DIY 7 inch Cassegrain telescope - 3, star test
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- 夸克星
- 文章: 3847
- 註冊時間: 週四 09 10月, 2003 21:06
DIY 7 inch Cassegrain telescope - 3, star test
Dear ATMs,
The purpose of making the tube assembly prior to the optics itself is to carry out star test. As mentioned before the primary mirror is already parabolic, the aim of the star test is to test the figure of the secondary.
Star test doesn’t need a real star. My target is a distant crystal chandelier. The reflection on the hanging “crystal” surfaces form perfect point sources.
The test result was short of surprising – the “star” image showed overcorrection, as predicted by prior computer simulation. A spherical secondary is bound to produced overcorrected images in a classical Cassegrain.
Naturally my next job is to change the spherical surface of the secondary into a hyperboloid. Don’t worry, I’ll post my method here – the secret of making the hyperboloid secondary mirror.
Best regards
Chan Yuk Lun
16 April 2012.
The purpose of making the tube assembly prior to the optics itself is to carry out star test. As mentioned before the primary mirror is already parabolic, the aim of the star test is to test the figure of the secondary.
Star test doesn’t need a real star. My target is a distant crystal chandelier. The reflection on the hanging “crystal” surfaces form perfect point sources.
The test result was short of surprising – the “star” image showed overcorrection, as predicted by prior computer simulation. A spherical secondary is bound to produced overcorrected images in a classical Cassegrain.
Naturally my next job is to change the spherical surface of the secondary into a hyperboloid. Don’t worry, I’ll post my method here – the secret of making the hyperboloid secondary mirror.
Best regards
Chan Yuk Lun
16 April 2012.
- 附加檔案
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- The aim of star test – to test the secondary mirror.
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- Ready for star test.
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- 夸克星
- 文章: 3847
- 註冊時間: 週四 09 10月, 2003 21:06
-
- 夸克星
- 文章: 3847
- 註冊時間: 週四 09 10月, 2003 21:06
Thanks a lot for your suggestion. However there are three resons prohibit me from choosing a big PVC tube :-wtyu21 寫:Dear MG,Why dont you using a plastic water tube for the main body for your new baby? I saw there are 10“ in diameter water tubes sell on the market once~
1. Expensive.
2. Heavy.
3. Circular parts are difficult to work with.
- lawrencemok
- 白矮星
- 文章: 741
- 註冊時間: 週一 25 7月, 2011 18:01
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- 夸克星
- 文章: 3847
- 註冊時間: 週四 09 10月, 2003 21:06
This small prototype Cassegrain will not be displayed in upcoming Open day ( 20,21 April ) but If you come I will of course show you personally.lawrencemok 寫:Chan Sir, will you show off this in QC open day?
A lot of other equipment will be shown, including a 14 inch Planetary Newtonian. I belief this telescope will be more attractive than the small Cassegrain.
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