16 inch ultra light weight telescope - version 1.0

[Chanlunlun]

Dear ATMers,

I will go a Maldive trip next month and it is a big waste not to explore the extremely clean sky over there. My luggage capacity is only 15 kg (cheap air ticket…lol ) which means that the 20 inch telescope cannot go along. The next on my list is a 16 incher, that is the PTC telescope that many of you may get familiar with.

My task is to reduce the total weight of the telescope below 15 kg, with an aperture of 16 inches. The problem is that the mirror itself already weighs 8 kg. I have only a margin of less than 7 kg to work with.

So I adopted a single pole design. To further reduce the total weight I change the secondary from 4 inch to 2.6 inch, vastly reducing the weight. The focuser is also change from a metallic rand-and-pinion to a custom PVC one which has a weight of only about 30 grams.

At the same time I have to lower the center of mass of telescope as much as possible to increase stability. After a few days struggle I finally come to a result of what you see in the attached pictures.

As usual I choose 3/4 inch plywood to work with. it is cheap, strong, light weight and easy to handle. Carbon fiber will get better ( and fancier ) results, but it is very expensive and not readily available.

Star test of the finished scope was carried out last night. Although the single pole is strengthened by three taut steel cables, it still cannot display as a rigid structure as traditional struss structure. However the alignment still holds good enough if altitude angle is not less than 30 degree, which I feel should be sufficient for ordinary visual star observation. The vibration is still there but not serious. The telescope is being fully functional.

The total weight of the telescope is 14.7 kg, not counting the eyepiece and telrad. I am being very glad with the result.

The plan B of the telescope will be carried out shortly, with carbon fiber struss design. I am waiting the arrival of carbon fiber tubes. But at least I have this scope on hand now, in case the carbon fiber cannot be ready in time.

Best regards
Chan Yuk Lun
18 June 2015

[Steve]

It is a pity that did not see you bring this new ultra light weight telescope for us to have an appreciation at PTC in the past starry nights started on Monday.

[Chanlunlun]

It is a pity that did not see you bring this new ultra light weight telescope for us to have an appreciation at PTC in the past starry nights started on Monday.

Hi Steve !

I did not come because I was making the telescope on Monday and Tuesday. On Wednesday night I star test the telescope at my home.

[鄧登凳]

You should paint everything black, shouldn't you?

[bingsze]

How about tonite?!

[Chanlunlun]

You should paint everything black, shouldn't you?

Hi Mr. Tan, long time no see.

Only the internal wall and the edge of the mirror box is required to be painted in black.

It will be done shortly.

[Chanlunlun]

How about tonite?!

Cloudy night !

[Eddy So]

[大黃傻貓GARFIELD]

Quick-witted makeshift but usable - as usual from Chan sir.

Be sure to share with us your trip at Maldives!

[Carl Chan]

一流設計！非常懷念以前大家在馬爾代夫觀星的經歷！

[Chanlunlun]

一流設計！非常懷念以前大家在馬爾代夫觀星的經歷！

Hi Carl,

Yes you tell the truth - 20 inch telescope at Maldive, truly amazing experience.

But now I can't carry the 20 incher, can only do this 16 - the next big on my list.