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Equipment Discussions >> Mounts

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Chopin
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Old Meade Starfinder EQ too shaky...
      #6318755 - 01/17/14 02:08 PM

Hey all, this isn't a forum that I frequent, but need some advice. I picked up a yard sale "find of the century" several years back. It was a Meade 10" Starfinder EQ package complete with plössl and instruction book for $50. Yes, the whole thing was in complete working order, except for some fungal etching on the mirrors. I've since rebuilt the scope with lighter weight protostar tube, lighter weight custom mirror cell, and had the primary recoated, etc... The scope is fantastic. But even after shedding several pounds on the OTA the vibrations still drive me batty. I'm really just looking for visual use from a tracking accuracy POV, but I think my expectations regarding stability are more in line with an astro photographer since most of time is spent north of 100x for L&P sketching.

Okay, to the point, is it possible to rebuild the Starfinder to make it worthy of carrying the big 25lb OTA, or should I start saving my money for a complete upgrade, say something like a used Celestron CI-700? Or is there an even better option...?

Thanks


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herrointment
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Re: Old Meade Starfinder EQ too shaky... new [Re: Chopin]
      #6318816 - 01/17/14 02:36 PM

I've got a 8" f/8.5 on a Starfinder. If I wanted good performance out of the mount I'd go for a short focal length 8" or better yet a 6" f/8.

Putzing around with the mount has delivered very small gains in my experience. I'd save for something more up to the task.

Here's your mount......... LINK!!!!!


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obin robinson
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Re: Old Meade Starfinder EQ too shaky... new [Re: Chopin]
      #6319210 - 01/17/14 06:15 PM

Shaky? What kind of surface is it on and are there any vibration pads under the feet? I just finished converting mine to be used as an astrophotography mount. Please provide more insight as to how and where the mount is shaking.

obin


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schluterdude
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Re: Old Meade Starfinder EQ too shaky... new [Re: obin robinson]
      #6319372 - 01/17/14 08:10 PM

My StarFinder 8" was a rock on the "port-a-pier" EQ it had. Double check everything is tight, including the declination axis. Snug that up by loosening the "setting circle" (quoted because it is kind of a rinks dink set up...), have someone push down on the saddle, and retighten it. That alone does wonders for the mount!

Also, if it is missing the rubber shoes, hunt down a suitable replacement.

Or, sell it to me :-P


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Gil V
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Reged: 09/09/12

Re: Old Meade Starfinder EQ too shaky... new [Re: schluterdude]
      #6319646 - 01/17/14 11:23 PM

My 10" starfinder has never had an issue with vibration. It dampens very quickly.

Edited by Gil V (01/17/14 11:24 PM)


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cheapersleeper
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Re: Old Meade Starfinder EQ too shaky... new [Re: Gil V]
      #6319697 - 01/18/14 12:10 AM

When I could get it balanced, I was able to do webcam on Jupiter for 60 seconds at a time. The thing was hard to manage but when tracking right it was not particularly shaky.

B


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tybee
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Re: Old Meade Starfinder EQ too shaky... new [Re: Chopin]
      #6320061 - 01/18/14 09:33 AM

Many years ago I started out with a Meade DS-10 which is basically the same scope as the Starfinder. I ended up putting my mount on top of a 4” water pipe screwed into a fire hydrant flange. The whole thing was bolted to a 15' x 20' concrete pad at least 24” thick in the center with 8 12” long 1/2” bolts. It was rock steady. My damping times were close to instantaneous. I regularly observed luna and Jupiter at 450x + and this was with the original 45lb sonotube.

I would say you need to upgrade your pier.

Tracking on the other hand wasn't so hot. You can't make a silk purse out of a sows ear.


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Wmacky
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Re: Old Meade Starfinder EQ too shaky... new [Re: tybee]
      #6320081 - 01/18/14 09:46 AM

Yeah, mine damped quickly, but I think that was because the bearings were made of rubber, and solidified peanut butter!

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obin robinson
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Re: Old Meade Starfinder EQ too shaky... new [Re: cheapersleeper]
      #6320195 - 01/18/14 10:55 AM

Quote:

When I could get it balanced, I was able to do webcam on Jupiter for 60 seconds at a time. The thing was hard to manage but when tracking right it was not particularly shaky.

