...
14486
gyouman
gyouman...
Oct 2, 2009 9:04 pm
Google 'pyrex mirror blank' - plenty of info ... -- Glen Youman Penryn, California http://www.astrophotos.net...
14487
David Adams
elrey3141592...
Oct 2, 2009 9:26 pm
Swift Glass in NY was the best I found. (Google it.) ... From: glasspusher2001 <glasspusher2001@...> To: atm_free@yahoogroups.com Sent: Friday, October...
14488
Astronomer Bilal
astronomerbi...
Oct 3, 2009 12:22 pm
Sorry people I forgot to mention that. I was using Chordal stroke with 50% overhang and #80 grit, with a glass tool, and couldnt get depression in 1.5 hour But...
14489
Mark Whitaker
tnut55
Oct 3, 2009 1:38 pm
Let's review the chordal stroke. If it is not working for you, then you are most likely not doing something right. 80 grit is fine but 60 grit will work much...
14490
Joe
nssdz
Oct 3, 2009 3:45 pm
... Wet the mirror with some soapy water and focus the sun onto a piece of paper. Viola! thats your focal length. If it's cloudy or nighttime,, set up a...
14491
Ali Khan
ak6666666
Oct 3, 2009 5:35 pm
Dear Mark and others, I am coaching Mr. Bilal via sms. We are some 1000 kms apart. He has found himself in a slight problem. I am perplexed how to get him out...
14492
Mel Bartels
Mel_Bartels
Oct 3, 2009 6:20 pm
1 Should he do more 50% chordal till tool edges are ground down as much as 1.27mm? Yes 2 Should he use hammer all around the tool alone to bring down the edges...
14493
Mark Whitaker
tnut55
Oct 3, 2009 8:19 pm
That's a problem with beginners. They are quick to try something without understanding what the results will be and how to avoid getting into trouble in the...
14494
Jerry
atc322asd
Oct 3, 2009 9:55 pm
Wow! That took a while to come in on my 2800 baud connection. J Jerry ... From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com] On Behalf Of Mark...
14495
Charles Mitchard
charlesmitchard
Oct 4, 2009 9:47 am
Hi, in a star test one looks for the rings that form on either side of focus. (and hope they are the same) What does it mean if you cant get the rings? Thanks ...
14496
Arjan te Marvelde (he...
atm_6_6_6
Oct 4, 2009 10:17 am
Joe, This will only work when you have mating tool and mirror, i.e. during fine grinding. A hogged-out blank may produce some image, but the shape is usually...
14497
James Takac
p3nn_drag0n
Oct 4, 2009 10:25 am
... Hi Charles If like me you are using a refractor type telescope, i.e mirrors instead of lenses the you wont see rings. What you see instead is the shadow of...
14498
Terry Trees
terrytrees
Oct 4, 2009 11:25 am
I think James meant reflectors mot refractors use mirrors. In my reflectors it generally means you need to use a higher magnification. Terry ... From:...
14499
James Takac
p3nn_drag0n
Oct 4, 2009 12:35 pm
Hi Terry Yes, you caught my error there. Newtonians and such using mirrors are reflectors and typically don't seem to display diffraction rings from my ...
14500
Jan van Gastel
janvangastel
Oct 4, 2009 1:19 pm
Yes, mirrors do show diffraction rings, just like refractors. But they do also show the shadow of the secondary mirror centered in the rings. To see the rings...
14501
James Takac
p3nn_drag0n
Oct 4, 2009 1:44 pm
Hi Jan That would seem to explain why I've never seen the diffraction rings then, i.e. not enough magnification when I was doing it. So for my 76 mm newt a 4 ...
14502
Jan van Gastel
janvangastel
Oct 4, 2009 2:22 pm
I think 175 x will be enough and maybe around 80 x already shows the rings. Jan http://members.ziggo.nl/jhm.vangastel/Astronomy/ ... From: James Takac To:...
14503
bgnirrep
Oct 4, 2009 2:41 pm
I am planing to make a diagonal holder and spider like Toshimi Taki's see http://www.asahi-net.or.jp/~zs3t-tk/8inch/8inch.htm for my 8". I was wondering if any...
14504
catboat15@...
olewilly2000
Oct 4, 2009 4:03 pm
Hold on a bit. Don't try any "hammer heads" or local tools to put a pit in the middle of the mirror. Now you have a "hole" so go to the grinding with mirror...
14505
Mel Bartels
Mel_Bartels
Oct 4, 2009 5:12 pm
Curved spiders are fairly popular over the past few decades. I've used 1/8 inch thick x 1.5 inch wide aluminum curved for me at the local machine shop. This...
14506
Ali Khan
ak6666666
Oct 4, 2009 6:01 pm
I want to say thanks to everyone on Bilal's behalf. He is doing COC 1/3 with tool and mirror. Things should turn out ok for him, I am pretty optimistic. He has...
14507
Mark Whitaker
tnut55
Oct 4, 2009 6:24 pm
He just needs to keep after it until he achieves full contact. He'll wear down the outer edges of the tool and associated sections of the mirror first. This...
14508
Ali Khan
ak6666666
Oct 5, 2009 3:51 am
Thanks. He found sag to be too shallow. Ok he will continue COC 1/3 with grit 80 till he gets required sag.   Thanks again  Have a great day.  Ali ... ...
