Alan64

When sawing out these washers, I don't get too close to the lines.  The excess can easily be removed; better that than sawing adjacent to or even past the lines.  Such also allows for fine-tuning of the diameters.  The same follows when using shears to cut along the outside of the washers; not too close...

Note the two outer and inner lines that were described for the larger washer on the right.  That one goes in the centre of the axis, and its exact size is a bit of a mystery.  That washer will be cut and dressed along the outer lines, then to test...

The larger washer on the left must have its inner diameter ever so carefully reduced, and until it drops in place.  It must be as snug as my attempts at an ISO9001 standard will allow, and for its narrow bearing-surface.

After the washers are roughly dressed...

...I then use a Dremel tool, along with either a grinding-stone or sanding-drum, to effect the exact dimensions required.  Lastly, the washers are fine-sanded and buffed with #0000 steel-wool and lemon-oil.

The Moon, and Jupiter I believe(By Jove!), were riding somewhat high in the sky whilst I worked, sawing the washers out of the sheet.  I didn't illustrate the aftermath of the sawing of the RA washers, but here is what they looked like as well, and fresh from the scroll-saw...

I saw the centres out of the smaller washers first, then the smaller washers out along with their scraps.  That leaves all of the washers ready for cutting, dressing and polishing; no further sawing, thank goodness.  

Now, the bronze pieces appear to be beaten up, but they aren't.  That's only greasy, oily smears here and there.  Incidentally, they appear as brass within that image, smacking of it at least.

I had to douse myself with 40% DEET-based repellent, to prevent anemia.  I prefer the lemon-eucalyptus(non-DEET), but a relation within the household cannot stand to be around me whilst so "perfumed".

I broke only one blade, yet during the last stretch, perhaps an inch left, although I wasn't using those whisper-thin, pin-less, jeweller-type blades(that require an adaptor), but some old fine-toothed pin-type blades that I've had for almost twenty years.  In that I was sawing non-ferrous metal, I thought, "Why not?"

The carbide drill-bit broke just before it drilled completely through the second X, but that's because my small drill-press is not a precision product.  My mini drill-press, which I would've used instead, the belt broke recently.  I can get replacements, but not in time to complete this project.  Still, before the bit bought it, it did make a deep enough hole into the bronze for the compass-point.

The washers for the DEC-axis have been described, and pilot-holes drilled out for the scroll-saw's blade; or blades rather, as I expect one or two to break.  However, I'm learning how to prevent that, but a breakage now and then is inevitable, as this bronze is relatively thick...

It's almost dark here, and a little cooler, but not quite there.  For tonight's "festivities", I'm getting the washers described beforehand.  Here, the two Xs for the compass-point have been determined...

There, above the sheet, is one of the many micro, carbide drill-bits that I have.  I used a common, steel micro-bit for the previous washers, but it tended to describe a circle instead of drilling a hole, until I cut the shaft of the bit down.  I won't have that problem with the carbide bit; but carbide is brittle, almost to the point where a bit may be considered disposable, so care must be taken, if I want to use it again in future.

11 minutes ago, badhex said:

I was wondering something similar. Could it be the CA causes the colour to somehow get cancelled out a little? 

That does seem logical...

Then, short, "fast" achromats are primarily if not exclusively for observing the dimmer, deep-sky denizens of the night, and which are colourless, for the most part.

Indeed, here, have we stumbled upon yet another reason to own a long-focus achromat?

From this, the washers for the DEC-axis shall arise...

The section from the roll that I used for the RA-axis was somewhat prettier, and adjacent to the aforementioned...

In that Synta was most generous in sticking a 0.060"+ plastic washer at the bottom of the axis, I can go whole-hog too, and make the smaller washers for the needle-thrust bearing from the same 0.020" sheet, instead of from the 0.008" sheet as I had first considered.

Then, they'll be on the outside of the DEC-shaft.  What could go wrong?  

After all, this isn't an EQ-1.

For over a week, it's been wet, and damp persisting.  When I went outside a while ago this afternoon, I could almost see the steam rising from the ground, still.  But it is drier, and I may now set up my scroll-saw...

...but at night, and with my friends in the sky watching o'er. 

On 23/07/2021 at 08:51, Ellyll said:

Thank you that's exactly what I have done. I saw one on an auction site for  approximately what I would pay for the part if I ever found it. I understand it to be called an az1/az2 yoke mount. So when I saw the other one with the fitting I needed I thought I would make the best of 2 plus I think it comes with the other missing bit the finder scope. So hopefully in the next couple of days I can get to use my telescope. 

Thank you to you all for you help and suggestions I really appreciate it. 

Let us know how you get along.  We love happy endings.

I buffed the threads of DEC shaft with #0000 steel-wool and lemon-oil.  The needle-thrust bearing now spins even more freely, and exceeding that of government work.  Mind you, that's without grease having been applied, yet.