B




In the other thread I think you saw my stepper motor upgrade for the Starfinder mount. Last night the mount was so stable that my biggest problem was with the heat coming off of the mirror. Jupiter was rock solid in the eyepiece with no vibrations. The stepper motor is much better than the AC synchronous in that regard.

The only time I noticed vibrations were when I knocked into the telescope or the feet by accident. They still dampened quickly.

obin


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Chopin
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Re: Old Meade Starfinder EQ too shaky... new [Re: herrointment]
      #6320257 - 01/18/14 11:18 AM

Quote:

I've got a 8" f/8.5 on a Starfinder. If I wanted good performance out of the mount I'd go for a short focal length 8" or better yet a 6" f/8.

Putzing around with the mount has delivered very small gains in my experience. I'd save for something more up to the task.

Here's your mount......... LINK!!!!!




Funny, I've been toying with the idea of a 7-8" newt, possibly a Royce conical 8". Would definitely be a lot lighter. But I think the GEM is my issue, since the dampening times are more than I'd like even when my 110mm newt is riding on top.

That Byers unit is cool. I've seen it before., but thought it was a custom build. I didn't realize there where others like it.


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Chopin
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Re: Old Meade Starfinder EQ too shaky... new [Re: obin robinson]
      #6320276 - 01/18/14 11:27 AM

Quote:

Shaky? What kind of surface is it on and are there any vibration pads under the feet? I just finished converting mine to be used as an astrophotography mount. Please provide more insight as to how and where the mount is shaking.

obin




Obin, thanks for the response. I'll post some pics with more detailed explanations, but the gist is this:

• Home built dolly with large locking casters
• Vibration pads (standard Meade style)
• Stock portable pier
• "Home built/modified" dove plate in place of original steel straps

I'm sure that my dolly design could be improved, as well as a complete overhaul of my poorly designed dovetail plate.

I can't remember if I mentioned it in the first post, but I use a binoviewer or a 2-ish pound EP with a 50mm extension tube. I am aware that this taxes the mount a little extra.


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Chopin
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Re: Old Meade Starfinder EQ too shaky... new [Re: schluterdude]
      #6320283 - 01/18/14 11:29 AM

Quote:

My StarFinder 8" was a rock on the "port-a-pier" EQ it had. Double check everything is tight, including the declination axis. Snug that up by loosening the "setting circle" (quoted because it is kind of a rinks dink set up...), have someone push down on the saddle, and retighten it. That alone does wonders for the mount!

Also, if it is missing the rubber shoes, hunt down a suitable replacement.

Or, sell it to me :-P




Good tip, T, thanks. I'll look at my "joints" and see if I could do any tightening.


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Chopin
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Re: Old Meade Starfinder EQ too shaky... new [Re: tybee]
      #6320288 - 01/18/14 11:31 AM

Quote:

Many years ago I started out with a Meade DS-10 which is basically the same scope as the Starfinder. I ended up putting my mount on top of a 4” water pipe screwed into a fire hydrant flange. The whole thing was bolted to a 15' x 20' concrete pad at least 24” thick in the center with 8 12” long 1/2” bolts. It was rock steady. My damping times were close to instantaneous. I regularly observed luna and Jupiter at 450x + and this was with the original 45lb sonotube.

I would say you need to upgrade your pier.

Tracking on the other hand wasn't so hot. You can't make a silk purse out of a sows ear.




Tybee, thanks. I've considered doing a custom pier build, and wondered if that might not be a big part of the issue.


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thywyn
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Re: Old Meade Starfinder EQ too shaky... new [Re: Chopin]
      #6320301 - 01/18/14 11:38 AM

at one point I had issues with my starfinder eq.. It ended up to be the ra worm had to much play between it and the main gear.. +1 for checking everything is snug...

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Chopin
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Re: Old Meade Starfinder EQ too shaky... new [Re: obin robinson]
      #6320302 - 01/18/14 11:39 AM

Quote:

Quote:

When I could get it balanced, I was able to do webcam on Jupiter for 60 seconds at a time. The thing was hard to manage but when tracking right it was not particularly shaky.

