Restoring a Classic Edmund Reflector

by Kevin Meredith

In December 2021, I was given an unexpected early Xmas present. My girlfriend was walking through Princeton when she noticed this interesting collection on the side of the road, and she texted to ask if I wanted it. After I responded immediately in the affirmative, she knocked on the door and got the owner, Bob, to hold it for me in his garage. I should explain that up until this point, my best telescope had been an imported 4.5-inch Bushnell Newtonian; usable, but rather tacky. (As a matter of fact, the big screw holding the azimuth axis together on its mount had snapped earlier in the year – it was plastic.) So you can understand that a 6-inch scope represented a significant step up for me. I drove over a few days later to pick it up. Bob was a spry older gentleman with an enthusiastic attitude. He told us he was moving house, and needed to divest himself of some bulky items. The telescope was an Edmund Scientific scope that he himself had built from a kit his parents gave him in 1964. It was on an equatorial mount, also home built from stock plumbing fittings at the same time, to save a few dollars on a manufactured mount. You can see Bob welding it together in the newspaper clipping. Bob also gave me two original eyepieces and an Edscorp equatorial mount that he had acquired later but had never got around to re-mounting the scope.

After hauling everything home, I carefully disassembled the instrument to its component parts, which were all covered in a few decades’ worth of grime. The pyrex 6-inch primary mirror was coated in a thick layer of detritus and dead bugs. Miraculously, after giving them a careful wash, both primary and secondary mirrors were in good condition. I put a small dot of red ink in the center of the primary mirror to help with collimation. To protect the optics, I constructed a dust plug for the tube from some layered foam board and hot glue. I thoroughly cleaned every other part of the telescope inside and out, applying a little lithium grease to the movable parts in the focuser and mirror cell. Scrubbing the interior of the tube was quite a reach as it is about 5 feet long. Dividing 5 feet by the 6 inch mirror diameter gives the scope a focal ratio of f/10 or so; more on this later. A lot of the steel screws and nuts that held it together were corroded, or had been replaced with mismatched parts, so I replaced everything with new stainless steel screws and locknuts for security. Although the cream enamel on the aluminum tube still shows plenty of scuffs and scratches, I decided not to re-paint anything. The marks of use should testify to the enjoyment this instrument has provided.

I decided to put the telescope on the Edscorp mount I had been given. The mount first received a thorough cleaning and lubrication. I fixed two stainless bolts in place protruding from the telescope tube, and used wing nuts to fasten it to the plate on the mount. This allows for quick take down and reassembly. However I quickly discovered that the bottom end of the OTA would often hit the mount legs, and the counterweight was not sufficient to balance it. A quick check revealed that this particular mount was actually designed for use with Edmund’s smaller 4.5-inch reflector. The larger mount would have included an RA clock drive and more weight. Nevertheless, this mount seemed sturdy enough to hold the scope, so I moved the mounting further down on the tube and added an extra counterweight. The second weight is fixed to a bolt that I tapped into the original weight at right angles, to achieve balance in both axes. The final result stays where it is aimed and can be quickly adjusted for using heavy eyepieces or camera gear.

Collimation of this telescope is fairly simple. The tricky part is aligning the secondary mirror, which is mounted to a simple brass rod. The rod goes back through a hole in the tube to the eyepiece assembly where it is held in place by a set screw. One must simultaneously hold the mirror in place and tighten the screw while looking through a collimating eyepiece. This operation almost requires three hands, but is made easier using a foam board wedge to hold the mirror at the correct distance from the tube wall to center it. The primary mirror cell employs the common three-screw adjustment system and is relatively easy to align.

A little research revealed a few things. It seems that this particular telescope kit was sold by Edmund from the late 1950’s to early 1970’s as the Super Space Conqueror. At the time, an assembled model would have cost around $200, which is $1800 today adjusted for inflation – it was near the top of their range, and indeed I was impressed by the quality of the components. Apart from the optics and the bakelite focusing knobs, everything is metal, with an aluminium tube and mirror cell and chromed brass focusing gear. At the time, Edmund was also selling 3-inch reflectors with cardboard tubes for 30 bucks!

Oddly, all the printed materials referred to their 6-inch model as having a parabolic mirror with a focal ratio of f/8, meaning that the focal length and tube should be about 4 feet long. Yet my example, with its 5 foot tube, is certainly f/10. I have a small clue as to why this might be. Bob gave me a cardboard star-finder that came with the kit, with the name and address of the Anchor Optical Co. It is shown above with the slip cover he made for it in school, illustrating altitude and azimuth. Anchor was Edmund’s clearing house for their, shall we say, less desirable optical components. Perhaps, to shift a few f/10 mirrors, they sold a version of the kit with a longer tube. If anyone reading has more definite information I would be happy to know it.

I have taken the telescope out on a few of the clearer nights this winter. Using both the originals and some newer eyepieces, I have been able to observe fine detail in many subjects. These include the Moon, Jupiter, Saturn, the Orion Nebula including five distinct stars in the trapezium, the Pleiades, and various other stellar clusters. A video of the Moon crossing my small CCD can be found at https://youtu.be/wTJ8OJwEcxA Although some might consider it primitive in today’s world of off-the-shelf SCT’s with go-to tracking mounts, it has been great fun to restore and use this old Newtonian on its simple equatorial mount. It makes me wonder how much less light polluted the night skies over New Jersey might have been nearly 60 years ago when it was assembled. It has sparked my interest in astronomy again, and I hope this telescope will see another half-century or more of use.

This entry was posted in February 2022, Sidereal Times and tagged , . Bookmark the permalink.

2 Responses to Restoring a Classic Edmund Reflector

  1. D. Skitt says:

    Very nice to see another telescope brought back to light!

  2. charlotteanne says:

    I have one of these telescopes that is in need of a good home and refurbishing. I am in Woodbury and would be glad to hold it for someone who would love it or use it for parts! email charlotteanne.lucas at gmail

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