COMPLETED Old Nexstar 8 GoTo Issue

[astronomer2002]

I am trying to help a friend set up his old Nexstar 8 and it's got me beat at the moment.

The telescope is an original version from the 1990's and has a hand unit version of 2.12.12.6

I have checked the stored location is in the UK though I believe the 2 star alignment process for alt-az use doesn't use this. The date and time are also correct, though I notice it does not keep date and time up to date. When switched on it displays the date and time of the day it was last used. Maybe this is a clue? I don't know if this is how the scope is supposed to behave.

Anyway.........

I switch on and go through the 2 star alignment ie  set tube horizontal and then centre on 2 stars widely separated. I chose Vega and Capella.

It comes back and tells me it's aligned!

Easy - so far.

Then I tell it to slew to M45, nothing too hard to start with and not far from Capella, and it tells me it's below the horizon and starts to turn the scope upside down!

Turn off and start again. This time I choose Capells and Deneb. Congratulates me and tells me it's ready. As my second star was Deneb I suggested it might like to try going to M27. It tells me that is below the horizon and when I overide it the tube starts to go upside down.

This age of Nexstar appears to have the OTA permanently fixed in place so cannot be upside down. Also I figure if it was something like that then the alignment would fail.

I am now stumped. Can't see how it can calculate that it is aligned after I do the alignment and then not know where it is.

Any help would be greatly appreciated.

 

Ian B

 

 

 

Edited December 27, 2019 by astronomer2002

[Kusanagi]

I know you have said that the time and date are correct, but have you tried putting the day and month the other way round.

I.E.

mm-dd-yyyy   instead of    dd-mm-yyyy

Also have you checked that it is not switching itself 12 hours out, as I have just helped a friend sort his GOTO out which was doing something similar and that was set for AM instead of PM ( would do the alignment correctly, say it was aligned and then go to a totally different place to where the object you wanted to look at was ). 

[RT65CB-SWL]

Hi Ian/@astronomer2002 -can the firmware be updated? - if not maybe an email to: https://www.celestron.com/pages/support

[Mick H]

Also check slew limits for "it's below the horizon and starts to turn the scope upside down", and turn off cord wrap.

[joe aguiar]

I had that scope it came out spring of 2000 (just saying this is case you want to know precise date and 90's can be within 1990 to 1999 which is a big gap, plus it was after that anyway.) the 5" came out sept or oct 1999 ( I got the first shipment of the 8")

this model you also need to point it north in case u r not doing that, the other 2 suggestions are good too.

joejaguar

Edited November 21, 2019 by joe aguiar

[astronomer2002]

Thankyou for the suggestions. I'm sure the date is correct way round as there is no month 18!

From the Instruction Manual there appears to be no reference to date and time if yo are doing a 2 star alignment.  I would really like to know whether 2 star alignment needs all the date and time elements to be correct and the tube pointed North before it will work. It seems unlikely as it is relatively hard to get to the date, time etc through the menu.

I would also have thought the date and time would be accurate after the scope had been turned off for a couple of days rather than simply remembering the last date/time it was on. Not sure if something is broken here. Manual is unclear and there seems to be no battery to keep the clock running, which is another oddity.

It states you need the tube pointed North and horizontal plus the correct date and time for the Automatic alignment, which is understandable as it is then going to select alignment stars and slew to them.

Has anyone still got one of these original mounts or can remember if the 2 star alignment worked if the date was a couple of days out? I have had, and still have, quite a few mounts each with their own idiosyncrasies,  but this one seems either broken or the instructions are wrong

 

I am using this copy of the manual:

http://www.company7.com/library/celestron/nexstar_8_manual.pdf

Ian B

 

nexstar_8_manual.pdf

Edited November 21, 2019 by astronomer2002

[Hallingskies]

I have an old Nexstar 4 and no, the handset only remembers the time it was last turned off at, which is aggravating.  You have to enter the date and time afresh each time unless you have the GPS add-on.  It does sound like a date-time entry issue, although it might be worth checking your location details are accurate as well.  You will need to start with the scope pointing north and reasonably accurate date/time info whatever alignment scheme you choose.  Also, make sure you are getting a good solid 12v minimum to it.  My old Nexstar did not like dodgy power supplies or battery packs that were not fully charged.

