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Avx tracking issues

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#1 Sidwin

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Posted 14 September 2019 - 09:50 PM

I noticed that my mount doesn’t keep up with the objects I’m tracking. Even with 26mm I noticed the moon is moving. Is there a setting or something i need to enable? I tried with Jupiter and Neptune I had to move the scope to keep it in my view finder. I was thinking of trying to use my slr.

#2 Jim Waters

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Posted 14 September 2019 - 09:59 PM

What RA rate / mode do you have the hand-controller set to?  Is the mount polar aligned?

 

The moon, planets and stars track at different rates.

 

EDIT - From the manual.

 

Sidereal – This rate compensates for the rotation of the
Earth by moving the telescope at the same rate as the
rotation of the Earth, but in the opposite direction. When
the telescope is polar aligned, this can be accomplished
by moving the telescope in right ascension only.
Lunar – Used for tracking the Moon when observing the
lunar landscape.
Solar – Used for tracking the Sun when solar observing
with the proper filter.


Edited by Jim Waters, 14 September 2019 - 10:03 PM.

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#3 james7ca

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Posted 14 September 2019 - 10:12 PM

As Jim said, but it could also be your polar alignment.

 

Also, the moon moves at a slightly different rate almost every night and it also moves in both R.A. and Dec. and most (all?) mounts don't track the moon in Dec. and they only use a single, average tracking rate for R.A. What this means is that the moon will drift somewhat even if you are doing everything right and even if the mount is working correctly. Also, you'll see night-to-night (moon phase and time of the year) differences in how well the mount will track on the moon.

 

However, I expect that most of the OP's issue is caused by not using the lunar tracking rate and perhaps from not having a good polar alignment (the latter would also affect the planets, like Jupiter, etc.).


Edited by james7ca, 14 September 2019 - 10:20 PM.

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#4 aa6ww

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Posted 14 September 2019 - 10:40 PM

It could also be your battery volage has dropped and not providing enough voltage to run your mount. I just read yesterday that the AVX is very sensive to slight voltage variations. Measure the input voltage when the mount is running. 

 

 

 

...Ralph


Edited by aa6ww, 14 September 2019 - 10:41 PM.

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#5 Sidwin

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Posted 15 September 2019 - 09:02 AM

Thanks for replies. I believe I’m sidereal. I’m using a 110v adapter so power is probably not a problem. I have mine polar aligned. I use my red dot and what I do is adjust the mount manually to get everything aligned to Polaris. Then I go through the alignment and I usually do 5-6 points whatever the handheld tells me to do. Then I noticed at the final alignment it tells me I think drift??? It does really well getting to the location if I tell it to find Jupiter or m23. I’ve seen guys take pictures with 3min shutters. That would be almost impossible for me. Thanks - Sid

#6 Sidwin

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Posted 15 September 2019 - 09:19 AM

I’ll go check my ra rate and report back.

#7 SkipW

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Posted 15 September 2019 - 10:12 PM

Thanks for replies. I believe I’m sidereal. I’m using a 110v adapter so power is probably not a problem. I have mine polar aligned. I use my red dot and what I do is adjust the mount manually to get everything aligned to Polaris. Then I go through the alignment and I usually do 5-6 points whatever the handheld tells me to do. Then I noticed at the final alignment it tells me I think drift??? It does really well getting to the location if I tell it to find Jupiter or m23. I’ve seen guys take pictures with 3min shutters. That would be almost impossible for me. Thanks - Sid

My AVX just started misbehaving recently. It would start up correctly, but when asked to slew, sometimes it would just oscillate back and forth by 15° or so (that's a guess) in Dec, but not actually go anywhere (slew was OK in RA). If I cancel the slew by pressing a direction button, it would immediately stop slewing in RA, but Dec changed from back and forth, to continuous slew in one direction, and the only way to make it stop was to turn the mount off. This was using the Celestron 5A AC adapter that's worked fine for years.

 

It had occasionally done this for the last couple of weeks, but would usually work correctly after a power cycle. But it did that every time I tried it yesterday.

 

Bummer! I really need this mount to be working for the next few weeks.

 

Taking a page out of my own book (I had suggested someone whose Celestron mount was acting up check the power supply and cable), I remembered that it had worked the last time I ran from battery power, so I put it on the little 12V AGM motorsport battery used for portable operation. It worked flawlessly every time. I wonder if the capacitors in the AC adapter are failing and there might be some "hash" on the 12V DC that is  confusing the computer. 

