Map the Sky: Charting Stars & Planets Pencil & Paper Style

[Opus_723]

I was wondering how someone would go about charting stars on their own, pencil and paper style. Particularly, I was curious how astronomers charted the positions of stars and paths of planets hundreds of years ago, and was hoping to replicate this. I understand it's probably very involved, but maybe there are some resources on the web I haven't been able to find?

 

[NobodySpecial]

Start with what angle your hand, finger, finger joint give held at arm's length
(if you didn't do much boy scout map reading an army artillary manual is a good guide)

Then just get some graph paper and go out and draw.
So there is two bright stars one finger width apart and 3 fainter ones a hands width below them, and so on.

It's a great way to learn the constellations

 

[turbo]

I was wondering how someone would go about charting stars on their own, pencil and paper style. Particularly, I was curious how astronomers charted the positions of stars and paths of planets hundreds of years ago, and was hoping to replicate this. I understand it's probably very involved, but maybe there are some resources on the web I haven't been able to find?

Have you hear of Tycho Brahe? There is no need to re-invent the wheel, and you would need a fortune to come up with instruments that would duplicate the accuracy of his measurements. Kepler used these measurements to refine our concepts regarding planetary motion. You can't do any of that with pencil-on-paper sketches. You need accurate time-keeping, accurate altitude measurements, and accurate transit-times to establish the celestial positions of visible objects.

 

[Borek]

You need accurate time-keeping, accurate altitude measurements, and accurate transit-times to establish the celestial positions of visible objects.

That's not entirely true. You can make quite a good map just by measuring angles with a sextant. Other data is needed "only" to correctly orient the map.

 

[turbo]

That's not entirely true. You can make quite a good map just by measuring angles with a sextant. Other data is needed "only" to correctly orient the map.

I beg to disagree. Without a coordinate system, all you'll have is a drawing, not a map. To accurately place celestial bodies on a map, you need to measure their Right Ascension as well as their Declination, and that requires precise timing. That goes to the heart of the longitude problem facing mariners before the invention of accurate chronometers. They could judge their latitude quite well, but without accurate time-keeping, longitude was a huge problem. In fact, the man who finally solved that problem by inventing the marine chronometer was awarded the modern equivalent of almost $5 million by Parliament.

The Greenwich observatory was a "transit" observatory, like Brahe's, and it became the standard time-reference for British navigation, which is why we have GMT as a modern time reference. As an interesting (perhaps) aside, until the establishment of official time-zones in the US, railroads had stations with all kinds of various local times. Not so much of a problem for a man on foot or on horseback, but the speed and efficiency of rail-travel brought time-differences back into focus, though in a much different fashion than the nautical problem.

http://en.wikipedia.org/wiki/John_Harrison

 

[russ_watters]

...so you need a sextant and a clock. So what's the big deal?

 

[Borek]

To accurately place celestial bodies on a map, you need to measure their Right Ascension as well as their Declination, and that requires precise timing.

No. You are thinking inside the box.

Knowing all angles (or well selected subset of angles) you can make a very precise map, in an arbitrary coordination system, defined by any two selected stars (well, not exactly by any two, angle between them can't be 180 deg).

There will be a problem with the map - its coordination system will be not linked in any way to Earth. For that you need something more, that's where your post fits.

 

[Vanadium 50]

...so you need a sextant and a clock. So what's the big deal?

Indeed, I suspect more people own clocks than own sextants.

But Borek is right - you can make a perfectly fine map without a clock. The problem is combining that map with other people's maps. Then you need either a clock (per map) or enough overlap.

 

[Opus_723]

Well, I don't need or want to create a map to Brahe's standards. I'm not looking for absolute, pinpoint accuracy, as I won't be really using the map for anything. This is mostly just for fun. I simply want to create a reasonably accurate map of the sky using rudimentary instruments. Surely people made sky maps before Brahe? A sextant and clock sounds perfect. Any ideas where I could learn how to do that?

 

[turbo]

Are you handy with tools? You could make a home-made transit telescope and mount it on a large vertical setting circle marked off in degrees of declination. Align it directly north and south and as brighter stars come close to that N-S line read off the time that they cross your field of view and record the time as the local right-ascension of the star and read the declination off of the setting circle, then mark the position of the star on a gridded paper. That's the old-fashioned method. Of course, lines of right ascension converge as you approach the poles, so this simplified method would work best at lower declinations where the lines of declination and right ascension are more "parallel".

 

[Jadaav]

Are you handy with tools? You could make a home-made transit telescope and mount it on a large vertical setting circle marked off in degrees of declination. Align it directly north and south and as brighter stars come close to that N-S line read off the time that they cross your field of view and record the time as the local right-ascension of the star and read the declination off of the setting circle, then mark the position of the star on a gridded paper. That's the old-fashioned method. Of course, lines of right ascension converge as you approach the poles, so this simplified method would work best at lower declinations where the lines of declination and right ascension are more "parallel".

Hi,

I want to know how to "make a home-made transit telescope" please. Can you help me with it ?

I don't know what to do.