The ongoing SLT saga! (Warning photos)

[GordonCopestake]

You might be aware that Rob and myself own SLT telescopes from Celestron. They are excellent lightweight grab and goto scopes that can carry about 8lbs of telescope (although mine is nearly 10lbs hence a few problems!). The telescope as it comes is serviceable with the lightweight plastic OTA's they are supplied with. They are intended for beginners and they do an excellent job at introducing people to astronomy. However they have a growing following with more experienced astronomers for grab and go scopes and to be used for mounting small APO's and maks on them.

However, like all good things, they have a few problems with stability that im trying to overcome. The mount arm is cast aluminum and i've also discovered that the "cup" and tripod leg lugs are also cast aluminum which makes the whole assembly actually quite stable. The part that lets things down are the tripod leg connectors and the spreader hardware. Both of which are plastic and mean that the whole ediface can twist and resonate to quite some degree. Untuned the whole thing can resonate for about 12 seconds when fully loaded. This obviously is unusable and makes focusing impossible.

I setout early this morning to see what i could do about this. First off a picture of the unsulled SLT base. This is what it SHOULD look like and something i should aspire to when i've put everything back in place!

Removing the top plastic cover reveals the 2 battery blocks, these are used to power the scope when an external powersource isn't used. It's an addition over the old GT mounts and a nice touch. I wish they had spent the extra money on the tripod though!

The 2 battery blocks are loose and are easily removed (or infact just fall out). Being careful not to pull the power connector i had a good nosey around inside. Spotting 4 screws that hold this second cover in place i swiftly removed this and delved deeper ..... only to find:

Nothing! Theres [removed word] all in these little mounts! All the "brains" and motors appear to be in the arm. Which is odd as that probably makes the thing top heavy. Well no matter. On a plus point, everything you see here is cast aluminum. The webbing gives extra strength and such a simple design appeals to me. Theres a single bolt in the center of the mount which holds to two parts of the rotating base together. This bolt seemed an ideal canditate to tightening so i used my trusty socket driver to tighten it a little. I didn't want to tighten it too much as it might strain the motors when slewing.

There was little else to be done here so i undid the large tripod screw that holds the mount head to the tripod and removed the mount head. It was at this point that i realised that the "cup" that celestron have used is actually quite solid. It's cast aluminum and you can see a "clock face" of ridges cast in to the metal.

Looking at the mount base i could see the 3 protrusions that interface with this clock face providing a very strong and high surface area connection. The mount base is also cast aluminum. You can also see the small plate that has the 1/4"-20 tapped hole in that accepts the phototripod bolt in the tripod head. This plate is easily removed using the 2 screws.

At this point the idea that i'de had regarding the use of a CG5 tripod came back to me. Although i think using the existing "cup" is probably a good idea with it being cast metal and not the plastic i initially though it was. Creating a new plate with a slightly larger tapped hole would allow the larger bolts of the CG5 to be used however i dont think this would give an advantage at this point as all this bolt does is ensure the two halfs of the mount are in close contact. The real work is done by the tripod legs.

Now the legs themselves arn't bad. They are tubular steel about 1" in diameter and fairly solid. The let down is the connections between the cast aluminum lugs on the base and the tops of the legs...... PLASTIC! It was here that the problem stemed and here where the battle would be faught!

Now the plastic tops of the legs are riveted to the steel legs which makes removing them a pain. And even if i could removed them without damaging the steel leg (perhaps by drilling them out) i would then be left with steel legs and no way to connect them to the mount. Any DIY botch job i did to connect them would probably be less secure than the original legs. Cleverer people than me work at celestron and made this connection (albeit to a price point) to be as strong as possible. I doubt i could do better with the materials at hand.

I decided there and then that Russ and others were right and the best way forward was to simply replace the entire tripod leg with a something else. Perhaps from an EQ5. I have an old EQ1 but the aluminum legs on that are probably worse than the SLT originals! My other option is to use hardwood and that appeals to me. I used to own a Vixen GP mount that had an ash tripod and was rock solid. Something like that would be perfect AND look nice

So i measured the lugs on the base and it's my intention to source a secondhand tripod or possibly find a cheap brand new alternative.

Well it's been an interesting morning and it beats work! This thread is really for me rather than anyone else as it helps me to crystalise my ideas, plus the photo trail assists my ailing brain (my memory isn't what it once was....)

Comments are welcomed as are offers of spare tripods! Hopefully i'll be able to update this thread with my solution soon. I'm off to make a few phonecalls to suppliers!

[geppetto]

Cool 8)

If it was mine, I'd go with wood.

Even if the legs were made from 2*1 pine, it would be

100 times more stable than what you have now.

Nice hardwood would be nicer still

Interesting little saga Gordon

[GordonCopestake]

I had contemplated DIY wooden legs, but my woodworking skills are pretty much none-existant!

[Kaptain Klevtsov]

The gap at the top in the wooden leg looks like 1.25", so if you find some 1.25" x 1" timber you just fasten three strips side by side with glue and nails, the middle one is offset to leave the 1.25" gap at the top and form a leg at the bottom, drill a hole for a bolt and that's it.

Adjustable would be fiddly but not much more work.

