1 2Once-Asked Questions 3==================== 4 5Q: I don't have *numpy*. What do I do? 6--------------------------------------- 7 8"import error: no module named numpy" 9 10A: Disable things that require numpy. 11------------------------------------- 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? 19------------------------------------------------------------- 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? 35------------------------------------------------------------------------------------------- 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? 54------------------------------------------------------------------------------------- 55 56A: Check out *plotann.py*, or try these older instructions... 57------------------------------------------------------------- 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? 77------------------------------------------ 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---------------------- 93 94 95 96 97