Meade "Polaris" 90mm f/10 Achromat

[Alan64]

I recently acquired this 90mm f/10 achromat, a Meade, and a second-hand clearance item...

https://www.ebay.com/itm/Meade-Polaris-90mm-Refracting-Telescope-Tube-1-25-Focuser-Red-Dot-Viewfinder/232757124851?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

...or £49.06.   A very good buy, in any event...

These were, and are still, returns apparently.  My own came with a sheared-off thumbscrew for the finder...

I was able to remove the lower part by grinding a slot, once I was barely able to unscrew it to raise it above the surface...

Some time afterwards, and as I was putting away the packaging, this fell out onto the floor...

...the better half.  Strange, though, as the shipping box was utterly undamaged; not even a scratch.  The seller eventually sent me a replacement...

Incidentally, I can't use that 8x50 finderscope with this telescope, as its eyepiece is simply too close to the business end there at the back.  It came with a good red-dot finder, and bang-on upon its arrival.  That's also strange.

Would that all of these imported telescopes arrived to one's liking and satisfaction.  Unfortunately, they don't. 

The doublet-objective upon its arrival, and untouched...

Lovely, but those lens-spacers are history.

[Stu]

Looks like a nice bargain, should have some fun with that.

I would think that if you rotate the diagonal 90 degrees clockwise then you should be able to use the finder?

What do you mean by the spacers being history? What will you replace them with?

Enjoy.

[SIDO]

That's a nice scope for a bargin, makes a good solar scope too with the appropriate filter. Nice work extracting the set screw by the way, I see your set up alt az so if that's the intent rotating the diagonal will work to get more headroom for the magnified finder but it will set you a little skewed or not looking straight down into the eyepiece with that setup...a set of rings and dovetail would solve it...good scope though, should put up some nice views ?

[Alan64]

1 hour ago, Stu said:

Looks like a nice bargain, should have some fun with that.

I would think that if you rotate the diagonal 90 degrees clockwise then you should be able to use the finder?

What do you mean by the spacers being history? What will you replace them with?

Enjoy.

I've already finished the telescope, and I'm now working on another.  This thread is being created after the fact.  I'll be revealing what happened to those haphazardly-placed, paper spacers further along.

That finderscope simply got in the way, and regardless of the diagonal's placement.  I have a large head.  Straight-through viewing is certainly possible, given the drawtube's length, and that would enable usage of the finderscope.  In any event, the red-dot is quite good.

[Alan64]

45 minutes ago, SIDO said:

That's a nice scope for a bargin, makes a good solar scope too with the appropriate filter. Nice work extracting the set screw by the way, I see your set up alt az so if that's the intent rotating the diagonal will work to get more headroom for the magnified finder but it will set you a little skewed or not looking straight down into the eyepiece with that setup...a set of rings and dovetail would solve it...good scope though, should put up some nice views ?

I might make a white-light solar filter for it.  Hmm, a set of rings and a dovetail-bar?  That was an interesting development in and of itself as I had gone along.

[Alan64]

The focusser, and all of metal, save the knobs...

But slop was clearly evident, even with the drawtube fully racked inward.  I wonder if this had anything to do with it...

Not a bit of PTFE(Teflon) among them...

Those two white bearing-strips for the drawtube; look how similar they appear to this piece from a packaged pastry's paper tray-liner...

That smacks of...Synta!  But of course!  That won't do, not at all.

The rather lengthy drawtube, and with a very skinny rack...

I also thought that the chromed rack was of plastic, but it's of brass, after I gouged it...

No stone was left unturned in the renovation of this telescope.  I took a piece of flocking, removed the adhesive off the backside, scored the paper underneath, then epoxied a tiny square of it onto the forward-facing tip of the rack...

Can't have that tip glinting off from the moonlight, or any light for that matter.  Dead as a door-nail, to all manner of stray light, my telescopes are inside, throughout.

The factory grey-black paint has the usual orangey, rusty cast, but no longer within the drawtube...

Even the two baffles within are of metal.

[SIDO]

Meade still isent painting the tube ends going into the cell it looks like in your photo, and I've also seen cell retainers and bottoms unpainted on these scopes.  No different than in 1990 in that regard ? 

[Alan64]

I use this to blacken my telescopes; it works a treat...

But you don't just spray it.  It has to applied by hand as well...

Flocking and blackening, flocking and blackening, flocking and blackening...

That's what it's all about, and in getting that last little bit of contrast out of the telescope.

This is what I had left of my old(2009) roll of flocking...

It was once a 30"-wide by 75"-long roll.  So, I recently ordered another roll...

You can never have too much flocking.  

[Alan64]

30 minutes ago, SIDO said:

Meade still isent painting the tube ends going into the cell it looks like in your photo, and I've also seen cell retainers and bottoms unpainted on these scopes.  No different than in 1990 in that regard ? 

All of the imported telescopes, regardless of design, are works in progress.  It's left to the end-users to finish them up.

Incidentally, in the early '90s, I had the misfortune of receiving a brand-new Meade 390 alt-azimuth kit.  The doublet was fouled with dirt, and cracked even if I remember correctly.  I sent it back pronto and got something else.

However, this 90mm Meade is its antithesis, although the old Meade 90mm did sport a metal objective-cell.

[SIDO]

Here's my 1990 390 Az, old pic quite a few upgrades since then. Only thing still original are the tube, cell and shield, has had a ton of work done over the years. Can't lift it anymore due to disability.