[joe aguiar]

I had to enter time date year point north location bascally everything for it to work each time I powered it up and I don't recall it remembering the time from last session. even if it was there I probally just re entered new date time was no big deal. I think using it for like 12 years I only had 1 times it didn't align. and everytime I have it in the ep view.

joejaguar

[Davey-T]

I've got one somewhere but not used it for years, from memory you did indeed have to enter time etc every time it was used.

Does it come up with the same repeatable error if so you could maybe calculate where it thinks it is to get a clue to the problem.

How are you powering it, mine was very susceptible to errors at the slightest drop in power.

Dave

[PEMS]

Possibly a few things to check:

Is the location correct, the scopes used to want Longitude then Latitude whereas we talk of Latitude and Longitude. So make sure that 51.5 (51 30) is actually the Latitude and not the Longitude. Longitude would be about -0.5 (-000 30) at an estimate, check the leading zero's as you could end up at 30 degrees West not half a degree West.

Date and time is not remembered, you enter it each time and Date is US format, not UK format. If you get it wrong they do not inform you of any error.

In location check the timezone, they can default to Western Pacific Timezone which is UTC -8

They will need setting up at the start and Level and North (as it is often termed) is a reasonable choice. Would have expected the manual to have given a requirement but I guess back then they didn't bother as much.

From reading others posts I also suggest that you do a reset as that seems useful, even required, to clean out data in the memory that appears to hang around.

[astronomer2002]

Thankyou all for the heads up on date and time needed to be entered every time - seems it is a design feature rather than an issue just with this scope.

Still not sure if there is a battery somewhere that needs replacing to keep the entered data, or is it that one of the eproms is written to each time you enter anything? I'm used to hidden batteries in handsets or mother boards that die after a few years.

I'm running the scope off 12v 5a power supply that I use on several modern mounts, a lot simpler and cheaper than 8 AA batteries. I tried it with rechargeables but it didn't like the ~10v that provided.

The manual does not tell me to do anything more than put the tube horizontal for the 2 star align so I guess not orienting it North is going to be the issue. I really hope so as that is a simple 'fix'.

Dates/times/lat/long and time zone are all correct though I note the time zone seems to be lost when you turn the scope off as well.

I will try the set up procedure again - if we ever get clearish skies!

Ian B

 

 

[Anne S]

I owned the later 8SE which had a removable ota. Therefore it's possible to put the tube on pointing the wrong way. That might upset it....

[joe aguiar]

right the original one u cant take out the ota, altho I have seen some people unhinge the ota out, and swap the ota to a different scope. or install a mod that puts a vixen clamp to the arm allowing similar to the new design of using any scopes in the old model.

joejaguar

[The Admiral]

2 hours ago, astronomer2002 said:

Still not sure if there is a battery somewhere that needs replacing to keep the entered data, or is it that one of the eproms is written to each time you enter anything? I'm used to hidden batteries in handsets or mother boards that die after a few years.

I use the Nexstar 8SE in Alt-Az mode. All good advice above. I too can confirm that date/time entries are not retained. There is no internal battery in the handset to keep the data in the volatile memory, my mount had this behaviour from new. It is also very easy to enter the details incorrectly. Using AA batteries to power it they can give odd results as the voltage drops so a decent external power supply is really a must, as you already do. I don't use an SCT but mount a refractor on it, with the arm on the LHS of the scope, viewed from the eyepiece end, but I have never initialised the mount with the scope pointing North. May be the SE is different. All I do is make sure that the tripod is absolutely level before adding the mount. There are additional requirements if using the mount on a wedge and operating in EQ mode, such as aligning the index marks on the mount head and aligning the OTA with the meridian. I've always been a bit doubtful of using daylight saving time so I have only entered GMT (UCT).

