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magic612
professor emeritus
Reged: 09/30/08
Posts: 561
Loc: Somewhere south of Chicago, IL
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So I'm now the (proud?) owner of a 127mm diameter, f/4.4 focal ratio lens. It's supposedly an achromat, and from the way it focuses during the day with my 32mm Plossl, I'd say it has decent color correction for such a fast lens. I bought it because I calculated that I ought to be able to make a very wide-field telescope with a 3 or perhaps up to 4 degree field of view. And, I got it for $40.
The gentleman whom I purchased it from indicated he got it as a surplus lens 40 some-odd years ago. It does look to have some purple anti-reflective coatings on it. He had it set up as a straight-through system, which even for a "young" guy like me (age 39), I think would be a bit hard on the neck. He said that the fixed eyepiece he had on it was an 18 or 25mm Erfle, but given it's rather narrow apparent FOV, it doesn't seem to be one. Anyway, the outer 25% of the field gets rather "soft" with that eyepiece; it looks much better across the field with my Plossl.
So I was planning on making a "cradle" for it so that I can use this scope on the tripod/mount I made earlier this year. I'm thinking of using some leftover 6" ID PVC pipe I have for the tube of the scope, setting it further back inside the pipe to make for a built-in dew shield. At the back of the scope, I thought I'd pick up one of these mirrors from Surplus Shed and angle the light cone up and out at a 90 degree angle (much better on the neck!). And given that I'm not likely to change eyepieces on it, I thought of using a "fixed" eyepiece (not sure what to use yet, but this eyepiece look interesting), with a simple plumbing hardware fine-focuser on it.
I'll likely flock the whole tube, and probably just put a very simple sighting system on it, given it's wide field.
Any other thoughts? Anything I should look out for on a lens this large/fast? Other ideas?
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- Celestron C8+, Orion 90mm f/10, Orion ST-80, 5" f/8 Dob, 127mm f/9.4 refractor, 114mm f/8 on DS GoTo, 60mm Sears 6333-A, 127mm f4.4 refractor lens (current project), 12" f/5 mirror (future project)
- Orion Vista 10x50s (5 deg), Sears #6207 7x35 (7 deg), Jason #138 Statesman 7x35 (11.5 deg)
Yes, I'm addicted to telescopes and binoculars. I am getting help. Every time I look at the heavens, it helps.
http://www.eyesonthesky.com
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Mike Lynch
member
Reged: 04/07/06
Posts: 52
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Let me offer you my thoughts on this....
I recently received of one of Surplus Shed's 127mm, f/5.5 lenses, and I took a relative "minimalist" approach to building a rich-field scope from it.
I happened to do EXACTLY what you suggested with 6" ID PVC pipe. I've put the lens inside the pipe for both the "built-in dew shield" aspect as you mentioned AND because I thought this heavy achromat lens and its cell would be more safely mounted that way.
I attached a PVC reducer on the focuser end of the PVC pipe and am now figuring out the best way to get a standard Synta-type 2" focuser from another telescope mounted in it. I've JUST ABOUT gotten that part figured out, too.
After I've painted all the PVC and determined how I plan to mount the scope on my Orion Astro View EQ mount, I'll be ready to go! (I'll probably just use two screws to attach it through the holes in the mount's cradle. I drilled holes in the PVC main tube to set it up and test to insure the length I had cut it was appropriate. And why make it more complicated?)
I plan to use the set-up for binoscoping; I already have the binoviewers and several sets of matching eyepieces.)
I may add a flexible handle to the top of the finished OTA, since this thing is HEAVY!
Hope my experience helps! Good luck on the build...
Mike Lynch
Frankfort KY USA
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Mike Lynch
member
Reged: 04/07/06
Posts: 52
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Oh, yes.... One more point.
Look at the list of topics in this DIY forum for at least two other threads on how others have built a scope from this 127mm, f/5.5 lens. You'll see "127mm" or "Surplus Shed" in the name of the threads.
Some of these guys have taken their time and fashioned some great scopes from it!
Mike Lynch
Frankfort KY USA
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jog
member
Reged: 10/26/06
Posts: 90
Loc: nj
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can you post a picture of the scope?
