The UIS Barber Luminous Stars Survey of M31 and M33 is the longest running continuous multi-filter survey of both the Andromeda Galaxy (M31) and the Triangulum Galaxy (M33).
This survey was innitiate und NSF grant AST- 1108890. In 2012, we began surveying the two nearby galaxies M31 and M33 to keep tabs on the most luminous stars in those galaxies. The evolutionary state of most of these stars is clearly post hydrogen fusing main sequence. They may become supernovae or supernovae imposters sometime in the near future and the pre-explosion record from this survey and others will be critical for interpeting that eventbecause their path from main-sequence to terminal state (death) is unclear. This survey endeavors to develop a baseline of data complimentary to other surveys that can be used to disentangle the evolutionary state and history of the most luminous stars.
It would be difficult to do a similar survey to any level of completeness in our own galaxy. Nearby face-on spiral galaxies, M31 and M33 are oriented in a way where we can study most of the galaxy unobscured and use what we learn to build a holistic picture of a galactic population of luminous stars. This can in turn help astronomers better interpret the stellar population in the Milky Way.
John C. Martin is the principle investigator responsible for this survey. Roberta Humphreys is a key collaborator and advisor who mantains a spectroscopic database of the targets at the University of Minnestoa.
This is a target survey. Photometry for the targets is fully currated and checked by humans. The targets for the survey fall into four main categories:
If you have a favorite target in M31 or M33 that does not appear on our list, please contact us. While the survey is currated for these targets, we save the photometry measured for every star imaged down to a reasonable SNR. We can make this data availble for use through a queriably SQL database.
The survey is conducted using a 20-inch F/13 cassegrain reflecting telescope with aluminum coated mirrors. The telescope is located at a dark site (Bortle Scale 4) about 20 miles north-northwest of Sprinfield, IL (out from under the city light dome). The field of view on the images is roughly 20 arcminues by 20 arminutes with a plate scale of roughly 0.6 arcseconds per pixel.
Between 2012 and August 2025, the survey was conducted using an Apogee U42 camera with a back-thinned and back-illuminsate 2048x2048 pixel E2V CCD42-40. In August 2025 the camera controller onboard the U42 had an unrecoverable failure. Finger Lakes Instrumentation was contracted to build a new camera around the E2V CCD42-40 chip. The new camera with the same imaging chip was put into service in January, 2026.
Imaging is conducted each year between August and Februrary using the UIS Research Observatory 20-inch Telescope. The fields in the survey may change from year to year because they are optimized to complete a survey of the targets in the fewest number of exposures. The fields cover most of M33 but they only partially cover parts M31 with targets of interest.
The goal of the survey is to image each target in multiple filters at least once per observing season. In some cases imaging might occure as frequently as once a month for some targets. Each epooch of imaging includes one Johnson V image and at least one other filter.
The goal of the survey is to provide photometric monitoring to a precision of at least 10% down to 20th magnitude.
The survey uses standard Johnson-Cousins high-throughput filters manufactured by AstroDon. Every epoch is imaged fully in V and either B or R. Later epochs are imaged in B, V, R, and Ic. Photometric comparison stars are selected from APASS. Detailed information about the photometric comparison stars can be found on a separate page on this site. K corrections and standard photometric color transforms are determined for the instrumental system through imaging of M67.
Photometric reduction are performed using an automated pipeline built around IRAF DAOphot PSF fitting photometry package. The survey uses PSF fitting photometry because crowding (particularly in M33) make it difficult to do uncontaminated aperture photometry for fainter targets. The pipeline standardizes the selection of stars used to build the PSF for each image. Initial testing showed that DAOphot outperformed other PSF photometry packages for the images in this survey. The pipeline performs PSF fitting photometry consistent with aperture photometry down to the 5-10% level.
Please reference the following paper when using materials from this survey:
"Multi-epoch BVRI Photometry of Luminous Stars in M31 and M33" by Martin & Humphreys in the 2017 Astronomical Joural (Volume 154, pp. 81)Here is a link to the entry for the article at the NASA Astrophysical Data System (ADS).
Please also acknoledge the survey in the following way:
This work makes use of the University of Illinois Springfield M31 and M33 Luminous Stars Survey which is made possible by the Henry R. Barber Astronomy Research Endowment.
By John C. Martin, University of Illinois Springfield Henry R. Barber Research Observatory
Last Updated on 2026-Jan-19 UT-6