Observations

The observations were obtained using the 0.9 meter f/13.5 reflector at the Warner and Swasey Observatory's Nassau Station in Chardon, OH on September 29, 2001, and October 2, 2001. The CCD used for the observations was a back illuminated thinned SIA-003AB SITe CCD (1024x1024 pixels) with 24 micron pixels. The filter set used was Johnson BV and Cousins RI.

DY Peg

Light curves from pulsating variable stars give information about the structure and evolution of stars in the instability strip. In addition, relationships between the periods of variable stars and their luminosity, in particular the Cepheid period-luminosity relationship, have proved to be useful distance indicators.

DY Peg (RA=23h06m22.s, DEC=+16&# 56' 36'') is a pulsating variable star (type SX Phe) with a period of 0.073 days, a magnitude change of 0.67 (from 9.95 to 10.62), and a change in spectral type from A3 to F. SX Phe stars are metal poor population II stars in the lower region of the instability strip. It was selected as our observational candidate for a pulsating variable star light curve because of its short period and large change in magnitude. DY Peg's change in spectral type will also allow us to construct a color curve for this variable star using observations taken with two different filters.

The data on this object was taken on September 29, 2001, from 9:00 p.m. EDT to 12:00 a.m. EDT. Since the period of DY Peg is 1.752 hours, we should have obtained approximately 2 full cycles of the variable star. Forty-two 30 second exposures with the V filter and fifty 30 second exposures with the R filter were taken. The exposures were taken in sequence alternating between the V and the R filter.

HX Lac

From observations of the light curves of eclipsing binary stars, information about the relative effective temperatures, radii, and masses of the stellar components can be obtained. These systems are recognizable by the distinctive double minimum exhibited in their light curves.

HX Lac is a W Ursae Majoris-type eclipsing variable. These have periods of less than one day, consist of ellipsoidal components, and have light curves for which it is impossible to specify the exact times of the onset and the end of the eclipses. This particular binary was chosen for observation because of its position in the sky (RA=22h 04m 13.0s DEC=+49° 17' 30"), its relatively short period (p=0.5274659d), and its large change in magnitude (from 14.2 to 14.9 in photographic magnitudes).

Observations were made on October 2, 2001, from 8:54 pm to 10:07 pm EDT. With a period of 12.7 hours the entire eclipse could not be observed. Thus, the approximate julian date of a minimum that would occur during this timeframe was calculated from the known julian date of a previous minimum obtained from the literature. A total of fourty-four 35 second exposures were taken using a clear filter. Initially, darks were taken every other frame, but after approximately ten minutes this was changed to every five frames.

NGC 7789

Open clusters are especially useful Galactic objects because each one constitutes a large population of readily observable stars with a very similar evolution and distance from Earth. One of the most convenient and worthwhile means for studying open clusters is through the examination of color-magnitude diagrams, which can provide accurate information about the cluster's age and formation history.

The particular cluster under consideration here is NGC 7789. It is a remarkably rich cluster of stars at RA = 23h 57m and Dec = +56 deg 42.9'. Previous color-magnitude diagrams of this cluster have highlighted a few prominent and interesting characteristics, such as a strong red clump, a distinctive RGB and a documented population of blue stragglers. The relatively large number of stars within this cluster's bounds makes it fairly easy to collect a good statistical sample of stellar magnitudes. These facts, combined with its convenient location in the sky at the time of observation, made NGC 7789 an ideal candidate for the final component of this observing project.

Images of NGC7789 were taken in a 2x2 mosaic collection cycle. In each quadrant of the mosaic, four exposures were taken: a 300 sec V-band and a 200 sec R-band exposure, along with their corresponding dark frames. The four regions of the mosaic were chosen so that they had a mutual overlap section constituting about 20 % of the total area of each quadrant. Since the field of view of the FLI direct imaging camera is about 6 arcminutes across, this setup for the mosaic was sufficient to encompass the roughly 10 arcminute diameter of this cluster.

M27

The planetary nebula, M27, also known as the Dumbbell Nebula, was chosen as a our "pretty picture" candidate because of its large angular size (>348"), and relatively bright luminosity (m_v=7.3). Also, because it is a planetary nebula, this object is a much better candidate for color imaging than, say, an elliptical galaxy.

Observations were carried out on October 2, 2001 from 10:41 pm to 11:44 pm EDT. The nebula was observed in four filters, B, V, R, and I, and both a 30 second and a 5 minute exposure were taken for each filter.