Lightbridge not holding collimation

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AZSkies
Post subject: Lightbridge not holding collimation
Posted: Wed Aug 05, 2009 10:14 am
molecule
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I have been having problems after cool down and collimation with the scope holding collimation when I move it to zenith. How I know this is when viewing from the back I move the scope up towards zenith and watch the shadow on the blug move from center. It moves very little but enough that it effects the view. I have replaced the holding screws on the OTA and I replaced the springs with "better" ones from ACE Hardware. What could be causing the slippage? I also have locking washers on the inside of the mirror holder where the springs are.

Jeff

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Meade 12" Lightbridge Deluxe
Meade 24mm SWA eyepiece
Explore Scientific 14mm & 6.7mm 82 deg eyepiece
Meade 2X Telenegative amplifier
Thousand Oaks UHC Filter
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The Blug!
Tectron Chesire and Sight tube collamation eyepieces
AstroZap Light Shield
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Bobs Knobs primary and secondary collamation screws

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snorkler
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Posted: Wed Aug 05, 2009 12:28 pm
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Have you checked the spider vane mounting screws and secondary mirror adjustment screws?

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AZSkies
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Posted: Wed Aug 05, 2009 1:11 pm
molecule
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Yes, the spider vane screws are tight and the secondary screws are as well. I can hear a slight thump when I move it to zenith like the mirror cell shifted or the mirror shifted. It improved a little when I added the locking washers behind the mirror cell where the collimation screws go through but the problem is still there.

Jeff

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Meade 12" Lightbridge Deluxe
Meade 24mm SWA eyepiece
Explore Scientific 14mm & 6.7mm 82 deg eyepiece
Meade 2X Telenegative amplifier
Thousand Oaks UHC Filter
Howie Glatter 1 1/4 635nm laser collimator
The Blug!
Tectron Chesire and Sight tube collamation eyepieces
AstroZap Light Shield
A cool looking eye patch!
Bobs Knobs primary and secondary collamation screws

Music is like candy, you have to throw away the rappers!


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Square_peg
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Posted: Wed Aug 05, 2009 3:55 pm
The Blacksmith
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Sounds like your primary is moving around. You hate to tighten the mounting clips too tight or you'll end up with pinched optics.

However if the mirror diameter doesn't match the diameter the mirror clips are spaced for then you could have an issue. Try wiggling the mirror in its cell. If it moves back and forth easily then you might need to add some felt pads to the insides of the mirror clips to take out the slop.

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AZSkies
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Posted: Wed Aug 05, 2009 7:47 pm
molecule
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I will try the felt pads on the mirror clips, but they have been tightend and tested and loosend and tested with the same result. I have lots of time for now to experiment so I will try different things.

Jeff

_________________

Meade 12" Lightbridge Deluxe
Meade 24mm SWA eyepiece
Explore Scientific 14mm & 6.7mm 82 deg eyepiece
Meade 2X Telenegative amplifier
Thousand Oaks UHC Filter
Howie Glatter 1 1/4 635nm laser collimator
The Blug!
Tectron Chesire and Sight tube collamation eyepieces
AstroZap Light Shield
A cool looking eye patch!
Bobs Knobs primary and secondary collamation screws

Music is like candy, you have to throw away the rappers!


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Erik
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Posted: Wed Aug 05, 2009 9:46 pm
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A thump is definitely a telltale sign that the primary is moving. Cork or rubber works pretty well as a gasket/shim. You can attach it in 3 points on the mirror cell (not the mirror) and that should solve your problem. :)

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Chopin
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Posted: Thu Aug 06, 2009 4:06 am
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Ditto what these guys said. My Hardin does the same. I just haven't gotten around to making the fix yet. You could also get a University Optics primary cell. From all I've hear those are really nice, solid cells for a reasonable cost.

