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Klesk14

Tips for polar aligning a CGEM.

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I've had some good and bad days while observing with the CGEM mount however as the topic says I'd like to have some tips on polar aligning.

The book does mention a few things here and there, one being balancing in DEC, however the safety screw on the dovetail (towards the back of the C11 OTA) cuts off and I am unable to balance.

Is it safe enough to remove this screw to push the OTA further forward towards the front of the mount to be able to properly balance in DEC?

Also while aligning, when should I use the hand controls on the remote or use the azimuth nobs with the latitude scale to center stars in the EP?

If anyone can help with my above concerns and provide any additional tips that would be great :D

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Firstly ensure that the mount is level.

There is a routine that allows you to polar align the scope by selecting a star, or planet to align the scope on. I've found it just a quick to purchase a polar scope First Light Optics - Celestron Polar Axis Scope. Move the mount to polar align,i.e. the 'nobs' on the mount.

With the C11 push it all the way up on the plate, this should ensure that it's perfectly balanced.

When you do the two star alignment ensure that you then add some other stars to sync onto. I find at least three other stars work perfectly. (use the handset to align perfectly with the stars)

If you need any more help, just ask.

Cheers

Edited by Willarnold
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Some CGEM users seem to say that you get just as good results if you simply rough align the mount by sighting Polaris through the whole that takes the polar scope...

I don't have enough experience of my CGEM to help but here is the routine used by Destrehan Dave (who seems to know a thing or two) which I am reproducing without permission so I hope he doesn't mind:

Step 0 is to level the mount (not critical) and rough align as outlined above.

"1) Do a 2 star alignment with 4 calibration stars.

2 Slew to a star near the meridian, close to the celestial equator.

3) On handset, press 'Align-->Polar Align-->Align Mount'

4) Scope will re-slew to the star

5) Center in the eyepiece (using hand controller); press enter

6) Scope will slew to the position where the star should be if alignment was

perfect.

7) Center the star using the physical alt/azimuth controls on the mount.

8) Return scope to home.

From there, there is some debate on whether or not you need to do a new 2-star

align or just add calibration stars. I do a full 2 star align with 4

calibration stars just to make sure."

I haven't tried this out yet (only had one night with the new mount) but if it is clear again this evening I'll be running through this routine.

Hope that this helps.

Ian

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That's sounds like a good idea to try that I'll definitely take that next time I go out. Thanks for both advice :-)

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I'm probably stating the obvious but...

I take it that when using the azimuth knobs to adjust the mount for alignment obviously with the OTA and weights on. I'll need to unscrew the threaded rod that attaches the mount to the tripod?

This seems to allow more free movement for the knobs to play with if the threaded bar isn't in. Now is this a good idea not having this secure with all the equipment on or is it still pretty safe? I wouldn't want to have everything topple over lol.

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Oh I forgot to mention earlier with my above post.

Am I better off to align with a low powered EP?

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Don't unscrew the threaded knob that holds the mount to the tripod.

Set everything up, scope and counter weights. Move the whole mount roughly to the pole star. Then use the knows to fine adjust.

For the stars get it centred with a low powered EP, then swap it out for a higher powered, and centre again.

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You don't want to remove the threaded rod, but you may need to loosen it a little. You want to avoid the mount head moving at all when you re-tighten it though.

It is much easier to go through the align procedure using an illuminated reticuled eyepiece. These are usally around 12mm but really take the guesswork out of centering the star. Make sure that your finder scope is well aligned so that the alignment star appears in the eyepiece or I sometimes use the finder scope, then a standard low power EP and then the reticuled one.

HTH

Ian

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I am having some trouble with alignment. I can polar align ok using polar alignment scope however, despite carefully following the setup sequence I find that when I select the first star in a two star alignment (usually Arcturus at the moment) the scope moves to a blank part of the sky some way off.

Should I then release the clutches on the scope to roughly position on Arcturus and finish with hand controls to finely centre the star in both the viewfinder and then the scope itself?

Any advice would be very welcome, I have carefully checked all settings so its not something like misselecting a city or daylight saving.

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The CGEM's have a Polar Aligment feature on the handset.

Level and balance the mount.

Get as close as you can with the polarscope (Have you aligned this with the axis of your mount?)

Do a 2 star align + 1 Calibration star

Once all this is done you can use the polar alignment feature, it will select a star and ask your to  center in the finderscope first and then in the eyepiece. Once that's done it will re-slew to the star, now you recenter the star in your eyepiece using the ALT/AZ blots.

Using this method i can track for about 2 min's, i guide so for me this is good enough

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