Jump to content


Photo

Nexstar 8 Original Silver Align/ GPS Problem

  • Please log in to reply
75 replies to this topic

#1 Lbrasci

Lbrasci

    Sputnik

  • *****
  • Posts: 35
  • Joined: 20 Dec 2012
  • Loc: South Florida

Posted 31 January 2013 - 05:03 PM

My first post and first goto telescope.

I recently bought a used celestron nexstar 8 original silver and I am having hard time aligning by auto-align and 2 star align. On the the auto-align option I have North/level and entered the correct time, date, lattitude, longitude, etc so then the telescope automatically slews to sirius but it slews to another location not sirius, I have tried different stars but same result. Also with the 2 star alignment I make sure I am using the correct starts (I double checked with google night sky app)I picked sirius and capella but the telescope says "bad alignment" I have tried different stars but same result. Please help as I have watched and read about 5-6 hours worth of online literature with no success. One last thing when I go to menu and go to the azm /alt option and I am pointing telescope North and parrallel to ground it reads azm 193 degrees and alt -59 degrees. Shouldnt it be approximatelly 0 degrees and 0 degrees? I tried to trick the computer and used the 193/-59 degree location as my North and level but it did not work either. Thank you in advance as this has been driving me crazy,

#2 Arthur Dent

Arthur Dent

    Galactic Hitch-Hiker

  • *****
  • Posts: 3708
  • Joined: 23 Oct 2008
  • Loc: South Yorkshire, UK

Posted 31 January 2013 - 05:08 PM

Whoa!

3 duplicate posts.

Need to delete 2 of 'em!

Can't help with original NexStar8i though.

Art

#3 BigC

BigC

    Gemini

  • *****
  • Posts: 3274
  • Joined: 29 Sep 2010
  • Loc: SE Indiana

Posted 31 January 2013 - 09:59 PM

Check the handset for stored location.It might be defaulting to a previous owner's locatiion and thus skewing the results by a timezone. Is the result consistent and about how far off from the desired star?
I bought a used 8Se from a person who wasn't happy with it-said it never quite put the target into the eyepiece.Turned out he had never known changed the observing location stored in the handset,and the previous owner was several hundred miles and a timezone away.

If you don't have the manual try to download it from Celestron .

#4 WaterMaster

WaterMaster

    Moat Keeper

  • *****
  • Administrators
  • Posts: 9528
  • Joined: 17 Feb 2010
  • Loc: Southeast Idaho, USA

Posted 01 February 2013 - 12:24 AM

I had another thought - I once spent an agonizing night of alignment failures before I realized I had not changed the Daylight Savings Time setting. :foreheadslap:

Also, I would think your encoders should read 0 and 90 when pointed due north and level, but I've never used that function. At first I thought maybe the OTA had been mounted backwards, which would give you 180 and -90 (or maybe 270), which isn't that far off what you're seeing, but I would think if the OTA were mounted 'backwards' it would be obvious. :shrug:

Finally, check to make sure you have the correct hemisphere (your latitude entry needs to be North).

#5 Lbrasci

Lbrasci

    Sputnik

  • *****
  • Posts: 35
  • Joined: 20 Dec 2012
  • Loc: South Florida

Posted 01 February 2013 - 03:25 AM

Check the handset for stored location.It might be defaulting to a previous owner's locatiion and thus skewing the results by a timezone. Is the result consistent and about how far off from the desired star?
I bought a used 8Se from a person who wasn't happy with it-said it never quite put the target into the eyepiece.Turned out he had never known changed the observing location stored in the handset,and the previous owner was several hundred miles and a timezone away.

If you don't have the manual try to download it from Celestron .


No information is saved once turned off. I downloaded the manual and it was no help. I would say final result is pretty consistence. Thanks for your input.

#6 Lbrasci

Lbrasci

    Sputnik

  • *****
  • Posts: 35
  • Joined: 20 Dec 2012
  • Loc: South Florida

Posted 01 February 2013 - 03:38 AM

I had another thought - I once spent an agonizing night of alignment failures before I realized I had not changed the Daylight Savings Time setting. :foreheadslap:

Also, I would think your encoders should read 0 and 90 when pointed due north and level, but I've never used that function. At first I thought maybe the OTA had been mounted backwards, which would give you 180 and -90 (or maybe 270), which isn't that far off what you're seeing, but I would think if the OTA were mounted 'backwards' it would be obvious. :shrug:

Finally, check to make sure you have the correct hemisphere (your latitude entry needs to be North).


