Quality of SDSS coverage (including 'holes')

The following is a reference note on quality of fields, including hole fields in the SDSS data set.

Since DR4, the CAS has a field quality table, called RunQA, which provides information relevant to the average data quality for the objects in each field of SDSS. In DR5, there is also a TargRunQA table for the 'target' data. In the CAS, an SQL query such as 'select top 10 * from RunQA' will show sample entries for this table. This table may be joined to rest of your query to sub-select only fields of the very highest quality, for instance, with seeing below a certain threshold, if that is desired.

If you wish just one number which describes the overall quality of a field, we recommend you look at the FieldQall number (0=bad, 1=acceptable, 2=good, 3=excellent).

This overall quality determination, FieldQAll, is based on the (dereddened) principal colors of all the stars in the field vs. the Galactic value of this quantity, the PSF quality, the difference between Aperture and PSF magnitudes for the same stars in the field, and the seeing.

Principal colors of stars are linear combinations of the SDSS colors u-g, g-r, r-i, i-z which align perpendicular to the stellar locus of stars with F thru K spectral types. The position of the locus in color space of the Milky Way's stars (suitablely dereddened), does not appear to change by more than 1% or so toward most high latitude lines of sight, and so, assuming this locus to be fixed, the value of the principal colors is then an excellent measure of the absolute photometric calibration of the data.

A shift of more than about 1% from the cosmic (Milky Way) values of the colors perpendicular to the stellar locus indicates a possible mis-calibration of the data.

The width of the stellar locus in principal value colors is also a good indication of the quality of the data, in particular of the relative photometry of stars.

The individual principal colors (averaged over the field, along with rms widths of the distribution), are available in this runQA table, along with Aperture-PSF magnitudes and widths.

The information in the RunQA table is as follows:

Column of RunQA table:  Description
==================================================

 FieldID:  64-bit unique fieldID identifier f(skyversion,firstfield?,run,rerun,camcol,field)

 skyVersion: 0=target, 1=best, the DR5 CAS contains both a runQA table
                               for the 'best' skyVersion and a
                               TargRunQA table for 'target'

 First:  is this field the first in a segment?  0=no 1=yes

 Run: 	Run number

 Rerun:  Rerun processing number

 CamCol: Camera Col 1-6

 Field:  Field within a run

 FieldQAll:  Overall Field Quality measure:  0=BAD, 1=ACCEPTABLE, 2=GOOD, 3=EXCELLENT

 OPDBQ:      Operations Database quality measure:  0=UNDETERMINDED, 1=BAD, 2=ACCEPTABLE, 3=GOOD, 4=MISSING (unused),
				 5=HOLE

 APPSFQ:  Aperture magnitude - PSF magnitude difference quality measure: 1=GOOD 0=BAD
 PCMEDQ:  Principal color analysis median shift from nominal cosmic (Galactic) value: 1=GOOD, 0=shift too big
 PCRMSQ:  Principal color analysis RMS spread in colors vs. nomial: 1=GOOD, 0=Spread too big
 PSFWCONDQ: PSF width quality: 1=GOOD, 0=BAD 

 PC_S:    average principal color s=-0.249u+0.794g-0.555r+0.234 for stars in field.
 PC_W:    average principal color w=-0.227g+0.792r-0.567i+0.05 for stars in field.
 PC_X:    average principal color x=0.707g-0.707r-0.988 for stars in field
 PC_Y:    average principal color y=-0.27r+0.8i-0.534z+0.054 for stars in field.
		 Where u,g,r,i,z are the dereddened PSF magnitudes of the stars in SDSS filters.

 rmsPC_s: rms width of the s color (mags)
 rmsPC_w: rms width of the w color (mags)
 rmsPC_x: rms width of the x color (mags)
 rmsPC_y: rms width of the y color (mags)

 medAp7mPSF_u:  median difference between the PSF mag and the 7-bin summed aperture mag in u band (mags).
 medAp7mPSF_g:  median difference between the PSF mag and the 7-bin summed aperture mag in g band (mags).
 medAp7mPSF_r:  median difference between the PSF mag and the 7-bin summed aperture mag in r band (mags).
 medAp7mPSF_i:  median difference between the PSF mag and the 7-bin summed aperture mag in i band (mags).
 medAp7mPSF_z:  median difference between the PSF mag and the 7-bin summed aperture mag in z band (mags).

