Astro 506

Problem 1: To be handed in on Jan 22

Given, on Earth:

	U	V	I	K	 

	-5.71	-5.23	-4.55	-2.19	sky background (log(Jy/arcsec^2))

	0.15	0.16	0.19	0.23	delta-lambda/lambda (filter width)

	0.36	0.55	0.79	2.3	filter central wavelength (microns)

	1810	3640	2550	670	flux zeropoint (m=0) in the Johnson system
					(U=B=V=0 etc. for Vega) (Jy)

	27.5	29.0	28.25		AB mag limit for 10-sigma detection for the
					Hubble Deep Field (HDF)

Calculate:

1. AB magnitudes and Johnson magnitudes for the sky

2. sky photons/s-arcsec^2 for the HET (D=9m)

3. object photons/s for the HET for the 10-sigma AB mag limits for HDF

4. Assume S/N = [I / sqrt(B)] * sqrt(t), where t is observing time,
   I is the object flux, and B the sky flux. Calculate the time it will
   take to reach a S/N of 10 with the HET for the 10-sigma detection 
   limits of the HDF. Assume the object flux is all within 1
   arcsec^2. How does this compare this to the 44 hours being spent
   (per band) with the HST. How does this change if the object flux is 
   enclosed within 4 arcsec^2?  

5. Infer the sky backgrounds (in AB and Johnson magnitudes)
   in U, V, and I bands for the Hubble Space telescope (2.1m) given
   the 10-sigma limits and 44 hours of observing time.