Nexstar 8 Original Silver Align/ GPS Problem

Hi Lbrasci,

With that 90 degree consistency and presumably a now confirmed reliable power source, I would certainly go along with Jon's suggestions in as much as something in your basic entered data is screwing up the ability of this 'scope to align accurately.

Can you therefore make a double check along the lines he's mentioned: i.e. ensure that your time is either in military format or according to an appropriate am/pm : that the date is in accordance with American format: (mm/dd/yyyy) your Time Zone is set to EST : and that your lat./long. are correct and not transposed.

Can you please confirm ?

Best regards,
Tel

H Dan,

Please accept that I may well also be wrong when it comes to aligning an N8 as opposed to an N8i and "switching off" was/is indeed necessary. It's as I said: I just don't know with any certainty.

Best regards,
Tel

Tel:

I recently acquired an original Nexstar 5 which I believe uses the exact same mount as the Nexstar 8. I am not quite sure how the GPS is hooked up? I did not think there was an option for that.

In any event, this is what I have done:

I use a digital level to level the base and then point the scope north and level the scope itself. I have not switched off the scope after pointing it north. After that I enter the longitude and latitude, the time zone, the time. I select auto align and it points reasonably close to Sirius, I align it, it points reasonably close to Capella, I align it and it's done. After that it puts objects within the field of view of a 32mm Plossl.

According to what I am reading, this Nexstar 8 is off by 90 degrees or more. To miss that badly, I can only think that somehow the latitude or longitude have the wrong sign or that the time is being entered as a 12 hour number (7:00) rather than a 24 hour number (19:00).


Jon

Hi Jon,

I have checked my latitude and longitude here in Lighthouse Point, Florida (Latitude: 26-16 N
Longitude: 080-05 W) about 20 times and I am not exagerating and I have tried both 12hour and 24 hour formats. Maybe I need to try a digital level.

Thanks.

Ok here is the latest.

I have made the following changes and have gotten same results:

1. Brand new batteries out of the box.
2. Tripod digitally leveled.
3. OTA digitally leveled.
4. Pointing true North used 2 different digital compass to verify.

Same results about 90 degrees off. The batteries and 120v electrical power took me to same location for sirius when I ran test. I guess brightside to all this is that its consistent with sirius location.

This is driving me nuts.

Sorry, Lb, but the last comment is unclear to me.

Are you saying that when you carry out an "Auto Align" and choose Sirius as your first alignment star the 'scope does in fact reach Sirius' basic location but that the second alignment star is 90 degs. off as usual, OR, that even in making its slew to Sirius, this slew still ends up 90 degs. off ?

Best regards,
Tel

Sorry, Lb, but the last comment is unclear to me.

Are you saying that when you carry out an "Auto Align" and choose Sirius as your first alignment star the 'scope does in fact reach Sirius' basic location but that the second alignment star is 90 degs. off as usual, OR, that even in making its slew to Sirius, this slew still ends up 90 degs. off ?

Best regards,
Tel

Hi Tel,

When I ran alignment Sirius was 90 degrees off when i used either batteries or electrical power. Sorry for the confusion. Thanks.

Additionally, does your hand controller version ask for a latitude co-ordinate followed by a choice between North or South and a longitude co-ordinate followed by a choice between East or West or, does it require you use a "plus/minus system.

Here I quote what Mike Swanson has to say on this subject from his book, "The Nexstar User's Guide".

Quote:

If your version of Nexstar asks for a + or - for latitude, + is north latitude.

Note that on the original Nexstar 5 and 8, storing your longitude and latitude in adjacent "stored locations" will corrupt the entries. This results in the Auto Alignment procedure missing the two alignment stars.

To prevent this problem, only store and use longitude and latitude in locations 0,4,8 or 1, 5, 9.

Does this information perhaps help ?

Incidentally, what HC version are you in fact using ?

Best regards,
Tel

Additionally, does your hand controller version ask for a latitude co-ordinate followed by a choice between North or South and a longitude co-ordinate followed by a choice between East or West or, does it require you use a "plus/minus system.

Here I quote what Mike Swanson has to say on this subject from his book, "The Nexstar User's Guide".

Quote:

If your version of Nexstar asks for a + or - for latitude, + is north latitude.

Note that on the original Nexstar 5 and 8, storing your longitude and latitude in adjacent "stored locations" will corrupt the entries. This results in the Auto Alignment procedure missing the two alignment stars.

