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Note that these value differ significantly from the canonical values posted on CFHT Web pages. The main differences are due to variations of the sky brigthness with Moon phase for u* and g’, and variations of the sky brightness with airmass for the redder filters (r’, i’ and z’). Finally, these values are subject to changes with the evolution of the baffling of the telescope. ## Expected depth of the observations already acquired :The expected limiting magnitudes were computed by using the MegaCam exposure time Calculator DIET under the following assumptions : seeing value of 0.8", point source, SNR = 5 computed in an aperture of 1.45*seeing=1.15".
In addition, in the SNR calculation, the sky term is multiplied by a factor n to take into account some additional noise in the sky subtraction or residuals due to crowding or systematics. n can range from 1 for a perfect sky substraction to 2 for a 1-1 pixel type subtraction. in DIET a value of n=1.5 isued. Limiting magnitudes (AB mags.) are given both for a point source, and a "galaxy" as defined in DIET : a distant and compact source, with a seeing-dominated profile. There is a difference of 0.7 magnitudes between them under the present assumptions.
## Details of the observations## Extinction map of D1 (Schlegel dust map)## DSS image of D1. Overlayed are the stars (R<14) from the USNO catalogue
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