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EQ6 / Atlas GOTO's Cone Error 3 STar Alignment?

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#1 Gregk

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Posted 04 September 2008 - 06:49 PM

Hi,

Recently did a Hypertune on my EQ6. All is super re: guiding tracking
but I keep failing the 3 star alignment consitenly and somtimes the
controller my say "alignment may not be close enough"I also swithced
to having the aligment stars come up by magnitutde instead of
alphebetically, which was a great help...I think.

I was doing 3 minute guided subs last night with errors < .5. Imaging
scope 80Ed Gudied scope 66mm WO apo with DSI and PHD

I did check with the mount pointed to Polaris...I moved the RA side
to side and polaris was shifting in my ED80 scope considerably looking
thru
a 26mm eyepiece...so there is an issue somewhere mechaniacally. Not real
apparent...to find

Is there a problem with letting the SYNSCAN pick the stars?

Thanks for any suggestions help

Greg

#2 Zebra24601

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Posted 04 September 2008 - 11:39 PM

I've only tried the three star a few times because, so far, it has never worked for me!

How do you get the alignment stars to show by magnitude instead of alphabetically? I've got an older firmware version, so I may or may not have that option. But I'd be curious to see it.

#3 Gregk

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Posted 05 September 2008 - 12:22 AM

Hi,

I have version 3 of the controller..under alignment stars in the setup menu you can sort alphabetically or by intensity.

I found the front ring on the imaging scope to be very loose to teh dovetail lifting up and off a little and now things are good again.

Another suggestions i got on the yahoo site was to use the one star aligment near the object to image and that works well ...have not tried it

Thanks

Greg

#4 Skylook123

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Posted 05 September 2008 - 01:25 AM

For me, IF polar alignment is good, the mount is level, and Home position is established well, then one star works well, two stars sometimes good, sometimes not so good, and three stars hardly ever any good. The devil is in the precision in the eyepiece for the alignments. It demands reticle eyepiece or high power to get each alignment star centered repeatably in the FOV. If not, the more stars you use, the more warped space becomes. Tricky, at times!!

#5 WarrenS

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Posted 05 September 2008 - 08:27 AM

For what it's worth, I have the opposite experience. One star alignment seldom works, three star almost always dead on. When aligning, I defocus the stars until they're almost touching the edge of the field of view which makes it much easier to tell centering.

#6 Skylook123

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Posted 05 September 2008 - 10:47 AM

Warren's method really helps the precision of centering. My problem is that usually I align with my highest power regular use eyepiece, a 9mm Nagler, which has such a doggone large FOV it's still easy for me to screw it up even with a defocused star.

I've had great luck, though, with an old 8mm Plossl if I remember to take it out. It's like looking through a soda straw after the Nagler, and the precision goes way up.

One other note, if you use a low power/wide field eyepiece for finding the star, and switch to high power on the star for centering, don't change the focus on most SCTs between stars. The mirror shift will kill the effort.

#7 groz

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Posted 05 September 2008 - 10:54 AM

My experience with a stock EQ6-Pro, and the HEQ5-Pro is also just the opposite, with a small caveat. Dont always accept the alignment stars in the order the HC shows, make sure you choose stars with decent geometry. 2 stars on one side of the meridian, one at a low dec, the other substantially higher, then the third star on the other side of the meridian, declination more or less between the original two. I just watch to make sure the 3 stars form a large triangle, with none of them at/near the zenith.I do occaisionally get the 'alignment failed' if I take the 3 stars as it originally offers them, and one is at / near zenith.

I use the guider display to center stars during alignment. After the 3 star align, it's quite normal for slews and goto commands to land things within the fov of the guidescope.

#8 David Pavlich

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Posted 05 September 2008 - 02:04 PM

My experience was to use a 3 star every time. Also make sure that the stars are fairly far apart. I never let the mount pick the stars unless the stars happened to be on the list that I made. I used the software that came with the mount, Orion's The Sky, to pick my stars. The problem is that the mount doesn't know where all of the pine trees are. :grin:

At any rate, the 3 star was my best alignment routine.

David

#9 jonbosley

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Posted 05 September 2008 - 02:51 PM

I also use three star - The best results I found is to use three stars in the same part of the sky I am going to image/view in and I get dead center, when I use a much wider star setup I find, in some parts of the sky, objects are on the edge of view or even just outside. I have done drift alignment with the setup which helps. I know that an approx polar alignment can lead to poor goto. I believe in three star it creates a mathematical model based on a triangle set by the alignment stars. Outside the triangle the model is less accurate, inside, much better. The larger the triangle the less accurate it is.
I also get very good goto with two star alignment. I have not really tried one star.

I seem to have problems with the PAE (sync routine), for some reason it thinks Jupiter is Saturn and when trying a star it reads that star but when I tell it to go to the star after the PAE (its still on the star I am just testing to see if its set, it moves off the star!
I have to say I had the EQ5 with version one (when they first came out) and the goto was much worse then the newer version with the Atlas. I believe there is still room to improve the goto on the mounts especially when using wider reference stars. A better sync routine would help a lot. The EQMOD improves the mounts when using a PC by bypassing the handset so hopefully the handset computer will get improved in time.

