MORE THAN HALF OF THE telescopes made by amateurs are portable types that weigh less than 100 pounds, and may be carried out-of-doors for temporary use or separated into several parts and transported in a car. Another large fraction of amateurs' telescopes are kept permanently out-of-doors. These are usually bolted to concrete or iron-pipe pedestals and are protected from the elements by tarpaulins or simple boxlike housings-that can be rolled aside.

Nearly every telescope user dreams, however, of housing his instrument in a fixed observatory structure. A wide variety of such structures, all good, none perfect, are discussed in Amateur Telescope Making-Advanced. One rare type, shown in Roger Hayward's drawing below, was designated the "teepee" observatory by the late H. Boyd Brydon in a series of articles on "The Small Observatory and its Design," published in 1988 in The Journal of the Royal Astronomical Society of Canada. Its chief merit is its simplicity. It roughly approximates the hemispheric dome that pleases the geometric or esthetic sense, yet it does not require building the curved shape of such a dome. Not shown in this drawing is a third section of the slot closure that may be removed and set aside during use of the telescope.

An example of the teepee dome is shown in Figure 1. Here it is set on top of a square building instead of on the ground. This is the observatory of Thomas R. Cave, 265 Roswell Ave. Long Beach, Calif. The simple 12-sided wooden frame of the teepee is covered with aluminum-painted heavy roofing paper. Though unbacked, and in use for some years now, it does not show the starved-dog's-rib effect of sagging that one might expect.

In the top of this dome is a hatch that affords telescopic access to the zenith. The hatch is lifted by an automatic spring that is held down at other times by a line from below.

The dome weighs about 400 pounds and rotates on 12 ball-bearing roller-skate wheels. It houses an eight-inch long-focus (f/10) reflecting telescope used for planetary observation by its owner. Cave is the Recorder of Observations of Venus for the Association of Lunar and Planetary Observers. 1 Association's mimeographed periodical, The Strolling Astronomer, enables amateur observers to "meet" each month and discuss their ordinary observations less formally than in a full-dress printed publication.

MOST amateur astronomers would be happy to have in their back yard the combined garage-workshop-observatory shown in the drawing on the right. It was planned and built by R. C. Barton of 8265 Garfield Ave., Alameda, Ca., an electrical engineer and a former president of the Eastbay Astronomical Society of Oakland. Because of this observatory's height above the ground, surrounding trees (which never get shorter) are less likely to limit its visible sky than if it were situated at ground level.

The building is 16 by l8 feet, large enough for a two-car garage. But one car is kept in it, the remaining space being occupied by the workshop filled with machine tools and benches. To gain space for any large job the car may be run outside temporarily.

A practical consideration in the planning of this kind of unit is the fact that if the owner should later wish to move, the building could easily be converted to a two-car garage by the next owner. Thus expenditure for the observatory is justified on other than "frivolous" grounds. If suitably planned the entire observatory might easily be moved from the building beneath it.

There is no inside stairway. The observatory is reached by climbing the outside stairway shown, crossing a south-facing lounging

deck and entering through a large French door. In the daytime such a door lights the interior enough to make adjustments on the telescope possible in comfort. Some observatories are cavelike in the daytime even with the shutters open.

The upper part of the Barton observatory is 10 feet square. Its top is finished to a circular opening with a wooden collar on which are fixed eight rubber-tired rollers. One of these is driven by an electric motor and rotates the dome. "Traction is obtained by levers and pulley blocks that permit me to control the upward thrust of the drive roller," Barton states. There are light fixtures in all four corners. Whole paragraphs of description of this dome are contained in the detailed drawing.

The observatory walls are finished in plywood panels two stages high that can be lifted out and reversed so that charts may be attached to both sides. One panel is painted black for use as a blackboard in answering the neighbors' questions and in discussions among observers. The telescope is a 10-inch reflector.

A type of observatory that no amateur has built, so far as is known, consists of two half-domes, one slightly smaller than the other, each of which can be rotated independently and entirely around on its own base circular track. It has no shutters. Because of the simplicity of its working principle, its architectural cleanness and its mechanical allure, this type of dome is most seductive.

