For questions contact Doug West (dwest61506@aol.com)

View of Orion in visible wavelengths (top) and infrard wavelengths (bottom). Photo courtesy: Akira Fujii (top) IRAS (bottom)

New and Noteworthy

• J and H Band Photometry of Variable Stars (ppt) - Powerpoint presentation by Dr. Doug West and Dr. Matthew Templeton presented at the Mid-American Regional Astrophysics Conference on April 7/8, 2006; University of Missouri - Kansas City
• August 2005 Update - AAVSO Infrared Photometry Progress Report: A Highlight on Eta Aql

Infrared astronomy is an exciting new area of observation and study for the amateur astronomer. The infrared region of the spectrum is typically defined as light with wavelengths greater than 1.1 micron. Human vision ends at about a wavelength of 0.75 micron. Members of the AAVSO and Optec, Incorporated (www.optecinc.com) have worked together to develop the SSP-4 infrared photometer. The SSP-4 photometer is designed to precisely measure light in the J (1.25 micron) and H (1.65 micron) bands. More information about the SSP-4 photometer can be found at http://www.optecinc.com/optec_011.htm .

So why would the AAVSO want to measure variable stars in the J and H band? The infrared bands give information about variable stars that cannot be determined from the visual bands (CCDV or PEP). For example, a Mira type variable star measured in the infrared has a much smaller amplitude of variation. The infrared light curve relates more closely to the actual temperature and radius change of the star as it pulsates. This gives theoretical astronomers a better understanding of the physical processes that occur in pulsating stars. Observations of certain kinds of eclipsing binaries are also very useful because they can help us better determine the properties of binaries. When the stars in the system have very different temperatures, such as in the case of Algol, it is very important to be able to estimate the separate temperatures. In the ultraviolet, the secondary eclipse of Algol is barely detectable but in the IR, it is quite deep, this leads to a more accurate solution. Studies of binaries with spots, such as, the RS CVn and W UMa systems, benefit from IR observations because they enable us to better determine the temperatures of the spots.

Observation in the infrared region of the spectrum has a few advantages over photoelectric photometry in the visual bands. The atmospheric extinction is much less in the infrared when compared to the visual. As a result, differences in airmass between the comparison and target star don't introduce as much error as in the visual bands. In a light polluted city sky the infrared sky is much darker because most of the man made light pollution is in the visible band.

Current Status of AAVSO IR Photometry Group

More Information

• JHK Standards for Small Telescopes - By Arne Henden, JAAVSO, Vol. 31, No. 1, July 2003, pages 11-20.
• Discussion Group for users of the Optec SSP-4 infrared photometer
• Preliminary Results from the AAVSO Infrared Photometry Gruop (3.3 MB pdf) - By M.R. Templeton, J.D. West, D. Terrell, et. al.
• Single Channel Infrared Photometry with a Small Telescope - By Dr. Doug West, WestSkies Observatory, Mulvane, Kansas, USA. Invited talk at the 1st Virtual Meeting on Amateur Astronomy.
• The AAVSO IR Group's list of target star and comparison stars
• Technical reports on initial use and evaluation of the SSP-4 photometer
• A paper presented at the Fall 2005 AAVSO Conference by Doug West, Doug Hodgson, and Ken Luedeke, "Infrared Photometry of Eta Aql"