Re: [TASS] Flat fielding

[Michael Gutzwiller <deepsky@FUSE.NET>]

In the IP package used by the star, etc programs, all images are converted
to floating point so no integer roundoff occurs.

A typical 8.5 magnitude star has a total ADU count of about 100,000 so the
0.035 floor is about 3,300 ADU's.  This is well out of any roundoff area and
is far and away larger than the calculaed  instrumental error of about 500
ADU's.

The floor remains anunresolved problem.

Mike G.


-----Original Message-----
From: Andrew Bennett <andrew.bennett@NS.SYMPATICO.CA>
To: TASS@LISTSERV.WWA.COM <TASS@LISTSERV.WWA.COM>
Date: Friday, September 10, 1999 11:08 AM
Subject: Re: Flat fielding


>On Thu, 9 Sep 1999 08:57:04 -0700, Chris Albertson <chrisja@JPS.NET> wrote:
>
>>Question:  Anyone know off hand the relationship
>>between ADU and magnitude for the Mk III.  I an
>>just wondering how many ADU = 0.05 magnitude for
>>a typical Mk III star
>The bright stars for which the 0.05 mags noise
>floor applies will be over 2,000 ADU so 0.05
>magnitude is over 100 ADU. Truncation errors
>with 16-bit arithmetic are entirely negligible
>unless one is doing the sums horribly wrong.
>Which has been known to happen (I am thinking
>of a professional image processing package somebody
>once tried to sell me) but surely not in TASS!
>
>Andrew Bennett, Avondale Vineyard, Nova Scotia, Canada.
>