B




In the other thread I think you saw my stepper motor upgrade for the Starfinder mount. Last night the mount was so stable that my biggest problem was with the heat coming off of the mirror. Jupiter was rock solid in the eyepiece with no vibrations. The stepper motor is much better than the AC synchronous in that regard.

The only time I noticed vibrations were when I knocked into the telescope or the feet by accident. They still dampened quickly.

obin




Yeah, another thing. The term vibration is a little vague. I should define the shakes as more of a low frequency wobble, as opposed to a high frequency buzz. It's not buzzy, just wobbly. If it was buzzy and settled in less than a 1/2 second I'd be ecstatic.

FWIW, I'm impressed by how well it tracks as long as I've taken the time to do a rough alignment of Polaris. I can use an EP with a 1/2 degree TFOV, leave the scope for more than 30 minutes and come back to the object still in the view...not still centered, mind you, but definitely in the view.

Off to take some images...


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Chopin
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Re: Old Meade Starfinder EQ too shaky... new [Re: thywyn]
      #6320305 - 01/18/14 11:40 AM

Quote:

at one point I had issues with my starfinder eq.. It ended up to be the ra worm had to much play between it and the main gear.. +1 for checking everything is snug...




Thanks. I'll do this while I set up the scope in a few minutes.


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obin robinson
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Re: Old Meade Starfinder EQ too shaky... new [Re: Chopin]
      #6320434 - 01/18/14 12:43 PM

Quote:

Obin, thanks for the response. I'll post some pics with more detailed explanations, but the gist is this:

• Home built dolly with large locking casters
• Vibration pads (standard Meade style)
• Stock portable pier
• "Home built/modified" dove plate in place of original steel straps

I'm sure that my dolly design could be improved, as well as a complete overhaul of my poorly designed dovetail plate.

I can't remember if I mentioned it in the first post, but I use a binoviewer or a 2-ish pound EP with a 50mm extension tube. I am aware that this taxes the mount a little extra.




My advice is to do as we say in aviation and "nut and bolt" everything. Go over EVERY fastener and make sure it is torqued tightly. The only issue I have with the Starfinder mount is that there is a lot of slop in the worm gear. The mount itself is very solid but the worm gear has a bit of periodic error which makes long exposure astrophotography very difficult. Planetary is fine but DSLR is going to be an uphill battle with these gears.

If you want I will take pictures of my stepper motor setup. It made things A LOT better than the AC sync motor and allows for easier slewing as well.

obin


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herrointment
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Re: Old Meade Starfinder EQ too shaky... new [Re: obin robinson]
      #6320510 - 01/18/14 01:19 PM Attachment (10 downloads)

My issue is that the mount can't handle the long moment arm of a 70+" tube.

I did find a replacement.........


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rdandrea
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Re: Old Meade Starfinder EQ too shaky... new [Re: Chopin]
      #6320562 - 01/18/14 01:39 PM

Check the worm gear backlash. It's set by moving the whole worm block. There should be a couple of allen-head capscrews that you can loosen to move the worm block. There is also a preload adjustment for the worm. It is a screw that presses on the worm. You can see it from the end opposite the motor.

Edited by rdandrea (01/18/14 02:08 PM)


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Chopin
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Re: Old Meade Starfinder EQ too shaky... new [Re: rdandrea]
      #6320653 - 01/18/14 02:31 PM

Okay, so I've definitely narrowed down to two huge culprits, and they're both my own dumb fault. The first is that the casters, despite being locked when in use, still have a lot of play. After pulling the whole unit off of the dolly much of the low frequency vibration reduced. The second issue is my homemade dovetail saddle, which I already suspected as a partial issue. It seems to allow some loose vibrations at that particular part of the joint. I do think that perhaps the moment arm of the BV on the 45" tube might still be a tad much for the mount, as it seems there is some slight flexure at the top of the pier. However, at this point, I'll have to :

1) Redesign the dolly to at least include leveling feet to bring the casters off of the ground

2) Just buy a dovetail saddle that actually hold the OTA without flexing

3) Tightening everything down as has been suggested by several of you


Once I have done these three things I'll reevaluate.



