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Second astronomical image with an FPA

Submitter: Tom Oosterloo (for the APERTIF team)
Description: After reaching the important milestone of the first astronomical image, DIGESTIF continues to give exciting results. What is shown here, on the left, is the neutral hydrogen of the Andromeda nebula (aka M31), the twin brother of our own Milky Way. M31 extends several degrees on the sky and this is much larger than the Field of View of a WSRT dish (indicated by the white circle). However, using the focal-plane array of DIGESTIF to instantaneously make many beams on the sky, most of M31 can be detected in one single telescope pointing. The image on the left is the result of a single 6.7 sec observation.

The image on the right is also of the neutral hydrogen of M31, on the same scale as the picture on the left. It was made with the WSRT by Robert Braun some years ago. Some may say that this image is better because is shows much more detail. But that is because Robert cheated by using all 14 WSRT dishes and make a large mosaic of many aperture synthesis images and that took many weeks to complete. In doing so, he needed 163 different telescope pointings to scan the sky and to cover M31. If each WSRT dish would have a system like DIGESTIF, the picture on the right could have been made with a single observation.
Copyright: ASTRON
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