Index: /trunk/doc/release.2015/ps1.calibration/calibration.tex =================================================================== --- /trunk/doc/release.2015/ps1.calibration/calibration.tex (revision 41196) +++ /trunk/doc/release.2015/ps1.calibration/calibration.tex (revision 41197) @@ -1102,7 +1102,8 @@ from the recalculated mean. -Suspicious stars are also excluded from the analysis. We exclude stars -with reduced $\chi^2$ values more than 20.0, or more than 2$\times$ -the median, whichever is larger. We also exclude stars with standard +Suspicious \textadd{(e.g., variable or otherwise poorly measured)} +stars are also excluded from the analysis. We exclude stars with +reduced $\chi^2$ values more than 20.0, or more than 2$\times$ the +median, whichever is larger. We also exclude stars with standard deviation (of the measurements used for the mean) greater than 0.005 mags or 2$\times$ the median standard deviation, whichever is greater. @@ -1152,8 +1153,4 @@ \sigma_i^{-2})^2} \end{equation} - -These rejections and the over-weighting of the Ubercal measurements -are admittedly ad hoc. Since the goal at this stage is to tie the -non-Ubercal data to the Ubercal system, we The calculation of the relative photometry zero points is performed @@ -1273,5 +1270,5 @@ For PV3, the relphot analysis was performed two times. The first analysis used only the flat-field corrections determined by the -ubercal analysis, with a resolution of 2x2 flat-field values for each +ubercal analysis, with a resolution of $2 \times 2$ flat-field values for each GPC1 chip (corresponding to \approx 2400 pixels), and 5 separate flat-field 'seasons'. However, we knew from prior studies that there @@ -1513,12 +1510,17 @@ \subsubsection{Iteratively Reweighted Least Squares Fitting} -With an automatic process applied to hundreds of millions of stars, it +With an automatic process applied to hundreds of millions of objects, it is important for the analysis to provide a measurement of the -photometry of each object which is robust against failures. The -Pan-STARRS\,1 detections have a relatively high rate of non-Gaussian -outliers, partly because of the wide range of instrumental features -affecting the data (see Paper III). \textmod{We have used Iteratively - Reweighted Least Squares (IRLS) fitting to reduce the sensitivity of - the fits to outlier measurements.} +photometry of each object which is robust against failures or other +outliers. \textadd{We would like to calculate an average magnitude + for each filter in the assumption that the flux of the star is + constant and all measurements are drawn from that population. + However, even after rejecting bad measurements based on the quality + information above, individual measurements may still be deviant.} +The Pan-STARRS\,1 detections have a relatively high rate of +non-Gaussian outliers, partly because of the wide range of +instrumental features affecting the data (see Paper III). \textmod{We + have used Iteratively Reweighted Least Squares (IRLS) fitting to + reduce the sensitivity of the fits to outlier measurements.} We have also used bootstrap resampling to determine confidence limits @@ -1787,5 +1789,6 @@ for either DR1 or DR2. An update to the database will define fields for each object which encapsulate the information about the ``primary'' -and ``best'' detections. +and ``best'' detections. Users should consult the help pages at MAST +for further information. \subsubsection{Warp Photometry} @@ -1826,5 +1829,5 @@ than PSF-like, the object bit flag \code{ID_OBJ_EXT} is raised. If more than half of the PS1 \ippstage{chip}-stage measurements within a -single filter are extended, then the per-filter bit flag +single filter are extended, then the per-filter bit flags \code{ID_SEC_OBJ_EXT} and \code{ID_SEC_OBJ_EXT_PSPS} are set. The latter bit is a duplicate bit defined because the high bit in a 32-bit @@ -1832,4 +1835,8 @@ object which has any \ippstage{chip}-stage measurements for one of the five filters has the per-filter bit flag \code{ID_SECF_HAS_PS1} set. +\textadd{Since stack images are more sensitive than the individual exposures, +faint sources which are detected in only the stacks will have the bit +flag {\tt ID\_SECF\_HAS\_PS1\_STACK} set but not {\tt ID\_SECF\_HAS\_PS1} +as the latter only refers to individual chip detections.