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Erik
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Posted: Thu Aug 06, 2009 11:17 am
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I have an older UO mirror cell on my 16" dob, and it's great. But it is a bit oversize, with an ID of about 16.25". It comes with nylon screws that can be tightened so they hold the mirror in place from the sides (the cell also has traditional mirror clips), but I chose to use a gasket instead. I didn't like the idea of the screws, nylon or not, resting against the mirror. With the shims I used, the cell does an excellent job of holding my big, thin mirror. The newer 27 point UO cells are probably even better. Since they mount from the side, it may be necessary to use an extension tube to reach focus, as they can't be installed as far back as the original cell. :)

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-Erik Wilcox
Homebuilt 16" Truss Dob
8" Antares f/5 Newt
SV 80mm ED Nighthawk NG on M1 ALT/AZ
Nikon Prostaff 65mm spotter on Trekpod
Konusvue 20x80 binos/Peterson PipeMount


"Newt Gingrich is what stupid people think smart people sound like."
-The Great Paul Krugman

Evolution is both fact and theory. Creationism is neither. -Anonymous


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AZSkies
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Posted: Thu Aug 06, 2009 12:53 pm
molecule
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I went on UO's web site and all I saw were eyepieces. I looked for accessories and no luck, am I not in the right web site?

Jeff

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Meade 12" Lightbridge Deluxe
Meade 24mm SWA eyepiece
Explore Scientific 14mm & 6.7mm 82 deg eyepiece
Meade 2X Telenegative amplifier
Thousand Oaks UHC Filter
Howie Glatter 1 1/4 635nm laser collimator
The Blug!
Tectron Chesire and Sight tube collamation eyepieces
AstroZap Light Shield
A cool looking eye patch!
Bobs Knobs primary and secondary collamation screws

Music is like candy, you have to throw away the rappers!


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Chopin
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Posted: Fri Aug 07, 2009 5:05 am
Velocepedist
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Nope, you're in the right place. It looks like they must have very recently pulled their ATM stuff off the site. Too bad. I'm not sure where else you can get aluminum cells like that for a good price.

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Erik
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Posted: Fri Aug 07, 2009 1:41 pm
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Wow, if that's the case, that's really too bad. Merdian Telescopes has quite a few ATM parts, but I'm not sure whether they have mirror cells. I would try and call University Optics just to see if they can still get them.

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-Erik Wilcox
Homebuilt 16" Truss Dob
8" Antares f/5 Newt
SV 80mm ED Nighthawk NG on M1 ALT/AZ
Nikon Prostaff 65mm spotter on Trekpod
Konusvue 20x80 binos/Peterson PipeMount


"Newt Gingrich is what stupid people think smart people sound like."
-The Great Paul Krugman

Evolution is both fact and theory. Creationism is neither. -Anonymous


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AZSkies
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Posted: Fri Aug 28, 2009 8:09 am
molecule
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If anyone of you would be so kind to give me step by step directions as how to fix the primary I would greatly appreciate it!! Also, is it possible to paint the outside of a Lightbridge. Can you rough up the surface and spray paint it? The white is pretty yes but I feel the reflected light hurts contrast. If I'm wrong, tell me. But remember, I have a cane now! :mrgreen:

Jeff

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Meade 12" Lightbridge Deluxe
Meade 24mm SWA eyepiece
Explore Scientific 14mm & 6.7mm 82 deg eyepiece
Meade 2X Telenegative amplifier
Thousand Oaks UHC Filter
Howie Glatter 1 1/4 635nm laser collimator
The Blug!
Tectron Chesire and Sight tube collamation eyepieces
AstroZap Light Shield
A cool looking eye patch!
Bobs Knobs primary and secondary collamation screws

Music is like candy, you have to throw away the rappers!


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Chopin
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Posted: Fri Aug 28, 2009 12:38 pm
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As long as there is no white visible to the inside of the light path, the outside of the housings should have little consequence. The trusses would be best off as flat black though, IMO, since they do lie mostly within the visibly reflected area of the light path. The very top and bottom of the upper cage and top of the mirror housing tube could likely be touched up with flat black as well. Also, a shroud will help, if you don't already have one. As for the consequence of the color of the outer portion of the scope (the part which does not effect the light path), that color will have a direct relationship with the speed of radiant cooling. White reflects all light, and thus allows for the passage of heat out through the tube more quickly as a result. If the outside is painted black it could slow down the cooling process, although I'm not sure by what percentage.

