two 12.5" f6.7 CF truss RCs completed

[TrevorW]

Howmcuh was the mirrors and whre could you buy nowadays

[Doomsayer]

I think one pyrex mirror set cost around AuD 2700 coated/landed about 18 months ago to my recollection. Star Instruments will sell you professional grade 12" f9 optics from low expansion material for at least triple that (not the even higher end ion milled variety from Aries).
Field flattener lenses for my RC $550US. There are medium level cost European RC optic manufacturers - somewhere in Italy (possibly A&M) and in one of the new Czech states I think. There have been posts here about Chinese suppliers as well - not sure about their quality. Another Italian ATMer has a website which gives info on his 12" RC at
http://www.tamanti.it/astronomy%20RC300.htm
- he uses ARIETE optics

guy

[AlexN]

Guy, At the prices you paid for the optics, and rough estimates on my behalf for the CNC work and outsourced labour, the pair of these would come in at around 2/3rds of the cost of 1 12.5" RCOS or there abouts?

Bargain in my eyes...

I took a look at the Italian one as well.. End product, I think yours look much more professional (read : make people stop and say "WOAH!! Thats a SERIOUS scope..") however I think his setup looks a lot more simple to make...

Not to mention, I dare say its much easier to ensure everything is aligned right in a solid tube than a truss setup..

If I had my choice of one to own, it would be one of yours, If I had to choose one to build myself.. It would be the italian one..

I'd be very keen to try to build myself a 10" RC scope, however I think I'd wait to see the prices of the GSO 10" RC unit when its released first... As that might be a more cost effective way to go, and if anything isn't right at first light, you can always send a bought one back..

[astroboy]

There looking great Guy , can't wait for delivery in a couple of weeks , just make sure I get the best one
Tony its probably not such a bargain when the amount of time that guy as put into the scopes and all the agonizing he did over the design , any one know a good trauma counciller ?

Thanks
Zane

[Doomsayer]

Thought I'd round off this post by showing some installation photos at Magellan Observatory. I took the other near identical 12" f6.7 Ritchey Chretien CF truss OTA down there last thing in January. It now rides on a Losmandy GM200 mount in the Sirius dome.

For first light we balanced up the scope with a Canon 5D DSLR (thanks to Col) and took a few test runs of images at f6.7. This OTA also has an integrated field flattener. There was no vignetting visible but there appeared to be a slightly tilted imaging plane. I also put a 31mm nagler in the back for a quick visual check anyway - we were all blown away by the beautiful contrasty and sharp views - we did not expect this with such an imaging-biased telescope.

Next day we rechecked optical alignment with a 2" laser and a 2" autocollimator. The OTA optical axis & secondary mirror were slightly out - easily fixed. At nightfall we reinstalled the Canon 5D - the stars were now even right to the corners. We also installed the A-P 0.75x focal reducer with the 5D. Again, no vignetting, excellent contrast, and even stars across the field of the 5D. The FR did eat up more backfocus however.

I admit to being relieved, as the much smaller chip on my own 12"RC with an ST8XME is hardly a test of these RC's imaging performance.

Still a bit more opto-mechanical refinement to come perhaps, plus plenty more road testing. At least it has been proved worth the effort so far.

A couple more pics of the other new scope at Magellan Observatory are attached.

guy

[spearo (Frank)]

Seriously impressive stuff,
could quit your day job and go into production if the testing turns out good!
frank

[Doomsayer]

thanks.
A production run seems feasible at face value. Especially with the economies of scale offered by a batch run of Al-plate parts put through a good CNC mill. I'd certainly want to be confident of the imaging performance of these OTAs first. The design is quite easily scaleable to larger mirror sizes.

An affordable source of optics is also an obstacle at the moment. Also not sure it's a good time for me to start a new business in the present economic climate.

I would be considering building my own motorised secondary focuser if I did this again. The Van Slyke secondary focuser these OTAs use adds a lot of mass and additional length to the OTA. The Van Slyke does do its job very well however. These two OTAs do require a mount with a high load capacity.

guy

[Jriy (George)]

Hello.I on a forum first.I write with a help it online translator.I have a complete set of mirrors for 300mm RC.Ya search the drafts of frames of main and auxiliary mirror.Can you help with drafts?Or help make the frame?

[Doomsayer]

Hello George
Check your PMs. You need to supply me with full mirror specification, sizes etc of the mirror set before I can comment.

guy

[Paddy (Patrick)]

What an impressive achievement, Guy. Amazing, superb.

[Doomsayer]

Thanks Paddy.
The RCs turned out well mechanically, and also seem to be cutting it optically and operationally (which is a relief!). It has taken me most of my limited sky time last year to get the whole optical, hardware and software system figured out and de-bugged. Just a bit more system tweaking to go before getting regular imaging runs under way. Then I have to concentrate on image processing....
guy

[Fivey (Jeremy)]

I really like this, it's inspiring actually. An ATM project with no half-measures, no cardboard tube, no wooden cradle, but a real honest-to-goodness proper telescope.

Just a question on the baffle - are you losing some aperture there in the middle? (Or is it all completely under the secondary mirror obstruction?)