I tried both daylight savings and standard time. My latitude is +26 degrees and longitude is W 80 degrees so what would be my encoders read if my telescope is pointed North and level? Is it azm 0 degrees and alt 90 degrees or azm 0 degrees and alt 64 degrees (90-26 my latitude)? Thanks.

#7 Lbrasci

Lbrasci

    Sputnik

  • *****
  • Posts: 35
  • Joined: 20 Dec 2012
  • Loc: South Florida

Posted 01 February 2013 - 03:47 AM

One more issue, its about 3:44am in Florida and I was trying to align and it freezes everytime I select AM for the time.

#8 Tel

Tel

    Cosmos

  • *****
  • Posts: 9125
  • Joined: 31 Mar 2006
  • Loc: Wallingford England

Posted 01 February 2013 - 05:37 AM

Hi Lbrasci,

Welcome to CN and to this forum ! :bow::bow:

There seems to be a number of factors coming together here to complicate the single objective of getting your Nexstar 8 (Original) to align and work, so let's try to dispense with some I would class as irrelevant at this stage.

In the first instance, forget about the "Get Alt/Az. Axis".

I have a Nexstar 8i mount which is very similar to yours and, in aligning my index marks on the 'scope and mount arm respectively to place the tube horizontally, my Alt. reading is ca. minus 53 degrees (cf. your minus 59 degrees) and the Az. figure can be anything subject to revoving the mount in azimuth ! I hasten to add I don't know why but nether do I care. I have never had cause to use this function.

So to the more relevant:

Assuming that you are indeed entering your correct (standard) time and date and have installed the appropriate, Time Zone (EST) plus you Latitude and Longitude and that you choose, (say), "Auto Align", you appear to refer to the fact that having chosen Sirius followed by Capella, the scope slews, (to one after the other), in their respective directions but misses both. (?)

If this is true; now comes the dumb question: if in slewing the 'scope misses, (by say, not more than a degree or two), the first alignment star, (Sirius), are you actually manipulating the hand control direction buttons to bring it into view in your eyepiece ?

If not and you are merely entering it as an "Align" then you will never get a successful alignment. (Similarly with the second alignment star, Capella).

I repeat, I know the question is a dumb one and if you are centralising your alignment stars in your eyepiece then please forgive me for asking, but with problems like this every piece of information gained helps to solve the puzzle.

However, in referring to the above, what complicates this issue (for me), is that you mentioned you had also used the "manually" applied "Two Star Align", in which case you would have had to manually slewed the 'scope in turn to both alignment stars and centralised both in your eyepiece. Is this not true and this is in fact what you did when applying this alternative alignment method ?

Stick with it: I'm sure we can come up with an answer ! :idea:

Best regards,
Tel
Edit: BTW. I don't have any answers at the moment regarding the "AM" time issue, but this can be easily check tested as to whether the problem DOES indeed exist by merely entering any time value between say, 12:01 and 11:59 and applying an AM value to it.

If the hand controller just won't accept an AM value, then obviously therein lies "the" or an additional problem to consider.

#9 Bob Griffiths

Bob Griffiths

    Getting Grouchy

  • *****
  • Posts: 10646
  • Joined: 10 Oct 2005
  • Loc: Frederick Maryland

Posted 01 February 2013 - 01:17 PM

...DO YOU IN FACT have a GPS unit hooked up to the scope...???

1 If so what does it indicate you position as..and what time is it showing..???

Now have you calibrated the GPS unit? (I'm assuming its a Celestron CN-16) for both NORTH and for LEVEL... I'm guessing not because you have to actually get it aligned before you can do that.. and you have not...

BUT the previous owner may have calibrated it and now the scope may actually be altering or over or under compensating trying to actually find North and level.. Just food for though... and I'd like to know if you hear a rattle in the GPS unit if you tilt it back and forth ..you should as a simple ball bearing rolls around and that ball bearing has been know to get stuck...

I always run my scope on Standard time year round
and in the summer I just make sure the scope (the time the GPS displays) is 10 PM instead of 9 PM like my watch tells me ...

I sure would not expect the scope to slew directly to either of your first 2 alignment stars.. It usually is way off on the first and completely out in left field on the second...Because its still guessing where the heck it is

One more question...are you sure its a plain 8 with one port in the base or is it an 8i with 2 ports ts in the base... Several of us still run 8i's but I do not know of anyone still running a original 8

Bob G.

