ASTR 597: Assignments

Spring Term, 2011

Assignment Due Date
Find the Brewster angle for a dielectric interface as a function of refractive index, n. Draw the corresponding picture that elucidates why this angle is special (all about the electron wiggle direction within the medium). Evaluate for air-glass interface. Monday, April 4
Using a thin-lens approximation for the APO 3.5 m telescope, determine how much the focus shifts for a 1 mm shift in the distance between the secondary and primary mirrors. Using this scaling, and the fact that the beam is f/10, how much does the secondary mirror have to move to introduce one arcsecond (170 μm) blur at the focal plane? Parameters for the scope: f1 = 6.12 m, f2 = −1.60 m, d12 = 4.8 m, s = f1d12 = −1.32 m, so that s′ works out to 7.543 m. Wednesday, April 13
Skim either the 2D-raytrace and/or the 3D-raytrace documents to get a heads-up on what's coming. We'll spend significant time raytracing, so understanding what's in the box will be helpful. Monday, April 18
Go ahead and play around with the 2-d raytracing stuff, if you are motivated. Here is the portal. whenever
Come up with a design that would let the venerable Palomar 200-inch telescope operate at f/15. The primary is 5.08 m in diameter and forms a prime focus at f/3.3. The Cassegrain focus forms approximately 2 meters behind the primary mirror. Work out all the numbers: f2 of the secondary mirror, the image and object distances relative to the secondary mirror (distance from prime focus; distance to telescope focus), d12, and the minimum diameter the secondary needs to be. What is the radius of curvature of the secondary mirror? Also present the plate scale at the Cassegrain focus in useful units, and what this would mean for a 4k by 4k CCD imager with 25 micron pixels, in terms of field of view, arcseconds per pixel, etc. Monday, April 18
Come up to speed on the 2-d raytracing program. Pick one of the investigations on the raytracing page for submission as your homework problem. The goal is to do just enough that you have gotten over the hurdle of using it and know how to interpret the output, so we can do examples in class without your being lost. In terms of what to turn in: a description of your investigation that shows me that A) you successfully ran the program, and B) you understood the output and learned something from it. Friday, April 22, by lunchtime
Review the 3D raytracing page and pick a task from the topics page, which may evolve over time. You will then present findings to the class. Week of April 25
Compute how long one would have to integrate to get a signal-to-noise ratio of 10.0 on a magnitude 22.5 source in each of the Sloan bands on SPIcam. Assume the seeing has a sigma of 1.5 (2×2 binned) pixels, and take the flux within a 2-sigma radius. Use the numbers on the slide labeled as number 43 in the SPIcam talk. Assume a read noise of 5.7 electrons. The sky numbers represent the number of photo-electrons in a 2×2 binned pixel, and all numbers are in electrons. Assume that the star flux is 100% of the flux captured by the CCD for a magnitude 20 source. Mon., May 9
IR Camera "Lab": Team up with a partner and check out the IR camera from me. I will be away Friday, May 13, and possibly Thursday afternoon as well. Following ideas and relations set out on the handout, perform an experiment with the IR camera. You could measure the emissivity of glass, of something shiny (and flat; but not behind glass like a bathroom mirror), or see how much tarnishing or fingerprints, etc. impact emissivity. You might find some decent metal scraps in the machine shop in the basement. You could attempt to measure the effective clear sky temperature (if blue). You could have some even better ideas, or come across something in your exploration with the camera that you get excited about and could turn into a useful/informative assignment. Fri., May 20, by pizza time
Build a cardboard tube spectrometer, using the slide-mounted grating handed out in class. The assignment is to: 1) explain clearly based on your own experience with the grating why we typically want a slit in spectroscopy; 2) estimate the angle to some particular wavelength and use this to determine the line spacing, a, expressed as the inverse, in lines per millimeter; 3) let me know what was the coolest, most informative thing you saw/experienced from use of the grating. Fri., May 27, by pizza time
Wavefront/Speckle Exploration: Use the wavefront simulation software, either in Python or IDL to generate simulated speckle point spread functions. There are many lines of inquiry that might be explored. See these instructions to access the code and to understand what the it does, along with some ideas for exploration (or can make up your own). Fri., June 3, in afternoon session

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