Winter is close – observing in coldest weather so far during this season

Last night sky got clear here in Sodankylä, and I set my scope up for routine observations. Winter is already very close, and suddenly weather turned very cold in monday night. It had been about +1 – +2 °C for long time, but during monday, temperature was below freezing all day and night and freezing, cold northern wind was blowing. Temperature was about -5 °C, but the freezig factor of the wind made it to feel like -10 °C!

In the evening, I made observations of R Tri and Z Uma, two variable stars that I always find myself obsering! For some reason, these stars have turned into my favourite variables! This time brightness of R Tri had dropped to 5.9, which means decrease of 0.4 magnitudes in 6 days! (I made my last observation in 8.11.2011). First I was quite skeptical and suspicious, but I just had to believe my eyes. And then I plotted my observation on the light curve of recent observations of this star sent to AAVSO, I noticed that my observation is sitting beautifully on the curve! So my observation was correct, and the brightness of this star had suddenly dropped ~0.4 magnitudes. I also noticed that at least according to the light curve, R Tri has a sharp maximum, and it has peaked in late october. Now it is clearly getting fainter again.

Then I observed also Z Uma, which is getting brighter. I estimated it’s brightness to be 7.4, which is still about 0.2 magnitudes less than the average of recent observations in the AAVSO database! So it means, that I’m still underestimating the brightness of this star – a thing that I discussed also in my last post.

And before going in and enjoying some hot blackcurrant juice, I watched quickly Jupiter and the Moon! On the “surface” of Jupiter, I was able to spot a shadow of one of the Jovian moons!

Observing session: #21/11-12
Date: 14/15.11.2011
Time: 22.00-23.05
Place: Sodankylä, Finland
Instruments used: L102/1000mm
Objects observed: R Tri, Z Uma
Conditions: NELM: 5.6, SQM: 19.23, -5 °C, clear sky, cold northern wind, no aurorae, 86% Moon in east at altitude of 30°


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