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Meade-Vorce "Polaris" 90mm f/10 Achromat OTA

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#1 Sky Muse

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Posted 09 September 2018 - 02:14 AM

Get one before they're gone...

 

https://www.ebay.com...8.c100290.m3507

 

The box arrived, and without a dent, or even a scratch...

 

box.jpg

 

OTA.jpg

 

I remember seeing cars of that colour, back in the '70s, Fords I think, and boy were they ugly.  It's more of a royal-blue than a true-blue.  I never liked royal-blue.

 

A red-dot finder came with it, and the battery's not dead...

 

red-dot finder.jpg

 

...but I can't attach the finder at present...

 

sheared thumbscrew2.jpg

 

sheared thumbscrew.jpg

 

Fortunately, I was able back the lower half of what was once the thumbscrew out enough to create a slot with a diamond-file...

 

sheared thumbscrew3.jpg

 

After awhile, after dinner, I decided to tidy up and put the bubble-wrap back in the box.  As I was straightening out the wrap, all of the sudden something fell onto the floor...

 

sheared thumbscrew4.jpg

 

lol.gif

 

Now, that thumbscrew was not sheared-off during the shipping, as the box was utterly undamaged.  I've contacted Mr. Vorce, and for a replacement.  We'll see how that pans out.

 

 

 


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#2 Sky Muse

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Posted 09 September 2018 - 02:54 AM

The specs label; it's awfully nicer than that of a Celestron...

 

specs label.jpg

 

At the heart of every refractor, is the objective; and in this case, a clear, unobstructed 90mm achromatic-doublet...

 

doublet.jpg

 

The lenses are pristine, aside from specks of dust; not a single smear to be found.  This one sure beats that Meade 390 I got back in the early '90s, and then promptly returned.  Its doublet looked like it had fallen into potting-soil, and then hurriedly crammed back into its cell.  It may have been cracked even.  It's hard to recall with all of that dirt that was on and within it.

 

I feel a blackening and flocking coming on.  You can see the baffles somewhat within the tube, within that image.  Those will be causing me problems.  Those enormous spacers are history.

 

I can't test it out yet, let alone star-test it out, as it's wet outside; ain't that the way it goes?  I can't work my magic until after then.  

 

The dust-cap; nothing special...

 

dust cap.jpg

 

Now, the focusser, on the other hand, is indeed special.  It's all of metal, aluminum, even the 1.25" visual back...

 

drawtube.jpg

 

With the drawtube extended all the way out, there's a little slop, but not much.  PTFE strips will fix that. 

 

I may not have a full 90mm of aperture, as the tube-wall encroaches into the light-path, and at least by its thickness.  The tube itself is 90mm in diameter, and I have the tube-rings picked out, but I'll want a longer dovetail-bar.  The bottom of the flint is situated somewhat above the rim of the tube.  Perhaps the light gathered will be refracted and skirt by just inside of it.  I have no idea. idea.gif   

 

Stay tuned for its first-light, when I'm able. popcorn.gif


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#3 starman876

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Posted 09 September 2018 - 08:35 AM

The specs label; it's awfully nicer than that of a Celestron...

 

attachicon.gif specs label.jpg

 

At the heart of every refractor, is the objective; and in this case, a clear, unobstructed 90mm achromatic-doublet...

 

attachicon.gif doublet.jpg

 

The lenses are pristine, aside from specks of dust; not a single smear to be found.  This one sure beats that Meade 390 I got back in the early '90s, and then promptly returned.  Its doublet looked like it had fallen into potting-soil, and then hurriedly crammed back into its cell.  It may have been cracked even.  It's hard to recall with all of that dirt that was on and within it.

 

I feel a blackening and flocking coming on.  You can see the baffles somewhat within the tube, within that image.  Those will be causing me problems.  Those enormous spacers are history.

 

I can't test it out yet, let alone star-test it out, as it's wet outside; ain't that the way it goes?  I can't work my magic until after then.  

 

The dust-cap; nothing special...

 

attachicon.gif dust cap.jpg

 

Now, the focusser, on the other hand, is indeed special.  It's all of metal, aluminum, even the 1.25" visual back...

 

attachicon.gif drawtube.jpg

 

With the drawtube extended all the way out, there's a little slop, but not much.  PTFE strips will fix that. 

