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Meade DS-90 Rehab Project

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#1 GoldSpider

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Posted 14 February 2018 - 09:31 AM

Last night I adopted a neglected and abused Meade DS-90.  For the price I was only concerned with the condition of the tube and optics, intending to replace everything else.  Modest expectations were met.  Barely.

 

IMG 4625

 

Other than the OTA itself, this is a truly pitiful scope.  The focuser is almost entirely plastic, and broken at all three flange screws (evidence, I surmised, of several escape attempts by the tube). 

 

IMG 4632

 

1/4 of the plastic rack teeth were broken off, and the finder had apparently ejected some parts as well, leaving an empty, useless 25mm tube.

 

IMG 4627

 

The mount and tripod appear to be intact, though I'm hesitant to trust the plastic parts and hollow aluminum legs to support the substantial-in-comparison OTA.  At some point I'll test it, if only to resell and recoup a few bucks on the renovation.

 

IMG 4630
 
For the rehabilitation, first and foremost the focuser will be replaced with a GSO 2" Crayford (still deciding if the two-speed is worth the expense on this scope), and then a finder scope with appropriate bracket and shoe.  Scopestuff appears to have a Synta shoe that attaches to the GSO focuser, so that makes the most sense to me, though a Meade finder would have been a nice touch.
 
Fortunately, I already have a set of Celestron tube rings that inexplicably came with my CG-5 mount that happen to fit the OTA perfectly, and a 2-inch diagonal that came with my 80mm imager that is seldom used.  
 
This should give me a nice, relatively inexpensive addition to my stable of scopes, and perhaps restore a little lost dignity to a serviceable set of optics.  

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#2 Auburn80

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Posted 14 February 2018 - 12:44 PM

Sounds like fun! waytogo.gif

 

Keep us posted on your progress; especially the focuser replacement.



#3 GoldSpider

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Posted 24 February 2018 - 10:00 AM

Small update:  I decided that the focuser update is not worth it the expense.  It looks like the objective was cleaned by the original owner, and not well.  They managed to damage the coating on the front, and left small scratches on the back. 

 

As luck had it, I found an exact match replacement for the damaged focuser cheap.  Bought that, ordered a metal draw tube to replace the stock plastic one, and am putting a 1.25" back and diagonal on it. 

 

Picked up a Meade 6x30 straight-through finder to replace the broken 5x24.  I'm gambling that the Synta shoe I'm ordering from Scopestuff will mate the bracket securely with the screw hole placement on the focuser.

 

bracket focuser

 

Last decision will be on a suitable mount.  Sure wish I'd pounced on the Vixen Super Polaris that was on Classifieds when I started this; that would have been a perfect platform for this scope!



#4 GoldSpider

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Posted 27 February 2018 - 03:42 PM

Here's a shot of the defects in the objective lens.  It's not noticeable looking at it straight on, so I'm not sure how much this will affect its performance.  It almost looks like the edge might be sealed, and I'm speculating that the defect may be a result of moisture that got between the lenses.  Is this a possibility worth looking into to the extent of separating the lenses to inspect?  How would I go about re-assembling the lens and properly sealing it?  The last thing I want to do is make things worse.

 

Objective Lens

 



#5 Myk Rian

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Posted 19 March 2018 - 06:46 PM

I just came into possession of a Meade DS-90. Just like yours. The only thing I find I am missing are the 2 upper halves of the cradle rings.

I looked around the Meade website and have not found any as replacement parts. Do you have a tip where I can find them.

 

Too bad about your objective lens. It looks pretty well scratched up. Makes you wonder what the PO was thinking while cleaning it.


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#6 GoldSpider

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Posted 19 March 2018 - 10:06 PM

I just came into possession of a Meade DS-90. Just like yours. The only thing I find I am missing are the 2 upper halves of the cradle rings.

I looked around the Meade website and have not found any as replacement parts. Do you have a tip where I can find them.

 

Too bad about your objective lens. It looks pretty well scratched up. Makes you wonder what the PO was thinking while cleaning it.

Most likely I'll be parting out everything besides the OTA out, so once I'm done with this I can let you know and we can work something out.  Shipping for these two bits of plastic couldn't be that much.

 

Considering the shape of the focuser assembly, I don't imagine there was a whole lot of "thought" that went into it at all.  Using an unknowingly abrasive glass cleaner is probably the least negligent thing that happened to this scope.


Edited by GoldSpider, 19 March 2018 - 10:08 PM.

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#7 Ringo

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Posted 24 March 2018 - 02:49 PM

Small update:  
As luck had it, I found an exact match replacement for the damaged focuser cheap.  Bought that, ordered a metal draw tube to replace the stock plastic one, and am putting a 1.25" back and diagonal on it.


Hey brother, I've got a 2102 like new coming to me in a few days and I was going to get either a Synta metal focuser for it or splurge for a dual speed Crayford from ScopeStuff. I had a 2090 and a 2102 before that I put Synta focusers on and they worked great compared to the original plastic crap.

