Mailman 3 নভেম্বর 2014 - AstroPy

Access to comments in astropy.io.asccii
by Knox Long 24 নভেম্বর, 2014

24 নভেম্বর, 2014

I/we are trying to move to astropy.io.ascii.read for reading ascii.data, and for the most part this is working well. However, we often also want access to comment lines in our ascii data and I have not found any way to do this. Is there something I am missing. Here is an example of what I would like to be able to read: # TITLE= "test.ioncC3.dat" # Coord_Sys CYLIND x z var inwind i j 1.4000e+09 3.5000e+08 0.00e+00 -2 0 0 1.4000e+09 8.0805e+08 0.00e+00 -1 0 1 1.4000e+09 1.0575e+09 0.00e+00 -1 0 2 1.4000e+09 1.3840e+09 0.00e+00 -1 0 3 1.4000e+09 1.8113e+09 0.00e+00 -1 0 4 1.4000e+09 2.3705e+09 0.00e+00 -1 0 5 1.4000e+09 3.1023e+09 0.00e+00 -1 0 6 1.4000e+09 4.0600e+09 0.00e+00 -1 0 7 Thanks, Knox

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Re: [AstroPy] astropy.coordinates vs kapteyn.celestial Coordinate Transformations
by vogelaar＠astro.rug.nl 24 নভেম্বর, 2014

24 নভেম্বর, 2014

Hello, There are two articles which support the decisions I made for the conversion of positions from fk5 to galactic in module celestial of the Kapteyn Package. The first article documents the rotation matrix that I used and the second article (written after the current version of celestial) documents the same matrix derived in a slightly different way. 1) Murray, C.A., 1989. The transformation of coordinates between systems of B1950.0 and J2000.0 and the principal galactic axes referred to J2000.0, Astron. Astrophys, 218, p.325-329, 2) Jia-Cheng Liu, Zi Zhu, Hong Zhang, Reconsidering the galactic coordinate system, arXiv:1010.3773 [astro-ph.GA] All the procedures implemented in celestial are documented in https://www.astro.rug.nl/software/kapteyn/celestialbackground.html The problem conversion mentioned by Joseph is: from kapteyn import celestial print celestial.sky2sky(celestial.galactic, celestial.fk5, [292.03306305555554], [1.7592747222222223]) [[ 171.158163857372 -59.263193188529]] which differs from the result by pyregion by a third of an arcsec. Murray proposed that the axes of the IAU1958 galactic coordinate system should be considered as absolute directions, unaffected by the E-term of aberration. This system is (in FITS terms) called FK4-NO-E. This approach has been approved by Adriaan Blaauw (private communications, 2008), so in fact I use: m1 = celestial.skymatrix(celestial.fk5, celestial.fk4_no_e) print m1[0] [[ 9.999256794957e-01 1.118148323917e-02 4.859003772314e-03] [ -1.118148322047e-02 9.999374848933e-01 -2.717029374405e-05] [ -4.859003815359e-03 -2.716259471425e-05 9.999881946024e-01]] This is the same matrix as Xo in Liu et al. in equation 9 m2 = celestial.skymatrix(celestial.fk4_no_e, celestial.galactic) In [27]: print m2[0] [[-0.066988739415 -0.872755765852 -0.483538914632] [ 0.492728466075 -0.45034695802 0.744584633283] [-0.867600811151 -0.188374601723 0.460199784784]] This is the same matrix as Nb in Liu et al. in equation 9 and the same as in Slalib (http://stsdas.stsci.edu/cgi-bin/gethelp.cgi?eg50.src) print m2[0]*m1[0] [[-0.054875539396 -0.873437104728 -0.48383499177 ] [ 0.494109453628 -0.444829594298 0.7469822487 ] [-0.867666135683 -0.198076389613 0.455983794521]] This is the same matrix as Nj in Liu et al. in equation 9 and Murray equation 33. The same matrix is constructed for: m3 = celestial.skymatrix(celestial.fk5, celestial.galactic) print m3[0] [[-0.054875539396 -0.873437104728 -0.48383499177 ] [ 0.494109453628 -0.444829594298 0.7469822487 ] [-0.867666135683 -0.198076389613 0.455983794521]] The inverse transformation is: lonlat= celestial.sky2sky(celestial.galactic, celestial.fk5, [0], [0]) With this expression we find the galactic center in equatorial coordinates: celestial.lon2hms(lonlat[0,0],prec=4) '17h45m37.1991s' celestial.lat2dms(lonlat[0,1],prec=4) '-28d56m10.2207s' which are the same values as in Liu et al. equation 11. For the pole: lonlat= celestial.sky2sky(celestial.galactic, celestial.fk5, [0], [90]) celestial.lon2hms(lonlat[0,0],prec=4) '12h51m26.2755s' celestial.lat2dms(lonlat[0,1],prec=4) ' 27d07m41.7043s' which are the same as the position given in Murray section 7.1 and Liu equation 10. So the transformation requires that the e-terms are removed. and it uses a rotation matrix which is documented in several articles and which guarantees that the galactic coordinate system is orthogonal. The suggestion of Thomas Robitaille seems therefore worthwhile to discuss. Martin > Hello, > > I've been porting pyregion to use astropy instead of kapteyn, and tests > with coordinate system conversions are slightly off. > > I think I've narrowed down the problem to my expectation that this should > be nearly zero: > > In [21]: from astropy.coordinates import SkyCoord > > In [22]: from kapteyn import celestial > > In [23]: a = SkyCoord('292.03306305555554d 1.7592747222222223d', > frame='galactic').transform_to('fk5'); print(a) > <SkyCoord (FK5: equinox=J2000.000): ra=171.158093022 deg, > dec=-59.2630875829 deg> > > In [24]: celestial.sky2sky(celestial.galactic, celestial.fk5, > [292.03306305555554], [1.7592747222222223]) > Out[24]: matrix([[ 171.15816386, -59.26319319]]) > > In [25]: SkyCoord('171.15816386d -59.26319319d', > frame='fk5').separation(a).to('arcsecond') > Out[25]: <Angle 0.4019071919711007 arcsec> > > > My question is: am I misunderstanding something about these coordinate > transformations to make them not equivalent? A third of an arcsecond is > significantly big deviation, particularly for HST or interferometry. AFAIK > fk5 is J2000 in both libraries and galactic coordinates have no concept of > epoch or equinox time. > > Thanks, > Joseph Booker > _______________________________________________ > AstroPy mailing list > AstroPy(a)scipy.org > http://mail.scipy.org/mailman/listinfo/astropy >

