Dear ATMs,
The parabolization of the 24 inch mirror continued. After nearly 5 hours of parabolization by the 14 inch lap, there was only little progress recorded. We think that it is high time for us to prepare the 9.5 inch parabolization specialized lap.
The second Foucalt test was also carried out and the result showed that the mirror was still an oblate spheroid, with a little bit corrected towards a sphere. It showed that the 14 inch lap was of very low efficiency when used as a parabolization tool.
At the moment we are still employing a simple Foucalt test to guide the figuring. Later we will proceed to use the Dall null test and figure the mirror against the Dall null tester. When we get a null figure we are close to a perfect paraboloid and we will switch to the Offner tester to finalize the figuring process. The star test will be the ultimate judge. We do not use the Offner tester first because it is still not yet calibrated. Only when the mirror surface get very close to perfect paraboloid do we use the Offner tester with confidence.
This is only the beginning of the final stage, we set no time limit to end this up.
Best regards
Chan Yuk Lun
14-3-2004
Parabolization of 24 inch continues
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- 註冊時間: 週四 09 10月, 2003 21:06
Parabolization of 24 inch continues
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- One of the telescope making team member trying hard to parabolize the mirror.
- parabolization.jpg (66.58 KiB) 已瀏覽 10976 次
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- The 24 inch mirror was set up vertically waiting for the Foucalt test.
- upright_3.jpg (48.46 KiB) 已瀏覽 10976 次
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- The Foucalt tester, a simple torch with a slit produces the light source, the knife edge is at right side.
- tester.jpg (52.79 KiB) 已瀏覽 10976 次
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Re: Parabolization of 24 inch continues
More pictures to come
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- The Foucalt test setup, notice that the mirror is at far side. As the mirror is really big the only feasible way to set up the test is onto the floor.
- Foucalt_test.jpg (39.49 KiB) 已瀏覽 10974 次
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- Proceeding to test the mirror, just like a soldier engage in a field battle.
- D_Day.jpg (37.49 KiB) 已瀏覽 10974 次
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- What we see under the tester. Obviously the mirror surface is an oblate spheroid, we may consider it just an opposite to a paraboloid.
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Dear Miss BeanKitty,豆豸苗 寫:嘩. 咁反光, 我諗好天的話都可以羅出去睇下個月亮?
The mirror, if not coated, reflects only 4% of incident light. However even accounted for that the uncoated mirror has a light grasp as same as that of a 4.8 inch refractor. So the telescope can be used to view all Messier deep sky objects, even un-aluminized, not to mention the moon and planets.
Best regards
Chan Yuk Lun
15-3-2004
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