#10 Lbrasci

Lbrasci

    Sputnik

  • *****
  • Posts: 35
  • Joined: 20 Dec 2012
  • Loc: South Florida

Posted 01 February 2013 - 02:32 PM

Hi Lbrasci,

Welcome to CN and to this forum ! :bow::bow:

There seems to be a number of factors coming together here to complicate the single objective of getting your Nexstar 8 (Original) to align and work, so let's try to dispense with some I would class as irrelevant at this stage.

In the first instance, forget about the "Get Alt/Az. Axis".

I have a Nexstar 8i mount which is very similar to yours and, in aligning my index marks on the 'scope and mount arm respectively to place the tube horizontally, my Alt. reading is ca. minus 53 degrees (cf. your minus 59 degrees) and the Az. figure can be anything subject to revoving the mount in azimuth ! I hasten to add I don't know why but nether do I care. I have never had cause to use this function.

So to the more relevant:

Assuming that you are indeed entering your correct (standard) time and date and have installed the appropriate, Time Zone (EST) plus you Latitude and Longitude and that you choose, (say), "Auto Align", you appear to refer to the fact that having chosen Sirius followed by Capella, the scope slews, (to one after the other), in their respective directions but misses both. (?)

If this is true; now comes the dumb question: if in slewing the 'scope misses, (by say, not more than a degree or two), the first alignment star, (Sirius), are you actually manipulating the hand control direction buttons to bring it into view in your eyepiece ?

If not and you are merely entering it as an "Align" then you will never get a successful alignment. (Similarly with the second alignment star, Capella).

I repeat, I know the question is a dumb one and if you are centralising your alignment stars in your eyepiece then please forgive me for asking, but with problems like this every piece of information gained helps to solve the puzzle.

However, in referring to the above, what complicates this issue (for me), is that you mentioned you had also used the "manually" applied "Two Star Align", in which case you would have had to manually slewed the 'scope in turn to both alignment stars and centralised both in your eyepiece. Is this not true and this is in fact what you did when applying this alternative alignment method ?

Stick with it: I'm sure we can come up with an answer ! :idea:

Best regards,
Tel
Edit: BTW. I don't have any answers at the moment regarding the "AM" time issue, but this can be easily check tested as to whether the problem DOES indeed exist by merely entering any time value between say, 12:01 and 11:59 and applying an AM value to it.

If the hand controller just won't accept an AM value, then obviously therein lies "the" or an additional problem to consider.


Hi Tel,

When the telescope slews over to any of the stars (Sirius, capella, vega, etc) it misses by more than 90 degrees. After it misses by more than 90 degrees I have manually centralizing the stars within the eyepiece and then pressed align and repeated process for second star but it says bad alignment.

"However, in referring to the above, what complicates this issue (for me), is that you mentioned you had also used the "manually" applied "Two Star Align", in which case you would have had to manually slewed the 'scope in turn to both alignment stars and centralised both in your eyepiece. Is this not true and this is in fact what you did when applying this alternative alignment method ? "

Im not sure what you are trying to say here. But when i did the the 2 star align i would pick Sirius and then manually slew to sirius centralizing it on my eyepiece and then repeat process for second star but hand controller says bad alignment.

Thanks for your input and encouragement.

#11 Lbrasci

Lbrasci

    Sputnik

  • *****
  • Posts: 35
  • Joined: 20 Dec 2012
  • Loc: South Florida

Posted 01 February 2013 - 02:49 PM

...DO YOU IN FACT have a GPS unit hooked up to the scope...???

1 If so what does it indicate you position as..and what time is it showing..???

Now have you calibrated the GPS unit? (I'm assuming its a Celestron CN-16) for both NORTH and for LEVEL... I'm guessing not because you have to actually get it aligned before you can do that.. and you have not...

BUT the previous owner may have calibrated it and now the scope may actually be altering or over or under compensating trying to actually find North and level.. Just food for though... and I'd like to know if you hear a rattle in the GPS unit if you tilt it back and forth ..you should as a simple ball bearing rolls around and that ball bearing has been know to get stuck...

I always run my scope on Standard time year round
and in the summer I just make sure the scope (the time the GPS displays) is 10 PM instead of 9 PM like my watch tells me ...

I sure would not expect the scope to slew directly to either of your first 2 alignment stars.. It usually is way off on the first and completely out in left field on the second...Because its still guessing where the heck it is

One more question...are you sure its a plain 8 with one port in the base or is it an 8i with 2 ports ts in the base... Several of us still run 8i's but I do not know of anyone still running a original 8

Bob G.