To prevent this problem, only store and use longitude and latitude in locations 0,4,8 or 1, 5, 9.

Does this information perhaps help ?

Incidentally, what HC version are you in fact using ?

Best regards,
Tel

Hi Tel,

My controller gives me choice of W and E and + or - system. Yes I use + for my latitude. I have not stored any locations, I looked for stored location on the main menu but I couldnt find it. The only place it mentions stored location is when it asks if you want longitute and latitude saved. I guess what I can do is put my longitude and latitude on all 10 locations. Or maybe there is another way to reset to default settings or erase all? What is HC = hand controller? Incase hc is hand controller I checked it and there are no markings or wording to indicate model or version. I am assuming its the original the one with only 18000 objects. Thanks.

Update:

I again tried the 2 star alignment but it didnt work still says "bad alignment" eventhough I used 5 different stars.

Hi Lb,

Yes HC means hand controller.

Your HC version should be accessible via this part of Mike Swanson's Nexstar website.

http://www.nexstarsi...N58Firmware.htm

As to permanent entry of your lat./long. co-ordinates, you will find how to do this on page 15 of your manual.

I understood that you had downloaded the manual but just in case, it may again be accessed via Mike's site according to:

http://www.nexstarsite.com/Manuals.htm

Just look down the page until you see the listing for the N8 manual and if necessary download it.

I hope this helps.

I must now away to my bed as it's 01:30 hours here in the UK !

Best of luck and regards,
Tel

Hi Tel,

The HC version does not appear when I power on or when I press all 4 arrows when I power on as per recommended website.

Also, yeah I had previously read page 15 of the manual and it doesnt tell you how to delete.

Thanks and goodnight.

Who can I take the scope to so that they can diagnose issue? I wonder if its a matter of GPS calibration, giving it some maintenance, or does the computer need to be completely replaced. I wonder how much it would cost to fix and is it worth fixing in lieu of buying a new one. I actually called the dude that advertises on this site that offers repair services but he has yet to call me back this was 3 days ago.

If I were to sell it in its present condition how much would it be worth? Optically and mechanically its perfect just the GPS and/ or computer issues. I guess if someone is looking for an 8" celestron nexstar and they dont need the computerized part it would be perfect for them.

Hi Lb and good morning !

Some overnight thoughts.

1) Without attempting to make any alignment at all, have you checked that both axes rotate freely in as much as the altitude axis can be powered via the HC, from a point where the 'scope tube, (OTA), is almost resting on the base of the mount to the vertical and back again without any signs of slippage, or other recognisable drive anomalies ?

(Note that with certain accessories added to the back end of the 'scope, it may not be possible for the OTA to reach the vertical before they make contact with the mount's base so remove all for the purpose of this test).

Assuming that the Alt. axis moves freely in both directions and you assess its clutch to be adjusted to the correct amount of tension so as to prevent the OTA from dropping under its own weight while at the same time not to be so tight as allow the drive motor to struggle, move on to checking the azimuth axis.

Rocking the mount base gently by hand from side to side, is there any excessive movement present ? A couple of millimetres either side is permissible but much more and this might be indicative of a problem.

Having checked for this freeplay, does the azimuth axis rotate a full 360 degrees in both directions under power with no sound anomalies which might suggest wear, missing gear teeth or slippage/looseness of the drive motor and thus overall only partial engagement of the drive mechanism ?

2) When you perform an "Auto Align", do you access the 90 degrees slew error to be in the altitude axis, the azimuth axis or both?

For example, when slewing to Sirius, the altitude axis will be raised from its original horizontal position by a certain amount but thereafter when the 'scope makes its second slew to Capella, it should be raised even more: Capella being at a higher altitude in the sky than Sirius.

Does this seem to be the case ? If so, then the Alt. axis is probably OK. This would therefore equally suggest that the problem is confined to the azimuth axis.

Overall therefore, if we can pinpoint whether the problem lies in any particular axis, I'm sure this would help in establishing the cause.

Hoping these thoughts help,
Best regards,
Tel

Hi Lb,

Our posts seem to have crossed ! My, you get up early in the morning ! It's only ca. 9:30am over here in the UK !

Over and above what I've just suggested and in respect of your latest posts, I would first and foremost leave the GPS out of the equation. At this stage we are trying to determine where the fault is within your 'scope and the GPS is only an accessory. The 'scope, in full running order, will function with or without it. Therefore it is superfluous and indeed only a complication to the solution of this problem.

