Sidereal Clock

[RLWP]

I have bought myself an observatory clock. Indicates sidereal time, has a low glare display with easy to read illuminated time indication:

£3 off Ebay. The recommendation is in the Fullerscope brochure. Buy a cheap alarm clock and move the timing adjuster to Fast

Anyone know of a source of luminous numbers? I'd like to renumber 7 - 12 to 19 - 24

I'm loving retro astronomy. It's somehow putting me more in touch with the sky and the history of the hobby

Richard

[Ruud]

That's nice! It looks like it's from the 1940s or thereabouts. Hope you find your phosphorescent numbers.

[RLWP]

Ooo no. I couldn't afford a 1940's one. This is probably a 70's or 80's clock, plastic case and everything.

In many ways, it's quite horrible. However it will do the job very nicely

Richard

[Scooot]

Did I understand you correctly, it's a normal clock but if you adjust the timing adjuster to fast it keeps sidereal time? Is it accurate, could you do that with any clock?

[RLWP]

Did I understand you correctly, it's a normal clock but if you adjust the timing adjuster to fast it keeps sidereal time? Is it accurate, could you do that with any clock?

Well....

You can't do that to a quartz clock - there's no way of adjusting it. You could do it to a pendulum clock, it's not very convenient though. So, really you need a balance wheel clock

It just so happens, alarm clocks are cheap and cheerful balance wheel clocks and have easy access to the fast-slow mechanism on the back. I have pushed this one right over to Fast to see what happens. I'm expecting to have to adjust it a couple of times to get it dead on. On the other hand, running a bit faster is OK for a couple of hours of observing.

Fullerscope catalogue: http://geogdata.csun.edu/~voltaire/classics/fullerscopes/BCFcatalogue_1985.pdf Page 13, Paragraph 2

Or you could get a 'phone app

Richard

[ghostdance]

I remember when a Westclox Big Ben was quite the alarm clock to have Even I had one!

Very nice. Took me back...

[RLWP]

For other clock bodgers. After approx twelve hours the clock has gained around four minutes. It looks like around half way across to Fast will be a better first guess

Richard

[philj]

Gosh thats taken me back, I did this from the 1985 fullerscopes catalogue with an old smiths kitchen clock back in the day

[beamer3.6m]

What is the purpose of a sidereal clock.

[Scooot]

The sidereal time at this moment in my location is 03.23 in 2 minutes mirfak will be directly overhead (crossing the meridian) because it's right ascension is 3.25. It measures star time. I don't really need a clock these days to know that, as plenty of apps will tell me the same info.

[teleskopjo]

If the celestial sphere rotates once a day why should sidereal clock run faster than a normal one?

[RLWP]

If the celestial sphere rotates once a day why should sidereal clock run faster than a normal one?

Because the earth rotates 365 times in a year AND goes around the sun once. So there's an extra day in a sidereal year, or four less minutes in a sidereal day

Does this help:

http://astronomy.swin.edu.au/cosmos/S/Sidereal+Day

Richard

[Scooot]

Because the earth rotates 365 times in a year AND goes around the sun once. So there's an extra day in a sidereal year, or four less minutes in a sidereal day

Does this help:

http://astronomy.swin.edu.au/cosmos/S/Sidereal+Day

Richard

That's a good illustration. So the earth needs to spin about 361° for the sun to be overhead again ie an extra 4 minutes.

[RLWP]

That's a good illustration. So the earth needs to spin about 361° for the sun to be overhead again ie an extra 4 minutes.

Zackly. It's why the stars move across the heavens night by night

Richard