Optec SSP-3 Photometer

Photometry of bright stars on the 16-inch telescope is done primarily with an Optec SSP-3 solid-state photometer. We can also mount this instrument on the 20-inch. We have B, V, R, and I filters. But the system is not as reliable in R and has much less sensitivity in I. So we primarily observe in B and V with it.

We observe Be stars and other bright targets. These observations help tie together the digital and visual photometric reference frames.We submit all our measurements to the AAVSO photometric database for archiving.

A copy of the manual is attached to this page as a document or it can be found at OPTEC's website.

Workflow/Use

The SSP-3 is an exceptionally stable instrument that uses a single pixel photodiode. Observations of a target are paired with a known comparison and a check. The telescope slews between the targets and the operator reads the measurements off the led display on the SSP-3. Later the measurements are reduced in a spreadsheet.

Calibration

Ideally, at least once every six months we perform observations to calculate the Epsilon-V (Hall, 1983) for the SSP-3/16-inch system. The system has remained stable as long as we have done it (since 2013). Our Epsilon-V value is consistent with zero (-0.011 +/- 0.013 based on nine measurements over five years), therefore no correction is called for to our reported values.

We began in late 2016 measuring our Epsilon-B value. It is 0.135 +/- 0.018 based on two measurements. It is likely that the B magnitudes we have reported without application of this correction are (depending on the color of the object) systematically a few hundredths of a magnitude bright.

There is a larger still Epsilon-R value that we have not yet attempted to measure.