# The solar survey at Pic du Midi: calibrated data and improved images

## TL;DR

This paper presents the calibration, improved imaging techniques, and public data release of the CLIMSO solar survey at Pic du Midi, covering multiple spectral lines and nearly a full solar cycle.

## Contribution

It introduces enhanced contrast coronagraphs, an autoguiding system, and calibrated, science-ready data for solar research, expanding the survey's capabilities and accessibility.

## Key findings

- Calibrated spectral radiance maps for H-alpha and Ca II channels.
- Improved contrast in coronagraph images of the Fe XIII corona.
- Public availability of high-quality, calibrated solar images and movies.

## Abstract

At Pic du Midi observatory we carry out a solar survey with images of the photosphere, prominences and corona. This survey, named CLIMSO (CLIch\'es Multiples du SOleil), is in the following spectral lines: Fe XIII corona (1.075 micron), H-alpha (656.3 nm) and He I (1.083 micron) prominences, H-alpha and Ca II (393.4 nm) photosphere. All frames cover 1.3 times the diameter of the Sun with an angular resolution approaching one arc second. The frame rate is one per minute per channel (weather permitting) for the prominences and chromosphere, and one per hour for the Fe XIII corona. This survey started in 2007 for the disk and prominences, and in 2015 for the corona. We have almost completed one solar cycle, and hope to cover several more, keeping the same wavelengths or adding others. Aims: Make the CLIMSO images easier to use and more profitable for the scientific community. Methods: Providing 'science-ready' data. We have improved the contrast capabilities of our coronagraphs, which now provide images of the Fe XIII corona, in addition to the previous spectral channels. We have also implemented an autoguiding system based on a diffractive Fresnel array for precise positioning of the Sun behind the coronagraphic masks. Results: The data (images and films) are publicly available and downloadable through virtual observatories and dedicated sites: e.g. http://climso.irap.omp.eu. For the H-alpha and and Ca II channels we calibrate the data into physical units, independent of atmospheric or instrumental conditions: we provide solar maps of spectral radiances inW m^-2 sr^-1 nm^-1. The instrumental improvements and the calibration process are presented in this paper.