The prototype of this design was built many years ago at the Washburn Observatory of the University of Wisconsin to house a six-inch refractor with an Alvan Clarke lens once used by the famous amateur-professional S. W. Burnham of lynx-eyed fame. This type of dome has therefore become known by association as the "Burnham dome." Learning that this beautiful dome had been converted some years ago to the conventional type with slot and shutter, this department sent an inquiry to Joel Stebbins, then Director of the Washburn Observatory. The disillusioning reply was: "All I can say is that after some years of experience we all looked upon the double dome as nothing but a nuisance. The inner dome worked very hard and had to be opened very wide in order to get near the zenith. For stars at the zenith the dome is exceedingly awkward, and to turn from one star to another in that region might require revolving the whole dome 180 degrees. All told, we have never regretted the change, and we think the ordinary dome with a good wide slit is still the best arrangement."

FOR the defense, Walter Scott Houston, an amateur astronomer of Cincinnati and a former University of Wisconsin student, has listed some advantages of the Burnham dome:

"It favors those who locate stars with out use of setting-circles; they can see a large expanse of sky.

"When photographing, one can open wide (I have just been to the dentist) and not have to recap the camera because of vibration while the dome is shifted.

"In comet seeking it is a big help.

"The top of the dome structure is not cut away whereas the conventional dome is structurally weakened by the slot.

"If the pier of the telescope is placed off-center in the dome, the zenith can be observed."

Lyle T. Johnson of La Plata, Md. points out that some conventional domes also give trouble at the zenith, and that, even if the pier is centered, telescopes on German or English mountings will already be eccentric when pointed to the zenith, thus reducing the blind spot if any remains.

Roger Hayward mentions that the high solar towers at the Mount Wilson Observatory are topped by domes of this construction, though here the sun is never at the zenith and the nested domes are therefore ideal.

It is unlikely that the above pros and cons exhaust the subject. Perhaps the: cons will act as a challenge to some amateur, leading to a practical solution, so that the elegant Burnham type of structure may be used.

None of the experimenters followed Father Daisomont's working directions. I tried to do this, and experienced no troubles with contact, scratches or lap. The directions follow.

Use common, rough, unfilled mimeograph paper of the kind available at an commercial stationer. Cut out a rough circle an inch or so larger than the tool. Dilute white library paste until sloppy and smear it on the tool with the fingers, using a minimum covering amount. Dip the paper in water, lay it for a moment between blotters, and then place it on the tool. Smooth it out and leave it to dry for a while with no mirror on top. When the paper is finally dry, trim off nearly all the overhang with a razor blade.

Dab a dry wad of tissue or rag in dry rouge and dab this on the lap. Instead of attempting to spread it evenly, which may result in too much rouge, dab it in evenly distributed blotches, which will spread under work. If the lap remains red instead of pink after a little polishing, with paper showing through white, make another lap. To remove the old one soak it a minute and scratch it off with the fingernails.

An important source of satisfaction with a paper lap is the ease of making another, so that there is no reluctance, as with a prized pitch lap, to destroy it. It also permits resumption of interrupted polishing with no preliminaries whatever. To those who do not enjoy the fragrance of hot pitch, or who are repelled by lovely messes, or find pitch possessed of seven devils, the paper lap is a lily-handed escape.

Suppliers and Organizations

The Society for Amateur Scientists
5600 Post Road, #114-341
East Greenwich, RI 02818
Phone: 1-401-823-7800

Internet: http://www.sas.org/

At Surplus Shed, you'll find optical components such as lenses, prisms, mirrors, beamsplitters, achromats, optical flats, lens and mirror blanks, and unique optical pieces. In addition, there are borescopes, boresights, microscopes, telescopes, aerial cameras, filters, electronic test equipment, and other optical and electronic stuff. All available at a fraction of the original cost.

SURPLUS SHED
407 U.S. Route 222
Blandon, PA 19510 USA
Phone/fax : 610-926-9226
Phone/fax toll free: 877-7SURPLUS (877-778-7758)
E-Mail: surplushed@aol.com
Web Site: http://www.SurplusShed.com