the first star test of the 24 in telescope

自製天文望遠鏡 牛頓望遠鏡 杜蘇式 卡式 設計和磨鏡方法<br>
佛科試鏡法 佛科刀片儀 光柵試鏡法 光柵片
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註冊時間: 週四 09 10月, 2003 21:06

the first star test of the 24 in telescope

文章 Chanlunlun » 週二 20 4月, 2004 11:34

Dear ATMs,

Thanks for the continuous fine weather the first star test of the 24 inch telescope was carried out last night, using a UWV 6.7 mm eyepiece, giving a 313X magnification. The result obtained will be used for retouching the mirror at once.

The test reviewed the fact that the mirror is under corrected a little bit although it shows a null figure in the Offner tester. This is by no means surprising since there must be error, one form or the other, exists inside our Offner tester. Computer simulation for light ray tracing will be commenced at once to locate a more optimized setting for the Offner tester.

Since the spherical aberration present is very mild the retouching process should be carried out in utmost care. A figuring process more than 10 minutes will probably overdo the job. Hence the mirror will be figured directly under star light, then reconfirmed by the re-calibrated Offner tester. This is being more safe-proof than the job carried out in the reverse order.

This is the beginning of the end. The birth of this newly fabricated large telescope will not be long away.

Best regards
Chan Yuk Lun
The sketch of the result of the star test last night. Left is the what was observed inside focus, middle is at focus and right is outside focus. It shows that the mirror is being a little bit undercorrected.
star_test1.jpg (5.35 KiB) 已瀏覽 4731 次
Perfect mirror should show such pattern under star test.
star_test2.jpg (5.18 KiB) 已瀏覽 4731 次


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