Stellafane 2000

by Bob Midiri

July 28th marked the 65th Stellafane convention to be held on Breezy Hill in Springfield, VT. We left that morning from SE PA. for the 7 hour drive to the beautiful Green Mountains of Vermont. Accompanying me were my 2 sons Robert and Jason, and fellow DVAA members Vince Scheetz and Barry Johnson. Anxiously awaiting this first Stellafane of the new millennium, weather forecasts were checked and rechecked on the prior days leading up to the convention. And of course, the forecast called for 3 days of rain! After last years washout, this forecast wasn't a harbinger for a great start to the convention. On our ride North, clouds seem to be following right along with us, but miraculously by the time we reached Stellafane, the sun was shining brightly and so were our hopes. After checking in at the Abbey Lynn motel, we rushed back to the Stellafane observing field. There were a large number of scopes already setup, and a lot of solar observing. A very fine view of a solar prominence was seen through John Vogt's AP refractor equipped with a Hydrogen Alpha filter. John also came prepared with his beautiful 32 inch F4 award winning dob. His scope has a Hextek Borosilicate Gas Fusion Honeycomb Mirror, which is 5 inches thick, but only weighs 85 lbs. The primary sits on an 18 point flotation cell, with remote control collimation. This is one awesome scope, that also sports a computer controlled Alt/Az drive system. After finishing other solar viewing through some Televue's (one set up on a bowling ball mount) and AP refractors, we were off to the large tent for the mirror making demonstrations. A large number of demonstrations of varying stages of mirror completion were being conducted. From the kids pushing six inch mirrors during rough grinding, to polishing and even optical testing. Dave Kelly of the Springfield Telescope Makers (STM) had his Foucault testing tunnel set up. This is the ideal way of Foucault testing your mirror, to avoid temperature fluctuations induced by the environment or your own body. His tester is setup to do Foucault or Ronchi testing. A great idea he had is having a tape measure mounted from the mirror test stand, to the knife/light position, enabling a quick estimation of the FL of the tested mirror! Scott Mulligan of the STM's unveiled to us his recently constructed interferometer. The setup with the CCD camera and monitor made it easy for all to see him test a mirror against a reference flat.

After checking out the mirror demonstrations, and with crystal clear sunny skies overhead, we decided to grab an early dinner at a very good local Chinese restaurant (I won't say the name since after I raved about a particular restaurant last year, we found them out of business this year), so we could get back to do some observing. With beautiful skies overhead toward evening, scopes were being setup everywhere, from John's 32 incher, a 25" Obsession, an eighteen inch Astrosystems TeleKit, to fellow club member and President of the DVAA, Marilyn Michalski's beautiful homemade 10" F6.5 "Emerald" dobsonian scope. The views through this home brewed mirror are stunning! With darkness firmly set in, seeing the Milky Way with its dark rifts set against its luminous star fields was inspiring! Some easy naked eye objects observed were the "Coat hanger" asterism near Sagitta, Andromeda Galaxy, double cluster in Perseus, and even the great Globular, M13. With her scope, and dark skies, the great summer globulars were like a religious experience. Seeing highly resolved, tiny pinpoint stars, while using high magnification, is a testament to the fine optics of this scope. Through a 25" Obsession, the TRIFED appeared as a photograph with its well defined lobes. The Veil and the Swan nebulas looked as they were intended, through these dark non light polluted skies. Along with all this fine observing, we also were treated to some very bright meteors bringing Oohs and Ahhs from the crowd. Unfortunately by 1:30 AM, the clouds rolled in, and brought an end to any further observing at this years convention. As this busy Friday came to a close, many tired people, from the mirror and telescope makers, the horseshoe contestants, and to the large number of now exhausted kids, were ready for some shut eye, so all can get up at dawn for the famous SWAP TABLES! This is were telescopes, binoculars, ATM supplies, books and magazines are strewn about for all to thirst on. Even a 30" mirror blank was being offered as a temptation for some unwary TN ( Telescope Nut). A large number of bargain hunters were milling about, and even Telescope Talk and Star Ware fame, Mr. Phil Harrington was there, proudly sporting his new shirt "Cell-A-Fane"! Phil is a great guy, astronomer, author, and moderator of a very fine Internet talk group called "telescope talk". He presently is putting the finishing touches on "STAR WARE-3".

