Michael Miles
professor emeritus
Reged: 02/11/05
Posts: 621
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Hi folks:
Figured I'd stir up the hornet's nest. Back in the 70's people built their own scope to save money. I think the same thing could be done today for a good astrophoto mount.
To that end, here's my parts list:
1) 7"x12" Homier lathe with 5" 4-jaw chuck and tools ($600)
2) Bunch of aluminum ($175)
3) Same gear and worm as used in CGE ($150)
4) dec drive and worm ($75)
5) 4 Tapered roller bearings ($40)
6) Roboscope drive and controller ($375)
7) Orion polar scope ($50)
8) Antares pier ($125)
And, at the end of that, you've got a metal lathe to spruce things up, invent new stuff, make a crayford focuser, make camera and insrument adapters, etc.
Besides, building the darn thing is fun!
I can post the web address for the parts, if there's any interest.
I'll check back on the nest later...
Hornet meister,
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
Edited by Michael Miles (05/02/06 02:17 PM)
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Michael Miles
professor emeritus
Reged: 02/11/05
Posts: 621
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or sell the lathe for $500 afterwards, and get a CGE quality mount for $1000...
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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Joe Cipriano
Entropy Personified
Reged: 09/03/05
Posts: 3830
Loc: Uh... anyone have a GPS?
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Michael:
Buzzzzzzzzzz.....
I can't provide definite proof (as I can't remember where I found the info), but the worm/wheel sets are WMBerg, at about $500 per set. Couldn't find info on the WMBerg site last I looked, as this was a contract deal with Celestron. Also, the worm wheel lower thrust bearings are about $35 each (need 2).
The shafts were true to +/-0.0075" (tested on V-Blocks with a run-out gauge), and are stainless steel; good luck getting that level of precision on a $600 lathe.
Runout on both top plates was lower than I could measure accurately (my run-out gauge is good to 0.001").
I wish you luck... 
Just buzzing 
--------------------
In the Land of Eternal Light Pollution & Great Pizza (Chicago)
SN-6, ED80, WO 66SD
Meade 208xt, SBIG ST-4
D70 (modified)
CGE (way modified)
A Wife who understands (unmodified)
Some other stuff...
I may not have gone where I intended to go, but I think I have ended up where I needed to be.
Douglas Adams
Edited by Joe Cipriano (05/02/06 03:37 PM)
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inaPICle
sage
Reged: 04/28/06
Posts: 278
Loc: Under cloudy skies in NH
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You forgot to add the cost metrology to that so add about another $300 or so for that if you plan to do a high quality job.
Also, you are only going to be able to make something pretty small on that lathe, so no CGE, maybe a CG-5 if you are lucky. You will not be able to swing enough metal to make anything close to a CGE. Also cheap lathes tend to suffer higher runout and end play. So overall precision will be low.
And your cost for quality tooling is way too. Typically for a good tool set you will be looking at around $1000.
You will also need a mill to accurately drill many of the holes. And also to make the dovetail head, unless you want to buy that too. And there are a lot of flat surfaces on a mount for dealing with altitude and azumith. If these are not pretty flat the mount will move and fall out if alignment when tightened down. The altitude adjustment is kind of hard to make with just a lathe.
And don't forget all the shafts will need to be precision ground. You won't get the accuracy you are looking for by turning the shafts on a cheap lathe. This is an astrophotography mount after all. And that would have to be steel, not aluminum, and you have to be sent out for hardening.
Of course in 1970 the quality bar for astrophotography was very low, at least by modern standards. These days with CCD imaging the bar is much, much higher.
You can get a CG-5 with goto for $750 that will knock the socks of any 1970's mount on a price/performance test.
So no contest. You won't get anything like a CGE for your money. In fact to tool up with something that could produce a mount like the CGE I would be looking at $10000 at least in tools and tooling, unless you got lucky in buying used equipment. And that is before the first piece of swarf is thrown off the machine.
Of course, not that it can't be done. There is a guy in the astronomical society I am in that did just this and built a mount something akin to a smaller MI-250. Of course has has a fairly large mill and a 12"x40" lathe.
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inaPICle
========
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Joe Cipriano
Entropy Personified
Reged: 09/03/05
Posts: 3830
Loc: Uh... anyone have a GPS?
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Yup.
Decent tool lathe (9x36 minimum) - about $10k
Mill with a 9x24 table - about $4k
8" horizontal/vertical Rotary Table for mill - about $500
Various measuring tools (calipers, micrometers, run-out gauges, etc) - $500-1000.
I'm just getting started...
--------------------
In the Land of Eternal Light Pollution & Great Pizza (Chicago)
SN-6, ED80, WO 66SD
Meade 208xt, SBIG ST-4
D70 (modified)
CGE (way modified)
A Wife who understands (unmodified)
Some other stuff...
