[vsnet-chat 230] (fwd) Re: visibility of omicron Cet

[Taichi Kato <tkato>]

From astroman@voyager.co.nz Fri Apr 18 15:05 JST 1997
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Date: Fri, 18 Apr 1997 18:03:50 +1200 (NZST)
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To: Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>
From: Stan Walker <astroman@voyager.co.nz>
Subject: Re: [vsnet-chat 228] visibility of omicron Cet
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At 11:40 AM 4/18/97 +0900, you wrote:
    Thanks to Stan Walker's reply to my question about the seasonal
visibility of Mira (omicron Cet).  I have picked up from the VSOLJ record
the first and last observations of the recent 20 observing seasons.

Taichi Kato

Dear Chatters,

After Taichi Kato's effort I had best supply some dates on Mira observations
in the south. I selected the following six cycles for reasons explained below:

Last Obsn                       First Obsn                      Interval

35191.8 @ 5.1           35240.3 @ 6.8                   48.5 days
35542.9      4.6           35603.3      7.3                   60.4
35901.8      6.8           35970.3      8.0                   68.5
36276.9      7.0           36340.3      8.3                   64.4
36648.8      8.8           36699.3      8.9                   51.5
37019.8      8.6           37078.3      6.5                   58.5

I'm unsure of the actual month/days of these JDs but if we take the latest
annual visibility before disappearance (set 6) and the earliest reappearance
(set 2 and 5) the gap is 45 days. Allowing for weather and brightness
effects (with maximum in the centre of the gap) this can probably be reduced
to 40 days or slightly less.

However, you might be impressed by the following sequence of measures:

32980.9,8.5     32995.8,9.1     33000,9    33005,9.1       33011,9.1
33017,9.2        33023,9.3        33033,9     33059.3,8.7   33070.3,8.7
33072.2,8.7    33075,8.6         33075.3,8.7    33078,8.9

I don't know who the observer was but he obviously used a telescope in the
twilight! The "gap" seems to be from 33033.9 to 33059.3, a mere 25.4 days
from 1949 April 26 to May 22! Maybe Albert Jones could comment on this one?

>From 1930 to about 1960 several NZ observers were following this star with
reasonably steady cover in the 1950s. But since about 1960 the Section
concentrated on stars south of the -30 referred to. Consequently the later
data are very sparse. I observed the star along with other members of the
Auckland Astronomical Society about 1968-72 and we concluded the visibility
gap was about 6 weeks which agrees reasonably well with the above - but the
observations have been lost. All based on binoculars, of course - not a half
metre telescope!

I note that historically (at least since 1596) the latest observed "maximum"
was 19 March in 1894 by Markwick and the earliest after the gap was 25 May
1873 by Schmidt. Fabricius had one on 25 June. I'm unsure whether these were
observed or extrapolated. Or even which hemisphere the observers worked in!

Thanks for the other data from the VSOLJ - I'll reply separately about this.
It's a very fascinating star.

Regards,
Stan Walker

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