At any rate, here are some images:

The rig



Industrial casters



Vibration suppression pads



My weak saddle, which is the aluminum top chopped from a Celestron 70-AZ tripod





Am I missing something here?



Is this spacing close enough



And here's a big one...how do I upgrade this!?! It really doesn't hold the tube from moving on the Dec (I think) Axis...


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herrointment
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Re: Old Meade Starfinder EQ too shaky... new [Re: Chopin]
      #6320712 - 01/18/14 03:11 PM

The space holds the optional dec tangent arm.

The lock knob is easier to use with a rubber cover on it but it is what it is...not great.

The small gap is normal IIRC.

Can't imagine the saddle is helping things!


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Chopin
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Re: Old Meade Starfinder EQ too shaky... new [Re: herrointment]
      #6320722 - 01/18/14 03:16 PM

I agree. The saddle needs to go. Thanks for the input on the other points, Jim.

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schluterdude
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Reged: 08/05/13

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Re: Old Meade Starfinder EQ too shaky... new [Re: Chopin]
      #6320869 - 01/18/14 04:47 PM

Keep the nylon bolt. Anything else (except brass) will mar the shaft, causing shifting when clamping. Not good!!!!

As for the RA axis gap, it can be taken apart, but it's tough! There are plastic bushings inside you can grease while you are in there. It's fairly self explanatory once you start stripping it down. You may need a small amount of mass persuasion (small dead blow hammer) to bang the shaft out.


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Chopin
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Re: Old Meade Starfinder EQ too shaky... new [Re: schluterdude]
      #6321721 - 01/19/14 06:55 AM

Quote:

Keep the nylon bolt. Anything else (except brass) will mar the shaft, causing shifting when clamping. Not good!!!!

As for the RA axis gap, it can be taken apart, but it's tough! There are plastic bushings inside you can grease while you are in there. It's fairly self explanatory once you start stripping it down. You may need a small amount of mass persuasion (small dead blow hammer) to bang the shaft out.




Thanks, T. Once I finish the other changes I'll assess this area to see if it seems related to any residual shakes. I'm beginning to get the impression that it wouldn't be worth the effort to "fix" anyway.


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hottr6
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Re: Old Meade Starfinder EQ too shaky... new [Re: Chopin]
      #6321837 - 01/19/14 09:36 AM Attachment (4 downloads)

Quote:



That Byers unit is cool. I've seen it before., but thought it was a custom build. I didn't realize there where others like it.



You mean like this 10" Starfinder and Byers 812?



Before the restoration:


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hottr6
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Re: Old Meade Starfinder EQ too shaky... new [Re: Chopin]
      #6321862 - 01/19/14 09:49 AM

Comments on your photos:
1) The Vixen dovetail is too small for this rig. Either go back to the lightweight Starfinder straps or a wider dovetail.
2) The "gap" in the DEC axis is for the optional tangent arm (bright shiny thing in following image)



3) The "gap" under the RA setting circle appears about right
4) I kept the stock DEC clutch screw and it works fine.


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hottr6
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Re: Old Meade Starfinder EQ too shaky... new [Re: schluterdude]
      #6321867 - 01/19/14 09:54 AM

Quote:

Keep the nylon bolt. Anything else (except brass) will mar the shaft, causing shifting when clamping. Not good!!!!

As for the RA axis gap, it can be taken apart, but it's tough! There are plastic bushings inside you can grease while you are in there. It's fairly self explanatory once you start stripping it down. You may need a small amount of mass persuasion (small dead blow hammer) to bang the shaft out.



Pulling the DEC axis should require NO persuasion. It is held in place by a small grub screw on the saddle. Relieve the grub screw and the nylon clutch screw and the DEC axis will fall out (watch your toes). If not, you may have a bent or abused shaft.


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schluterdude
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Re: Old Meade Starfinder EQ too shaky... new [Re: hottr6]
      #6322265 - 01/19/14 02:00 PM

I agree with a well loved one! The plastic bushings are fairly snug. I was able to obtain one with virtually zero hour on it (but still 20 years old! Lol) and whatever grease was used at the factory had "stickified" over the years.