 rmsAp7mPSF_u:  rms scatter inthe difference between the PSF mag and the 7-bin aperture mag in u (mags).
 rmsAp7mPSF_g:  rms scatter inthe difference between the PSF mag and the 7-bin aperture mag in g (mags).
 rmsAp7mPSF_r:  rms scatter inthe difference between the PSF mag and the 7-bin aperture mag in r (mags).
 rmsAp7mPSF_i:  rms scatter inthe difference between the PSF mag and the 7-bin aperture mag in i (mags).
 rmsAp7mPSF_z:  rms scatter inthe difference between the PSF mag and the 7-bin aperture mag in z (mags).

 seeing_u:     average measure of the FWHM seeing (arcsec) in the u band for the field.
 seeing_g:     average measure of the FWHM seeing (arcsec) in the g band for the field.
 seeing_r:     average measure of the FWHM seeing (arcsec) in the r band for the field.
 seeing_i:     average measure of the FWHM seeing (arcsec) in the i band for the field.
 seeing_z:     average measure of the FWHM seeing (arcsec) in the z band for the field.

Each SDSS field has a quality set by the operations database (OPDBQ above). This quality is determined by the seeing of the field, the tracking of the stripe, the cloudiness of the data (photometric or not), and whether or not the photometric pipeline timed out while processing.

This OPDB quality is designated by an integer from 0-5, and is stored in the quality parameter of the tsField*.fit file for each field. Here's a key to what that quality means.

 0=UNDETERMINED,   // The data has been obtained, however its
                   // quality has not yet been determined.
 1=BAD,            // Bad data.  Don't bother with it.
 2=ACCEPTABLE,     // The data is acceptable for the survey, but we would
                   // like to improve on it.
 3=GOOD,           // The data is fully acceptable for the survey, and
                   // there is no need to improve it.
 4=MISSING,        // The data is missing, but we include the area of
                   // sky associated with the data as a hole in the
                   // survey.
 5=HOLE            // The data is unacceptable, but we include the area
		   // of sky associated with the data as a hole in the
		   // survey.

Also in the tsField file are more details on exactly why quality was set to what it was.

For instance, if the tsField file has a frames_status value of 3 = FIELD_TOO_LONG, meaning the field timed out during processing, this results in a quality = 5 (HOLE) for the overall field quality.

The psp_status is also available in the tsField file, as are the culled, badmask,acceptablemask,goodmask and holemask masks.

The quality holes are areas of sky where no objects are cataloged, and researchers interested in structure statistics of galaxy or star distributions may wish to mask out these holes from their coverage map. Roughly half of these fields include a very bright star (generally r < 5 or a very large galaxy or globular cluster, causing the object deblending in the photometric pipeline to time out. While no catalog information is available for these fields, the corrected image is available. Data of sufficiently poor quality can also be marked as a hole (where the frames_status is 0): very poor seeing (significantly worse than 2′′ FWHM), glitches in the telescope tracking, and non-photometric data. There are also a few small gaps, also marked as holes, which fall between two adjacent SDSS scans.

We note that there are different holes in the best version of sky than the target version. This is due to the photometric pipeline timing out for a number of fields processed with pipeline version v5_4, where earlier versions did not time out. In other words, if we had let the photometric processing run longer, they may have finished successfully. Future data releases will include these data.

Fields which are marked as hole will show up as holes in the large scale structure masks; objects detected in those fields are not included in the data release. The following table lists the holes in the DR4 fields.