I may not have gone where I intended to go, but I think I have ended up where I needed to be.
Douglas Adams
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Michael Miles
professor emeritus
Reged: 02/11/05
Posts: 621
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Jeez - I'm not hiring you guys to make my mount - I couldn't afford you! (My secrets to addressing the criticisms at the bottom .
To start with, here's my parts list (w/ web addresses):
1) 7"x12" Homier lathe with 5" 4-jaw chuck and tools ($600)
http://tinyurl.com/l4lq2
and the 5" chuck, measuring tools, cutting tools, boring bars, live center, drill chuck center: http://www.littlemachineshop.com/
details:Order detail:
Product Price Qty Amount
1243 End Mill Set, 6 Piece 4 Flute 13.95 1 $13.95
1700 Boring Bar Holder, 1/2" 9.95 1 $9.95
1247 Boring Bar Set, 1/2 Shank 17.95 1 $17.95
2412 Tool Bits, 5/16" Brazed Carbide Set of 5 16.95 1 $16.95
1237 Magnetic Base Indicator Holder 12.95 1 $12.95
2346 Lathe Chuck, 4-Jaw 5" with Adapter 93.00 1 $93.00
1222 Studs & Nuts 1.99 1 $1.99
1240 Edge and Center Finder 6.95 1 $6.95
Sales Tax: $0.00
Shipping & Handling: $23.52
Total: $197.21
2) Bunch of aluminum cut to length($175)
http://www.asapsource.com/public/index.asp
3) Same gear and worm as used in CGE ($190)
http://www.wmberg.com/
details:
ORDER DETAILS
=-=-=-=-=-=-=-=-=-=
Qty Item Price Total
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
1 W32B29-S180 $ 104.081 $104.08
1 W32S-3S $ 29.176 $29.18
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
SubTotal $133.26
2 B1-7 UNFLANGED RADIAL BALL BEARING
$17.619 $35.24
5 CS-5 CIRCULAR COLLAR CLAMP
$3.795 $18.98
1 S1-11 GROUND PRECISION SOLID SHAFT
$6.020 $6.02
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
SubTotal $60.24
4) dec drive and worm ($75)
http://www.apogeeinc.com/product.asp?itemid=683&catid=49
5) 4 Tapered roller bearings ($40)
http://www.vxb.com/page/bearings/CTGY/Tapered-Roller
6) Roboscope drive and controller ($375)
details here: http://groups.yahoo.com/group/RoboScope/
7) Orion polar scope ($50)
http://www.telescope.com/shopping/product/detailmain.jsp?itemID=165&itemType=PRODUCT&RS=1&keyword=polar+scope
8) Sky Instruments PD30 pier ($125):
http://www.handsonoptics.com/pts_skyinstruments.html
Ok, how does it work?
The tapered roller bearings are the secret. They are often used a precision references in machine shops. They typically have a 0.0001" runout. They are ground and hardened, and bear very heavy loads. I visited Parallax Instruments, and Joe uses tapered roller bearings in his 150 and 250 mounts. I built a very complicated EQ head when I was younger, but my Roboscope buddy and I have brainstormed a way to build a 50-75 lb. payload EQ head using just a lathe. The precision of the Homier lathe is quite sufficient for this application.
Anybody game?
Michael
--------------------
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
Edited by miniventures (05/03/06 06:21 AM)
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jrcrilly
Refractor wienie again
Reged: 04/30/03
Posts: 22739
Loc: NE Ohio
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Quote:
6) Roboscope drive and controller ($375)
details here: http://groups.yahoo.com/group/RoboScope/
Hi, Michael.
I'm a long-time member of that Group, which is dedicated to Autostar conversions. Is that what you are considering? The LXD55/75 motors/encoders might do the job if you can find 'em but I believe you'll find that the more readily available DS series units and the unobtainable DH series units lack both the torque and the encoder resolution to provide the performance of a CGE. Of course in either case the Autostar controller itself (though I like them) will be considerably less rich in operating features.
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John C
Urban Observatory
Tele Vue Pronto
A&M/Astreya 76mm F/6 APO
TMB/LOMO 80mm F/7.5 APO
Tak FSQ-106N F/5 APO
Meade 152ED F/9 "APO"
Meade 178ED F/9 "APO"
Tak CN-212 8" F/12 classical Cass/ F/4 Newt
Teeter 20" F/3.8 truss Newt w/ServoCat
LXD750, EM-200, CI-700
ST-10XME
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Strgazr27
Scope Junkie
Reged: 10/04/04
Posts: 6134
Loc: StonyHill Observatory
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I'll put my CGE up against it....Your using the Meade AS controller to be able to account for the different tooth count between the DEC and RA gears correct?