After the swap meet, it was getting near the time for judging homemade telescopes in Mechanical, craftsmanship, innovative component, and junior (16 and under) entries. My 7 yr. old son Jason entered his 6" F5 dob into the competition. He ground and fully polished this mirror (of course dad helped with the initial rough grinding, parabolizing, and wood cutting) over 3 months. He caught the bug watching his older brother making a mirror, when I taught some scouts mirror and telescope making for a merit badge. Also fellow club member, Marilyn Michalski, entered her beautiful 10 inch dob. Unfortunately for Jason and Marilyn, where their scopes really shine are in the optics, but optical judging was going to be clouded out.

According to Tom Spirock of the STM's, there were 40 scopes entered into competition this year. By the way, the STM's did another wonderful job for this years convention. After a tough year valiantly battling the proposed prison planning, and losing the judgment, they still fought and won on the use of IDA approved lighting fixtures at the prison which will be built just 3 miles South of Stellafane. To this years convention, some nice touches were added by the STM's. One was the ability to enter your scope into competition over the Internet at their web site, which cut down on the congestion around the Pink Clubhouse for the registrants. At the clubhouse, they also had a map of the judging area, for you to place your entrant number, so the judges know where your scope is. And finally, the placement of red blinking diodes, on the hill walking toward the clubhouse, was a God send. Thank you, and another awesome job done.

Out of the 40 scopes entered, the usual Dobsonians lead the pack, including a fully functional (both optically and mechanically), 1.5" F5 miniature truss tube dob, made by Barry Crist of Halifax, Pa. This year also has seen the rebirth of the Split ring equatorial. Two in particular were a 14.5" F6 by Ray Harder of Gravly, CT., and a 12.5"F6 by Al Francis of Middleburg, Pa. There were a ton of fines scopes, but time and article space are limited.

Al Francis made a beautiful 12.5" Split ring equatorial. Al said it took him about one year to make the 12.5 inch F6 mirror. The mirror was figured to better then 1/8th wave using the "Tex" program. The construction of this "non-ultralite" 250 LB scope was no easy task. Much thought and planning went into the design, from the drilling of 3 holes into the side of the then unfinished mirror blank allowing plugs to mount the mirror to the cell in lieu of mirror clips, to the fully rotating optical tube assembly. This eliminates the collimation problems associated with utilizing just the upper cage rotation scheme. According to Al: "The inner rotating cage was built by cutting four rings from plywood and fastening them together with six, 2' lengths of 5/8" all-thread. The rings are evenly spaced apart with the center 2 rings merely adding rigidity. The bottom ring is fastened to a central bearing which is sandwiched between the inner cage and exterior octagon base. The mirror cell is also bolted, from the top, to the bottom ring. The upper ring slides on four Teflon pads attached at the top of the octagon base. The tension on the Teflon is adjustable via 4 bolts on the octagon base. The upper tube assembly attaches to the inner tube by 6 knobs. It does not touch the octagon base. The mirror is removed for cleaning by first detaching the upper tube assembly and then removing the entire mirror and cell from the top of the inner cage". The diameter of the spit ring is 48 inches and made from double 3/4" Oak Ply. The mount is made with tripled 3/4" Oak plywood, while the upper cage utilizes 1/4" oak plywood. The aluminum truss tubes are connected by a ball and socket assembly, eliminating the need of figuring the angles when using conventional connectors. It took Al 25 months to make the scope, and he had assistance from Ron Newman. Ron's contribution to the scope was his design of the "Drag & Drop" clutch system and he installed the electronics. There are a total of seven, 6-volt batteries on the scope. The scope incorporates hand controlled electrical collimation, and drive corrector. The beautiful crayford focuser was made by Al. They are low profile with 2" travel and are user adjustable to lift in excess of 5 pounds. The stainless steel shaft size is 3/16", compatible with the JMI moto-focus. These focusers are available through Al's web page at: www.focuser.com and they go by the name "MoonLite Telescope Accessories". I know I will order one of these awesome focusers for my current telescope project, when I have a little extra on hand cash.