Target skyVersion holes

run rerun camcol fieldstart-end 'quality (5=hole)' 'frames_status (3=timeout,0=ok)'
-------------------------------------------------------------------------

1737 0 6 30 5 3
1739 0 2 31 3 3
1739 0 2 160 3 3
1889 1 4 42 5 3
1895 0 1-6 170-185 5 0
1895 0 1-6 268-285 5 0
1992 0 1 141 5 3
1992 0 1 168 5 0
1992 0 2 130 5 3
2074 0 5 174 5 3
2126 0 4 278 5 3
2126 0 6 341 5 3
2248 0 1-6 186-196 5 2
2328 0 1 77 5 3
2566 0 3 108 2 3
2566 0 4 330 2 3
2566 0 6 64-65 2 3
2566 0 6 220 2 3
2583 0 1 44 3 3
2583 0 2 136 2 3
2662 0 1 38 3 3
2777 0 4 253-254 5 0
2822 0 3 35 3 3
2822 0 6 108 3 3
2825 0 1 44 5 0
2826 20 2 290-291 5 3
2864 0 5 237 2 3
2964 20 3 453 5 3
3015 0 1 105-125 5 0
3015 0 1 156 5 0
3015 0 1 159 5 0
3015 0 1 161-162 5 0
3015 0 1 195-215 5 0
3015 0 1 275 5 0
3015 0 1 283 5 0
3015 0 1 287-288 5 0
3031 20 1 407 5 3
3031 20 3 81 5 3
3031 20 4 63 5 3
3031 20 5 78 5 3
3180 0 1 72-73 5 0
3180 0 1 78-81 5 0
3180 0 1 85 5 0
3180 0 1 90-91 5 0
3187 20 1 180 5 3
3225 20 2 299 5 3
3225 20 3 71 5 3
3225 20 4 264-265 5 3
3225 20 4 310 5 3
3225 20 6 184 5 3
3225 20 6 195 5 3
3226 20 5 127 5 3
3462 20 2 202 5 3
3462 20 3 286 5 3
3462 20 3 287 5 3
3462 20 6 141 5 3
3478 20 4 103 5 3
3518 20 3 63 5 3
3525 20 5 108 5 3
3530 20 2 155 5 3
3530 20 3 240 5 3
3530 20 4 189 5 3
3538 20 1 91-92 5 3
3538 20 1 162 5 3
3538 20 4 184 5 3
3538 20 5 135 5 3
3560 20 1 231 5 3
3560 20 2 216 5 3
3605 20 1 23 5 3
3606 20 1 107 5 3
3606 20 6 100 5 3
3630 20 2 237 5 3
3630 20 4 193 5 3
3631 40 2 237-238 5 3
3631 40 3 66 5 3
3631 40 3 238 5 3
3631 40 3 401-402 5 3
3631 40 4 178 5 3
3631 40 4 221 5 3
3631 40 5 97 5 3
3631 40 5 138 5 3
3631 40 6 346 5 3
3635 40 4 145 5 3
3647 40 6 29-30 5 3
3698 40 5 131-132 5 3
3699 40 5 219-220 5 3
3699 40 6 100 5 3
3704 40 2 41-42 5 3
3704 40 5 158 5 3
3704 40 6 169 5 3
3705 20 1 333-334 5 3
3705 20 2 236 5 3
3712 20 1 120-121 5 3
3716 41 2 120 5 3
3716 41 3 37 5 3
3716 41 3 78 5 3