What part number are you using for the CGE Gears from WB? I ask as I got a quote of over $300 for the set.....
The bearings are nice but they are worth nothing if the shaft that rides in them is not as perfect along with the machining to mount them in.
Keep us posted on your progress 
--------------------
Bobby
StonyHill Observatory
Atlas w EQMOD
Vixen R200SS
Orion ED-80
AT-111
AT66-ED
QHY-8
SSAG
YAHOO TMB 130SS Group
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Michael Miles
professor emeritus
Reged: 02/11/05
Posts: 621
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Hi John:
Yes, I'm talking about the LXD55/75 motor/encoder units and Autostar. Granted, maybe not quite as snazzy as the CGE electronics, but you could easily substitute anything else if you built it yourself. I'm not claiming that you'll have a unit that's exactly like a CGE, but that will have it's functionality.
One of the nice features of DIY is that you can design for incremental upgrades. That's what I did with my mount that I built in the late 70's. I cut my teeth on Texereau's book, and was always shooting for a 10" Newtonian (or another variety of similar sized relector). I built an EQ head out of aluminum with tapered roller bearings with that in mind. I always wanted a Byers drive, but they were always just outside of budget. I've seen 9" Byers drives on ebay for $500 that are probably much better than the CGE gears (Joe Nastasi of Parallax told me they were a good deal). I've got the same gears as the CGE from WM Berg, and enough money left over to buy the GOTO. The gear in the CGE is a class 10, but Berg carries class 12 (and higher?) if you want more precision.
The mount I have doesn't have motor drives, and that's the modification that I'm currently working on. However, I do have an LXD-75, and my tapered roller bearing DIY mount is silky smooth compared to the ball bearing LXD-75. My mount balances to a much finer degree, so the torque on the motors can be much lower. I'll probably use a slower slew speed to reduce intertial loads during slewing, but I'm confident the LXD75 motors will work.
Cheers,
Michael
--------------------
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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Michael Miles
professor emeritus
Reged: 02/11/05
Posts: 621
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Hi folks:
I forgot a couple of things from harborfreight.com:
jewel dial indicator ($20):
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=1717
boring bars ($20):
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=1722
drill chuck ($20):
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=42340
digital caliper ($16):
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=47257
combo square ($18):
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=4185
center drills ($5):
http://www.littlemachineshop.com/products/product_view.php?ProductID=1230
Michael
--------------------
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
Edited by Michael Miles (05/03/06 10:33 AM)
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Michael Miles
professor emeritus
Reged: 02/11/05
Posts: 621
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Hi Bobby:
Actually, the alignment of the bearings in the bearing housing is much more critical than the shaft. The shaft is just a device to transmit the force to the bearings without flexure (ARGG No Spell check!!).
Laters,
Michael
--------------------
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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Joe Cipriano
Entropy Personified
Reged: 09/03/05
Posts: 3830
Loc: Uh... anyone have a GPS?
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Michael:
Not splitting hairs, but the W32B29-S180 isn't going to work, unless your shaft is 1/4" diameter - a little small for a 50-75lb capacity mount...
The CGE worms & wheels are not in WMBerg's regular catalog (sorry, but the ones you listed ain't it); you need to call them for a quote. IIRC, the bore for both wheels is about 1.25" (the shafts fit through the wheels).
You really need to budget for a good worm/wheel set. Also, while tapered roller bearings will tolerate some misalignment, it's not as much as you think - the shafts need to be as true as possible.
Sorry - I'm not trying to disillusion you. Please realize that it's going to take a lot of precise work to build an AP-capable mount; that's one of the reasons why the good ones are so expensive. I sincerely wish you luck. If you need any info on how the CGE is put together, I'll be happy to help you out.
--------------------
In the Land of Eternal Light Pollution & Great Pizza (Chicago)
SN-6, ED80, WO 66SD
Meade 208xt, SBIG ST-4
D70 (modified)
CGE (way modified)
A Wife who understands (unmodified)
Some other stuff...
I may not have gone where I intended to go, but I think I have ended up where I needed to be.
Douglas Adams
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Michael Miles
professor emeritus
Reged: 02/11/05
Posts: 621
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Quote:
Michael:
Not splitting hairs, but the W32B29-S180 isn't going to work, unless your shaft is 1/4" diameter - a little small for a 50-75lb capacity mount...
Bore to fit,
Michael
--------------------
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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Michael Miles
professor emeritus
Reged: 02/11/05
Posts: 621
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Hi Joe:
Quote:
...If you need any info on how the CGE is put together, I'll be happy to help you out.
Thanks for the offer - any good design surprises in the CGE that might help?