The DEC specs for the washers and what-not...

The upper DEC washer, at 0.020"/0.508mm in thickness...

There's another one of Synta's narrow bearing surfaces again, indicated at right, but that one may not be widened, as that of the RA-axis could've been.  The inner-diameter of the washer must be as snug as possible, as a result, and no greater than 62mm across.  Nor should the outer-diameter be greater, so as not to protrude over the teeth of the DEC-worm gear.

Incidentally, the four large plastic washers, two for the RA-axis and two for the DEC-axis, are 0.0215"/0.55mm in thickness, 0.0015"/0.038mm thicker than the bronze to replace them, although quite negligible.

The middle DEC washer is essentially identical to the bottom surface of the DEC-worm gear, also at 0.020"/0.508mm in thickness...

The thickness(0.0945"/2.4mm) indicated in the following spec(the lowermost washers) is the needle-thrust bearing sandwiched betwixt two 0.008"/0.203mm-thick bronze washers...

Said bearing and washers are taking the place of the original single plastic washer, at 0.0630"/1.6mm in thickness...

The plastic washer is 0.0315"/0.8mm thinner than the three parts to replace it, and fits over the DEC-shaft's thread rather sloppily; again, quite negligible, as those are on the outer portion of the DEC-shaft.  There will still be plenty of room for the lock-nut, and the parts for the useless setting-circle.

There may be another washer to be made, but I won't know for certain until I test-fit the thicker bronze washers.  I seriously doubt that it will be necessary, however.

I might make a bronze washer for the setting-circle as well.

The bearing spins freely now, and with that toothpick...

The aluminum threads of the DEC-shaft do tend to try to catch the inner rim of the bearing.  I will look into that as well.

In the end, the DEC-axis will have four bronze washers, two thinner and two thicker.  I would love to place even more within, more bearings too, but there are no places to put them.

The poor ole DEC-axis, always taking a back seat to the RA-axis; abandoned, forlorn, neglected, and relegated to a secondary importance.

It's a shame...

...that I cannot place the needle-thrust bearing on the inside of the DEC-axis...

...resting upon that inner surface at the very bottom...

...and lovingly sandwiched between two bronze washers to boot.  But I cannot, as it would throw everything off, wildly.  Although, it makes sense nonetheless, as the weight of a telescope would then rest upon it.  So much for dreams.  

And now, back to the original idea, which will work.  On the opposite side of that inner surface, is the outer surface.  Initially, the bearing had to be snapped in, and was somewhat difficult to pry out...

But I don't want to reduce the outer diameter of the bearing itself, so I've sanded and polished the inner surface of the cavity instead...

All of the paint on the inside was removed as a result, and now, the bearing drops in readily...

...but it does not spin as freely as I want.  Next, I'm going to grind a bit more off of the inner rim...

https://www.youtube.com/watch?v=b9xDvX2_v0k

In the end, I didn't feel the need to alter the bar.

During the interim, I had ordered a dovetail-bar from China, via AliExpress, and at 152mm in length.  It arrived today in the early afternoon...

For some unknown reason, reasonably-priced bars shorter than 200mm are few and far between, over here.  The bar came with what appears to be M4 screws...

...and useless.  They don't fit anything, for my purposes.  "Ours is not to reason why..."

I located the rings that I had gotten for the other, Celestron 70mm achromat...

But then, I noticed that the base of the rings would hang off of the ends of the bar once attached...

That's not the worst thing in the world, and most of the base does fit over the bar.  My OCD, however, wants it flush.  I haven't decided yet, but I'm probably going to drill new holes inward a bit from the ends.  The bases, the rings, are actually quite wide.  There are better-grade rings that are slimmer, which would not hang over the edge.

I then went out and got mostly M5 hardware to effect the attachment of the rings...

The nuts are of the "acorn" type, like that of an oak.  Those will act as stops on the underside of the bar, and to help prevent the telescope from sliding out of the mount's saddle whilst adjusting or removing same.

In that I will be using tube-rings, these original screws that once fastened the bar to the OTA, with their heads protruding above the tube's surface, have got to go...

I also got these, which will be placed in their steads, glued in place even...

I've adjusted the vast majority of the slop out, what very little there was, between the RA-worm and the worm-gear.  I did leave a frog-hair's width as a fail-safe.  I can't detect any real movement, only a very slight "knock".  This is being done in the summer.  In winter, it may become slightly more loose, who knows, but no matter as I don't much like observing in the cold, although the night sky is delightfully darker.

I have ordered a brass rod, 0.40"/10mm in diameter, 10"/250mm in length, and to replace these black-plastic clamping "buttons"...

The "buttons" are 0.20"/5.08mm in height, and 0.37"/9.34mm in diameter.

