Subject: Yet another measure of the DSC performance

From: Nan Ellman

Submitted: Wed, 06 Sep 1995 22:59:41 EDT

Message number: 4 (previous: 3, next: 5 up: Index)

To try and pin down the cause of the discrepancy between Michael's S/N
calculations and his limiting magnitude, I matched stars from the
Koo-Kron photographic catalog to objects detected in one of the SA57
scans. I found that 

1. S/N ~10 at F= 20, in agreement with Michael's revised estimate

2. S/N began dropping below 3  at F ~21

3. At  21 < F <= 22, photo found 41% of the objects (with consistent
flux measurements) 

4. At 20 < F <= 21, photo found 95% of the objects.

5. Fainter than F=22, there were no reliable matches.

6. Overall, for F <= 22, the completeness was 80%

These numbers are consistent with Michael's estimate of S/N and
expected detection rate for *point* sources. I believe the catalog he
used contained both galaxies and stars without any
classifications. The inclusion of galaxies probably explains the lower
completeness.

If people are interested, I can make my plots available on the web.

    Nan
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