Ian

Edited November 22, 2019 by The Admiral

[joe aguiar]

the original light grey u had to point north and level the tube to be level, that was still easy to do

joejaguar

[Cosmic Geoff]

Having to re-enter the date and time each time you turn it on is normal for a Nexstar.  It should retain the latitude and longitude once set.  There are plenty of settings to get wrong, any of which will cause it to point to the wrong bit of sky:  latitude/longitude, time zone, daylight saving, date format, time of day.    I have found that doing a daytime setup between noon and 1pm can also catch one out (should be 00hrs and PM).

If the scope points to the wrong patch of sky, I would respectfully suggest that it's telling you the settings are wrong, even if you think they are correct....   These scopes were made for the USA market, so all settings are in US formats.  Lat/long setting is also non-obvious and catches out many new users.

The current Nexstars do not need to be pointed North (or anywhere else) before starting alignment, with the exception of the Starsense accessory, but an old one with a mount that can be used in equatorial wedge mode may differ.  Is the mount being used in alt-az or equatorial mode, and are your settings consistent with this? (My Nexstar SLT has EQ North and EQ South in the menus, even though these seem to have no practical use in an alt-az outfit.)  I scrolled through the Nexstar 8 manual you cite, and note that it apparently tells you to start with the scope aligned North in order to locate the alignment stars.  AFAIK, Sky-watcher Synscan mounts still work this way, but the recent Nexstar mounts dispense with this and assume that (a) you can find alignment stars yourself or (b) the three star alignment (on three unidentified bright stars) will sort it for you.   I wouldn't try updating any firmware before you have got the system to work.  Later Nexstars use a different (Nexstar+) handset, but as all the clever stuff is in the handset, if you swap the handset for a later version it will probably work.  BTW, a Starsense system might work too (but check the small print).

The 5.5/2.1mm power plug on the recent Nexstars is not very good and can cause problems with poor contact.  Recently I had the plug on my C8SE shift during a session, scrambling the software, and the same night the OTA started traversing downwards at high speed in altitude, for no evident reason.  I suspect the plug again.

Edited November 25, 2019 by Cosmic Geoff
EQ

[michael8554]

For the sake of ticking one possible error off the list, select London as your location - this will be close enough for testing.

Enter date and time. 

Once you have your Alignment Successful message, go into the handset menus to "Get ALT-AZ" reading, while you're still pointed at the second star.

Is this reading correct compared to a Planetarium?

Try a goto an object north of your second alignment star - eg M39  from Deneb. 

This can't possibly be below the horizon ........... 😆

Tell us how you get on !

Michael

 

 

 

[astronomer2002]

Thankyou for all who posted suggestions, they have all been very helpful.

As I said initially I have no knowledge of this scope and was working on the assumption there was an issue as my friend, who has had it for many years, indicated it no longer worked.

I have finally got it to work properly in alt-az mode.

The key was to start with the scope pointing North and to have the single arm on the west side of the mount.

 

My process was:

Switch on

Pont scope at Polaris (suggested here)

Move tube to horizontal with aid of spirit level

Set time and date and check location

Select 2 star alignment and choose Deneb

Drive to Deneb and centre in ep. Press Align

Select Capella and drive to it through southern path (ie not going through North)

Centre Capella in ep and press align

Get the usual 'congratulations' message

Tell scope to drive to M37 - Eurika - it does!

Tell scope to drive to M57 - once again it does.

Tell scope to goto M15 - it's in the ep!

 

Basically nothing wrong with the scope when set up like this. I have not tried the other methods but don't believe there is anything wrong, except the large gear backlash which seems endemic.

 

Thankyou all again

 

Ian B

 

 

Edited December 4, 2019 by astronomer2002

[michael8554]

Well done for getting it going

Michael 

[Mick H]

Agree, glad you got it going. I hope you have many clear skies.

[Cosmic Geoff]

On ‎04‎/‎12‎/‎2019 at 09:22, astronomer2002 said:

Basically nothing wrong with the scope when set up like this. I have not tried the other methods but don't believe there is anything wrong, except the large gear backlash which seems endemic.

That's normal. 😕