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1966 Sears 76mm f/16 Equatorial Refractor - "A Telescope made for Astronomers"
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The year was 1966 and the day was the 25th of December. Early that morning I woke up and joined my brother, sister and first cousin in the quest to see what Santa had delivered under the Christmas tree. There was a corrugated cardboard box with my name on it and it contained a nice big Lionel-Porter chemistry set of the kind you could do real experiments with. Over that box there was a note indicating that something else should have been there but did not arrive on time. I had no clue to what it was and a telescope was out of out of the question because I had received the standard 2.4” f/11 altazimuth refractor the year before. In addition, the chemistry set was quite a lot and no, I was not being spoiled. You see, the 25th of December is also my birthday (now everyone knows!) and my parents always made sure that I was not shortchanged due to that coincidence of holidays and gave me two presents. A couple of weeks went by and one day after school my mother, who never mentioned the second present again, told me to accompany her to the nearby Sears warehouse. The clerk in the warehouse took out this long box, and placed it in the car. Just a look at the box told me what the contents were and when we arrived at home mother told me to open up the box and take my birthday present. The box was opened carefully to reveal a rather long and beautifully finished wooden box with a label in the front indicating that inside I would find a Sears 76mm f/16 equatorial refractor. The catalog ad indicated that this as a telescope “made for astronomers”! I remember standing there flabbergasted and staring at the box for a while before actually opening it.
Arrival and Assembly:
The telescope had arrived in the second week of January 1967. You could say that I should not remember a lot about the assembly of the telescope but on the contrary, I do remember it as if it where happening today.
The impressive wood box had a couple of plastic bands as a safety measure to avoid accidental opening. I cut the bands and opened the box to find the three nicely varnished tripod legs enveloped in some translucent paper. A pouch in the inside of the box lid contained the instructions. Below the tripod legs I found the telescope optical tube assembly, the focuser, equatorial mount, eyepieces and hardware all neatly packed. The instructions were easy to follow and in no time I had assembled my first equatorial mount. The tube needed to have the focuser installed but that was straight forward. I placed the tube assembly in the mount and then finished the process by installing the dew shield and finder. An equatorial mount was something new to me and although I had read about it I had never used one before. The assembled telescope looked huge and challenging. The telescope objective was supposed to be collimated from the factory so no adjustment was attempted. Accessories with this telescope included 5 eyepieces. They were a 22mm Kellner, 12mm and 9mm Huygens and 6mm and 4mm Ramsdens, all of them had .965’ barrels. A prism diagonal was included as well as a porro prism image erector and a 2x Barlow. An extra accessory that I considered neat was a small tray light for the accessory tray in the tripod. There were also two filters, a green lunar filter and the now infamous eyepiece sun filter plus an eyepiece projection screen for solar observation, a safer alternative to the eyepiece solar filter. A very important and included “accessory” was that book that provided a lot of us with our first introduction to astronomy titled “The Telescope and The World of Astronomy” by Marvin Riemer (see figure 1). It was a simple and concise book for the beginner. The book was also the key to eventually become a member of the American Association of Variable Stars Observers (AAVSO). The 2.4” f/11 refractor had also included the book plus a one year gift subscription to that old classic “The Review of Popular Astronomy” (RPA). Last year marked my 40th anniversary of becoming a full member of the AAVSO. The RPA allowed me to learn about amateur astronomy in the mainland US and even establish communication with other amateurs.
Figure 1. Sears 76mm f/16 Refractor accessories. The only really good eyepiece here is the 22mm Kellner but the 6mm Ramsden is remarkably good too. How many remember that book?
I almost forgot to mention the12X40mm finderscope of excellent quality. The focal length is a bit longer than what we are used to find in finders these days. It is attached to the telescope with two ring holders (see figure 3). These holders allow movement of the finder to any comfortable position required. The focuser (figure 2) is smooth and well constructed with chromed focusing tubes that slide on small pieces of felt. There are a couple of small screws that can be used to collimate the focuser. The only problem is the .965” diameter of the focusing tube made for standard Japanese eyepieces. An adapter for standard American size eyepieces allows the use of better quality Plossls and Orthoscopics. In the lower right corner of the metal label on the focuser, right beside the serial number, you can see the stamped seal of the Royal Astro Optical Co. of Japan, the original manufacturer of the telescope.
Figure 2. Focuser with model and serial numbers. See the two adjusting screws.
