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tommy_tse
週二 26 6月, 2007 01:39
版面: 自製天文望遠鏡 Amateur Telescope Making
主題: 天文望遠鏡製作 2007 (第十一課 - 實習課5) 24 June 2007
回覆: 26
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天文望遠鏡製作 2007 (第十一課 - 實習課5) 24 June 2007

Choi Sir was demonstrating his homemade setup with handheld controller to perform the Knife-edge Test (or Shadow Test).

Layanata added his digital camera to let us see image of the mirror (vertical lines).
tommy_tse
週二 26 6月, 2007 01:36
版面: 自製天文望遠鏡 Amateur Telescope Making
主題: 天文望遠鏡製作 2007 (第十一課 - 實習課5) 24 June 2007
回覆: 26
觀看: 15805

天文望遠鏡製作 2007 (第十一課 - 實習課5) 24 June 2007

Here is a pictorial record of the steps involved for making the Pitch Lap (cont'd). 10. Put rouge-water mixture on the Pitch Lap before cold press. 11. Cold Pressed for almost 1 hour and 15 minutes. 12. During the cold press process, Wah! was helping us to check the degree of matching between the mi...
tommy_tse
週二 26 6月, 2007 01:34
版面: 自製天文望遠鏡 Amateur Telescope Making
主題: 天文望遠鏡製作 2007 (第十一課 - 實習課5) 24 June 2007
回覆: 26
觀看: 15805

天文望遠鏡製作 2007 (第十一課 - 實習課5) 24 June 2007

Here is a pictorial record of the steps involved for making the Pitch Lap (cont'd).

6. Cut away the extra pitch around the mirror.
7. Use rules to prepare the lines for channel cutting.
8. Cut Channels in the Pitch Lap.
9. Cut in 30 degree angle around the rim of the Pitch Lap (No Photo).
tommy_tse
週二 26 6月, 2007 00:59
版面: 自製天文望遠鏡 Amateur Telescope Making
主題: 天文望遠鏡製作 2007 (第十一課 - 實習課5) 24 June 2007
回覆: 26
觀看: 15805

天文望遠鏡製作 2007 (第十一課 - 實習課5) 24 June 2007

Here is a pictorial record of the steps involved for making the Pitch Lap. 1. Wah! was melting the pitch over a stove. 2. Put the mirror and the tools in hot water. 3. Put paper strip around the tool. 4. Melted pitch was being poured on the convex upper face of the tool. 5. 豆豸苗 helped us to press th...
tommy_tse
週二 26 6月, 2007 00:49
版面: 自製天文望遠鏡 Amateur Telescope Making
主題: 天文望遠鏡製作 2007 (第十一課 - 實習課5) 24 June 2007
回覆: 26
觀看: 15805

天文望遠鏡製作 2007 (第十一課 - 實習課5) 24 June 2007

I spent one hour right before lunch to complete 6 runs of 5 minutes each W-stroke method using Sand # 1200.
I tested the mirror via reflection angle method during 600 and 1200 stages.
tommy_tse
週二 26 6月, 2007 00:36
版面: 自製天文望遠鏡 Amateur Telescope Making
主題: 天文望遠鏡製作 2007 (第十一課 - 實習課5) 24 June 2007
回覆: 26
觀看: 15805

天文望遠鏡製作 2007 (第十一課 - 實習課5) 24 June 2007

I started the lesson to complete the polishing using Sand #600. I did 6 runs of 5 minutes each with W-Stroke method. I spent a total of 2 hours from last lesson to this lesson to complete this.
tommy_tse
週一 25 6月, 2007 21:53
版面: 天文攝影 Astrophotography
主題: 各區天氣
回覆: 37
觀看: 12745

It is also cloudy here in Pokfulam; however, I saw some breaks in between clouds at around 8:45 pm and it is quite transparent. i think shooting Jupiter may be nice tonight.
tommy_tse
週日 17 6月, 2007 23:41
版面: 自製天文望遠鏡 Amateur Telescope Making
主題: 天文望遠鏡製作 2007 (第九課-實習課4) 17 June 2007
回覆: 23
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天文望遠鏡製作 2007 (第九課-實習課4) 17 June 2007

Here is a picture of how much #600 sands (mixed with liquid soap solution) were being used in a single polishing run.
tommy_tse
週日 17 6月, 2007 23:39
版面: 自製天文望遠鏡 Amateur Telescope Making
主題: 天文望遠鏡製作 2007 (第九課-實習課4) 17 June 2007
回覆: 23
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天文望遠鏡製作 2007 (第九課-實習課4) 17 June 2007

Wong Sir also showed us how to examine the grains of #600 above by back lighting via a 10x loupe. Wong Sir said he hated this as the bright light hurt his eyes and he will only demonstrate to us once.

Here is the picture of the #600 grains after 2 runs of 4 minutes and 30 seconds each.
tommy_tse
週日 17 6月, 2007 23:35
版面: 自製天文望遠鏡 Amateur Telescope Making
主題: 天文望遠鏡製作 2007 (第九課-實習課4) 17 June 2007
回覆: 23
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天文望遠鏡製作 2007 (第九課-實習課4) 17 June 2007

Look at this guy, he pretended to look like wong sir but I bet he did not know what he was doing! Wong Sir told this guy to go home and polish #600 and #1200 two hours each and forget about the reflection testing. Poor guy!
tommy_tse
週日 17 6月, 2007 23:33
版面: 自製天文望遠鏡 Amateur Telescope Making
主題: 天文望遠鏡製作 2007 (第九課-實習課4) 17 June 2007
回覆: 23
觀看: 15534

天文望遠鏡製作 2007 (第九課-實習課4) 17 June 2007

Wong Sir also showed us how to measure the degree of matching of the two glass pieces by reflection test under a florescent lamp to see if the refelction of the “red florescent lamp” brightness was even when moving the mirror left to right or vice versa. Don’t use pencil mark testing as it may scrat...
tommy_tse
週日 17 6月, 2007 23:26
版面: 自製天文望遠鏡 Amateur Telescope Making
主題: 天文望遠鏡製作 2007 (第九課-實習課4) 17 June 2007
回覆: 23
觀看: 15534

天文望遠鏡製作 2007 (第九課-實習課4) 17 June 2007

Before I started on sand #600, Wah! and 豆豸苗 helped us to measure our mirror’s focal length by measuring the radius of curvature using light test. My mirror’s radius of curvature was 1460 mm, which is 2 times its focal length. The standard f/6 with 120 mm mirror required 720 mm focal length. I was fo...
tommy_tse
週日 17 6月, 2007 23:20
版面: 自製天文望遠鏡 Amateur Telescope Making
主題: 天文望遠鏡製作 2007 (第九課-實習課4) 17 June 2007
回覆: 23
觀看: 15534

天文望遠鏡製作 2007 (第九課-實習課4) 17 June 2007

Wong Sir said there are a few common mistakes we made when polishing #320: (1) Too much sands so the tool and mirror were “lifted up” by the sands so polishing became uneven; (2) We did not got rid of the bubbles between the two glasses so not all surface area were polished; (3) We used too much or ...
tommy_tse
週日 17 6月, 2007 23:09
版面: 自製天文望遠鏡 Amateur Telescope Making
主題: 天文望遠鏡製作 2007 (第九課-實習課4) 17 June 2007
回覆: 23
觀看: 15534

天文望遠鏡製作 2007 (第九課-實習課4) 17 June 2007

I did another 5 runs of W-Stroke and the pencil mark testing still could not pass. This time with the rim markings gone but the center markings were left behind after dry strokes. A few students encountered the same problem around the same time like me. Choi Sir was wondering what had happened to us...

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