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This fond contains official letters, photographs, and administrative files related to P. R. Chidambara Ayer during the years 1919-1932.

These photographic slides contain the images of the spectrometer, and Ondrej telescope related to the Optical Science Department of Royal Observatory, Edinburgh.

This font is regarding public works in Kodaikanal Observatory

This font is regarding Instruments used in Kodaikanal Observatory

This fond contains collection of items that provide information about solar eclipses that occurred during the time period of 1868-2006. The collection includes photographs of total solar eclipses that took place on different dates, and covered from different places as well as sketches that help to illustrate the phenomenon and the path of the eclipses.

This item was about the photograph of granite pillar in meteorology department compound at Nungampakkam, Chennai as seen today. In the compound of the Meteorology Department in Chennai, there is a 15-foot tall granite pillar weighing 10 tons. This granite pillar is part of the Regional Meteorological Centre in Chennai and is preserved as a monument. This is the place where Madras Observatory was existed.

The fond contain compilation of Pogson's observations and drawing

The item is a 6 inch transit circle. The transit circle is an instrument used to determine the declination of stellar onjects. It consists of a circular scale kept perpendicular to the rotating axis of a telescope tube.

This item was a optical instrument named as Stereoscope. Stereoscopes are apparently those optical devices that help to view the two images separately and with relaxed eyes. There are two types of stereoscopes as: lens or pocket stereoscopes and mirror stereoscopes. Lens or pocket stereoscopes are great for viewing the whole overlap area of prints up to 9 cm × 13 cm or parts of larger patterns. On the other hand, mirror stereoscopes were designed to accept standard 23 cm × 23 cm metric air photos and work well with A4/US letter-sized prints. Most models come with magnifying options up to eight times, which is pretty impressive. One cool thing about mirror stereoscopes is that they are large enough to allow the analyst to draw beneath them, so it is possible to trace objects identified in the stereoview with a pen onto one of the images or a transparent overlay. However, it's important to remember that this sketch wouldn't have the geometric properties of a map as it contains all distortions present in the base image.

This item was an instrument used for measuring the intensity of a light source. It uses a light-sensing device that is calibrated to express intensity in a standard unit. Some optical elements such as lens etc. are also employed to incerase the sensitivity of the instrument.