GlenM
Vendor
Reged: 05/20/07
Posts: 1738
Loc: Lancashire UK
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Well, I can't fight it any longer. I would like to build a longish focal length refractor. I am looking at 5" f/12-f/15. I have e-mailed D&G about a lens and cell. No word back yet. I am wondering if there are any other suppliers who you guys have tried and can recommend just in case I need to.
This is my first foray into refractor building. I have built quite a few Dobs though. My heart is into refractors so I've got to do one.
I will be obliged for any help.
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Glen
www.lyraoptic.co.uk
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Gary Fuchs
scholastic sledgehammer
Reged: 05/22/06
Posts: 867
Loc: Easton, PA, USA
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Glen,
I understand you want to make a refractor, but have you considered a Schief?
You'd get an even longer focal length, ie f27 - so more magnification out of long eyerelief relatively simple design eyepieces, no false color, easy collimation (much easier than a Newt), probably lighter weight and a shorter OTA, and a lower (maybe much lower) cost.
Here's Dave Groski's and mine at this year's Stellafane:
(I believe Dave had his on Venus at mid-day - not sure if that's the case in this shot though it looks like it - and it looked fine.)
Gary
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GlenM
Vendor
Reged: 05/20/07
Posts: 1738
Loc: Lancashire UK
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Hi Gary,
I've not done any research on this system before. I have seen a few though. Certainly interesting. I don't really want to go down the road of making my own optics. Are there suppliers of optics for this system?
Thank you for the link.
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Glen
www.lyraoptic.co.uk
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John Jarosz
Astro Gearhead
Reged: 04/25/04
Posts: 2287
Loc: Chicago area, IL
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A 5" F12 or so refractor is going to need a really robust mount. Have you considered building it as a folded refractor? Not as classic in appearance as a traditional design, but the length is much more manageable. You do need a good flat mirror that's half the diameter of the objective. It would be an extra cost, but I think the shorter length would allow the scope to be used more often.
John
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6" F4.6(w/Paracorr) GEM reflector, 8" F11 Dall Relay Scope
6" F5 RFT Refractor, Garrett Gemini 20x80 LW
Edited by John Jarosz (08/19/09 07:32 PM)
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Mark Harry
Post Laureate
Reged: 09/05/05
Posts: 3124
Loc: Northeast
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Gary, your pics aren't showing. Format too large?
Mark**************
NEVERMIND! they are now. (?!@#*)
Didn't know the other was yours!
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So many projects, so little time!
Edited by Mark Harry (08/19/09 07:41 PM)
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Gary Fuchs
scholastic sledgehammer
Reged: 05/22/06
Posts: 867
Loc: Easton, PA, USA
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Hi Glen,
Quote:
Are there suppliers of optics for this system?
I don't know if there are any current off-the-shelf suppliers of Schief optics though there is at least one manufacturer of complete scopes on the continent, just can't recall the name right now. There are a few CN'ers here that should be able to make you a set.
As for the mechanics, there are some things to pay attention to, and obviously it's not Newt-like, but on the whole I think comparable or even easier to build than many common Newt designs, though not as simple as putting a cell on a tube, some baffles and a focuser on the other end...
(I think - and there's been a good amount of discussion about this, much of it by people who haven't made them - that a Schief set can be a fairly challenging project for your first mirror; but if you have some experience and avail yourself of guidance, very doable.)
Gary
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Gary Fuchs
scholastic sledgehammer
Reged: 05/22/06
Posts: 867
Loc: Easton, PA, USA
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Mark,
Sorry for any trouble with the pics. Maybe some issue with my host? Sometimes they come up normally and sometimes I have to refresh or reload the page.
I heard you were at Stellafane. I was hoping to say hello to you and Kevin Frederick at least and put some faces together with names. Next year...
I had my scope on the hill near Dave's Schief and 6" f4 and Matt Considine's Schupmann on Saturday, and right outside the clubhouse next to Dave's scopes and Dick Parker's refractor on Friday night.
Gary
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timo4352
super member
Reged: 04/16/07
Posts: 160
Loc: Northeast Ohio
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Hi Glen
This group will help fuel that urge:
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/?yguid=332121599
Tim
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Orion 3.6CA Reflector
and 2 homebrew scopes --
8" Hubble Bubble ballscope
8" F/8 CHief - nearing completion 
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polaraligned
sage
Reged: 12/26/08
Posts: 229
Loc: P. R. of New Jersey
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A 5" at f/12 or even f/15 will be OK on a G11 mount if you use a Hargreaves strut. D&G makes excellent doublets.
Plenty of people here who can help you. Go for it!
Scott
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GlenM
Vendor
Reged: 05/20/07
Posts: 1738
Loc: Lancashire UK
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I have had an e-mail from Barry at D&G giving me a time line for a 5" f/12. It's 6-8 months. I suppose it would give me time to get things organised.
Thank you all for your suggestions and links so far. I am finding the options very interesting.
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Glen
www.lyraoptic.co.uk
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kfrederick
professor emeritus
Reged: 02/01/08
Posts: 664
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get hold of ED JONES and go CHief he has a great 6 inch that maybe he will sell /bet it will SMOKE that refractor /in every way /smaller /no color /no obstruction/ kevin
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Mike I. Jones
Carpal Tunnel
Reged: 07/02/06
Posts: 1572
Loc: Fort Worth TX
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Glen,
I'm actually surprised Groski hasn't honked his Schupmann horn at you as well 
Rather than choosing one configuration here, I'd say follow your initial desire and make that refractor, THEN the Schief, THEN the Chief AND the Schupmann!
Newport Glass sells pregenerated 4", 6" and 8" achromat kits with full tooling at http://www.newportglass.com/angwcat.htm. My recommendation: do the 6" aperture AAB6.15 kit. Twice the light for the same amount of effort.
