Subject: Re: jemx mosaics
 

Hi Simon,

> Hi - sorry to disturb you while you were away, I hope you had a nice
> trip !  I had a bit more of a think about this from my end:

No problem. Thank you for your extensive analysis of this issue.

>
>
> I understand about not wanting to renormalise the images, but for a
> different reason: to me it seems that there is something not right - the
> significance should simply be the flux measured, divided by the error on
> the flux (sqrt of the variance), it shouldn't need normalising if both
> of those are correct, the distribution should have a width of 1 sigma by
> definition.  The distribtion of the background significances should
> remain the same gaussian (mean of 0, std of 1 sigma, area of number of
> pixels in the image) although it should look smoother as exposure increases.

As I mentioned in my previous e-mail, we are aware about that, but we have not given it
a high priority so far. It may indeed be time now to find out what to do for the next
OSA release. However, this is not a trivial issue and it may have nothing to do with
the mosaicking but has its origin in j_ima_iros images. We need to seat and think this
over.

Unfortunately, this comes at a very bad time. I am in the middle of two proposals to
hire a PhD student and secure my own employment, while I need to find time to work on
PLANCK... So, I am afraid I will not be able to come back to you before a couple of
weeks or even before the AO-6 deadline.

Cheers,
                 Jérôme

--
Dr. Jérôme CHENEVEZ                 Institut for rumforskning og -teknologi
     DTU Space                      Juliane Maries Vej 30
National Space Institute            DK-2100 Copenhagen Ø
http://www.dsri.dk/~jerome          www.space.dtu.dk
Tel. +45 35 32 57 03                FAX: +45 35 36 24 75