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Guy Wells

AVX Advanced Tracking issues and Polar Alignment.

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Hi there. I'm a planetary guy with a Meade LT6 ACF Alt/Az mounted. No problems...

The issue is happened to a friend of mine with his new AVX Advance + C9.25.

I have minimal experience using EQ mounted scopes.

Here is what we do to setup:

  • Level tripod with one leg pointed north.
  • Add scope align the notches on the mount. Set latitude to our position. No polar scope so we just roughly centre Polaris through the 'hole'
  • Perform either a 2 star alignment or use the Star Sense. After this we slew to Saturn. It's towards the left of the FOV.
  • Now we use ASPA. It tells us we have a slight error. We choose a star and it slews to it. The slews to the place it ought to be if polar alignment was correct.

We are now supposed to adjust the Alt and AZ of the mount to centre the star, in first NS and EW. This is where we seem to stuggle. I manage to centre the first and second part. Then the scope loses the plot. Alignment reads XXX XXX. Trying to slew to Saturn again will move the scope into very peculiar positions! Looking at the latitude dial now reads something completely different to our actually location....

Any obvious errors that I am making?

Thanks for any input.

Skips

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I have the same mount, but am still at the beginners stage.

One thing i noticed in your rundown is that you have one leg pointing north.

On the tripod before you put the head on, there is a peg sticking up. The peg that you tighten the Azimuth knobs on. That peg should be pointing north.

It is possible to mount that peg on the same side as one of the legs, but the factory mounted way is to have it in the middle of two legs "to keep the scope from hitting a leg when slewing".

If you have the peg in the factory mounted hole then you are of by 60* or so.

The peg should also be pointed at true north and not magnetical north.

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Yes, sorry. The peg is north and it's in it's stock tripod position.

Edited by Ras Skipper

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I use the AVX very successfully so you must be doing something wrong. After doing an alignment and at least calibration stars you check the Polar align and it's out. You then follow the ASPA routine and then you should perform another alignment before checking the error on the PA. Then you do another ASPA and you should be somewhere near PA. If you follow the instructions to the letter you should be ok. I didn't understand your comment about the " Looking at the latitude dial now reads something completely different to our actually location...."

If you set the latitude correctly to start with then it must be near to what you set unless you have done a huge adjustment during ASPA and you should not have to do that.

When you do ASPA pick a star high in the sky (not Polaris) near to the Meridian.

Peter

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after you've done the polar align routine - ie pointed to a star, the mount nudges it offset a bit which you then adjust back to center with the alt and az knobs - you need to put the mount back into home position again (facing north, weights down) and do a new star-align - were you doing that ?

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Hi there. Yes, it gives an offset. We adjust the alt az to centre the star. It does then ask for an EW alignment too. Anyway turn off then on. Re do alignment and then the error is xxx xxx.

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It is supposed to be clear tonight. I guess whilst my rig is imaging we can spend the night not doing anything useful with his scope LOL!

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I don't turn mine off after ASPA - I do what the manual says and do an Unsync and then another alignment. 

Peter

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The end result ought to be the same though. Doing an alignment then checking for any offset in the mount?

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I can get 4 mins unguided after an ASPA alignment so yes weird.

Peter

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I have the same set up as you and I can get several minutes of pretty decent tracking. I have noticed a few weirdnesses like yours - one time it said my latitude error was like 80 degrees and then once it tried to slew way past hitting the tripod (I shut it off, which I read somewhere is bad to do, but pressing the motor speed button seems to stop it). 

I always add two more stars to the initial alignment - this really does help with the initial finding and centering (I centre the camera sometimes too). Once my alignment for gotos is done, then I check the polar alignment error. I was making a stupid mistake initially by moving along the latitude scale to the right instead of to the left (i.e., it reads right to left, not left to right - so 43 is to the left of 40, not to the right).  IF you turn it off and on, make sure your time is right and if your lattitude/longitude info is off, you should check and see where it is getting that info from. 

The only real difficulty I've had is moving the mount in alt-az since it is very tight and sticky... 

--Ram

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