Michael
--------------------
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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Joe Cipriano
Entropy Personified
Reged: 09/03/05
Posts: 3830
Loc: Uh... anyone have a GPS?
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Quote:
Quote:
Michael:
Not splitting hairs, but the W32B29-S180 isn't going to work, unless your shaft is 1/4" diameter - a little small for a 50-75lb capacity mount...
Bore to fit...
Only if you're confident you can center the bore to about +/- 0.0005" or so, and clamp it in the chuck with sufficient force to hold it without damaging the teeth. Remember - that bore will directly affect the worm gap; if the bore is off center, your worm mesh (and backlash) will change as the worm wheel rotates - not a good thing.
You could try to engineer a spring-loaded worm block that would follow any deviations in the worm wheel while applying constant pressure - something to think about...
I'm putting together a list of the good & bad on the CGE for you; I'll post here when finished. Here's some pics of the disassembled Dec axis; RA is almost exactly the same.
--------------------
In the Land of Eternal Light Pollution & Great Pizza (Chicago)
SN-6, ED80, WO 66SD
Meade 208xt, SBIG ST-4
D70 (modified)
CGE (way modified)
A Wife who understands (unmodified)
Some other stuff...
I may not have gone where I intended to go, but I think I have ended up where I needed to be.
Douglas Adams
Edited by Joe Cipriano (05/03/06 03:22 PM)
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Michael Miles
professor emeritus
Reged: 02/11/05
Posts: 621
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Wow Joe!
Those are great pictures. Worth 1000 words. I see they do use the tapered roller bearings. Out of curiousity, what is the RA shaft diameter, and how far are the RA bearing spaced from each other?
Now I'm going to have to take pictures of my EQ head...
Thanks,
Michael
--------------------
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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Levi
sage
Reged: 12/17/05
Posts: 467
Loc: Camarillo CA
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One thing left out from all these calculations is time. What's your time worth to you? How many hours will be spent puting all this togehter? Also is the lathe 110 volt or 220 or 240 volt. Single or two phase? WIll you have to have an electrician upgrade your service for this? Add several thousand if you do.
really think it's great you want to do this and have actually thought of getting a small lathe so I can make small stuff. Problem is I'm spending so much time learning imaging and getting used to the CGE I have that I just don't have the luxury of time to devote to another hobby.
Good luck in your endeavors and please post a shot of your work when done.
--------------------
Levi
http://www.imageevent.com/cabinetry
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Michael Miles
professor emeritus
Reged: 02/11/05
Posts: 621
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Hi Joe:
By the way - I'm enjoying this thread - thanks everyone!
Another note - I spoke with Joe Nastasi about spring loading, and I seem to remember him mentioning that the Paramount ME has a sprung worm. He said that the Byers gears he used on the Parallax mounts had extremely tight concentricity on the worm gear, so a sprung worm wasn't necessary (and the PE reports I've seen on Parallax mounts prove it). The concentricity of the worm gear bore is something I'm concerned with, but if if just doesn't work, I can upgrade to the Byers drive gears and do the CGE one better.
Hoping it'll work,
Michael
--------------------
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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Michael Miles
professor emeritus
Reged: 02/11/05
Posts: 621
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Hi Levi:
The homier lathe is 110v. There's a great yahoo group for that one too:
http://groups.yahoo.com/group/7x12minilathe/
My problem is that I used to be a machinist, and when I use my LXD-75, all I can think of is how I could do it better. I used to build telescopes when I was a teenager, so I just decided that this is a part of my hobby.
When I get the mount working, I'm going to work on a spectroscope - my dream project from my adolescence...
It's all fun,
Michael
--------------------
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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Joe Cipriano
Entropy Personified
Reged: 09/03/05
Posts: 3830
Loc: Uh... anyone have a GPS?
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Quote:
Out of curiousity, what is the RA shaft diameter, and how far are the RA bearing spaced from each other?
IIRC about 7" from outside face to outside face; total shaft length is about 10". RA and Dec assemblies are exactly alike; the only real differences are the top plates, and the mortise cut into the RA housing to accept the tenon on the altitude plate. Shafts (0.984"/25mm dia) are interchangeable.
Celestron engineered the CGE fairly intelligently. In comparison to similar mounts, the Dec is "over-engineered"; Celestron probably saved some $ by limiting the number of seperate parts necessary. IMHO - smart way to save money.
--------------------
In the Land of Eternal Light Pollution & Great Pizza (Chicago)
SN-6, ED80, WO 66SD
Meade 208xt, SBIG ST-4
D70 (modified)
CGE (way modified)
A Wife who understands (unmodified)
Some other stuff...
I may not have gone where I intended to go, but I think I have ended up where I needed to be.
Douglas Adams
Edited by Joe Cipriano (05/03/06 08:29 PM)
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