86164.0905??(23 h 56 min 4.0905?s or 23.9344696 h).?
Another way to understand this difference is to notice that, relative to the stars, as viewed from Earth, the position of the Sun at the same time each day appears to move around Earth once per year. A year has about 365.24 solar days but 366.24 sidereal days. Therefore, there is one fewer??per year than there are sidereal days, similar to an observation of the?.?This makes a sidereal day approximately?365.24/366.24??times the length of the 24-hour solar day.
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https://adsabs.harvard.edu/full/1984IAPPP..17...55D
Pages 55 ~ 61
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I received an email asking "What is sidereal time and where is it used?"
And
"How do you derive it from 60Hz?"
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Wiki has a fairly good article on sidereal time.
Sidereal time is used by astronomers. There are special motorized drives that change the azimuth (degrees north-south) and elevation (height) to keep a star centered in a telescope
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Any sane person uses a app for their Android or iPhone. But there are special people like My Crazy Cousin who lives north of Santa Fe who is an advanced amateur astronomer.
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Anyway My Crazy Cousin wanted a dual display clock, one display would show Mountain Standard Time, the other Sidereal time, both synched to WWV.
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I happen to have some unused National Semiconductor LSI MM5314 single IC clock chips.
I used green 7 segment LEDs for the MST and red 7 segment LEDs for the Sidereal.
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I used an inexpensive precision 10MHz canned TTL oscillator with internal heater. She upgraded to a ~$150 GPS disciplined oscillator with a 10MHz output.
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I used a PIC programmed with magic code to convert 10MHz to 60MHz.
http://leapsecond.com/pic/
http://leapsecond.com/pic/picdiv-list.htm
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scroll down to
pd60.asm:;?? PD60 -- PIC "4-pin" frequency divider (10 MHz to 60 Hz)
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You feed 10MHz into the PIC and get 60Hz out, the accuracy of the 60Hz depends on the accuracy of the input 10MHz.
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Then open
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https://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1984IAPPP..17...55D&defaultprint=YES&filetype=.pdf
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And you see one way way to modify 60Hz to feed "sidereal 60Hz" to a LSI clock chip to display sidereal time.
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I used the same logic but with CMOS chips.
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Now if the Leapsecond.com only had a 10MHz to "60Hz Sidereal".....
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Now as I said at the beginning, any sane person would use an android device, perhaps an older tablet for a nice large display....but My Crazy Cousins "observatory" is in a marginal cellphone coverage so she maybe she isn't so crazy.
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[She also happens to be my favorite cousin. A really nice if somewhat dingbatty person.]
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My personal GTM/EST/Sidereal clock uses 3 MN5314, on for each time zone and uses the chip enable pin to turn on the desired time zone. Of course mine was built from 1976 through 1980 in stages.
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I came up with a logic circuit using 74LS chips that achieved the same function. I replaced my 74LS design with the new CMOS.
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Unless you are an astronomer, or total geek, you will never need sidereal time, but this is one 'easy' way to obtain it.
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Of course she could simply have spent ~$200 at
https://brgprecision.com/products/stand_alone_clocks/sidereal.php
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Note 1: I've never actually used the Sidereal function, the only really clear nights in Kentucky suitable for astronomy are when there are no clouds and it's -10...and I'll be inside where it is warm and either asleep in our bed or listening to shortwave.
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Note 2: The CMOS 7555 are a Xitch to get working properly!
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Note 3: I saw a scheme in a British or German electronic hobbyist magazine that used logic to switch the 50/60Hz input from 60 to 50 every so many cycles to obtain sidereal time. It's been over 50 years I don't recall the circuit.
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Note 4: For a really hard way to get regular and sidereal time
https://www.worldradiohistory.com/UK/Practical-Electronics/80s/Practical-Electronics-1981-10.pdf
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Note: 5: It should be possible to use the leapsecond.com 10MHz to sidereal 1 pps to drive one of those cheap analog clocks.
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They have a 32?kHz crystal, "IC" to produce 1 PPS, it'd require some experimentation but it should work.
Since My Crazy Cousin is dyslexic, like me, analog clocks are viewed as the work of the devil and you are on your own here.
This might help
https://sound-au.com/clocks/timebase.html
and
http://leapsecond.com/pic/picdiv-list.htm
scroll down to
pd29.asm:;?? PD29 -- PIC 10 MHz to best sidereal 1PPS, with sync and milli-step
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Note 5: You can also replace the large coil on regular AC mains powered analog clock with a smaller winding and lower voltage.
https://sound-au.com/clocks/motors.html
https://sound-au.com/clocks/ocm.html
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Mr. Elliot also has a nice circuit for changing 50>60Hz or 60>50Hz to allow clocks from "over there" to work "here."
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My sister has a hideous French clock she loves, it runs on 50Hz and the ESP circuit and replacing the high voltage coil with a low voltage one made her a happy camper.?
I could have divided 60Hz down to 20Hz, used a PLL with divide by 5 to generate 100Hz, divide by 2, but that was too simple. I wanted to play with the ESP circuit.
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I'm ignoring Raspberry and Ardino because I have zero familiarity with programming or interfacing them (and no desire to learn, I ignored Apple and Wang at work and they went away....). Although I am running a Raspberry with a dirt cheap SDR from SDRplay and it is nice. A friend's daughter say the Raspberry up for me.
[ The windows version requires windows 10, ain't gonna happen, I'll learn Linux first.]
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I have enough real electronic projects to keep me busy as long as I'm on this side of the grass.
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Yea I have too much time on my hand this winter.
The only good thing about winter is it does end. [I hope]
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