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Meade LX-200 10" GPS Goto

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#26 OzAndrewJ

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Posted 13 November 2015 - 11:47 PM

Gday gatesjunior

 

The LX200GPSs are normally very accurate for AltAz gotos when aligned properly

If the encoders check out OK, but manual 2 star aligning still gives very bad results ( after using a good star pair ), then you may need to check the orthogonality of the OTA.

 

Andrew Johansen Melbourne Australia



#27 gatesjunior

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Posted 14 November 2015 - 12:03 AM

Gday gatesjunior

 

The LX200GPSs are normally very accurate for AltAz gotos when aligned properly

If the encoders check out OK, but manual 2 star aligning still gives very bad results ( after using a good star pair ), then you may need to check the orthogonality of the OTA.

 

Andrew Johansen Melbourne Australia

 

Do you have a good process for this ?



#28 OzAndrewJ

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Posted 14 November 2015 - 02:10 AM

Gday gatesjunior

 

I used a mirror in my shed, but i wouldnt say that was "easy".

Also, orthogonality testing is really a 2 stage process, but stage one is a lot harder without the right tools.

Ie stage one is to ensure the DEC axle is orthogonal to the RA axle ( normally a factory process )

Stage 2 is to ensure the OTA is orthogonal to the DEC axle

 

There are lots of methods posted on the net, but Up where you are, i reckon the easiest way to do a stage 2 check is to put the scope on a wedge and "mechanically" aim the wedge at Polaris, not the pole.

Then, you simply declutch the RA axis and spin the OTA ( preferably with a camera for ease of use ) and watch what happens.

ie if you start with the DEC axle horizontal, you adjust the azimuth of the wedge to roughly centre polaris,

then set the DEC axle vertical and use the alt adjustment to centre polaris.

Now you reset the axis to horizontal and note where Polaris is on the screen

Now manually rotate in RA by 180deg and again note where Polaris is

If Polaris effectively describes a circle as you rotate, then the OTA is parallel to the RA axle.

If not, you need to adjust accordingly.

There are 2 very small threaded holes in the back of each of the OTA saddles.

You need to get some screws that fit into those holes ( i dont have the sizes handy ).

These temporary screws effectively act like jacking bolts on the OTA locking bolts, to allow you to provide a fine adjustment of the OTA relative to the saddle.

As such, you release the tension of the three OTA locking bolts on one side of the OTA, and use the jacking bolts to tweak the position until the spin test results in Polaris doing donuts in the FOV of the camera ( or eyepiece )

 

Andrew Johansen Melbourne Australia



#29 gatesjunior

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Posted 14 November 2015 - 07:00 AM

Thank you sir.



#30 OzAndrewJ

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Posted 14 November 2015 - 05:09 PM

Gday gatesjunior

 

 

Just one other thing.

Getting to the three saddle bolts to release and snug them

when the OTA is at DEC=90 can be a real pain.

I replaced mine with fender washers and hex head screws to make it a bit simpler.

That said, the spin test can be done without needing to do any adjustments

if you just want to check the OTA alignment.

 

 

Andrew Johansen Melbourne Australia



#31 gatesjunior

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Posted 14 November 2015 - 07:46 PM

Gday gatesjunior

 

 

Just one other thing.

Getting to the three saddle bolts to release and snug them

when the OTA is at DEC=90 can be a real pain.

I replaced mine with fender washers and hex head screws to make it a bit simpler.

That said, the spin test can be done without needing to do any adjustments

if you just want to check the OTA alignment.

 

 

Andrew Johansen Melbourne Australia

 

Andrew,

 

  So, a friend of mine in our local club gave me some guidance and this is what I have done.  I put the ota at a 90 with the Correction plate at the top center of the forks.  I then put a level on top of the OTA.  I checked level on the tripod and telescope base first.  Then I spun the OTA around and watched to see if the level changed at all, which it did not.  I then moved the level around the OTA in different locations and checked level.  What I found is the DEC side needed to come down.  Maybe a 1/4 of an inch. or maybe an 1/8th  So I brought it into level this way with the level above each fork and then re-tested everything.