 

I may not have a full 90mm of aperture, as the tube-wall encroaches into the light-path, and at least by its thickness.  The tube itself is 90mm in diameter, and I have the tube-rings picked out, but I'll want a longer dovetail-bar.  The bottom of the flint is situated somewhat above the rim of the tube.  Perhaps the light gathered will be refracted and skirt by just inside of it.  I have no idea. idea.gif   

 

Stay tuned for its first-light, when I'm able. popcorn.gif

Heck I got some 100mm I will let go for that pricegrin.gif


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#4 grif 678

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Posted 09 September 2018 - 04:21 PM

I think Bill Vorce will fix the problem, he is a respectable person.


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#5 Sky Muse

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Posted 09 September 2018 - 06:30 PM

I think Bill Vorce will fix the problem, he is a respectable person.

I think so, too.  I got a reply, and in their asking if everything else is allright with it.  I hope they have one.  I'm not envisioning their having a box filled with them on a shelf.


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#6 Sky Muse

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Posted 09 September 2018 - 06:39 PM

Heck I got some 100mm I will let go for that pricegrin.gif

I already have a 4".  This 90mm will be my largest achromat, for the usual and white-light solar, and to hopefully exonerate the Meade 90mm I had received back in the '90s.

 

Although, someday I might get this...

 

https://www.astronom...ube_p11923.aspx

 

...and build a mount for it out of 2x4s. smash.gif



#7 Sky Muse

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Posted 09 September 2018 - 07:32 PM

In the getting of this achromat, I did so for myself, of course, but equally for those first starting out.  Many of these beginners are reluctant to place a goodly chunk of their wherewithal into what might be a passing phase, or so they think.  Most of us have food, rent, mortgage, utilities; expenses, and that for other leisurely activities.  Now, I'll eat at home, me gruel, and get a nice something or other that's astronomical in nature; and instead of taking everyone out to eat.  But I may be one of the few, therefore I don't want them to have to throw away what they acquired initially, and when they upgrade from it in a, happily, sustained interest.  A first telescope should be just as good as the last, for a treasured memory, and the continued use of same.

 

I do expect, however, for everyone who first acquires a telescope to be able to work on it; the mechanical aspects.  But the figuring and polish of an objective is not fixable, and that happens to be, by far, the most important part of a telescope.  Therefore, it is my desire, my drive, to find out if these manufacturers are aware of this, too.

 

On the home front, it's still overcast and damp.  I can't perform a star-test with this doublet, not to mention its collimation upon arrival.  On rainy days like this, you remain indoors, and putter, and what would be finer than to remove the doublet and blacken its edges; to measure it, and to know what was taken away from the spec: 90mm...  

 

I want every last millimeter, and I want it for everyone else, too.  Will it be 88mm, or 86mm, as I'm expecting?

 

But I can't do all of that until after it's tested in its raw state, fresh from the factory; fresh as a fresh-baked apple pie on a window's sill.  "Catch-22"...


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#8 tony_spina

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Posted 09 September 2018 - 09:49 PM

Are you doing a flashlight test to check the aperture? 



#9 Sky Muse

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Posted 09 September 2018 - 11:22 PM

Are you doing a flashlight test to check the aperture? 

I read up on the method.  I suppose I could attempt it.  By the way, you won your guess; I think, in that you may have thought it to be the 90mm f/6.7 discussed previously within another thread?



#10 tony_spina

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Posted 10 September 2018 - 12:21 AM

Yes I knew that the 90mm was missing in your arsenal. Thus my guess.

 

The 90mm f6.7 that I picked up from Bill is very good.  I’m putting it together for a family friend and their kids. It will ride on a AZ3 mount with slow motion controls that I had lying around taking up garage space



#11 Sky Muse

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Posted 10 September 2018 - 12:44 AM

Do revamp the focusser.  Have you any PTFE sheets, yet? 

 

https://www.eplastics.com/sheets/ptfe

 

I had gotten a square-foot each of the .005", .010", .015" and .020", and it was rather economical.

 

I checked mine again, and there's slop when it's racked all the way inward.



#12 tony_spina

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Posted 10 September 2018 - 05:51 PM

Don't recall any slop in the focuser on the 90mm f/6.7.  Did have some astigmatism due to the retaining ring being too tight.  But that was an easy fix


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#13 Jaimo!

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Posted 11 September 2018 - 08:27 PM

I love threads like this, economical observing, very useful for a beginner or someone not willing to part with a fortune.  Keep up the good work.

 

Jaimo!


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#14 starcanoe

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Posted 11 September 2018 - 08:42 PM

Could the focuser be used as a two inch?

