[vsnet-chat 4738] Re: Eta Carinae

[Fraser Farrell <fraser@trilobytes.com.au>]

On Fri, 17 Aug 2001, Bish Ishibashi wrote:
>Our next visit to Eta Car with the HST/STIS happens in between September
>through November 2001 also. So stay tuned. [And while waiting, please 
>give your best shot to observe it as much as you can!]  

A tad difficult at the moment, because it's spending most of the night
near ground level. Not to mention the 100+ km/h winds we've had here
for the last few days. My last attempt to do astronomy was thwarted by
flying debris from my neighbour's roof.


>He was presenting the visual light curve of
>Eta Carinae measured by Albert Jones. What fascinated me was to learn 
>that the light curve exhibited a yearly variation with an amplitude of
>roughly 0.3 astronomical magnitudes. Basically the annual change in 
>atmospheric extinction (color-effect that occurs at high air-masses) gave 
>rise to the yearly variation.

An interesting point. Albert has for many years observed from Dunedin,
which from memory is at about latitude 45 degrees south. If extinction
is the cause then the yearly variation should be more pronounced for
observers further north. For example Stan Walker's group observe from
Auckland (~35 S). And the majority of Australian observers live
between 31 and 38 south. Observers further north not only have the
ground getting in the way; there's also Wet Season to contend with.


>Well, as naive as I was then, I told Chris 
>that I was amazed to know that human eyes could measure the visual 
>magnitude of a star so ACCURATELY. Chris immediately corrected that 
>"these measurements are NOT ACCURATE; but they are taken CONSISTENTLY." 

But all of my observations are Perfect it's just the rest of you who
are wrong ;-)


cheers,
Fraser Farrell

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