Telescope design

[Orion]

Hi All,
I have been tinkering with this idea for a while now for a different design in a telescope one that will bring the focal point back down to earth "sort of speak" Would be interested in you're comments.

[slice of heaven]

There is already a newt with that design so you can use long focal lengths
Ive seen large dobs and the ep is near the alt bearing to remove the need for step ladders.

[astro_south (Andrew)]

I have been thinking of a similar idea - having the eyepiece at the centre of an altiude bearing so that the height doesn't change. I was thinking that the secondary and tertiary would be bigger than you have depicted though. Have you used software to come up with the design parameters?

[Orion]

No Andrew it's just a quick drawing to get my point across. With such big telescopes it's a must to have the eyepiece towards the middle of the scope.

[ballaratdragons (Ken)]

Ed,

would you use a spider or a correcting plate to hold the 2ndry? and how would you mount and adjust the diagonal mirror?

If you ever get a chance to come to our Ballarat observatory you can see the 'Federation Telescope'. It is designed for the Handicapped. They sit in one spot and the EP never moves whilst the scope moves all over the sky.

http://observatory.ballarat.net/faci...tml#federation

[Orion]

Ken I would use a spider for the second and third mirror, corrector plates for that size scope would be huge and heavy. I am thinking to adjust the second and third mirror like we normally do with our diagonals

[ballaratdragons (Ken)]

I imagine it would be a truss frame as well. That would then give access to the diagonal for collimation.

[Orion]

Now you are catching on Ken!

[ballaratdragons (Ken)]

Sounds like an excellent project Ed.

Are you able to purchase the correct 2ndry or would you grind & figure it yourself?

[Vermin (Tom)]

Interesting idea Ed. Any reason why you couldn't use a flat for the secondary?

Assuming it did not overly complicate collimation, I'd be interested in this sort of set up for my 16" f5. It would negate the need for little ol' shorty me having to use a step ladder.

[stringscope (Ian)]

Fascinating project Ed.

Do you have the primary mirror on the way already?

I asume the primary would be parabolic and the tertiary would be a flat, what about the secondary??

Cheers,

[astro_south (Andrew)]

Ed

just wondering why a flat secondary wouldn't work.... or would it?

[Orion]

Ok this is why I would like to use a cassegrain secondary, I think that a flat secondary will obstruct more incoming light it would have to be bigger than the cassegrain secondary. Having a long focal ratio to cut back on the size of the flat secondary would put to much demand on the telescope mount, having a longer and more heavier upper section. The convex of the secondary will allow for a longer focal point to get the eyepiece further down the telescope.
I haven't even started with the primary it is just an idea at the moment witch might come a reality in a few years to come.

[iceman (Mike)]

Nice project Ed.. but what does the wife say about this?

30" would be one hell of a scope, can't wait to test it out at Kulnura.. will it be done by June new moon?

[Astroman (Andrew Wall)]

Jims Mobile produce a similar scope to your Design, VERY expensive!

http://www.jimsmobile.com/ntt30_data.htm

Love the design, but the obstruction up top is a little too large for me. I am guessing it would only have a similar performance to a 12" or 14" scope.

But with limited reviews it's hard to say.

[h0ughy (David)]

Your been hearing voices again Ed. George has turned you, and you have gone to the apature fever.

Has george talked you into the 30" he made, and with a little bit of modification you came up with that design?

[mch62 (Mark)]

It will need to be a Cassegrain secondary as a Folded Newtonian will have a large obstruction in the flat but they are out there.

Interesting but expensive idea though.

Me thinks a step ladder is cheaper

I would say you could pick up a second hand cherry picker cheaper and keep it a straight Newtonian focus.

Here is a 31"f7 Newtonian

[Stephan]

Hi Ed,

Would be an interesting project especially with a 30“ (in words thirty) mirror. You idea is not new in fact it is more than a hundred years old. This design is called Nasmyth-Telescope after J. Nasmyth 1808-1890.

If you build the mount fort hat telescope your self as well, why don’t you build a Coudé Telecope? You just have one more mirror inside the mount and your eyepiece is on the mount in a stationary position independent from the position of the telescope.

Stephan

[Orion]

Andrew, I seen that telescope from JMI before the secondary is flat and the obstruction must be large considering the size of the telescope. The Cassegrain secondary will be smaller than the flat making the focal point longer to allow the eyepiece to be further down the telescope.

Houghy, no voices heard just dreams of big plates of glass. George and I have been doing a bit of talking but I'm the one that brought it up. I wasn't aware that he had a 30" I know he's got the 32"

mhodson, it would certainly have a Cassegrian secondary I've seen the folded Newtonians out there with flat secondary but they don't bring the focal point down far enough and the secondary is to large. By getting home made mirrors it will cut down on cost (been up cherry pickers plenty of times but I think I'll give it a miss this time)

Hello Stephan thanks for the input. I was sure that some one had come up with the idea but I didn't know who. Just wondering Stephan I noticed that you come from Newcastle have you been to the Newcastle Astronomical Society?
http://www.nas.org.au/

[Stephan]

Hi Ed.

I have never been to the Newcastle Astronomical Society because the meetings are usually Friday nights (last Friday in the month or so) and for the peace at home ...

Stephan