[Aavso-photometry] The AAVSO Photometric All-Sky Survey (APASS)

[Arne Henden]

On Wed, Mar 4, 2009 at 6:55 PM, Tom Richards <tom at woodridgeobsy.org> wrote:
> I note you're using an ABG chip, which surprises me. Will this affect the
> linear-response region significantly and hence the mag range you are
> planning to cover?

The 16801, which is a non-ABG chip, is twice as expensive, so we compromised.
ABG has two main effects: you have lower QE & dynamic range because of
the extra real estate used by the ABG function, and you have the nonlinearity.
Nonlinearity can be handled, both through numeric processing and by reducing
the ADC range; I'm not too concerned about this.

The ABG function may actually be beneficial in the wide-field case because of
the chance occurrence of bright stars in the field that would otherwise bloom
and prevent measurement of dimmer stars in the vicinity.

But you are right - these cameras do have limitations, and careful calibration
will be necessary.  I expect to spend a couple of weeks in the lab at HQ before
sending them to New Mexico.
Arne