Joe Derek, from Hudson, New Hampshire last year had a beautiful award winning 12.5 inch dobsonian. This year Joe brought his beautiful 12.5 inch OTA, now mounted on his award winning German Equatorial mount. I asked Joe why he switched, "The equatorial mount was always my goal because it strikes me as a more attractive design. It allows me to follow objects at high magnification and offers me the potential for photography. At public viewing sessions, it gives me freedom from constant adjustment of the scope". The declination and right ascension axis are made of chrome-plated rods that are 45 mm in diameter - from hydraulic pistons - with 9" diameter steel plates welded on the end. The tripod base for the equatorial mount is made from a 12" diameter Sonotube with a triangle-shaped frame set inside. The Sonotube is covered with oak veneer. The three legs are made of oak and secured to a plywood base over-layed with oak. Also he has a rotating tube with the rings made of 3/4" oak veneer plywood glued together. High density polyethylene plastic are placed between the scope and the wooden rings, and it rotates on roller blade wheels. Joe stated that he "started construction on this mount around December, in the hope of having it completed by Stellafane". Of course the scope is motorized with synchronous DC motors on both axis for slewing, with his drive corrector. This is one beautiful scope, wonder what he will bring next year?

David Aucoin from Waltham, Mass brought his awesome 13.1 inch dob with a f4.5 "Coulter mirror". The scope is unique in design, David designed it to incorporate the altitude bearings into the mirror box. This enables the rocker to be only 2 inches high. A router was used for the altitude bearing cutout. The mirror box was also designed to someday hold a 16 inch mirror. The scope has a low center of gravity, designed to be ladder free, and fit into a subcompact car. From the ground to the eyepiece at zenith is only 62 inches. It was made of Baltic Birch, and has a no tool setup. Dave said the mirror was an older Coulter, and a good performer with a 1/8 wave figure.

Marilyn Michalski from Kimberton, Pa, and President of the Delaware Valley Amateur Astronomers completed her 2 year project called "Emerald". This 10 inch Dobsonian has a homemade mirror, which Marilyn completed to a very high accuracy. She had some guidance making the mirror through the clubs telescope making class. According to Marilyn she ran into 3 major obstacles while making this mirror. First: was getting the curve to the edge during rough grinding. Second: during polishing was obtaining a true sphere, and tackling a broad rolled down edge. Third: Was over parabolizing using a star lap, then returning back to a sphere. Well after all that, Marilyn came out with one excellent mirror. I have looked through this scope and the images are terrific! Marilyn searched a long time for appropriate designs of the tube and base. After a long search, she purchased plans from Barry Peckham of LITEBOX TELESCOPES in Honolulu, Hawaii. "I liked his use of wood, emphasis on light weight, and artistic integrity". The tube was ordered from Parks Optical Co. through Pocono Mountain Optics in Moscow, PA. This 72-inch tube was taken to an auto body shop, where a professional auto body paint (#38 Emerald Green, for the 1999 Cadillac Seville) was applied. She installed black velvet to reduce ambient/stray light inside the tube. Installation required two people: A smaller diameter tube was wrapped with the velvet and unrolled in 8-inch swaths into the fiberglass tube after being sprayed with 3M's "Super Trim Adhesive," Part No. 08090 (available in auto parts stores). The adhesive is sprayed on both the back of the fabric and on the tube section to be glued. The beautiful Baltic Birch was stained and polyurethaned , presenting a "Cherry wood" appearance. The scope has buttery smooth motion in both axis.

Hideaki Kimuva from Greensboro NC came with his beautiful dob containing a Meade 16 inch F4.5 mirror. Being an avid DSO observer, he obtained his Messier certificate with an 8 inch scope, but needed something larger for his present goal, the Herschel 400. He designed and constructed this awesome scope with help from members of the Greensboro Astronomy Club. Being 5'4" tall, size and weight were a major goal in designing this well thought out scope. The 18 point floatation cell utilizes welded stainless and carbon steel throughout, and has a 12 volt cooling fan attached. The open structure is designed for very quick mirror cool down. The mirror box is made with 3/4" Baltic Birch on the 2 sides that carry the 24" altitude bearings, and 1/2" Baltic Birch on the opposing sides to decrease total weight. The low profile mirror box/rocker assembly, only requires a four inch step for Hideaki to view the zenith. On the ground board, solid 1" thick natural rubber is utilized for the three feet which decreases vibration dampening time. The large altitude bearings, proper balancing, along with the use of ebony star and Teflon for the bearings, make this scope move with buttery smoothness. He also has dew heaters mounted on the secondary and primary mirror cells. The secondary cage weighs in at only 11 lbs including a Telrad and 80 mm wide field Celestron F5 scope. With a 32 mm plossl the 80 mm finder gives a large 4 degree FOV, which equals the outer ring of his Telrad. The mirror box and mirror assembly weighs in at 54 lbs, making this a very light weight and user friendly scope.

