Star data format explained

Star data format explained

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I am looking for a formal explanation of the following star database format:

Akamar,f|S|A3,02:58:15.696|-44.6,-40:18:16.97|19.0,3.2,2000,0 Menkar,f|S|M2,3:02:16.8|-11.81,4:05:24|-78.76,2.54,2000,0 Mirfak,f|S|F5,03:24:19.37|24.11,49:51:40.25|-26.01,1.8,2000,0 Aldebaran,f|S|K5,4:35:55.2|62.78,16:30:35|-189.36,0.87,2000,0 Rigel,f|S|B8,5:14:32.3|1.87,-8:12:06|-0.56,0.18,2000,0

I know most of the values, but can anyone send me a link to the formal description?

It looks like XEphem's format of databases as described in the manual's file format description. Does the filename end in.edb? That is a common extension for these sort of files. Assuming it is, then the format breaks down as (taking the first line for example):

  • A name (Akamar)
  • A "type designation" for the sort of object, in this caseffor fixed (as opposed to orbital elements or a bound satellite)
  • A subfield for thefixed type indicating it's aStar
  • The spectral type of the star (A3)
  • Right ascension (RA) and proper motion in RA (02:58:15.696and-44.6milliarcsec/year)
  • Declination and proper motion in Dec (-40:18:16.97and19.0milliarcsec/year)
  • Magnitude (brightness) of the object (3.2)
  • Reference epoch for the proper motions (2000.0)


Classified Terran Empire records equated stardate 0141.7 to January 13, 2155

Stardate systems were used in certain cultures as early as the 2150s, when the United Earth government worked with calendar dates. In 2154, Degra, a Xindi-Primate, sent a coded message to Enterprise NX-01 containing a stardate for when Enterprise should rendezvous with Degra's ship. T'Pol knew that it was three days in the future, indicating that Vulcans also had an understanding of stardates at that time. ( ENT : " Damage ") In the late 2250s, the Terran Empire used them to date events of 2155. ( DIS : " Vaulting Ambition ")

By 2164, Starfleet officers would open log entries with a stardate. By 2230, the first four digits stood for the Gregorian calendar year. In the alternate reality of stardate 2258, the Jellyfish gave its manufacturing date as "stardate 2387". ( Star Trek ) This scheme was used in the alternate reality as late as 2263. ( Star Trek Beyond ) By 2256 in the prime reality, a more opaque relationship had been established between stardates and the Gregorian calendar. ( DIS : " The Vulcan Hello ") Variations on this scheme were used as late as 3188. ( DIS : " People of Earth ")

Stardates did not replace clock time or everyday units for expressing larger timespans, such as days, weeks, months, years, centuries, or millennia, and stardate systems tend not to apply retroactively instead of Gregorian or Julian calendars either. ( TOS-R : " The Naked Time ")

How does the STAR method work?

The STAR method helps you create an easy-to-follow story with a clear conflict and resolution. Here’s what each part of the technique means:


Set the stage for the story by sharing context around the situation or challenge you faced. In most cases, it’s best to describe relevant work situations but depending on the amount of directly transferable experience you have, it might also be appropriate to discuss academic projects or volunteer work. It’s also imperative to talk about a specific instance rather than your general responsibilities.

You should spend the least amount of time on this part of your answer as interviewers are more concerned with the actions you took and results you got. Share the right amount of relevant detail by identifying the two or three most important pieces of information necessary to give the interviewer enough context about the situation.

Example: “In my last role as lead designer, there was a point in time when my team was short-staffed and facing a significant backlog of work. The account managers were setting unrealistic deadlines, which was causing stress for my team and affecting morale.”

Describe your responsibility or role in the situation or challenge. In other words, discuss the goal or task set out for you. This section requires a minimal amount of time similar to the situation component. Again, consider just one or two points that best illustrate the task you needed to complete.

Example: 𠇊s a team leader, it was my role not only to ensure my team met our deadlines but also to communicate bandwidth to other departments and keep my team motivated.”


Explain the specific actions you took to handle the situation or overcome the challenge. This part of your answer requires the most in depth description as this is what largely indicates your fitness for a role. Identify and discuss a few of the most impactful steps you took to find success.

Often, workplace challenges are addressed by a team however, it’s a common pitfall to use the word “we” to describe how you achieved your goals during an interview. In any case, it’s important to focus on what you did in the situation. It can be helpful to remember that the employer’s intention is to hire you for the role rather than your team, so you should use the word “I” to highlight your particular contributions.

