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- 12.5" -
|
STYLE |
THICKNESS |
WEIGHT |
|
full thickness |
2.20" |
24 lbs |
|
thin |
1.50" |
17 lbs |
|
conical |
2.125" |
13 lbs |
|
cellular |
2" |
7-9 lbs |
|
|
|
|
|
- 20" -
|
STYLE |
THICKNESS |
WEIGHT |
|
full thickness |
4.00" |
148 lbs |
|
thin |
1.85-2.0" |
45-50 lbs |
|
conical |
3.25" |
48 lbs |
|
cellular |
3" |
27-30 lbs |
|
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In reality very few full thickness mirrors are used
on projects, unless they are under 10" in diameter or are
used in an optics shop as a collimation flat or sphere. |
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As far as an optic reaching equalibrium is concerned,
the charts above list the mirror types by how fast they take
to equialize to ambient temperatures. Full thickness mirrors
take the longest, while the (opened sided) cellular take the
least amount of time. Only when an optic has reached equalibrium
can it take full advantage of its optical quality. The less mirror
mass, the faster it will reach equalibrium. |
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It cannot be stressed enough that the best optical
quality a given mirror can produce will not be realized until
the optic(s) has reached thermal equalibrium. The most exotic
or expensive glass (or metal) type in existance cannot get around
this fact. Until it has equalized, the images will be deteriorated.
Even seemingly minute differences (0.5C) in the glass versus
surrounding temperatures can degrade image quality. |
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Everything around the primary mirror influences the
cool down time also. The mirror cell material and design. A closed,
full length tube versus a truss design. The amount of space between
the edge of the mirror and the wall of the OTA. All of these
factors can be designed to maximize thermal characteristics,
which in turn helps optical quality. |
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