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Does Cuiv's Video on Leveling apply to Star Trackers?

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#1 Son of Norway

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Posted 17 January 2025 - 02:20 PM

OK, so Cuiv did a video on leveling your mount.  It demonstrates the same advice that I have seen often.  A perfect leveling of an equatorial mount is not critical, PHD2 will keep you on track.  But his demonstration was with an EQ mount that has motors to make corrections in both RA and DEC.  I don't see how this can apply to a star tracker like the SkyGuider Pro that can make corrections only in RA. 

 

I usually use my SGP with a 400mm APO lens.  In my experience it requires near perfect balance, polar alignment and leveling to get good guiding of the RA axis with PHD2 and good tracking with the DEC axis.  I work very hard on each one.  If the mount is not level it has no way to correct the movement of  the DEC axis and you will get poor results.  So I don't think that the standard wisdom on leveling applies to star trackers, but the members here have vastly more collective experience and wisdom than I do so I am asking the question: 

 

Does Cuiv's video apply to star trackers?



#2 idclimber

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Posted 17 January 2025 - 02:29 PM

Even with a tracker mount you need to physically align the RA axis to the celestial pole. The only difference is your Dec is not motorized 

 

The main reason I spend an extra minute leveling the tripod is to make elevation adjustments simpler and a bit quicker. 


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#3 dcbrown73

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Posted 17 January 2025 - 02:30 PM

I saw that video and it makes me laugh that someone would even try that beyond being a joke or just to see if said mount can correct for something so off level.  Not actually try to image in that condition.  (you're just asking be wasting your time for that imaging session)

 

As for you question, that's a blanket question.   I suspect it depends on the specific mount and it's capabilities of coping with being that unlevel.

 

I have an old Orion Sky Tracker, but it's been so long since I used that, that I don't even recall how to align it.   If it doesn't have computer aided alignment process, then it likely won't track.



#4 dcbrown73

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Posted 17 January 2025 - 02:31 PM

Even with a tracker mount you need to physically align the RA axis to the celestial pole. The only difference is your Dec is not motorized 

 

The main reason I spend an extra minute leveling the tripod is to make elevation adjustments simpler and a bit quicker. 

Exactly.  If my mount is level, then 41 degrees mark is very close to 41 degrees making tracking easier.



#5 Zambiadarkskies

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Posted 17 January 2025 - 02:35 PM

I saw that video and it makes me laugh that someone would even try that beyond being a joke or just to see if said mount can correct for something so off level. Not actually try to image in that condition. (you're just asking be wasting your time for that imaging session)

As for you question, that's a blanket question. I suspect it depends on the specific mount and it's capabilities of coping with being that unlevel.

I have an old Orion Sky Tracker, but it's been so long since I used that, that I don't even recall how to align it. If it doesn't have computer aided alignment process, then it likely won't track.


After the pain of umpteen threads about whether leveling is critical I can fully understand why he did it 🤣. And it's great that he did.
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#6 Poynting

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Posted 17 January 2025 - 02:46 PM

Hello,

 

For star trackers, using the polar scope to polar align in a repeatable way benefits from levelling. If you level the mount first, and determine what position in RA the mount need to be in for the reticle to be calibrated with the horizon (9-to-3) or with a plumb object (12-to-6 with a radio tower for instance), and mark this position so it is repeatable at a later time, then at that later time you just level the mount, move RA to that noted position, and put Polaris in the right spot and you are good. DEC drift will be minimized. 

 

If you polar align with another method such as drift alignment or plate solving methods, those methods don't require levelling to get the mount in the polar aligned position to minimize DEC drift. That is to say that polar alignment of the mount does not require levelling, but the method you use to get there may benefit from it.


Edited by Poynting, 17 January 2025 - 03:11 PM.


#7 dcbrown73

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Posted 17 January 2025 - 02:51 PM

After the pain of umpteen threads about whether leveling is critical I can fully understand why he did it . And it's great that he did.