 

And whats the story on a 90 f6.7.....I'd kinda like to get my hands on one of those.


Edited by starcanoe, 11 September 2018 - 09:28 PM.


#15 tony_spina

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Posted 11 September 2018 - 10:31 PM

Could the focuser be used as a two inch?

 

And whats the story on a 90 f6.7.....I'd kinda like to get my hands on one of those.

You could put a GSO 2" focuser on the 90mm

 

I got the 90mm f6.7 from Bill when he listed them on CN



#16 starcanoe

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Posted 11 September 2018 - 10:37 PM

I am not interested in putting a 2 inch focuser on such a scope. I am wondering if the scopes focuser drawtube is big enough to be used as a 2 inch focuser.



#17 Sky Muse

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Posted 11 September 2018 - 11:09 PM

Could the focuser be used as a two inch?

 

And whats the story on a 90 f6.7.....I'd kinda like to get my hands on one of those.

My own is the "Polaris" 90mm, and at f/10.  The 90mm f/6.7 is the "Infinity" version...

 

https://www.bhphotov...SEALw_wcB&smp=y

 

The drawtube of my 90mm is only 1.625" in diameter; not quite up to 2", regrettably...

 

drawtube2.jpg

 

...and that of the 90mm "Infinity" appears likewise.  It is possible, however, to replace the 1.25" focusser with a 2".  Incidentally, the 2" focusser of my Antares 80mm f/6 fits the tube of this Meade 90mm f/10 like a glove...

 

2-inch foucsser.jpg

 

...however, the focusser is not oriented per the Meade emblems and the fixed dovetail-bar, but no matter.

 

Also, the tube-rings from the Antares fit the tube of the Meade, so there will be no need and expense in acquiring ones specifically for same...

 

Antares tube ring.jpg

 

Earlier, and partly due to the parts from the Antares fitting perfectly scared.gif , I was concerned as to whether or not I would have a full 90mm of aperture.  I just took this snap, through the fully racked-in focusser, and it appears that little to no loss is to be expected...

 

aperture.jpg


Edited by Sky Muse, 11 September 2018 - 11:10 PM.

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#18 starcanoe

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Posted 11 September 2018 - 11:16 PM

Thanks Sky Muse

 

Bummer that focuser isn't a true 2 inch. On the other hand...if it is only meant for 1.25 inch format there is a a bit of room in the there for flocking and or small baffles.

 

Hmmmm....some folks here will probably be grabbing these up...I have 4 or 5 true 2 inch focusers like you have shown above that I've been meaning to sell lately...might need to get those ads up.

 

I have the Meade F8.8 90mm. It sure is fun with a 2 inch diagonal and 50mm plossl. The focuser is plastic and I just took the end piece off and jammed the diagonal in there...tight enough a fit in the tube that it stays put.


Edited by starcanoe, 11 September 2018 - 11:30 PM.


#19 tony_spina

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Posted 12 September 2018 - 12:22 AM

I am not interested in putting a 2 inch focuser on such a scope. I am wondering if the scopes focuser drawtube is big enough to be used as a 2 inch focuser.

It comes with a 1.25” focuser.  The Meade 102s come with the 2” focuser



#20 Sky Muse

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Posted 12 September 2018 - 01:54 AM

It comes with a 1.25” focuser.  The Meade 102s come with the 2” focuser

Then that 102mm "Infinity" would be the one to get, and to take advantage of the wider fields-of-view.  At f/6, you could use up to a 2" 40mm eyepiece, with a 6.6mm exit-pupil; well within the 7mm maximum of the dark-adapted eye, and for a low, low 15x; binocular-like even.


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#21 Sky Muse

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Posted 13 September 2018 - 12:27 AM

I just went out, and I saw Mars, clear as a bell, yet through the wispy overcast.  I don't need a planet to test this achromat, but a star, and nary a one to be seen.  

 

It's chomping at the bit to get out there...

 

achromat.jpg

 

...but it will just have to wait, perhaps later this morning if the overcast subsides further.  I can't crack this telescope open, to address and enhance its innards, until after its first-light, and more importantly, a star-test.

 

Incidentally, Mr. Vorce himself finally replied to my enquiry about the thumbscrew, and with the news that he has one, and as of now it has already been mailed out.


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#22 Sky Muse

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Posted 13 September 2018 - 11:02 PM

The replacement thumbscrew arrived; my profound thanks to Mr. Vorce...