Kenneth Schlum from Lockport, N.Y had the most unusual scope at the convention. The scope uses four 24 inch square thin methacrylate mirrors in a quasi optics setup. According to Ken, this give an effective aperture of 72 inches, and he states he gets pin point star images. The scope is constructed out of electrical conduit, sort of Herschelian in nature, utilizing bike wheel rims riding on polypropylene V blocks as the altitude bearings. The azimuth bearing is made from a 3 foot trampoline, and uses ABS plastic in place of ebony star for the bearing surface. The 4 mirrors focus the light to a secondary screen made of micro glass bead. The light cone is then directed to an achromatic lens assembly in which he views through.

After checking out some of these unique telescopes it was off to the tents for 2 very interesting talks. The first was presented by Bryan Greer of Worthington, Ohio, and titled :"Thermodynamic Effects on Scope Performance". Bryan explained how the atmosphere acts as an "Air Lens", where differing densities of cold and warm air bend light waves in varying angles of refraction. This is why we see so much distortion, since layers of cold and warm air in our optical systems bend the light waves in different directions. A test called the "Schlieren Test" (which is a cousin of the Foucault test setup) has been used to measure how long a mirror takes to thermally equilibrate. Tests have shown that a six inch mirror requires three hours to fully equilibrate, that is if the temperature stays relatively stable! Even a 14 degree temperature difference between the mirror and the surrounding air, will give an error of 1 wave from peak to valley during the cool down. Some remedies mentioned were: 1) Use of a fan below the mirror. 2) Adequate space between mirror and the wall of the tube or mirror box. 3) Tube vents above the mirror. 4) The utilization of large thin mirrors to significantly decrease cool down time.

The next interesting talk was given by Alan Adler of Palto Alto, Calif. on "Flexing Spherical Mirrors into Quality Paraboloids". Al, took Bill Kelly's methods one significant step further. He wrote a computer program with ray tracing to find the optimum areas of the mirror to stress or flex to give a virtually perfect image. Kelly's idea was to flex the center of the mirror, Adler has developed a system that basically pulls on the center and pushes up the perimeter! He devised a system using "hardware" items for this procedure, and they include: a pusher cushion, a solid rubber side wall, an aluminum plate, a carriage bolt, a coil spring to regulate tension, and a pusher plate, which is a cup like structure that pushes the outside of the mirror. He has determined that for an F6 or faster system, to utilize this procedure, the mirror thickness should be no greater then 10% of the mirrors diameter. The strength of the glue needed is only around 8 PSI, but a two-part adhesive is required for total cure of the epoxy. The cup and the puller are the key, you must use isotropic materials (which flex equally in all directions), polycarbonate or aluminum being two such materials. The inherent problem of this procedure is, you guessed it, astigmatism. Anything being pulled or pushed off center is a major cause of astigmatism. The difficulty of pulling a mirror into a paraboloid is inversely proportional to the "F" ratio. I think I will stick to using a pitch lap for my Paraboloids!

The Saturday evening programs Master of Ceremonies was "Big Bob" Morse of the STM. Bob has one heck of a sense of humor, and had the large crowd in the tent in tears with laughter at times. Keeping a large crowd happy while the skies were deluging the fields with rain, is Bob's forte. First he always asks to know who the youngest and oldest attending the convention were. There was a 3 month baby as this years winner. Door prizes and the grand prizes were announced, and of course Big Al donated a ton of eyepieces, including Naglers, Panoptics, Radians, and Powermates. Fellow club member, Paul Perlmutter was fortunate to win the 4 Radians! The telescope awards, were then announced. My 7 year old son Jason, came in fourth place and boy was he proud. A nice touch added this year for the junior awards, was not only receiving a ribbon and certificate, but an eyepiece was given to each winning child and donated by Gary Hand from Hands On Optics! Kudos go out to him, since all kids love a gift, Thanks Gary! The Stellafane Shadowgrams was again presented by David Levy, a good friend of the late Walter Scott Houston. As this years convention closed on a soggy note, the many memories will last forever. The terrific work done by the Springfield telescope Makers is absolutely astounding. This is not a one week setup. These guys and gals have started preparing for next years Stellafane, as soon as this one ended. The grounds are marvelous, the food outstanding, the comradeship everlasting, the new telescope ideas refreshing, and the memories of Porter, Cox, and Houston permeating. Hope to see you there next year August 17th and 18th.

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