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or declination? In astronomy, declination (abbrev. dec or δ) is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle.
Are you talking about sighting a unknown object in the sky and calculating it declination and ascension. Or are you talking about taking finding a given object on map getting its known declination and ascension and then find that spot in the sky?
With my scope's goto system I have to give it the date and time and longitude and latitude. Then it goes to three targets that I "bracket". I can then enter a goto location. If I starhop by manually moving the scope it should give me hours minutes second for ascension and degrees for declination.
If you don't have "goto" you have to use "setting circle" I think the Norton's Star Atlas and Reference Handbook has the procedure for that method. Which I believe starts by locking in on a know star and matching "setting circles" on the telescope to that setting.
The two things that spurred this question are 1) trying to measure the movement of Mars away from Leo right now and 2) curiosity about how Hipparchus was able to discover precession by comparing the shift in the position of the stars from earlier observations.
I have not been able to find how the positions are measured with simpler tools.
A better locator (and better telescope) will be helpful to locate some of the less visible objects, but right now my interest is probably more basic.
Do you have a good watch and telescope? If you want a crude measurement you can put Mars on the edge of your field of view and the mark the time. Then time how the rotation of the earth takes to move a known star into view. If you do this over several nights the time will get larger and larger as Mars moves away. Or you can swap this a known star that mars is moving toward.
How Hipparchus made it's determination of precession is beyond me. I am sure it has a lot to do with inertial guidance, gyroscopes and FM.
Mars should be up over the trees here pretty soon. Thanks.
I am reading through De revolutionibus - slowly. It is interesting that he used right ascension and declination. I wonder how far back that coordinate system was used, and how it was measured.
Copernicus mentions a sextant. I found this http://digital.lib.lehigh.edu/planets/group_assign.pdf
The topic is very interesting to me.
Thanks so much for following up on this.
Anyway, from 1/19 to tonight I can report that Mars is 4 degrees closer to Pollux, according to my astronomical instrument. (That is when I remember to move my fat finger from obstructing the string.)