Discussion on beams

We measure the beam by using the middle scan of the 3-scans sequence launched with @beammap Here are the best-of on 3 sources.

Preliminary findings

The main beam (the Gaussian part) seems with a normal width aka 11", 17".
The quadrupod holding the secondary gives clear diffraction marks as a faint cross visible in all scans.
In between, there is a large near-side lobe, especially at 2mm (but also visible at 1mm), that shows up as a rectangular pyramid-like shape at the 10% level, the origin of which is unknown. It seems to scale with wavelength. It was not so apparent in NIKA. Therefore the quality of the dichroic is not at the center of this issue.
For comparison, see the NIKA-1 beam maps in Fig.8 of Catalano+2014 and in Fig.8 of Monfardini+2011.

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- * For comparison, see the NIKA-1 beam maps in Fig.8 of [[http://www.aanda.org/articles/aa/pdf/2014/09/aa23557-14.pdf|Catalano+2014]]) and in Fig.8 of [[http://iopscience.iop.org/article/10.1088/0067-0049/194/2/24/pdf|Monfardini+2011]].
+ * For comparison, see the NIKA-1 beam maps in Fig.8 of [[http://www.aanda.org/articles/aa/pdf/2014/09/aa23557-14.pdf|Catalano+2014]] and in Fig.8 of [[http://iopscience.iop.org/article/10.1088/0067-0049/194/2/24/pdf|Monfardini+2011]].