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Init Polar Alignment -- Any Trick ?

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#1 kyang

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Posted 28 October 2013 - 10:32 PM

Hello All,

Would you please share some tricks of how to do initial polar alignment? I mean how to roughly set the mount to NCP ...

It is not too hard when I setup my iEQ30 at my backyard as there are not many stars that I can see through the polar scope.
However, during my first visit to a dark site, I have hard time to tell which star is Polaris in the polar scope.
There are just too many stars :foreheadslap:

Will it help to use a laser pointer to roughly point to NCP ? Something like: http://www.shermcraf...polaralign.html

Thanks.

-Kai

#2 Bowman

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Posted 29 October 2013 - 02:05 AM

I find that a polar scope is a hinderance and not a help. The field is too small and you can easily get lost. I center Polaris in my Telrad and that gets me close enough to Polaris to do an iterative polar alignment. Five or six iterations and I am done.

Larry Hoffman

#3 Eddgie

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Posted 29 October 2013 - 09:01 AM

Unless you are imaging, it is not usually necessary to do an accurate polar alignment. You only need to be within a fiew degrees, and you can acheive this with a compass.

But unless you are imaging, an exact alignmen simply is not usually required. Just use a compass and sight the mounts alignment to north using the north leg and the center and sight along the centerling of your compass needle (being careful to compensate for megnetic declination for your area). Level the mount and just use the scales on the mount to set the latitude for your area. These scales are usually not all that accurate, but they are close enough for a Go-To mount to work.

If you observe from the same loction in your yard, next time you observe, consdider doing a polar alignment with the handset software before you take the scope down, and then mark the positions of the tips of the legs. If it is a hard surface like concrete, make tiny dimples in the surface with a masonay drill, and if it is grass, drive 6" lenghs of pipe into the surface at the point where each leg tip contacts the ground.

This way, next time you set up, you just put the mount on the marks and you never have to polar align agian.

And this. Most Go-To GEMS do not track in DEC, only RA, If your alignment is not perfect, the Go-To will work beautifully, but you may find that in time, an object will drift out of the field because if there is an error, the fact that the DEC motor is not driving to compensate for the north/south drift will become evident. But in most cases, it takes many minutes for a target to drift from the field and you can touch up using the hand control.

The best way to avoid fussing with it in the future though is to carfully level the mount the next time you use it, and then do a polar alignment routine using the built in sofware after a rough alignment, then remember to mark the leg point postions on the ground.

Now, next time you set up, just position the tips of the legs on to your marks, level, point and shoot.

In my case, I even used to just accept the "Last Alignment" and if I was using a smaller scope, this was often good enough so that I did not even have to do another alignment. Not all mounts store the last alignment data though. Usually these are mounts like the CGE that has a built in battery to store this data.

The longer the focal lenght of the scope though, the more likey it will be to have to re-align.

But even my C14 could sometimes get away without another alignment because I had my leg tip positions marked into my patio with dimples and could get the CGE set up with a pretty high degree of repeatability.

Again, unless you are imaging, your alignment does not really have to be all that close. A compass and the latitude scales on your mount are all that you really need to get excellent Go-To performance.

#4 Cliff Hipsher

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Posted 29 October 2013 - 11:36 AM

How about this:

Set the mount to the home position and power it up. Make sure that time, date, and LAT/LONG are correct. DO NOT run an alignment. Tell the mount to GoTo Polaris. The mount should slew to were it thinks Polaris is based on time, date and geographic position. Use the manual Azimuth and Latitude adjustments to put Polaris in the center of your eyepiece. This is exactly how my Meade LXD75 does a One Star or Polar alignment.

#5 mpgxsvcd

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Posted 29 October 2013 - 02:38 PM

How about this:

Set the mount to the home position and power it up. Make sure that time, date, and LAT/LONG are correct. DO NOT run an alignment. Tell the mount to GoTo Polaris. The mount should slew to were it thinks Polaris is based on time, date and geographic position. Use the manual Azimuth and Latitude adjustments to put Polaris in the center of your eyepiece. This is exactly how my Meade LXD75 does a One Star or Polar alignment.


Brilliant and Simplistic!

#6 Roy McCoy

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Posted 30 October 2013 - 01:11 AM

+1
+1
+1!

#7 Roy McCoy

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Posted 30 October 2013 - 01:19 AM

Kai,

If you can set up before sundown it may help because Polaris is one of the early stars you will see.

#8 Aquarist

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Posted 30 October 2013 - 07:08 AM

How about this:

Set the mount to the home position and power it up. Make sure that time, date, and LAT/LONG are correct. DO NOT run an alignment. Tell the mount to GoTo Polaris. The mount should slew to were it thinks Polaris is based on time, date and geographic position. Use the manual Azimuth and Latitude adjustments to put Polaris in the center of your eyepiece. This is exactly how my Meade LXD75 does a One Star or Polar alignment.


Excellent idea!

#9 kyang

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Posted 31 October 2013 - 12:55 AM

Thank you guys for the excellent ideas !!!

#10 Phil Sherman

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Posted 31 October 2013 - 08:52 AM

My Atlas mount has a variable brightness LED in the polarscope to illuminate the reticle. If the brightness is set correctly, Polaris can be the only star visible in the polarscope, even from a dark site.

You can probably simulate this using a red flashlight held at an angle and pointed towards the polarscope.

There have been a couple of posts here on CN describing a way to polar align your mount before it gets dark. These require a mount controller that has a digital readout which allows you to use the accuracy of the gears to get the altitude correctly set. A GOTO to any object visible at dusk, any planet or bright star, is then used to adjust the azimuth. This technique should give you a polar alignment that's accurate enough for visual observing and a great starting point for drift alignment for imaging.

Phil






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