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astropy.coordinates vs kapteyn.celestial Coordinate Transformations
by Joseph Booker 16 নভেম্বর, 2014

16 নভেম্বর, 2014

Hello, I've been porting pyregion to use astropy instead of kapteyn, and tests with coordinate system conversions are slightly off. I think I've narrowed down the problem to my expectation that this should be nearly zero: In [21]: from astropy.coordinates import SkyCoord In [22]: from kapteyn import celestial In [23]: a = SkyCoord('292.03306305555554d 1.7592747222222223d', frame='galactic').transform_to('fk5'); print(a) <SkyCoord (FK5: equinox=J2000.000): ra=171.158093022 deg, dec=-59.2630875829 deg> In [24]: celestial.sky2sky(celestial.galactic, celestial.fk5, [292.03306305555554], [1.7592747222222223]) Out[24]: matrix([[ 171.15816386, -59.26319319]]) In [25]: SkyCoord('171.15816386d -59.26319319d', frame='fk5').separation(a).to('arcsecond') Out[25]: <Angle 0.4019071919711007 arcsec> My question is: am I misunderstanding something about these coordinate transformations to make them not equivalent? A third of an arcsecond is significantly big deviation, particularly for HST or interferometry. AFAIK fk5 is J2000 in both libraries and galactic coordinates have no concept of epoch or equinox time. Thanks, Joseph Booker

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TAN WCS speedup
by Maik Riechert 14 নভেম্বর, 2014