I'm not saying to bang the snot out of it. Yes, something is VERY wrong if that is the case. A small rap with a 3lb dead blow just helps get the process started if his was like mine. Clean up the old grease, clean the shaft with WD40 and a grey scotch brite pad, and slide her back together!


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Chopin
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Re: Old Meade Starfinder EQ too shaky... new [Re: schluterdude]
      #6326427 - 01/21/14 03:28 PM

Okay, I've replaced the huge industrial casters with some small furniture grade casters. Now I can raise the casters off the ground with blocks and have a perfectly solid meeting point right from the base. Another positive side effect is that the whole pier is now 5 inches lower, improving the center of gravity. Much better.

Second thing, I pulled off the weak saddle. Until I can justify the cost of a full saddle and plate (maybe ADM), I'm just bolting the tube rings right to the top plate of the mount. It works, even though it's not as elegantly adjustable. Definitely solid, though. Another improvement.

So now it seems apparent that the most obvious amount of remaining jiggle is emanating from the RA axis. It's not a lot, but it's definitely there. so the next step is to pull off the cover and see if the worm gear needs adjusting. I'm not sure exactly what "backlash" is. But if it's a degree of wobble between the teeth and the worm then I can see how that might be an issue.

I'll get back once I strip and assess it.

Edited by Chopin (01/21/14 03:33 PM)


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rdandrea
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Re: Old Meade Starfinder EQ too shaky... new [Re: Chopin]
      #6328319 - 01/22/14 12:52 PM

Quote:

I'm not sure exactly what "backlash" is. But if it's a degree of wobble between the teeth and the worm then I can see how that might be an issue.




That's what it is.


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Dr. Woo
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Re: Old Meade Starfinder EQ too shaky... new [Re: rdandrea]
      #6331553 - 01/23/14 10:00 PM

Yeah my Starfinder GEM has slop in the (backlash) in the worm and gear too. Haven't tried to adjust it out yet, but there is a screw to adjust that.

And to obin robinson I'd love to see pictures and info on your stepper conversion being as the motor is missing on my GEM


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obin robinson
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Re: Old Meade Starfinder EQ too shaky... new [Re: Dr. Woo]
      #6332029 - 01/24/14 07:16 AM

Quote:

Yeah my Starfinder GEM has slop in the (backlash) in the worm and gear too. Haven't tried to adjust it out yet, but there is a screw to adjust that.

And to obin robinson I'd love to see pictures and info on your stepper conversion being as the motor is missing on my GEM




Send me your e-mail address and I can send a bunch of photos to you in high res.

obin


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schluterdude
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Re: Old Meade Starfinder EQ too shaky... new [Re: obin robinson]
      #6332193 - 01/24/14 09:33 AM

Every gear requires a small amount of backlash. With the gear being plastic, I'll bet that there's a ton of runout/out of round to it as well. This is why you "cheat" and intentionally leave the RA axis slightly out of balance, so you are always in a loaded condition.

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Chopin
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Re: Old Meade Starfinder EQ too shaky... new [Re: schluterdude]
      #6336178 - 01/26/14 08:32 AM

So, I pulled the plastic housing from the gears at the back of the RA shaft. There might be a little backlash there, but it seems okay.


Quote:

Every gear requires a small amount of backlash. With the gear being plastic, I'll bet that there's a ton of runout/out of round to it as well. This is why you "cheat" and intentionally leave the RA axis slightly out of balance, so you are always in a loaded condition.




I can acknowledge that when I don't put slightly more weight on the "dropping" side of the RA it can take roughly 5-10 seconds for the image to start tracking again after I reposition the RA by hand. Perhaps someone here knows if this is within normal tolerances for the Starfinder. Mine seems like it's 14 years old, given the instruction booklet has a copyright date of 2000.

At any rate, I've viewed with the scope twice now since removing the sloppy saddle and the jiggly casters, and I'm disappointed by how much worse the vibration is at the RA. Settling times are noticeably faster, but the vibrations are higher in frequency. I understand basic mechanical principles enough to get why this is happening. And after inspecting the whole RA "arm" (not sure what the correct name is) I can verify that it is indeed the weak link.

