SSP-4 Photometer Observation Report and Analysis #1

This report represents my first set of observations with the SSP-4 (1mm detector). What I have tried to accomplish with this set of observations is to refine my observation technique so that I can make accurate and repeatable measurements. I feel this goal has been accomplished, that is, the SSP-4 photometer is capable of repeatable measurements with a predictable accuracy. I plan to add to this report as I gather more observations. In my next phase of observations I will concentrate on determination of the color transformation coefficients, airmass extinction terms, and the signal-to-noise (SNR) dependence with magnitude.

Table 1 presents the results of differential photometry measurements taken with the Optec SSP-4 (1mm detector). The telescope used was a Meade 0.25m SCT in alt-az configuration. The column labeled “Comp SNR” and “Target SNR” represents the SNR of the comparison and target stars, respectively. The SNR is calculated from the ratio (average counts for n measurements)/(standard deviation for n measurements). The measurements in table 1 have not been corrected for color and airmass differences between the target and comparison stars. The SSP-4 detector temperature is assumed to be -40C unless noted. For some measurements I added a flip mirror mounted to the telescope. The flip mirror functioned as a right angle prism. Adding the flip mirror caused a decrease in the flux by approximately ¾ magnitude. I used the flip mirror to increase the altitude of stars that I could observe. In the “straight through” configuration, that is, without the flip mirror, the SSP-4 will strike the telescope for stars with altitudes approximately 50 degrees or higher.

Table 1 - SSP-4 Differential Photometry

Table 1 Notes

1. Clear, T(amb) = 70F, no flip mirror, averaged over six integrations
2. Clear, humid, T(amb)=80F, with flip mirror, average over seven integrations
3. Clear, ¾ moon, T(amb)=67F, used flip mirror, average over seven integrations
4. Clear, ¾ moon, T(amb)=67F, without flip mirror, average over seven integrations
5. Clear, full moon, T(amb)=70F, without flip mirror, average over seven integrations

Table 2 - Catalog Magnitude for Stars in Table 1

Conclusions:

• Repeatable observations can be taken with the SSP-4.

• Using the 05/12 and 05/15 observations with Spica as the comparison star and SAO 139033 as a target star you obtain for SAO 139033: J = 1.14 +/- 0.05 and H = 0.26 +/- 0.04. The error term is the standard deviation of the mean for seven measurements. These J and H values are within 1.5*error of the published values for SAO 139033. This is reasonable when you consider both catalog J and H magnitudes for Spica and SAO 139033 have an error of 0.05 mag and are both small amplitude variable stars. This also indicates that the color correction terms will be small since these two stars are of very different color.

References:

Gezari D.Y., Pitts P.S., Schmitz M., Catalog of Infrared Observations, Edition 5, 1999, CDS catalog number II/225.

UKIRT Bright Standards, http://www.jach.hawaii.edu/JACpublic/UKIRT/astronomy/calib/bright_stds.html