The equatorial mount in this telescope did not include an electric motor drive although one was available as an option. A set of long flexible controls are used for slow motion in both right ascension and declination. The objective lenses are mounted in a push pull adjustable cell. I had very little idea of how good these lenses were. The telescope was completely assembled and placed in the corner of our family room where I would just sit and look at it for a long time waiting for that first clear night. It was a rainy January back in 67.
First Light I
First light for this telescope is fuzzier in my memory than the day I assembled it. It must have been sometime in the middle of January 1967 and probably on a weekend. I do remember that there was a problem adjusting the equatorial mount to the correct altitude. The mount had been designed to go as low as approximately the latitude of Miami but I live at 18 degrees north. In order to adjust it lower I had to remove the screw used to keep the altitude adjustment in place. In the end I decided to use it as low as possible with the screw in place and it was not that bad. Most of the first objects observed with this telescope were Messier objects and the planets especially Jupiter. The images were good to my young and untrained eyes and the telescope was a big advancement from my 2.4” f/11 refractor.
Figure 3 shows the telescope fully assembled as it looks today located in my observing location on the roof.
Figure 3. The Sears 76mm f/16 refractor as it looks today and during an observing session. Notice the 12X40mm finderscope and the 1.25” eyepiece adapter.
By March of 1967 I had been using the telescope almost every clear night. Sometimes, and to my parent’s discontent, I got up very early in the morning to observe some object that was not available earlier. On one occasion I had spent a long night of observing and inadvertedly left the telescope pointing up while taking a break. As a result, dew condensed over the objective lens to the point that it created enough accumulation for water to slide down the lens border, seep into the objective cell and end up between the achromat elements. There was no escape. In order to dry the water from between the elements the objective would have to come out. Being 13 years old, with no experience handling lenses, knowing that the instrument was still under guarantee, but eager to continue my observations, I took the risk and proceeded to dismount and clean the water from between the elements. Everything went well until I began to remount the lenses. Somehow the crown element slid from my hands, fell sideways in the towel I had placed in the table and quickly rolled into the terrazzo floor of the dining room splitting in two nice equal parts. I was paralyzed. How could something like this have happened? Well, it happened because I was careless, too confident and 13 when you think that you know everything, nothing bad is going to happen and you are going to live forever. As a consequence the 2.4” f/11 was again my main telescope until much later when I was able to replace the broken lenses with a 75mm f/15 Edmund objective that had to be fitted in the original telescope cell. The new lenses worked very well and their quality was excellent but somehow it was not the same. By 1976 I was pursuing my graduate studies and my astronomical endeavors had taken a low priority. I sold the telescope and lost track of the instrument for 20 years.
During the early 90s my interest in astronomy had revived. Pure and simple coincidence caused the second owner of the telescope and the author to meet in 1996. During our conversation the question arose as to the whereabouts of the telescope. After leaving my hands the telescope had been used a lot but at that moment it was stored in its box and had been there for quite sometime. Middle age nostalgia plus my rekindled interest in astronomy took over me. You guessed right, the telescope was back in my hands in exchange for another instrument. I took the now not so good looking and worn long box home and opened it with the same excitement of that January back in 67. The only thing missing was the tray light, probably a victim of worn out batteries. Every other part was there. My good friend had taken good care of the telescope. Nonetheless, the whole telescope needed some TLC to get it back to working condition. The Edmund lenses had not been removed since I had installed them many years ago and there was a healthy growth of fungus between the elements, something common in this humid and hot climate. The objective was disassembled, cleaned and replaced in its cell. Luckily these Edmund lenses had alignment marks. I started using the telescope for observing double stars listed in my old 1966 Norton’s and began to amass quite a hefty number of observations. The Edmund lenses gave excellent images but, in the Sears cell, they were a headache to collimate and center due to the fact that the original cell was built to accommodate a 76.2mm diameter objective. So, for years I kept looking for an original objective. Just recently and thanks to the very capable auspices of Sheldon Faworski, I was successful in my quest and able to get an original objective. These telescopes were made by Royal Astro Optical in Japan and the objective that I got from Sheldon was an exact match. Figure 4 shows the “new” original objective lens.
Figure 4. The new 76mm objective in the push-pull collimatable cell.