 

thumbscrew - 091318.jpg

 

achromat2.jpg

 

                                                   whee.gif


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#23 Sky Muse

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Posted 14 September 2018 - 05:11 AM

At last, the skies cleared substantially, so I took the 90mm f/10 achromat out on the Voyager I alt-azimuth, and set it up facing east.  I used the Vixen 30mm Plossl(30x) and framed the Pleiades, gorgeous, but most importantly, the Astro-Tech "Titan" 70° 10mm(90x) for the star-test; not to mention a spectacular view of the Trapezium and nebula of Orion.  This 90mm is rather bright, in that it collects ample light under my skies.  The patterns of the star-test appeared most satisfactory, intrafocally, and extrafocally(although less clear, as usual).  Intrafocally, I could clearly see the spacers of the doublet jutting into the pattern, and at two points.  Needless to say, those will be removed and replaced.  I had little problem finding the sharpest focus; not quite snap-to, but very close.  The crescent Moon had set hours before, therefore the sky was at its darkest, and ideal.  I had seen the Moon the evening before, with just the eyes, and part of a planetary conjunction of sorts.  I used the red-dot finder that came with the telescope, and it's rather bright to where I had to dim it down, so it's certainly working.  I used Rigel to align it.  I took a snap of Betelgeuse, but I couldn't capture the detailed diffraction rings sloughing off of it in waves.  The last object I observed was Sirius, as it had finally risen a bit over the trees for a look-see.

 

Afterwards, I must say, the false-colour is well controlled with this one, and expectedly so, at f/10; thus far.


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#24 Sky Muse

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Posted 20 September 2018 - 10:21 AM

The dovetail-bar that came with my Antares 80mm f/6 achromat, purchased in 2015...

 

805ub.jpg

 

...has always been too short for balancing, especially with a 2" diagonal and ocular fitted.  I got this 13"-long bar back in 2003, misplaced and forgotten during the interim, and practically unused...

 

new dovetail.jpg

 

The original 6mm hex-head bolts for the Antares' tube-rings made use of the threaded holes of the rings as "nuts", and are consequently rather short in length.  I did not want to fit the rings on the new bar that way, but with nuts in addition, so I went to my local hardware and got two longer 6mm bolts, three 6mm nuts, and one set of washers, flat and lock.  Two sets of flat-washers and lock-washers were already included with the Antares. 

 

I used one of the original bolts and the new set of washers as a stop on the lone far end of the 13" bar.  Alas, but not surprisingly, the 6mm bolts would not thread into the holes of the long bar, and I didn't want to wallow out the threaded holes of the rings, so I wallowed out the threaded holes of the bar instead.  One of the new 6mm bolts for the rings is a Phillips-head, a recess drilled out of the hole for it there at the center of the bar, and so to be able to slide the bar back and forth for balancing, unfettered...

 

new dovetail3.jpg

 

I had to grind down the tips of the new bolts, as they were just a wee bit too long, yet ideal for digging into the optical-tube when clamped.  Stainless-steel is not fun to work.  Both tips will now clear the tube...

 

new dovetail4.jpg   

 

I now have an ideal mounting solution for my two largest achromats, of slightly differing apertures I might add, and for diddly-squat.  The tube of the Meade 90mm...

 

tube rings.jpg

 

tube rings2.jpg



#25 Sky Muse

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Posted 22 September 2018 - 02:13 PM

The fixed dovetail-bar had been removed, and therefore required the filling-in of the holes.  I got two plain-steel M5 flat-top screws, 10mm long, at my local hardware, and sawed them down to about 5mm in length.  The tips were painted, and the smooth surfaces sanded and roughened...

 

fillers.jpg

 

Before installing, I coated the undersides of the screws' heads, and the outer perimeter of the holes of the tube, after recessing the holes slightly, with J-B Weld epoxy...

 

old holes.jpg

 

old holes2.jpg

 

I couldn't recess the holes to accommodate the heads fully, as I didn't want to risk drilling out the threading of the holes.  I used the largest bit I had, and considerable in diameter, but endangering nonetheless.  Once the epoxy cures, I will then test it to make sure that the heads won't catch onto the tips of the bolts fastening the tube-rings to the dovetail-bar.  

 

I will have the option, however, of grinding down the heads afterwards if they do threaten to catch, then I can paint the heads to render them as inconspicuous as possible.

 

I hate fixed dovetail-bars, and I'd be willing to bet that you do, too.




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