A single-photon counting astronomical spectrophotometer.

Area of Science:

• Astronomy and Astrophysics
• Optical Instrumentation
• Spectroscopy

Background:

• Traditional spectrophotometers using current measuring photometry have limitations in information acquisition rates.
• Advancements in photon-counting technology offer potential for enhanced sensitivity and data throughput in astronomical observations.

Purpose of the Study:

• To modify an existing spectrophotometer to incorporate single-photon counting capabilities.
• To evaluate the performance of the modified instrument for astronomical spectroscopy, focusing on sensitivity and resolution.

Main Methods:

• Modification of a spectrophotometer to enable single-photon counting.
• Implementation of precise guiding mechanisms to minimize wavelength shifts during spectral scans (±0.1 Å).
• Testing the instrument's performance at McDonald Observatory using the 208-cm Struve reflector.

Main Results:

• The modified spectrophotometer demonstrated successful observation of faint objects (m(p) = 15.3) with a resolution of 40 (150 Å slit width).
• High-resolution observations (50,000, 0.1 Å slit width) were achieved for bright objects (V = 0.0) with 1-second integration times.
• Shot noise was identified as the dominant noise source for count rates below 10^4/sec on photometric nights.

Conclusions:

• The modified spectrophotometer effectively leverages single-photon counting for improved astronomical spectroscopy.
• The instrument achieves high sensitivity and resolution, enabling the study of a wide range of celestial object magnitudes.
• Further optimization may be needed to mitigate shot noise limitations at lower count rates.