The interesting thing is.  A Equatorial mount is supposed to naturally follow the sky when properly level and aligned.  I can easily get decent results unguided with my EQ6-R Pro at 60 second exposures   Auto-guiders make small corrections to it's movements to perfect any imperfections in it's natural tracking capabilities.

 

Intentionally making or leaving your mount unlevel /  not properly aligned, just makes the computer / guiding work that much harder and the mounts natural ability to follow the sky is rendered moot.

 

I liken it to the strain wave mounts with and without counter weights.  Can it track without a counter weight?  Yes.  Does the mount / computer work much harder to track that way?  Yes, it does.  I think Cuiv even proved that in battery drain when he did a video testing with and without the counter weight on the strain wave recently.  (he said it used 25% more battery to track without the counter weight vs with a counter weight)


Edited by dcbrown73, 17 January 2025 - 02:53 PM.

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#8 Andros246

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Posted 17 January 2025 - 03:08 PM

The interesting thing is. A Equatorial mount is supposed to naturally follow the sky when aligned.

Let me fix that for you.

And to the OP

Your star tracker is an EQ mount identical to our fancier EQ mounts in the basic principles on how a EQ mount works.

Edited by Andros246, 17 January 2025 - 03:16 PM.


#9 dcbrown73

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Posted 17 January 2025 - 03:37 PM

Let me fix that for you.

 

No, that's not what I mean.  When EQ mounts were originally designed, they were designed with the expectation that it would be properly leveled and polar aligned prior to operation. I don't mean "computer alignment algorithms" when I say that, I mean visually polar aligned.  The later addition of computers allowed less accurate leveling and moved the effort from the mount's natural tracking to computer aided tracking.

 

If it weren't for the sheer weight of the scope / cameras, etc.  You probably wouldn't even need an EQ mount at all; you could just use some sort of gimbal to track the sky just like smaller cameras on gimbals are used to track terrestrial objects on drones and other things.


Edited by dcbrown73, 17 January 2025 - 03:38 PM.


#10 PIEJr

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Posted 17 January 2025 - 03:41 PM

Let's start off with a link. https://youtu.be/6lW...eN3eElnNadVM6Pt

 

And to be thorough, here is more. https://youtu.be/cKV...7wjKRGamlkbbuQo

 

I found it interesting, although the tilting exaggerated. I got a kick out of it when he loosened his RA, and the telescope swung to its balance point.

 

Bottom line is I've worked around enough heavy industries to understand level and plumb, and why it is important.

 

Most of the argument that it doesn't matter makes me glad those folks don't build skyscrapers.

 

What I do works for me. Everybody do what works for you, too.

 

Clear Skies!


Edited by PIEJr, 17 January 2025 - 03:45 PM.

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#11 900SL

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Posted 17 January 2025 - 04:17 PM

The only thing that matters is whether the RA axis of your mount or tracker is accurately aligned to the NCP or SCP.

Levelling is good to do, because it helps when making alt az adjustments, but not necessary
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#12 Andros246

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Posted 17 January 2025 - 04:35 PM

 

Bottom line is I've worked around enough heavy industries to understand level and plumb, and why it is important.

 

I think we figured that out when playing with building blocks in preschool.

 

funnypost.gif



#13 DrGoon

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Posted 17 January 2025 - 05:01 PM

Intentionally making or leaving your mount unlevel /  not properly aligned, just makes the computer / guiding work that much harder and the mounts natural ability to follow the sky is rendered moot.

Yes - as astrometry and guiding gets better, so we can better correct for sub-optimal positioning. The problem would seem to me that the corrective movements are amplified and so it increases the light bleed into adjacent photosites. If you can get close to true and need no guidance, the images should need less sharpening, and can offer more tonal resolution. Hence I'd rather have an AP mount to a ZWO if I had the means. smile.gif


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#14 idclimber

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Posted 17 January 2025 - 05:59 PM

No, that's not what I mean.  When EQ mounts were originally designed, they were designed with the expectation that it would be properly leveled and polar aligned prior to operation. I don't mean "computer alignment algorithms" when I say that, I mean visually polar aligned.  The later addition of computers allowed less accurate leveling and moved the effort from the mount's natural tracking to computer aided tracking.

 

If it weren't for the sheer weight of the scope / cameras, etc.  You probably wouldn't even need an EQ mount at all; you could just use some sort of gimbal to track the sky just like smaller cameras on gimbals are used to track terrestrial objects on drones and other things.

The RA axis of any equatorial mount has only one place it can point. This is completely independent of the tripod. You could literally bolt an EQ mount to the side of a post and assuming there is enough adjustment get that axis pointed at the celestial pole. 

 

Level on the tripod only allows an arguably easier time setting the elevation and you have a bit less crosstalk on each axis. With modern programs using an offset on a star at it is pretty trivial to fix both. 

 

Even if the mount was a degree or two polar alignmet off the main impact on our images is field rotation, not Dec drift. Dec drift is quite slow especially when compared to the common periodic error in mounts like the AM5. 



#15 w7ay

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Posted 17 January 2025 - 06:43 PM

A perfect leveling of an equatorial mount is not critical, PHD2 will keep you on track.  

Not leveling a mount allows you to point the RA axis perfectly at the NCP (or SCP).

 

Next clear night, go out to find Polaris by rotating your head (azimuth) and tilting your head up and down (altitude).  You can always find Polaris by just these two motions.  The same is true with pointing the RA axis at the pole.

 

However, the above is missing an important ingredient... once you have sighted Polaris, tilt your head sidewards (Hour Angle).  You can keep Polaris centered, but the rest of the sky has rotated around it.  Tilting your head sideways is analogous to not leveling the base of an equatorial mount.

 

Basically, when your star reaches the prime Meridian (zero Hour angle), the mount does not think it is at zero Hour Angle; unless the mount has been modeled with star alignments.  

 

A computer controlled mount may fail to execute a meridian flip when the controlling software sends a GOTO, expecting the star has already traversed the mount's zero hour angle.  You see this all the time at the ASIAIR forum (where the ASIAIR would rinse and repeat the Meridian flip GOTO command every 1 minute, before the mount finally executes the flip when the mount thinks the star is now on the other side of the meridian).

 

Each degree that you are off east-west leveling means a difference of one minute of clock time difference between the mount and the computer.  A tripod whose legs are separated by 1 meter will sustain a 1 degree tilt (4 minutes of time) if one of the east or west legs is about 17.5mm shorter than the others.  

 

In short, if you don't want to waste time waiting for a Meridian flip, do yourself a favor and level your mount.

 

Chen


Edited by w7ay, 17 January 2025 - 06:49 PM.

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#16 Arcueid

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Posted 17 January 2025 - 08:25 PM

If you're only tracking a object that might be OK as long as you have properly polar aligned. But for goto and meridian flip that might introduce some problems.



#17 rj144

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Posted 17 January 2025 - 08:35 PM

No, that's not what I mean.  When EQ mounts were originally designed, they were designed with the expectation that it would be properly leveled and polar aligned prior to operation. I don't mean "computer alignment algorithms" when I say that, I mean visually polar aligned.  The later addition of computers allowed less accurate leveling and moved the effort from the mount's natural tracking to computer aided tracking.

 

If it weren't for the sheer weight of the scope / cameras, etc.  You probably wouldn't even need an EQ mount at all; you could just use some sort of gimbal to track the sky just like smaller cameras on gimbals are used to track terrestrial objects on drones and other things.

What is computer aided tracking?  Do you mean guiding?


Edited by rj144, 17 January 2025 - 08:35 PM.


#18 dcbrown73

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Posted 17 January 2025 - 09:41 PM

What is computer aided tracking?  Do you mean guiding?

That's only half of it.

  1. Computer alignment. (2/3 star alignment, all the different alignments offered by computer, etc)
  2. Image based star tracking / guiding.

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#19 idclimber

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Posted 17 January 2025 - 09:58 PM

What is computer aided tracking?  Do you mean guiding?

The funny thing is there is actually software in common use that does correct for changes and errors in polar alignment. This is precisely what sky modeling on premium mounts like the 10 Micron, Paramount or an Astro-Physics mounts do to get tracking errors so low you can image unguided. 

