Choosing stars for GoTo alignment.

[deejayry]

I've been getting on reasonably well with my HEQ5 Pro mount, most of the time i have had a good reliability with the GoTo functions, however i am not sure i am choosing correct alignment stars.

sometimes I find that the mount just doesnt want to play ball.

So far i have only been using 1 star alignment, mainly because i am a little confused on what stars to choose.

Following is some pointers on how to choose appropriate alignment stars:

One Star: Choose a star closer to the Celestial Equator (smaller declination absolute value).



Is the Celestial equator the same as the ecliptic?

normally i have used Aldebaran as my alignment star, is it a good one to choose? if not could someone suggest another star?

[Siguy]

The celestial equator is 0 degrees latitude on the celestial sphere. Aldebaran is close to the equator but Orion's belt stars are right about on it.

[hhEb09'1]

Is the Celestial equator the same as the ecliptic?The celestial equator is 90 degrees from the north star, Polaris. The ecliptic is inclined by 23 degrees to the celestial equator--so they cross. Probably the brightest star close to either crossing is Zavijava, beta Virginis, but it's less than mag. 3

Wow, I just noticed that around the second week in October, 2009, Venus, Saturn, and Mercury all gather there! You might be able to see them lined up in the early morning.

[RickJ]

Going astray is rather common with one star alignments. Also never all that accurate unless the scope is very level if used in alt azimuth or polar aligned accurately if equatorial. 2 or 3 star alignments are better. Just pick three well separated in different parts of the sky. Many of today's mounts will pick them for you once they know your date, time and location. Though you need a good sky as they don't know where the trees and houses are and seem to pick ones behind something. Better to learn what stars it uses and where they are in the sky then you can pick three that are in view. Contrary to advertising, knowing the sky is a great help with go-to mounts!

Rick

[deejayry]

ok thanks for the advice guys, for now i will stick with the 1 star allignment, but i will try using one of the stars of orions belt... Then i will learn the locations of some more suitable alignment stars for 2 or 3 star alignment.

I am meeting with the Bristol Astronomical Society for the third time tonight, and if the weather is good after the meeting some members are going to the clubs observatory, hopefully i can get a few pointers from them.

[aurora]

For a two star alignment, it helps to find two stars that are not close in either right ascension or asimuth. In other words, pick two bright stars that are not close together, and are in different parts of the sky.

[hhEb09'1]

ok thanks for the advice guys, for now i will stick with the 1 star allignment, but i will try using one of the stars of orions belt... Then i will learn the locations of some more suitable alignment stars for 2 or 3 star alignment.If you want bright, easily recognized stars, Orion also has Betelgeuse and Rigel, both within 5 or 10 degrees of the celestial equator. If Orion is not visible, Altair in Aquila probably is, it's also bright (one of the stars of the Summer Triangle with Vega and Deneb) and as close to the equator. Come to think of it, the Summer Triangle makes a nice wide separation for three bright stars--any of which are good candidates.

[winensky]

I agree with Rick. 3 star alignment will give the most accurate alignment. The bonus is as the year progresses you will learn which new bright stars are rising so by the end of a year you will have a mental map of a couple of dozen stars to work with. I know the mfg say not to be too fussy with polar alignment but reasonable care will make it easier to identify stars directly from the go to.

Kind regards
Matt