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130SLT GoTo alignment problem

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#1 TheNosy1

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Posted 30 March 2013 - 11:58 AM

Hello everyone, I've tried aligning my 130SLT about 4 times already and every time its off by quite a bit. The last time I aligned it, as far as I knew I was doing everything correctly. I was using a power supply (not batteries), my mount was level with the ground, I double checked my long and lat co-ordinates and I entered the time to withing + or - 1 minute of the correct time. The method of aligning which used was auto 2 star align. The first star I chose was Dubhe and the second (as recommended by the scope) was Sirius. I'm fairly confident I centered my two stars in my eyepiece as well. What could I be doing wrong!?

Any help would greatly be appreciated! Thank you in advance!

#2 Dave L

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Posted 30 March 2013 - 01:33 PM

Are you using two star manual or two star auto? Try using manual two star only. Choose stars that are far apart. Make sure that you are choose the second alignment star in the same direction as the scope usually goes. For example if the scope aligns goes towards the right rotation, that is the rotation that you should go when aligning the scope. Also try reseting the hand control to factory settings, If none of this works,and the mount is still under warranty, call Celestorn for an RMA.

#3 WarmWeatherGuy

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Posted 30 March 2013 - 03:12 PM

The auto 2-star align works great unless you choose the first star that is too high in the sky. Your location isn't given so we can't tell if Dubhe is high for you or not.

When you begin the computer knows your longitude, latitude, and time of day. It already knows which star is straight overhead but it doesn't know which way is North. If you choose a star that is overhead, and then point the scope straight up, you are not giving it much new information. If you pick a star closer to the horizon then it can figure out which way is North.

If your eyepiece doesn't have cross-hairs then you can defocus the star which makes it a big donut. That big donut is easier to center in the eyepiece more accurately.

These are just some ideas that might help.

#4 dragonslayer1

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Posted 30 March 2013 - 03:14 PM

and verify date as well as time and DST on
Kasey

#5 Tel

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Posted 30 March 2013 - 03:48 PM

Hi Nosy1,

It would certainly help (me) to learn your approx. location but despite this, I think the first question to pose, (assuming you are convinced that you have entered your co-ordinates, time zone, time and date correctly), is as follows.

If you are absolutely sure you centralised Dubhe and no other star when performing your Auto Two Star Align, how far adrift from Sirius would you estimate your 'scope to have been when it ended its automatic second slew ? (i.e. Just outside the FOV of your EP, a few degrees or "miles" off) ?

Additionally, what focal length EP were you using ?

Best regards,
Tel
An afterthought:

Is this the first time you've aligned in this way: (the 'scope being new to you); or is this a problem which has just arisen following many normally successful alignments in the past ?

#6 TheNosy1

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Posted 30 March 2013 - 07:24 PM

"Is this the first time you've aligned in this way: (the 'scope being new to you); or is this a problem which has just arisen following many normally successful alignments in the past ? "

Nope it has pretty much been the same.

When it tries to slew towards Sirius its miles off (about an extended hand length from pinky to thumb) :p. (It still says alignment success though)

My approx location is Nice, France. And yes, Dubhe was quite high in the sky, so probably not a great place to start then.

I was using a 25mm TS Optics plossl 50degree AFOV.

#7 TheNosy1

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Posted 30 March 2013 - 07:29 PM

I'm pretty sure I did centralize Dubhe correctly though. The reason I did is because I read that its best to do your first alignment on polaris. And since polaris was obstructed where I was, I chose to go for Dubhe which was close-ish according to my application.

#8 Tel

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Posted 31 March 2013 - 03:52 AM

Hi TheNosy1,

I hope I'm on the right track here, but checking with Stellarium planetarium this morning, Dubhe will only reach a maximumum altitude over Nice of ca.72 degrees at between 23:00h and 00:00h UTC, so using it as an alignment star should present no problems particularly since you probably used it at a lower angle anyway. (?)

Secondly, you advise that in making its automatic slew to Sirius, having aligned Dubhe manually according to the Auto Two Star procedure, it appears to be "off target" by the width of an outstretched hand at arm's length. This sounds suspiciously like ca. 15 degrees or 1 hour in time.

Assuming therefore that your fixed and retained entered co-ordinates, (latitude/longitude), relate to:

Approx. North 43^ 42' 0" / East 7^ 16' 12"

Time Zone +1 hour.

