Earthshine blog

Earthshine blog

"Earthshine blog"

A blog about a system to determine terrestrial albedo by earthshine observations. Feasible thanks to sheer determination.

Lamps on the Antenna

Exploring the PSFPosted by Peter Thejll Dec 29, 2011 03:19PM
As the night was fairly clear, I put the telescope on the lamps on the Antenna (Alt/Az: 21*34'/256*25').

As the several lamps on the Antenna seem distinct it is at least not an 'extremely foggy night'. I took V-band exposures at about 1 second.

Then I extracted the profile from the 25 coadded images. Only the quadrant below and to the right of the lower of the two sources above was used:

To about 20 pixels we see the actual lamp (i.e. the glass enclosure and filament). From about 30 pixels to short of 100 pixels we see the halo dropoff. The red line is a 1/r^(2.8) PSF.

This is contrary to what Chris found using the Moon and the occulting balcony! Unless the halo we see above is built up in the few hundred feet between the lamp and the telescope it must be due to the optics in the telescope. We cannot rule out that there was some fog, but the size of the exponent (2.8) indicates a 'clear night', I think - or is that circular thinking?

Anyway - it is not impossible that both optics and 'air' scatter in the same way.

Wonder if we can detect any examples where there is one halo from the optics and another from the atmosphere?

The above is not an occulting experiment.

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