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missed star.png (23,740 bytes) missed star 3.png (27,435 bytes) missed star 2.png (28,130 bytes) |
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I did some testing. It is a rounding and accuracy problem. By being very strict against double detection's it is missing the star on the edge/boundary. The problem is that the double detection doesn't use historical detection information but exclude any star outside the detection box. Making the double detection a little less strict solves the problem but introduces a few double detections in crowded star fields. The detection box has to be exact positioned or historical star detection needs to be used. It also possible that getHFD2 gives a tiny different star position depending on the test box placement. |
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The modification below will allow detection of all stars but give a few double detections in crowded fields. For a perfect detection I would implement a second image array where you mark the found star position area's and use this to exclude new stars. This is easy to implement. if ((hfd1>0)and(Undersampled or (hfd1>0.8))) and (hfd1<99) and (xc>=-0.5+(fitsX-(s div 2))) and (yc>=-0.5+(fitsY-(s div 2))) {prevent double detections in overlap area} and (xc<+0.5+(fitsX+(s div 2))) and (yc<+0.5+(fitsY+(s div 2))) and (vmax>treshold) and (vmax<(MaxADU-2*bg)) {new bright star but not saturated} then |
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Thank you, this look good, the 0.5 tolerance avoid to miss a star and the array prevent a double detection. I use what you do in ASTAP to implement the array. This is in: https://github.com/pchev/ccdciel/commit/4eb49a8a11286b1f98ef3e054aa89984bfc92102 |
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The code can be simplified. See below. The two lines containing the xc and yc conditions are redundant. In fact some more stars are detected. The star box size is less critical. My old value of 120 now works also. I also noticed a smaller value for size:=round(2*hfd1); That works fine. I used a little more conservative value of 3*hfd1. See no difference. So this works perfect. I'm impressed again by the performance. All problems solved. :) {check valid hfd } if ((hfd1>0)and(Undersampled or (hfd1>0.8))) and (hfd1<99) and (img_temp[0,round(xc),round(yc)]=0) {area not surveyed} // and (xc>=(-0.5+fitsX-(s div 2))) and (yc>=(-0.5+fitsY-(s div 2))) {exclude overlap area} // and (xc<(0.5+fitsX+(s div 2))) and (yc<(0.5+fitsY+(s div 2))) and (vmax>treshold) and (vmax<(MaxADU-2*bg)) {new bright star but not saturated} then |
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I let this test with xc and yc to avoid to keep a measurement in the overlap area from a star disk truncated at the boundary. But after testing this can be removed as you suggest because this truncated measurement are already rejected by the asymmetry test. I change to 2*hfd1 (used as a radius, so marking a area 4xhfd1) for big defocused stars to avoid to exclude a too large area around this stars. The change is in https://github.com/pchev/ccdciel/commit/3a618eb9cf23bb73096e570df9eb04295262d7e8 And I think this issue can be closed. |
- Anonymous