And that your date imput is in US. format (month/day/year). (You must have entered this correctly since under European format dd/mm/yyyy, 30/03/2013 would be rejected. (There are only 12 months in anyone's year) ! :lol:

Thus, carrying out an experiment with my Nexstar 81 mount this morning, it seems ever likely that the 15 degree variation is brought about simply by switching from "Standard Time" displayed on the hand controller to "Daylight Saving".

Keeping all other parameters the same therefore, I would suggest that before anything else, you repeat your alignment keeping to a "Standard Time" display on the hand controller, (which, as from today, will be one hour behind that which your watch is now showing; Middle European Time plus 1 hour having started this morning.

Also if you wish, repeat the above having this time selected "Daylight Saving" with current MET +1h and you should observe the same resulr, (this time a favourable one I hope) !

Incidentally, although I showed a difference of 15 degrees for Sirius according to the "Standard Time" or "Daylight Saving" I chose, (keeping the input time the same in both cases), my hand controller still registered "Alignment Success" under both test regimes; much in the way yours did with that erroneous alignment! :idea:

Let us all know how it goes. If it isn't the answer we'll have to think again ! :idea:

Best regards,
Tel

BTW. You can test this out for yourself at any time of the day merely by "fooling" the 'scope with false input data.







#9 TheNosy1

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Posted 31 March 2013 - 04:51 AM

Thanks very much Tel! Extremely helpful as always! I really appreciate you trying to get to the bottom of this. I'll try switching to standard time and to daylight saving with MET +1 time tonight.

#10 Tel

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Posted 31 March 2013 - 05:36 AM

It's just all a guess as to whether the above resolves your alignment problem, but entering exactly the same clock/watch time while operating with "Standard Time" followed by a second test using "Daylight Saving", will produce a 15 degree difference while strangely enough, the HC records a successful alignment for both !

I only estimated you 'scope to be out by ca. 15 degrees based on the rough but recognised principle that a spread hand at arm's length represents ca. 15 degreees of sky, a clenched fist, ca. 10 degrees at the same distance, one finger, around half a degree etc.

Hoping therefore that a combination of "Standard Time" plus MET works or, conversely, "Daylight Saving" together with MET plus 1 hour (time now in France), produces the same result.

Remember, in terms of time, the heavens themselves couldn't care less whether it's Tuesday or Christmas ! Clock time is something invented by us through which we organise our daily social and commercial lives !

Best regards with fingers crossed for a successful outcome !(If not,......... back to the drawing board )!
Tel

BTW. Either of the above "seasonal" time inputs, (Standard or Daylight Saving), may not place Sirius in your EP. They may not even put it in your finder, but either, in combination with the correct Earth time, should place it much closer to your 'scope than hitherto. If this is so, then we are on the right track and will probably only need to carry out a little "tuning" !

#11 TheNosy1

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Posted 01 April 2013 - 03:26 AM

OK, so last night i switched to standard time and GMT+1 and the auto align on the second star was off by about 2 degrees. Which is good, so I aligned it perfectly and the alignment was successful. But when I used the tour function to go to some random objects, it was still off by about a 1/4 of a degree. I also nearly broke my handset as it wrapped around my scope :foreheadslap:. Could this have damaged the motor?

#12 Tel

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Posted 01 April 2013 - 04:42 AM

Hi TheNosy1,

You were lucky the cord wrap went no further and that you were able to spot it in time !

It's an easy matter to check out the hand controller and mount in broad daylight just to make sure all is well. I'm sure it is. Just repeat what you did last night.

To that end, select the same "Auto Two Star" alignment as I presume you did last night, enter the same time at which you began plus yesterday's date, and then, as the procedure directs, point the 'scope manually as directed to your first alignment star, (Dubhe ?). Obviously a little bit of guesswork will be necessary here but I'm sure you can estimate Dubhe's position reasonably well from last night's viewing !

Now press "Enter" followed by "Align" and then select Sirius (?) as your second alignment star. Press "Enter" and your 'scope should slew, automatically this time, to where Sirius would have appeared in your sky at the input time. If the position looks recognisable, press "Enter" and "Align" and then just try a few slews to some of the other objects you attempted to view.

