Quote:
Originally Posted by astro744
Stellar coordinates on star charts use RA and Dec which is similar to longitude and latitude. What you also need to know is Local Sidereal Time. LST is approximately four minutes faster per day than standard clock time. You can get software or an app to tell you LST.
The LST equals the RA of any object crossing the north south meridian. In other words an object that has risen and reaches its highest point for the evening will have its RA equal the LST at that time. This gives you another way of determining LST if you know the RA of an object and it is just crossing, then that is the current LST at that time.
Dec is simply latitude. 90 degrees declination is equal to you location latitude up from the southern horizon. E.g. At 30 deg south of the Equator the south celestial pole (90 deg Dec) is located 30 deg up from the southern horizon. The celestial equator arcs from east to west and reaches 60 deg high from the northern horizon for an observer located 30 deg south of the Equator.
Orion is low in the west at sunset so you'll have to wait a couple of months before it reappears in the per dawn hours in the east.
At 19:43 Eastern Australian Standard Time the LST was 13:48. Use Stellarium and turn on equatorial grid and make sure cardinal points are showing and then look toward the N horizon.
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some good info but maybe confusing for some. with a dob, you need to know altitude (height) and azimuth (direction). if you have an eq mount then Ra and Dec can be used to find objects with all that info.
software / Appz can convert ra/Dec into alt/az. for objects the star charts at skymaps are handy
www.skymaps.com/downloads.html just make sure to download the southern hemisphere.
matt