Why no CHiefs intrest???
Posted 31 December 2012 - 08:10 AM
Posted 31 December 2012 - 09:03 AM
Posted 31 December 2012 - 09:23 AM
Posted 31 December 2012 - 09:29 AM
Posted 31 December 2012 - 11:04 AM
Posted 31 December 2012 - 11:08 AM
So all you experts Here is your question. Why no interest in the Ed Jones Chief design ?
Doesn't Ed have a book on this is the works?
I am interested, but am waiting for his book, so that I can take the full benefit of his insights and designs. (I hope this will encourage Ed in his book project, here is a guaranteed sale.)
(And in the meantime have other, more elementary, projects I have not gotten to yet.)
Posted 31 December 2012 - 11:30 AM
Hmmmm, I usually can't use 'lenses' and 'easy' in the same sentence, particularly if those lenses need to be tilted and aligned to an optical axis without clear reference points. It is a neat design, but beyond what I can do with the simple tools I have.
Posted 31 December 2012 - 01:07 PM
Posted 31 December 2012 - 01:28 PM
I was thinking of an 8" Chief. Could an f/8 or faster Chief be made with off-the-shelf lenses?
Posted 31 December 2012 - 04:54 PM
Posted 31 December 2012 - 05:32 PM
Actually I think so. I haven't worked a design yet but I found a lens combination in my latest Zemax catalog (or else I just missed it before) that might work for an 8 inch F/8 maybe F/7. Stay tuned, I post it on spiderless.
Posted 31 December 2012 - 08:01 PM
Posted 31 December 2012 - 08:27 PM
K, every day is a New Year gone by. Something to think about.
Not sure why we cheer on New Years .Another year gone .Any way Happy loss of another year.Bucket list telescopes would be a good post . I have mine.
Posted 01 January 2013 - 08:58 AM
Posted 01 January 2013 - 09:14 AM
Posted 01 January 2013 - 09:41 AM
Posted 01 January 2013 - 10:52 AM
1. Eyepiece is located farther down the tube and more convenient.
2. Less of the light path crosses through itself, thus reducing in-tube convection effects. The path from the primary to the secondary shares part of the path of the incoming parallel light, and an even smaller portion is common between the primary and secondary path, and the secondary to L1.
3. The cost for the two small corrector lenses is less than a full-aperture 1/20 wave optical window for a 17" to 20" optimized Newt.
4. Ghost reflections are essentially absent, as all optics are operated off-axis.
5. Commercial lenses can be used for smaller instruments, further reducing cost.
The disadvantages of a Chief that I see limiting or prohibiting it from commercial interest are:
1. Alignment sensitivity
2. Structural stiffness required to maintain alignment over all pointing angles from near-horizon to zenith.
3. A required skill level in collimation that may not be present in beginning telescope owners, who can barely keep a Newt properly aligned if at all.
4. Requires an Amici or pentaprism to give an image without reversion. By itself, the Chief optical system acts similar to a Cassegrain with an off-center pupil, and gives an inverted image. Using a fold mirror or prism flips the image across one axis, but not the other. It would take a pair of reflections from a pentaprism or pentamirror to restore the image to simple inversion. The Amici prism would give an erect image without inversion.
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.
The Chief does work, and is an admirable project for advanced ATM's like Ed and Kevin, but I'm not seeing it as attractive to a commercial dealer wanting to make a 10% profit margin. I also see it as very intensive post-sale support in trying to work with customers to align their scopes. I could also be completely full of it, and there might be mass-production techniques that haven't been developed yet that could actually give a 10% profit and reasonable cost and delivery.
Posted 01 January 2013 - 10:54 AM
So all you experts Here is your question .Why no interest in the Ed Jones Chief design ?
Firstly, the premise of your question may not be valid. Adoption of new ideas in telescopes takes some time. Cases in point: Roland Christen was publishing designs and building apochromatic refractors in the early 1980's, yet the scopes did not become wildly popular until late in that decade. IIRC, even into the (very) early 1990's the "wait list" for one of his scopes was barely longer than the fabrication time. Another case in point: John Dobson was building and showing his alt/az Newtonians in the late 1970's. The earliest reference I could find of one appearing at a star party was either 1979 or 1980 Riverside (I can't recall the exact year off the top of my head) where he won a 1st prize award. His scope was (technically) a very small leap yet manufacturers (and amateurs) didn't adopt it in numbers until much later in the 1980's.
I prize the performance of long focus mirrors, and think the Chief would be great. I am very tempted. But I haven't done one yet. Looking at the Chief deign specifically, here is what I see:
1) Every design appears to be "custom". Not only does one have to take into account aperture and focal ratio (like a Newt), but the angles may be different depending upon the ideas of the builder, and the lens prescriptions and tilts change. Very few amateurs today grind their own mirrors, and amateur lens makers could probably be counted on two hands. Meanwhile, in a Newtonian a flat is always a flat, and widely available.
2) To derive these solutions, one must have optical design software. Not only is software cost a hurdle, but I would question my own ability to understand it and derive valid data from it. Not being an optician, I would fear being nothing more than a chimp banging on on a piano. It would not be a happy day to finish a $1,000+ project only to learn it was fatally flawed from the drawing board.
3) I am in the minority in my appreciation for long-focus mirrors. As such, I have a 16" f/7 "laying around" that could be re-purposed. Or, I would seriously consider spending money (or time) to acquire a more suitable one. Most astronomers today have (or want) short mirrors that would be unsuitable to the project.
4) The fabrication challenges probably deter many. I have built many scopes and enjoy working with wood, but even so my shop is relatively simple. And I have no metal working capability or experience beyond a hacksaw, drill press, and a couple of thread taps. Any metal components or optical carriers would have to be farmed out to a custom machinist. Certainly easy to find, but not low-cost.
Posted 01 January 2013 - 12:10 PM
Posted 01 January 2013 - 01:13 PM
On a different thread (the Herrig) the light crosses its own path three times, but convection effects were never mentioned, IIRC. How damaging are such effects?
Less of the light path crosses through itself, thus reducing in-tube convection effects
Posted 01 January 2013 - 01:29 PM
Posted 01 January 2013 - 03:17 PM
If there is enough demand for a product people want someone will produce it.
Posted 01 January 2013 - 03:30 PM
Yes, Mike, the paths are shorter but there are more of them in this case. I was hoping you could direct me to a study done on the effects of path crossing, rather than tell me to wait for your to build the Herrig - given that the Herrig is last on your bucket list! Gee, then, I guess neither one of us knows how bad this path crossing is, do we? I'll look elsewhere. Thanks.
Th mutual paths are a lot shorter than for a Newt. I'll let you know when I build my 8" Herrig.