If they are also in roughly the same positions as you remember them from last night to be, all should be well.

Note that if you wish, you can always set the "Cord Wrap" feature within the hand controller, which should, (but not always infallibly), prevent your HC and power source cables from wrapping around the mount or tripod legs.

As to the alignment itself last night; it sounds as if the main problem has been solved but that a small degree of "tuning" may now be necessary to "accurise" your 'scope.

Back to that soon. Meanwhile, can you advise as to what size EP you were using for your alignment last night ?

Best regards,
Tel
BTW. In that responding PM I've sent you this morning; I think I got my divergent lenses transposed with my convergent ones ! :foreheadslap:

#13 TheNosy1

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Posted 01 April 2013 - 05:36 AM

This time, as I was out at around 00:00 am last night, I aligned on Polaris and then Pollux. BTW I think I might have been off by about 1/2 a degree rather than 1/4 of a degree. I was using a 2x barlowed 25mm plossl 21.1 field stop and 50 degree field of view

#14 Maverick199

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Posted 01 April 2013 - 06:39 AM

Don't use your barlow for aligning. Align first, goTo first and then insert barlow where required, like on Planets for instance.

#15 TheNosy1

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Posted 01 April 2013 - 07:33 AM

Yeh ok, but surely that isn't the cause for the 1/2 degree inaccuracy, right?

#16 TheNosy1

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Posted 01 April 2013 - 09:25 AM

Oh BTW I have another problem. Whenever I press track on the hand set and select alt-az it just returns me to the menu... Is this supposed to happen?

#17 dragonslayer1

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Posted 01 April 2013 - 11:00 AM

As to the Barlow, if you don't have it or any other adaptor seated, positioned, or set right yes it can effect it... Also need true magnification when aligning I would say.
Kasey

#18 WarmWeatherGuy

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Posted 01 April 2013 - 11:14 AM

If you ever want to stop the slewing just press any of the 4 arrow keys.

#19 Tel

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Posted 01 April 2013 - 12:40 PM

Oh BTW I have another problem. Whenever I press track on the hand set and select alt-az it just returns me to the menu... Is this supposed to happen?


Which hand-controller are you using ? Is it the Nexstar + version with a Celestron logo on the bottom left-hand button or the old version with the word, "Info" on it ?

(Just so that we know what we are dealing with here).

Best regards,
Tel

#20 TheNosy1

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Posted 01 April 2013 - 04:30 PM

Its the one with the celestron logo on the bottom left button

#21 dragonslayer1

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Posted 01 April 2013 - 05:17 PM

If jumps to menu when trying alt az track and you have it set up as alt az and not EQ you might try reflashing the handset
Kasey

#22 Tel

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Posted 01 April 2013 - 07:29 PM

Can you perhaps give a better description of what's happening when you access "Tracking".

Not being familiar with the new hand controller, although it's described as being not too dissimilar from the old, presumably you press the "Menu" button to see "Menu / Tracking" appear on the screen ? If it is not immendiately displayed, again I presume you use either of the "Scroll" buttons until it DOES appear ?

Once on screen, I'm guessing you press "Enter". You should then see "Tracking / Mode" appear. Finally by pressing "Enter" once more, you should see "Tracking Mode / Alt./Az". ?

If you can confirm this, the only way back to the "Nexstar Ready" display is by pressing the "Undo" button whereby one press should take you back to a displayed "Tracking Mode" followed on a second "Undo" press by "Menu / Tracking" followed after a third by "Nexstar Ready".

The above is the sequence for the Version 4 hand controller display. Can you therefore please detail more fully where yours differs ?

Also, if you decide to reflash your firmware, (and I don't personally think it will solve your alignment problems), judging by the literature, there seems to be only one update available anyway.

See below.

www.nexstarsite.com/Firmware/SLTFirmware.htm

Reverting to your alignment problem, I'm sure you'd agree that the alignment is a lot closer now than its original 15 degrees off target. I therefore believe that the 'scope merely requires a little tuning for it to consistently hit its targets.

