Thread: Star Align
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Old 19-01-2021, 03:36 AM
astro744
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astro744 is offline
 
Join Date: Apr 2007
Posts: 1,244
A compass will only give you magnetic bearings which you don’t want unless you apply the offset magnetic deviation to your location. If you still want a good compass try any orienteering compasses that are oil filled as these come to a bearing and sit there without oscillating rapidly. (Silva brand is good but there are others).

Best way to find true south is to find true north first using the Sun. You need a vertical stick and a horizontal surface. The true north-south line is the diretion of the shortest shadow. This is best done in winter as in the summer the shadow is short as the Sun is a lot higher.

I have used the Sun shadow method but I also use (and prefer for its speed) the the following method. Get any astronomy app whether on computer (PC) or mobile device. (You do not need the device outside). Stellarium is free so I’ll describe it.

Do this in the morning well before the Sun reaches its highest point in the sky so that you do not miss that point.

1. Make sure your location is in Stellarium.
2. Make sure Daylight saving is enabled or not to match your location.
3. Position the North horizon in the bottom centre of screen. Turn cardinal points on to see ‘N’ indicator.
4. Turn on Alt/Azimuth grid (not RA/Dec equatorial grid).
5. Zoom in or out until the Sun is on the right of screen with N at bottom of screen. The horizon should be slightly curved, (not too much).
6. Turn OFF atmosphere to show a black sky with stars if you like as it makes it easier to see the grid.
7. Increase the time factor to speed up the motion of the sky (just a little until the Sun is moving slowly right to left.
8. When the sun reaches the 0/360 deg azimuth line (true north), pause the time to freeze the movement.
9. Note the time. This is the transit time when the Sun reaches its highest point and is situated on the N-S meridian.
10. Go outside close to this time. When the time is reached the Sun is at transit. Drop a vertical line to the horizon. This is true north. 180 deg in the other direction is true south. I mark the fence in my yard from where I normally place my telescope in the direction of true south.

Of course you don’t need to do steps 1 to 8 if you can simply get the transit time of the Sun either from an app such as Sky Safari (find sun and click on it and it will show transit time), or search the web for transit time (for your location).

Note you can do this at night for transiting stars. Pick stars closer to the horizon and not ones overhead. Even with the Sun this method is easier in winter when the Sun is lower in the sky.

Enjoy your new ‘scope. Try and also learn the sky without the aid of GOTO as it will be more rewarding ultimately as you’ll get to know when and where things are and how they move. You can still rely on GOTO to get you there but I still recommend a chart and manual navigation so you know where ‘there’ is. Stellarium is a great tool for this. And yes join the local society if you like, (subject to any covid requirements). CAS used to meet at Stromlo, perhaps still do.
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