TLK 90 Variable stars

The TLK 90 list is a specialized catalog designed for the dedicated visual observer. It highlights 90 stars that exhibit significant, predictable changes in brightness, making them perfect targets for those using binoculars or modest telescopes.

History & Who Made It

The list was compiled by Thomas L. Kaye (TLK) and published in 1990. Kaye was a highly active member of the amateur astronomy community and a frequent contributor to the AAVSO (American Association of Variable Star Observers).

In the late 1980s, Kaye noticed that while professional catalogs like the General Catalogue of Variable Stars (GCVS) contained thousands of entries, beginners often struggled to find stars that were bright enough to observe effectively by eye. He hand-selected 90 "showpiece" variables to act as a definitive starting point for anyone wanting to contribute to the science of variable star monitoring.

The Purpose

The TLK 90 served as a bridge between casual stargazing and scientific data collection.

• 1. Skill Building: It provides a curated "gym" for observers to practice estimating stellar magnitudes by comparing the variable star to nearby "fixed" stars.

  2. Consistency: By encouraging many observers to watch the same 90 stars, the catalog helped create very smooth and accurate "light curves" (graphs of brightness over time).

  3. Color Observation: Many stars on this list are deep red giants, which helps observers learn how the human eye perceives different light frequencies as a star’s temperature changes.

What Objects and How Many

The catalog contains exactly 93 stars. The vast majority are "pulsating" variables—stars that physically expand and contract, changing their surface area and temperature.

• Mira Variables (Approx. 60%): Massive red giants that pulsate over months.

• Semiregular Variables (Approx. 30%): Stars with less predictable cycles that still show visible changes.

• Eclipsing Binaries (Approx. 10%): Two stars orbiting each other, where one passes in front of the other to create a "dip" in light.

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