Best regards,
Tel

#23 TheNosy1

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Posted 02 April 2013 - 03:45 AM

With the original alignment it was just the second star that the scope automatically slewed to that was off by 15 degrees. The actual selecting things from the menu and then slewing to them part was off by about 1 degree. So the accuracy so far has improved by about 1/2 a degree in changing the time settings... About the controller:

Not being familiar with the new hand controller, although it's described as being not too dissimilar from the old, presumably you press the "Menu" button to see "Menu / Tracking" appear on the screen ? If it is not immendiately displayed, again I presume you use either of the "Scroll" buttons until it DOES appear ?

Yes, that's correct.

Once on screen, I'm guessing you press "Enter". You should then see "Tracking / Mode" appear. Finally by pressing "Enter" once more, you should see "Tracking Mode / Alt./Az". ?

Correct

If you can confirm this, the only way back to the "Nexstar Ready" display is by pressing the "Undo" button whereby one press should take you back to a displayed "Tracking Mode" followed on a second "Undo" press by "Menu / Tracking" followed after a third by "Nexstar Ready".

OK, I thought it would take me back to the nexstar ready display once I had selected a tracking mode.

What does it sound like when the motor is tracking? Because mine sounded like it was having little spasms in the motor is this what its supposed to sound like? When I tried looking at saturn, it was still slowly deviating from my field of view. But I guess that's normal as the tracking isn't relative to a particular object, but relative to the rotation of the earth.

Hope to hear from you again Tel and thank you very much for your replies and your future replies :).

#24 hopskipson

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Posted 02 April 2013 - 06:55 AM

I have the 8se and when it's tracking it sounds like a very quiet ticking. Saturn should stay in the field of view for awhile if your backlash settings and alignmeny proceedures are in order. I find that if I mess up the alignment by not centering the stars with the down and right buttons the tracking will not hold the object for long. I'm sure Tel can explain further.

#25 Tel

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Posted 03 April 2013 - 04:51 AM

With the original alignment it was just the second star that the scope automatically slewed to that was off by 15 degrees. The actual selecting things from the menu and then slewing to them part was off by about 1 degree. So the accuracy so far has improved by about 1/2 a degree in changing the time settings... About the controller:

Not being familiar with the new hand controller, although it's described as being not too dissimilar from the old, presumably you press the "Menu" button to see "Menu / Tracking" appear on the screen ? If it is not immendiately displayed, again I presume you use either of the "Scroll" buttons until it DOES appear ?

Yes, that's correct.

Once on screen, I'm guessing you press "Enter". You should then see "Tracking / Mode" appear. Finally by pressing "Enter" once more, you should see "Tracking Mode / Alt./Az". ?

Correct

If you can confirm this, the only way back to the "Nexstar Ready" display is by pressing the "Undo" button whereby one press should take you back to a displayed "Tracking Mode" followed on a second "Undo" press by "Menu / Tracking" followed after a third by "Nexstar Ready".

OK, I thought it would take me back to the nexstar ready display once I had selected a tracking mode.

What does it sound like when the motor is tracking? Because mine sounded like it was having little spasms in the motor is this what its supposed to sound like? When I tried looking at saturn, it was still slowly deviating from my field of view. But I guess that's normal as the tracking isn't relative to a particular object, but relative to the rotation of the earth.

Hope to hear from you again Tel and thank you very much for your replies and your future replies :).


Hi TheNosy1,

I'm now somewhat confused about this "15 degree off target aspect" but I think I understand. (?) However, your 'scope being half a degree more accurate now in slewing to objects following a successful alignment, is very unlikely to be attributable to the time adjustments I suggested you made.

But let's not dwell on that. It would seem, (and please correct me if I'm making the wrong assumption), you are now achieving successful alignments via the Auto Two Star Align procedure but that your slews, to the objects you choose to view, are now only slightly "off". ( ca. 0.5 deg.) (?)

It therefore seems to me that, (as mentioned a while ago), your 'scope just needs a little tuning.

To that end, perhaps cast your eye therefore over the various procedures for tuning and alignment accuracy I put together in the following CN Nexstar thread some time ago. (Page down counting to post number 19).

Equally so, if you are having difficulties holding objects in the field of view of any given eyepiece, take a look at the first post on the same CN thread.

I would however emphasise that you should read post 19 first and establish whether your particular 'scope would benefit from any of the "tuning tips", (for want of a better description), before proceeding to review post 1.

http://www.cloudynig...5417848/page...

Hoping this helps,

Best regards,
Tel






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