} In addition, if the object has measurements from the 2MASS point @@ -1872,4 +1879,5 @@ \subsection{Photometry Calibration Quality} +\label{sec:photcal} % /data/kukui.1/eugene/cal.paper.images.20190217/scatter.sh : allsky.scatter.photom @@ -1892,5 +1900,5 @@ position across the sky. For each pixel in these images, we selected all objects with (14.5, 14.5, 14.5, 14.0, 13.0) $<$ ($g,r,i,z,y$) $<$ -(17, 17, 17, 16.5, 15.5) magnitudes, with at least 3 measurements in $i$-band (to +(17, 17, 17, 16.5, 15.5) \textadd{magnitudes}, with at least 3 measurements in $i$-band (to reject artifacts detected in a pair of exposures from the same night), with \code{PSF_QF} $> 0.85$ (to reject excessively-masked objects), @@ -1922,4 +1930,5 @@ 18)$ millimagnitudes. +% /data/ipp070.0/eugene/dr2.figs.20190205/ % /data/kukui.1/eugene/cal.paper.images.20190217/kronrepair.sh : full.figure \begin{figure*}[htbp] @@ -1929,5 +1938,6 @@ PV3.4 photometry illustrating the impact of the issues identified in the PV3.3 stack and warp photometry. All figures use \ips-band - photometry. The left panels use data from PV3.3 while the right + photometry, \textadd{restricted to objects brighter than 17 magnitudes with + at least 10 chip measurements}. The left panels use data from PV3.3 while the right use PV3.4. The top row shows the mean difference between the average photometry from individual exposures (``chip'') and the @@ -2025,5 +2035,5 @@ First, the astrometric calibration has a larger number of systematic -effects which must be performed. These consist of: 1) the +effects which must be corrected. These consist of: 1) the Koppenh\"ofer Effect, 2) Differential Chromatic Refraction, 3) Static deviations in the camera. We discuss each of these in turn below. @@ -2046,5 +2056,5 @@ shift of about one pixel. This effect was only observed in 2-phase OTA devices, with 22 / 30 of these suffering from this effect. By -adjusting the summing well high voltage down from a default +7 V to +adjusting the summing well high voltage down from a default +7V to +5.5V on the 2-phase devices, the effect was prevented in exposures after 2011-05-03. However, this left 101,550 exposures (27\%) already @@ -2078,7 +2088,7 @@ Differential Chromatic Refraction (DCR) affects astrometry because the reference stars used to the calibrate the images are not the same -color (SED) as the rest of the stars in the image. For a given star +color as the rest of the stars in the image. For a given star of a color different from the reference stars, as exposures are taken -at higher airmass, the apparent position of the star will be biased +at higher airmass, the apparent position of the star will be \textadd{shifted} along the parallactic angle. While it is possible to build a model for the DCR impact based on the filter response functions and @@ -2112,6 +2122,6 @@ stars used the calibrate a specific blue- or red-filter image, respecitively, while $\zeta$ is the zenith distance. -Figure~\ref{fig:DCRexample} shows the DCR trend for the 5 filters -\grizy, as well as the measured displacement in the direction +Figure~\ref{fig:DCRexample} shows the DCR trend for the \gps\ filter +as an example, as well as the measured displacement in the direction perpendicular to the parallactic angle. We represent the trend with a spline fitted to this dataset. @@ -2131,5 +2141,5 @@ \includegraphics[width=\hsize,clip]{{\picdir/DCR.example}.\plotext} \caption{\label{fig:DCRexample} Example of the DCR trend in the - g-band. {\bf top:} DCR trend in the parallactic direction {\bf + g-band, in which it is strongest. {\bf top:} DCR trend in the parallactic direction {\bf bottom:} DCR trend perpendicular to the parallactic angle.} \end{center} @@ -2139,6 +2149,6 @@ $(g,r,i,z,y) = (0.010, 0.001, -0.003, -0.017, -0.021)$ arcsec airmass$^{-1}$ magnitude$^{-1}$. We saturate the DCR correction if -the term $\left[gi_{\rm ref} - (g - i)\right] \tan \zeta$ or -$\left[zy_{\rm ref} - (z - y)\right] \tan \zeta$ for a given +the term $\left[(g - i)_{\rm ref} - (g - i)\right] \tan \zeta$ or +$\left[(z - y)_{\rm ref} - (z - y)\right] \tan \zeta$ for a given measurement is outside of the range where the DCR correction is measured. The maximum DCR correction applied to the five filters is @@ -2340,5 +2350,5 @@ In order to perform this analysis, we need estimated distances for every reference star used in the analysis. \cite{2014ApJ...783..114G} -performed SED fitting for 800M stars in the 3$\pi$ region using PV2 +performed spectral energy distribution (SED) fitting for 800M stars in the 3$\pi$ region using PV2 data. The goal of this work was to determine the 3D structure of the dust in the galaxy. By fitting model SEDs to stars meeting a basic @@ -2354,5 +2364,5 @@ and Solar motion parameters ($U_{\rm sol}, V_{\rm sol}, W_{\rm sol}$) = (9.32, 11.18, 7.61) km sec$^{-1}$ as determined by -\cite{1997MNRAS.291..683F} using Hipparchus data. Proper motions are +\cite{1997MNRAS.291..683F} using Hipparcos data. Proper motions are determined from the following: \begin{eqnarray} @@ -2366,15 +2376,24 @@ is independent of distance while the reflex motion induced by the solar motion decreases with increasing distance. Also note that this -model assumes a flat rotation curve for objects in the thin disk. Any +model assumes a flat rotation curve for objects in the thin disk. \textmod{Any reference stars which are part of the halo population will have proper motions which are not described by this model; the mostly random nature of the halo motions should act to increase the noise in the -measurement, but should not introduce detectable motion biases. Also, -if the distance modulus is not well determined, we can assume the -object is simply following the Galactic rotation curve and set a fixed -proper motion. If we do not have a distance modulus from the Green et -al analysis, we assume a value of 500pc. - -\note{find the improvement by using 2MASS -- in the PS1 DRAVG pages} +measurement. We do not attempt to compensate for asymmetric drift in +the populations with higher radial velocity dispersion. This effect +will introduce some bias in the azimuthal direction which our simple +model cannot address. For stars for which the distance modulus is not +well determined, we assume the object is simply following the Galactic +rotation curve and set a fixed proper motion.} If we do not have a +distance modulus from the Green et al analysis, we assume a value of +500pc. \textadd{We find that applying our Galactic rotatation model improves +the systematic proper motion errors to some extent. The standard +deviation of the quasar proper motions (averaged on 12 arcminute +superpixels across the sky) is reduced from $(\sigma_{\mu,\alpha}, +\sigma_{\mu,\delta}) = (4.6, 2.4)$ mas yr$^{-1}$ for the uncorrected +analysis to $(\sigma_{\mu,\alpha}, \sigma_{\mu,\delta}) = (2.9, 2.0)$ +mas yr$^{-1}$ after correction for the Galactic rotation model. The +remaining quasar motions continue to show some systematics which may +suggest the need to include a correction for the asymmetric drift.} For the initial PV3 analysis, we again used the 2MASS coordinates as @@ -2388,5 +2407,7 @@ the Gaia DR1 coordinates. The Gaia DR1 coordinates used a fixed 2015 epoch. Coordinates were propagated from that epoch to the epoch for -each PS1 image as described above. +each PS1 image as described above. \textadd{In a future analysis, we will use +the Gaia DR2 proper motions to tie the astrometric analysis to Gaia +both in terms of the mean positions as well as the dynamical system.} \subsection{Object Astrometry} @@ -2406,5 +2427,7 @@ \code{ID_MEAS_USED_OBJ}. Some detections were identified as extreme outliers if their position deviated from the mean object coordinate by -more than 2 arcseconds. These detections were ignored and marked with +more than 2 arcseconds. \textadd{Such a large deviation can only occur when +the in-database calibration is poor, for example near the edges of a +chip.} These detections were ignored and marked with the bit flag \code{ID_MEAS_POOR_ASTROM}. @@ -2418,16 +2441,14 @@ \subsubsection{Iteratively Reweighted Least Squares Fitting} -With an automatic process applied to hundreds of millions of stars, it -is important for the analysis to provide a measurement of the -astrometry of each object which is robust against failures. The -Pan-STARRS\,1 detections have a relatively high rate of non-Gaussian -outliers, partly because of the high degree of structure in the -astrometric transformations introduced by the camera optics and the -atmosphere, and partly due to the high masked fraction and other -detector effects. We have used a techinique called Iteratively -Reweighted Least Squares (IRLS) fitting to reduce the sensitivity of -the fits to outlier measurements. We have also used bootstrap -resampling to determine confidence limits on our fits given the -observed collection of position measurements. +\textmod{Just as with the photometric analysis, it is also important for the +astrometric analysis to provide a measurement which is robust against +failures. In addition to the detector effects artifacts which affect +astrometry, the astrometric measurments may have non-Gaussian outliers +due to the high degree of structure in the astrometric transformations +introduced by the camera optics and the atmosphere. We have again +used the IRLS technique to reduce the sensitivity of the fits to +outlier measurements.