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How close can ALMA observe to the Sun? - Knowledgebase / General ALMA Queries / The Sun - ALMA Science

How close can ALMA observe to the Sun?

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ALMA can actually point at the Sun. But, if the target is not the Sun itself, it is not advisable to point closer to the Sun than a couple of primary beamwidths from the solar photosphere to avoid a large amount of contamination in the observations.
This is because detectable solar emission is seen in the antenna sidelobes up to several degrees away from the Sun, although small grooves or etchings in the antenna surface are designed to ensure that sunlight is not reflected to the secondary subreflector.

Please see the ALMA Technical Handbook Chapter 8.10 for more information on solar observations.