My question is: Would the simple mod of the metal draw tube replacement make a huge difference in the slop or just a little better. Telescope-Warehouse has them right now for 20 bones. Trying to decide whether to get one for 20 bones or splurge since this is a like-new 2102, which are nice grab n'go refractors and are not easy to find.

#8 Myk Rian

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Posted 26 March 2018 - 09:04 AM

I'll have a new draw tube Wed and will let you know if it helps.

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#9 GoldSpider

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Posted 26 March 2018 - 02:45 PM

Hey brother, I've got a 2102 like new coming to me in a few days and I was going to get either a Synta metal focuser for it or splurge for a dual speed Crayford from ScopeStuff. I had a 2090 and a 2102 before that I put Synta focusers on and they worked great compared to the original plastic crap.

My question is: Would the simple mod of the metal draw tube replacement make a huge difference in the slop or just a little better. Telescope-Warehouse has them right now for 20 bones. Trying to decide whether to get one for 20 bones or splurge since this is a like-new 2102, which are nice grab n'go refractors and are not easy to find.

 

I actually ordered that focuser from ScopeStuff, and it was a perfect fit for the tube, but I would have had to tap new holes in the OTA for the screws to secure it.  I wasn't comfortable with that, nor (ultimately) with spending that much for a focuser on what might be a marginal scope, and ended up returning it.  The metal draw tube is definitely an improvement over the plastic one, though the R&P focuser still isn't what I'd call "smooth".  Still a work-in-progress.


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#10 Myk Rian

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Posted 26 March 2018 - 06:34 PM

My DT arrived a day early, (thanks, Bill ). I had to file down the blob of epoxy used as a rack stop to keep it from rubbing the focuser inner ring. No biggie there. It has tightened the focuser up quite a bit. $20 well spent.

Edited by Myk Rian, 27 March 2018 - 08:25 AM.

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#11 GoldSpider

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Posted 26 March 2018 - 07:22 PM

My DT arrived a day early, (thanks, Kevin). I had to file down the blob of epoxy used as a rack stop to keep it from rubbing the focuser inner ring. No biggie there. It has tightened the focuser up quite a bit. $20 well spent.

That could be part of my problem with the sticky focuser.  Thanks for pointing that out.


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#12 Ringo

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Posted 26 March 2018 - 10:51 PM

Ok, so you ready for this? A few months ago the "boss lady" here goes "you need to lose some of your scopes, you got way too many all over the place". I'm like I know I got like 14 or 15 of various shapes and sizes plus parts galore including 1 of these Meade 90's and a much desired Meade 102mm (DS2102) both with these nice Synta metal focusers I put in them. I'm like "I got my C6 and C8, what do I need these for?" So I contact Bill at Telescope-Warehouse (he's 2 hours from me) so maybe I don't have to spend a ton of time (and money) listing everything on eBay and here. The brother takes everything! I meet him in Kingman, AZ and he looks at everything and gives me a check for 800 bones. Three months later I'm throwing up all over myself for letting go the 2102. WTH was I even thinking? I even tried to buy them back from him but he sold it all! Freak me, lol. The Synta focusers cost me about 60 bones 5 years ago but now you can't hardly find them anywhere. Here's pics of the 2102:DS102 02a.JPG DS102 03a.JPG DS102 04a.JPG

Edited by Cyberpunk, 26 March 2018 - 10:55 PM.


#13 Myk Rian

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Posted 30 March 2018 - 02:35 PM

I was looking at the so called teflon tape in the focuser. It looks like black electrical tape, so I removed it, used Goof Off to clean the residue, and then cleaned it with alcohol. Years ago my BIL gave me a partial roll of teflon tape used for door walls and windows. I cut that into 1" strips and put it in place of the OEM tape. Much smoother and it tightened it up nicely.

Here's the old tape with a strip of the new.

 

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#14 GoldSpider

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Posted 30 March 2018 - 03:05 PM

I was looking at the so called teflon tape in the focuser. It looks like black electrical tape, so I removed it, used Goof Off to clean the residue, and then cleaned it with alcohol. Years ago my BIL gave me a partial roll of teflon tape used for door walls and windows. I cut that into 1" strips and put it in place of the OEM tape. Much smoother and it tightened it up nicely.

Here's the old tape with a strip of the new.

Could you take a photo of where that tape goes inside the focuser?  I could be mistaken, but I don’t believe I have anything between the draw tube and the inside of the focuser. 

 

Edit:  I checked the old broken focuser I replaced and found where those tape strips are.


Edited by GoldSpider, 30 March 2018 - 06:09 PM.


#15 Myk Rian

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Posted 17 April 2018 - 09:59 AM

I checked the collimation last night. Set a compass to 1.75" and drew a circle 3.5" diameter. I cut that out and placed it over the objective lens.

Wrapped a couple layers of paper around my collimated laser and placed it in the focuser. The beam landed about 1" off center, so I loosened the focuser mounting screws and adjusted it until the laser hit the center spot from the compass point. Tightened the focuser screws, and done.


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#16 Myk Rian

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Posted 20 April 2018 - 08:48 AM

Here is what I have. I've put a lot of work into this thing, as you have also.