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Mike Lynch
member
Reged: 04/07/06
Posts: 52
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Right now (LITERALLY!!) I'm in the process of spray-painting the PVC tube exteriors for this scope and an 80mm Short Tube I've made for a friend, using Surplus Shed's $39 lens.
I'll post some photos as I get close to completion... perhaps tomorrow(?)
Incidentally, for the orignal poster and other viewers, I have some adhesive flocking paper I bought from Scope Stuff for the interior of the 127mm scope. I've used it before, and really liked the results.
I've spray-painted the interior of the 80mm with flat black paint. This 80mm is essentially a little brother of the 127mm... put together in much the same way as the larger one with a PVC pipe and reducer for the focuser.
Mike Lynch
Frankfort KY USA
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magic612
professor emeritus
Reged: 09/30/08
Posts: 561
Loc: Somewhere south of Chicago, IL
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Hey Mike - great stuff! Sounds like we do have similar ideas on how to mount something along these lines. I'll check out those other threads too (I think I perused one of them a couple weeks ago, now that I think about it). One thing I am doing a little differently is just directly mounting an eyepiece to an eyepiece holder with some screw threads directly above the mirror I'll be using. Because it's so short (22" focal length!), I didn't want to vignette the field, and this way I'll get full aperture. With that 38mm Surplus Shed eyepiece I mentioned in my first post, I'd have a 14x magnfication, and over a 4 degree field; with my 32mm Plossl, it's 17x and just over 3 degrees. Either way, it'll be a nice, rich field!
Jog - pictures of what I purchased are below. Of course, I'll be doing some significant modifications to make it work for my tripod/mount.
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- Celestron C8+, Orion 90mm f/10, Orion ST-80, 5" f/8 Dob, 127mm f/9.4 refractor, 114mm f/8 on DS GoTo, 60mm Sears 6333-A, 127mm f4.4 refractor lens (current project), 12" f/5 mirror (future project)
- Orion Vista 10x50s (5 deg), Sears #6207 7x35 (7 deg), Jason #138 Statesman 7x35 (11.5 deg)
Yes, I'm addicted to telescopes and binoculars. I am getting help. Every time I look at the heavens, it helps.
http://www.eyesonthesky.com
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Mike Lynch
member
Reged: 04/07/06
Posts: 52
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David,
I can fully understand why you want to avoid vignetting the light path for your lens. And your web site shows that you are very into the DIY aspect of this great hobby.
Far be it from me (sincerely) to suggest there's a "better" way for you, but to be able to use as many eyepieces as you can with this scope, would you consider making a PVC focuser, too... as web page :
Perhaps a large enough PVC focuser tube, adapted at the eyepiece end to reduce to 1.25", would decrease the chances of the vignetting....?
Mike Lynch
Frankfort KY USA
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magic612
professor emeritus
Reged: 09/30/08
Posts: 561
Loc: Somewhere south of Chicago, IL
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Hey Mike -
At the moment, I'm not sure I want to be able to use as many eyepieces as possible. My reasoning for getting this lens/scope was to make a very wide field refractor somewhere between my binoculars and other telescopes. Since I already have an ST-80, I can technically get an even larger field (if I wanted). But the largest field of view my scopes will generally produce (minus the ST-80) is about 1.6 to 1.8 degrees. So I'm looking for the maximum possible FOV with the best image possible. This really will be a "specialty" scope to hit that 3-4 degree field of view "sweet spot" but with more resolving power than my 80mm scope has.
The other thing I'll have to consider is balance. Because the mount I've already made for my f/9.4 scope is a bit narrower than what I'll be able to make for this one since I'll be using PVC pipe, I'm not sure I'll have the ability to do much in the way of balancing once the scope is together/set in the mount (unless I use counterweights, but I'd prefer to avoid that if possible). By having a "fixed" eyepiece, that will minimize balancing issues, as the weight on the eyepiece end won't change. Then the only focusing required would be minor changes depending on the person viewing.
Besides, with the mount the way it is, I can swap this scope in/out with my longer f/9.4 in about 10 seconds flat. So if I need higher magnification/more contrast/a narrower field for a given object, it's a simple swap - and both lenses are the same diameter.