} We have also used bootstrap resampling to +determine confidence limits on our fits given the observed collection +of position measurements. We begin the astrometric analysis for each object by projecting the @@ -2474,5 +2495,5 @@ weights. New values for $\omega_\eta,\omega_\zeta$ are calculated, and the fit is tried again. On each iteration, the fitted parameters -are compared to the values from the previous iteration. If they +are compared to the values from the previous iteration. If the parameters have not changed significantly ($< 10^{-6}$) or if the fractional change is less than some tolerance ($10^{-4}$), then @@ -2494,12 +2515,13 @@ Bootstrap-resampling analysis is used to assess the errors on the fit -parameters: A number of measurements equal to the number of unclipped -data points are randomly selected from the set of unclipped data -points, with replacement after each selection. These data points are -then used to fit for the astrometric parameters, using ordinary least -squares fitting. The parameters are recorded and the process re-run -300 times. For each astrometric parameter, the error is determined as -half of the 68\% confidence range for the distribution of fitted -parameter values. +parameters in a fashion similar to the photometry analysis: A number +of measurements equal to the number of the remaining unclipped data +points are randomly selected from the set of the remaining unclipped +data points, with replacement after each selection. These data points +are then used to fit for the astrometric parameters, using ordinary +least squares fitting. The parameters are recorded and the process +re-run 300 times. For each astrometric parameter, the error is +determined as half of the 68\% confidence range for the distribution +of fitted parameter values. \subsubsection{Object Astrometry Flags} @@ -2511,5 +2533,5 @@ fitted to parallax without proper motion as well. If an object is fitted for parallax, it is also fitted with a model including only -proper motion and only a mean position. The chisq for all three fits +proper motion and only a mean position. The chi-square for all three fits is saved. Currently, the highest order fit allowed is saved in the database, regardless of the significance of the improvement in adding @@ -2631,5 +2653,5 @@ \sigma_\delta)$ is 16 milliarcseconds. -The Galactic plane is clearly apparently in these images. Like +The Galactic plane is clearly apparent in these images. Like photometry, we attribute this to failure of the PSF fitting due to crowding. The celestial North pole regions have somewhat elevated @@ -2721,5 +2743,5 @@ Solar motion to correct the absolute proper motion (see Section~\ref{sec:galactic.rotation}). We identify the resulting - database as PV3.1. This database was used to generate the positions + database as PV3.2. This database was used to generate the positions in the \ippdbtable{gaiaObject} table, which are exposed in the DR1 release. @@ -2786,12 +2808,14 @@ \begin{center} \includegraphics[width=\hsize,clip]{{\picdir/gaia.photom.v1}.\plotext} - \caption{\label{fig:gaia.photom} Comparison with Gaia DR1 - photometry. {\bf Left} Mean of PS1 - Gaia DR1, {\bf Right} Standard - deviation of PS1 - Gaia DR1. For pixels with $|b| > 30$ and $\delta > - -30$, the standard deviation of the PS1 - Gaia DR1 mean values is 6.9 - millimagnitudes, while the median of the standard deviations is 12.4 - millimagnitudes. The former is a statement about the consistency - of the Gaia DR1 and Pan-STARRS\,1 photometry, while the latter - reflects the combined bright-end errors for both systems. } + \caption{\label{fig:gaia.photom} Comparison with Gaia DR1 photometry + (see Section~\ref{sec:gaia.tie} for sample selection). {\bf Left} + Mean of PS1 - Gaia DR1, {\bf Right} Standard deviation of PS1 - + Gaia DR1. For pixels with $|b| > 30$ and $\delta > -30$, the + standard deviation of the PS1 - Gaia DR1 mean values is 6.9 + millimagnitudes, while the median of the standard deviations is + 12.4 millimagnitudes. The former is a statement about the + consistency of the Gaia DR1 and Pan-STARRS\,1 photometry, while + the latter reflects the combined bright-end errors for both + systems. } \end{center} \end{figure*} @@ -2869,5 +2893,5 @@ signal to noise in Gaia; they were also apparent in the plots of the statisics of the per-exposure measurement residuals -(Figure~\ref{fig:allsky.astrom.sigma}. The standard deviations of the +(Figure~\ref{fig:allsky.astrom.sigma}). The standard deviations of the median differences are ($\sigma_\alpha, \sigma_\delta) = (4.8, 3.1)$ milliarcseconds. @@ -2932,5 +2956,5 @@ \begin{figure*}[htbp] \begin{center} - \includegraphics[width=\hsize,clip]{{\picdir/A4}.pdf} + \includegraphics[width=0.95\hsize,clip]{{\picdir/A4}.pdf} \caption{\label{fig:pole.bad.histogram} Histogram of the fraction of bad groups for each skycell (red line).