Example: “I set up a formal creative request process including project timeline estimates to set better expectations. I scheduled weekly meetings with account managers to discuss my team’s bandwidth and share progress updates. I also kept my team informed of the new processes, so they could have some peace of mind knowing the issues were being addressed.”


What was the outcome you reached through your actions? This is also an important part of your response to focus on. You should spend only slightly less time discussing the results than your actions. Decide what the two to three most impressive results were and talk about these.

Quantify your success or provide concrete examples of the effects of your efforts if possible. In addition, discuss what you learned, how you grew and why you’re a stronger employee because of the experience.

Example: 𠇋y providing more transparency into my team’s processes and setting better expectations with the account managers, we were able to re-prioritize the design team’s to-do list and complete everything in our backlog. I took these learnings, continued to apply this structure and as a result, in the following quarter, we shortened our average project timeline by two days. I also learned just how important it is to communicate clearly across teams.”

Star data format explained - Astronomy

This section discusses file formats used by the programs.

Each line of file contains: ra, dec, mag Required. Right ascension, Declination, and magnitude (V or visual). 6 chars for RA, one for sign of DEC, 4 for DEC, 3 for mag. object type Defines what the object is: star, galaxy, cluster, nebula, planet, other, unknown, vector, area, comment, or invisible, with subtypes for each (Two chars). Defaults to type star subtype single. spectral class or color Defines the color of the object, as spectral class for stars or directly for other objects (Two chars). letter or flamsteed number or size Defines either the Bayer letter or Flamsteed number of a star, or the size of an extended object encoded in two chars. constellation The constellation field contains the IAU designation of the constellation the object is in (three chars). name Name or other labeling string. Terminated by comma. comment field Remainder of line after the comma which terminates the name. This comment field may be used for special information about the object, e.g. the phase of the moon.

Magnitude is encoded into three fields as follows: the first character may be a `-' , in which case the next two characters are the magnitude times 10, e.g. `-16' means `-1.6' . The first character is a digit, the three characters are the magnitude times 100, e.g. `563' means `5.63' . Finally, if the first character is a capital letter, this is taken as the base-36 value of the integral part of the magnitude, and the remaining two characters are the fractional part times 100, e.g. `B34' means `11.34' .

The Bayer letter or Flamsteed numbers are applicable only to stars. The field is two characters wide. Greek letters are a single lowercase letter followed by a space or a number, encoded as in the PostScript Symbol font:

the original definitions, which were @, E, 0, x, and % respectively.

An uppercase letter followed by any character or two non-numeric characters is the roman letter designation for the star, e.g. `CY' . Two numbers or a space and a number is the Flamsteed number of the star.

The size of nonstellar objects is encoded in seconds of arc in the size field to two significant digits. The second character is always a decimal digit. Sizes from 0 to 99 arc seconds are encoded as two decimal digits. For larger objects the first character is a capital letter, interpreted as follows, with the second character as the next digit:

The types and subtypes implemented are:

The magnitude of an object determines what information is displayed. Three magnitude limits are defined for each file in each map window. If the magnitude is greater (dimmer) than the first limit, nothing is drawn. If the object is brighter than a second limit, the label (Bayer or Flamsteed) is printed (if present). If it is brighter than the third limit, the name is printed (if present if not, the label is printed if present). These text strings generally appear to the right of the object, but the driver can change this. Note: the label string only applies to stars.

For nonstellar objects, the label field defines the size of the object in arc seconds.

For magnitudes within a range defined for the mapwindow, a magnitude tag, the magnitude to one decimal place as in variable star and asteroid finding charts, may be displayed. This will generally be below and to the right of the object, but this is controlled by the driver.

The symbol drawn for the object is determined by the type field.

For devices supporting color, the spectral class or color field defines the color of the object, and perhaps the associated text. The spectral class of stars is mapped to display color, and for other objects, this field may contain direct color specifications, e.g. 'r3' for an object colored red level 3. All this is controlled by the device driver. Standards for color definitions are yet to be defined.

The constellation field is not currently used in the display.

The comment field is also not generally used, but some drivers may use it to contain special information such as the phase of the moon or position angle of a comet's tail.

This text format, called , is the original data file format. Data for each object is on a single line, stored in character fields. Currently, an older variant is also supported, one which has 4 characters for the magnitude and omits the color and letter/number fields. Both of these formats are designated as type , since each line is read individually and these two types are easily distinguished on a line by line basis. In all formats, if a value is unknown, it should be spaces, or a null string in the case of the name and comment fields. The RA, DEC and mag. must always be provided for an object.

Since it is a text format, it may be mailed safely and be used on many different computer architectures without change. However, it is slow, and uses more file space than it ought.