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- Celestron C8+, Orion 90mm f/10, Orion ST-80, 5" f/8 Dob, 127mm f/9.4 refractor, 114mm f/8 on DS GoTo, 60mm Sears 6333-A, 127mm f4.4 refractor lens (current project), 12" f/5 mirror (future project)
- Orion Vista 10x50s (5 deg), Sears #6207 7x35 (7 deg), Jason #138 Statesman 7x35 (11.5 deg)
Yes, I'm addicted to telescopes and binoculars. I am getting help. Every time I look at the heavens, it helps.
http://www.eyesonthesky.com
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magic612
professor emeritus
Reged: 09/30/08
Posts: 561
Loc: Somewhere south of Chicago, IL
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Okay, so I happened to be in the home improvement store today (how convenient that I had to buy housepaint!), and picked up a 1.25" to 1.5" PVC pipe adapter (these things are perfect for setting a 1.25" eyepiece into), a 1.5" pipe coupling and a 2' length of 1.5" pipe. I just may have to experiment with making a low-profile Crayford focuser.
Way to go Mike - you got me thinking about adding a focuser, and now I'm going to wind up doing more work on this scope and make it even nicer!  
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- Celestron C8+, Orion 90mm f/10, Orion ST-80, 5" f/8 Dob, 127mm f/9.4 refractor, 114mm f/8 on DS GoTo, 60mm Sears 6333-A, 127mm f4.4 refractor lens (current project), 12" f/5 mirror (future project)
- Orion Vista 10x50s (5 deg), Sears #6207 7x35 (7 deg), Jason #138 Statesman 7x35 (11.5 deg)
Yes, I'm addicted to telescopes and binoculars. I am getting help. Every time I look at the heavens, it helps.
http://www.eyesonthesky.com
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Mike Lynch
member
Reged: 04/07/06
Posts: 52
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Heh-heh... I've been known to wander into the "telescope" section of some home-improvement and hardward stores myself. Actually get some good help when I explain what I'm looking for, too!!
OK, I've attached a couple of photos of the near-complete 127mm f/5.5 sewer, UH, I MEAN PVC, scope!! 
One heavy sucker!! may need to find a ring system to hold it securely to the mount!
I need to do some other refining, but one thing I like about this "design" is that, since the main lens is slightly smaller than the ID of tube, I should be able to do some collimation, if it's very far off.
The tube is pretty short because this setup will be used for binoviewing. I hope to get some looks at our partly-cloudy sky tonight to see how this works!
Mike Lynch
Frankfort KY USA
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Mike Lynch
member
Reged: 04/07/06
Posts: 52
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OK, perhaps I can't attache more than one photo at a time! Here's another!
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Mike Lynch
member
Reged: 04/07/06
Posts: 52
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Took the 127mm scope out for a short while as dusk was falling, but mosquitoes chased me back in before very long. I got some good sharp terrestrial views and views of clouds in the reddened western sky after the Sun went down. I was happy with those views.
Turned to the southeast to view Jupiter as it was rising higher. Not a real sharp view. Probably need some tweaking on the collimation. But, of course, this thing's going to do much better on deep-sky stuff (my favorite targets, 'specially planetary nebulae) than planets.
So far, so good. No major issues other than collimation and comfort that the heavy scope is securely attached to the mount! 
Mike Lynch
Frankfort KY USA
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magic612
professor emeritus
Reged: 09/30/08
Posts: 561
Loc: Somewhere south of Chicago, IL
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Mike - looks good! You sure it's not vignetting the edge of the field though?
I took mine out (well, in the condition I bought it, see photos above) and placed it against my present mount to steady it so I could take it for a "test drive." Considering that the edges of the field looked soft during the day with the current eyepiece, I was pleasantly surprised at the nice focus it achieved at night. I'm definitely looking forward to adding a focuser and using my 32mm Plossl now. In between doing some more house painting, I'll hopefully get some work done on a Crayford focuser for it. I've drawn my proposed idea in AutoCAD of what I'd like to make (see attached PDF file); any feedback on that would be most welcome.
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- Celestron C8+, Orion 90mm f/10, Orion ST-80, 5" f/8 Dob, 127mm f/9.4 refractor, 114mm f/8 on DS GoTo, 60mm Sears 6333-A, 127mm f4.4 refractor lens (current project), 12" f/5 mirror (future project)
- Orion Vista 10x50s (5 deg), Sears #6207 7x35 (7 deg), Jason #138 Statesman 7x35 (11.5 deg)
Yes, I'm addicted to telescopes and binoculars. I am getting help. Every time I look at the heavens, it helps.
http://www.eyesonthesky.com
Edited by magic612 (09/08/09 09:35 AM)
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Mike Lynch
member
Reged: 04/07/06
Posts: 52
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Good luck on your build....especially if you have to attend to those pesky little chores like housepainting!!
