Circular Letter to Solar Observatories


   Dear Sirs,

   Annexed are Memorandum and Questionnaire concerning
problems of the single-frequency observations of the Sun
on metric wavelengths (suggested upper limit for the band
is 1000 MHz). Under circumstances explained shortly in
there Dr. P. Zlobec (Osservatorio Astronomico di Trieste,
Italy) and I decided tentatively to undertake an action
purpose of which is to collect the informations regarding
receiving systems used or planned at solar stations as
well as to obtain your opinions based on experiments made
in various circumstances. It is hoped that this undertaking 
will be the first step towards an international
improvement in this field and may be treated as an extension 
of the work done by Prof. H. Tanaka and others, at
the lower frequencies. As Prof. Tanaka says, these problems 
are much more difficult than on higher frequencies.
In spite of that, he was glad of our initiative and we
found very helpful his advices and encouragement during
preparation of these matters.

   We hopefully expect that you will be able to find some
spare time to reconsider problems presented here and 
inform us about your opinions. Other problems not noticed
by us would perheps be most valuable. Especially encouraged 
would be comments and propositions based upon your
own experiences. However, descriptions of your equipement
in compliance with our Questionnaire, even without
further comments, would also be of great Value.

   The Questionnaire itself is regarded as a guide in
your comments but we do not see any necessity to follow
it exactly in the proposed form. In order to avoid 
misunderstanding in meanings or units there are short 
explanations or examples of possible realizations inside 
parentheses.

   The collected material will be the basis of a summary
reviewing existing techniques of the metric wavelengths
observations and your propositions regarding methods of
overcoming particular instrumental difficulties as well
as remarks on standardization of routine observations and
data processing. This summary when completed will be in
the first instance distributed among the contributors.
Later on we intend to publish general results of this
undertaking in one of the astronomioal journals.

   If in your opinions it will appear that some of the
problems are above a single Observatory means or interest
they might be resolved with the aid of such organizations
like URSI or IAU (General Assemblies).

   Please feel free to express all your comments or opinions
that might improve for benefit our common course.

   You are kindly asked to send your response to Dr. Zlobec
(in English or Italian) or to me (in English, Russian or
Polish) until October 1976.

   Thanking in anticipation 

                                    Your sincerely


                                    Kazimierz M. Borkowski

Torun, May 7th, 1976.

   P.S.

   In the late 1974 (Nov.) I asked some of you for comments
on the variability index evaluation. Now I would like to
thank you very much for your helpful responses. Basing on
them and other materials I prepared proposition for a new
measure of variability that is to be published in a few
menths in "Postêpy Astronomii" (No. 2, 1976, in Polish) and
was submitted to "Physica Solariterrestris" (in English;
the paper is entitled The Variability Index for Solar Radio
Emission). It was also presented in an abbreviated form in
the monthly report of January 1976 of Torun 127 MHz 
observations.
                                    K. M. B.