As to repair or selling, I can't advise. Being an Englander, I have no idea of your marketing structures.

Best regards,
Tel

Hi Lb:

I think we need to clear up some possible confusion regarding the GPS you mention in the title of this post.

Do you indeed have a GPS unit on your scope? Note that the Nexstar 8 does NOT come with a GPS as a standard feature. A GPS would be an add-on for that scope, and I'm not even sure if one was sold which was compatible with that scope.

But if you did have one, it would be a separate box of some sort attached to the outside of the OTA or the mount, and it would have some cabling that connected it to the mount. Since the only connectors on that scope are the one in the handset cavity and the one on the bottom of the handset, I assume it would have to connect to one of those.

(Note that Celestron DID sell a model called the "Nexstar 8 GPS" which had GPS built-in, but it is a different mount than the one you have. It is a dual fork mount that is similar to the current CPC line of mounts.)

-Dan

I believe the Celestron CN-16 GPS unmit was imtroduced for the Nexstar "i" series as an option.I have a Nexstar 5i with CN-16 unit on top of the OTA.Theree is no socket to plug the CN-16 cord into on the original Nexstar 8.

I seem to recall the HC asking for an "offset" during the intial alignment.That is a number relating to how many timezones away from UTC(Greenwich)'if that is set incorrectly the positions will be off .
The fact the error in pointing is consist makes me think something is incorrect in the numbers being put into the HC.

Hi Lb and good morning !

Some overnight thoughts.

1) Without attempting to make any alignment at all, have you checked that both axes rotate freely in as much as the altitude axis can be powered via the HC, from a point where the 'scope tube, (OTA), is almost resting on the base of the mount to the vertical and back again without any signs of slippage, or other recognisable drive anomalies ?

(Note that with certain accessories added to the back end of the 'scope, it may not be possible for the OTA to reach the vertical before they make contact with the mount's base so remove all for the purpose of this test).

Assuming that the Alt. axis moves freely in both directions and you assess its clutch to be adjusted to the correct amount of tension so as to prevent the OTA from dropping under its own weight while at the same time not to be so tight as allow the drive motor to struggle, move on to checking the azimuth axis.

Rocking the mount base gently by hand from side to side, is there any excessive movement present ? A couple of millimetres either side is permissible but much more and this might be indicative of a problem.

Having checked for this freeplay, does the azimuth axis rotate a full 360 degrees in both directions under power with no sound anomalies which might suggest wear, missing gear teeth or slippage/looseness of the drive motor and thus overall only partial engagement of the drive mechanism ?

2) When you perform an "Auto Align", do you access the 90 degrees slew error to be in the altitude axis, the azimuth axis or both?

For example, when slewing to Sirius, the altitude axis will be raised from its original horizontal position by a certain amount but thereafter when the 'scope makes its second slew to Capella, it should be raised even more: Capella being at a higher altitude in the sky than Sirius.

Does this seem to be the case ? If so, then the Alt. axis is probably OK. This would therefore equally suggest that the problem is confined to the azimuth axis.

Overall therefore, if we can pinpoint whether the problem lies in any particular axis, I'm sure this would help in establishing the cause.

Hoping these thoughts help,
Best regards,
Tel

Hi Tel,

1. Scope moves freely 360 degrees and holds its own weight with no problem.

2. Based from your Sirius and Capella example it appears the altitude axis is ok and the problem is with the azimuth axis.

I hope we can figure this out.

Thanks.

Hi Lb,

Our posts seem to have crossed ! My, you get up early in the morning ! It's only ca. 9:30am over here in the UK !

Over and above what I've just suggested and in respect of your latest posts, I would first and foremost leave the GPS out of the equation. At this stage we are trying to determine where the fault is within your 'scope and the GPS is only an accessory. The 'scope, in full running order, will function with or without it. Therefore it is superfluous and indeed only a complication to the solution of this problem.

As to repair or selling, I can't advise. Being an Englander, I have no idea of your marketing structures.

Best regards,
Tel

Hi Tel,

I am just a night owl I go to sleep late. I sometimes stay up just to watch Saturn.

Hi Lb:

I think we need to clear up some possible confusion regarding the GPS you mention in the title of this post.

