Sourcing a Conical Primary?

[MrB]

I was getting ready to order a conical primary mirror from R.F. Royce Optical, but Robert just informed me there is at least a 6 month waiting list!

Anyone know if there are any other reputable glass pushers making conical primaries?
A cellular primary would be even better, but my finances don't quite stretch that far :(

[SkyViking]

I have just ordered a 12.5" from Royce this week. I was told it should be here in January. Still a few months away but not 6?

[MrB]

Hi Rolf,
In Robert's follow-up email he says "Delivery is likely after February. I'm swamped." so 5+ months :sadeyes:

[anj026]

You might try Ostahowski Simon, otherwise just place your order with Royce asap.

Take consolation in the fact that you are not after a D & G lens or and A-P refractor! :)

[MrB]

Cheers Andy.
I had briefly entertained the idea of converting your old Dob into a small Astrograph... but there's no way I could butcher your hard work!

I think you are right, I'll just have to place the order for a 12.5".
I was going to order a 10" but with the extra wait, I can squirrel away a bit extra cash :)
Will have to get a cheap GSO primary in the meantime.

The number of times I have thought about an AP over the years, I could have had one by now! :rolleyes:

[SkyViking]

Maybe my order pushed it to Feb, oops sorry ;) I wonder how many mirrors he makes in a month?
I will be building a bigger truss tube in the meantime anyway so the wait doesn't bother me too much.

[GrahamL]

I would of thought 6 months not to unreasonable ?

[Satchmo]

I've made a number of conical mirrors ( see latest results from David Fitz-Henry's 12.5" "Bunyip") however not taking new orders at the moment.

The conical blanks have been manufactured by Newport Glass since the late 1980's. It a wonder that more opticians don't offer them.

[MrB]

Whew! I don't feel so guilty now! :lol:
I had fully intended to request a quote from you, but then I was offered a used one of your 10" f3.8 conicals.
I will more than likely send you an RFQ when I decide to go for more aperture ;)
David's build thread is one of the reasons I decided to go with a conical for my Newt-Astrograph.



It is strange isn't it? There are so many advantages, I am yet to think of even one disadvantage :shrug:

[Satchmo]

There is a fair amount of thickness and mass in the centre. Renowed planetary photographer Anthony Wesley found them not ideal for imaging in Canberra where the mirror has to track some large temperature shifts. I am a fan of them but they are definitely more fiddly on the production side.

[MrB]

That is true, however I thought the centre thickness was no thicker than a full thickness mirror(6:1) So overall it has reduced mass?
I think for my use, the 80-100mm secondary obstruction should pretty much cover the majority of the centre anyway?
For me, dealing with a flotation cell and supporting a thin-mirror with edge support in an imaging scope really doesn't appeal.
The ease of mounting and the supposed benefits with conicals holding their collimation had me sold.
If it takes a little longer to reach thermal equilibrium than a thin mirror, so be it.

[Satchmo]

Well , yes , reduced mass compared to a style of mirror that been out of vogue for a long time. I found the total mass of 14.5" to be about the same as a 1.6" thick blank. It is pretty neat doing a center mount , and you save the mass and complexity of a float cell. IMHO the cut -off point for those designs is 14.5" above which the design of the Newport blanks is probably starting to get a bit flimsy for self- supporting design ( ie too thin out near the edge).

[MrB]

Yeah sorry, in my head I was comparing with mirrors of relative ease to mount, so ignoring thin mirrors. I didn't convey that very well (at all!)

[MrB]

I had sourced a 10" f3.8, but sadly that sale fell through.

With Mr. Royce backlogged and Mark not taking orders, it's getting hard to find a mirror. This is crazy.

If anyone has a 10" or larger conical, around f3.8 or f4-ish, in good condition, please let me know.
I have a lot of $ invested in carbon and I don't want to waste it.

Edit: Thanks to everyone that has previously contacted me via PM, much appreciated.

[Satchmo]

Hi Simon- I wouldn't get too obsessed about conicals. A 10" in 1.33 to 1.4" thick will perform just as well thermally and just needs to be bonded to at least a 9 point cell- if you are building a scope the cell is is easy to make. A conical still needs a tilt mechanism so the only difference between the two styles of mounting are 3 aluminum triangles.

[ZeroID]

\
Upgrade time hey ? You going to document this build as you did last time ?

Don't think I'll be copying you on this one. Too big for anything I've got room for. :shrug:
Good luck with the build. :thumbsup:

[asimov]

Just a bit of useless info > The commercial SW 14" newt primaries are all conical.

[Satchmo]

yes, interesting bit of history there. As Skywatcher bought Celestron , the mirror blanks in the 14" are the same ribbed conical ones as used in the Celestron 14"'s since the 1970's . ( At least as far as I've seen in the Orion Dobs which are made by Skywatcher for Orion ) .

[MrB]

Cheers Mark,
I had thought about this, but as it will be used as a portable astrograph I really liked the simplicity of mounting a conical and the fact there is less chance of the primary moving and losing collimation(perhaps this is flawed logic?), whereas the traditional cells just seem to have too much possibility for movement, particularly while being transported in the back of my car to a dark sky site.

I'm afraid my enthusiasm for this hobby is hemorrhaging fast.
Every path I try to take I seem to get blocked. Used scopes either get sold out from under me to other buyers(this has happened a number of times here, presumably because the new buyer can pick it up), or the seller can't be fanged to box it up and freight it(also a number of times). It really isn't that hard people!

I might take up knitting or something.
But then I'll probably go to Spotlight to be told there is a 6 month wait for wool.
That wasn't a personal dig at you Mark, your circumstances are different, just at the industry in general.

Yeah I'm just having a whinge, I'll get over it. It is just frustrating.
My last ditch effort will be trying to polish a turd; a GSO imaging newt.
I only need the primary, everything else will be trashed or parted out, but it's the only place I can find a 10" f4 before my darksky holiday in a couple of months.

[anj026]

I know it's not what you are after Simon but Royce has a 10" f6 conical available for sale now.

http://www.rfroyce.com/

Andy

[MrB]

Yeah really want something around f4, but cheers for the heads-up Andy :thumbsup: