"Largest" Amateur Scopes?

[Moonshane]

We have a 20 inch f4.1 and based on this experience I personally would want to go for faster f ratio and keep the focal length down to 2 metres or less. If you just keep adding aperture and focal length your field of view keeps diminishing. This means you never do get to see M101 as a complete, bright spiral, nor M33 etc. You just get to see more and more fainter, smaller, galaxies in the same kind of detail as you saw familiar ones before the increase.

So that f3 scope seems to me to be a truly great idea.

As for ladders, no thanks! I welded up a wheeled steel platform for two, with handrail all around it. Yhis makes tracking easier (you rest your arms on the rail as you steer) and has a built in bin for EPs etc.

Olly

this is a great point Olly. the other thing to consider is that according to Kreige anyway, the weight of the rocker box for an f5 scope has to be 5x heavier than the secondary cage to balance due to the 'fulcrum' effect of longer poles. obviously the overall weight of an f3-4 would be much less as you'd just need to maybe add a little weight at the secondary end to balance (like a 31mm Nagler).

[John]

Great link John. If i win the Lotto tonight i'm getting myself a bleddy big dob.

I agree Russ - there is something about David L's scopes that is really appealing - I'll bet he does not turn out anything other than excellence

[FraserClarke]

The focal length is only 1500mm for a 20" Pretty amazing. No ladder required! Will open the door for much larger models without silly focal lengths and climbing 12ft ladders in the dark.

Or people could stop using a Newtonian design and move on to something far more suited to a large telescope.

I think the corrected Dall-Kirkham has a lot going for it as a big amateur scope of the future. Elliptical primary, spherical convex secondary, flat fold out to a focus at Nasmyth. A doublet (commerical lenses) to correct the spherical aberration, and give you a large field with far better image quality than a Newtonian. "easily" do a 1-meter with the eyepiece at seated level.

Olly's point about the FoV is a good one though -- directly linked to focal length that...

[haitch]

I helped a friend get his 24" David Lukehurst out of storage and set it up in the garden the other week.

It took 1 1/2 hrs to put it together and be up and running with 2 of us so whilst they are portable they aren't exactly grab and go.

I took my 14" round too and it took a couple of minutes to set up being solid tube (you do need a good sized estate for a solid tube f4.5 14").

I think scopes that big are really best off in the hands of a club where they can be appreciated by more people or taken by a group to a dark site where many hands make light work of setting up.

[Nexus 6]

I think scopes that big are really best off in the hands of a club where they can be appreciated by more people or taken by a group to a dark site where many hands make light work of setting up.

well ye, it would be something to have a look through a big scope at a local society. I'd certainly be willing to help set up one these beauties

[bish]

The biggest scope I have had the chance to look through is a 16". I'm itching to see some of the galaxies with a 20"+. There's a review site I stumbled across and the guy tested a really big scope (think it was 36", maybe bigger) and he said he could see the pillars of creation.

[Russells Teapot]

The Toronto Centre of the Royal Astronomical Society of Canada is the caretaker of a 1.88 meter (74") telescope. It was owned by the University of Toronto, but they sold the 200 acres of land it was on.

It used to be the 2nd largest telescope on the planet when it was built 76 years ago (only the 100" Hooker was larger).

Does this count?

[Glasspusher]

Hi Russells Teapot, that scope was made by Grubb Parsons in Newcastle, one of several with a mirror 74 inches in diameter.

John

[Russells Teapot]

It was. The mirror came from a test run that Corning did for the 200". The entire thing, dome and all, was built on Tyneside, taken apart and shipped to Canada where it was re-assembled. It has been painted many times over, and now all the screws look like rivets!

When it saw first light, it took over 2nd spot on the list of the worlds largest telescope from one that was "only" 72" in diameter, on the west coast of Canada.

So, for a time, Canada had the 2nd and 3rd largest telescopes in the world.

Anyway, they have a 100mm eyepiece that gives 330 times magnification.