Which North?

I just came across a nifty gadget. The Align-Mate from digitalastronomy.com is an "eyepiece button" with a compass on one side and a bubble level on the other that is used when setting up an LX90. According to the description, you "rotate the instrument until the 'N' on the compass lines up with the telescope tube" and then make "a small local adjustment for your true north deviation."

I assume this means that you adjust for the difference between magnetic and true north. My question is "how do you make the small local adjustment?" The instruction manual for the LX90 simply states "turn the telescope horizontally until it points North" and the instructions even recommend not paying "undue attention" to precise polar alignment.

So, how precisely do I need to make the north alignment and if I use a compass, how do I make the "small local adjustment" referred to above. Thanks.

Check for the local magnetic deviation
http://www.satcruiser.com/azel.htm ( link shows deviation map)
and just set the compass to the degree of error for your area. IE "14'" Here it would be 14' subtracted from the north heading so it would be 346' for true north.
Floyd

Dave,

As I remember the LX 90 as with other Meade Go-to's, only require a rough alignment of the scope to Polaris. This is done by visually pointing the OTA North. In Alt-az mode this should get all your Goto's within the supplied eyepiece.

Use of the equatorial wedge, is another issue. Use the compass on the wedge to give the off-set from mag-north . Where I am located ( CT) it is 11 degrees East (looking North)

Using the compass on Meades mount and using the info in the owners manual under "Polar Aligned" should get you close and educated quickly.

I found the LX 90's goto's to be very accurate even with the quick setups

Have a great day and a dark night,

Tom T.

As far as an LX90 is concerned, in actuality, if you know the major stars of the sky, all you really have to do is level the instrument base and do a two star alignment without ever having to worry where north is.

Let's say you know the stars Capella and Arcturus (try to use two stars at opposing ends of the sky). Unlock the R.A. and Dec. knobs so the OTA swings freely. Choose two star alignment (or easy align) and choose the first star (say, Capella) and press enter. The motors will whirr away but you'll notice that nothing happens, as it shouldn't since you unlocked the R.A. and Dec gears. When Autostar asks you to centre Capella (and beeps), simply manually point the telscope to Capella (assuming you know where it is), lock up the R.A. and Dec and fine tune using the Autostar controls. When you choose the second star and press enter again, the telescope should then point you very close to the second star (say it's Arcturus). From this point ONLY use the Autostar controls to centre the star. You should have perfect alignment at that point without ever having to point the telescope north at all.

Levelling the OTA and Pointing it north ONLY serves to tell Autostar where to look to find the alignment star. If you already know where that alignment star is, you don't need north at all - magnetic or true.

Best of luck.

Derrick.

Back to David's original post - I have one of those gadgets ordered, as I can't find the expensive compass I bought years ago.

I think it's a neat idea.