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On Sep 29, 2004, at 6:12 PM, Alexandre Eremenko wrote:

> Dear Fred,
>
>> as I had trouble with a telescope.
>
> What trouble with a telescome?
> I think I am also having troubles with my scopes,
> and even considering buying a Cassens-Plath telescope
> (which fits SNO-T as well, they say).
>
>> I would buy
>> a Tamaya Spica.  I would like to sample some of the Russian sextants
>> too, but....
>
> Why Tamaya? You think it is superior to Cassens-Plath is some respects?
> I would be also interested to sample a Cassens-Plath;
> maybe sometime we will come together...

The trouble was a Cassens and Plath telescope that was not aligned
properly.  I didn't check it when I first received it, which I should
have done; after a month of wasted sights I finally checked it.

The Cassens and Plath is very accurate and precise, but the mirror
housings are aluminum, I believe.  In addition, the shades are glued in
the holders; the star scope is set so far back on the mount that it's
wide field of view exceeds the diameter of the horizon mirror and the
horizon shades need to be cocked back to block the sun.  There also
were some quality issues with the box packing.

My understanding is that the Tamaya Spica is very carefully constructed.

>
>> from electrolytic corrosion, which disfigures many an aluminum
>> sextant.

This occurs on exposure to salt water.

> Your table (which I still have to study carefully)
> shows that you had problems somewhat similar to my ones.
> Which sextant (and scope!) was used, if you remember?
> The columns in the table I received were not aligned well.
> After the date, what is this? GMT?
> And what is "N(Da-Do)"? (Third column from the right).
>
>> Note the widely
>> varying difference between Da-Do for objects between 25 and 33 degrees
>> apart.
>
> Yes!! Same effect I had. I even  suspected something was wrong with the
> refraction theory... for this case. How did you calculate the
> "real" distances?

The columns are Object1, Object2, the arc distance between them in
whole degrees, then the date & GMT are one column, separated by a
space.  Following that, N(Da-Do) is the number of observations in that
set, then the mean and standard deviation of those observations.  Da-Do
is the difference in seconds of arc between the cleared, observed
distance and the calculated distance.  I used Young's method as
outlined by George Huxtable in January of 2003 on this list.  The
archives of this list are at 

The observations were made with a Husun "Mate" sextant with a 2.5x
telescope.

>
>> Object1 Object2 degrees date&GMT    N(Da-Do)     Mean(Da-Do:sec)
>> Std(Da-Do:sec)
>>
>> Betelgeuse Rigel   18      04/02/2003 00:59:18     3       17      20
>> Procyon Betelgeuse 25      01/13/2003 01:25:29     1       5
>> Sirius  Procyon    25      02/14/2003 04:57:12     3       -2      5
>> Sirius  Procyon    25      02/23/2003 22:24:40     4       30      20
>> Sirius  Betelgeu   27      01/12/2003 03:46:39     2       -52     0
>> Betelgeuse Pollux  33      02/23/2003 22:33:08     3       -45     11
>> Capella Betelgeuse 39      01/20/2003 23:21:31     3       2       10
>> Vega    Arcturus   59      07/16/2004 02:40:23     5       -13     59
>> Sirius  Capella    65      02/03/2003 02:09:00     13      -63     71
>> Sirius  Schedar    104     02/03/2003 04:09:56     4       -47     95

   

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