Subject: Re: observing in Moon nights

From: richard mcmahon at IOA <[email-masked]>
Date: Sun, 16 Jun 2002 16:50:18 +0100 (BST)

I would stay at least 30degrees; ie. around 2hrs in RA away from the
moon. By now it is probably to bright to observe in g when the moon is
up. You need to increase the exposure times when the sky is bright as
follows:

* Exposure times in moonlight
* Formally the exposure time needs to be increased linearly with sky
brightness if you want to attain a uniform limiting magnitude.
* Take action if the sky goes more 25% above the values above by making
exposure time 50% longer. [this will overcompensate but it avoids
human errors which occur when observers try to micro-manage the
expsoure times.

* When the sky brightness reaches 50% above the above double the nominal
exposure.

* Donot go more than x2 on the nominal exposure times since then the
survey speed drops. It is probably better do a redder band or move further
from the moon.

Note the sky value you measure on the screen includes bias level
so you need to subtract this.

r.

On Sun, 16 Jun 2002, Weimin Yuan wrote:

> Date: Sun, 16 Jun 2002 04:59:26 +0100 (BST)
> From: Weimin Yuan <[email-masked]>
> To: Richard McMahon <[email-masked]>
> Cc: Mike Watson <[email-masked]>, Jonathan Tedds <[email-masked]>
> Subject: observing in Moon nights
>
> Hi Richard,
>
> We are now approaching to the bright Moon nights.
> Is there any minimal angle at which we should keep the
> telescope away from the Moon? (Moon phase dependent?).
> We'd take this into account when planning the observations.
> regards
> Weimin
>

--------------------------------------------------------------------------
 Dr. Richard G. McMahon    | Phone (office)     44-(0)-1223-337519
 University of Cambridge   |       (switchboard)       1223-337548
 Institute of Astronomy    |       (secretary)         1223-337516
 Madingley Rd              | FAX                       1223-337523
 Cambridge, CB3 OHA, UK.   | mobile                (0)-7885-409019
 office: Hoyle 8           | home                      1223-464920

---------------------------------------------------------------------------
email: [email-masked]         | WWW:  http://www.ast.cam.ac.uk/~rgm
---------------------------------------------------------------------------