sidereal clock for sale
Bryan Mumford
It was created at the request of staff at Mt. Wilson and may be of
interest to amateurs who want to keep an eye on local sidereal time. Local
sidereal time is the Right Ascension of objects currently at the zenith.
See:
http://www.bmumford.com/clocks/sidereal/index.html
--
Bryan Mumford
www.bmumford.com
Skip Freeman
> Mumford Micro Systems is making an analog quartz sidereal clock for sale.
Hey, astronomy buffs! My green laser arrived today. Should I buy a
sidereal clock next?
-Skip
Daniel
> > Bryan Mumford wrote ...
> > Mumford Micro Systems is making an analog quartz sidereal clock for sale.
>
> Hey, astronomy buffs! My green laser arrived today. Should I buy a
> sidereal clock next?
Only if you're willing to pay 4X the going rate for a battery powered
quartz 24-hour clock!
Daniel
Robert Provin
news:b07467f0.02050...@posting.google.com
======================================================
Hi Daniel,
A sidereal clock may have 24 hours on its face, but it definitely does
not mark time at the same rate as a standard "quartz 24-hour
clock"! In other words, there is a difference between a mean solar day
and a sidereal day.
Robert
--
Posted via Mailgate.ORG Server - http://www.Mailgate.ORG
Bryan Mumford
Dani...@unitedstates.com (Daniel) wrote:
> Only if you're willing to pay 4X the going rate for a battery powered
> quartz 24-hour clock!
Yeah, it sounds expensive, doesn't it! After all, it *IS* just a 24 hour
quartz clock. The problem is that the period of the quartz oscillator
needs to be .997270 seconds, not 1.000000 seconds. That's a big "gotcha".
If someone were making a million of these they could be cheap because a
mass-manufactured quartz motor is cheap in production. But there is no
mass-manufactured quartz clock with a sidereal rate. What I had to do was
write a program for an ultra low power microprocessor chip that would
interface with a "surgically" altered quartz clock motor and drive it
reliably at the right rate. I hand tune each oscillator to within 2 parts
per million and use a precision voltage regulator to eliminate effects of
battery voltage on the rate. I fabricate a custom dial and assemble the
whole kit and kaboodle one at a time, by hand.
That's what it takes for me to make a sidereal rate quartz clock. I'm not
going to get rich on these, it's an esoteric project that Seiko won't
tackle because the market is smaller than hairs on a flea. If I had half a
brain I wouldn't tackle these projects either, because it takes far longer
to work it all out than I'll ever recover in sales. It's just that it was
"up my alley", and I couldn't resist when the people at Mt. Wilson asked
if I could do it for them. The "cool factor" is very high; to have my
clocks used by astronomers at Mt. Wilson!
Florian
>quartz 24-hour clock!
Find me a sidereal clock for a quarter the cost of Mumfords and i'll buy it!
-Florian
http://www.stargazing.com/
Mike Simmons
Only if you believe the sidereal day and the mean solar day are the same length.
I can vouch for Bryan's clocks, not because I have one but because I know the
people that have the prototypes that he made. I asked the observer at Mt. Wilson
that started the whole thing what he thinks of the clocks he has and I got a 15
minute rant about how great the clocks are. He'd been looking for an analog
sidereal clock for years before someone pointed him to Bryan as the guy that
could make one. He is "tickled pink" with what he eventually got. One clock is
in his home on the mountain and a couple other observers have them as well. He
says it's something everyone with a telescope should have and he's planning on
giving some as Christmas presents this year (I have to do something to get in
really good with him!<g>). The clocks aren't in the domes now but if/when the
old sidereal clock in the 100" dome finally gives up a Mumford clock will replace
it. He also says Bryan is a great guy who really knows his stuff and goes out of
is way to get everything just right.
I suggest you go to Bryan's site and see what he's offering. There isn't
anything like it available anywhere -- at any price. I'm putting it on my own
Christmas list.
Mike Simmons
Daniel
>
> Yeah, it sounds expensive, doesn't it! After all, it *IS* just a 24 hour
> quartz clock. The problem is that the period of the quartz oscillator
> needs to be .997270 seconds, not 1.000000 seconds. That's a big "gotcha".
