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Equipment Discussions >> Mounts

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freestar8n
Post Laureate
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Reged: 10/12/07

Re: weird issue... new [Re: rmollise]
      #6320426 - 01/18/14 12:39 PM

Quote:

A few minutes considering the geometry of the situations shows you are clearly wrong.




Rod -

It is very obvious that some consideration of the geometry points to level not mattering to polar alignment.

It is *not* obvious that All Star Polar Alignment *cannot be done* without assuming the mount is level - and that level matters - but it is true.

This is what the long thread was all about - and I believe most people were eventually led to realize that level does matter.

The point isn't that "level matters to polar alignment." The point is that "level matters to the all star polar alignment procedure."

The fly in the ointment of the geometry is the inherent transformation from the polar axis error in sky coordinates, to the alt-az motions of the mount. The fact that this requires having the mount be level, or in some known orientation, is not obvious - but it is completely true.

ASPA has to assume the mount is level or there will be error in the final alignment. For small amounts off level it will be a small error - but for large errors in pier tilt or time or lat/long - the error can be huge.

So people should definitely have the mount pretty well level when they use ASPA. They don't have to go nuts about it - but decently level and decently accurate lat/long/time are all important.

If they *don't* use ASPA and they use a polar scope or something - they can have the whole thing in some crazy tilted state and it will work fine - but that isn't ASPA.

Frank


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rmollise
Postmaster
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Reged: 07/06/07

Re: weird issue... new [Re: freestar8n]
      #6320876 - 01/18/14 04:52 PM

Quote:



It is very obvious that some consideration of the geometry points to level not mattering to polar alignment.

It is *not* obvious that All Star Polar Alignment *cannot be done* without assuming the mount is level - and that level matters - but it is true.




But that's not obviously the opinion of Celestron given the reply from one of their people posted here. Further, I've, as I said, frequently completed AllStar very satisfactorily without worrying about leveling. Was my mount off level by 20 degrees? No, I can't say that, but I can say I didn't lay hands on a bubble level.


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wargrafix
sage


Reged: 04/10/13

Loc: Trinidad
Re: weird issue... new [Re: freestar8n]
      #6320880 - 01/18/14 04:55 PM

Hmmm....I am by the inlaws so in need to wait until I arrive home. Question: if I use only east stars to align, would this throw off things..my2 stars are rigel and sirius. Calib is canupus pollux and castor and betelguze

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guyroch
Vendor (BackyardEOS)
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Reged: 01/22/08

Loc: Under the clouds!
Re: weird issue... new [Re: wargrafix]
      #6320894 - 01/18/14 05:03 PM

Quote:

Hmmm....I am by the inlaws so in need to wait until I arrive home.




I'm sure your inlaws (and spouse) will understand and support your decision to leave now and attend to the important things



Guylain


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Peter in Reno
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Reged: 07/15/08

Loc: Reno, NV
Re: weird issue... new [Re: rmollise]
      #6320903 - 01/18/14 05:09 PM

You probably missed this part of Celestron's response:

Quote:

The further away from level that you get, the worse your polar alignment will get.




'nuff said.

Peter


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rmollise
Postmaster
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Reged: 07/06/07

Re: weird issue... new [Re: Peter in Reno]
      #6320905 - 01/18/14 05:12 PM

Quote:

You probably missed this part of Celestron's response:

Quote:

The further away from level that you get, the worse your polar alignment will get.




'nuff said.

Peter




But he referred to "level" in terms of the tripod being off balance. 'Nuff said. Excelsior.


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rmollise
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Reged: 07/06/07

Re: weird issue... new [Re: wargrafix]
      #6320907 - 01/18/14 05:13 PM

Quote:

Hmmm....I am by the inlaws so in need to wait until I arrive home. Question: if I use only east stars to align, would this throw off things..my2 stars are rigel and sirius. Calib is canupus pollux and castor and betelguze




If you leave off your calibration stars, your go-tos will not be as good, at least in areas far from the two alignment stars.


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freestar8n
Post Laureate
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Reged: 10/12/07

Re: weird issue... new [Re: rmollise]
      #6320954 - 01/18/14 05:33 PM

Quote:

But that's not obviously the opinion of Celestron given the reply from one of their people posted here.