Are those baffles in your drawing? I've flocked the entire interior of my tube, but I wondered if baffles would make a difference.
While I dont' THINK it's cutting off the edge of the light cone, I need to take the time to simply draw a ray-trace diagram to see how it "calculates" out.
Dumb question (maybe): If you can see the inside edges of the lens cell while looking through the mirror diagonal without an eyepiece, is that any quick indication about such vignetting?
Mike Lynch
Frankfort KY USA
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magic612
professor emeritus
Reged: 09/30/08
Posts: 561
Loc: Somewhere south of Chicago, IL
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Mike - yes, baffles in the drawing. I honestly haven't fully decided whether to include them or not, but I figured I should draw some in case I do incorporate them. I was going to go the 100% flocking method too, but decided that baffles wouldn't hurt, either.
I not entirely sure of the answer to your questions, but I suspect that you'd need to see the inside edge of the lens cell that are *inside* of the lens itself (in other words, the portion of the cell that is closer to the diagonal). Your lens is set a ways back into the cell, so it's possible you're seeing that "forward" portion of it. Without doing a ray-trace, I'd think you'd need to place a circle the size of the smallest field stop of the eyepieces you plan to use for the scope, and set it approximately where that field stop would sit when the eyepiece is in.
THEN when you look into the mirror diagonal, if you can see the back portion of the lens, that might (and I emphasize, *might*) mean you're getting full aperture. But those who are smarter about this stuff would answer that better - I'm honestly giving you my best guess! That's also why I drew mine out, so I could ensure I'd be getting full aperture.
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- Celestron C8+, Orion 90mm f/10, Orion ST-80, 5" f/8 Dob, 127mm f/9.4 refractor, 114mm f/8 on DS GoTo, 60mm Sears 6333-A, 127mm f4.4 refractor lens (current project), 12" f/5 mirror (future project)
- Orion Vista 10x50s (5 deg), Sears #6207 7x35 (7 deg), Jason #138 Statesman 7x35 (11.5 deg)
Yes, I'm addicted to telescopes and binoculars. I am getting help. Every time I look at the heavens, it helps.
http://www.eyesonthesky.com
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Michael Miles
professor emeritus
Reged: 02/11/05
Posts: 677
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Hi Mike:
I've' got one of these lenses too. Since you've got the lens cell mounted backwards, did you remove and reverse the lens assembly?
Michael
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LXD-75 w/
Stellarvue 102ED
Hardin 10" Newt
Antares 8" Newt
Meade AR-5
Meade N-6
Celestron 102mm refractor
Canon 300D, Meade DSI guiding
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StarStuff1
scholastic sledgehammer
Reged: 04/01/07
Posts: 985
Loc: South of the Mason-Dixon Line
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An easy way to check for vignetting is to measure the exit pupil using an eyepiece of known focal length.
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Tools that make objects very far away appear much closer than they actually are.
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Mike Lynch
member
Reged: 04/07/06
Posts: 52
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Michael,
YES, I did do exactly that! But thanks for asking!
Since the cell fit more securely deeper inside the PVC pipe, and I wanted the dew- and glare-shield advantages of that setup, I carefully unscrewed the retaining ring, flipped the lenses together and re-attached the ring.
Have you built a scope with the lens? If so, what's the distance between the back edge of the lens and your focuser? (I realize you may have some posts on the "127mm Surplus Shed" threads here; I just haven't noticed all the names.)
Mike Lynch
Frankfort KY USA
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GlennLeDrew
Pooh-Bah
Reged: 06/18/08
Posts: 1288
Loc: Ottawa, Ontario, Canada
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For visual work, if you can get full illumination on-axis only, that's generally good enough. As long as the offending 'baffle', such as inner opening of focuser drawtube, etc., is more than about three field stop diameters in front of the field stop, illumination fall-off will usually be so gradual that you'll never be able to detect it.
Moreover, some light fall-off in fast 'scopes is actually a *good* thing, as this means some off-axis light passing through the edge of the ojective is being masked, and this does slightly improve edge-of-field sharpness.
