MSUM Archive of the MAPS Catalog - Frequently Asked Questions
(The MAPS Project website maintains it's own Frequently Asked Questions list. Consult it if you have questions about the MAPS Catalog itself, this FAQ covers issues exclusive to the MSUM Archive of the MAPS Catalog.)
This is not intended to be a substitute for the actual documentation, which includes detailed information on photometry, astrometry, and object classification. Rather, this page has sample replies to often-heard comments about the online catalogs.
Questions we have answered on this page:
- Is the MSUM Archive associated with the MAPS Project?
- Any differences between the MAPS Project version of the MAPS Catalog and the MSUM version?
- Why are object queries in Galactic coordinate so much slower than in B1950 or J2000?
- Is the MSUM Archive associated with the
MAPS Project? [back to top]
The MSUM Archive of the MAPS Catalog is an independent research project by me, Juan Cabanela, an associate professor of Physics and Astronomy at Minnesota State University Moorhead (it was originally developed when I was at Saint Cloud State University). I was one of the creators of the original MAPS Catalog and had been interested in getting a local version running for use by the MSUM observatory as well as for my own research.
With that said, the folks at the MAPS Project have been very helpful in letting be grab some of their code and documentation for this site. Although most of the MySQL development ended up using code I had on hand, I didn't know any PHP before this project started and am grateful to Matt Gray of the MAPS Project for his help in providing me with useful code to start with.
- Any differences between the MAPS Project
version of the MAPS Catalog and the MSUM version? [back
Originally this project was started because I wanted to "extend" the MAPS Catalog with parameters useful for my research. However, as time went on, the folks at the MAPS Project liked what they saw in this website and we merged our code bases so that both sites offer identical features for the most part. I may add some additional features as time goes on, for example, I am currently working on:
- True "circular" query areas, so you can ask for all the objects within X arcseconds of the position queried. Angular separation will also be an acceptable output variable. [About 90% done as of March 21, 2005]
- Why are object queries in Galactic coordinate
so much slower than in B1950 or J2000? [back to top]
In a nutshell, this is because the POSS I plates were shot with their boundaries roughly aligned to the celestial equator and not the the Galactic equator. Therefore the "limits" of POSS I fields in Galactic coordinates tend to be much broader. Therefore, when the software checks which POSS I fields have limits encompassing a given sky box, there will often be POSS I fields matched that do not actually overlap the given sky box even though the "limits" of that POSS I field in Galactic coordinates.
If the field is large enough (many degrees in width), queries in Galactic coordinates should not be much worse than those in B1950.0 or J2000.0.