Name:____________________________________________ Due Date:____________Score ________ / 40
Astronomy 480 - IRAF Tutorial for Exercise V
Introduction to PSF Fitting and DAOphot
1. <10 pts> After doing daoedit, fill in the following table with the values to use for daofind for 5 stars from each of the B and V images.
V filter |
x |
y |
Sky Mean |
Sky sigma |
FWHMpsf |
Counts |
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Averages: |
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B filter |
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Averages: |
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2. <5 pts> Edit datapars. Enter in this table both the values you got from your measurements and the values you actually used after you ran the tasks and saw the results (or after you compared your values to those in the listing linked from the course homepage and chose them). Remember: We are working with m920004 first and will come back to this table when you get to m920006.
V filter |
B filter |
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Your value |
Value used |
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Your value |
Value used |
fwhmpsf: |
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fwhmpsf: |
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sigma: |
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sigma: |
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datamin: |
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datamin: |
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datamax: |
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datamax: |
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3. <3 pts> What values do you think are appropriate for:
photpars.apertures: __________
fitskypars.annulus: __________
fitskypars.dannulus: __________
4. <2 pts> What values for the FWHM did psf determine? V filter __________ B filter __________
5. <5 pts> Compare the photometry in this exercise with those of IRAF IV for the following stars and comment on the results, giving explanations for any discrepancies (say, of 0.2 magnitudes or more):
Star ID
(IRAF IV)
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X
(approx)
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Y
(approx)
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V |
B |
IRAF IV |
IRAF V |
IRAF IV |
IRAF V |
6 |
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8 |
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13 |
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18 |
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20 |
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6. <2 pts> Run the match program so that you have 2 lists of stars: a list of those stars in the V filter that have matches in the B filter, and a list of those stars in the B filter that have matches in the V filter.
7. <3 pts> Create the color-magnitude diagram for your results using your favorite graphing program.
Show your graph to your instructor before printing. If your results are way off base, then you may have to go back, modify some of your parameters or check to make sure all parameters are set correctly (usually the problem), and redo the photometry. Once you have a CMD that you are satisfied with, print it and attach to this sheet.
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8. Here is a recently published CMD of M 92, with the major regions identified. Compare your overall results with this diagram by answering the following questions.
a. <1 pt> First, estimate on which part of the diagram the stars from this exercise lie. Indicate your guess clearly on this image. (It will help if you adjust the X- and Y-axis scales of your graph to match this figure.)
b. <2 pts> Second, there is, no doubt, an offset in V and in B-V between your CMD and this one. Why is this? (There is probably more than one reason.)
c. <2 pts> Why are there so many stars in this diagram that are scattered and do not lie on the main-sequence or the sub-giant, giant, or horizontal branches? |
9. <5 pts> Finally, using good writing style, summarize in general terms the full process you experienced here. Perhaps describe the problems you had and what you learned from your errors. Also, maybe include suggestions for future students of DAOphot.