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To HyperTune or Not - That is the question

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#1 mtb.daily

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Posted 23 May 2009 - 03:22 PM


Hey gang,

I have had no end of frustration trying to get nice round stars. They always seem egg shaped.
Worse, the direction of elongation is not consistent.

My mount is an EQ-6 Pro.

On my OTA, the C11, I have re-aligned the primary, secondary and corrector plate as per Celestron specs.
I even tried using my WO80 instead of the C11 and still get eggs for stars. :(

Its not in a particular part of the image, it is usually every where but not always.

Now, I have done polar alignment many times, I did 3-star alignment many times and still EGGS :(

Now, the other night, I though I would do a PE check using PHD and PEAS. I got wonderful data but, I forgot to disable the guiding output.

Here is the PEAS output.

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#2 mtb.daily

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Posted 23 May 2009 - 03:24 PM


Now, as you can see fro the previous image, the MAX PE is only .71 aSec. Not bad but, as I stated above, this is guided. I will do an unguided session the next clear night.

BTW: The object was the star SPICA.

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#3 mtb.daily

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Posted 23 May 2009 - 03:25 PM

The next screen shot...

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#4 mtb.daily

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Posted 23 May 2009 - 03:26 PM

And the next

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#5 mtb.daily

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Posted 23 May 2009 - 03:28 PM

Now, the snaps show the various PHD Settings and the Guider is the KWIQ Guider (based on a 50x9 finder with the QHY5 Guider attached).

So, given this info, and the egg shaped stars, should I hyper tune my EQ-6 Pro or, is the problem somewhere else ?

Any ideas would be help full.

Thanks,
-Jerry

#6 David Pavlich

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Posted 23 May 2009 - 09:34 PM

First, I'd set the loop for 2 seconds instead of .5. Question: How often is PHD sending inputs to the mount? Is there long periods of no commands or do the commands come frequently? I ask because one of three things is happening if you're getting a lot of correction from PHD; either the PA is not good enough, the PE is so bad that the guider can't correct it or the seeing is so bad that the guider is actually chasing the seeing. My money is on the PA routine or the seeing. How long can you go without the star drifting from the crosshairs without PHD guiding the mount? And if the seeing is bad, you might as well pop in an eyepiece and do some viewing because the guider will go nuts trying to keep up.

You can try defocusing the star a tiny bit to help with the seeing, but it may just be to a point that it ain't gonna' work.

As far as the hypertune is concerned, if you have the time and patience, see Bobby's tutorial (stargazer27). You can get some nice tips there. It'll only make your mount better.

David

#7 Jerry3672

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Posted 24 May 2009 - 06:42 AM

Yes- hypertune.

If you do hypertune than take the time to lap your worm gear. I used 600 grit compound on my worm.

here is a graph of before the lap. This is with PHD disconected from the mount

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#8 Jerry3672

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Posted 24 May 2009 - 06:44 AM

And now see how much more smooth.

So PHD will not have to chase bumps due to a sticky mount.

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#9 mtb.daily

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Posted 24 May 2009 - 05:42 PM

What do you mean 'lap the worm gear' ?

-Jerry

#10 mtb.daily

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Posted 24 May 2009 - 05:44 PM

Also, what do you mean 'PHD disconnected from the mount' ?

Jerry

#11 mtb.daily

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Posted 24 May 2009 - 05:49 PM

David, what did you mean 'PA' ?

Jerry

#12 Jerry3672

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Posted 24 May 2009 - 07:38 PM

I disconnect PHD from the mount to measure the PE. Hit the brain on PHD and select "disable guide output". The PHD log will then be your PE.

Lapping the worm gear is just as it sounds. You would use a fine grit lapping compound on the worm and run the gears until they run smooth. I’ve used lapping compound for years, but if you have never lapped anything, then you should fine someone who has and ask for help. The best tip for lapping the worm gear is to keep the compound away from all bearings. It only takes a small amount of compound in a bearing and it will be junk.
Next tip- after lapping clean the gears very well. I have a sonic cleaner, but you can do a good job with brake parts cleaner from an auto store.

#13 David Pavlich

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Posted 24 May 2009 - 09:48 PM

David, what did you mean 'PA' ?

Jerry


PA=Polar align.

David

#14 mtb.daily

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Posted 24 May 2009 - 11:49 PM

Thanks, and Thanks....

Jerry

#15 mtb.daily

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Posted 25 May 2009 - 12:21 AM


Jerry3762,

thanks for info on Lapping.

I did some research on Internet and found a number of web sites that talk about it including one where a person lapped the worms of a Losmandy G11. Very good description as well as pics.

Now, since the EQ-6 Pro/Atlas mounts have fixed positions for both the worm and the worm gear, and the fact that lapping will, in essence, remove small amounts of material from both parts of the worm drive, how do you tighten, or snug up the two parts when finished ? Its not like these mounts have adjustments for these gears. They only go into one spot.

Or, am I missing something.


David,

PA is not something I have too many issues with. I have adjusted my polar scope to be sure it is aligned with the polar axis of the mount and I always perform a PA before any usage of the mount.

The star, when guiding is turned off, typically stays close to where it should be but, it's not perfect as this is not a permanent setup. Every time I use it, I have to setup everything.

Perhaps I may have to spend more time learning to drift align.

-Jerry

#16 rmollise

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Posted 25 May 2009 - 07:05 AM

Jerry3762,

thanks for info on Lapping.

I did some research on Internet and found a number of web sites that talk about it including one where a person lapped the worms of a Losmandy G11. Very good description as well as pics.


I doubt you will find the road to round stars involves "hypertuning" or any other futzing with the mount. The usual way to get them is by fine-tuning the PHD settings--experiment with various settings and guide exposures. Also...

Guide exposures shouldn't be longer than about two seconds nor shorter than 1 second.

Set guide rate in the HC for .5.

Are you drift aligning? If not, do so.

Be scrupulous about eliminating ANY potential flex between scope and guide scope.

I think you will find these things will work much better than attacking the worm gear.

;)

#17 Jerry3672

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Posted 25 May 2009 - 07:17 AM

here is a link to a tune up that shows how to adjust the backlash.

http://timsastroblog...up-for-eq6.html






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