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AVX Not Tracking -- Or Is It?

Celestron Equipment Mount SCT
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#1 verityfalls

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Posted 22 October 2021 - 09:42 AM

Hello everyone,

 

I have a new (as of a few months ago) setup that, after a few months of tinkering and prepping, finally saw first light this week. Here's the setup I have currently going:

  • AVX Mount, polar aligned
  • 9.25" SCT (also from Celestron)
  • ZWO ASI1600GT CCD

I was under the impression that I could get pretty good tracking with just the mount on exposure times up to around 30 seconds, but I'm getting pretty heafty streaking with just 5s exposures (I've attached one so that y'all can see if you'd like). For my current needs, sub-30s is all I need, so I have not planned for an autoguide system yet. 

 

Was I wrong in thinking the AVX could handle these kinds of exposures? When I reached out to Celestron about the possibility of tracking not working, they told me to get an autoguide system; is this the way to go, or should I look more into making sure the tracking isn't actually the issue? Any advice would be appreciated!

Attached Thumbnails

  • Screen Shot 2021-10-22 at 9.05.44 AM.png


#2 bunyon

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Posted 22 October 2021 - 09:52 AM

Assuming the streaks are east/west and that is a 5s exposure, that looks like the motor is off. It's been awhile since I had an AVX, but I think it should say on the handpad if it's tracking or not. Did you do an alignment for go-to? My recollection is that once you do that, it starts tracking automatically. But, if you don't, if you just polar align the mount, it doesn't track unless you specifically tell it to. 



#3 Nemo51

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Posted 22 October 2021 - 09:58 AM

I routinely get near perfect 2 minute subs, unguided, with my avx. 


Edited by Nemo51, 22 October 2021 - 09:58 AM.


#4 bunyon

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Posted 22 October 2021 - 10:07 AM

I routinely get near perfect 2 minute subs, unguided, with my avx. 

At what focal length? If the above image was a 9.25" SCT at prime (or even with a reducer), I'd totally buy that as PE on a longer exposure (not 30s, though). I had an AVX with fairly large PE that autoguided out easily. 

 

But for 5s, there should be no streaking at almost any focal length. 



#5 DirtyRod

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Posted 22 October 2021 - 10:09 AM

I’d be surprised if the AVX would handle it unguided at that focal length. I have trouble getting consistent 60s subs on my 8” guided with a focal reducer which is about half the focal length. I could see it with a shorter refractor but I’d bet you need guiding at that FL.



#6 verityfalls

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Posted 22 October 2021 - 10:12 AM

Assuming the streaks are east/west and that is a 5s exposure, that looks like the motor is off. It's been awhile since I had an AVX, but I think it should say on the handpad if it's tracking or not. Did you do an alignment for go-to? My recollection is that once you do that, it starts tracking automatically. But, if you don't, if you just polar align the mount, it doesn't track unless you specifically tell it to. 

I did do an alignment for go-to! I followed the instruction for a 2-star align, added 2 calibrations stars for good measure, then polar aligned. When I checked for tracking on the handpad, the mount said that it was tracking EQ North Sidereal, as it should. After some more reading around online I'm thinking a firmware update and/or reset might be in order. I'll try that and see if I can get the tracking straightened out.

 

Thank you all for confirming my suspicions that this is indeed the tracking; I figured 5s was far too short to show this kind of streaking.



#7 bunyon

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Posted 22 October 2021 - 10:18 AM

I did do an alignment for go-to! I followed the instruction for a 2-star align, added 2 calibrations stars for good measure, then polar aligned. When I checked for tracking on the handpad, the mount said that it was tracking EQ North Sidereal, as it should. After some more reading around online I'm thinking a firmware update and/or reset might be in order. I'll try that and see if I can get the tracking straightened out.

 

Thank you all for confirming my suspicions that this is indeed the tracking; I figured 5s was far too short to show this kind of streaking.

It should be tracking then.

 

One thing I note: You'll want to polar align first, then align for go to. If you polar align second, that will throw off the goto alignment. But it should cause the RA motor not to track. 

 

I can't imagine it's firmware, either. If the RA motor is on and the scope polar aligned, it should track. Regardless of anything else.

 

However, there is one other thing to to check before taking action: Is this only one sub or did you do many and they're all streaked? I remember sometimes if you open the shutter immediately after the goto that there could be some "settling" or backlash that would throw off the first sub. But once the backlash was taken up, the remaining subs worked fine.


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#8 michael8554

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Posted 22 October 2021 - 10:47 AM

I've seen the AVX worm period quoted as 594 secs, say 10 minutes.

 

After PA and then Star Alignment, centre on a bright star near south and the meridian.

 

Check horizontal (RA) centring every minute or so.

 

If it's not tracking the star will be gone very quickly.

 

RA Periodic Error will cause the star to drift a little left and right of centre over the 10 minutes, but not out of view.



#9 aa6ww

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Posted 22 October 2021 - 11:17 AM

You gotta do the polar alignment and leveling before you even turn on the scope.

Tracking should be dead on if your polar alignment is correct and you are leveled.

 

..Ralph



#10 verityfalls

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Posted 22 October 2021 - 11:48 AM

It should be tracking then.

 

One thing I note: You'll want to polar align first, then align for go to. If you polar align second, that will throw off the goto alignment. But it should cause the RA motor not to track. 

 

I can't imagine it's firmware, either. If the RA motor is on and the scope polar aligned, it should track. Regardless of anything else.

 

However, there is one other thing to to check before taking action: Is this only one sub or did you do many and they're all streaked? I remember sometimes if you open the shutter immediately after the goto that there could be some "settling" or backlash that would throw off the first sub. But once the backlash was taken up, the remaining subs worked fine.

