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Old Meade Starfinder EQ too shaky...

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#1 Chopin

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Posted 17 January 2014 - 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

#2 herrointment

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Posted 17 January 2014 - 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!!!!!

#3 obin robinson

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Posted 17 January 2014 - 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 :question:

#4 schluterdude

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Posted 17 January 2014 - 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

#5 Gil V

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Posted 17 January 2014 - 11:23 PM

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

#6 cheapersleeper

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Posted 18 January 2014 - 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

#7 tybee

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Posted 18 January 2014 - 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.

#8 Wmacky

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Posted 18 January 2014 - 09:46 AM

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

#9 obin robinson

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Posted 18 January 2014 - 10:55 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


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 :cool:

#10 Chopin

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Posted 18 January 2014 - 11:18 AM

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.

#11 Chopin

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Posted 18 January 2014 - 11:27 AM

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 :question:


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.

#12 Chopin

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Posted 18 January 2014 - 11:29 AM

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.

#13 Chopin

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Posted 18 January 2014 - 11:31 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.


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

#14 thywyn

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Posted 18 January 2014 - 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...

#15 Chopin

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Posted 18 January 2014 - 11:39 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


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 :cool:


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...

#16 Chopin

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Posted 18 January 2014 - 11:40 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...


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

#17 obin robinson

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Posted 18 January 2014 - 12:43 PM

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 :)

#18 herrointment

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Posted 18 January 2014 - 01:19 PM

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

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

Attached Files



#19 rdandrea

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Posted 18 January 2014 - 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.

#20 Chopin

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Posted 18 January 2014 - 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
Posted Image


Industrial casters
Posted Image


Vibration suppression pads
Posted Image


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

Posted Image


Am I missing something here?
Posted Image


Is this spacing close enough
Posted Image


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...
Posted Image

#21 herrointment

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Posted 18 January 2014 - 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!

#22 Chopin

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Posted 18 January 2014 - 03:16 PM

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

#23 schluterdude

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Posted 18 January 2014 - 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.

#24 Chopin

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Posted 19 January 2014 - 06:55 AM

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.

#25 hottr6

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Posted 19 January 2014 - 09:36 AM


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?

Posted Image

Before the restoration:

Attached Files








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