From: TerryMosel@aol.com Date: Fri, 6 Jun 2003 14:47:20 EDT Subject: Rho Cas, Delta Sco, SaN, Solar day, BBQ Hi all, The unusual & unstable hypergiant Rho Cas may be about to show some variability. Normally around mag 4.6, it can brighten to about 4.1, before usually fading to below 6th mag, as it ejects vast amounts of material from its surface. Useful comparison stars are Zeta, mag 3.7; Kappa, mag 4.2; Lambda, mag 4.8; Tau, mag 4.9; Sigma, mag 5.0; 4 Cas, mag 5.0; 12 Cas, mag 5.4; SAO 35761, mag 5.6; SAO 35682, mag 6.2. Delta Scorpii has also been brightening steadily over the last year or so. Normally around mag 2.3, it is now considerably brighter than mag 2, and is becoming almost comparable to Antares, which is about mag 1. There are no suitable comparison stars in the area, but try to judge it relative to Beta (2m.6), Pi (2m.8), Sigma (2m.9) or Antares itself (range 0.9 - 1.1). Delta is a blue supergiant, about 1500 times brighter than the Sun; Antares is of course a red supergiant, so the contrasting colours make it hard to compare directly. I forgot to mention that the Sky at Night programme, repeated tomorrow (Sat) morning on BBC2 at 11.30 features photos of the Transit of Mercury by IAA member Peter Paice. (Also, another IAA member, Les Gornall, got an excellent series of photos of the annular eclipse from the Hebrides, and has combined the best into a short video sequence which he will show at our opening meeting on Sept 24.) Advance notice: IAA Solar Day, WWT, Castle Espie, Comber, Co Down, Sun 15 June, 14.00 - 17.00. All welcome. IAA Summer Solstice BBQ, Armagh Observatory, Sat 21 June, 15.30 (tbc) - lateish. More details later. For IAA members & guests, plus of course Observatory & Planetarium staff & guests! But we won't turn anyone else away, if you ask nicely inb advance! Bring your own food & drinks, we provide the cooking etc. More details soon. Good luck & clear skies, Terry Moseley
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