Twin Telescope observations of the Sun at Kodaikanal Observatory

TL;DR

The paper details the design, implementation, and initial results of a twin telescope at Kodaikanal Observatory for high-cadence solar observations, enhancing long-term solar activity monitoring.

Contribution

It introduces a novel twin telescope system capable of simultaneous Ca-K line and continuum imaging, improving solar observation capabilities since 2008.

Findings

Network element covers about 30% of the solar disk.

Network element area index varies marginally with seeing conditions.

Telescope achieves 5-minute cadence for regular observations.

Abstract

We report the design, fabrication and installation of a 'Twin Telescope' at Kodaikanal Observatory intended to augment the ongoing synoptic observations of the Sun that has been carried out since 1904. The telescope uses a 15 cm objective capable of taking Ca-K line filtergrams and photoheliograms in continuum of the full disk of the Sun simultaneously, at a frequency of 0.1 Hz using 2kx2k format CCD cameras. The telescope has been in operation since February 2008 and images are being obtained at a cadence of 5 min during normal observing periods. In case of solar activity, images of the active regions can be taken at a frequency of 1 Hz by restricting the field of view and spatial resolution. In this paper, we describe the telescope, instruments, image acquisition, data calibration and image processing. We also discussed a method of determining the network element and plage area index. The preliminary results show that while the network element covers about 30% of the disk, the percentage of the network element area index varies marginally with the seeing conditions during the day.