 

 

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  • 20180331_120734.jpg

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#17 Myk Rian

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Posted 20 April 2018 - 08:49 AM

Another;

 

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#18 Myk Rian

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Posted 20 April 2018 - 10:40 AM

The Alt/Az gearing is what took the most time. I took both gear boxes apart, cleaned everything, and replaced or flattened the washers and worm gears. There are 4 spring washers. one on each end of the gear/clutch assembly. So assembly is; Spring washer - indexed washer, with flattened side facing out - worm gear - indexed washer, with flattened side facing in - Spring washer - hand knob.

 

I used gun lube on the worm gears and axle shaft. A drop or 2 of oil between the gears and clutch washers.

 

20180321_105627.jpg

 

20180321_103144.jpg

 

 

 



#19 Myk Rian

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Posted 20 April 2018 - 10:56 AM

If your motors turn a bit before moving the scope, Your gear boxes need adjusting.

 

There are a couple adjustments that need to be made when tuning the setup of the gearboxes. The first it to remove slack in the axle shaft.

The lock nut on the end of the shaft needs to be adjusted so when it turns, and moves the flat worm gear, it doesn't move in or out. Tighten the nut just enough to prevent that. It should still turn freely.

 

There is also an adjustment for the worm gears meshing. A small hex wrench (don't remember the size) is used to adjust the position of the axel shaft. It brings the worm gears further or nearer together. Adjust it to minimize slop. Everything must still turn freely. The Alt/Az gearboxes are identical.

I think loose gearing would be a frustrating experience for Meade Telestar users, and a source of a bad rep.

 

20180321_105618.jpg

 

20180321_110758.jpg


Edited by Myk Rian, 20 April 2018 - 12:17 PM.

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#20 GoldSpider

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Posted 23 April 2018 - 08:10 AM

Here is what I have. I've put a lot of work into this thing, as you have also.

Did yours come with that handsome white dew shield?  I like that better than the cheap, cap-less one that came on mine.

 

How did you end up attaching the RDF?



#21 Myk Rian

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Posted 23 April 2018 - 09:02 AM

I have the white dew shield, but no lens cover. Used double sided tape to attach the RDF.

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#22 jonalmada

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Posted 06 March 2019 - 01:39 AM

I just picked up one of these for $25 and it certainly has it's issues. For one the guy who had it didn't really store it in too good of conditions and it has had a rough life, but less rough than the one Goldspider brought back to life.

I've got one rather sticky issue with my DS-90 restore. The AltAz worm gear literally is broken in two with a clean break on the clean part of the shaft away from the worm gear itself. The brass portion, if you can call it that, is likely some kind of pot metal and has some kind of wood looking material on the inside. I'm debating drilling a pin on either side to reassemble the pieces or putting out a call for anyone with a donor replacement to help me resurrect this poor little beastie to life. I will say that this thread is a Godsend since I got some wonderful insights from the photos and all of you guys commenting.

 

DSC 0140
 
DSC 0135

 

 

The other thing that is a royal pain are the cheap battery holders for the 10 AA batteries. The plastic on the one I have is self-destructing. I went ahead and ordered a replacement off Ebay, but I want that to be a temp solution and to put an appropriate large capacity battery on the unit to power it. My question is can I get away with 12 VDC or is this thing requiring 15 VDC?


Edited by jonalmada, 06 March 2019 - 01:48 AM.


#23 Myk Rian

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Posted 06 March 2019 - 08:06 AM

I use a 12v, 2 amp supply.
Try scopehed for a gear.
My focuser just wasn't going to cut it. I replaced it with a GSO 2 speed Crayford from Scopestuff.

Myk
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#24 jonalmada

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Posted 06 March 2019 - 02:06 PM

I use a 12v, 2 amp supply.
Try scopehed for a gear.
My focuser just wasn't going to cut it. I replaced it with a GSO 2 speed Crayford from Scopestuff.

Myk

Thanks Myk - I'll document my progress on getting it to work and share the photos on this thread. I'll give scopehed a try ;>)



#25 GoldSpider

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Posted 06 March 2019 - 02:52 PM

If you don't have any luck getting what you need from scopehd, I can see if I can dig out one of the motors I salvaged from the mount/tripod before I tossed it.

 

While I'm here, here's a little update on this project.  I replaced the focuser assembly with an identical one I found on eBay, and replaced the focuser drawtube with a metal one from scopehd. 

 

I bought a synta finder shoe, finder stalk, and a basic 6x30 Meade finder (also from scopehd).  As I'd anticipated, the shoe doesn't fit particularly snugly, as the only points that actually contact the focuser are at the screws.  Not a particularly firm base for it (would love some ideas here to improve this).  The finder is a piece of junk (even for the price); it's out of focus and there is no way to adjust it.  Basically useless.

 

I took the scope outside, and not surprisingly there was a good deal of chromatic aberration.  I wasn't expecting terrific optics, but even I was a bit disappointed at the view of Mars.  I've considered replacing the objective with a lens cell from Surplus Shed, but I think that would probably be throwing good money after bad, so I will probably just try to sell the OTA.  I've ended up collecting several more telescopes than I need.




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