To determine if the inner end of the drawtube is acting as an aperture stop (i.e., reducing the effective aperture for on-axis imagery), measure the distance from that opening to the eyepiece's field stop. If it's less than the drawtube I.D. times the objective's f/ratio, you're suffering a reduction in aperture.
For example, say the focuser tube's I.D. is 2" and your objective is f/5.5. The maximum allowable separation between eyepiece field stop and inner end of the drawtube is 2" x 5.5 = 11".
But it's easy to just look and see, *if* you can place your eye where the eyepiece field stop will lie (that is, at the focal surface.) You'll likely have to remove any diagonal, and then focus on a distant subject using a magnifier and rack the focuser until the drawtube's outer opening is *also in focus* with the image. Center your eye, and look for the actual edge of the entire objective to be visible without having to move your eye off-axis. As long as this condition is observed, you're fine.
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Home-made 11X50 right angle bino, 8.1 deg. FOV
Modified 26X100 bino, 3.5 deg. FOV
Home-made Mk II RA bino, using interchangeable objectives and eyepieces
My Gallery
Mediocre minds discuss people. Good minds discuss events. Great minds discuss ideas.
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Mike Lynch
member
Reged: 04/07/06
Posts: 52
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Thanks to ALL of you for your thoughts. I had a busy evening, and I won't have a lot of time to complete the measurements for a couple of days, but suffice it to says that it DOES look like I'm vignetting the light path from the lens in my 127mm scope, at least when it's racked in for some eyepieces, based on a ray trace drawing I've done. (That's obviously not a surprise to some of you!!  )
I need to carefully measure the location of my focuser tube end at its most racked-in position for my eyepieces and determine what's going on.
I THINK I can reduce the length of the tube, if that, in fact, can remove the "offending" length of it. Guess we'll see.
Mike Lynch
Frankfort KY USA
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Mike Lynch
member
Reged: 04/07/06
Posts: 52
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Well, after staying up late to get some yard work and required reading done, I came downstairs to take a look at my 127mm setup and determine what needs to be done about the focuser vignetting the light path. The answer appears to be elegant, simple, and one I didn't want: Flip the lens cell around (and, of course, flip the lenses themselves, too!) and attach the cell to the tube in reverse direction.
My ray-trace diagram indicates the focus-tube end will likely be far less of a problem and may need no shortening at all, since the lens will be significantly further away.
I'll determine for sure after I drill some holes in the bottom lip of the cell and securely re-attach it to the tube. I can determine if all my eyepieces can come to focus with this arrangement.
My hope to use binoviewers without an OCA, however, may have just evaporated! Guess we'll see!
So "Thanks!" again to those who asked that important question about vignetting. I think I have a better appreciation of why David's considering a fixed diagonal mirror and a permanent eyepiece! Avoids the focuser-tube vignetting possibility altogether!
Mike Lynch
Frankfort KY USA
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magic612
professor emeritus
Reged: 09/30/08
Posts: 561
Loc: Somewhere south of Chicago, IL
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Hey Mike - It's all about maximizing light-gathering capacity; good to hear that it sounds like you'll be getting full (or close to full) aperture. Hopefully the binoviewer will work too, and still come into focus.
Although I'm still going with the "fixed diagnonal" idea, I'm working on designing a low-profile Crayford focuser that has a large enough draw tube so the vignetting won't be an issue. It'll just take some "back and forth" with the main lens to determine the best spot to place it for optimal focusing.
Ah... well, I can get to that after the outside painting of the house and inside painting of the bathroom is done. Gotta love "vacations".... 
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- Celestron C8+, Orion 90mm f/10, Orion ST-80, 5" f/8 Dob, 127mm f/9.4 refractor, 114mm f/8 on DS GoTo, 60mm Sears 6333-A, 127mm f4.4 refractor lens (current project), 12" f/5 mirror (future project)
- Orion Vista 10x50s (5 deg), Sears #6207 7x35 (7 deg), Jason #138 Statesman 7x35 (11.5 deg)
Yes, I'm addicted to telescopes and binoculars. I am getting help. Every time I look at the heavens, it helps.
http://www.eyesonthesky.com
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Mike Lynch
member
Reged: 04/07/06
Posts: 52
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Heh-heh! I agree: Maximizing the light. When I get the new "flipped" set up finished, I may realize how much light I was MISSING with most of my eyepieces!!
