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Equipment Discussions >> Classic Telescopes

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amicus sidera
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Re: Edmund 3011 6" F6 w/ late-70's GE mount - overview new [Re: amicus sidera]
      #5273131 - 06/15/12 03:46 PM Attachment (64 downloads)

Here's an exploded view of the motor and its shaft, the worm, ball bearing and setscrew described previously. I later cleaned and lubricated this part of the drive.

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amicus sidera
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Re: Edmund 3011 6" F6 w/ late-70's GE mount - overview new [Re: amicus sidera]
      #5273137 - 06/15/12 03:48 PM Attachment (50 downloads)

The motor itself rarely requires lubrication, but the geartrain (the pear-shaped box below the motor, and attached to it) is another matter. I don't feel that it's necessary to remove the geartrain cover for this operation, as Edmund appears to have very kindly specified a lubrication point on this motor! Note the small hole on the bottom plate, next to the motor shaft... a very light, high-quality oil can be introduced to the geartrain via this hole. In my experience, the oil migrates to all the gears inside fairly rapidly. I also place a drop or so where the motor shaft meets the bronze bushing, as shown below, as well as the two small pinions on both the bottom plate and the other end of the shaft (the latter not visible in the photo below).

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amicus sidera
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Re: Edmund 3011 6" F6 w/ late-70's GE mount - overview new [Re: amicus sidera]
      #5273145 - 06/15/12 03:55 PM Attachment (51 downloads)

The factory finder on the 6" f/6 is a 6X30mm convertible model... it can be used either straight through, or with a diagonal as seen here (the factory default method). If one wishes to convert to straight-through use, it is necessary to slide the objective lens forward in its cell to allow the eyepiece to reach focus - I've found that a piece of stiff paper, tightly rolled, serves admirably for this purpose. The eyepiece is then secured using the thumbscrew, and final focus checked.

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amicus sidera
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Re: Edmund 3011 6" F6 w/ late-70's GE mount - overview new [Re: amicus sidera]
      #5273166 - 06/15/12 04:09 PM Attachment (57 downloads)

It appears that, sometime in late 1981 or early 1982, Edmund discontinued the use of the high-quality, cast-aluminum-body 1-1/4" focuser for their 6" telescopes. My first 6" f/6, purchased in August of 1981, had such a focuser, while this recently-acquired instrument, purchased originally in April of 1982, has a focuser that is somewhat simplified.

Apart from the drawtube and the focuser knob shaft, it appears to be made entirely of black thermoplastic, and up-and-down movement is accomplished by means of the drawtube moving against a rubber tube which has been slid over the focuser knob shaft, alà Edmund's Astroscan.

Contrary to what might be thought at first, it actually works quite well, providing the rubber makes good contact with the drawtube. Replacement rubber tubing that is too thick exerts too much pressure, and makes focusing a bit difficult, but with the correct piece of smooth (not ribbed) tubing in place, it functions very smoothly. Additionally, the focuser knobs can be adjusted via setscrews to increase or decrease the stiffness of the focuser, by making them tighter or looser where they contact the focuser housing.


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amicus sidera
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Re: Edmund 3011 6" F6 w/ late-70's GE mount - overview new [Re: amicus sidera]
      #5273174 - 06/15/12 04:15 PM Attachment (50 downloads)

The focuser drawtube has two "tabs" on its very top, again in the style of the Astroscan, and these are bent outward to prevent the tube from accidentally falling into the OTA, should it be moved too far inwards.

Altenatively, one can be bent inwards to better grip the eyepiece.


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amicus sidera
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Reged: 10/14/11

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Re: Edmund 3011 6" F6 w/ late-70's GE mount - overview new [Re: amicus sidera]
      #5273177 - 06/15/12 04:18 PM

That's it... I trust that this information will be found useful to both current and future owners of these instruments.

A couple of final notes:

The Bad: Regarding what passes for setting circles on this mount: both are immovable relative to the castings, as they are glued on. The declination circle on this mount apparently got past Q.C. that day, as it is almost 7 degrees off; the RA circle not only isn't driven, it doesn't "slip", since it's attached with adhesive - which makes it pretty worthless, in my opinion. Many fledgling telescopists depend upon circles to find objects. What were they thinking?

The Good: I had concerns regarding the steadiness of this mount, since it uses 5/8" shafts like my old Palomar Jr., which trembled in the slightest breeze. Pleased to report that, once properly balanced, it's fairly steady, with settling times of about three seconds or so when given a small bump - much better than I expected.


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barasits
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Reged: 06/12/11

Loc: Chicago
Re: Edmund 3011 6" F6 w/ late-70's GE mount - overview new [Re: amicus sidera]
      #5273446 - 06/15/12 07:14 PM

An outstanding account in every respect! Bravo!

