BL Tel Project

Project Leader: Peter Williams @peter-williams

Visual observers are invited to participate in monitoring of BL Tel for which observations are required. BL Tel was the subject of a long-term visual study between 1983 and 2000 with the recording of 8 eclipses during that time. Results of those eclipses are summarised in Publications 25 (C99) of the VSS RASNZ (2000). BL Tel is an Algol type system of period near 778 days and visual range between magnitudes 7 and 10. Eclipses are of duration up to 2 months.

Project Description

Introduction

BL Tel was the subject of a long-term visual study between 1983 and 2000 with the recording of 8 eclipses during that time. Results of those eclipses are summarised in Publications 25 (C99) of the VSS RASNZ (2000). BL Tel is an Algol type system of period near 778 days and visual range between magnitudes 7 and 10. Eclipses are of duration upto 2 months.

Objective

The objective is to produce a complete visual light curve based on daily mean magnitudes and from this to determine the basic parameters of the eclipse – the date of mid eclipse, daily rate of brightness change, overall duration and amplitude. These results can then be compared with results from the earlier eclipses.

2011 Eclipse

Visual observers are invited to participate in monitoring the 2011 eclipse of BL Tel for which observations are required between mid April through to the end of June 2011.

Observations

Visual observers should obtain magnitude estimates on a daily basis commence immediately and continue through to the end of of the eclipse period. BL Tel is suitable for observation with binoculars when at maximum and during the early and late stages of eclipse. Large binoculars or small telescopes will follow through it through minimum.

A chart showing suitable comparison stars is shown here: .

All observations should be included in usual reporting to the AAVSO. Observers should also send a complete list of their observations in JD format (no heliocentric corrections required) to the undersigned at completion of the program.

Multi colour photometry is also most welcome. Arne Henden, Director of the AAVSO, is also investigating use of the BSM-South telescope during this time.

2013 Eclipse

The bright Algol type eclipsing binary is again due to undergo a primary eclipse, the predicted date of mid eclipse being near 2013 July 06.

Visual and other observers are again encouraged to monitor this event as part of a long term study to monitor eclipses of BL Tel. Eclipses occur at intervals near 2 years and 2 months and the 2013 eclipse will be the 10th to be observed since this program commenced 20 years ago with the 1983 eclipse.

Interested observers should commence observing BL Tel from now and continue through to mid August to ensure both onset of eclipse and the subsequent return to maximum light is recorded.  The current chart for visual observers is available on the VSS web site under the tabs Research > Visual Observing > BL Tel 2011 then via the link under the heading Observations. Alternatively, a copy can be provided by email upon request.

Observations should be made on a nightly basis and reported as usual to the AAVSO.  Please also send a copy to the undersigned at completion of the eclipse.

With a visual magnitude range of 7 to 9, BL Tel can be followed with binoculars at maximum and during early/late stages of eclipse and with larger binoculars or small telescope through minimum.

Results for the 2011 eclipse appear in the VSS Newsletter – August 2011.

Peter Williams @peter-williams
Heathcote NSW

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