 

Then I took it outside and picked a landmark and trained the drives.  After which, I added this same insulator on top of a distant pole as my landmark as well.  Then I slewed off of it to the complete opposite side and then told it to goto the landmark.  It in fact did and the insulator was in the FOV of the 12mm cross-hair I used to set it with.  Now, it was not perfect but pretty close.  So I slewed away again and moved more drastic adding up and down motions into the mix as well and then told it to go back to the landmark.  It did and in fact was still pretty close and in the FOV of the 12mm.

 

Tonight is not really clear, so I have not been able to really test the Alignment yet and the goto on the heavens.


Edited by gatesjunior, 14 November 2015 - 08:03 PM.


#32 OzAndrewJ

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Posted 14 November 2015 - 08:11 PM

Gday gatesjunior

 

That method will possibly detect if there are any gross errors

but even most good digital levels are only accurate to 0.1deg ( ie 6 arcmins )

I am surprised you had an error of 1/4" based on the sequence you describe,

ie why did the level not move when on top of the OTA,

but show a big error when on the side of the OTA. I dont understand that.

However, if that were true, it would certainly explain bad gotos.

A spin test on Polaris will give an absolutely irrefutable result.

 

As to selecting a landmark, then slewing away and going back,

that wont really test much other than the encoders arent

behaving in an "erratic" manner.

 

Andrew Johansen Melbourne Australia



#33 gatesjunior

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Posted 14 November 2015 - 08:40 PM

Gday gatesjunior

 

That method will possibly detect if there are any gross errors

but even most good digital levels are only accurate to 0.1deg ( ie 6 arcmins )

I am surprised you had an error of 1/4" based on the sequence you describe,

ie why did the level not move when on top of the OTA,

but show a big error when on the side of the OTA. I dont understand that.

However, if that were true, it would certainly explain bad gotos.

A spin test on Polaris will give an absolutely irrefutable result.

 

As to selecting a landmark, then slewing away and going back,

that wont really test much other than the encoders arent

behaving in an "erratic" manner.

 

Andrew Johansen Melbourne Australia

 

Yes, I did want to test the encoders and you are correct, that is why I did that.  I do not have a wedge, and I am in Alt/Az mode, so I am not sure how I would test what you described without one.  The scope and the forks both spin, so to me that test of spinning was only testing really the tripod levelness.  When I moved the level around on the OTA is when I noticed it being off above the forks.



#34 gatesjunior

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Posted 14 November 2015 - 08:47 PM

Is it possible at all my hand controller is bad ?  I know that sounds like an off the wall question, but I have noticed it seems as it gets a little colder out that it sometimes just does not act right.  Let me explain.  I tried tonight, briefly to do an alignment just a few minutes ago.  There was a slight clearing.  Now, this is where is gets strange.  I aligned the first star, Vega, then it took me over to Mirphak.  Now, it was hit and miss, so I am not absolutely sure that was the star I was on, but I think so.  I had done a calibration of sensors on Polaris just before, so I thought well, let me tell it to go back to Polaris, this is where it gets strange.  The hand controller said slewing, but I did not hear or see the telescope moving ???

 

Does any of this sound crazy or what ?  It just kind of stayed where it was at.  Wait, never mind, I remember changing the GPS Offset from +13 to 0 I think without resetting the power to the scope..  Doh !!


Edited by gatesjunior, 14 November 2015 - 08:51 PM.


#35 OzAndrewJ

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Posted 14 November 2015 - 08:52 PM

Gday gatesjunior

 

The scope and the forks both spin, so to me that test of spinning was only testing really the tripod levelness.

Ahh OK. I normally do that process by using my digital level on the top of the fork hub, not the OTA.

Just set the level on the hub and zero it, then spin the forks

When the level doesnt change during 360deg, i know the RA axle is vertical within 6 arcmins.

 

Andrew Johansen Melbourne Australia



#36 gatesjunior

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Posted 14 November 2015 - 08:57 PM

I really think what I need to do is this, you tell me, I might be getting ahead of myself.

 

Go outside and level tripod with a level.

Grab the OTA and mount it on the tripod.

Face the OTA's Correction Plate North and the panel South

Set the OTA to 0 degrees

Turn on the scope and let it initialize

Go into mode and then setup and telescope and run the sensor calibration

Then do the Automatic alignment and let it find tilt, level, north, etc and do the two star alignment

Then test the Goto function

 

Does all that sound right or am I missing something or a step

 

Hey, also, the battery in the unit itself on the board might be dead, I do not know.  It does lock onto GPS fairly quickly and does link it to my site I added for my home.