Mike Lynch
Frankfort KY USA
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Mike Lynch
member
Reged: 04/07/06
Posts: 52
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Now, why didn't some of you people knock me in the head (gently, I would have hoped!) and tell me what was wrong with my thinking?! 
I'm back in business now with the 127mm f/5.5 refractor, and it finally dawned on me that my problem was that I wanted to use my binoviewers only, and didn't consider where the focus was going to be for cyclops viewing OR how much vignetting would occur for the binos. The focus tube was going to have to be in a particular location for each, no matter what! DUH! (Go ahead! Have a good laugh. It's my birthday weekend, and everyone should be partying and laughing!)
The photo shows my re-configuration. Lens cell pushed outside the PVC tube, and focuser in a position for cyclops AND bionoviewer use (but only with my Burgess 1.9x OCA.). The focuser tube is at or just outside the vignetting point for cyclops mode and just inside it for binoviewing. I'll probably carefully cut off the inside inch or so... or I could look for a shorter focuser.
Clouds and rain in the forecast for a couple of days... of course.
Mike Lynch
Frankfort KY USA
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magic612
professor emeritus
Reged: 09/30/08
Posts: 561
Loc: Somewhere south of Chicago, IL
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Okay, well after a long while of hemming and hawing over what direction I was going to take with the Crayford focuser I planned to make for this scope (read: procrastinating), I finally designed the focuser tonight. I'm satisfied with how it looks in CAD. I expect it should work fine, although the proof is always after it's built. I hope to get to that later this week, depending on kids' schedules after work.
I'm going for a very simple wooden Crayford, since I don't have much in the way of metal working equipment. But something along these lines seems practical and perfectly workable. So that's the direction I'm headed, with a few minor tweaks (adding ball bearings to the shaft, using PTFE tape for the pads).
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- Celestron C8+, Orion 90mm f/10, Orion ST-80, 5" f/8 Dob, 127mm f/9.4 refractor, 114mm f/8 on DS GoTo, 60mm Sears 6333-A, 127mm f4.4 refractor lens (current project), 12" f/5 mirror (future project)
- Orion Vista 10x50s (5 deg), Sears #6207 7x35 (7 deg), Jason #138 Statesman 7x35 (11.5 deg)
Yes, I'm addicted to telescopes and binoculars. I am getting help. Every time I look at the heavens, it helps.
http://www.eyesonthesky.com
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magic612
professor emeritus
Reged: 09/30/08
Posts: 561
Loc: Somewhere south of Chicago, IL
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Oops, almost forgot: I did cut and paint a section of PVC pipe for the new tube, but I'm not terribly happy with how it looks. But since the weather has cooled off significantly since then, I may have to put off a fresh coat of paint until sometime in the spring, unless we get a warm spell here pretty soon.
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- Celestron C8+, Orion 90mm f/10, Orion ST-80, 5" f/8 Dob, 127mm f/9.4 refractor, 114mm f/8 on DS GoTo, 60mm Sears 6333-A, 127mm f4.4 refractor lens (current project), 12" f/5 mirror (future project)
- Orion Vista 10x50s (5 deg), Sears #6207 7x35 (7 deg), Jason #138 Statesman 7x35 (11.5 deg)
Yes, I'm addicted to telescopes and binoculars. I am getting help. Every time I look at the heavens, it helps.
http://www.eyesonthesky.com
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gatorengineer
scholastic sledgehammer
Reged: 02/28/05
Posts: 882
Loc: Hellertown, PA
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Hey Mike,
Look at Siebert Optics for a zero Mag OCA.... Other suggestion is to try a prism diagonal, the light path is shorter than a mirror..........
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20" F5 Dob
16" Dob in pieces
Comet Catcher
MN71
12" Doc Clay Sky Patrol MEADE SCT
12.5" F4 Newt under construction
Siebert 45mm Binoviewers
Lots of binos---
Optics Past - 8" Stf Mak, 4" B&W triplet, 6"Schmidt newt, 12"LX200, C8, Meade LX10-10", 10" MEADE ACF, SN8, TAL150K, Orion 150MC, Jason 60mm refractor, ATM 6" F8, WO 110FLT, 92mm Off Axis Newt, Televue Genesis, Nikon 20x120 bino's, 15x110 Boarderguards, Kuhne Flaks
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Mike Lynch
member
Reged: 04/07/06
Posts: 52
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Interesting you should mention the Siebert OCA. I just picked on up on AstroMart; it's the 1.25x version, and it DOES work well! The increase in magnification is not objectionable, and the focus tube remains completely out of the light cone! 
