Sundial

[Mike Kelly]

I have yet to carve this out, but as soon as I can get a 2' piece of corian its done.

Took 2.5 hours to calculate the lines out for my location an lay it out in Partworks.

[Brady Watson]

Cool...thanks for posting. Can you point me towards some online resources to do the calculations myself and make my own ?

Thanks!
-B

[zeykr]

Take a look at http://www.shadowspro.com

A sundial has been on my todo list for some time!

[Mike Kelly]

Brady

I used the calculator at http://www.anycalculator.com/horizon...ial.htmhttp://

There is also some info at http://www.mysundial.ca/

Also the site/program that Ken refers to is good free program, but if you want to export to dxf it requires a $60 upgrade


Mike Kelly

Cool...thanks for posting. Can you point me towards some online resources to do the calculations myself and make my own ?

Thanks!
-B

[dana_swift]

Interesting project, I have also considered building a sundial. It will give you an appreciation of the motion of the earth which is not nearly as simple as it appears.

The problem is the analemma, which is a fancy word saying the sun moves around in the sky at the same time of day depending on the day of the year. It makes a non-adjusted sundial less accurate than you might think.

The sun moves north and south 46.9 degrees over a year, and east and west approximately 10 degrees. The east west motion results from the earths orbit around the sun not being a circle. That motion is independent of your position on the earth. It makes summer days last longer and longer as you move further from the equator, not setting at all for parts of the year above the arctic circle.

If the sundial is mounted on an Az-El mount so it can compensate for the annual analemma, the sundial can be accurate within 1-2 seconds if it is large enough to see that level of motion. Without it the error peaks at about 20 minutes.

Its no big error and shouldn't slow anybody down from putting up a sundial and having fun with it. But don't set your clocks by its indicated time, your cell phone time should be within a second.

A great conversation starter for sure..

Cool project!

D

[curtiss]

If you have your Aztec calenday next to your sundial you can correct for the analemma I think...

The little arrow thing is supposed to point at the north star which you can do at night.... or set it for solar noon in your area.

One would need two sundials, cut an hour apart, which are changed out with daylight savings time.

[knight_toolworks]

I have made a few of these. a engineer makes them and he does all the real work. I have to edit the lines to make them work and I carve them on these 24" aluminum discs that he machines flat. They show how non flat my machine is.

[khalid]

What a great topic.. I am struggling making one sundial for couple of days..using Shadowspro expert printed out one on A4 size..Now want to get the Meridian to get the direction of Pole star,,,... I will use few circle and get the shadow of the sun ...

Equation of time should be on the side of sundial to get the accurate time of the day...

[Brady Watson]

Ken, Mike & Dana - Thanks!

-B

[ironsides]

I have a Sun Dial purchased from garden shop.

It is extremely accurate once a month, right after I calibrate it to match my Atomic Watch and Daylight Savings Time

George