14 নভেম্বর, 2014

Hi, I just finished implementing my own wcs_pix2world function specifically for the TAN projection using just Python with numpy and numexpr. Without numexpr I was slightly slower than astropy (15s vs 12.8s). But with numexpr I got it down to 6.8s, so nearly twice as fast. This is for 8 million pixel coordinates as input run on my 2GHz Core 2 Duo Laptop under Python 2.7 64 bit with Windows 7 and using Christoph Gohlke's numpy and numexpr binaries. I cannot post the code yet but the code is not that important anyway as I didn't do really complicated things. As numexpr seems to provide the main speedup, maybe some concepts of it could be used to speedup astropy/wcslib. I guess it's not a sensible option to actually implement all of wcslib in Python, given that there are way more complicated projections etc. than TAN which would take quite some time to reimplement/maintain. This is basically it, just wanted to share that. Cheers Maik

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fourpiskytools - simple Python examples for sending and receiving VOEvents
by Tim Staley 13 নভেম্বর, 2014

13 নভেম্বর, 2014

Hi all, if any of you are working on follow-up of transient events, you might be interested in a package I've just put together: https://github.com/timstaley/fourpiskytools The package aims to provide a 'minimum working example' of how one might get started working with VOEvents, that can be easily adapted for your specific needs. VOEvents are the standardised format for distributing alerts (gamma-ray burst here, detected in optical, etc etc), and are intended to be machine readable, as opposed to the current typical method of posting human-written reports as ATels or on a dedicated project website. The transport protocol uses a 'keep-alive' connection, so they're also pretty low-latency (compared with e.g. sending emails). Finally, as compared to say NASA-GCN, they are flexible enough to be adapted for many different telescopes, and support a decentralised publication model. The hope is that if we can get more teams on-board and using VOEvent, it opens up a slew of possibilities for rapid event classification and targeted follow-up. Note that fourpiskytools is built on voevent-parse (http://voevent-parse.readthedocs.org/en/master/), a package for which I'm currently considering how best to integrate the astropy core functionality, so if that would be useful to you and you'd like to see it soon then drop a note on the relevant issue: https://github.com/timstaley/voevent-parse/issues/2 Happy transient hunting! -Tim

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WCS creation
by Martin Beroiz 4 নভেম্বর, 2014

4 নভেম্বর, 2014

Hello everybody, I have an image for which I have the RA-Dec information for some sources along with the pixel location. From that info, I want to create a WCS object with astropy preferably. Is there a simple way to do that? I read the docs for the WCS class but it seems it only manipulates WCS but won’t create one from the information on a few stars. Basically, I’m looking for a python equivalent of STARAST for IDL http://idlastro.gsfc.nasa.gov/ftp/pro/astrom/starast.pro Is there a built-in way to do this with astropy or affiliated package? Thanks for your help. M.

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Apply now for the Python in Astronomy Lorentz workshop! (20-24th April 2015)
by Thomas Robitaille 3 নভেম্বর, 2014

3 নভেম্বর, 2014

Dear colleagues, We are very pleased to inform you that applications are now open for the Lorentz Center workshop on: Python in Astronomy Lorentz Center, Leiden 20-24th April 2015 http://python-in-astronomy.github.io This workshop aims to bring together researchers, Python developers, users, and educators, and will include presentations, tutorials, unconference sessions, and coding sprints. In addition to sharing information about state-of-the art Python Astronomy packages, the workshop will also focus on improving interoperability between astronomical Python packages, providing training for new contributors, and developing a common set of educational materials for Python in Astronomy. The meeting is therefore aimed not only at current developers, but also users and educators who are interested in being involved in these efforts. To apply, please go to the following page: http://python-in-astronomy.github.io/ and follow the link to the application form. Applications should be submitted by 28th November 2014 at the latest, and we will let you know by mid-December whether you have been accepted. The workshop will be hosted by the Lorentz Center, which is an international center that coordinates and hosts workshops in the sciences, based on the philosophy that science thrives on interaction between creative researchers. In addition to being supported by the Lorentz center, this meeting is being sponsored by GitHub (http://www.github.com) and NumFOCUS (http://www.numfocus.org). We are thus able to offer financial support for travel for a few junior participants. If you would like to apply for financial support in order to attend the meeting, please indicate this in the last section of the application form. Please forward this email to anyone who may be interested, including Python or workshop announcement mailing lists! Best regards, Thomas Robitaille, on behalf of the organizing committee: Pauline Barmby Eric Jeschke Sarah Kendrew Stuart Mumford Magnus Persson Thomas Robitaille

