Royce Conical Mirror - Anyone using?

[glend]

I am considering using a Royce Conical mirror for my next scope build - a 12.5" f5 imaging newt. This will be an ultra light scope, constructed of carbon fibre tubes, an optimised for imaging with focuser on the underside of the 'tube' structure at the front to optimise balance. A Royce Conical mirror would weigh less than half that of an equivalent full thickness mirror. Any users on IIS?

[Wavytone]

I would be interested to hear as well.

The question of Royce conical mirrors was discussed some time ago here on IIS but it did't come to any conclusion.

Some time ago I was considering buying one to build a lightweight dob but decided against it as the ones I was interested in had the central mounting bolt glued in place which raises a big question about what happens to recoat such a mirror, as glues will outgas in vacuum - effectively foiling any attempt to recoat it.

I don't really accept the idea that overcoated mirrors last indefinitely - especially in newtonians; I have had overcoated mirrors before for many years and they do eventually need recoating. The only exception is a multilayer dielectric coating, but that's serious $$$$ and I don't know if the figure is preserved with such a coating - they aren't thin.

I concluded better to buy a conventional Zambuto mirror made to order for two reasons:

a) I realised actually you DO need weight in the backend of the OTA to put the altitude axis down near the primary. A lightweight mirror (such as a Royce one) isn't such a clever idea.

b) no glue means it can be recoated.

Since then the weather deteriorated to the extent I can't really see any point spending $$$ again in this hobby until I can afford to retire and relocate to a better site; it's a year since my scope has been out of its box for any serious observing and that was so time-limited all I did was re-acquaint myself with the bright things. And there's the long waiting list for a Zambuto mirror...

[ZeroID]

I believe Rolf ( Skyviking) is using a 12.5" Royce Conical and you have seen what he can do with it.

http://www.rolfolsenastrophotography.com/Equipment/125-inch-Serrurier-Truss/

http://www.rolfolsenastrophotography.com/

[glend]

Thanks Brent, I knew I had seen one somewhere.

[Kunama]

Anthony Wesley used to have a Royce which he used successfully in 2009 to discover the Jupiter impact....... it might still be available for sale (14.5")

[Rac]

For imaging you cannot go past a conical mirror!

It's a shame more mirror makers are not using conical blanks.

Apart from my Royce mirror having a horrid figure it did work well but it should work even better now it's been refigured.