Second Original Objective: First Light II
The replacement objective was received in its original cell so it was easy to exchange the objectives without disassembly of the elements. This objective was in pristine condition as if it had never been used. It was a great pleasure to see the telescope as it had been 42 years ago before the “accident”. The “new” objective was collimated using a Cheshire eyepiece and I waited for the next evening. Fortunately, after a cloudy day, there was an opening at about 9:00pm and I took the telescope out on the roof just as it is in figure 3. My first object was Vega about 45 degrees in altitude. I did a star test that resulted in superb optical performance with only a tinge of purple in such a difficult star for an achromatic. Out of focus diffraction patterns were equal and focus was tack sharp. My next target was Antares and here I was really impressed. Just a bit above the first diffraction ring I could see the greenish companion. It looked like a gold and emerald ring. The optical performance of the objective was awesome. The eyepieces used for the tests were and 8mm Plossl and 6mm plus 4mm Orthoscopics. These eyepieces have standard 1.25’ barrels requiring an adapter. Much later that night I was able to observe Jupiter and although low in the sky, the images were superb showing several of the cloud bands and no purple fringing around the planet. The contrast was as expected for such a long focus refractor of excellent quality. Others that have tested objective lenses from Royal Astro Optical or Towa, both manufactures of refractors in the 60s, have met with similar results. Recently a set of tube rings and a dovetail mount from Orion allowed the use of this telescope with my EQ3 or Skyview Pro mounts. Using the EQ3 mount and my Phillips Webcam with a 2X Barlow I captured the detail of Jupiter’s atmosphere seen in figure 5. The altitude of the planet was less than 30° from the southwestern horizon at the time this image was taken and turbulence was very noticeable from heat radiated by the reinforced concrete roof of the second floor of the house. Just recently two images of the moon were obtained with the same setup showing the Sinus Iridum and the crater Gassendi both coming out of the terminator (figures 6 and 7). Both images show what the 76mm optics of this telescope can do even at high magnification. Double stars such as Zeta and Eta Orionis are easy targets for the 76mm objective and the pitch black field of view is a plus for deep sky objects.
This telescope has another definitive advantage. It is lightweight and easy to mount anywhere with the original mount or the EQ3. What do telescopes share with boats? They share a mathematical formula indicating that size is inversely proportional to use. As you can imagine, this 76mm is used a lot.
Figure 5. Jupiter with the 76mm refractor. Image taken on November 27, 2009 with Phillips Webcam and 2X Barlow. Poor seeing conditions.
Figure 6. The Sinus Iridum region with the 76mm Refractor at f/32.
Figure 7. Gassendi coming out of the terminator with the 76mm refractor at f/32.
What happened to the Edmund objective? It was in storage for sometime and before someone asks, no, it was not stored waiting for another terrazzo floor “accident” to happen. I have learned around the way and have mounted and dismounted many other objectives without a mishap (well… OK almost!). Sometimes I use the telescope with the old eyepieces just to compare observations and to remember how I saw objects through this telescope 42 years ago notwithstanding the fact that my eyesight was much better in those days.
On a final note I must say that one issue with this telescope is the mount. Although sturdy enough to hold the telescope, it is shaky in winds and any movement of the flexible control cables also produces vibrations. Visual observations are not impaired that much by this problem. Just recently the equatorial head underwent a total disassembly, cleaning and lubrication. The original lubricant had completely dried out to the point that it was ineffective. After reassembling and with the new lubrication the equatorial head moves very smoothly and is easier to control.
At an original cost of $199.99 or about $1000.00 in today’s dollars, the 1967 Sears 76mm f/16 equatorial refractor is an excellent telescope with superb optical performance especially suited for the observation of extended objects such as planets and the moon but also performing very well on deep sky objects due to its excellent contrast and dark field. Double stars are one of the best objects for this type of telescope. It is capable of resolving very difficult pairs for its aperture. The mount is adequate but should have been made more stable as it is prone to vibrations but then, it was 1967 and commercial telescope mounts were not what they are today. The optical tube assembly mounted on the EQ3 provides an excellent platform for visual observations and imaging. Nonetheless and for old time’s sake, I end up using it a lot in the original mount. Nothing like keeping tract of an object manually for hours as many of us used to do a long time ago when electric clock drives were a luxury and computer controlled telescopes were as much of a dream as flying automobiles. Who needs nice comfortable hand controlled clock drives anyway? We have been spoiled rotten and I am still waiting for my flying car!