#37 OzAndrewJ

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Posted 14 November 2015 - 08:59 PM

Gday gatesjunior

 

The GPS offset wont cause what you describe.

The normal cause of what you mention is not hitting enter to select the target before hitting goto.

The software isnt real bright, in that if you hit "goto" when you are on the current target, it will actually do a full goto again, thus tricking you into thinking it is doing something :-) It is really just spinning its wheels.

Just ensure when you scroll to Polaris ( or any other target ), you hit enter first.

It should flash that it is calculating the new coords and then the word Polaris will appear on line 1 of the hbx to indicate it has been selected.

At that point, hitting goto should work.

 

Andrew Johansen Melbourne Australia



#38 gatesjunior

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Posted 14 November 2015 - 09:00 PM

Hey, I just thought of something.  I have a laptop and Stellarium, is there a way I can test the scope with that and hook my cable to the RS/232 port ?  I mean, if I trust Stellarium just as a test run as far as position of the stars and do the alignment with centering the star with Stellarium on each one then could I not just tell Stellarium to go to an object and see how the scope behaves, or is this just not going to work that way ??



#39 gatesjunior

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Posted 14 November 2015 - 09:03 PM

Gday gatesjunior

 

The GPS offset wont cause what you describe.

The normal cause of what you mention is not hitting enter to select the target before hitting goto.

The software isnt real bright, in that if you hit "goto" when you are on the current target, it will actually do a full goto again, thus tricking you into thinking it is doing something :-) It is really just spinning its wheels.

Just ensure when you scroll to Polaris ( or any other target ), you hit enter first.

It should flash that it is calculating the new coords and then the word Polaris will appear on line 1 of the hbx to indicate it has been selected.

At that point, hitting goto should work.

 

Andrew Johansen Melbourne Australia

 

You are kidding me, OMG, I think I in the tour I just use the arrow keys and then hit Goto and it goes.  You know what, let me ask you a really stupid question.  The tours I have on this scope are the old ones !!!  From like 1.2b or back in 2003 or whatever, because Meades site was and I think still is displaying the 404 error on things.  So I had a guy send me his rom file and I upgraded it that way.  Now most of the other data downloaded fine, but did I mix and mash things by the way I flashed this thing ??

 

For the record, all the testing I had been doing was hitting Goto from the tour screen.


Edited by gatesjunior, 14 November 2015 - 09:04 PM.


#40 OzAndrewJ

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Posted 14 November 2015 - 09:11 PM

Gday gatesjunior

 

 

Does all that sound right or am I missing something or a step

That sounds normal, but again, doing a manual 2 star is far faster and you have far greater control.

All the level dancing etc does is give the scope a rough idea on how to find the first star by dead reckoning.

After you hit enter on the first star, everything the dancing process did is ignored, and the aligning process becomes the standard 2 star.

 

ie Just do a manual 2 star and choose an easily identified star as your first star, and centre it accurately.

If everything is setup correctly, the second star should normally appear in the 26mm EP.

The auto method always picks the brightest star first, and the second star is the next brightest that fits within a large selection range, and this isnt always optimal for good aligning. Manual 2 star allows you to choose, so try to get 2 stars approx 90 deg apart in Azimuth and between say 40 to 60 deg in altitude if you can.

 

Andrew Johansen Melbourne Australia



#41 OzAndrewJ

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Posted 14 November 2015 - 09:17 PM

Gday gatesjunior

 

Now you have me confused :)

 

so I thought well, let me tell it to go back to Polaris

From that statement, i deduced that you were using the named stars menus to test different targets.

Tours are a totally different proposition, and im not sure how you could manually select Polaris in a tour???

 

 

 

I think I in the tour I just use the arrow keys and then hit Goto and it goes.

Yep, but pls dont use tours "for testing stuff", use the named stars menus, as you have total control.

 

Andrew Johansen Melbourne Australia



#42 gatesjunior

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Posted 14 November 2015 - 09:29 PM

Gday gatesjunior

 

Now you have me confused :)

 

so I thought well, let me tell it to go back to Polaris

From that statement, i deduced that you were using the named stars menus to test different targets.

