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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.
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 Steve originally made the Telrad body using urethane models from which he cast the body in aluminum.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!
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.
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.
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:
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 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.
The center of the window is about 3-½ inches (89 mm) above the platform (telescope, stage light, etc.) upon which the Telrad is installed, and so seeing into the distance through the sight depends on being able to have the Telrad window remain above obstructions that might be in the way. The optional Telrad Riser is an accessory for the Telrad sight which elevates the Telrad from the Base by either 2 or by 4 inches. The Riser can be installed quickly and with no tools by the user. The Riser is available in either 2 inch or 4 inch heights, these are installed onto the Telrad Quick Release Base and the Telrad sight is installed onto the Riser. The upper platform of the Riser resembles the Telrad Base and accepts the Telrad Sight, while the bottom of the Riser matches the arrangement on the bottom of the Telrad Sight and thus fits perfectly into a Base. These Risers can even be stacked if desired to attain greater elevation.
Right: Telrad sight with optional 2 inch high Riser installed (67,567 bytes).
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":
Move the telescope to center the Telrad onto the bright star Betelgeuse (in Orion). Move the telescope to the left (west) about 2-1/2 Reticle diameters. This should put the telescope just about centered onto the Rosette Nebula.
Center the Telrad onto the bright star "Vega". Next move the telescope about two Reticle diameters (about 8 degrees) south east over to the two brightest stars nearest to Vega; these will be the stars "Sulafat" and "Sheliak". Move the telescope to position the stars "Sulafat" and "Sheliak" on the middle ring of the reticle at 9 and at 3 o'clock positions. The "Ring Nebula" should be just about centered in the Reticle.
The more you practice this skill, the easier it becomes to use the Telrad. And a side benefit will be that you improve your own ability to judge angular separations.
We have heard some people suggest that they day of the Finder is over since many modern telescopes incorporate computer controlled mounts that can slew the telescope optical tube from one object to another automatically. But we at Company Seven remind our customers:
Right: Meade 14" ACF telescope with lens shade atop Astro-Physics 1200GTO mount and Pier-Tech3 adjustable height pier; note one of the two Telrad sights with Dew Shield atop the telescope (47,204 bytes).
So in a sense the telescope and mount are being used as the finder, finding the target so that the surrounding field and its relationship to the object of interest too may be studied!
The Telrad And Star Charts
You may find it helpful to plan your first several observing sessions by using a star chart, with a properly scaled transparent "template" which shows the Telrad Reticle pattern. The template may be placed over the chart to help one navigate across the sky. You may purchase any of a number of commercial star charts which include a Telrad sight pattern overlay, or you may buy an optional overlay, or you make one yourself with the aid of a mechanical drawing compass possibly drawn over a chart printed from a computer planetarium program. The star charts we recommend include:
TELRAD SIGHT SPECIFICATIONS
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