1,656 reputation
615
bio website linkedin.com/in/neilsen
location Illinois
age 44
visits member for 3 years, 9 months
seen yesterday

Astronomer and software developer with interest and expertise in sky surveys, observing strategy and efficiency, data science, open science, and image processing.


Jul
14
answered Why is the universe so organized?
Jul
2
comment What are the easiest ways to get data out of a FITS file without a library?
The hexdump recipe I gave works just fine for headers of extended HDUs (I assume that's what you mean by subheaders). You just need to scroll past the data. Note that FITS requirements on the arrangement of the data mean that the header data cards of subsequent headers will line up correctly.
Jun
29
comment Standards for scientific metadata in common-use image formats?
The exceptions I refer to are compression and heaps. I personally find the growing use of the compression features of some libraries before they are properly documented foolishly short-sighted: I want a proper published standard.
Jun
29
answered Standards for scientific metadata in common-use image formats?
Jun
28
comment What are the easiest ways to get data out of a FITS file without a library?
Of course on my own system I use appropriate tools (ds9, fv, TOPCAT, pyfits), but I also want to be able to write a bash script I can hand to someone and reasonably expect to work without any additional effort. Maybe I should just expect that everyone will have a python interpreter, at least.
Jun
27
comment What are the easiest ways to get data out of a FITS file without a library?
The FITS standard specifies big endian. Some formats that used to be used by IRAF were very close to FITS, but were machine dependent. Some raw files that were produced by the SDSS data acquisition system were little endian, and used a "SIMPLE=FALSE" keyword assignment to indicate that they were not purporting to be real FITS.
Jun
27
comment What are the easiest ways to get data out of a FITS file without a library?
Other file types (ASCII tables and images) should be slightly easier. FITS heaps are pretty much impossible without lots of code, and fortunately obscure anyway.
Jun
27
comment What are the easiest ways to get data out of a FITS file without a library?
The sample file I used can be found here.
Jun
27
answered What are the easiest ways to get data out of a FITS file without a library?
Jun
27
asked What are the easiest ways to get data out of a FITS file without a library?
Jun
25
answered How can one predict the length of the Synodic month? Why is it irregular?
Jun
24
answered What is the simplest way to prove that the Earth orbits the Sun?
Jun
18
comment Why don't we have a better telescope than the Hubble Space Telescope?
The size issue is the mirror. JWST's mirror consists of multiple segments, but this is technically challenging.
Jun
18
answered Why don't we have a better telescope than the Hubble Space Telescope?
Jun
17
comment When taking a sequence of exposures for stacking/coaddition, what dither patterns are most commonly desired? Why?
Good, general response; I would just add that, in addition to needing dithering to cover bad pixels, you also need it to cover gaps between detectors when your camera has a array of detectors (eg CCDs) rather than just one.
Jun
17
accepted When taking a sequence of exposures for stacking/coaddition, what dither patterns are most commonly desired? Why?
Jun
17
answered How long would it take to scan the visible universe for unique signals?
Jun
16
answered Recommend good book(s) about the “scientific method” as it relates to astronomy/astrophysics?
Jun
13
comment What do the colors in false color images represent?
I don't think "false colors" implies that the colors were "added by computer", only that they do not represent the exact same colors the eye would see, which is correct. I do not know how well color photographic film really matches the human eye, but I do expect that it is much closer than, say, Johnson BVR. However, I suspect that such film is uncommon in images in contemporary publications, which are probably mostly Johnson B/V/R, SDSS g/r/i, or some set of HST filters (F430W + F555W + F814W?). For emission line objects, sometimes the difference can be dramatic.
Jun
12
answered What do the colors in false color images represent?