3723 40 4 48 5 3
3723 40 5 13 5 3
3723 40 6 67-68 5 3
3804 41 6 59 5 3
3805 41 1 117 5 3
3813 40 2 158 5 3
3813 40 4 83 5 3
3813 40 4 123-124 5 3
3813 40 5 144 5 3
3818 40 5 25 5 3
3818 40 5 198 5 3
3818 40 6 86 5 3
3838 41 1 68-69 5 3
3840 40 1 192 5 3
3840 40 1 214 5 3
3841 41 1 37 5 3
3841 41 6 198-199 5 3
3893 40 3 411 5 3
3893 40 5 344 5 3
3893 40 6 277 5 3
3894 40 3 258 5 3
3900 41 2 640 5 3
3900 41 3 715 5 3
3900 41 6 801 5 3
3909 40 1 190 5 3
3909 40 4 166 5 3
3909 40 4 270-271 5 3
3910 40 3 183 5 3
3918 41 1 100 5 3
3918 41 1 389 5 3
3918 41 3 279 5 3
3918 41 5 316 5 3
3919 40 2 40 5 3
3919 40 3 101 5 3
3919 40 4 44 5 3
3927 40 1 85 5 3
3927 40 3 11 5 3
3927 40 3 39 5 3
3964 41 1 228 5 3
3964 41 3 133 5 3
3965 40 3 55 5 3
3972 40 5 65 5 3
3992 40 4 123 5 3
3996 40 4 253 5 3
3997 40 1 28 5 3
4002 40 1 103 5 3
4002 40 1 195 5 3
4002 40 2 49 5 3
4002 40 2 50 5 3
4002 40 2 157 5 3
4002 40 2 232 5 3
4002 40 2 268 5 3
4002 40 3 147 5 3
4002 40 4 263-264 5 3
4010 40 4 102 5 3
4010 40 6 158 5 3
4010 40 6 231 5 3
4204 40 2 236 5 3
4208 40 2 237 5 3
4264 40 5 177-178 5 3
4294 40 5 153 5 3
4380 40 2 75 5 3
4381 40 2 114 5 3
4382 40 1 57 5 3
4392 40 1 114 5 3
4392 40 3 77 5 3
4470 40 2 142 5 3
4504 40 5 256-257 5 3
4512 40 3 229 5 3
4550 40 1 85 5 3
4569 40 5 56 5 3
4571 40 2 17 5 3
4576 40 2 688 5 3
4576 40 4 817 5 3
4623 40 1 324 5 3
4623 40 4 83 5 3
4632 40 3 180-182 5 3
4646 40 3 81-82 5 3
4649 40 1 416 5 3
4649 40 4 146 5 3
4670 40 4 261 5 3
4674 40 1 241 5 3
4678 40 4 249 5 3
4682 40 6 208 5 3
5061 40 2 115 5 3
5071 40 2 112 5 3
5071 40 2 215 5 3
5071 40 6 229 5 3
5080 41 1 138 5 3
5080 41 2 269 5 3
5087 40 6 292 5 3
5115 40 5 102 5 3
5140 40 1 113 5 3
5140 40 6 85 5 3
5183 40 2 406 5 3
5194 40 2 645-646 5 3
5194 40 6 700 5 3
5224 40 1 108 5 3
5225 41 4 85 5 3
5225 41 6 32 5 3
5308 40 3 111-112 5 3
5308 40 5 192 5 3
5313 40 5 116-117 5 3
5323 40 3 136 5 3
5327 40 3 54 5 3
5390 40 6 162 5 3

