Off-disk straylight measurements for the Swedish 1-m Solar Telescope
Number of Authors: 1
2016 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 585, A140Article in journal (Refereed) Published
Context. Accurate photometry with ground-based solar telescopes requires characterization of straylight. Scattering in Earth's atmosphere and in the telescope optics are potentially significant sources of straylight, for which the point spread function (PSF) has wings that reach very far. This kind of straylight produces an aureola, extending several solar radii o ff the solar disk. Aims. We want to measure such straylight using the ordinary science instrumentation. Methods. We scanned the intensity on and far o ff the solar disk by use of the science cameras in several di ff erent wavelength bands on a day with low-dust conditions. We characterized the far wing straylight by fitting a model to the recorded intensities involving a multicomponent straylight PSF and the limb darkening of the disk. Results. The measured scattered light adds an approximately constant fraction of the local granulation intensity to science images at any position on the disk. The fraction varied over the day but never exceeded a few percent. The PSFs have weak tails that extend to several solar radii, but most of the scattered light originates within similar to 1'. Conclusions. Far-wing scattered light contributes only a small amount of straylight in SST data. Other sources of straylight are primarily responsible for the reduced contrast in SST images.
Place, publisher, year, edition, pages
2016. Vol. 585, A140
instrumentation: miscellaneous, methods: observational, methods: data analysis, techniques: photometric
IdentifiersURN: urn:nbn:se:su:diva-127891DOI: 10.1051/0004-6361/201527137ISI: 000369710300147OAI: oai:DiVA.org:su-127891DiVA: diva2:940163