} \end{center} @@ -2949,5 +2973,5 @@ based on a comparison between stack and mean object photometry. In the presence of modest registration errors, mean object photometry would -not be affected, as individual detection woulds have the correct +not be affected, as individual detection would have the correct signal, and averaging their flux in catalog space would yield the correct total magnitude. On the other hand, imperfect stacking would @@ -2960,5 +2984,5 @@ in poor stack photometry for the affected skycells. -Further investigaion revealed that the cause of these failures was an +Further investigation revealed that the cause of these failures was an error in the internal reference catalog used for the PV3 analysis (see Section~\ref{sec:synthdb}). This reference catalog used PS1 @@ -2994,7 +3018,7 @@ We first used the PV3 mean astrometry and photometry to define a new reference catalog in the assumption that the bulk of the failures -would be eliminated by the astrometric recalibration. We reprocesed a +would be eliminated by the astrometric recalibration. We reprocessed a section of the polar cap data using this PV3-based reference catalog -and re-ran the astrometric registration test was repeated on the +and re-ran the astrometric registration test on the reprocessed exposures. The reprocessing greatly ameliorated the registration issue, as shown in Figure~\ref{fig:pole.bad.histogram}. @@ -3016,10 +3040,10 @@ We consider skycells with more than 10\% bad groups to have been -adversely affected by this problem. Uses of DR2 should be aware that -the affected skycells have poor astrometry and effective image +adversely affected by this problem. Users of DR2 should be aware that +the affected stack skycells have poor astrometry and effective image quality. However, as these images may be useful to the community, they are available from the MAST cutout server. Users who attempt to download these problem skycells will see a warning message and should -avoid using the skycell images for quantitative measurements without +only use the skycell images for quantitative measurements with extreme caution. Since stack measurements from these skycells are significantly damaged, the DR2 release has set the measured stack @@ -3029,5 +3053,5 @@ \section{Conclusion} -The Pan-STARRS Data Release 2 provides astromtry and photometry of +The Pan-STARRS Data Release 2 provides astrometry and photometry of roughly 3 billion astronomical objects across the $3\pi$ survey region. The photometry system has been shown to be reliable across @@ -3047,5 +3071,118 @@ community. -\note{need to add discussion of SDSS, DES, LSST, Gaia} +\textadd{The past three decades have seen the digital release of a series of +large-scale optical and near-IR astronomical surveys with generally +steady improvements in quality. The trend begins in the mid 1990s +with the digitized photographic plate surveys such as USNO-B +\cite{2003AJ....125..984M} and SuperCOSMOS \cite{2001MNRAS.326.1295H} +which have photometric errors of roughly 300 millimags and astrometric +errors of roughly 200 milliarcseconds. The Hipparcos \& Tycho +catalogs released in the mid 1990s have much smaller astrometric +errors (roughly 0.6 milliarcseconds) but substantially limited depth +($V < 11.5$) compared to the ground-based work +\citep{1997AA...323L..57H}.} + +\textadd{The first generation of sky surveys using digital detectors, including +SDSS \citep{2001ASPC..238..269L} and 2MASS +\citep{2006AJ....131.1163S}, brought a substantial leap in the quality +of both photometry and astrometry along with improvements in the depth +and wavelength coverage. Glossing over the details of how exactly to +determine the accuracy of the SDSS and 2MASS photometry, it is clear +that the photometric accuracy of those surveys are in the vicinity of +10 - 20 millimagnitudes for all filters, more than an order of +magnitude improvement over the photographic plate surveys. The +astrometric accuracy of these two surveys (roughly 50 - 80 +milliarcseconds) is also a large improvement.} + +\textadd{The Pan-STARRS $3\pi$ Survey public release represents an important +step in the ongoing progress towards covering the sky with +well-characterized measurements. The nearly coincident data releases +from Gaia \citep{2016AA...595A...4L,2018AA...616A...1G} complement the +PS1 releases greatly. In the south, the Dark Energy Survey has +produced its first public data release covering roughly 5000 square +degrees of the sky \citep{2018ApJS..239...18A} with reported +photometric precision of better than 10 millimagnitudes.