Do you indeed have a GPS unit on your scope? Note that the Nexstar 8 does NOT come with a GPS as a standard feature. A GPS would be an add-on for that scope, and I'm not even sure if one was sold which was compatible with that scope.

But if you did have one, it would be a separate box of some sort attached to the outside of the OTA or the mount, and it would have some cabling that connected it to the mount. Since the only connectors on that scope are the one in the handset cavity and the one on the bottom of the handset, I assume it would have to connect to one of those.

(Note that Celestron DID sell a model called the "Nexstar 8 GPS" which had GPS built-in, but it is a different mount than the one you have. It is a dual fork mount that is similar to the current CPC line of mounts.)

-Dan

Hi Dan,

My mistake I do not have a GPS. Thanks.

I believe the Celestron CN-16 GPS unmit was imtroduced for the Nexstar "i" series as an option.I have a Nexstar 5i with CN-16 unit on top of the OTA.Theree is no socket to plug the CN-16 cord into on the original Nexstar 8.

I seem to recall the HC asking for an "offset" during the intial alignment.That is a number relating to how many timezones away from UTC(Greenwich)'if that is set incorrectly the positions will be off .
The fact the error in pointing is consist makes me think something is incorrect in the numbers being put into the HC.

Hi BigC,

I wish I was entering the wrong numbers so that this headache would go away.

Hi Lb,

I wasn't quite clear from your above comment, whether you detected any freeplay in the azimuth axis if you tried to rotate it from side to side by hand.

I assume there is none or very little and thus the azimuth axis cannot otherwise be rotated by hand. (?) Could you confirm this to be the case ?

Assuming then that the altitude axis is OK, as you've indicated by the relative elevations it made in respect of slewing to Sirius followed by Capella, and that you are absolutely convinced all your HC data entries, (Time, Date, Time Zone, Standard Time Confirmation, Lat./Long Co-ordinates) are sound and correct; then I think the time is approaching to open up the base of the mount for inspection. Are you happy to do this if necessary ?

Best regards,
Tel

Hi BigC,

I wish I was entering the wrong numbers so that this headache would go away.

Here's a crazy suggestion:

So, the darn thing is pointing about 90 degrees off. Do an experiment, use the wrong time, starting with maybe 6 hours earlier and see how close it gets...

Is there a local astronomy club nearby where you might be able to find someone to come and look at the scope? How far are you from Mobile Alabama?

Last ditch effort: Send me the controller and I will test it on my Nextstar 5.

Jon

Hi Lb,

I wasn't quite clear from your above comment, whether you detected any freeplay in the azimuth axis if you tried to rotate it from side to side by hand.

I assume there is none or very little and thus the azimuth axis cannot otherwise be rotated by hand. (?) Could you confirm this to be the case ?

Assuming then that the altitude axis is OK, as you've indicated by the relative elevations it made in respect of slewing to Sirius followed by Capella, and that you are absolutely convinced all your HC data entries, (Time, Date, Time Zone, Standard Time Confirmation, Lat./Long Co-ordinates) are sound and correct; then I think the time is approaching to open up the base of the mount for inspection. Are you happy to do this if necessary ?

Best regards,
Tel

Hi Tel.

Yeah no freeplay when I tried to rotate from side to side. Yeah i am willing to do what it takes to get this resolved. I just dont want to damage any of the components, as I am not to handy.

Hi BigC,

I wish I was entering the wrong numbers so that this headache would go away.

Here's a crazy suggestion:

So, the darn thing is pointing about 90 degrees off. Do an experiment, use the wrong time, starting with maybe 6 hours earlier and see how close it gets...

Is there a local astronomy club nearby where you might be able to find someone to come and look at the scope? How far are you from Mobile Alabama?

Last ditch effort: Send me the controller and I will test it on my Nextstar 5.

Jon

Hi Jon,

Thats an interesting idea by tricking the scope its a different time in the day and see how close it gets.

Ill research to see whats the closest astronomy club in my area.

I am basically 35 miles North of Miami, Florida. So i am probably atleast 500-600 miles from Mobile Alabama.

Thanks.

This one looks good to me:

Southern Cross Astronomical Society

Jon

Update.

As suggested I did some experimenting with changing the time. I did an experiment for 8,7,6,5 and 6-1/2 hours before my actual time. At 6.5 hours before my actual time the scope is basically above Sirius but the altitude is off by approximatelly maybe 20 degrees higher ( I am guessing).

Maybe I need to experiment with my altitude?