Tours are a totally different proposition, and im not sure how you could manually select Polaris in a tour???

 

 

 

I think I in the tour I just use the arrow keys and then hit Goto and it goes.

Yep, but pls dont use tours "for testing stuff", use the named stars menus, as you have total control.

 

Andrew Johansen Melbourne Australia

 

Well, that is because after the two star alignment I did bounce back to manual, where in the past I had always used tour after the alignment just to have it take me around and show me a few things I have not looked at before.  And that makes sense, I did not hit enter, why, because I was always using Tour to check the alignment of objects.  So back to my question, could the tour data be old enough where the data is off or something ?  Or the older version of 1.2b's tour data is not quite the same format or data as the newer ?  Could that be messing my scope up, since I upgraded with a copied rom file ?



#43 OzAndrewJ

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Posted 14 November 2015 - 09:43 PM

Gday gatesjunior

 

 

So back to my question, could the tour data be old enough where the data is off or something ?

Depends on how the tour was written.

Normally, a tour will list a named star by name. If it is done that way, the scope will read the RA/DEC from its internal databases, precess and refract it and then do a goto, ie the coords should be correct.

If the tour has been written using manually entered RA/DEC coords, then data entry is treated as jnow() and any local errors could cause grief.

As per before, if you want to "test" the accuracy of the mount, forget using tours, only use named stars, as it greatly simplifies the process.

 

Andrew Johansen Melbourne Australia



#44 gatesjunior

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Posted 14 November 2015 - 10:26 PM

Gday gatesjunior

 

 

So back to my question, could the tour data be old enough where the data is off or something ?

Depends on how the tour was written.

Normally, a tour will list a named star by name. If it is done that way, the scope will read the RA/DEC from its internal databases, precess and refract it and then do a goto, ie the coords should be correct.

If the tour has been written using manually entered RA/DEC coords, then data entry is treated as jnow() and any local errors could cause grief.

As per before, if you want to "test" the accuracy of the mount, forget using tours, only use named stars, as it greatly simplifies the process.

 

Andrew Johansen Melbourne Australia

 

That is what I am going to do from now on.  Once I know that works, then I will look into the tours section.



#45 OzAndrewJ

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Posted 14 November 2015 - 10:57 PM

Gday gatesjunior

 

based on a rough location of Michigan, and an early evening align ( say 19:00 - 20:00 )

maybe try doing a 2 star align using Vega first ( as you cant miss it )

and Mirphak as the second star.

Ensure you centre them properly as well.

If you dont have a crosshair EP, just defocus the scope until the star looks like a large donut.

This makes it much easier to judge when its central in the EP.

Use the finder to confirm its the correct bright star.

 

Andrew Johansen Melbourne Australia



#46 gatesjunior

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Posted 14 November 2015 - 11:09 PM

Gday gatesjunior

 

based on a rough location of Michigan, and an early evening align ( say 19:00 - 20:00 )

maybe try doing a 2 star align using Vega first ( as you cant miss it )

and Mirphak as the second star.

Ensure you centre them properly as well.

If you dont have a crosshair EP, just defocus the scope until the star looks like a large donut.

This makes it much easier to judge when its central in the EP.

Use the finder to confirm its the correct bright star.

 

Andrew Johansen Melbourne Australia

 

Got it..  I will report back.  I can also hook up Stellarium to the scope and see where it is reporting the scope is stating where it is pointed.  I have already verified connectivity and communication with the scope and it does show the scope indicator.   So if you want me to do any testing with that, I can also bring my laptop out with me as well and connect her up.

 

This might be a good way to see what the scope is reporting and what I am seeing.  Because we could see on Stellarium where the scope is stating it is pointed at compared to what I am seeing.


Edited by gatesjunior, 14 November 2015 - 11:18 PM.


#47 OzAndrewJ

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Posted 14 November 2015 - 11:30 PM

Gday gatesjunior

 

hooking up to stellarium will be fun enough, but again, for testing, the KISS principle is in order.

( Also, until you have aligned, Stellarium will only be given "estimated data" from the scope,

so its not much help.)

I note in yr earlier post you mentioned using Vega, Almaak.

Depending on actual time of night, this gives an Az angle between stars that might

be a bit greater than the optimum 90deg than we want.