Also, go back through the ATM forum and look for James Champagne's very thoroughly documented story of building his 6" refractor as part of his Physics degree. PM him and get advice from him, he's a great guy.
I just joined the Yahoo http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ group and there's a lot of good info there as well.
I agree on the performance of the alternate configurations suggested, they are all great scope designs. But they are simply well-meaning recommendations - you should build exactly what you want. I made a 6" f/10 achromat myself and yes, the secondary spectrum is there, but it still gives beautiful images. A Schief, Schupmann and Chief are all on my to-do list as well.
Mike
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56 mirrors, lenses, 16" f/6 Newt, 6" f/10 refractor, TOA-130S, Tinsley 5" f/15 Mak, 6" f/4 RFT, Coronado PST. Still to build: 24" f/10 Modified Dall-Kirkham, 10" f/26 Mak, 8" f/12 apo, spectrohelioscope, Herrig, Schupmann, and others.
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GlenM
Vendor
Reged: 05/20/07
Posts: 1738
Loc: Lancashire UK
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I think I'm going to join the Yahoo group and see how it works out. I have been speaking to a couple of people today and they have said to go for the f/15 version. I think they could be right.
I will also be making my own alt/az mount for the scope.
It is good to hear all the views of the dedicated people on CN. What an excellent site. I am delving into past threads tonight.
My better half found out about the project today! I had to mention it due to the fact a large piece of aluminium tubing may be turning up in the next few days. The eye will soon heal.
All suggestions are welcomed.
Thank you all 
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Glen
www.lyraoptic.co.uk
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8330
Loc: Bremerton Washington
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Quote:
I think I'm going to join the Yahoo group and see how it works out. I have been speaking to a couple of people today and they have said to go for the f/15 version. I think they could be right.
I will also be making my own alt/az mount for the scope.
It is good to hear all the views of the dedicated people on CN. What an excellent site. I am delving into past threads tonight.
My better half found out about the project today! I had to mention it due to the fact a large piece of aluminium tubing may be turning up in the next few days. The eye will soon heal.
All suggestions are welcomed.
Thank you all
Glen..go for it. 5"f/15 is a great performer and still retains that eligant refractor feal/look. It's objective is farely forgiving in its design and fabrication. I have a pretty slick website I will find that helps you all along the way to building your scope.
The Yahoo group is dedicated to those who build their own and there is plenty of help and encouragement there.
I too am building a 10"f/15 along with many other things.
My intent is to build the ojective myself. Currently I purchased an objective..but am going to make the 10"f/16 for another scope on the books.
Rob
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www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8330
Loc: Bremerton Washington
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Glen...check this website out and save it as a favorite...it is extremely helpful in fabriaction of your scope.
http://bobmay.astronomy.net/refractor/Refrindex.htm
Rob(good luck)
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www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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Gary Fuchs
scholastic sledgehammer
Reged: 05/22/06
Posts: 867
Loc: Easton, PA, USA
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Quote:
I will also be making my own alt/az mount for the scope.
Do you mean one that tracks? If not, at modestly high magnifications for a 4" or 5" (~125X - 175X or more) I find it very distracting to almost constantly reposition. And with the adjusting a 5 or 6 foot scope will probably take a bit of time to settle.
For example, when we set up Friday night at Stellafane two of Jupiters moons were tough to separate staying put; it would have been much harder or impossible manually moving the scope.
My Schief is probably as heavy as your refractor will be or close, though shorter, and while I'd like more it does okay on an old RV-6 GEM.
Gary
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 8330
Loc: Bremerton Washington
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Quote:
Quote:
I will also be making my own alt/az mount for the scope.
Do you mean one that tracks? If not, at modestly high magnifications for a 4" or 5" (~125X - 175X or more) I find it very distracting to almost constantly reposition. And with the adjusting a 5 or 6 foot scope will probably take a bit of time to settle.
For example, when we set up Friday night at Stellafane two of Jupiters moons were tough to separate staying put; it would have been much harder or impossible manually moving the scope.
My Schief is probably as heavy as your refractor will be or close, though shorter, and while I'd like more it does okay on an old RV-6 GEM.
Gary
Gary...did you grind your secondary against the primary to get its curve correct?
I have an 8"f/13 mirror I'm considering using for a Schief.
Rob
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www.goldmtobservingcenter.com
A great place for amateur astronomers, and ATM's to come and enjoy their hobby.
http://tech.groups.yahoo.com/group/HomemadeRefractorTelescopes/ My homemade refractor group.
www.vimeo.com/6014031
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GlenM
Vendor
Reged: 05/20/07
Posts: 1738
Loc: Lancashire UK
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Gary,
I don't intend to make the alt/az a tracker at the moment. This of course may change in the future.
Rob,
Thank you for the links. Plenty of reading to do.
I didn't really want to grind my own lens. Just depends how this project goes. You never know.
Thank you all
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Glen
www.lyraoptic.co.uk
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Gary Fuchs
scholastic sledgehammer
Reged: 05/22/06
Posts: 867
Loc: Easton, PA, USA
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Quote:
Gary...did you grind your secondary against the primary to get its curve correct?
Hi Rob,
Yes. Glass on glass. Then polished the concave primary and tested for sphericity and radius with knife edge and Ronchi. Then polished the convex secondary and interference tested it to match the curve of the primary.
Gary
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Gary Fuchs
scholastic sledgehammer
Reged: 05/22/06
Posts: 867
Loc: Easton, PA, USA
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Quote:
I don't intend to make the alt/az a tracker at the moment.
Rob, you have a long refractor or two don't you? What do you think about tracking vs not for high magnification viewing?
Gary
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