When scopes start to get big.....

[Peter Drew]

Ironically, size is the cure for aperture fever, if the scope gets too big to be conveniently useable it can get sidelined like my 30" F4.1 which has not seen use for about 6 years since replacing it with a much more useable 16" LX200.

[crashtestdummy]

I considered building one myself and even though im a mechanical engineer by trade im still not 100% confident to undertake it.how good is the book?

[barkis]

I considered building one myself and even though im a mechanical engineer by trade im still not 100% confident to undertake it.how good is the book?

Very doable, if you are meaning the making of the mirror.

A 12" is the best bet for a first go, but even that requires a lot of care .

If you could get one with a pre generated curve to around f5, it would save you a lot of work grinding it out, and fine grinding, polishing the figuring would be your job. Followed by the aluminising of the finished article.

The big asset you'll need, is patience. Not sure how available mirrors with generated curves are.

A 16" would be a monumental task, but, amateur mirror makers do them, and larger.

Two books are available in print still I believe. Jean Texereaus Telescope Making, which is by far the best, and NE Howards Handbook for Telescope Making is also still in print I think.

I made mirrors years ago, but I sold up all my remaining Mirror Blanks, Grinding agents and Polishing powders, together with a grinding machine , plus the Texereau Book.

I still have the NE Howard book, which is a bit dog eared, but still OK.

There have been a number of members who have undertaken the making of mirrors, and One member. Glasspusher, did a tutorial type Thread to aid those who were involved .

It's a great activity, if you have the fortitude and stickability to see it through.

Your engineering skills should stand you in good stead, especially where telescope the hardware requirements are concerned.

Many folks buy the Optics ready made, and build the Tube and Mount, although the mount is easier if it to be in a permanent location, and especially if it an Equatorial cofiguration.

Believe me, it's a great feeling when you can work a large lump of glass into a very precise optical device

Good luck if you take it on.

Ron.

Glasspusher.

http://stargazerslounge.com/user/3192-glasspusher/

[crashtestdummy]

The trick with Orion Optics scopes is to buy them used

yeah i think i will just avoid any of their products in future just to be on the safe side

[crashtestdummy]

i would buy the mirrors and just make the base and truss assembly,i dont fancy dealing with mirrors tbh

[Beulah]

 This WILL NOT FIT through your standard 2'6" doorways. I will make the necessary alterations to the design so it does.

Wassat, to your doorways? That's one dedicated Dob fan!

[MarsG76]

Good comparison for anyone contemplating a size upgrade.

Initially I wanted to go up to a 16" dob from my, or complement my 8SE.

I settled on a Skywatcher 14" GOTO Dob due to the fact that I just (millimeters to spare) fits through the back door when wheeling the assembled unit. (I added 4 wheels to the base of the dob with swivel a wheel stops).

Reason 2 was that when observing at or near zenith the 14" was the perfect size for me to be comfortably looking through the eyepiece when standing up... perfect height...

Comparing the views between a 14" and a 16" most likely won't be that different, judging that by the fact that even now the 14" only very noticibly out performs the 8SE on the clearest and darkest nights. On average nights the views are similar.

That said, I setup my 8SE/CGEM kit as only Astrophotography and the Dob as only observing... I am loving the views the dob delivers.

 

[Wobbly Bob]

On 16/01/2013 at 23:11, Naemeth said:

How will it weigh more?

The  mirror, a solid lump of heavy glass plus the support structure.