Your original comment alluded to the geometry of the situation, and the long thread describes the fundamental geometry and mathematics of the process. It has nothing to do with the way it was implemented. It has to do with the fact that the adjustments are made in alt/az, and those axes have a specific orientation. I would be happy to explain it at any level if you are interested, but if you look at my figures at the beginning of the long thread - with an open mind - it might make sense.

If you are interested in the details of these things and how they work, then I encourage you to take a look. You cannot pre-move the mount in equatorial movements so that a user's subsequent alt-az motions will do the right thing - unless you know how those alt/az axes are oriented to the sky. To me - this should be obvious from the geometry of the transformations involved.

Frank


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jimbo728
super member


Reged: 11/05/13

Loc: Central NH
Re: weird issue... new [Re: guyroch]
      #6320967 - 01/18/14 05:40 PM

The CG 5 has a bubble level built in. Leveling provides consistency in your set up. If you are going to do AP, consistency in set up and balance will improve pointing accuracy.
If you must set up on a slope you really should adjust the tripod legs to level just to avoid a tip over.
No matter who is technically right on this one, it doesn't hurt to level the mount.
Good luck!
Jim


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wargrafix
sage


Reged: 04/10/13

Loc: Trinidad
Re: weird issue... new [Re: jimbo728]
      #6321068 - 01/18/14 06:39 PM

Lol. If I was staying over, the mount would be out right now. But I have heard the bubble is not correct on the cg5. I will give it a try when I arrive home. So many possible outcomes. I hope to get the right one.

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dragonslayer1
scholastic sledgehammer


Reged: 02/25/12

Loc: SLC, UT
Re: weird issue... new [Re: jimbo728]
      #6321077 - 01/18/14 06:45 PM

Yes, you first try and get it aligned to polaris by sight when you set up your mount. Then do your 2+4 (2star align/ 4 star calibration) then go to a star on southern horizion, approx 60* and towards the west.
Select Polar Align/mount align; It will select the star you were just on and you center and align it and the mount will sync to it. Then when you accept you want polar align, the mount will move to where the star should be,,, Then you adjust the mount RA/DEC adj knobs to try and get it centered as best as possible.. Then when done exit polar align and unsync the star that was used. Then redo 4 calibration points and if go-to are not good enough, then power down and redo 2+4, Kasey


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wargrafix
sage


Reged: 04/10/13

Loc: Trinidad
Re: weird issue... new [Re: dragonslayer1]
      #6321136 - 01/18/14 07:26 PM

I wish I can see polaris from where I setup but not so luck. Its compass and guesswork.

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dragonslayer1
scholastic sledgehammer


Reged: 02/25/12

Loc: SLC, UT
Re: weird issue... new [Re: wargrafix]
      #6321246 - 01/18/14 08:58 PM

Acompass is fine, Kasey

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rmollise
Postmaster
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Reged: 07/06/07

Re: weird issue... new [Re: freestar8n]
      #6321257 - 01/18/14 09:07 PM

Quote:




If you are interested in the details of these things and how they work, then I encourage you to take a look. You cannot pre-move the mount in equatorial movements so that a user's subsequent alt-az motions will do the right thing - unless you know how those alt/az axes are oriented to the sky. To me - this should be obvious from the geometry of the transformations involved.

Frank




Thanks. But my observations are:

1. Level does not effect the go-to alignment.
2. Neither does is affect AllStar in any observable fashion.

Knowing that I do not need to have the mount precisely level is good enough for me.

Edited by rmollise (01/18/14 09:08 PM)


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guyroch
Vendor (BackyardEOS)
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Reged: 01/22/08

Loc: Under the clouds!
Re: weird issue... new [Re: rmollise]
      #6321403 - 01/18/14 10:54 PM

Quote:

Quote:




If you are interested in the details of these things and how they work, then I encourage you to take a look. You cannot pre-move the mount in equatorial movements so that a user's subsequent alt-az motions will do the right thing - unless you know how those alt/az axes are oriented to the sky. To me - this should be obvious from the geometry of the transformations involved.