Best skyVersion holes

run rerun camcol fieldstart-end 'quality (5=hole)' 'frames_status (3=timeout,0=ok)'
-------------------------------------------------------------------------

752 40 2 205 5 3
752 40 2 276-277 5 0
752 40 5 692 5 3
752 40 6 660 5 3
756 44 2 587 5 3
756 44 3 338 5 3
1035 40 6 112-113 5 3
1043 40 6 149 5 3
1140 40 6 250-251 5 3
1231 40 6 141-142 5 3
1345 41 2 607 5 3
1359 40 3 60 5 0
1412 40 1 233 5 3
1412 40 3 315 5 3
1458 40 3 646 5 3
1458 40 4 674 5 3
1458 40 6 525 5 3
1462 40 5 88 5 3
1462 40 6 399 5 3
1462 40 6 458 5 3
1729 40 3 195-196 5 3
1729 40 4 387 5 3
1737 40 6 30 5 3
1739 40 2 31 5 3
1739 40 2 160 5 3
1739 40 3 24 5 3
1739 40 5 175 5 3
1740 40 2 95 5 3
1740 40 2 135 5 3
1740 40 6 54 5 3
1889 40 4 42 5 3
1895 41 1-6 270-280 5 0
1904 42 4 172 5 3
1992 40 2 130 5 3
2076 40 1 140-141 5 3
2125 40 1 132 5 3
2126 41 4 126 5 3
2126 41 4 278 5 3
2126 41 6 341 5 3
2131 40 6 25 5 3
2131 40 6 26 5 3
2137 40 2 279-280 5 3
2137 40 3 243 5 3
2137 40 6 183 5 3
2189 40 3 57 5 3
2190 40 1 144 5 3
2243 40 1 130 5 3
2243 40 3 75-77 5 0
2243 40 4 73-77 5 0
2243 40 4 131 5 3
2243 40 5 71-75 5 0
2243 40 6 70-72 5 0
2247 41 6 145 5 3
2299 41 1 300 5 3
2305 40 3 38-39 5 3
2326 41 2 309-310 5 3
2328 40 1 77-78 5 3
2328 40 1 122 5 3
2328 40 2 175 5 3
2328 40 4 38 5 3
2379 40 2 130 5 3
2566 40 2 83 5 3
2566 40 3 108 5 3
2566 40 4 330 5 3
2566 40 6 64-65 5 3
2566 40 6 219-220 5 3
2583 40 1 44 5 3
2583 40 2 136 5 3
2662 40 1 38 5 3
2662 40 2 257 5 3
2662 40 3 130 5 3
2662 40 3 141 5 3
2662 40 4 183 5 3
2662 40 5 84 5 3
2735 40 5 114-115 5 3
2738 40 4 155 5 3
2738 40 4 184 5 3
2738 40 4 280 5 3
2740 40 1 225 5 3
2740 40 4 163 5 3
2777 40 4 53 5 3
2822 40 1 49 5 3
2822 40 3 34 5 3
2822 40 3 35 5 3
2822 40 3 52 5 3
2822 40 6 108 5 3
2825 40 1 45-46 5 3
2825 40 6 208 5 3
2826 40 4 223 5 3
2826 40 4 224 5 3
2830 41 1 68 5 3
2830 41 4 252 5 3
2863 40 6 101 5 3
2864 40 2 40 5 3
2864 40 2 61 5 3
2864 40 5 186 5 3
2864 40 5 237 5 3
2883 40 5 212 5 3
2887 40 6 43 5 3
2888 40 5 45 5 3
2964 40 1 57 5 3
2964 40 6 22 5 3
2986 40 1 173 5 3
3015 40 1 333 5 3
3015 40 4 348 5 3
3015 40 6 121 5 3
3015 40 6 133 5 3
3031 40 1 407 5 3
3031 40 3 81 5 3
3031 40 4 63 5 3
3031 40 5 78 5 3
3103 40 1 130-131 5 3
3130 40 6 50 5 3
3177 40 2 229 5 3
3177 40 2 255 5 3
3180 40 4 65 5 3
3180 40 6 42 5 3
3180 40 6 76 5 3
3185 40 1 44 5 3
3187 40 1 180 5 3
3187 40 4 82 5 3
3225 40 2 299 5 3
3225 40 2 355 5 3
3225 40 2 356 5 3
3225 40 3 71 5 3
3225 40 4 264 5 3
3225 40 4 265 5 3
3225 40 4 310 5 3
3225 40 6 184 5 3
3225 40 6 195 5 3
3226 40 1 88 5 3
3226 40 5 127 5 3
3325 41 1 430 5 3
3325 41 4 99 5 3
3325 41 5 345 5 3
3388 40 3 128-129 5 3
3388 40 4 167 5 3
3462 40 2 202 5 3
3462 40 3 286 5 3
3462 40 3 287 5 3
3462 40 6 141 5 3
3478 40 4 102 5 3
3478 40 4 103 5 3
3518 40 3 63 5 3
3518 40 4 117 5 3
3518 40 4 118 5 3