 

The other funny part is larger heavier loads like a 24" Planewave and above are commonly placed on Alt Az mounts not an equatorial mount. 


Edited by idclimber, 17 January 2025 - 09:59 PM.

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#20 rj144

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Posted 17 January 2025 - 11:47 PM

 

That's only half of it.

  1. Computer alignment. (2/3 star alignment, all the different alignments offered by computer, etc)
  2. Image based star tracking / guiding.

 

Thanks.  But I'm still a bit confused.  Using a computer to align is just an aid.  It just helps physically aligning.  The computer isn't aligning, right?

 

What is "image based" tracking?  There's tracking which uses an image as a reference?



#21 dcbrown73

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Posted 18 January 2025 - 10:25 AM

Thanks.  But I'm still a bit confused.  Using a computer to align is just an aid.  It just helps physically aligning.  The computer isn't aligning, right?

 

What is "image based" tracking?  There's tracking which uses an image as a reference?

When you do a computer alignment, you are telling the computer exactly where specific stars are and when you do that.  It knows where the encoders are when it's pointing at those stars.   This allows the computer to triangulate where it's actually pointing based on the encoders, so when it goes to start tracking, it has a very good idea of what direction to go.   This alone won't give you perfect tracking, but can allow a mount (like Cuiv) to unlevel the mount yet still track in the correct general direction.

 

To get great tracking, you also need Image based tracking (or guiding with a guide camera)  It watches the stars movements and if the star moves from where it should be in the image, the computer will send adjustments to the mount to move the mount to correct the star's location in the image.

 

H0ihq6.jpg



#22 Bob_Gardner

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Posted 18 January 2025 - 10:36 AM

In short, if you don't want to waste time waiting for a Meridian flip, do yourself a favor and level your mount.

Chen

I could be wrong but suspect that leveling errors have caused issues with my portable rig during meridian flips at a remote dark sky site.  I have an Askar 151phq on a GEM45 (which handles the load well and provides 0.5 to 1.0" rms tracking depending on seeing and other factors).  Using the iOptron pier extender and with the mount perfectly leveled, I have confirmed during daytime testing that the camera on the end of the OTA assembly always clears the legs of the mount during meridian flips (with the ASIAIR settings I'm using), regardless of the declination of the object being imaged.  However, while imaging at the dark sky site, I had a close call where I had to intervene to prevent the camera from hitting a tripod leg during a meridian flip.  I am not 100% sure what caused this, but suspect that leveling (being off by a few degrees) may have been a contributor.


Edited by Bob_Gardner, 19 January 2025 - 09:07 AM.


#23 DeepSky Di

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Posted 18 January 2025 - 11:37 AM

Polar aligning is getting the rotational axis of your mount  pointed at the pole. The mount does not need to be level to achieve this, and that's the point of the video. The misalignment is deliberately and wildly exaggerated to prove this point; and it's also stated that this is unsafe when slewing if the mount is so unbalanced that slewing causes it to tip over.



#24 The Rigger

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Posted 18 January 2025 - 11:45 AM

Granted I'm new to this hobby, but this just makes no sense to me.  If you have the capability, why would you not level? Seems pointless....

 

I guess I'll shut up 'n' keep reading.


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#25 kathyastro

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Posted 18 January 2025 - 12:09 PM

But his demonstration was with an EQ mount that has motors to make corrections in both RA and DEC.  I don't see how this can apply to a star tracker like the SkyGuider Pro that can make corrections only in RA.

The ability of an EQ mount to track accurately has nothing to do with motors making corrections.  It is totally dependent on the quality of the polar alignment, and nothing else.  If the RA axis is aligned with the pole, the tracking will be accurate.  This applies whether the tripod is levelled or not.

 

A tracker is simply a small, simple EQ mount.  The same reasoning applies: if you can point the RA axis at the pole, tracking will be accurate. 

 

Watch the video again, and try to understand why level is not important.

 

I still recommend that people level their mounts, because it makes polar alignment easier.  But it is not a requirement for accurate tracking.


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