Jon

#10 Gregk

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Posted 05 September 2008 - 04:16 PM

" I seem to have problems with the PAE (sync routine), for some reason it thinks Jupiter is Saturn and when trying a star it reads that star but when I tell it to go to the star after the PAE (its still on the star I am just testing to see if its set, it moves off the star! "

I have experienced that also. What it the correct procedure for PAE. Do you always have to clear the previous. I get the object centered and then do a PAE and it tells me It's centereing it...is that it or is there more to it.

Thanks

Greg

#11 Skylook123

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Posted 05 September 2008 - 07:12 PM

The PAE issue was addressed in one of the recent updates (don't remember if it was V3.20 or V3.21).

#12 Charlie Hein

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Posted 05 September 2008 - 08:01 PM

What it the correct procedure for PAE. Do you always have to clear the previous.


Sems to me that unless you have a permanent setup you'd have to clear out the PAE every time, or maybe drift align to the same precision every time.

Typically your mount is not going to be aligned exactly the same from session to session otherwise - and if this is the case then how could PAE be expected to work properly between sessions?

FWIW, I always clear the data between sessions - I've never attempted to re-use it.

Charlie

#13 Skylook123

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Posted 06 September 2008 - 09:35 AM

According to the documentation, PAE data is maintained until the next stellar alignment (even if the power is cycled), or it can be deleted with the hand controller's menu.

For SynScan, the sky is broken up into 88 regiors. Not sure what happens under the hood if a duplicate PAE is used for the same object; my assumption is that it adds to the "list", since the azimuth/elevation have changed, one purpose of PAE is to correct mount behaviors in the specific region associated with the PAE object at the time of PAE, and the same object may cross a boundary into a new zone. I've seen it happen during some outreaches when I use PAE on an object in case I need to come back to it. For some time, the returns will be dead perfect. Later on, GOTOs to the part of the sky where the original object used to be are very good; GOTOs to the old object are not as precise as previously. This actually can help in some cases, like when I'm looking at galaxie groups that sweep through the same piece of sky.

Until a new stellar alignment is performed, it adds to the current PAE set if an object in a new section of sky is chosen, even if the power is cycled, to keep refining the GOTOs for setups that haven't been moved or relocated. Stellar alignment (and, presumably, current PAE) is not saved if Park isn't used prior to shut down.

#14 wmyers

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Posted 08 September 2008 - 04:18 PM

I used to have a great deal of trouble with my Atlas and SynScan 3 star alignment. I started pointing the scope at Polaris before starting the process and my errors have been substantially reduced. I don't know if that is something that I should have known or if it was blind luck but it's been working for me.

wynn

#15 luu5

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Posted 08 September 2008 - 04:35 PM

Atlas parking position is to north pole?

#16 PGW Steve

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Posted 08 September 2008 - 05:15 PM

I've always had great success with 3 star so I've never used anything else. The odd time I get "alignment failed" but only because I center an incorrect star because my knowledge of named stars is limited.

#17 wmyers

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Posted 08 September 2008 - 09:06 PM

I'm not knowledgeable enough to state that home position is on polaris. I just know that I optically align the polar scope then optically put the scope on (or close) to polaris, then I power up the mount and go through the routine. Before I just started the routine with the scope pointed in a random direction. After starting at polaris, I almost always have a successful 3 star alignment.
I use a 5mm illuminated reticle eyepiece. (quite often, I have to switch back and forth with a wide field).

#18 Skylook123

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Posted 09 September 2008 - 07:36 AM

The nominal Home position is counterweight bar down, DEC = 90 degrees (the mount's DEC, not necessarily true DEC). "Park" means "Put me in a position at power off that I'll recall when power is applied the next time." The SynScan hand controller allows the user to associate the Home position with the Park location. The V3.x firmware also allows the user to choose some other orientation for Park, such as a stow position that allows a dome to close, or a roll-off roof to roll back on. The user can choose Park to Home (CW down, DEC=90), or Park to Another Location. If one of these options is chosen prior to shutting off power, the HC will assume that position as the starting point on the next power up. So, I guess "Park" is an action that establishes a repeatable position, "Home" is one orientation, and most folks will Park to Home. This makes alignment on the next power cycle easier, especially going to the first star, if polar alignment is also maintained.

#19 Eddgie

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Posted 09 September 2008 - 09:54 AM

For 3 star to work properly, the first two stars should be in one hemisphere (East or west) and the third star HAS to be in the OPPOSITE hemisphere.

If you use 3 stars in the same hemisphere, the mount will not calculate cone error.

I had an original EQ6 and even with the old Firmware, the 3 Star worked best.

Also, I aligned using a Telrad (I still do even with my C14 many times, though with THIS scope, it sometimes helps to use a 31mm Nagler). Always got excellent pointing simply by sticking the stars in the center of the Telrad Reticule...

Regards.

#20 mtb.daily

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Posted 23 May 2009 - 09:31 PM



Just to chime in here.


I always use 3 star and I use PHD with my guide-scope to do the alignment.

This way, I can center the mouse on the PHD screen and move the scope such that the alignment stars are always on the mouse.


Just be sure they are both pointing at the same target.

Then, I get dead on pointing.

-Jerry






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