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- TABLE DES MATIÈRES
- TABLE DES ILLUSTRATIONS
- RECHERCHE DANS LE DOCUMENT
- TEXTE OCÉRISÉ
- Première image
- PAGE DE TITRE
- Preface to the third edition (p.R2)
- Contents (p.R3)
- Introduction (p.5)
- The various forms of telescopes. Their construction and advantages (p.7)
- Refracting telescopes (p.11)
- Stands for indirect-vision reflectors (p.31)
- Equatorial adjustments (p.41)
- To silver and polish glass specula (p.49)
- Apparatus (p.49)
- To support the Mirror in the Silvering Vessel (p.50)
- To clean the mirror (p.51)
- To immerse the mirror (p.51)
- To prepare the Silvered surface for polishing (p.52)
- To polish the Silvered surface (p.53)
- To separete the Mirror from the Wooden Support (p.54)
- Martin's process of silvering (p.54)
- Dr. Henry Draper's formula for silvering (p.56)
- The sugar of milk process for silvering (p.56)
- General, hints on silvering (p.57)
- Accessories to the telescope (p.58)
- Observatories (p.66)
- Defining and separating tests (p.78)
- Light tests (p.79)
- Catalogue of reflecting and retracting telescops and their accessories (p.81)
- Achromatic perspective glasses (p.81)
- Achromatic opera glasses (p.81)
- Achromatic field glasses (p.81)
- Achromatic telescopes (p.83)
- Horne and thornthwaite's binocular telescopes (p.83)
- Refracting telescopes for astronomical purposes (p.84)
- Astronomical object glasses (p.87)
- Astronomical reflecting telescopes (p.89)
- Silvered-glass specula (p.93)
- Silvered-glass diagonal mirrors (p.93)
- The “romsey” observatory (p.93)
- Silvering and polishing specula (p.94)
- Apparatus for silvering (p.94)
- Set of silvering apparatus (p.94)
- Astronomical eye pieces (p.95)
- Solar eye pieces (p.95)
- Micrometers (p.95)
- Astronomical spectroscopes (p.96)
- Trabsit instruments (p.96)
- Works on astronomy (p.96)
- Dernière image
- Première image
- PAGE DE TITRE
- The german equatorial stand (p.17)
- The victoria equatorial (p.18)
- The alt-azimuth stand (p.32)
- Horne and Thornthwaite's equatorial reflector (p.34)
- Horne and Thornthwaite's portable equatorial reflector (p.35)
- The berthon equatorial (p.38)
- The berton equatorial (p.39)
- The victoria equatorial telescope (p.85)
- Berthon patent equatorial stand (p.90)
- The alt-azimuth stand (p.92)
- Binoclar microscope (p.97)
- Dernière image
3°
A test as to the correctness of the adjustments A and C may be obtained thus: Place a very low power eye-piece in position and notice if the field appears uniformly brilliant; should one edge be shaded, it shows that the adjustments are not perfect, and they should be tested and made correct. Should, however, the eye-piece have a very large field, an even marginal shade may be seen, showing that the flat is not quite large enough for the illumination of that large field ; this would not interfere with good definition, the only disadvantage would be a slight loss of light with that power. On the other hand, a too large flat would also always occasion loss of light. In trying these experiments the telescope should be directed to a bright part of the sky.
The bulb of a thermometer illuminated by the sun, or on a dull day by any bright light, forms what is known as an“ artificial star,” and may be used during the day for delicate adjustments in place of a true star.
The cell mount of the large mirror can be removed from the tube and replaced without disturbing its adjustments, but it is very advantageous if the entire instrument can always be left undisturbed when not in use in an observatory of light construction, having a skeleton revolving dome, covered with well oiled canvas or calico, and made with a wide opening and large shutters, as described on page 66. Both the large and small mirrors should be protected by their covers (with which they are provided), when not in use, especially if left in the open air. The larger sized tubes' have a door large enough to admit the cover, and so allow of its being put on the large mirror without the necessity of the speculum being removed from the body of the telescope. We have lately introduced a screw movement for delicately revolving the flat mount.
Le texte affiché peut comporter un certain nombre d'erreurs. En effet, le mode texte de ce document a été généré de façon automatique par un programme de reconnaissance optique de caractères (OCR). Le taux de reconnaissance estimé pour cette page est de 99,78 %.
La langue de reconnaissance de l'OCR est l'Anglais.
A test as to the correctness of the adjustments A and C may be obtained thus: Place a very low power eye-piece in position and notice if the field appears uniformly brilliant; should one edge be shaded, it shows that the adjustments are not perfect, and they should be tested and made correct. Should, however, the eye-piece have a very large field, an even marginal shade may be seen, showing that the flat is not quite large enough for the illumination of that large field ; this would not interfere with good definition, the only disadvantage would be a slight loss of light with that power. On the other hand, a too large flat would also always occasion loss of light. In trying these experiments the telescope should be directed to a bright part of the sky.
The bulb of a thermometer illuminated by the sun, or on a dull day by any bright light, forms what is known as an“ artificial star,” and may be used during the day for delicate adjustments in place of a true star.
The cell mount of the large mirror can be removed from the tube and replaced without disturbing its adjustments, but it is very advantageous if the entire instrument can always be left undisturbed when not in use in an observatory of light construction, having a skeleton revolving dome, covered with well oiled canvas or calico, and made with a wide opening and large shutters, as described on page 66. Both the large and small mirrors should be protected by their covers (with which they are provided), when not in use, especially if left in the open air. The larger sized tubes' have a door large enough to admit the cover, and so allow of its being put on the large mirror without the necessity of the speculum being removed from the body of the telescope. We have lately introduced a screw movement for delicately revolving the flat mount.
Le texte affiché peut comporter un certain nombre d'erreurs. En effet, le mode texte de ce document a été généré de façon automatique par un programme de reconnaissance optique de caractères (OCR). Le taux de reconnaissance estimé pour cette page est de 99,78 %.
La langue de reconnaissance de l'OCR est l'Anglais.