Ultra Compact的大型Dobs

[David]

There is always some compromise. One can only make the more ideal dobs to suit one's need if he or she can make one. And some of us may not be good or interested in doing this. An ultralight is easy to carry, quick to setup and quite affordable, but has some compromise in terms of stability and not able to use big eyepieces. Obsession's ultra compact is not light but compact enough to fit the boot compartment of a small car if you buy 18 inch or smaller, but expensive. Can use big eyepieces like Ethos to enjoy spacewalk experience, very smooth and stable. Setup time is also very short.

[Chanlunlun]

我也正在考慮是否直衝16"的，真的很希望有機會可以見識Litescope的威力，之後再作決定！

Dear Steve,

Only very few 16 inch telescope/s ( actually may be only one ) is/are in active use locally. The reason is simple and obvious - weight and volume.

Think about this - how could one carry a telescope weights more than 50 kg ( e.g. a Meade Lightbridge ) to site without a car ? Under such concern even a Litescope weights too much at this aperture.

Even with a car you must design very carefully so that it is able to fit well into the small lugguage compartment. A 16 inch telescope is by no means a small toy.

A practical 16 incher must be custom made to suit local environment. That is

1. It must be equipped with ultra thin mirror to reduce weight and to facilitate fast thermal equilibrium.
2. It must be short enough to avoid bringing a ladder.
3. It must adaptable to giant heavy contemproray eyepiecs without losing its balance.
4. Last but not least it must be cheap.

At the moment I can't think of any commercially available telescopes fit all 4 above requirements simultaneously.

Best regards
Chan Yuk Lun

[BossKwan]

Meade,Celectron...等公司幾時會出Ultra Compact的大型杜蘇鏡?

Dear WFPC2,

You seem still not getting the main point - the most important part of the story does not concern about the telescope itself. It concerns how to transport the telescope to the site. So the main point is about an important accessory - a car or an aeroplane.

And your car must be big enough for your big scope to be comfortably sitted in. With a car you may travel to any site at ease, at any time, once good weather appears.

If you are using an aeroplane then your big Dobs must be so designed such that it fits into a standard suitcase for luguage checking in. One last word - if you are travelling with an aeroplane your gear should weight less than 30 kg otherwise you are getting troubles checking in. Nowadays airport workers are not so willing to touch heavy lugguages.

My experiences are first hand and wish you good luck.

Best regards
Chan Yuk Lun

Good points!

That's why I am in favorite with a 12" portable Dobs in light-weight truss design for maxiam portability which can be easily handled whatever you go by bus or taxi.

Of course, if WFPC2 who doesn't need to often move his Dobs around, says like having a fix site, bigger size Dobs should be desirable choice....

[Chanlunlun]

Good points!

That's why I am in favorite with a 12" portable Dobs in light-weight truss design for maxiam portability which can be easily handled whatever you go by bus or taxi.

Dear Boss Kwan,

That depends on how thick the mirror is. If you are using full thickness mirror ( 1 : 6 ) then a 12 inch mirror blank still weights too much for a single man travelling around without a car.

Chances are - you will be tired very soon after one of two trips. Sooner or later you will discover your "big" Dobs becomes a furniture sitting somewhere permenantly at home.

Best regards
Chan Yuk Lun

[lightning]

Meade,Celectron...等公司幾時會出Ultra Compact的大型杜蘇鏡?

Dear WFPC2,

You seem still not getting the main point - the most important part of the story does not concern about the telescope itself. It concerns how to transport the telescope to the site. So the main point is about an important accessory - a car or an aeroplane.

And your car must be big enough for your big scope to be comfortably sitted in. With a car you may travel to any site at ease, at any time, once good weather appears.

If you are using an aeroplane then your big Dobs must be so designed such that it fits into a standard suitcase for luguage checking in. One last word - if you are travelling with an aeroplane your gear should weight less than 30 kg otherwise you are getting troubles checking in. Nowadays airport workers are not so willing to touch heavy lugguages.

My experiences are first hand and wish you good luck.

Best regards
Chan Yuk Lun

Dear Mr.Chan

How comes any point related to car or aeroplane in this post?
It seems talking about the possibility of using an Ultra Light Big Dobs without travelling a long distance for WFPC2 himself.