Frank




Thanks. But my observations are:

1. Level does not effect the go-to alignment.
2. Neither does is affect AllStar in any observable fashion.

Knowing that I do not need to have the mount precisely level is good enough for me.




Actually Rod your observations in this thread alone led you to make 2 strong statements against me. It is obvious (to me at least) that your observations are just that, your observations... yet you claimed geometry as a mean to defend your observed -practical- experience.

You are certainly entitled to defend your -practical- experience at face value (as should anybody), after all it is real experience you accumulated over the years. However, you should refrain (as should anybody) from making derogatory comments towards another member claiming anything but your observed experience. It is becoming very clear to me that you claimed geometry without having thought this through very well (note that I have used your wording).

You can read whatever you want into my comments, but know that I do not mean any disrespect. I truly mean that.

Like I said earlier, I have no dog in this fight.

Levelling your mount is, simply put, common sense. Case closed.

Guylain


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guyroch
Vendor (BackyardEOS)
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Reged: 01/22/08

Loc: Under the clouds!
Re: weird issue... new [Re: guyroch]
      #6321409 - 01/18/14 11:01 PM

I suggest we leave all that behind us and bring the conversation back to the original intention of the OP.

He seems truly motivated in learning polar alignment and astronomy as a whole.

WE SHOULD BE EMBRACING THAT!

Regards,

Guylain


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freestar8n
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Reged: 10/12/07

Re: weird issue... new [Re: guyroch]
      #6321443 - 01/18/14 11:26 PM

I think that the main thing for the OP to do is use more calibration stars for better goto accuracy and polar alignment. Using 3 calibration stars instead of 1 should improve things greatly.

Level, time, and lat/long do affect the all star polar alignment accuracy, but this sounds like a GoTo accuracy issue - and that shouldn't be affected by level, but it can be affected by using only one calibration star.

Frank


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rmollise
Postmaster
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Reged: 07/06/07

Re: weird issue... new [Re: guyroch]
      #6321872 - 01/19/14 10:01 AM

Quote:



Actually Rod your observations in this thread alone led you to make 2 strong statements against me. It is obvious (to me at least) that your observations are just that, your observations... yet you claimed geometry as a mean to defend your observed -practical- experience.






Nope. Read my posts more carefully. I said that level has no effect on being able to polar align an equatorial mount. And it doesn't.

As for the AllStar alignment procedure, my observation is that _in my experience_ level, precise level anyway, anything beyond eyeballing has absolutely no effect on the procedure. I haven't made a study of this. But I can say that being somewhat off level doesn't do a thing to the accuracy of this polar alignment method OR to go-to accuracy.

I didn't make derogatory comments about anyone. Again, see if you can read my posts a little more carefully.

Edited by rmollise (01/19/14 10:13 AM)


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wargrafix
sage


Reged: 04/10/13

Loc: Trinidad
Re: weird issue... new [Re: rmollise]
      #6321987 - 01/19/14 11:14 AM

Wow. I didn't mean to start anything negative here. Everyone here has been super helpful . There are a few issues I am trying to work around but I sincerely appreciate everyone's input. Lets try this another way. Please bear with me:

Last night was clear and then before coming outside. ...rain. :-(
I don't trust the bubble level on my mount. Before attaching mount to the tripod I made sure all 3 axis were dead level. Popped the mount and showed not level. I put my bubble level and it said level. Now this was on a level ground.
Obverving area is where the slight incline is and I will try the levelling for the sake of completeness. The issue which bugs me is the results are off north south and not east west where the incline exist.

I need to ask after leveling how much off the first alignment star is normally off? Also I have a very very stupid question. The dec cable has one end saying to dec motor, does it go to the dec area where the ota is or where the other cables are attached to.

A long read I know but I want you all to know that I am not only grateful but also more motivated than before. :-)


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dragonslayer1
scholastic sledgehammer


Reged: 02/25/12

Loc: SLC, UT
Re: weird issue... new [Re: wargrafix]
      #6322030 - 01/19/14 11:50 AM

Its like Rod said, eye balling it is close enough for level to find your problem. The first alignment star can be off a lot. When you get set-up, reset your settiungs to factory settings. thats in menu in handset. Then enter location timwe date time zone etc then start your 2+4 alignment, then polar align, Kasey

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