Introduction
When making observations with the UMBC Observatory, we have to account for the limitations of our observatory, given that we are looking through an atmosphere, located around Baltimore, and have imperfect equipment. Because of this, we must properly understand the effects of these factors on our observations, and develop pipelines to correct for said factors. One standard metric for ground based observatories is the limiting magnitude, which defines the faintest celestial objects we can reasonably expect to detect on a given night. This metric is often calculated by observing dim sets of stars, and seeing how accurately we can calculate their relative magnitudes.
This is tested against a set of photometric standards outlined in a series of papers by Dr. Arlo Landolt. These papers present constant star fields and their associated Johnson magnitudes. Given data from these photometric standards, we seek to develop a pipeline that transforms our observations into calibrated sets of “data reduced” frames. The first step to utilizing this pipeline involves taking calibration frames – which seek to isolate possible sources of unwanted signals arising from our optical system such as thermal noise, electronic bias, or inhomogeneities. Additionally, we need to make observations of these star fields at a high enough signal to noise ratio (SNR) such that we maintain confidence in any derived results. Due to the dimness of these star fields, it is vital that we are able to differentiate between our background and the sources in the star fields.
With the calibration frames and star field observations, we can use a software pipeline to calculate instrument magnitudes – a relative value that is dependent on our location and equipment. After this, we can account for the effects of our atmosphere, and translate our measurements to the Johnson System of stellar magnitudes. From here, we can compare our calculated magnitudes to those published by Landolt, noting at what limiting magnitude our values begin to diverge from the reported values. With a validated data reduction pipeline, the UMBC Observatory gains the ability to calibrate and observe stellar sources outside of relative measurements, which can be used in future photometric studies, classes, and training.
Author: Olivia Chiarini
Editor: Jacob Rubinstein
Date: 20241001