-----Original Message-----
From: Joe Goins
Sent: Tuesday, August 15, 2000 7:40 PM
To: 'Sam Michael'; Joe Goins
Subject: RE: ATM 12x12x0.8" astrositall blank
In what way is astrositall difficult to polish?
Joe Goins
-----Original Message-----
From: Sam Michael [mailto:samm@idcomm.com]
Sent: Tuesday, August 15, 2000 5:00 PM
To: Joe Goins
Subject: RE: ATM 12x12x0.8" astrositall blank
It grinds normally. It is just difficult to polish.
Sam.
-----Original Message-----
From: owner-atm@shore.net [mailto:owner-atm@shore.net]On Behalf Of Joe Goins
Sent: Tuesday, August 15, 2000 1:14 PM
To: 'Hugues_Laroche@ses-astra.com'; Joe Goins
Cc: 'atm@shore.net'
Subject: RE: ATM 12x12x0.8" astrositall blank
Hugues,
Thanks for the info. I'm not sure what you mean about taking astigmatism precautions. Would you possibly know the best way to hog out the rough curve? I hear this astrositall stuff is hard to grind.
Joe Goins
-----Original Message-----
From: Hugues_Laroche@ses-astra.com [mailto:Hugues_Laroche@ses-astra.com]
Sent: Monday, August 14, 2000 2:42 AM
To: Joe Goins
Cc: 'atm@shore.net'
Subject: Re: ATM 12x12x0.8" astrositall blank
>I have a chance to buy an 12x12x0.8 inch astrositall blank.
>What's the largest size mirror I can make out of it,
>because of it's thickness?
12". :-)
Take astigmatism precautions at fine-grinding and polishing.
I have a small program that gives you the sagitta, weight of the glass
calotte removed
to make the mirror concave, its weight, remaining weight (sorry all is in
centimeters and kg) ...
Better view this in non-proportional font:
Diameter = 30.48 cm
Edge thickness = 2.032 cm
Weight of blank out of PYREX = 3.306 kg
Weight of blank out of SITAL = 3.736 kg
f/d f sagitta thickness PYREX SITAL
@ center Calotte Total Calotte Total
1.00 30.5 1.91 0.13 1.56 1.75 1.76 1.98
1.50 45.7 1.27 0.76 1.04 2.27 1.17 2.57
2.00 61.0 0.95 1.08 0.78 2.53 0.88 2.86
2.50 76.2 0.76 1.27 0.62 2.69 0.70 3.04
3.00 91.4 0.64 1.40 0.52 2.79 0.58 3.15
3.50 106.7 0.54 1.49 0.44 2.86 0.50 3.24
4.00 121.9 0.48 1.56 0.39 2.92 0.44 3.30
4.50 137.2 0.42 1.61 0.34 2.96 0.39 3.35
5.00 152.4 0.38 1.65 0.31 3.00 0.35 3.39
5.50 167.6 0.35 1.69 0.28 3.02 0.32 3.42
6.00 182.9 0.32 1.71 0.26 3.05 0.29 3.44
6.50 198.1 0.29 1.74 0.24 3.07 0.27 3.47
7.00 213.4 0.27 1.76 0.22 3.08 0.25 3.49
7.50 228.6 0.25 1.78 0.21 3.10 0.23 3.50
8.00 243.8 0.24 1.79 0.19 3.11 0.22 3.52