The format was introduced to allow data to be exchanged as text, with greater precision in the location and magnitude fields, and greater readability compared to the format. The format is too slow for use as input to the starchart programs. A data conversion program is provided to convert between formats, and to precess coordinates during the conversion.

Each object is represented by a single line in the file. This line contains fields each of which corresponds to a field in the format. The fields are separated by a single character, usually `' . Fields may be omitted from the end of the line omitted fields are assigned their default values. Fields may be empty, and again are assigned their default values. As with the other formats, the RA, DEC, and mag. must be present.

The RA may be given as a decimal hour, hour and decimal minute, or hour minute and decimal second. The DEC may be given in the same format. The magnitude is a floating point number.

The type, and color, fields are empty or one or two characters, as in the format.

The label field is also the same as in the format, and encodes the size of non-stellar objects in two characters. There is a bit of "magic" in this field. Since `X ' or ` X' are both valid, and whitespace is normally ignored, iff this field is two characters wide, and both characters are printing characters, it is taken verbatim as the label field. That is, `. X . ' is ` X' , while `. X . ' is read as one character and left justified to become `X ' .

The constellation field is the IAU abbreviation for the constellation and is always blank or three characters.

The name and comment are two separate fields. Commas should not be used in the name field, since when this name is placed in the other formats a comma is used to separate the name from comments.

Three binary input formats are supported. These formats provide greater position and magnitude accuracy, with faster input, and varying degrees of storage space reduction. The files are inherently unportable, however, and should not be exchanged between machines and operating systems, or even different compilers. The format, described above, provides a general data exchange format.

The three formats provide different storage sizes. The most general format, which contains all the data in the format, is the format. A smaller format, stores only the RA, DEC, mag. and object type fields, all other fields become their defaults (usually spaces). The smallest format, stores only the RA, DEC and mag., all other fields become their defaults, notably the object type is `SS' .

The binary formats are described as C structures. How the data in the structure is stored is therefore highly variable between compilers, operating systems and machines. However, most machines should be able to take advantage of these formats for local storage.

The Hubble Space Telescope Guide Star Catalog, available on 2 CD-ROMs, may be used as a stellar database. This format may be read by dataconv and the starchart programs, but now written. An index file is used to specify which files on which CD-ROM should be read.

The file is a special file format added to support larger databases of dimmer stars. It provides an index mapping location to filenames of files containing star data as above. Each indexed file covers a rectangle of sky in RA and DEC. The areas may be different sizes for different files. The area covered is given as the RA and DEC of the upper left and lower right corners, followed by the filename and a string indicating the type of the file. This is all on one line in the file. The format is then:

Overview of the FITS Data Format

A FITS file consists of one or more Header + Data Units (HDUs), where the first HDU is called the `Primary HDU', or `Primary Array'. The primary array contains an N-dimensional array of pixels, such as a 1-D spectrum, a 2-D image, or a 3-D data cube. Five different primary data types are supported: unsigned 8-bit bytes, 16 and 32-bit signed integers, and 32 and 64-bit single or double precision floating point reals. FITS can also store 16 and 32-bit unsigned integers.

  • Image Extension - a N-dimensional array of pixels, like in a primary array
  • ASCII Table Extension - rows and columns of data in ASCII character format
  • Binary Table Extension - rows and columns of data in binary representation

Each header unit consists of any number of 80-character keyword records which have the general form:

KEYNAME = value / comment string

The keyword names may be up to 8 characters long and can only contain uppercase letters, the digits 0-9, the hyphen, and the underscore character. The keyword name is (usually) followed by an equals sign and a space character (= ) in columns 9 - 10 of the record, followed by the value of the keyword which may be either an integer, a floating point number, a character string (enclosed in single quotes), or a boolean value (the letter T or F).

The last keyword in the header is always the `END' keyword which has no value or comment fields. There are many rules governing the exact format of a keyword record (see the FITS Standard for details) so it is generally better to rely on standard interface software like CFITSIO to correctly construct or parse the keyword records rather than directly reading or writing the raw FITS file.

Each header unit begins with a series of required keywords that specify the size and format of the following data unit. A 2-dimensional image primary array header, for example, begins with the following keywords: The required keywords may be followed by other optional keywords to describe various aspects of the data, such as the date and time of the observation. Other COMMENT or HISTORY keywords are also frequently added to further document the contents of the data file.

The data unit, if present, immediately follows the last 2880-byte block in the header unit. Note that some HDUs do not have a data unit and only consist of the header unit.

