Rough grinding of 24 inch mirror was completed

[Chanlunlun]

Dear ATMs,

We are finally there.

Today we only carried out 1 hour of rough grinding and our goal was reached. Rough grinding is finished.

After a total of 19 hours of rough grinding work the final sagitta was 10.8 mm, which is being equivalent to a focal length of 82 inches, or in other word we have reached a f/3.4 curve. What a triumph day!!

But the story still continues – it is after a careful calculation ( no shown here ) do we realize that the actual focal length is indeed 77 inch, or actually we arrived at a f/3.19 curve - we have overdone the job!! What actually happened was that the group of students, during the last hour, pushed the glass so hard that twice the usual amount of glass has been removed and lead to an overshot.

This is not a big disaster . So our next step is to correct the surface back to spherical with the mirror on bottom and tool on top. A 1/3 center to center stroke will be applied in order to bring the mirror back to desire f/3.5 curve again. The remaining 4 lbs of #40 carbo is still useful.

The total cash burnt away at the moment is as follows :-

Mirror blank + tool blank $1200
Folding table for mirror grinding $138
25 lbs of #40 carbo $500

Total $1838

A lot of grit was consumed curing the rough grinding stage and still more to come. So we have to close monitor the money burning rate so as not to exceed our $4500 budget.

Hence you see that apart from physical laboring work, building big telescope also involves certain degree of management skill.

Best regards

Chan Yuk Lun
14-2-2004

[Wah!]

球面化未呀??

[Subaru]

球面化未呀??

第五斷第二句講咗未.

[Chanlunlun]

球面化未呀??

Dear Mr. Wah!,

Thanks for your concern. The surface correction stage will start 3 hours later today.

Best regards
Chan Yuk Lun
15-2-2004

[Wah!]

球面化未呀??

第五斷第二句講咗未.

吃吃吃....發雞盲添