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Square_peg
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Posted: Fri Aug 28, 2009 1:07 pm
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Talk to Sky Captain (Kerry Hanna) over on Cloudy Nights about modding the Light Bridge. He's done about everything a man can do to improve it, including some powder coating. He's got one sweet LB. :cool:

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AZSkies
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Posted: Sat Aug 29, 2009 2:15 pm
molecule
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I have seen Sky Captans LB and he did an amazing job modding it out. As for my scope, I have a flat black tape on the inside of the trusses and of course I have a shroud. All inside white parts are painted flat black with a testors paint pen including the mirror cell. I also flocked the upper assembly. I just thought the with the scope being a bright white it would have some effect on seeing. I was thinking of a medium gray color. But the WAF comes into play here also.

Jeff

_________________

Meade 12" Lightbridge Deluxe
Meade 24mm SWA eyepiece
Explore Scientific 14mm & 6.7mm 82 deg eyepiece
Meade 2X Telenegative amplifier
Thousand Oaks UHC Filter
Howie Glatter 1 1/4 635nm laser collimator
The Blug!
Tectron Chesire and Sight tube collamation eyepieces
AstroZap Light Shield
A cool looking eye patch!
Bobs Knobs primary and secondary collamation screws

Music is like candy, you have to throw away the rappers!


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AZSkies
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Posted: Sun Apr 11, 2010 10:10 am
molecule
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Ok, I need to get this correct before I go spend more money on mods. My Lightbridge is still "shifting" when I move it to zenith. So am I correct in saying (and what you folks are saying) that I need to wrap felt around the outside of the main mirror?

Also on a different subject, is there a way to "rework" the base? I thought on saw on CN a mod to a Lightbridge base where it looked more like an Obsession base. Is this possible? And if not, because my altitude break is worn out what about the counterweights that Far Point Research sell (three 3lb weights that screw into the bottom of the mirror cell) or the sliding two 1lb weights that attach onto the OTA tube. Just need some input if you don't mind. Also, can you use the teflon pads that sell in hardware stores to use for alt movement, the ones that already have the nails in them.

Jeff

_________________

Meade 12" Lightbridge Deluxe
Meade 24mm SWA eyepiece
Explore Scientific 14mm & 6.7mm 82 deg eyepiece
Meade 2X Telenegative amplifier
Thousand Oaks UHC Filter
Howie Glatter 1 1/4 635nm laser collimator
The Blug!
Tectron Chesire and Sight tube collamation eyepieces
AstroZap Light Shield
A cool looking eye patch!
Bobs Knobs primary and secondary collamation screws

Music is like candy, you have to throw away the rappers!


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Erik
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Posted: Sun Apr 11, 2010 5:25 pm
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The base would definitely be my top priority. I would just rebuild one out of plywood, using your current base as a template. Then you can cut holes in the plywood base and it will be stronger and lighter than the particleboard base.

The shift does indeed sound like the mirror has a gap between it and the cell. Sone felt or soft Velcro should fix the problem.

_________________

-Erik Wilcox
Homebuilt 16" Truss Dob
8" Antares f/5 Newt
SV 80mm ED Nighthawk NG on M1 ALT/AZ
Nikon Prostaff 65mm spotter on Trekpod
Konusvue 20x80 binos/Peterson PipeMount


"Newt Gingrich is what stupid people think smart people sound like."
-The Great Paul Krugman

Evolution is both fact and theory. Creationism is neither. -Anonymous


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AZSkies
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Posted: Sun Apr 11, 2010 8:48 pm
molecule
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So not to sound old and confused :mrgreen: but do I make the base the same as what I have, just out of plywood? Will I be able to safely make it smaller and not as large and heavy. Remember, I'm old and forgetful and need details!

Jeff

_________________

Meade 12" Lightbridge Deluxe
Meade 24mm SWA eyepiece
Explore Scientific 14mm & 6.7mm 82 deg eyepiece
Meade 2X Telenegative amplifier
Thousand Oaks UHC Filter
Howie Glatter 1 1/4 635nm laser collimator
The Blug!
Tectron Chesire and Sight tube collamation eyepieces
AstroZap Light Shield
A cool looking eye patch!
Bobs Knobs primary and secondary collamation screws

Music is like candy, you have to throw away the rappers!


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