Geoff


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madeline
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Re: Edmund 3011 6" F6 w/ late-70's GE mount - overview new [Re: barasits]
      #5273489 - 06/15/12 07:46 PM

WOW, you really put it all on the line. You and alot of other people are a big credit to this forum. Fantastic job and I bet it was alot of fun doing it. Your photographs are the best. Thank you

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amicus sidera
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Re: Edmund 3011 6" F6 w/ late-70's GE mount - overview new [Re: madeline]
      #5275443 - 06/17/12 10:46 AM

Glad both of you liked it!

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amicus sidera
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Re: Edmund 3011 6" F6 w/ late-70's GE mount - overview new [Re: amicus sidera]
      #5275448 - 06/17/12 10:54 AM Attachment (51 downloads)

One more thing which I feel needs to be addressed on the 6" Edmund red-tube 'scopes is the matter of diagonal attachment.

The diagonal mirror is secured to its stalk by means of what appears to be an epoxy-type adhesive, without any other mechanical means of attachment, such as clips or brackets. Although I've not heard of one of these particular diagonal mirrors becoming detached, relying upon adhesive that is 30-plus years old is a bit of a gamble when one considers the consequences if it did let go. To prevent such an untoward event, I've taken the precaution of attaching safety wires to the diagonal mirrors on both my examples of this instrument.

The following photo shows the diagonal on its stalk, with a bit of the excess adhesive visible.


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amicus sidera
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Re: Edmund 3011 6" F6 w/ late-70's GE mount - overview new [Re: amicus sidera]
      #5275457 - 06/17/12 11:04 AM Attachment (39 downloads)

The safety wires that I used were made from stranded stainless steel wire, .012" in diameter, that was originally from a spool of model aircraft control line that I've had since I was very young, and is likely still available from hobby stores. I'm sure that I could have have utilized stranded or solid copper wire of similar size.

After the pieces were cut to the proper length, they were bent 90° in preparation for attachment to the underside of the diagonal mirror and stalk.


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amicus sidera
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Re: Edmund 3011 6" F6 w/ late-70's GE mount - overview new [Re: amicus sidera]
      #5275468 - 06/17/12 11:14 AM Attachment (35 downloads)

Below is a photo of one of the safety wires in position. They were attached by means of E-6000 adhesive, which is available in most craft stores. While a bit more difficult to work with than silicone adhesives, with less work time and a tendency to "thread", it does not outgas acetic acid while curing, and remains similarly flexible once dry.

With these wires in place, I can now transport and use these classic instruments without fear of diagonal detachment. In the event the original adhesive does eventually fail (which would almost certainly be noticeable as a failure to maintain collimation), the diagonal mirror can easily be reattached, with no damage occuring to either it or the objective.


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amicus sidera
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Re: Edmund 3011 6" F6 w/ late-70's GE mount - overview new [Re: amicus sidera]
      #5279401 - 06/19/12 06:47 PM Attachment (39 downloads)

Addendum: While becoming acquainted with this particular mount, I realized that there was no "stop" for the threaded strap-tightening shaft to keep it from unscrewing out of the strap bar, which might lead to the loss of the stap bar and straps from the saddle. Since the strap-tightening shaft uses a 1/4-20 threaded rod, a small portion of which extends outside the strap-tightening bar when the straps are completely slack, a 1/4-20 nut on the end of the shaft presented itself as a solution. Since only a few threads protrude from the bar at the loosest position, the standard method of placing a stop at the end of such a shaft, the double-nut method, was unusable in this case. As it was, a fairly shallow nut was required, having only 2 or 3 complete threads inside.

Having a suitable nut on hand, I proceeded to attach it onto the end of the threaded shaft with a breakable-strength threadlocker, which compound hardens anaerobically (in the absence of air) between the threads it's applied to. Only a small drop was needed, and I was careful to avoid exposure to the threadlocker itself, as it can produce an allergic skin reaction. I also made sure that the threaded hole in the strap-tightening bar was well down on the threaded shaft during application, as I certainly didn't wish to have any of the threadlocker get into those threads! See photo below.

Once dry, with the threaded rod is captivated, there is little danger of the rod being unscrewed so far that it loses contact with the bar, making for safer mounting and dismounting of the OTA. Should the straps need to be replaced for any reason, the nut is readily removed due to the use of the breakable-strength threadlocker.



