Details of exhibit
- Exhibition:
- 1908 Fifty-third Annual Exhibition of the Royal Photographic Society of Great Britain
- Exhibit title:
- Sun, August, 1908
- Exhibitor:
- C. W. Barlow
- Section:
- Lantern Slides
- Group Title:
- Set of 11 Slides
- Exhibit No.:
- 518
- Description:
- The points of technical and scientific interest are:-
1. The photographs are taken with a 4¼-inch astronomical refractor, the object glass of which is about 100 years old, and not specially corrected for photographic work. The light has been rendered nearly monochromatic by the insertion between eyepiece and sensitive plate of deep yellow isochromatic screens. The negatives are on ordinary gelatine bromide lantern plates, the exposure being made by a diaphragm shutter, and varying from 1/50th to 1/150th second approximately.
2. The special adaptability of the process of carbon transparency for this and all other scientific work where the exact gradation of the negative is required in the print. All except Nos. 1, 4, 5 and 11, are printed by this method, with the result that the delicate granulation of the solar surface is retained even in the centre of the disc, while the tint is not too dark, and the gradual falling off of the emissive power from centre to edge is correctly represented.
3. Some of the largest, and most interesting sunspots of recent years are shown. The very regular S-shaped spot in No. 2 is very rare. No. 9 shows one of the largest spots that have ever been seen on the sun. Another spiral spot is shown in No. 10, where the umbra is S-shaped. No. 4 shows well the granulation of the solar surface, and the structure of the bright faculę. No. 11 shows a fine collection of spots which are very large, considering that the solar cycle is now well-advanced towards the minimum. - Exhibit type:
- Photographic equipment and supplies
- Process:
- [Not Listed] ()
- Award:
- none