The threaded holes for the clamps are about 0.40"/10.2mm in diameter.  I may have to reduce the diameter of the brass rod slightly.  We'll see.

Oh dear, I've got this to do next...

<shudder>

10 hours ago, Ellyll said:

Hi all I am very new to all this. I have been given a telescope (Science Tech Reflector Telescope 262 Power)  The person I got it from said there may some bits missing It was given to them by someone else. Anyway I have tried to set it up there are only 2 items missing and I have found one of them on the internet etc.  The other one see photo below ( taken from  someone's listing on an auction site) the vital bit I am missing , I have no idea what it is called and despite searching the web all day I am still none the wiser. It is for the top of the tripod for the the big bracket thing to sit in which holds the telescope. I have joined this forum today in search of any help or advise please if possible to help me use the telescope.  If you can help I would be very grateful.

 

What you have there is a 76mm f/9 Newtonian, and with a 700mm focal-length.  I almost got one myself recently, out of rather keen interest, but then the price went up, and just before I was about to purchase it.  What you're missing there is the hub for the tripod.  It's what the legs attach to, and then the mounting-yoke for the telescope to that.  That is a most critical part, as it joins the telescope to the legs that raises it up off of the ground.  You would need to search long and hard, I'm afraid, to find that part.  I have a hub just like that among my belongings, somewhere, but I'm quite far away.  Else, I'd hand it over to you freely.

I know I haven't been of much help; my apologies.

Ah!  Here it is, and useless to me now...

It went with this refractor...

I've since removed the legs and placed them onto another hub.

5 hours ago, mikemarotta said:

Astronomy is a small market. Most of the sellers work hard at customer service because there is no second chance to do it right: people walk away and shop elsewhere. 

Allow me to recommend that you reach out to the local astronomy club. The stars at night are big and bright.

The astronomy-club closest to my home is in the middle of a large city to the north, about 30 to 40 miles away.  They actually observe in that location.  But I don't dare travel to that city these days; too dangerous, especially at night.

Then, I have my own "club" here at home.  

First things first; firstly, the two ball-bearings of the RA-worm assembly were saturated with grease; the grease massaged, pressed into the bearings in the hope that some might make its merry way inside same...

Next, the cavities for the bearings were greased, and one of the bearings pressed into place...

The worm was washed, then greased, along with the bronze washers...

The threaded adjusting-sleeve was screwed in until it just stopped, by hand, no tool, then the nut was tightened over that...

The RA-worm assembly installed...

Whilst twisting the worm-shaft with the thumb and forefinger, the motion is utterly smooth and effortless, as though it's not attached to the axis at all, yet the worm-gear rotates at the same time, just as smoothly and effortlessly.

In that the bronze washers cannot be seen after assembling, there's no image of those to show, only of which to tell.

I will need to tweak the RA-worm assembly, with the set-screw in the centre of the block.  When taking hold of the worm-gear assembly, I can move same side to side only ever so slightly, left to right, right to left.  I want to see if I can get that just a wee bit tighter, without compromise.

The DEC-worm assembly, the cavities for the ball-bearings, are tighter.  It did not arrive as freely turning as the RA-worm assembly, but it's now just as the other.

The time has come to grease the worm-assemblies...

"Get on with it already!"

Okay, okay!

The four worm-washers, two for the RA-axis, and two for the DEC-axis, are completed.  Glamour shot...

The washers do not span the full diameter of the ball-bearings, only a bit beyond the inner portion which rotates independently...

More bronze "jewellry" for the mount-head...

The RA-worm assembly, exploded...

Not much else there, than what may be seen when assembled.

The ball-bearing assemblies fit quite well within the worm-block...

...good thing, that; although, nasty little hole there in the casting.

Hmm...

We can't have the two, steel ball-bearing assemblies rubbing against the brass worm, can we?

What might be done about that?

Two 10d galvanised-nails into oak, and spaced 11mm apart...

The nails cut down to where 15mm lengths were left...

Then...

I just want to see if I can "fix" it.

The RA-worm assembly...

The nut required a 17mm socket...

...but I'm going to have to make a tool to loosen the adjuster.

You want something like this, rather...

That long adaptor looks like what's provided with the Sky-Watcher Newtonian-Dobsons, and another animal entirely.

That diagonal is an Amici, and for daytime/terrestrial use; birds in trees, ships at sea, that sort of thing.  At night, a star-diagonal is suggested, and in this case a star-mirror.

You can get a 2" star-mirror, or this 1.25"... https://www.rothervalleyoptics.co.uk/antares-90-star-diagonal-125.html

20 hours ago, casual_observer said:

Thank you Alan for the input!

Velcro would also come in handy crafting a "dew-sheild" out of household materials

Indeed it would.  The ready-mades utilise Velcro for fastening, too, and may simulated at home very easily.  I made this one with materials from hardware and arts & crafts stores...