Jaime Zamorano jaz at astrax.fis.ucm.es
Thu Sep 16 20:17:19 UTC 2010


This effect is real and you could measure it because your backyard is
inside a very dark and non light polluted area.

Regards, Jaime
  Jaime Zamorano                     E-MAIL: jaz at astrax.fis.ucm.es
  Dept. Astrofisica   Phone: 34-91 394 4590    FAX: 34-91 394 4635
  Fac CC Fisicas // Universidad Complutense // 28040 Madrid (Spain)
    http://guaix.fis.ucm.es/   - http://www.ucm.es/info/Astrof/
 Logics will get you from A to B,
 imagination will take you everywhere. (Albert Einstein)

On Thu, Sep 16, 2010 at 7:38 PM,  <JPDarkSkies at aol.com> wrote:
> re: Jaime.  Thanks for bringing this down to a realistic level as I feel
> that some of the quoted figures for dark sites are higher than I would
> expect.
> On the subject of cloud.  I am involved with a DS survey and I use my back
> garden as a starting calibration point before starting a survey trip.  I
> normally get a SQM-L reading of 21.4 but on one, only one, occasion I was
> getting varying readings up to 21.7.  I also noted very high tenuous cloud
> and assumed that there was a blanketing effect.  As I could make out the
> cloud I would have expected a lowering of the readings but possibly, I could
> not actually see the cloud but see the star background changing.
> Has anyone else seen this effect?  John P.
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