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Job ad: LSST software lead @ U. Washington (research faculty)
by Mario Juric 2 নভেম্বর, 2014

2 নভেম্বর, 2014

Hi everyone, I wanted to bring to your attention a search (at the research faculty level) for the lead of the Large Synoptic Survey Telescope (LSST) data pipelines effort at the University of Washington: https://jobregister.aas.org/node/49445 The ad itself is pasted below; I hope you find it interesting! PS: Also as a heads up -- LSST will be hiring about a ~dozen more people in the coming ~1-2 years (@ UW, Princeton, NCSA, SLAC, and LSST HQ in Tucson) to develop various (open source, Python/C++) LSST toolkits and processing pipelines. If you're interested in software for large surveys, keep an eye on http://lsst.org/hiring. Thanks (and do feel free to e-mail me with any questions!), - Mario ======== Research Assistant or Research Associate Professor of Astronomy, University of Washington - JRID49445 The Large Synoptic Survey Telescope (LSST) is a planned, large-aperture, wide-field, ground-based telescope that will survey half the sky every few nights in six optical bands. It will create the world's first high-definition movie of the universe, detect hazardous asteroids, help uncover the mysteries of dark energy and dark matter, and more. With an 8-meter class telescope, a 3.2 gigapixel camera with a 2-second readout, and a state-of-the-art petascale data management system, the LSST will process, archive, and distribute over 15 TB of data produced every night. Once completed, the LSST will be the largest and most modern optical survey project ever built. The LSST Data Management system will be constructed by a team of about 50 members residing at partner institutions across the United States and Chile. It will include a data processing system spanning two continents, new state-of-the-art image processing algorithms, petascale computing clusters with tens of thousands of cores, large distributed databases, and next-generation analysis toolkits, among others. All LSST DM code is free software (GPL v3), written in modern Python and C++. The University of Washington (UW) LSST team is responsible for the development of the algorithms and software that will analyze this nightly data stream (including the detection and characterization of transients, variables, and moving sources). To support this work at UW, we are soliciting applications for the position of Research Assistant or Research Associate Professor in the Department of Astronomy. University of Washington faculty engage in teaching, research and service. The successful candidate will lead the LSST data management group at UW, and is expected to play a leading role in the development of the software for the nightly processing of the LSST data (including, but not limited to, the development of algorithms for image subtraction, the detection of transient and variable sources, and the characterization of transient and variable sources) and the application of the LSST Data Management system to simulated and precursor survey data. Pending appointment renewal, external funding to help support the position is anticipated to be available for up to the duration of LSST construction (8 years), with the potential opportunity for continuation into Survey Operations (10 years). The ideal candidate is an astronomer with strong interest in large surveys, hands-on experience with development of astronomical software, and the potential to lead a highly skilled team. A PhD in physics, astronomy, computer science or a related field is required. Strong C++ and Python skills, and experience with the development and application of image subtraction techniques to large astronomical surveys is preferred. Please send a statement of professional interests, CV, bibliography, and the names of at least three people who may be contacted for letters of reference. Application reviews will begin immediately, and continue through November 30, 2014 or until the position is filled. Documents will be accepted electronically in a single pdf file sent to the attention of Mario Juric, search committee chair, at mjuric(a)astro.washington.edu, with subject line "research faculty application (your name)". The University of Washington is proud to be one of the nation's premier educational and research institutions. Our people are the most important asset in our pursuit of achieving excellence in education, research, and community service. Our staff not only enjoys outstanding benefits and professional growth opportunities, but also an environment noted for diversity, community involvement, intellectual excitement, artistic pursuits, and natural beauty. The University of Washington is an affirmative action and equal opportunity employer. All qualified applicants will receive consideration for employment without regard to, among other things, race, religion, color, national origin, sex, age, status as protected veterans, or status as qualified individuals with disabilities ======== -- Mario Juric, UW Astronomy Faculty | UW eScience | LSST DM Project Scientist Web : http://research.majuric.org Phone : +1 609 933 1033

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