David,Bosskwan and Mr.Yuen have given good points that is
still necessary to minimize the weight and aperture ratio of a
big dobs for WFPC2's future long use.

Why did you so care of people using a big telescope?

[BossKwan]

Good points!

That's why I am in favorite with a 12" portable Dobs in light-weight truss design for maxiam portability which can be easily handled whatever you go by bus or taxi.

Dear Boss Kwan,

That depends on how thick the mirror is. If you are using full thickness mirror ( 1 : 6 ) then a 12 inch mirror blank still weights too much for a single man travelling around without a car.

Chances are - you will be tired very soon after one of two trips. Sooner or later you will discover your "big" Dobs becomes a furniture sitting somewhere permenantly at home.

Best regards
Chan Yuk Lun

Dear Chanlunlun,

You are right, I do concern about the thickness of the mirror. As far as I know, some of China factories can supply mirrors with a ratio of 1:8 or even close to 1:10 which should be good enough for constructing a real portable Dobsonian.

Another key problem is how to minimize the weight of the structure of the main mirror's house (the base cell). Wooden materials or aluminium, which are good for the design? All these need a deliberate plan...... and I hope I am able to work out a fancy design...

Peter Kwan

[Chanlunlun]

Dear Mr.Chan

Why did you so care of people using a big telescope?

Dear Mr/Miss Lightning,

Yes. Exactly. I care very much about people using big telescopes because so many of them just disappear after one or two appearances.

Isn't that beautiful when one day we could see two, three or even more big scopes around at site ? Isn't that marvellous when many more people can enjoy the veiw inside many big scopes all at once ?

In foriegn counrtries and even inside China people start to travel to star site by driving cars. the same should appear in here, if big scopes are to survive.

If we demand even better results at more remote places we should travel by aeroplane. I used to travel to remote places for star gazing with my 20 inch telescope by planes. My 20 incher has been travelling around the world for more than 10,000 miles. Portability is then a must.

That's why I mention them. That's what big Dobs are built for. Without knowing this - your big Dob eventually becomes a piece of furniture.

Welcome to reality.

Best regards
Chan Yuk Lun

[TONGKW]

在香港，大多天文同好都没有自己的漆黑觀测地方，天文望遠鏡需要可以容易地被携带到觀測地點，這是極之重要，蓋如果套鏡太大太重 ，就不容易被携带會令使用次數不多至越用越小到不用，最終會被放在床下底積塵。

[iceeyes]

请问镜神，如果DOB组件有木头构成，进出关会不会有特别的注意事项？

[Chanlunlun]

请问镜神，如果DOB组件有木头构成，进出关会不会有特别的注意事项？

Dear Mr/Miss Iceeyes,

Wooden parts can be freely carried into China without problems.

However Australia has very strict policies against carrying wood into their country. If you have a Dobsonian made of wood make sure you have converted all parts into metal before departure.

Best regards
Chan Yuk Lun

[TONGKW]

這間外國廠有售十分便携”Dob” ，有 6“ 至 14” 口徑，設計獨特， 較細口徑的應該可以由壹個人携帶外出 。
http://www.sumerianoptics.com/alkaid.php

[豆豸苗]

這間外國廠有售十分便携”Dob” ，有 6“ 至 14” 口徑，設計獨特， 較細口徑的應該可以由壹個人携帶外出 。
http://www.sumerianoptics.com/alkaid.php

多謝唐生好介紹!
靚靚0既木工 + 好欣賞佢個箱拆開轉成水平轉盤!!!!!

[WFPC2]

這間外國廠有售十分便携”Dob” ，有 6“ 至 14” 口徑，設計獨特， 較細口徑的應該可以由壹個人携帶外出 。
http://www.sumerianoptics.com/alkaid.php

Thanks for sharing the good link Mr.Tong.

果種木材會否忌與水份接觸?

[iceeyes]

感谢镜神解答。
To WFPC2，木头上最好还是上清漆比较好，防霉防蛀。也不用担心露水。

[WFPC2]

感谢镜神解答。
To WFPC2，木头上最好还是上清漆比较好，防霉防蛀。也不用担心露水。

但油漆會有洞,雨水很容易滲入。