Spacebuzz

Blog posts tagged with data

Posts in the past four weeks

Friday
Feb 14 2014
17:04 UTC

APOD Linked Data

... the Day (APOD) and data formats so if neither of those interest you feel free to look at a pretty picture of a nebula instead. Since 2007 I've been running the @apod Twitter account. Since the US government shutdown of October 2013 I've been providing an APOD search engine too. As a result I have put some effort into parsing the content of every APOD since 1995 and have them in a big file split into fields such as date, title, author, des

Posted by Astronomy Blog

Thursday
Feb 13 2014
04:59 UTC

intensity vs flux bug

... spent some quality time with Ekta Patel tracking down a bug in our visualization of output from The Tractor. In the end it turned out to be a think-o (as many hard-to-find bugs are) in which I had put in some calibration information as if it calibrated flux, when in fact it calibrates intensity. The flux vs intensity issues have got me many times previously, so I might learn it some day. As my loyal reader knows (from this and this, for example) I feel very strongly that an astronomical ima

Posted by Hogg's Research

Friday
Feb 07 2014
04:59 UTC

reading student work on exoplanets and lensing

In a small amount of research time today, I read various bits of writing from students. Leslie Rogers's (Caltech) student Ellen Price (Caltech) has written a very nice paper about Fisher Information in exoplanet transit observations. I am going to recommend to them that they make the paper more useful to experimental design by specifically accounting for the differences between photon noise and read noise, the latter penalizing you for taking shorter exposures. I say this because their ma

Posted by Hogg's Research

Wednesday
Feb 05 2014
04:59 UTC

the Kepler PSF

... Kepler pixel-level data. The idea is to make a slightly more flexible model for the PSF than what the Kepler team has created, permit variation in stellar centroid (from exposure to exposure) and detector sensitivity (from pixel to pixel) and see if that—plus some super-fast optimization with ceres—can crush this.

Posted by Hogg's Research

Tuesday
Feb 04 2014
04:59 UTC

better photometry for Kepler

Because Hou has finished and submitted his paper on the (apparently aptly named) FML, today's MCMC meeting devolved into a discussion of how Kepler does its simple aperture photometry (or SAP, if you like the acronym circus). By the end of the meeting, we had formulated a question in fundamental astronomy which I am not sure has been answered in the literature: If you know your point-spread function (PSF or pixel-response function or PRF or pixel-convolved point-spread function or PCPSF) p

Posted by Hogg's Research

Friday
Jan 31 2014
04:59 UTC

rebuilding a model

... have for a pixel-level data-driven model for the Kepler imaging. We debated the question of fixing or rebuilding (from scratch) Foreman-Mackey's code (written to make the demo in our whitepaper). Since the model is linear in everything, we decided that rebuilding from scratch would be straightforward and probab

Posted by Hogg's Research

Thursday
Jan 30 2014
04:59 UTC

sampling in galaxy shape space

Lang and I pair-coded (although really Lang coded and I stared at the terminal) two extensions for The Tractor today, both related to our hierarchical weak lensing project (now called MBI) with Bard and Marshall and Schneider and Dawson and others. In the first, we extended our mixture of Gaussians approximations to standard galaxy profile to general Srsic indices; this requires some optimizations, running now in the background. In the second, we built something (that Lang wants to call "Tro

Posted by Hogg's Research

Tuesday
Jan 28 2014
04:59 UTC

observing and fitting streams of stars

... spent the day up at Columbia, visiting Johnston's group and also Geha and Bonaca came down from Yale. We discussed all things tidal streams, including recent papers by Sanders and by Bovy (streams are the new exoplanets?). We noticed that some things in those papers might be in one or two old papers by Johnston and by Helmi. Will do due diligence on that soon. One thing I don't like about these recent papers is that they are very tied to the action–angle formalism, which requ

Posted by Hogg's Research

Friday
Jan 24 2014
04:59 UTC

likelihood functions

... based on the observed (data) intensity (standard practice for lots of optical astronomy, including many of my own SDSS papers). On the latter, Marshall asked me to write up my

Posted by Hogg's Research

Thursday
Jan 23 2014
04:59 UTC

weak lensing

... had two telecons today. The first was with Phil Marshall, to discuss my Atlas project, which needs some love and attention. Phil had lots of good ideas for improvements that make it more fun and more useful. In the second I joined a meeting with Marshall's GREAT3 team, which is getting ready to compete in the upcoming weak lensing competition. The team includes Lang, who is operating the farm machinery required. We discussed the importance of having an explicit (and good) prior over g

Posted by Hogg's Research

Wednesday
Jan 22 2014
04:59 UTC

hierarchical inference of exoplanet densities

... optical) radii. The data on these tiny planets (especially the masses) are extremely noisy, so she used hierarchical infe

Posted by Hogg's Research

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