1
2Once-Asked Questions
3====================
4
5Q: I don't have *numpy*.  What do I do?
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7
8"import error: no module named numpy"
9
10A: Disable things that require numpy.
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12
13Some parts of the code need the "numpy" python package.  To disable things that need numpy::
14
15    solve-field --no-remove-lines --uniformize 0  [....usual arguments...]
16
17
18Q: Is there a way to plot a grid of RA and Dec on the images?
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20
21A: Yes
22------
23
24You'll have to run the "plot-constellations" program
25separately.  For example, if you have an image 1.jpg and WCS 1.wcs:
26
27    jpegtopnm 1.jpg | plot-constellations -w 1.wcs -o grid.png -i - -N -C -G 60
28
29will plot an RA,Dec grid with 60-arcminute spacings.  Unfortunately
30they're not labelled...
31
32[Note, see *plotann.py* also for more annotation options.]
33
34Q: Is there a way to get out the center of the image (RA,Dec) and pixel scale of the image?
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36
37A: Yes, with the *wcsinfo* program
38----------------------------------
39
40Yes, run the "wcsinfo" program on a WCS file -- it prints out a bunch
41of stats, in a form that's meant to be easy to parse by programs (so
42it's not particularly friendly for people).  "ra_center" and
43"dec_center" (in degrees) and "pixscale" (in arcsec/pixel) are what
44you want.
45
46Q: Is there a way to plot N and E vectors on the image?
47-------------------------------------------------------
48
49A: Not yet.
50-----------
51
52
53Q: Is there a way to plot a list of your own objects on the image by inputing RA,Dec?
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55
56A: Check out *plotann.py*, or try these older instructions...
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58
59Yes -- but it's roundabout...
60
61First, project your RA,Dec objects into pixel x,y positions:
62
63    wcs-rd2xy -w 1.wcs -i your-objs.rd -o your-objs.xy
64
65Then plot them over the image (or annotated image).  There's not
66currently a way to label them.
67
68:
69
70    pngtopnm grid.png | plotxy -i your-objs.xy -I - -x 1 -y 1 -s X -C green -b black > objs.png
71
72The "-x 1 -y 1" compensate for the fact that FITS calls the center of
73the first pixel (1,1) rather than (0,0).
74
75
76Q: Would your code work on all-sky images?
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78
79A: Not very well
80----------------
81
82We assume a TAN projection, so all-sky images typically don't work,
83but it should certainly be possible with a bit of tweaking, since
84all-sky is really a much easier recognition problem!  One thing you
85can try, if your image is big enough, is to cut out a small section
86near the middle.
87
88Q: I want to build an index from my own catalog.  How do I proceed?
89-------------------------------------------------------------------
90
91A: See :ref:`genindex`
92----------------------
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97