Why no CHiefs intrest???
Posted 01 January 2013 - 09:01 PM
Dave O did a great paper explaining a 10 inch I hope he will post it .
That little document was created for Jack S, and is specific to his CHief; he has added some more information from an actual construction point-of-view (again specific to his design). As far as I am concerned, it is his document now, and he is free to do with it as he likes.
Posted 01 January 2013 - 10:29 PM
As for me, I've got my long focus Newt now and it's just massive. The CHief is still attractive for me and now that I have my newt, I can go back to stabilizing the problems I had with the mount and CHief's upper OTA.
Kevin's concept of the waterjet upper OTA is I think really good for those of us who are intimidated by field collimation. Ed assures us that the skill is learnable and not necessary every single time, but I am cautious.
I'll post the document in a bit.
Posted 01 January 2013 - 10:43 PM
If you want a copy, please email me at firstname.lastname@example.org. :-)
This document has contributions by Dave and Mike and Kevin. The document is part narrative and part compilation of emails.
I don't have the time to clean it up anymore right now, but I am saving it for my assured return to the CHief.
Enjoy. If you have questions, I will do my best to answer.
If you have feedback for this doc, please by all means let me know.
Posted 01 January 2013 - 10:46 PM
Could you email it to my Yahoo account?
Posted 01 January 2013 - 10:52 PM
Posted 02 January 2013 - 12:26 AM
5. Cost versus benefit/sales volume - Can Chiefs really be commercially made at any useful sales volume or profit margin? Kevin's Chief has set the bar in Chief size and quality that may never be beaten. But could he make an order of, say, 250 units, and make anything like a profit? I would estimate no, it would not be a profitable commercial product.
I'll address that, while noting that yes, just setting up a Newtonian properly defeats a lot of people.
As a mirror maker, there's mostly one surface (the primary) that I'd make any profit on. The other components are farmed out (certainly in the case of Kevin's 17"). There's just not enough return from a long f/ratio primary, even with hyperboloid correction, to make it worth pursuing. Yes, one for myself, cool, I'd like to have it. Try to make them to sell (optics sets or finished scopes), no way. The user support could indeed be a killer.
CO vs no CO? Definitely I come down on the unobstructed side. But I have my own redesign of the Stevick-Paul on my list that's mountable and all mirrors, something I'm make first at a 14" size. It has the advantage...wait for it...that I fiddled around optimizing a new take on the SP that could be supported in a standard sort of dob structure.
I'd like to see the Traveling Chief Road Show. Set that thing up at OSP next fall and there'll be a LOT of interest. But until the eyes meet the EP it's difficult to commit the units that commercial manufacture would require. This is one for the converts, long standing or newly minted from handy materials...
Kevin has done a great thing in making the lens-box assembly available to anybody at about his cost, I think he's right that this simplifies it to the point of ease. Not sure if he's publicized that very much yet - uhm, or if he really intended that and wasn't just talking to me - though we have discussed it. But the $2.5K or so for the 17" lens set (less in qty) is still a stickler, and ya know those probably really do need to be coated for throughput (not reflections) and that's pricey.
This is not in any particular order. But I'd like to see Kevin talk on about his experiences with this thing because he's the one that's been pushing on with it to see the fulfillment of the no-compromise large unobstructed design that this is.
Posted 02 January 2013 - 04:41 AM
Why no interest in the Ed Jones Chief design ?
A question for you Kevin.
Would you have your 20" Chief if you didn't have Ed to make the lenses?
Posted 02 January 2013 - 06:47 AM
Posted 02 January 2013 - 07:54 AM
Posted 02 January 2013 - 10:11 AM
Your 17" Apo-Chief has a long-radius convex secondary, which forces your bend angle to a single value. But combined with the hyperboloidal primary, the convex secondary was what allowed the last bit of correction over your FOV.
Kevin, I think the 17" Apo-Chief you have built is one of the most remarkable achievements in ATM history, right up there with Russ Porter's Springfield mount, TCT's like the Stevick-Paul and Schupmann, the Houghton and Schmidt configurations, and the Dobson mount. I would say its design and fabrication may remain unique in history, even with the other Chiefs being built.
I agree with Mark Cowan that it's well worth taking around the country and showing at major star parties. I don't know when, but I do look forward to viewing through it on some still, quiet night with good seeing and transparency.
Posted 02 January 2013 - 10:38 AM
Posted 02 January 2013 - 10:47 AM
He has given a ton to this project in time and expertise as have others. I love the giving nature of the folks in this group.
Posted 02 January 2013 - 11:40 AM
Posted 02 January 2013 - 03:55 PM
As a mirror maker, there's mostly one surface (the primary) that I'd make any profit on.
OK Mark, here is an idea that seems largely forgotten: The Sasian unobstructed Newtonian as published in Sky & Telescope March 1991?
For those not familiar, it used a tilted 6" f/9 paraboloid. The secondary mirror was ground with a torodial surface and mounted to pass light back across the tube to the focuser. Like the Chief it is unobstructed, but does not result in much (if any) length reduction compared to a standard Newtonian. It generally resembles the DGM off-axis Newtonian, but without the waste inherent in creating the daughter mirrors.
That would give you two pieces of glass fabricate and sell (one of them being very unique), and a layout that would be generally familiar to most users. I would imagine support efforts would be quite reasonable.
Posted 02 January 2013 - 04:05 PM
My problem is time. I'm still finishing the 17.5" dob that my father-in-law started. Then I have an 8" Cave to do some resoration on. Oh and I really want to rebuild the 13.1" Coulter. So the Chief is last in line and I don't know when I'll get started on it.
I would like to know if I can get off the shelf lenses for the project. I might even go ahead and get them now and layout the design. But it'll be sometime before I actually start building it.
Posted 02 January 2013 - 09:15 PM
Yes it may be possible to make a 12.5 inch F/8 Chief. Ross Optical has a 3 inch diameter negative lens of the right focal length. It can be matched up with a 60 mm convex lens (no one makes a matching 3 inch convex lens). I've never tested any Ross Optical lenses so I don't what quality they make but in theory it works.
Posted 02 January 2013 - 11:50 PM
For those not familiar, it used a tilted 6" f/9 paraboloid.
Just a bit small. An awful lot of unobstructed designs don't scale up well, and really (just my opinion) the interesting ones are the ones that do - SP, CHief, Schupmann, and maybe one other that I can't recall offhand...
Posted 03 January 2013 - 08:46 AM
Posted 03 January 2013 - 11:08 AM
The Sasian unobstructed Newtonian actually used a F12 primary.
I have the original telescope shown here:
The optics need to be remounted in something less flimsy. If anyone is interested in it send me a PM.
I remember that scope and article. That would be splendid on a Springfield mounting.
Posted 04 January 2013 - 11:33 AM