[Alan64]

That older version, the 390 and 395, can make use of a Herschel wedge, for solar.  With the plastic objective-cell of my own, that's not an option, I'm afraid.  I'll have to make do with the lesser white-light solution, the film.

[Alan64]

The interior of the focusser's housing, before and after...

The adjustable(via set-screws), black-plastic bearing-strip for the drawtube became the substrate for a .030"-thick self-adhesive strip of PTFE.  The two bases for the fixed strips received two layers of aluminum-foil tape, a layer of clear double-sided tape, and a .020"-thick strip of PTFE, each...

Before, there was considerable slop as the drawtube was racked inward and outward, even when racked fully inward; but no more, even when racked fully outward...

The camera had a hard time taking a crisp image of that utterly dead interior, instead focussing on the knobs outside.

The distance from the outer surface of the drawtube to the inner rim of the housing's flange is 18mm to 18.5mm, all round; although I've yet to check the overall collimation.

Working with this metal focusser was an absolute pleasure, compared to the plastic ones in the past.  As I went along, everything seemed to magically fall into place, and work perfectly.

[Alan64]

What's next, I wonder.  Ah, the optical-tube, of course...

Three baffles this achromat sports.  There will be no flocking past the first baffle from the objective end, but that's probably all it needs anyway, given the length of the tube and where ordinary blackening will suffice.

Here, the first run from the objective end has been flocked, and the remainder re-blackened...

That was taken with the flash of the camera.  Here, without the flash...

At the time that image was taken, there were eleven light-bulbs on in the room; to stray light, deader than a proverbial door-nail.

The fixed dovetail-bar was removed, and the threaded holes of the tube filled...

The aperture of this achromat is 90mm, but the diameter of the tube is 80mm.  Within its cell, the doublet is stepped off away from the end of the tube, enough I suppose to render the 90mm aperture intact, or at least most of it...  

[Alan64]

Once the fixed dovetail-bar was removed, how to mount it?

Again, the diameter of the Meade's optical-tube is 80mm.  I had gotten an Antares 805 80mm f/6 achromat from Canada about three years ago...

...and its tube is 80mm in diameter as well...

...a perfect fit.  The two telescopes can share the same tube-rings.  Now, I couldn't balance the Antares with a 2" diagonal and a 2 eyepiece with its rather short dovetail-bar.  Around 2003, I had acquired this 13"-long bar, and for a failed mounting project for yet another telescope(I have 12 or 14 at present)...

It's rather dated, but never used, until now...

...most versatile for both telescopes, and for every conceivable balancing requirement.  Here it is on the Antares, and balanced with the 2" diagonal and eyepiece...

It will be shown fitted onto the Meade 90mm f/10 towards the end of the thread.

[Alan64]

The plastic objective-cell, and the retaining-ring for the doublet; my, they certainly are shiny...

The ring and a portion of the cell were blackened, after the surfaces were roughened...

That's the only portion of the cell that required blackening.  The dew-shield...

One piece it is, and with its faux flange.  I hate shiny black plastic, even when it isn't in the light-path.  It looks cheap.  So, I painted it a matte-nickel, and overcoated that with a clear-satin...

The rim of the objective-cell was painted, too...

The dew-shield friction-fits over the cell, but it wasn't tight enough to my liking, so I added three strips of flocking, in a triad, round about the inner surface of the dew-shield's flange, and it's now nice and snug.

[Alan64]

The dew-shield was also flocked...

With the entry-level telescopes, the dust-cap for the objective SNAPS into place, along with its reduced-aperture cap, at 65mm.  I don't care for that.  So, I cut off all the ridges and bumps from round both caps, and used the dew-shield's flocking to hold the main cap in place, and red felt to hold the 65mm aperture-cap in its place...

Both caps now fit like a glove, hold in place, and with no snapping pressure or sounds.  For the main cap to fit into the flocked dew-shield, I had to reduce its diameter somewhat, and test-fitting it after each short grinding session; mustn't take too much off...

Certain areas of the main cap were blackened; round the 65mm aperture on the front, and for kicks, the entire backside...

The 65mm aperture can certainly be practical from time to time, and for a 65mm f/14.  Also, the textured front surface of the main cap was dulled with #0000 steel-wool.

I just love working on junk components, and in making them better than they deserve.

[Alan64]

And now, the best for last: the doublet, of crown and flint glass...

Marks were made for the spacers' replacement, and a mark to preserve a, albeit wishful, calculated rotational position of the elements.

The oversized, to me, black-paper spacers were history as soon as I laid eyes upon them.  They were also haphazardly-placed, one of them a good bit away from the edge...

The spacers were replaced with those of foil; each spacer of two thicknesses of aluminum-foil tape, if I recall, and smaller of course. 

Here, the edges of the doublet's two elements have been blackened...

Before and after, the doublet blackened and with its new spacers, at right...

Notice how the doublet appears much less...there...almost invisible.  That's the ticket.  That's what you want.

With the telescope reassembled, at last, the objective, before and after...

I've observed with it a couple of times thus far.  I'll put it this way...

The Trapezoid and its environs, within Orion, at 45x with a 20mm 68°: the nebula appeared as an island, its well-defined ghostly "shores" dropping off into a jet-black "sea".  I've simply never seen it that beautiful before, certainly not with my blackened and flocked 150mm f/5 Newtonian.

If you had seen it with your own eyes, you'd immediately set to work upon your own telescope(s), I'd wager.

That's all.

[Rob]

Very nice job on the rework there. Should serve you well I'm sure.