Stray-light effect on magnetograph observations

Document Type

Article

Publication Date

1-1-1998

Abstract

To examine the stray-light effect in magnetograph observations, we have determined the point spread functions of the vector magnetograph mounted on the Japanese Solar Flare Telescope based on two indirect methods, one analyzing the solar limb intensity profile, and the other using the Fourier power spectra of photospheric intensity distributions. Point spread functions consist of two parts: a blurring part which describes seeing and small-spread-angle stray light, and a scattering part which describes large-spread-angle stray light. The FWHM spatial resolution is typically 3.0″, and the amount of scattered light is about 15% on clear days. We find that the blurring part is well described by a Moffat function whose Fourier transform is given by an exponential function. Our results indicate that polarization measurements of low-intensity magnetic elements like sunspots may be significantly underestimated due to the large-spread-angle stray light, and polarization measurements of magnetic elements which are smaller than 5-7″ appear to be disturbed by small-spread-angle stray light.

Identifier

0042224517 (Scopus)

Publication Title

Solar Physics

External Full Text Location

https://doi.org/10.1023/A:1005012509071

ISSN

00380938

First Page

229

Last Page

244

Issue

2

Volume

183

Grant

966–0203–6056

Fund Ref

National Science Foundation

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