} + +\textadd{The next decade will see further advances in survey breadth and depth +along with further improvements in calibration quality. Over the next +2-3 years, the Ultraviolet Near-Infrared Optical Northern Sky (UNIONS) +Survey collaboration (a meta-collaboration of the Pan-STARRS and +Canada-France Imaging Survey, or CFIS, collaborations) is expected to +release deep photometry in the {\it ugriz} bands for roughly 5000 +square degrees of the northern hemisphere with agressive photometric +precision goals. This collaboration is in part motivated to support +the Euclid satellite mission, which requires deep 8-band photometry to +measure photometric redshifts, but only provides the {\it JHK} bands. +The Large Synoptic Survey Telescope is also expected to produce +high-precision photometry and astrometry to great depths over a very +large portion of the sky available from the southern hemisphere.} + +\textadd{From our experience with the Pan-STARRS survey, and the results of the +comparisons between surveys, a few lessons stand out.} + +\textadd{First, systematic errors come in many forms and dominate the +calibration precision. Internal or relative examination of the data +can reveal important and unexpected effects such as the Koppenh\"ofer +and vertical diffusion effects we identified in the Pan-STARRS +devices.} + +\textadd{Second, cross-comparisons between independent datasets are critical to +reveal the limitations. This lesson has appeared several times in our +intestigations, in the comparison between Pan-STARRS and Gaia above, +between Pan-STARRS and SDSS \citep{2016ApJ...822...66F}, and in the +comparison between Pan-STARRS and 2MASS \citep{2013ApJS..205...20M}. +The cross-comparison can be used to explicitly constrain the +calibration on one survey based on another, as was done by +\cite{2016ApJ...822...66F} for the SDSS Hypercalibration solution. +Alternatively, the cross-comparison can be used to identified issues +which may be solved by improved internal analysis. } + +\textadd{The third lesson we have learned is that there is no substitute for +photometric conditions. The cross-comparison of photometry between +Pan-STARRS and Gaia suggests that the current Pan-STARRS calibration +is limited in part by the excessive contribution of non-photometric +observations. This can be seen in the elevated scatter in patches +which correspond to single observing blocks (see +Figure~\ref{fig:allsky.photom.sigma} and discussion in +Section~\ref{sec:photcal}). A future re-analysis of the Pan-STARRS +dataset will attempt to further limit the impact of the +non-photometric data on the photometric calibration. The other +critical improvement will be to include more data from the continuing +observations to ensure every patch of the sky is covered with +photometric observations.} + +\textadd{Finally, while the systematics are still probably the limiting factor +for the average calibration, for individual measurements of objects, +we believe our current limitations come from a few specific factors. +First, the quality of the aperture corrections, especially in the +ability of the software to avoid extremely deviant results on occasion +appears to be one of the main drivers of bad photometry measurements +for brighter stars. Second, the quality of the background sky model +currently appears to be the limitation for the faint sources. +Finally, improvements to the PSF model, especially including +color-dependent and non-linear effects such as the brighter-fatter effect +\citep{2014JInst...9C3048A,2015JInst..10C5032G} will probably be +necessary to push the limits of photometric and astrometric accuracy. } + +\textadd{While there is clearly still room for improvement, the Pan-STARRS +$3\pi$ Survey DR1 and DR2 photometry will be a critical resource for +many years. We are confident that, in addition to the many science +discoveries enabled by the large and accurate photometry, the +high-quality photometry provided here will save observers countless +hours of telescope time by obviating, or at least greatly reducing, +the need to observe standard stars on a regular basis.} + +%% USNO-A,B : 0.2 arcsec, 0.3 mag, R ~ 21 +%% https://arxiv.org/pdf/astro-ph/0210694.pdf +%% https://ui.adsabs.harvard.edu/abs/2003AJ....125..984M/abstract +%% SuperCOSMOS : 0.2 arcsec, 0.3 mag +%% http://www-wfau.roe.ac.uk/sss/intro.html +%% https://ui.adsabs.harvard.edu/abs/2001MNRAS.326.1295H/abstract +%% https://ui.adsabs.harvard.edu/abs/2001MNRAS.326.1315H/abstract +%% Hipparcos : XX mas, 0.XX mag +%% https://ui.adsabs.harvard.edu/abs/1997A%26A...323..620K/abstract +%% https://ui.adsabs.harvard.edu/abs/1997A%26A...323L..57H/abstract + +% \note{need to add discussion of SDSS, DES, LSST, Gaia} \acknowledgments @@ -3134,2 +3271,4 @@ kukui:/data/kukui.3/eugene/pv3.stats.20161202/maps.measure +% /data/ipp070.0/eugene/dr2.figs.20190205/ +% /data/kukui.1/eugene/cal.paper.images.20190217/kronrepair.sh : full.figure