 

Has anyone encountered this?

 

I’ll go check my ra rate and report back.

RA tracking rate defaults to Sidereal when it's powered up. It might retain a different rate through a hibernation; I don't know, but might test that next time I get a chance.


Edited by SkipW, 15 September 2019 - 10:13 PM.


#8 Stelios

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Posted 16 September 2019 - 01:59 PM

Thanks for replies. I believe I’m sidereal. I’m using a 110v adapter so power is probably not a problem. I have mine polar aligned. I use my red dot and what I do is adjust the mount manually to get everything aligned to Polaris. Then I go through the alignment and I usually do 5-6 points whatever the handheld tells me to do. Then I noticed at the final alignment it tells me I think drift??? It does really well getting to the location if I tell it to find Jupiter or m23. I’ve seen guys take pictures with 3min shutters. That would be almost impossible for me. Thanks - Sid

People who take 3-min subs (sub-exposures aka "pictures") usually guide their mounts. Note that you don't take long subs when imaging the moon or planets, you take videos (long subs would completely saturate the moon or planets). Also for planets (but *not* for DSO--galaxies, nebulae, globs, etc.) a *little* drift is not that important as the software will align the images.

 

Polaris is a significant distance (about 45') from the north pole. This doesn't much matter for visual, but most definitely matters for astrophotography. With your AVX the best way to polar align in the absence of a guidescope, is to use ASPA (All-Star Polar Alignment), it's a capability of your hand control. There are better ways but ASPA is not bad. It should get you within 10' or so. 



#9 bmurphy495

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Posted 18 September 2019 - 12:21 AM

My AVX just started misbehaving recently. It would start up correctly, but when asked to slew, sometimes it would just oscillate back and forth by 15° or so (that's a guess) in Dec, but not actually go anywhere (slew was OK in RA). If I cancel the slew by pressing a direction button, it would immediately stop slewing in RA, but Dec changed from back and forth, to continuous slew in one direction, and the only way to make it stop was to turn the mount off. This was using the Celestron 5A AC adapter that's worked fine for years.

 

 

Like this? https://youtu.be/GUZ_sx6_HIY

 

Loose encoder, it's rotating on the shaft during a slew.

 

B



#10 mclewis1

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Posted 18 September 2019 - 08:05 AM

What Stelios said.

 

A few other comments ...

 

- the different tracking rates don't make enough of a difference at low magnifications to notice. If you notice drift at lower magnifications it's just about always polar alignment.

 

- power doesn't affect the tracking rate (the mount synthesizes the correct frequency digitally to keep the RA motor tracking at the correct rate). Low power does cause all kinds of problems so having a solid 12v source is important, but it doesn't change the tracking rates.



#11 SkipW

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Posted 18 September 2019 - 06:19 PM

Like this? https://youtu.be/GUZ_sx6_HIY

 

Loose encoder, it's rotating on the shaft during a slew.

 

B

Similar, but slower, and in Dec, not RA.

 

Interestingly, I tried again this morning and, on a whim, reversed the cable connecting the main electronics to the Dec assembly, and it works correctly. I'm not sure if that is the problem or not. If it is, it may have been just a matter of re-seating the connector or perhaps one end of the cable works more poorly in one of the connectors than the other.



#12 bmurphy495

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Posted 18 September 2019 - 09:51 PM

Similar, but slower, and in Dec, not RA.

 

Interestingly, I tried again this morning and, on a whim, reversed the cable connecting the main electronics to the Dec assembly, and it works correctly. I'm not sure if that is the problem or not. If it is, it may have been just a matter of re-seating the connector or perhaps one end of the cable works more poorly in one of the connectors than the other.

There is a little plastic cap on the back side of the motors that you can pop off and look at the encoder. Mine fell off in my hands when I did that. 

 

Let us know if re-seating the connector fixes it.

 

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#13 SkipW

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Posted 19 September 2019 - 06:20 PM

There is a little plastic cap on the back side of the motors that you can pop off and look at the encoder. Mine fell off in my hands when I did that. 

 

Let us know if re-seating the connector fixes it.

 

Thanks for the suggestion. I think I have found and fixed the problem, and it does seem to be related to the encoder, but it's not what you think wink.gif.

 

I've started a new thread here with the solution and any follow-on discussion.


Edited by SkipW, 19 September 2019 - 06:25 PM.

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