> If someone were making a million of these they could be cheap because a
> mass-manufactured quartz motor is cheap in production. But there is no
> mass-manufactured quartz clock with a sidereal rate. What I had to do was
> write a program for an ultra low power microprocessor chip that would
> interface with a "surgically" altered quartz clock motor and drive it
> reliably at the right rate. I hand tune each oscillator to within 2 parts
> per million and use a precision voltage regulator to eliminate effects of
> battery voltage on the rate. I fabricate a custom dial and assemble the
> whole kit and kaboodle one at a time, by hand.
>
> That's what it takes for me to make a sidereal rate quartz clock. I'm not
> going to get rich on these, it's an esoteric project that Seiko won't
> tackle because the market is smaller than hairs on a flea. If I had half a
> brain I wouldn't tackle these projects either, because it takes far longer
> to work it all out than I'll ever recover in sales. It's just that it was
> "up my alley", and I couldn't resist when the people at Mt. Wilson asked
> if I could do it for them. The "cool factor" is very high; to have my
> clocks used by astronomers at Mt. Wilson!
Hi Bryan,
My apologies. I certainly sounded like I was throwing stones at you
and/or your sidereal clock. That certainly wasn't my intent. I
admire the uniqueness of the product and have no doubt whatsoever that
it is worth every penny of the price -- to the right buyer.
The problem is that I'm a cheap bastard. That's my shortcoming, not
yours and not your clock's.
Now I know that there is a difference between a sidereal vs. a solar
day, and though I never bothered to compute it to any refined degree,
I knew it to be on the order of 4 minutes a day.
So, given my penchant for pinching pennies, I figure that *for my
needs* I can set a cheap mass-produced clock for the correct sidereal
time at the beginning of an evening's observing & by dawn be about 2
minutes off. Further, most mass-produced battery/quartz clocks have a
speed adjustment that through trial & error ought to knock off some,
if not all, of that error. Then again, *my needs* are usually
satisfied if I know the current RA at the meridian within 30 minutes
so mental math generally suffices! This is definitely not the case
for folks at Mt. Wilson and won't be the case for (hopefully a great
many) folks with setups somewhere between mine and theirs.
Once again, my apologies. I sincerely hope that you sell a million
of them and that you make a few bucks in the process.
Daniel
posted at around roughly about near 21:30 LST
Florian
>needs* I can set a cheap mass-produced clock for the correct sidereal
>time at the beginning of an evening's observing & by dawn be about 2
>minutes off.
That's a clever idea! I'd never thought of that. ;-)
-Florian
http://www.stargazing.com/
Dave Jessie
news:CCbA8.1294$vT1.1...@bgtnsc04-news.ops.worldnet.att.net...
>> So, given my penchant for pinching pennies, I figure that *for my
>>needs* I can set a cheap mass-produced clock for the correct sidereal
>>time at the beginning of an evening's observing & by dawn be about 2
>>minutes off.
>
>That's a clever idea! I'd never thought of that. ;-)
It's a fine idea - for a while - until one day you forget to set the clock
back 'about 4 minutes' and then another day passes...and another. Then you
try to remember just how many days have gone by since you last set the clock
back. Before you know it, you're hopelessly lost. I speak from experience!
In 1960 when I was 11 I read the Edmund Scientific book on Sidereal Time and
decided then and there to perform this 'simple' operation with a Big Ben
windup alarm clock I received in a trade from a friend. I was determined to
keep that clock on Sidereal time, and actually did for the rest of that
summer. To set it initially required quite a bit of pencil work! This was
LONG before calculators, so I was very interested in keeping Ben set
properly. You know, I wonder what ever happened to that clock...
Dave Jessie
@mbnet.fi John & Tarja Shakespeare
Mike Simmons wrote:
[snip: Discussion of Bryan Mumford's sidereal clock]
> I suggest you go to Bryan's site and see what he's offering. There isn't
> anything like it available anywhere -- at any price. I'm putting it on my own
> Christmas list.