Return to main FITS page. Page Author: William Pence
Last update: Tuesday, 26-Jan-2021 14:30:43 EST

My God! It's Full of Stars!

A great all-around set of star data is the HYG Database. This incredibly useful dataset was created by David Nash by merging the Hipparcos Catalog, the Yale Bright Star Catalog (5th Edition), and the Gliese Catalog of Nearby Stars (3rd Edition), then weeding it down to useful size. This database contains ALL stars that are either brighter than magnitude +7.5 or within 50 parsecs (about 160 light years) from the Sun, a total of 31,859 stars. It is in Comma Separated Value (.csv) format, which most spreadsheets and database programs can import. If you want quality data but are unwilling to do the drudge work, this is the dataset to use!


Scientists Jill Tarter and Margaret Turnbull have compiled a massive dataset of nearby stars that it is not impossible for them to host habitable planets. Note that "habitable" does not necessarily mean "human habitable". They winnowed down the 120,000-odd stars in the Hipparcos dataset into 17,129 prime stars. Seventy-five percent are within 140 parsecs (450 light years). Please note that while they have removed all stars incapable of hosting a habitable planet, the remaining stars in the database are not guaranteed to have such a planet. The stars in the database are those "worthy of a closer look."

The HabCat dataset is available here in a Zip archive. The un-zipped dataset is in CSV format. The columns are Hipparcos catalog number, Right Ascension (in the form HH MM SS), Declination (in the form +-DD MM SS), Apparent Magnitude, Parallax in milliarcsecs (parsecs = milliarcsecs/1000), error in parallax, B-V color index, error in color index, CCDM catalog number (CATALOGUE OF COMPONENTS OF DOUBLE AND MULTIPLE STARS), HD catalog number (Henry Draper), and BD catalog number (Bonner Durchmusterung). Here is a re-print of the article describing the methodology used.


HabHYG is a dataset I whipped up myself. It is basically the HYG database merged with the HabCat database. Beware that errors might have crept in, serious researchers should go back to the primary sources. The file is a Zip archive of a CSV format file. Note that there is only one entry for each star system, the extra stars in binary and trinary star systems are not shown.

The fields are HabHyg index (a number I invented to ensure that each entry had a unique number associated with it), Hipparcos catalog number, Habitable? flag (1 = habitable), Star Display Name (of all the names of this particular star, the one that I found personally the most asthetically pleasing), Hyg catalog number, Bayer-Flamsteed name, Gliese catalog number, BD catalog number (Bonner Durchmusterung), HD catalog number (Henry Draper), HR catalog number (Hoffleit Bright Star), Proper Name (e.g., "Sirius"), Spectral Class, Distance from Sun in parsecs, Galactic cartesean co-ordinates (epoch 2000) Xg/Yg/Zg in parsecs, and Absolute Magnitude.

Internet Stellar Database

For a comprehensive look at the nearer stars, you cannot beat the incredible Internet Stellar Database. This site will allow you to look up all manner of star data, with explainations. And the 3-D co-ordinates are already calculated for you!

Encyclopedia of Suns

The Armchair Astrometrist has a great list of Encyclopedia of Suns gleamed from the Hipparcos data.

Research Consortium on Nearby Stars

Here is an up-to-date list of the 100 nearest stars, courtesy of the Research Consortium on Nearby Stars.

Bright Star Catalog

Here is a list of the Fifty Nearest stars and a list of the Fifty Brightest stars compiled by CosmoBrain.

Gliese Catalogue of Nearby Stars

Users of Windows Vista (and later) and Mac OS X v10.3 (and later) can use their operating system's built-in archive utility.

Info-Zip is free and available on a wide-range of operating systems, including MS-DOS, Windows, Mac, and Amiga.

The GNU project offers gzip (GNU zip) which is also available for multiple operating systems.

If those don't do it, there are many more options available.

Warning for IBM users: PKZip 3.00G is a Trojan Horse program that will destroy your hard drive!

The Gliese Near Star catalog is the standard reference work for budding young starmap makers. It contains all known stars within 25 parsecs (81.5 light years). Version 2.0 was compiled in 1969, while version 3.0 was done in 1991. Naturally 3.0 has more stars, about half again as much.

Here is version 2.0 (about 96K) and version 3.0 (about 244K). These are PKZip compressed format files, and contain both the data and the docs.

Otherwise, the Gliese near star catalog 3.0 is available as a Gnu Zip (i.e., Gzip) file from the Strasbourg Astronomical Data Center. Decompress with one of the Gzip programs mentioned to the right, or WinZip. Be sure to also get the documentation, as it explains what data is in what column. Just to make things annoying, that changed from version 2 to version 3.

