Hi guys, it's me again:
Just thought of another fun experiment we can do during the Jan. 31 lunar
eclipse. One person wrote saying that he doubted there would be enough
light during a prenumbral eclipse to cast a shadow on a sundial. If you
have a photometer, you could measure the minimum
There will be a total penumbral lunar eclipse on Jan. 31. The moon will
pass entirely through the lighter part of the Earth's shadow without any of
it being in the umbra or darkest portion. I don't know the exact time of
the event. This is a somewhat rare event. I thought that this would be an
Hello All:
I've been enjoying the discussion on the delay of sunset due to refraction.
Somewhere I heard that at mid latitudes this is about three minutes. Can
anyone confirm this?
Here is the reason I ask. On the outer edge of my horiz. sundials I engrave
little sunrises and sunsets which
Dear Patrick:
Thank you so much for a good answer that makes sense.
The effect of refraction of light in the earth's atmosphere is least when
the sun is highest but in practice is not a major factor when the sun's
altitude is more than 10 degs above the horizon. For this reason you should
use
Dear Philip,
You have posed some interesting questions about setting up a
dial. You should bear in mind a few points before deciding.
1. If there is any error in the gnomon angle, this will
show worse at 6am and 6pm and will be totally invisible at 12.
2. If
Dear Slawek and others:
We could make this question even more complimented if we consider the speed
of light. When we see the sun's center on the horizon we are seeing light
that left the sun about 8 minutes earlier. The sun really has already set.
(of course this has no practical effect on
Hello dialists:
Hoping that I might get your help with one last question that needs
answering before the new edition of my Sundial Owner's Manual goes to print.
In the chapter on setting a (horizontal) sundial, I recomend that a dial
should be oriented north not by a compass and not by polaris
Hello Dialists:
I am currently writing the 4th edition of my Sundial Owner's Manual and want
to make sure that the information I,m giving my customers is correct.
I have a section which tells how to tell time by using moonlight and a
sundial. I provide a table of corrections from which the
Nass members and Dr. Langley:
The sundial I saw out my window while landing in Dallas was DEFINITELY a
large horizontal dial with hour markers and a bright red gnomon pointing
north at about the right angle. It was not navigation equipment! It was
cloudy that day so I couldn't tell the time.
Dear NASS Members:
I returned home after Christmas to find 52 e-mails most of which were
responses to my inquiry about Daylight Saving Time. Thank you all for
writing such insightful answers, including you, Fernando. I was astounded
by the variety of opinions out there and the depth of
Responding to questions about wooden sundials:
In 1993 I built my first dials out of teak, mahogony and oak, trying various
protective enamels, varnishes, and oils. They have been baking in our hot
Arizona sun , experiencing huge day/night temperature differences, and the
teak and mahogony
Dear NASS members:
I want to thank all of you who immediately sent me E-mails in response to my
letter of introduction yesterday. It is so nice to be connected to this
group via the net! But I can't wait to meet you all in person.
Most of you had the same questions: Do I have a
Dear Bob:
John Carmichael recently subscribed to this group using this address.
Unfortunately, the day after he left on a week long trip. He is a sundial
maker who works in Coconino Flagstone. (That's in Arizona) The colors vary
from a pinkish to an amber to almost a white. He has found that
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