Beacon Hill Telescopes in the UK sells a clock which displays both sidereal time and
UT (or other zone). It's near the bottom of their online price list, but is not
exactly cheap, at £99.00
http://www.beaconhilltelescopes.mcmail.com
AWR Technologies, also in the UK, has a range of Sidereal/Universal clocks, which
incorporate a switchable metronome (audible second and minute UT pips, useful for
timing). They have different thermal sensitivities and accessories, with prices
starting at £106.00 for the basic model.
http://dspace.dial.pipex.com/awr.tech
There are probably other sidereal clock makers as well, but prices will be higher
than for mass-market clocks.
Best Regards,
John.
--
Remove the DÖTS from shäkëspëärë to get a valid email address.
Bryan Mumford
was a conventional analog clock face to hang on a wall, patterned after an
old one that is in use at Mt. Wilson. I've not found another analog
sidereal clock offered for sale.
I like being able to look over and see the local sidereal time as a
curiosity. It allows me to daydream about the sky and what's going on
outside my little world in front of the computer screen. But I'm curious
about how others might use it. I know LST is critical to real
observervatories, but is it also used by amateur observers?
-Bryan Mumford
Robert Provin
news:news-03050...@192.168.1.101
================================================================
Hi Bryan,
One use that I have done in the past (before the advent of digital
setting circles) was
for locating celestial objects during daylight hours. A polar aligned
equatorial with
old fashioned analog setting circles can be calibrated by simply
pointing the scope
to the meridian (using a level) then setting the R.A. circle by the
sidereal clock. I
enjoyed many hours of daylight observation of planets and bright stars
using this
method.
Mike Simmons
than Bryan's.
Mike Simmons
Bob May
were the old mechanical watches.
I might note that it's possible to take any of the mechanical watches and
retime them for this purpose but the watch repairman will find you wierd!
The problem with the mechanical watches is that you will be needing to check
them weekly as they do run at different rates over temp and position. If I
were to do such a thing with a pocket watch, I'd get a Waltham model 4992
watch (24 hour dial and of the highest quality of watchmaking) for the
watch. Unfortunately, such watches are fairly expensive compared to the
quartz watches.
FWIW, any quartz watch can quickly be made to run at sidereal rate by
changing it's crystal for one that runs that much faster. It would be wise
to use one of better quality that has a setting cap in it otherwise the
timekeeping won't be that accurate.
I might note that the clock that Brian is selling is actually a decent price
as the timekeeping needs to be done on each clock and that's going to be
taking a fair bit of time of the tech to do the job correctly as the loading
of the crystal by test equipment will take the frequency of the clock off.
That's in addition to the need to fully disassemble the clock and put the
new dial on there. In addition, the mechanism isn't one of the cheap wall
clocks as it also has the second timing buttons. Brian looks to have done
an excellent job of making a good accurate clock for keeping time at an odd
rate.
--
Bob May
Imagine the terrorist's fun when they realize that their 72 "nubile virgins"
are all lesbians and cranky from it being that time of the month!
JOHN PAZMINO
F > Subject: Re: sidereal clock for sale
F > Date: Thu, 02 May 2002 13:58:58 GMT
F > Organization: AT&T Worldnet
F >
F > > So, given my penchant for pinching pennies, I figure that *for my
F > >needs* I can set a cheap mass-produced clock for the correct sidereal
F > >time at the beginning of an evening's observing & by dawn be about 2
F > >minutes off.
F > That's a clever idea! I'd never thought of that. ;-)
And a very old one. The trick was the afjustment. In the good old
days, when sidereal time was far more of a necessity for using setting
circles, a telescopist would deidcate a certain wristwatch or pocket
clock for sidereal time. He nudged the sped adjustment a bit and
checked the clock one day later to see if it was off by that 3m56s.
After about a week the rate was as good as could be (the afjustment
was pretty coarse). This clock he kept with his observing gear and he
set it near sunset to a calculated sidereal time.
---
þ RoseReader 2.52á P005004
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Quadibloc
> Convert An Existing Clock By Replacing the 32768 crystal with a 32858 crystal
easily run out and buy?
John Savard
Quadibloc
https://forum.cosmoquest.org/archive/index.php/t-54749.html
Somebody ordered 500 custom quartz crystals at 32.8577 kHz, which is more
accurately the needed frequency. Maybe he still has some.
John Savard
Chris L Peterson
a smartphone.
