TELRAD SIGHT

Above: Telrad Sight with furnished Quick Release Platform - viewed from right rear. Note three control knobs at rear for adjustment of reticle pattern onto display window and on the right side at the rear is the on-off and brightness adjust dial lever (97,541 bytes)

The Telrad is a one power (1X) sight that was originally designed for installation onto astronomical telescopes as an aid to locating deep sky wonders at night. While it was not developed as a tool for daytime use, some of our customers have adapted the Telrad sight for uses we never anticipated; for example many stage lighting technicians adopted the Telrad to help them point spot lights in the theatre.

The Telrad can be employed as the sole or primary sight of a telescope to help you "star hop" using visible stars to find and center objects that would be invisible to the naked eye or in other small finder telescopes. Or, you may choose to use a Telrad in combination with a second conventional magnifying finder telescope. The Telrad is the innovative, dominant choice of finder sights by the amateur astronomy community, and it is not uncommon to find a Telrad on professional observatory telescopes too! It is a particular favorite among experienced amateurs using deep sky telescopes (particularly our larger "Dobson" style telescopes) where aperture and the ability to find faint deep sky objects are concerns; these include our Astro-Systems and other fine Dobsonians by Obsession and Star Master. The Telrad is often the choice to replace economical finders sights provided on telescopes such as the Orion model XT-10, XT-8, and XT-6. Most of the big telescopes found at any star party get-together will probably have a Telrad on it.

However, because of the Telrad's ungainly appearance and moderate bulk the Telrad is not generally selected for use on smaller, fork mounted telescopes such as the Questar 3-1/2, Maksutov-Cassegrain, or C-5 Series fork mounted Schmidt-Cassegrain, or compact 70mm to 105mm aperture Achromatic and Apochromatic refractor telescopes such as those we offer by TeleVue and Astro-Physics. Customers who do not need the larger field of view of the Telrad, and seek a more compact sight for use with smaller telescopes may wish to consider our Qwikfinder.

History:

The beginnings of Telrad, Inc. originate in the late 1970's when Steve Kufeld of Huntington beach, California came up with the economical sight to help amateur (and professional) astronomers find their way across the night sky. Steve based the Telrad concept on World War II vintage bombsight technology; he simply came up with a new application for it. By the late 1970's Steve had arrived at a prototype. Steve originally made the Telrad body using urethane models from which he cast the body in aluminum. Soon afterwards, an ABS plastic injection mold was made. Since about 1982 this is the basic form of the Telrad which would not be altered to the present day. And since then Telrad has found better ways to make the sight, increased production volumes and improving economy of scale, and so the cost of the sight has remained the same!

Telrad Arrangement:

The Telrad sight is composed of two components: 1) Sight, and 2) Base. The Sight houses the power supply (two "AA" batteries), an on off rotary switch which also can vary the brightness of the display, a red L.E.D. lamp, the Telrad reticle, a mirror to divert the light up towards the 45 degree inclined display window, and a lens to bring the image of the reticle to focus on the window.

Left: Telrad sight reticle pattern projection arrangement (not to scale):
1. Red L.E.D., 2. Telrad reticle, 3. Adjustable tilt flat mirror, 4. focusing lens,
5. display window inclined at 45 degrees shown with simulated projected reticle. (6,999 bytes).

The Telrad optical arrangement is simple, and yet reliable. It provides that the Telrad's distinct pattern, adjustable in brightness, will be projected by a long life red Light Emitting Diode onto the display window. When the window is viewed from the observers vantage point then the pattern will appear to float, apparently suspended in front of the stars or other objects in the background. The Telrad sight is delivered from Company Seven with the reticle pattern focused onto the window. The focus is factory set by the adjusting the spacing between the L.E.D./reticle assembly and the focusing lens. The L.E.D. and reticle assembly are cemented into place within the Telrad housing. One must use care when installing or removing the two "AA" batteries (optional - not included with the Telrad) not to dislodge the L.E.D. reticle assembly.

Left: Telrad Sight Reticle Pattern - display set to near maximum brightness to show up better in photograph (4,298 bytes).

The reticle pattern is scaled so that each one of the three circles appears to cover a set area of sky: 4 degrees for the outer circle, 2 degrees for the middle circle, and 1/2 degree for the circle in the center. And so Star hopping (moving from one star to another) with the sight is very easy:

• the view through the window is "normal" and not reversed left to right, and up side down as is common in many telescope finderscopes,

• one may clearly see the area of sky around the Telrad window,

• the three projected circles help one to learn how to judge angular distances from one object to another.

• the intensity of the reticle can be varied, and with the optional Telrad Pulser blinking circuit kit it can be pulsed on and off repeatedly.

Telrad Installation:

Each Telrad sight is sold furnished with one sight Base. The Base must be installed onto a telescope at a position that will assure:

• the Telrad will not interfere with movement of a telescope - such as in a fork mount.

• the display window will be positioned at a point behind which the observer can easily view the window.

• the sight display axis will be close in line with the optical axis of the telescope, this is to facilitate the alignment of the displayed reticle pattern with the target seen in the telescope.

The Base is best left attached on to a telescope by any one of several ways, this is usually either by double sided adhesive foam provided with the base, or by attaching the base with mounting screws through the provided holes in the base. The Base could be strapped onto a telescope, or attached to an accessory plate by those who do not wish to risk marring the expensive finish of a fine telescope. Once the Base is attached to a telescope then the Telrad can be positioned onto and then secured to the Base by the two furnished metal thumb screws. Extra bases are available so that one may move the Telrad sight from one telescope to another.

Once the Telrad sight is installed onto the Base then then the reticle pattern must be aligned so that both the telescope and sight are centered onto a distant target. This adjustment my be made during the day or evening. The adjustment is easily managed by the three focus dials located at the rear of the sight housing. These three dials permit the user to tip or tilt the internal flat mirror to shift the position of the pattern on the display window.

Use of the Telrad

To locate an object with the aid of the Telrad, simply move the telescope so that a bright star or other object near the desired object comes into the display window of the Telrad. if the desired object is bright enough to see in the Telrad sight, then simply center the object in the center circle of the Telrad, and then move to the main telescope for detailed look. If the object to be viewed is fainter than what can be seen with the naked eye, then use the Telrad to navigate onto the target by "star hopping".

Some examples of "Star Hopping":