Question

1. A star is being observed with an 8 bit CCD has a central pixel value of 82 counts when the exposure time is 10 seconds. What would the central pixel value be if the exposure time were 25 seconds? Explain your reasoning.

   		The central pixel value would be about 82 counts since the detector is linear.
   		The central pixel value would be about 205 counts since the detector is linear.
   		The central pixel value would be about 305 counts since the detector is linear.
   		The central pixel value would be about 159 counts since the detector is linear.

2. A 12-bit CCD collects light from a star over a 10 second exposure and obtains a central pixel value of 1068. What is the longest exposure that could be taken of this star and still avoid saturation? Explain your reasoning.

   		A. The longest exposure is about 39 seconds since the detector is linear and will saturate at 4095 counts.
   		B. The longest exposure is about 38 seconds since the detector is linear and will saturate at 4095 counts.
   		C. The longest exposure is about 40 seconds since the detector is linear and will saturate at 4095 counts.
   		D. The longest exposure is about 37 seconds since the detector is linear and will saturate at 4095 counts.

3. Choose the table which most closely agrees with your answer for the followig question:

   Enter the offsets you obtained for starfield 2 and starfield 3 in the table below.

   		X Offset Y Offset Starfield 2 -35 29 Starfield 3 -14 -20
   		X Offset Y Offset Starfield 2 -35 37 Starfield 3 -14 -20
   		X Offset Y Offset Starfield 2 -14 -20 Starfield 3 -34 30
   		X Offset Y Offset Starfield 2 -35 29 Starfield 3 -18 -15

4. Choose the table below which most closely agrees with your answer for Question 7 of the lab.

   The starfields of the blink comparator contain 5 variable stars. Create different blinking sequences in the simulator to identify the variables and record the x and y locations of the variables on this starfield. One variable star has already been located for you. Note that the coordinates do not need to be exact, you just need to be able to find the stars again in the next simulator

   		X coordinate Y coordinate Variable #1 64 114 Variable #2 24 260 Variable #3 131 201 Variable #4 309 177 Variable #5 331 22
   		X coordinate Y coordinate Variable #1 64 114 Variable #2 124 260 Variable #3 131 201 Variable #4 309 177 Variable #5 331 22
   		X coordinate Y coordinate Variable #1 64 114 Variable #2 124 260 Variable #3 131 201 Variable #4 309 177 Variable #5 350 122

5. Decide if the following answer is true or false for the question:

   Hypothetically, suppose that you add a long series of observations all taken one day apart to the blinking queue. Would you be able to detect large amplitude variable stars with periods of a) 1.0 days, b) 0.5 days, or c) 0.75 days?

   Answer:

   If the observations are taken 1 day apart then you will not see large amplitude variable stars with periods of 1.0 day or 0.5 days because after one day both types of stars will be in the same phase on each day of observation.

   If the star has a period of 0.75 days then the phase will not be the same after one day. A period of 0.75 days is 18 hours. Suppose on the first day the phase of the star is 0. After 18 hours the phase will again be 0 so after 6 more hours the phase will now be 0.33 or 6/18 = 1/3 of a cycle.   On day 2 we have: after another 18 hours the phase will again be 0.33 so after another 6 hours the phase will advance another 1/3 cycle so the phase is 0.67. On day 3 the phase will be back to 0.

   Another way of looking at this is to consider when the phase will be 0; it will be zero after 18 hours, 36 hours, 54 hours and 72 hours, So if we observer each 24 hours then the phase will not be zero again during our observation until after three days.

   True

   False

6. What is the range of pixel values inside the inner circle for this star? (Find the maximum and minimum values.

   		Pixel Values Minimum 1633 Maximum 31495
   		Pixel Values Minimum 16330 Maximum 31495
   		Pixel Values Minimum 16330 Maximum 17865

Answer 1