ASTRONOMY Borda's Repeating Telescope - 1820 and 50 similar items
More details about this item!!! NOTE !!! if the image(s) in the description shows a broken image icon(s), right click on the icon(s) and open in new tab to see the larger image(s). Astronomy Another Fine Quality Print from Martin2001 Legend : Borda's repeating circle (telescope) without reflection. The chief astronomical use of Borda's circle, which is that of determining the altitudes of stars upon the meridian by several observations near the meridian. The repeating circle may be very well used for getting the time either by equal altitudes, or by absolute altitudes with one or two repetitions. For this purpose there should be three or five horizontal wires, and the instrument should be previously carefully adjusted. The instrument must be moved in azimuth, so that the star passes each wire near the centre, and nothing should be touched which afi'ects the level. For illumination by night. there is an opening with a reflector in the centre of the telescope. This is objected to as weakening the telescope, but the other mode of illumi nating by a small central retlector, or outer ring in front of the object glass, is inconvenient. Perhaps by taking a longer hold of the telescope and strengthening the intervening portion of the tube, the former convenient arrangement may be preserved without sensible loss of strength. The repeating circle, on Borda's construction at least, cannot be well employed in observing the sun without very careful screening. The level is so perpetually changing its zero, when exposed to the sun, that there is no possibility of saying what the instrumental zenith is. Print Specifics: Type of print: Copperplate engraving - Original antique print Year of printing: not indicated in the print - actual: 1820 Publisher: Longman, Hurst, Rees, Orme Brown, London Condition: 1 (1. Excellent - 2. Very good - 3. Good - 4. Fair) Dimensions: 8 x 10.5 inches (20 x 25 cm), including blank margins (borders) around the image. Paper weight: 3 (1. Thick - 2. Heavier - 3. Medium heavy - 4. Slightly heavier - 5. Thin) Reverse side: Blank Notes: Green color around the print in the photo is a contrasting background on which the print was photographed. Martin2001 Satisfaction Guaranteed Policy! Any print purchased from me may be returned for any (or no) reason for a full refund including all postage. seller since 1998. Five-star service. Powered by Turbo Lister The free listing tool. List your items fast and easy and manage your active items.
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