Question

It is a cool day in Green Bank (5 deg C), and you are observing a point-source calibrator with the GBT that has a flux density of 1 Jy. However, you measure a flux density of only 800 mJy.

(a) (2 points) What is the observed atmospheric opacity, tA?

Answer 1

Answer on Question 55053, Physics / Astronomy | Astrophysics

Question:

It is a cool day in Green Bank (5 deg C), and you are observing a point-source calibrator with the GBT that has a flux density of 1 Jy. However, you measure a flux density of only 800 mJy.

(a) (2 points) What is the observed atmospheric opacity, $t_A$?

Solution:

$$\begin{array}{l} S_{\text{meas}} = \exp(-\tau_A) \times 1 \\ 0.8 = \exp(-\tau_A) \times 1 \\ \tau_A = -\log 0.8 = 0.22 \\ \end{array}$$

Answer: $t_A = 0.22$

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