Tero Niemi has a pre-processed datafile of the Gliese catalog here. It will save you a lot of effort.

Terry Kepner pointed out that one cannot accept all the Gliese data without question, specifically the parallaxes . It states quite clearly in the documentation that some of the parallaxes are based on photometric readings, not on triangulation. Some stars are included even though they are known to be farther away than the photometric readings would indicate. And other stars are not listed even though they are known to be closer than their photometric readings.

Mr. Kepner says as a rule of thumb all measurements in astronomy are good only to the first two decimal places with distances under about 100 light years, and every measurement is plus or minus 50% with distances above 100 light years.

Mr. Kepner goes on to state that the French are running a massive collection of data regarding distances from a satellite (Hipparcos) that has been gathering data on 100,000 stars over the last ten years. They expect to have the most accurate distance database ever in another year or so. Being based on a satellite, without the Earth's atmosphere to interfere with delicate instruments, the data is already much better than anything measured from the ground. Sadly, the survey is limited to stars brighter than 12th magnitude, so many nearby red dwarfs will be missed.

Measurement re-reduction

The BAA VSS database has the unique ability to re-reduce magnitudes. This is immensely useful when sequence magnitudes are updated with improved photometry. This is made possible by two critical factors: the database records both the full magnitude e.g. “b(2)v(3)c”, and the sequence magnitudes. This means that observations spanning many years using different sequences can be re-reduced to give results based on the same modern sequence of magnitudes. This capability is built into both the visual and CCD databases, though it does rely on observers submitting the full estimate and not simply a magnitude, a requirement insisted upon by the VSS.

SIMBAD Astronomical Database - CDS (Strasbourg)

The purpose of Simbad is to provide information on astronomical objects of interest which have been studied in scientific articles.

Simbad is a dynamic database, updated every working day.

It provides the bibliography, as well as available basic information such as the nature of the object, its coordinates, magnitudes, proper motions and parallax, velocity/redshift, size, spectral or morphological type, and the multitude of names (identifiers) given in the literature. The CDS team also performs cross-identifications based on the compatibility of several parameters, in the limit of a reasonably good astrometry.

Simbad is a meta-compilation built from what is published in the literature, and from our expertise on cross-identifications. By construction it is highly inhomogeneous as data come from any kind of instruments at all wavelenghts with any resolution and astrometry, and different names from one publication to another.

Simbad is not a catalogue, and should not be used as a catalogue. The CDS also provides the VizieR database which contains published lists of objects, as well as most very large surveys. The idea now is to use both Simbad and VizieR as completary research tools.

What is SIMBAD ?
basic search
by identifier
by coordinates
by criteria
reference query
TAP queries
Display all user annotations
User's guide
Query by urls
Nomenclature Dictionary
Object types
List of journals
Measurement description
Spectral type coding
User annotations documentation
Image thumbnails

BETA - Mobile version

SIMBAD4 1.7 - May-2018
Release history

The SIMBAD astronomical database provides basic data, cross-identifications, bibliography and measurements for astronomical objects outside the solar system.
SIMBAD can be queried by object name, coordinates and various criteria. Lists of objects and scripts can be submitted.
Links to some other on-line services are also provided.

Basic search
If the Simbad database was helpful for your research work,
the following acknowledgment would be appreciated:

This research has made use of the SIMBAD database,
operated at CDS, Strasbourg, France

2000,A&AS,143,9 , "The SIMBAD astronomical database", Wenger et al.

Simbad contains on 2021.06.24
12,117,356 objects
41,672,622 identifiers
390,265 bibliographic references
24,690,884 citations of objects in papers
14,914 acronyms described for Simbad

SIMBAD on the Web is the WWW interface to the SIMBAD database. It offers the following functionalities:

How to Prepare for an Interview Using STAR

Since you won’t know in advance what interviewing techniques your interviewer will be using, you’ll benefit from preparing several scenarios from the jobs you’ve held.

Make a List of the Job Qualifications

First, make a list of the skills and/or experiences that are required for the job. It may help you to look at the job listing and similar job listings for indications of the required or preferred skills/qualities and match your qualifications to those listed in the posting.

Create a List of Examples

Then, consider specific examples of occasions when you displayed those skills. For each example, name the situation, task, action, and result.

Match Your Skills to the Job

Whatever examples you select, make sure they are as closely related to the job you’re interviewing for as possible.

You can also take a look at common behavioral interview questions, and try answering each of them using the STAR technique.

F | Physical and Orbital Data for the Planets

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