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Earthshine blog

"Earthshine blog"

A blog about a telescopic system at the Mauna Loa Observatory on Hawaii to determine terrestrial albedo by earthshine observations. Feasible thanks to sheer determination.

JD2455836

Observing log Posted on Oct 02, 2011 08:56AM

Skyflats, Moon and Altair.

Skyflats started too late and are not well exposed – I started at 6:13, Sunset was close to 6:20 so should perhaps start closer to 6:00 next time.

Moon was run through various settings of SKEs and the KEDFs as well as the NDs – but images appear strange – as if the devices did not set right or the input data was wrong.

Altair was imaged through variable cloudiness allowing us to see both very clear PSFs and the misty PSFs.

The NAS was acting up – images were not being received on it. Had to reboot.



Altair maps the stellar psf!

Exploring the PSF Posted on Oct 02, 2011 08:23AM

We took a few hundred 0.4 second exposures of Altair, to measure the stellar PSF. Plot below shows Altair (green) versus our current best model (red) of the PSF based on fitting the moon. Note x axis is log(r/pixels).

The match is excellent, especially for the outer halo with its r^-3 powerlaw! Disagreement in the inner PSF (r<3 pixels, log(r)<0.5) is because Altair is very elliptical — so the radial PSF shown here has a lot of scatter. Note that this might be due to saturation/miscentering during the coadd – we’ll look at that.