Chris.B
>
> I'd just go with one of the zillion available sidereal clock apps for
> a smartphone.
I should start whittling a wooden pendulum now. Just in case.
You can tie on a bag of last week's obsolete iPhonies as a bob. ;-)
Quadibloc
> I'd just go with one of the zillion available sidereal clock apps for
> a smartphone.
the sidereal rate...
John Savard
Martin Brown
Someone did it a long while ago they might still have some left.
The way I did it was make a normal clock using a LCD display and 16F877
and provide a switch to allow solar or sidereal timekeeping with an
ability to tweak the second and digitally correct to 1ppm daily.
I intended to add temperature compensation but it worked well enough at
that point so I gave up.
Converting master pendulum clocks originally intended for clocking in
systems to an observatory sidereal clock is quite doable by shortening
the pendulum within the limits allowed by the adjuster.
Today there are any number of smartphone apps that will do sidereal time
and some predictions of satellite passes and Iridium flares too.
--
Regards,
Martin Brown
Mike Collins
food, water electricity and prescription medicine than sidereal time
clocks/.
Mike Collins
and dirt cheap is Emerald Observatory for iPad:
http://emeraldsequoia.com/eo/
They also do an iphone watch app which includes sidereal time displays.
Gerald Kelleher
The annual singular twilight at the South pole as Polar night settles in as part of the long day/night cycle as distinct from the daily day/night cycle experienced at habitable latitudes.
https://www.usap.gov/videoclipsandmaps/spwebcam.cfm
There is no such thing as the solar day/sidereal day, there are,however, the dual day/night cycles and the distinct surface rotations behind them and now quite visible with contemporary time lapse -
https://www.youtube.com/watch?v=CFrP6QfbC2g&t=100s
The surface rotation as a function of the orbital motion of the Earth runs parallel with the orbital plane.
That grown adults could manage to project a notion that there are two distinct 'days' running off daily rotation is absurd in the extreme for it obliterates the possibility of expressing a round and rotating Earth and an equatorial speed.
Chris L Peterson
<'''newspam'''@nezumi.demon.co.uk> wrote:
>The way I did it was make a normal clock using a LCD display and 16F877
>and provide a switch to allow solar or sidereal timekeeping with an
>ability to tweak the second and digitally correct to 1ppm daily.
and a standard crystal (I don't recall the frequency- probably 10 or
20 MHz). It's easy enough to divide that down to get sidereal seconds
with quite high accuracy.
You only need an unusual crystal frequency if you're trying to convert
an existing clock into a sidereal clock.
If I were building a standalone sidereal clock today, I'd probably use
a small computer like an Arduino or Raspberry Pi and implement it in
software. This approach also makes it easy to keep the time synched
across a wireless network.
lal_truckee
> If an EMP destroys electronics I will be more worried about the lack of
> food, water electricity and prescription medicine than sidereal time
> clocks/.
Dr J R Stockton
egroups.com>, Thu, 13 Apr 2017 16:52:26, gmv...@gmail.com posted:
>
>Convert An Existing Clock By Replacing the 32768 crystal with a 32858 crystal then calibrate it against WWV 1000 HZ tone using a variable
>condenser of the right value. Sidereal time is simply one more day within the same civil year period. so like 32768 * 366.25/365.25 should be
>the new frequency.
accurately by normal time. One side of the crystal will be actively
driven at 32768. Tap it off, buffered, and use it as reference for a
phase-locked loop with a ratio of, say, one of these
365/366 1461/1465 12053/12086 146097/146497
which generates the right frequency for driving a sidereal clock. Use a
similar clock, if you like, and just remove the crystal and drive the
receiving side with your new frequency. If the result is wrong by about
8 minutes per day, use the reciprocal ratio.
https://en.wikipedia.org/wiki/Phase-locked_loop
Use something like a http://www.ti.com/product/CD4046B but possibly
faster.
http://www.ti.com/lit/ds/symlink/sn74lv4046a.pdf
Google for cmos pll ic
RS Components may still do good data/application sheets.
--
(c) John Stockton, Surrey, UK. 拯merlyn.demon.co.uk Turnpike v6.05 MIME.
