Project Leader: Mark Blackford

The SBDSLR Project aims to provide observational data in support of Ed Budding’s The Southern Binaries Programme of CONZ and CAAM. The targets will be bright, relatively under-observed, or newly discovered, southern binaries. They will mostly be eclipsing binaries, but others may be close binaries with possible photometric effects of binarity but not eclipses.

A secondary aim of the SBDSLR Project is to establish DSLR photometry as a legitimate technique for scientific studies of variable stars. Due to their brightness our targets will generally be unsuited to the narrow field of view of CCD imaging through a telescope. DSLR cameras with standard lenses provide fields of view wide enough to include suitable comparison stars.

Specific measurements may vary from target to target and will be described in detail as targets are added to the Project. Initially we will concentrate on determining orbital period and well-determined times of minimum of primary (and secondary) eclipses of eclipsing targets. For many of our targets the available epoch and period data are quite old and cannot be relied upon for predictions of eclipses.

Complete light curves may be required for some targets. Combined with radial velocity and spectral data, these light curves will allow determination of many parameters of the orbits and stars themselves.

All significant results are to be published in suitable journals, with observers’ data and summary reports on progress published on this website.

This project is suitable for observers new to DSLR photometry as well as for experienced observers. Feedback and advice on observing and results will be provided. This is a good opportunity to learn and improve technique, as well as making publishable scientific contributions.

Participants in the SBDSLR Project will need to develop skills in recording and measuring images as well as transforming their measurements to the standard magnitude system. Whilst time of minimum can be determined from untransformed magnitudes, the magnitudes cannot be compared and combined with other observers data. A tutorial on DSLR photometry is available, including determining and applying transformation coefficients.

Lists of targets will be published here from time to time, together with observational requirements. VSS participants will be notified by email of new targets and issues arising about current targets.

Observational requirements may differ somewhat from target to target, but in general they are:

1. DSLR observation with standard camera lens (not through telescope).
2. Use the epoch and period data given for each target to predict eclipses using Tom Richards’ Times of minimum spreadsheet Excel spreadsheet. These predictions may be out by many minutes or even hours due to the length of time since the epoch and period were determined. Therefore, it may take several attempts to record an eclipse.
3. Time series are needed, preferably through an entire night or as much of it as possible. Therefore, the camera must track the target, e.g. piggy backed on a motorised telescope.
4. Record time series images with as fast a cadence as you can whilst keeping SNR > 100.
5. Photometric filters are not required, we will use the three colour channels of the camera.
6. Exposure time and defocus should be optimised to achieve Green channel peak ADU values of ~3/4 of your camera’s saturation value for the brightest comparison star (or target). This will ensure all three colour channels will be below saturation for the target and comparison stars.
7. Observers will be advised what data to submit and in what format.

Project Targets

Here is a list of stars under observation, observing season, and current status. Click on the star name for more information about it, particularly observing requirements, data for predicting times of minimum, VSS observational data and reports, and news items. For information about eclipsing binaries and their observation in general, see the article Eclipsing Binaries and VSS, with many useful links. For information and links on observing techniques, see Observing and Reporting. More information on the individual systems can be accessed via the AAVSO VSX Index.

Observing season dates are calculated for observers at Sydney’s latitude. Elsewhere these will differ somewhat.