3525 40 5 108 5 3
3530 42 2 155 5 3
3530 42 3 240 5 3
3530 42 4 189 5 3
3538 40 1 91-92 5 3
3538 40 4 184 5 3
3538 40 5 135 5 3
3538 40 1-6 291-310 1 0 : This is declared bad in error - to be fixed
3560 40 1 231 5 3
3560 40 2 216 5 3
3560 40 6 130 5 3
3605 40 1 23 5 3
3606 40 1 107 5 3
3606 40 4 18 5 3
3630 40 4 193 5 3
3631 40 2 237 5 3
3631 40 2 238 5 3
3631 40 3 66 5 3
3631 40 3 238 5 3
3631 40 3 401-402 5 3
3631 40 4 178 5 3
3631 40 4 221 5 3
3631 40 5 97 5 3
3631 40 5 138 5 3
3631 40 6 346 5 3
3635 41 4 145 5 3
3647 41 6 29 5 3
3664 40 2 156 5 3
3698 41 5 131-132 5 3
3698 41 5 132 5 3
3699 41 5 219-220 5 3
3699 41 6 100 5 3
3704 40 2 41-42 5 3
3704 40 5 158 5 3
3704 40 6 169 5 3
3705 40 1 333-334 5 3
3705 40 2 236 5 3
3712 40 1 120-121 5 3
3712 40 1 166 5 3
3716 42 3 37 5 3
3716 42 3 78 5 3
3716 42 6 117 5 3
3723 40 4 48 5 3
3723 40 5 13 5 3
3723 40 6 67-68 5 3
3804 41 6 59 5 3
3805 41 1 117 5 3
3813 41 4 83 5 3
3813 41 4 124 5 3
3813 41 5 144 5 3
3813 41 5 257 5 3
3818 41 5 25 5 3
3818 41 6 86 5 3
3838 41 1 68-69 5 3
3840 41 1 192 5 3
3840 41 1 214 5 3
3841 41 1 37 5 3
3841 41 6 198-199 5 3
3893 41 3 411 5 3
3893 41 5 344 5 3
3893 41 6 277 5 3
3894 40 3 258 5 3
3900 41 2 640 5 3
3900 41 3 715 5 3
3900 41 6 801 5 3
3909 40 1 190 5 3
3909 40 4 166 5 3
3909 40 4 270-271 5 3
3910 40 3 183 5 3
3918 41 1 100 5 3
3918 41 1 389 5 3
3918 41 3 279 5 3
3918 41 5 316 5 3
3919 40 2 40 5 3
3919 40 3 101 5 3
3919 40 4 44 5 3
3927 40 1 85 5 3
3927 40 3 11 5 3
3927 40 3 39 5 3
3964 41 1 228 5 3
3964 41 3 133 5 3
3965 40 3 55 5 3
3972 40 5 65 5 3
3992 40 4 123 5 3
3996 40 4 253 5 3
3997 40 1 28 5 3
4002 40 1 103 5 3
4002 40 1 195 5 3
4002 40 2 49 5 3
4002 40 2 50 5 3
4002 40 2 157 5 3
4002 40 2 232 5 3
4002 40 2 268 5 3
4002 40 3 147 5 3
4002 40 4 263-264 5 3
4002 40 2 158-325 5 0: This hole is too big - to be fixed
4002 40 3 147-325 5 0: This hole too big - to be fixed
4010 40 4 102 5 3
4010 40 6 158 5 3
4010 40 6 231 5 3
4204 40 2 236 5 3
4208 40 2 237 5 3
4264 40 5 177-178 5 3
4294 40 5 153 5 3
4380 40 2 75 5 3
4381 40 2 114 5 3
4382 40 1 57 5 3
4392 40 1 114 5 3
4392 40 3 77 5 3
4470 40 2 142 5 3
4504 40 5 256-257 5 3
4512 40 3 229 5 3
4550 40 1 85 5 3
4569 40 5 56 5 3
4571 40 2 17 5 3
4576 40 2 688 5 3
4576 40 4 817 5 3
4623 40 1 324 5 3
4623 40 4 83 5 3
4632 40 3 180-181 5 3
4646 40 3 81-82 5 3
4649 40 1 416 5 3
4649 40 4 146 5 3
4670 40 4 261 5 3
4674 40 1 241 5 3
4678 40 4 249 5 3
4682 40 6 208 5 3
5061 40 2 115 5 3
5071 40 2 112 5 3
5071 40 2 215 5 3
5071 40 6 229 5 3
5080 41 1 138 5 3
5080 41 2 269 5 3
5087 40 6 292 5 3
5115 40 5 102 5 3
5140 40 1 113 5 3
5140 40 6 85 5 3
5183 40 2 406 5 3
5194 40 2 645-646 5 3
5194 40 6 700 5 3
5224 40 1 108 5 3
5225 41 4 85 5 3
5225 41 6 32 5 3
5308 40 3 111-112 5 3
5308 40 5 192 5 3
5313 40 5 116-117 5 3
5323 40 3 136 5 3
5327 40 3 54 5 3
5390 40 6 162 5 3