Merlyn Web Site < > - FAQish topics, acronyms, & links.
Quadibloc
> Tap it off, buffered, and use it as reference for a
> phase-locked loop with a ratio of, say, one of these
> 365/366 1461/1465 12053/12086 146097/146497
> which generates the right frequency for driving a sidereal clock.
But I'll admit that the method used by sidereal clock apps is probably simpler
even for an electronic circuit:
Determine the time of day. Determine the day of the year.
Add the day of the year as a fraction of the year to the time of day as a
fraction of a day - and get the sidereal time that way. As a bonus, one gets the
conventional time and date, so that the clock can be (accurately) *set* even if
you don't know what the current sidereal time _is_.
John Savard
Gerald Kelleher
The fictional idea of a sidereal day apart from a solar day is a property of trying to bypass the central Sun as a reference for daily rotation and appealing to a rotating celestial sphere out to the point of Polaris and its Southern equivalent. Linking daily rotation directly to that rotating celestial sphere in order to justify RA/Dec is silly in the extreme
but who would know it ?.
The appeal of separate rotations and especially the rotation that represents the Earth's singular annual rotation due to orbital motion would draw in those who can distinguish between lunar orbital motion where one side of the moon constantly faces the Earth whereas the Earth does not demonstrate the same orbital behavior as it runs its circuit around the Sun.
If direct imaging of the planet's dual rotations doesn't make a difference then nothing will yet not everyone can be prone to celestial sphere reasoning -
https://www.youtube.com/watch?v=CFrP6QfbC2g
Draw a breath and allow the imaging of the motions tell their story.
Quadibloc
> The fictional idea of a sidereal day apart from a solar day is a property of
> trying to bypass the central Sun as a reference for daily rotation and appealing
> to a rotating celestial sphere out to the point of Polaris and its Southern
> equivalent. Linking daily rotation directly to that rotating celestial sphere in
> order to justify RA/Dec is silly in the extreme
> but who would know it ?.
circle.
So while the Earth revolves on its axis at a nearly regular pace - one that was
more accurate than man-made clocks, before atomic clocks were invented - the
shape of the Earth's orbit means that the sundial is affected by the Equation of
Time.
Therefore, when astronomical observatories observed the heavens for purposes of
timekeeping, they did so by making transit circle observations of the stars.
And so referencing the Earth's rotation to the distant stars, rather than to the
Sun, does not seem at all "silly" to us here, but is instead the most natural
and obvious way to study the Earth's rotation in isolation, by itself, rather
than compounded with the Earth's orbital motion around the Sun.
I know you think differently about this than I, and others, do. But it's not
enough just to _say_ that something is silly. If you expect to convince anyone,
you will need to say _why_ it is silly.
John Savard
Gerald Kelleher
VR technology looks like it would further many of the insights that were stitched together in this forum using graphics that were not originally dedicated to the components of a narrative. All it needs are people of courage,endeavor and stature instead of the dull and compliant that plague threads that are never meant for them.
The development of timekeeping from the original motion of a star from the left to the right of the Sun and its first annual appearance at dawn (right of the Sun) is a benchmark for many,many topics of discussion and development. It doesn't invite the mindless but it does require wider circulation.
Chris.B
> In an era when nuclear weapons are back on the agenda I wouldn't have the time to deal with the us/we of this forum although it is the only place I know to further the insights.The intrusions are more or less meaningless vandalism or graffiti by those who live in a bubble yet imaging is still pouring in even when interpretation doesn't keep pace.
Quadibloc
http://www.quadibloc.com/science/cal0501.htm
I recently made an addition, noting that a quartz crystal with a frequency of
4.95827 MHz would not only oscillate 495,827 times in one-tenth of an SI second,
but would also oscillate 509,458 times in one-tenth of a Martian second derived
by dividing the length of 88775.260726 second Martian day by 86,400. At least it
would be as accurate as the available precision for the length of the Martian
day is; 88775.2607260193575818... seconds per day.
Continued fractions are your friend.
John Savard
Quadibloc
day. Using a correct figure instead, I now only need a 437.23 kHz quartz
crystal.
I haven't updated my web page yet with the correction, but I will soon.
John Savard
Quadibloc
John Savard