 

You gotta do the polar alignment and leveling before you even turn on the scope.

Tracking should be dead on if your polar alignment is correct and you are leveled.

 

..Ralph

Thank you both for your replies! I did the physical polar aligning (moving the physical setup in Alt/Az) before doing the go-to alignment, then did the handpad polar alignment following the go-to alignment (as the manual recommends).

 

I took 5 exposures, all of which had the streaking. Very odd. I'll try it all again on the next clear night and see what happens, because you're both right, it should just start tracking.


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#11 bunyon

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Posted 22 October 2021 - 11:59 AM

In that case....I got nuthin. Did the five seconds exposures back to back all end up in the same place? That is, over 30 seconds, how far across the FOV did a star move?

 

Probably worth watching the live view (or using an eyepiece). 



#12 verityfalls

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Posted 22 October 2021 - 12:13 PM

In that case....I got nuthin. Did the five seconds exposures back to back all end up in the same place? That is, over 30 seconds, how far across the FOV did a star move?

 

Probably worth watching the live view (or using an eyepiece). 

Using the eyepiece makes it seem like the mount isn't tracking. At this point I'm hoping for user error somewhere in the process; I'll be especially careful to go step-by-step by the book in my next observing session and hope that solves it. The images I took also show that it seems to be a tracking issue; here they are in gif form.

 

Definitely a tracking issue. Fingers crossed that it's a solvable one!

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  • 10-18-Star-Streaking.gif


#13 cneal

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Posted 22 October 2021 - 12:20 PM

What tracking mode are is the mount set for? 

 

Menu->Tracking->Rate  Options are Sidereal, Solar, or Lunar.



#14 bunyon

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Posted 22 October 2021 - 02:02 PM

Yeah, your mount isn't tracking. I thought of cneal's idea, that the rate is wrong, but you wouldn't see that much difference in movement from the three rates in 30s. 

 

I don't know why, but your motor isn't running. 



#15 Old Man

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Posted 22 October 2021 - 05:01 PM

You also need to set the "TRACKING MODE", either EQ NORTH or EQ SOUTH, which ever applies. If you don't the mount still will not know what to do.



#16 Marino

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Posted 24 October 2021 - 09:48 AM

Aren't you supposed to redo the standard two star - calibration star alignment after doing an All Star Polar Alignment?

I'm visual only and have only done the ASPA once to see how it works so I may be wrong.



#17 DirtyRod

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Posted 24 October 2021 - 10:06 AM

Aren't you supposed to redo the standard two star - calibration star alignment after doing an All Star Polar Alignment?

I'm visual only and have only done the ASPA once to see how it works so I may be wrong.

That is correct. After the All Star Polar Alignment you have to re-align. 



#18 bunyon

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Posted 24 October 2021 - 08:00 PM

But the mount doesn’t need go to alignment or a very accurate polar alignment to track better than the OP has shown. Unless he aimed the polar axis southwest, he should be getting better results than his gif shows.

#19 verityfalls

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Posted 25 October 2021 - 10:01 AM

But the mount doesn’t need go to alignment or a very accurate polar alignment to track better than the OP has shown. Unless he aimed the polar axis southwest, he should be getting better results than his gif shows.

She, and I did indeed aim north! This is also what all of my research has shown; I'll just have to try it out again once the clouds clear and see if the problem clears itself up with a factory reset.



#20 bunyon

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Posted 25 October 2021 - 10:12 AM

She, and I did indeed aim north! This is also what all of my research has shown; I'll just have to try it out again once the clouds clear and see if the problem clears itself up with a factory reset.

She! My sincere apologies for the assumption. 

 

I know you aimed north. You described the situation well and it sounds like you did everything right. I just wanted to be sure the discussion of order of operation (important for most accurate go-tos) didn't take away from the most fundamental issue: the AVX motor isn't on or isn't engaged. Simply setting the AVX down pointed roughly north should keep an object on the sensor for many minutes if tracking is on.



#21 verityfalls

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Posted 25 October 2021 - 11:13 AM

She! My sincere apologies for the assumption. 

 

I know you aimed north. You described the situation well and it sounds like you did everything right. I just wanted to be sure the discussion of order of operation (important for most accurate go-tos) didn't take away from the most fundamental issue: the AVX motor isn't on or isn't engaged. Simply setting the AVX down pointed roughly north should keep an object on the sensor for many minutes if tracking is on.

No worries at all! That makes perfect sense. I'll update y'all once I get a chance to test it after reset.


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#22 verityfalls

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Posted 04 November 2021 - 01:29 PM

She! My sincere apologies for the assumption. 

 

I know you aimed north. You described the situation well and it sounds like you did everything right. I just wanted to be sure the discussion of order of operation (important for most accurate go-tos) didn't take away from the most fundamental issue: the AVX motor isn't on or isn't engaged. Simply setting the AVX down pointed roughly north should keep an object on the sensor for many minutes if tracking is on.

 

Great news! A reset seems to have done the trick: took me a couple of tries to get the polar aligning right, but we are in business and clearly tracking!

 

gallery_382008_18032_441305.jpg


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#23 bunyon

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Posted 04 November 2021 - 01:47 PM

Congrats! Glad it worked out.



#24 michael8554

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Posted 05 November 2021 - 04:44 AM

Your image is suffering from Coma,.

 

Usually this is only seen in the corners, but your image has Coma in the centre too.

 

I believe this means that Collimation needs adjusting.



#25 verityfalls

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Posted 05 November 2021 - 07:59 AM

Your image is suffering from Coma,.

 

Usually this is only seen in the corners, but your image has Coma in the centre too.

 

I believe this means that Collimation needs adjusting.

You're aboslutely correct--I will adjust the collimation next time I'm at the scope. Thanks!




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