This is the sort of thing i'm after, who makes these in Australia?

[overlord]

http://cgi.ebay.com/12-5-F8-TRUSS-TUBE-DOBSONIAN-TELESCOPE-SWAYZE-MIRROR-/120728683778?pt=US_Telescopes&hash=item1c1bfd8502#ht_500wt_1076 :thumbsup:

[erick]

Various people have made their own, or a few. I only know of one who has made quite a number now, for customers:-

www.sdmtelescopes.com.au (http://www.sdmtelescopes.com.au)

Various of these also come up for sale second hand, from time to time if you are patient.

You can buy truss dobs from overseas (USA mostly), but shipping will be significant. There are kit makers overseas which might reduce shipping costs, but you would need to fit them out yourself with mirrors, focusser etc.

[astroron]

Eric I think he is more interested in the Long focal length as he wants it as planetary scope.
I think he would have to find someone who makes that kind of mirrors as most mirrors are made for shorter focal length scopes these days .
Cheers

[overlord]

Awesome yeah! I was thinking about the longer focal length tho?

The good thing about such an arrangement is the mirror can even be spherical if it's more than f/10. I want a 15" f/10, hell yeah! The bottom half will be buried in a wine cellar with the top half at ground level. :eyepop: LOL!!!

Also he don't list prices, :eyepop::eyepop:

See later this year i'm gonna buy myself something interesting for planets, so it's gonna be a Saxon Mac, or an Obsession or....... ? I've talked about it heaps on here! But these long focus gems are amazing. I would love one of these!!!!!!!!!!!!!!!!!!!!!!!!!!

I have an f/5 with an early 2000s focuser and it's annoying! Saturn looks like a normal face and then when i release hand from focuser it defocus to this :eyepop: and i don't want a crayford either, i need a whole NEW SCOPE! LOL!!!

[renormalised]

Ron is right....unless you ground your own mirror to the specs you wanted, you would have to get one especially made. Most of the mirror makers do short focal length mirrors, but if you asked, I would imagine one of them would be more than happy to make you a long focal length mirror.

Mind you, with anything over 8-10" in mirror aperture you'd need a damn tall ladder to look through the eyepiece!!!!.

[erick]

I'm sure that Peter and a mirror maker will, theoretically, make anything a customer wants - as long as they are convinced it will work. But, true, their order books might be filled with large aperture, short focal length scopes that they have geared up to make in the last few years.

[overlord]

I will.

Later this year i'll pay someone to make a good mirror for me. I will make the best planetary telescope in the southern hemisphere. 20" f/15. :rofl: just kidding, 15" f/9 or something will do. :P Oh I'm silly today. I think Patrick Moore has something like that, so I will need an f/12 to keep up appearances:

OOPS, no he has a 15" f/6.

http://www.astro-sharp.com/pm_restoration_page3.asp

It's ok... I have a big backyard. I am sooooooo gonna do this! The long-focus revolution beginneth! :thumbsup:

[overlord]

This is so exciting! I am gonna built using spherical f/12, of 16" diameter. Telescope will be 5 meters long! f/12-f/15 is necessary to achieve sharp views in a Mak.

Base to be buried deep in the ground! But it would be easier to just get a larger obsession oh well. :*(

[tlgerdes]

Cant you be like everyone else and get a good 16" F5 and put a 2x powermate on it. At least then is it doesnt need a riggers course to operate.

[overlord]

There are no 16" f/5's

[overlord]

I will never use a ladder for any telescope.

That is an impractical solution suited to dark skies.

Rather, the bottom of the scope will be located in a subterraneous vacuity.

The top shall be surrounded by a seated observing platform. I will be able to sit down even with the largest scope. This is necessary for sketching planets.

[bojan]

Hmm..
this "subterraneous vacuity" of yours for "the largest scope" will cost you more than scope itself ;)

[Satchmo]

They are hiding from you.

[toc]

This sounds like a blurb for a patent application. :D Do you have something already designed?

[overlord]

Yeah I know, but I want to do something crazy.

[overlord]

They don't really make em. They make ~f/4.5 and then don't tell u that u need paracorr at that ratio. They push the limits to get the aperature/weight ratio high for sale. My digital camera gives fish-eye at that ratio. I have learned that it must be set to f/8 to get crisper images. sO I am gonna do something radical and make a 4" f/50 scope. I will only be able to point at the horizon and stuff but it will be the first in the world! 6 meter focul length, lol. Who wants to make a primary f/50 for me? actually i need to think about that, will release a tender later this year.

[bojan]

You do it yourself:
http://telescopemaking.org/grinding.html
http://www.youtube.com/watch?v=AbRa_NpI9nE
http://www.youtube.com/watch?v=ng_dFoOHHF8
http://www.youtube.com/watch?v=BJ3SeL4G8y4

[dannat]

Just buy the 16" & colour in the outer 2-3 " in blk texta to improvebthe f/ratio..& avoid the paracorr, then cut the 2ndary to a smaller size & get a curved 3 vane spider :thumbsup:

[toc]

There is a telescope design that combines long focal lengths, large aperture and short manageable tube lengths. Its called an SCT! :D In all seriousness, that is why a lot of us own such scopes. We know they are compromises.