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• What is histogram of slew times between az,alt pairs? 
• Kem asserts it takes about 5 sec to slew between adjacent fields. But that's not right. Assuming we go mostly in elevation, no dome limitation, is angular acceleration limited. We accelerate for half and decelerate for half the time. So the half-slew time obeys (elevation-limited) theta=(1/2)alpha*t^2, and theta = 3.5/2 and alpha for elevation is (conveniently) 3.5 deg/s/s so t=sqrt(2*(theta/alpha)=sqrt(2) = 1.41 sec. So kinematic adjacent-field best slew time is 2.8 sec. Add one sec for settling and we get 3.8 sec, call it 4, not 5. 
• ** we should take OpSim output of pointings, with rotator angle, and compute bounding boxes in RA, DEC, then import into GIS database to do rapid queries of coverage in time and filter space. 
• Do maximum unobserved gap analysis for each field for each filter. 
• Phil Pinto suggests computing next-field time needed as a parallel process. 
• Do object-based coverage analysis rather than field-center-based analysis
• How do we represent both transparency and sky brightness across a field? Scalar (what's done now), vector (histogram) or matrix (sky image)?\

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Feb 8, 2014

Using ESSENCE data set to look at cloud transmission. Email from Gautham:

Hi,

We have both things, but neither exactly in the form in your email. We save zero points for each image of course, and I have the average zero point. You can take the differences, and some component of the difference is attributable to extinction due to clouds - I'd imagine the histogram of the differences will be some gaussian with an exponential decay on one side.
This data is in a binary table - I can make it FITS or text if you like but it's 32MB compressed so too big to email - do you have your odyssey account?

It's got other information you don't ask for in your email, but I'm guessing you will want - filter, exptime, airmass, fwhm, aperture correction, zptmag (offset + apercorr modulo a negative sign), number of stars used in the zptmag fit, Chi_sq of that fit, MJD-OBS...

In [9]: zptdata.dtype.descr
Out[9]:
[('date', '|S6'),
('dcmpfile', '|S32'),
('filter', '|S1'),
('exptime', '<f8'),
('airmass', '<f8'),
('field', '|S4'),
('amp', '|S2'),
('apercorr', '<f8'),
('apercerr', '<f8'),
('offset', '<f8'),
('doffset', '<f8'),
('x2red', '<f8'),
('skyadu', '<f8'),
('sky0', '<f8'),
('nim', '<i8'),
('nused', '<i8'),
('nskip', '<i8'),
('pused', '<f8'),
('cterm', '<f8'),
('ctermerr', '<f8'),
('fitgood', '<i8'),
('fitair', '<i8'),
('fitcolor', '<i8'),
('airmflag', '<i8'),
('apcorflag', '<i8'),
('dpfwhm1', '<f8'),
('dpfwhm2', '<f8'),
('mjdobs', '<f8')]



There is also sorta 5 sigma uncertainties - but they are really saved as magnitudes at specific values of median uncertainty:

gnarayan@rclogin05|/n/panstarrs/data/v10.0/W/workspace/sm061128/10> imhead wdd7.061128_0658.133_10.sw.dcmp | grep MAU
MAU010  = 'UNKNOWN,<=20.2'     / magnitude with median uncertainty of 0.010
MAU015  = 'UNKNOWN,<=20.2'     / magnitude with median uncertainty of 0.015
MAU020  =               20.333 / magnitude with median uncertainty of 0.020
MAU050  =               21.399 / magnitude with median uncertainty of 0.050
MAU100  =               22.173 / magnitude with median uncertainty of 0.100
MAU200  =               23.012 / magnitude with median uncertainty of 0.200


These are only stored in the FITS headers - I can convert these also into a table. You probably also want the additional file headers.

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Logged onto odyssey. (run gorc.sh &, then use RSA key). 

SM data are in 

/n/panstarrs/data/v10.0/W/workspace

then smddmmyy. 

to get Gautham/Armin toolkit, on odyssey 

csh

source .myrc

(which I stole from Gautham)

.dcmp files carry image headers and can use wcstools imhead utility on those files. 

can get them with 

ls w*.sw.dcmp

pulled out zero points for one single amp for all nights with

stubbs@rclogin10|/n/panstarrs/data/v10.0/W/workspace> gethead MJD-OBS ZPTMAG sm??????/3/w*.sw.dcmp > ESSENCE_zpts.dat

put ESSENCE_zpts.dat in my home directory on odyssey.

Here is it, also: 

ESSENCE_zpts.dat

Also, Gautham extracted R and I band zero point values, and provided these two data files: 

R band extinction is 0.104 mag/airmass. 

The three columns are : observation name, MJD of observation, zero point. 

changes in zero point are due to both clouds and airmass. 

Took Gautham's data set and did correction for airmass, make cumulative plot of delta zero point, sorted. 

Image Added

Image Added

Image Added

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Some references

LSST science book

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