Solar Physics

, Volume 234, Issue 1, pp 187–201

Mercury Transit for Stray Light Evaluation: IPM-THEMIS Case


DOI: 10.1007/s11207-006-0033-5

Cite this article as:
Briand, C., Mattig, W., Ceppatelli, G. et al. Sol Phys (2006) 234: 187. doi:10.1007/s11207-006-0033-5


Mercury's transit on the solar disk offers ideal conditions to determine the stray light level of instruments. We present here the results on the stray light level deduced from the observation of the Mercury transit on 2003 May 7th at the secondary focus of the THEMIS telescope with the broad-band and spectral channels of the IPM instrument. The scattered light in the broad-band channel is about 17% and about 25% in the spectral channel. The spread function was deduced for the two channels taking into account the observations on the limb and on Mercury's disk.

The goal of this paper is to underline the limits of determining the spread function from limb measurements to correct disk observations. Indeed, we show that if a diaphragm is located in the optical path of scattering surfaces, then the spread function deduced from limb measurements can be underestimated compared to the one required for disk observations. The case is illustrated with the results of the IPM-THEMIS instrument. The spread function deduced from limb measurements is able to correct disk observations in the broad-band channel but not in the spectral channel, even if the two channels are illuminated through the same telescope configuration.

Copyright information

© Springer Science + Business Media, Inc. 2006

Authors and Affiliations

  • C. Briand
    • 1
  • W. Mattig
    • 2
  • G. Ceppatelli
    • 3
    • 4
  • G. Mainella
    • 5
  1. 1.LESIAObservatoire de ParisMeudon CEDEX PrincipalFrance
  2. 2.Kiepenheuer-Institut für SonnenphysikFreiburgGermany
  3. 3.IACLa Laguna TenerifeSpain
  4. 4.On Leave from INAF-Osservatorio di ArcetriFirenzeItaly
  5. 5.Fundación Galileo Galilei – INAFSanta Cruz de La PalmaSpain

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