The making of 30 inch telescope - 2, specification

[Chanlunlun]

Dear ATMs,

For a 30 inch big mirror we must have a grinding machine. So we make one. It consists of 12 students.

This is what I call human fresh grinding machine. They are powered by Hamburger and Coca-Cola.

Following is the specification of the telescope :-

1. Aperture – 30 inch., thickness 1 inch.
2. Secondary mirror – 4」 minor axis enhanced aluminium coating. ( Actually this is the same secondary mirror of the 24」 and also the 20」 telescope. Three telescopes share the same secondary to reduce cost and resources. )
3. f/ratio : 3.3
4. Zenith eyepiece height – 89 inches ( may be a little bit more )
5. Transporting weight – 100 lbs.
6. Total estimated cost for construction – HKD 4000. We have spent HKD 1874 for the mirror blanks and reserve another HKD 1000 for 50 lbs. #40 grits. For remaining grits and polishing powder we use what left behind from the 24 inch project.
7. Labors required for transporting – 2
8. Reflective layer – single silver layer.
9. Mirror cell- 27 point true floatation system.
10. Focuser – intruding type, actual minor axis of secondary required : 3.3 inches. The bore of the focuser is 1.25 inch b cause we have one on hand, free.
11. Material for mechanical construction – plywood.
12. Slow motion control – yes. Powered by two dc 6 Volts gearheaded motors.
13. Tracking ability – yes. By regulating voltage applied onto the two dc motors.
14. Binoview capablity – yes, the intruding focuser provide sufficient back focal length for using binoview. Of course a 2X barlow must be coupled before the binoviewer while in use.
15. Weight of finished primary mirror : estimated 44 lbs.

Questions and suggestions are welcomed.

Best regards
Chan Yuk Lun
18-3-2005

[HK.Raymond.Tse]

Dear Chan Sir,

As you will have a grand 30 inch very soon, the largest ATM dob in HK, you may place (or sell) your old 24-inch dob with me, since I have a place for it : on top of my EQ platform.

Raymond Tse

[Chanlunlun]

Dear Chan Sir,

As you will have a grand 30 inch very soon, the largest ATM dob in HK, you may place (or sell) your old 24-inch dob with me, since I have a place for it : on top of my EQ platform.

Raymond Tse

Dear Raymond,

Thanks for your interest. However I regret to inform that we have no planning to sell or to let go the 24 inch telescope at the moment.

As according to our new planning the old 24 inch would be used for joint school function. It's marvolous to let students of other schools to see the heaven in greater details. The old 24 inch still remains very alive even with the emergence of the 30 inch telescope.

Best regards
Chan Yuk Lun

[chrislichi]

學校都有得磨鏡....正ar!!!