Mike Lynch
Frankfort KY USA
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magic612
professor emeritus
Reged: 09/30/08
Posts: 561
Loc: Somewhere south of Chicago, IL
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Some progress today - I got the Crayford focuser made. It took longer than I'd hoped, but it looks nice too, and works surprisingly well considering it's a wooden one using PTFE (Teflon) tape for the bearing surfaces. Needs some paint and a more appropriate bolt for the tension, but other than that, it's good to go.
Mounting the lens in the tube looks like it might be easier than I initially anticipated, but I don't want to get too overconfident until I actually do it. But a few tests with some basswood strips gave me reason to smile. So hopefully I'll have time for that later this week. Then I'll need to build a rear cell that will hold the adjustments for the internal diagonal mirror.
More to come soon... 
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- Celestron C8+, Orion 90mm f/10, Orion ST-80, 5" f/8 Dob, 127mm f/9.4 refractor, 114mm f/8 on DS GoTo, 60mm Sears 6333-A, 127mm f4.4 refractor lens (current project), 12" f/5 mirror (future project)
- Orion Vista 10x50s (5 deg), Sears #6207 7x35 (7 deg), Jason #138 Statesman 7x35 (11.5 deg)
Yes, I'm addicted to telescopes and binoculars. I am getting help. Every time I look at the heavens, it helps.
http://www.eyesonthesky.com
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magic612
professor emeritus
Reged: 09/30/08
Posts: 561
Loc: Somewhere south of Chicago, IL
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Well, the weather finally warmed up a bit, so I managed to get the interior of the PVC pipe painted all flat black (though eventually it will get flocked), and the outside gloss black. Here's a couple pictures of the simple wooden Crayford focuser on the pipe section. The "bearings" are simply some PTFE tape on the wooden blocks, and I plan on changing the tensioning screw to a thumbscrew instead of the "washered" bolt.
Also, I should note that the PVC 1.25" pipe adapter works very nicely as a receptacle for 1.25" eyepieces - it's a simple compression fittings, so just pop the eyepiece in, turn the fitting, and it's tight/centered! All I did was place it into a simple coupling, which serves as the focuser tube. Just a bit of cleaning up of some minimal flash, and it's quite smooth all the way through it's motion. Oh, and I used some silicone tubing to give some "cushioning" between the carbon fiber rod and the PVC coupling. At the moment, some extra silicone tubing is holding the flanged ball bearings in place; I'll likely update those to something that will stay in place more permanently.
I'm pretty excited; can't wait to get this finished and try it out!
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- Celestron C8+, Orion 90mm f/10, Orion ST-80, 5" f/8 Dob, 127mm f/9.4 refractor, 114mm f/8 on DS GoTo, 60mm Sears 6333-A, 127mm f4.4 refractor lens (current project), 12" f/5 mirror (future project)
- Orion Vista 10x50s (5 deg), Sears #6207 7x35 (7 deg), Jason #138 Statesman 7x35 (11.5 deg)
Yes, I'm addicted to telescopes and binoculars. I am getting help. Every time I look at the heavens, it helps.
http://www.eyesonthesky.com
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GlennLeDrew
Pooh-Bah
Reged: 06/18/08
Posts: 1288
Loc: Ottawa, Ontario, Canada
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Nice job on that focuser!
How will the diagonal be supported?
If space and layout considerations permit, how about orienting the focuser so that the roller shaft is on the objective side? (Assuming your pics represent the back end of the 'scope's tube.) To me, it seems preferable to have less 'stuff' under one's nose and cheeks.
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Home-made 11X50 right angle bino, 8.1 deg. FOV
Modified 26X100 bino, 3.5 deg. FOV
Home-made Mk II RA bino, using interchangeable objectives and eyepieces
My Gallery
Mediocre minds discuss people. Good minds discuss events. Great minds discuss ideas.
