The only way things work is to use the same measuring aperture for the target as you do for the comparison, as then you are measuring the same fraction of each star's profile and you get an accurate differential measure. Your measure cannot be compared with someone else (there will be an offset), and if you use different aperture sizes on the next night, your next measure can't be compared with the first since you would have a different offset. If you use a different measuring aperture between the target and the comparison star, then you are measuring different fractions of total light and the magnitude difference will change. It also means that, as you increase your measuring aperture, you continue to increase the star signal as you are capturing a larger fraction of its total light. noise that sweet spot is different for different brightnesses of stars as the relative contribution of the sky background changes. There is a sweet spot where you maximize signal vs. You want the maximum signal (large aperture) but with the minimum sky background included (small aperture). This means that setting measurement apertures is a compromise. Back in the 1970's, we measured star profiles out to several degrees. ![]() Basically, the star profile never ends - think of the Sun and how far its light spreads. Some of the spreading of light is due to the atmosphere some is due to the optics, mount tracking, etc. However, multiple queries may be submitted sequentially, even if one or more queries are still executing.Remember that a star is not a point source, but instead has a profile. Most queries are limited to a single object or position, except for searches by observation ID.The results of a search of Virtual Observatory collections may have arbitrary limits on the number of rows returned, on a resource-by-resource basis (i.e., limits which may imposed by the collection provider).The maximum allowed search radius is limited on a collection-by-collection basis.All coordinates are interpreted as J2000. ![]() M51 and M 51) are ignored unless the space is significant in the name. Object names are not case-sensitive, and spaces between the characters (e.g.For example, M5 returns results for object Messier 005. Leading zeros are ignored in the name.When formulating a search, note the following: Search for multiple observations by id: a TESS and HST observation See the table below for examples of various custom search radius inputs. Note that some collections have search radius limitations. The default cone search depends on the size of the object but is usually 0.2 degrees for most targets. Specify the Search RadiusĪ custom search radius can be specified by appending to the coordinates r=, where number is any valid decimal number and unit is one of "d" (degrees), "m" (arc-minutes), "s" (arc-seconds). A cone search is performed around the input coordinate at a default radius of 0.2 degrees. Right ascensions must be positive and southern declinations require a leading negative sign. Coordinates can be given in a variety of formats. Users can search for data by providing a target on-sky coordinate of Right Ascension (RA) and Declination (Dec). Other catalogs with coordinate and decimal symbolsĪll-sky satellite catalogs with restricted symbols Objects from standard catalogs such as Messier and NGC will be resolved Allowed FormatĪllowed formats for target names are the following: ![]() A wide variety of catalog and common names can be resolved to known objects. Names of objects are passed to a NED or SIMBAD name resolver, which associates known object names with sky coordinates. Users can search for data by inputting the astronomical name of a target object on the sky. Search for JWST data by instrument that match a selection of header keyword values. Search for MAST data associated with a Digital Object Identifier. Libraries of observed, reference point-sources for higher-precision photometry and astrometry. MAST-held collections of source lists, e.g. ![]() Hubble Spectroscopic Legacy Archive (HSLA)Ī collection of spectra housed in the Hubble Legacy Archive. These include HST, JWST, Kepler, GALEX, EUVE, FUSE, IUE, SWIFT, and several other missions.Ī worldwide collection of repositories providing astronomical images, catalogs and spectra.Ī catalog of tens of millions of sources from the Hubble Legacy Archive (HLA), derived from HST imaging in multiple instruments and passbands.Ī collection of spectra associated with sources in the HSC. The combined observations from all MAST collections.
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