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actionhac
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Re: Edmund 3011 6" F6 w/ late-70's GE mount - overview new [Re: amicus sidera]
      #5279526 - 06/19/12 08:02 PM Attachment (41 downloads)

Very nice overview of the 3011. I never see any red tubes around here but your excellent articles makes me even hungrier for one. They must have cost Edmund a fortune to manufacture. Especially that crazy diagonal support system.
I'm going to buy some E-6000 and add your safety wires. I have owned 2 older white-tube Edmund's where the glue failed, one landed precisely in the center of the primary in the shadow and one was less fortunate in the picture below.
Robert


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amicus sidera
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Re: Edmund 3011 6" F6 w/ late-70's GE mount - overview new [Re: actionhac]
      #5279544 - 06/19/12 08:14 PM

Ouch! I'd never actually heard of this happening, it just seemed a reasonable precaution... thanks for confirming my suspicions, Robert, although I heartfully wish you weren't able to do so!

Both of my 6" Edmunds have had the wire treatment, as has my Astroscan, the diagonal mirror of which is also glued on. The 8" f/5 has clips to hold the diagonal mirror in place very solidly, so haven't bothered to add wires to that one - although after seeing your photo, I may do so anyway!


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amicus sidera
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Re: Edmund 3011 6" F6 w/ late-70's GE mount - overview new [Re: amicus sidera]
      #5279577 - 06/19/12 08:37 PM

Two more items that may prove useful:

1. A minor improvement which I made to the OTA was replacing the plastic-covered screws and washers that hold the mirror cell to the tube with stainless-steel binder-head machine screws of the proper length... with their considerably lower profile, it's much easier to slip the straps over the back of the OTA while mounting or dismounting it.

2. The steel end of the declination tension knob bears directly upon the declination shaft when tightened, leading to marring and galling of the declination shaft. To correct this, I first removed as much of the galled, raised metal as I could from the declination shaft where the tension knob bears upon it. Then, using a leather punch, I punched a hole out of a piece of thick scrap leather (a heavy old belt, in this case) a little less than 1/4" in diameter, and placed a few drops of oil on the resulting round divot of leather. This divot was then placed into the declination tension knob hole leading to the declination shaft, followed by the tension knob itself. This small piece of oiled leather acts as a buffer, keeping metal-to-metal contact from occurring and producing a smoother "feel" to the declination axis motion.


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amicus sidera
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Re: Edmund 3011 6" F6 w/ late-70's GE mount - overview new [Re: amicus sidera]
      #5355165 - 08/06/12 05:29 PM Attachment (32 downloads)

One complaint that often arises among users of these mounts is the amount of looseness, or "play", that the polar axis exhibits.

The photo-diagram below shows the forces working upon the worm and driveshaft when the RA axis is moved... note that in one direction (towards the right in this photo), the worm is limited in its movement by a bronze pushing pressed into the casting, while the other direction has no similar limiter upon which the worm might abut, instead relying solely upon the retaining ring in the motor gearbox to limit travel. Since this retaining ring is loosely-toleranced, considerable movement in this direction can occur, with undue stress being placed upon the gearbox. Additionally, the stress imposed on the worm may cause it to loosen, resulting in the worm sliding along the driveshaft and losing contact with the ring gear...


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amicus sidera
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Re: Edmund 3011 6" F6 w/ late-70's GE mount - overview new [Re: amicus sidera]
      #5355190 - 08/06/12 05:41 PM Attachment (31 downloads)

What is needed is another bushing towards the motor side of the assembly to restrict the movement of the worm and driveshaft when under load, such as occurs when moving the telescope.

The diagram below shows the arrangement I devised to overcome this problem:


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amicus sidera
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Re: Edmund 3011 6" F6 w/ late-70's GE mount - overview new [Re: amicus sidera]
      #5355204 - 08/06/12 05:50 PM Attachment (30 downloads)

Since the casting already had a 5/8" hole bored in it to allow the driveshaft bearing the worm to be inserted into the housing, I made up a suitable bushing from 5/8" diameter plain steel round stock (incidentally, it appears that the design may have called for this bushing initially, but cost concerns led to its deletion from final production). A nominal 5/16" hole was bored in a 1" length of the round stock, with the end facing the motor being countersunk a short distance to accommodate the projecting bushing on the motor gearbox.

A hole was drilled in the underside of the casting and tapped with 10-32 NF threads to allow for a setscrew to lock the bushing in place:


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amicus sidera
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Re: Edmund 3011 6" F6 w/ late-70's GE mount - overview [Re: amicus sidera]
      #5355220 - 08/06/12 05:58 PM Attachment (25 downloads)

Finally, the bushing was inserted and the driveshaft and worm were placed into position. Two washers, one on each side, provide for a smooth bearing surface at either end, and the entire assembly was then "fine-tuned" for the slightest possible clearance while still allowing for free turning of the worm and driveshaft. Once its position was optimized, the bushing was locked into place by means of the setscrew, lubrication was applied where needed and the mount was then reassembled...

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