I tested my theory by closely watching the gear and electronics housing while moving the scope end manually and forcefully back and forth on the RA axis. It clearly flexes in opposing directions, ever so slightly, in response to the scope on the other end. I wonder if the real culprit is that the joint that holds the RA "arm" in place is just too weak to handle the loaded 28.6 pound OTA and 25 pounds of weights on the lower shaft. If this is the case, is there a way to strengthen the RA axis?


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schluterdude
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Reged: 08/05/13

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Re: Old Meade Starfinder EQ too shaky... new [Re: Chopin]
      #6336768 - 01/26/14 02:05 PM

Do the vibrations match the frequency of the motor vibrating and/the small gearbox? Is there a resonance building up causing the tube to vibrate like a tuning fork?

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herrointment
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Re: Old Meade Starfinder EQ too shaky... new [Re: Chopin]
      #6336781 - 01/26/14 02:14 PM

The clutch does have some lag in it so you need to lead the object you wish to observe a bit. You can try adjusting balance and clutch tension......it's a can of worms though. Here's a LINK for replacement bushings if that's any help.

Some folks are really liking this mount.....so the answer is out there somewhere. Good luck!


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schluterdude
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Reged: 08/05/13

Loc: Centerville, OH
Re: Old Meade Starfinder EQ too shaky... new [Re: herrointment]
      #6336868 - 01/26/14 02:59 PM

When setting balance, disengage that slipper clutch! I forgot to mention that earlier! I think there are three screws on the tension plate. You can always completely remove it, clean it up, and re grease it as well. Then use a marker, and mark the tube for both visual and AP setups. That way you can just set it and go each time.

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Chopin
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Reged: 02/03/05

Loc: In the doghouse.
Re: Old Meade Starfinder EQ too shaky... new [Re: schluterdude]
      #6337438 - 01/26/14 07:30 PM

Quote:

Do the vibrations match the frequency of the motor vibrating and/the small gearbox? Is there a resonance building up causing the tube to vibrate like a tuning fork?




No, I believe they're much slower frequency vibrations than the motor, and they only come on when I touch the tube or when a moderate breeze hits it like a sail. It does eventually settle (less than two seconds, perhaps). The worst part is that it sets off vibrations every time I touch the focuser knob. It is making it extremely frustrating to dial in the correct focus since it vibrated every time. Maybe I'm expecting too much out of the mount. I'd like rock solid performance, and I beginning to think I'm not going to get that with a 45 inch, 28 pound OTA. I'm still willing to work with it, though, because I'm not in a position to drop $1500-2000 on a new mount.


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Chopin
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Reged: 02/03/05

Loc: In the doghouse.
Re: Old Meade Starfinder EQ too shaky... new [Re: herrointment]
      #6337443 - 01/26/14 07:33 PM

Quote:

The clutch does have some lag in it so you need to lead the object you wish to observe a bit. You can try adjusting balance and clutch tension......it's a can of worms though. Here's a LINK for replacement bushings if that's any help.

Some folks are really liking this mount.....so the answer is out there somewhere. Good luck!




Thanks. I really like the mount, it works wonders with my 4" Newt. Tracking is really good for visual use, and it runs on AA batteries. Hard to complain about that for the $50 it cost me.

I'll check the link and see about the clutch.


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Chopin
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Reged: 02/03/05

Loc: In the doghouse.
Re: Old Meade Starfinder EQ too shaky... new [Re: schluterdude]
      #6337446 - 01/26/14 07:33 PM

Quote:

When setting balance, disengage that slipper clutch! I forgot to mention that earlier! I think there are three screws on the tension plate. You can always completely remove it, clean it up, and re grease it as well. Then use a marker, and mark the tube for both visual and AP setups. That way you can just set it and go each time.





Good tips. Thanks, T.


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schluterdude
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Reged: 08/05/13

Loc: Centerville, OH
Re: Old Meade Starfinder EQ too shaky... new [Re: Chopin]
      #6337493 - 01/26/14 08:05 PM

Perhaps try a motorized focuser?

Or, try and reinforce the area around the focuser. I have a thin steel plate on both the OD and ID of the tube that shores up that area, helped me out allot!


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