Using Mirphak reduces this angle by about 20 deg, so may end up getting a better tip/tilt calculation.

Try it and see. :-)   ( but keep it simple )

 

Andrew Johansen Melbourne Australia



#48 gatesjunior

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Posted 14 November 2015 - 11:36 PM

Gday gatesjunior

 

hooking up to stellarium will be fun enough, but again, for testing, the KISS principle is in order.

( Also, until you have aligned, Stellarium will only be given "estimated data" from the scope,

so its not much help.)

I note in yr earlier post you mentioned using Vega, Almaak.

Depending on actual time of night, this gives an Az angle between stars that might

be a bit greater than the optimum 90deg than we want.

Using Mirphak reduces this angle by about 20 deg, so may end up getting a better tip/tilt calculation.

Try it and see. :-)   ( but keep it simple )

 

Andrew Johansen Melbourne Australia

 

Got it..



#49 gatesjunior

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Posted 15 November 2015 - 07:55 PM

 

Gday gatesjunior

 

based on a rough location of Michigan, and an early evening align ( say 19:00 - 20:00 )

maybe try doing a 2 star align using Vega first ( as you cant miss it )

and Mirphak as the second star.

Ensure you centre them properly as well.

If you dont have a crosshair EP, just defocus the scope until the star looks like a large donut.

This makes it much easier to judge when its central in the EP.

Use the finder to confirm its the correct bright star.

 

Andrew Johansen Melbourne Australia

 

Got it..  I will report back.  I can also hook up Stellarium to the scope and see where it is reporting the scope is stating where it is pointed.  I have already verified connectivity and communication with the scope and it does show the scope indicator.   So if you want me to do any testing with that, I can also bring my laptop out with me as well and connect her up.

 

This might be a good way to see what the scope is reporting and what I am seeing.  Because we could see on Stellarium where the scope is stating it is pointed at compared to what I am seeing.

 

 

Well, I went outside and did the following:

 

Setup tripod and leveled it

Brought OTA out and mounted it on the tripod and pointed the Corrector lens North and the Controller South

Trained the drives during the day just before dark and then waited for dark, powered it off

Dark arrived and then I Turned it on and skipped align and did a calibrate sensors first

Then I did a manual two star alignment using the two stars you gave me, Vega and Mirphak

 

After this was all done I told it to go to the North Star, bang in the middle of the 26mm, now I used that initially to do the two star alignment as well, but then switched to my 12mm and brought it out of focus a little and centered it in the cross-hairs for each alignment star.

 

So, I thought o.k., lets go to the moon.  Bang, it was also in the FOV.  So then I got excited and started bouncing all over, Ring Nebila, M13, M32 and Andromeda Galaxy, Dumbell Nebula, and a few others, they were pretty much all in the 26mm FOV.  Maybe one or two off a little, but I would watch when it was slewing to it and normally could see it off the FOV a little.

 

So, what do you think ?  Is it being mostly in the FOV on a 26mm pretty good or do you think that is not acceptable ?   I did also try and hold enter on a couple after I centered them and then bounced around from there.  Even going back to objects a second time, a lot of them were then in center and some were a little off...

 

So, I am very happy..  Thank you, now just so you know, I did reload the right tours and all the objects again just to make sure I had it all right..


Edited by gatesjunior, 15 November 2015 - 08:01 PM.


#50 OzAndrewJ

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Posted 15 November 2015 - 08:40 PM

Gday gatesjunior

 

So, what do you think ?  Is it being mostly in the FOV on a 26mm pretty good

Considering you still really dont know how good the orthogonality is, the results are pretty good.

( I would be disappointed if M31 wasnt in the EP :lol: )

As to the moon and planets, they can be off a bit at any time due to the cut down calculations involved, esp the moon )

Also, the planets are found using j2000 coords via the hbx, so if you are happy its all working on stellar targets, it may pay to use Stellarium to select planets.

Other than that, another rough guide to the orthogonality is to do gotos between objects at very different altitudes, and gotos between objects at approx the same altitude.

If the gotos where little change in altitude is required are spot on, but gotos between objects with large differences in Altitude arent, then the orthogonality may require further tweaking at a later date.

However, if its all working well now, and you can find things, just enjoy it for a while.

 

Andrew Johansen Melbourne Australia




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