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magic612
professor emeritus
Reged: 09/30/08
Posts: 561
Loc: Somewhere south of Chicago, IL
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Thanks Glenn!
I plan on supporting the diagonal from the tube cap that I'll have to make. It will essentially be like a reflector's secondary, except instead of having spider vanes to support it, I'll be able to use a solid piece of wood. Then I'll have collimation bolts in the back, to adjust the diagonal mirror.
Good point about orienting the focuser the other way - the tube hasn't been cut yet, so I can still manage that. I'll have to revisit the CAD drawing and double check how my diagonal support structure is set up, and if I have the room, I'll probably change that. (In the pictures above, the focuser is simply set on the tube for the photos sake.)
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- Celestron C8+, Orion 90mm f/10, Orion ST-80, 5" f/8 Dob, 127mm f/9.4 refractor, 114mm f/8 on DS GoTo, 60mm Sears 6333-A, 127mm f4.4 refractor lens (current project), 12" f/5 mirror (future project)
- Orion Vista 10x50s (5 deg), Sears #6207 7x35 (7 deg), Jason #138 Statesman 7x35 (11.5 deg)
Yes, I'm addicted to telescopes and binoculars. I am getting help. Every time I look at the heavens, it helps.
http://www.eyesonthesky.com
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magic612
professor emeritus
Reged: 09/30/08
Posts: 561
Loc: Somewhere south of Chicago, IL
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Well, I made a lot of progress on this the last few days:
- Focuser finished (and slightly upgraded)
- Tube cap with mirror completed
- Tube mount cut and assembled
- Lens cell installed properly
So, it was successful in the sense that "it worked." The focuser worked quite nicely (more on that later though). I was rather amazed at how many stars I could see with it! And - I was quite impressed with the lens overall - with my 32mm Plossl, stars were visible and seemed point-like out to the edge of the field - not bad for an f/4.4 refractor.
That said, there were some issues I need to fix. One, I merely "eyeballed" the secondary mirror, and given that bright stars displayed a "flared side" which seems to be caused from the slight mis-alignment of the secondary. But I didn't fix that yet because....
The tube mount hits the cradle I built specifically for my other 127mm scope (the f/9.4). So although I was able to "hand hold" the tube in place and view a few things that way, I could in no way shape or form use the scope as intended. It's my own fault, of course - I thought, "Hey, I'll just build it to the width of the other scope mount and it will work" - failing to account for the brace on the back of the cradle. It's not a difficult fix - I just need to reposition a wood brace - but it was enough to warrant a big:
So I couldn't collimate the secondary while hand-holding the back of the tube too. I'll get there, though.
The other minor issue was the PVC coupling I used for the focuser tube has a VERY slight angle to the outside surface. So when it moves slightly past the halfway point, it barely - but perceptibly - shifts. However, since I managed to place the focus at a point where the focuser need not move much, I think I've managed to avoid the need to have the focuser move past that point at all. It stays in a "non-shifting range" so to speak. My raytrace also showed that I'm presently not vignetting at all, but if I went to the 1.5" pipe, I would. So I think the minor problem is really not one at all. It simply required very careful lens-cell placement.
Overall, everything else worked well, and with a few minor tweaks, it ought to be in good shape. Like I said, I was VERY impressed with the views - an unobstructed 127mm view, even from light-polluted skies, was really amazing. LOTS of faint stars were visible, and I think with the secondary collimation and a smoothly moving mount, I'll have quite the nice scope.
It's not all that heavy, so although it's not quite "grab and go" (due to the large tripod I'll be mounting it on) it will still be very easy to transport and move. And the detail it showed now - uncollimated - gives me great hope for what I'll be able to see later when it's really tuned up! 
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- Celestron C8+, Orion 90mm f/10, Orion ST-80, 5" f/8 Dob, 127mm f/9.4 refractor, 114mm f/8 on DS GoTo, 60mm Sears 6333-A, 127mm f4.4 refractor lens (current project), 12" f/5 mirror (future project)
- Orion Vista 10x50s (5 deg), Sears #6207 7x35 (7 deg), Jason #138 Statesman 7x35 (11.5 deg)
Yes, I'm addicted to telescopes and binoculars. I am getting help. Every time I look at the heavens, it helps.
http://www.eyesonthesky.com
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