Captain Chaos

[geppetto]

The gap at the top in the wooden leg looks like 1.25", so if you find some 1.25" x 1" timber you just fasten three strips side by side with glue and nails, the middle one is offset to leave the 1.25" gap at the top and form a leg at the bottom, drill a hole for a bolt and that's it.

Spot on 8)

Just how I made mine...

quick n' dirty n' cheap n' stable

Edit: I used glue and screws on mine but then I'm not from Uddersfield

[Kaptain Klevtsov]

Edit: I used glue and screws on mine but then I'm not from Uddersfield

Well my welding is rubbish with wood, don't have the right welding rods.

(But I do have a nail gun :D )

Captain Chaos

[GordonCopestake]

Sounds like a plan, i might have a bash at that! Even i cant get that wrong......... :shock:

[geppetto]

Even i cant get that wrong

Pictures please! :D

[GordonCopestake]

As you wish!

My first hours work:

Any ideas for a spreader bar? I was thinking of using string to hold the legs up, but that doesn't give any strength.

[geppetto]

You took yer time :D

Nice job matey

A leg spreader could be three bits of chain from legs to a matal ring in the middle.

[russ]

wow Gordon that should look the business.

look forward to seeing the end result.

Russ

[GordonCopestake]

hehe, i had nothing better to do today

seemed like a good project.

I used 1.25" x 1.25" pine, not ideal but it will tell me if it works or not. I used m6 nuts/wingnuts throughout as this means i didn't have to redrill the lugs. Had to use threaded rod though as couldn't find any bolts long enough (3.75"). Just cut off what i needed, worked a charm. Used 8mm repair washers too to spread the load and keep it nice and tight.

Just need to put the bottom block in place now on each leg. I might make that the foot, im not sure. Then to sort out the spreader. I think i'l lbolt the blocks through rather than nail them as i can keep pressure on them then. Nails might pull loose, even with glue.

No idea if it will work, it could be worse than the original hehe, we'll see!

[Kaptain Klevtsov]

Gordon, seeing as you have the screwed rods, I'd put the spreader low down. Start by putting a stack of four pieces through one leg and drill through the two side pieces and the top piece, then on the next leg use three pieces, then two. That way they will overlap in the centre properly and you can put a bolt through the lot, still have 1.25" ground clearance as well.

If it doesn't make sense I'll try again.

Captain Chaos

[geppetto]

CC thats inspired 8)

[Kaptain Klevtsov]

Thanks Geppetto

Oh and Gordon, if you're there, maybe put the top blocks a little further down so that the wingnuts can compress the legs onto the casting without trying too hard to bend the leg pieces.

Captain Chaos

[GordonCopestake]

I missed your tip CC, but i can move the top blocks down easily enough. I see your point about the bolts compressing the legs.

I tested the tripod as is and it DOES add strength to the whole thing. But there is STILL some flexure. I dont think im going to be able to take that last little bit out and im going to have to live with the 1-2 seconds wobble at high powers. At low powers its fine, and tbh wide field is what i brought the ED80 for in the first place. The SLT mount is rated at 8lb's and my ED80 with 2" diagonal, 8x50 right angle finder, hunk of televue glass is already up to 10lbs. So i guess im already at the outer edge for this mount. I looked up the weight of the smaller moonfish scopes and was supprised that they are actually HEAVIER on paper than the ED80's. Makes no sense to me as the ED80 is in a 100mm tube. Hey ho. I doubt my D70 will sit nicely on this hehehe

[GordonCopestake]

Photos:

Not ideal and im still missing a spreader bar, but it's better than the original!

[Rob]

Nice job Gordon!. You could use plywood and cut a triangle, square off each corner and L bracket to the legs?.

Rob

[GordonCopestake]

That would work Rob and give some stability but you wouldn't be able to close the tripod then without a screwdriver

[Rob]

Wing nuts to attach?. Put the bolts through the legs, and fix the wing nuts on from the inside of the leg?.

Failing that, old fashioned chain!!... pull out till the chain tightens

Rob

[geppetto]

Looking proper is that Gordon

Another block between the sides of each leg half way down

wouldn't go amiss.

Also, when you've got the spreader on, dangle a decent weight

from the top centre. Six pack of beer should be right but allow

for the weight decreasing through the observing session

[GordonCopestake]

Would an extra block half way down add much to the stability Phil? I was thinking cutting the legs short and having another piece sliding inside with a wingnut to clamp the sliding part down. Gives me an extending tripod. Not sure how much stability i'de loose tough. I like the weight idea..... i'll let the missus know

Rob, chain or string is ideal. 3 pieces attached to a central metal ring or something. I'de also tie a piece of elastic to the ring and attach the other end to the base of the mount so the chain didn't get in the way when the legs closed.

I need to screw everything down tight and glue it all together so it's permanent at the moment it's not stuck. Any surgestions for wood glue? Are they all the same? Im attaching to flat pieces together not dowels or anything so it would have to be strong and not squish out too far.

I'm quite pleased with how it's turned out actually.

[Rob]

Screw it together Gordon, don't cut corners now... job done!.

[GordonCopestake]

I'll have to go and buy some 3" screws as i dont have any long enough. And i'll have to buy a long drill bit too cause i think i'll need to pilot the holes. Then all thats left is varnish, varnish and varnish

[OXO]

Gordons Grab n Do it ya self scope