[vsnet-chat 860] Re: PSF-fitting or aperture photometry (Richmond)

[Gianluca Masi <gianmasi@fr.flashnet.it>]

Taichi Kato wrote:

>    Intrapixel CCD response is not uniform (even for "astronomical" quiality
> ones).  Owners of CCD equipped with ABGs should extremely care for this,
> since ABG pattern on the CCD surface non-uniformly absorbs the light.
> Experiences with ABG-equipped CCDs and this small FHWM have shown up to
> 0.2 mag variation depending on the "intrapixel" location of the image
> center (even worse than visual estimates!).  FWHMs at least 3 pixels are
> recommended for more accurate photometry.

Do you think that maybe of some help, as regards the point above, to
have the telescope a _bit_ out of focus, to have a larger FWHM?

Best Regards,
Gianluca

-- 
***********************************************************************
* Gianluca Masi                           "Two things fill the soul   *
* Via Madonna de Loco, 47               with awe and reverence [...]: *
* 03023 Ceccano (FR)                     the starry sky above me and  *
* ITALY                                    the moral law within me"   * 
* email: gianmasi@fr.flashnet.it                                      *
* http://vsnet.eurolink.it/comets/                        I. Kant       *
***********************************************************************

VSNET Home Page

Return to Daisaku Nogami

---

vsnet-adm@kusastro.kyoto-u.ac.jp