Hi Bob,

How do I verify if the GPS is hooked up? Maybe GPS needs calibration. It doesnt indicate position or time no information is saved once unit is turned off, I have to manually enter all info. The telescope does not automatically go to North and level I have to manually slew it over as per instruction on hand controller. I see one port (looks like telephone jack) on the backside of the hand controller. I am not sure if its the 8i or 8 I took a picture of it. Thanks.

Attached Files



#12 Tel

Tel

    Cosmos

  • *****
  • Posts: 9125
  • Joined: 31 Mar 2006
  • Loc: Wallingford England

Posted 01 February 2013 - 04:15 PM

Hi Lbrasci,

No answers yet as such, but to clarify:

1) If your mount has no plug-in ports on the top of its battery box, then it will be a Celestron 8. If there are two ports on the battery box, (one labellled "Aux" the other, "Auto Guide"), then it will be a Celestron 8i.

2) "Two star Align", as opposed to "Auto Align".

Yes, what I meant was that with an N8/N8i "Auto Align", the 'scope makes both slews to the chosen alignment stars so obviously there is room for error as Bob indicated. In other words, it would be a sound bet that the slews might well miss their target star, (but not by much), demanding further manual slewing action on your part to bring said star into the centre of the eyepiece.

However noting that you have also carried out a "Two Star Align", you would have had to have moved the 'scope yourself, (via the hand controller's direction buttons), to each alignment star in turn. All this therefore and the fact that your 'scope under an "Auto Align" is ending its slews adrift by ca. 90 degrees, tells me that something is more seriously amiss here than mere pointing and eyepiece centralisation errors. :idea:

So where next:

Well, at this stage I would recommend that you abort any attempts to incorporate the use of the GPS if you have not already done so, as this only introduces another unwanted variable to complicate the problem.

Secondly, and a question I should have perhaps asked at the onset: what sort of power source are you using ?

Best regards,
Tel

#13 Lbrasci

Lbrasci

    Sputnik

  • *****
  • Posts: 35
  • Joined: 20 Dec 2012
  • Loc: South Florida

Posted 01 February 2013 - 04:41 PM

Hi Lbrasci,

No answers yet as such, but to clarify:

1) If your mount has no plug-in ports on the top of its battery box, then it will be a Celestron 8. If there are two ports on the battery box, (one labellled "Aux" the other, "Auto Guide"), then it will be a Celestron 8i.

2) "Two star Align", as opposed to "Auto Align".

Yes, what I meant was that with an N8/N8i "Auto Align", the 'scope makes both slews to the chosen alignment stars so obviously there is room for error as Bob indicated. In other words, it would be a sound bet that the slews might well miss their target star, (but not by much), demanding further manual slewing action on your part to bring said star into the centre of the eyepiece.

However noting that you have also carried out a "Two Star Align", you would have had to have moved the 'scope yourself, (via the hand controller's direction buttons), to each alignment star in turn. All this therefore and the fact that your 'scope under an "Auto Align" is ending its slews adrift by ca. 90 degrees, tells me that something is more seriously amiss here than mere pointing and eyepiece centralisation errors. :idea:

So where next:

Well, at this stage I would recommend that you abort any attempts to incorporate the use of the GPS if you have not already done so, as this only introduces another unwanted variable to complicate the problem.

Secondly, and a question I should have perhaps asked at the onset: what sort of power source are you using ?

Best regards,
Tel


Hi Tel,

Below the mount arm and on the side of the battery box there is a port for a in wall electrical plug (please see attached picture), there are no plug ports on top of the battery box.

I am connecting it to my electrical wall outlet using 120w. Should I try using batteries?

Thanks.

Attached Files



#14 Tel

Tel

    Cosmos

  • *****
  • Posts: 9125
  • Joined: 31 Mar 2006
  • Loc: Wallingford England

Posted 01 February 2013 - 05:36 PM

Hi Lbrasci,

Yes, that's the external power supply's receiving socket and I now see, from your earlier image, the cord feeding it from your mains wall socket; presumably via a suitable transformer.

Now, with the use of a transformer supply, there are a number of aspects to consider.


1) What is its rating ? (Input voltage/output voltage and max. current rating).

I also have to say that I wasn't sure what you meant by 120w ? Did you mean Watts or Volts or ...... ?

2) The cord connection, (jack plug), at the mount, should be of 5.5 mm outer diameter/2.1mm inner diameter. What you might find however, is that the jack plug's inner diameter is the more standard 2.5mm variety, which can lead, in this application, to possible intermittent electrical supply to the mount.

Does the connection feel at all loose particularly at the mount ?

3) You say you use mains supply from your wall socket as demonstrated by your first posted photo. However, is there enough wire there for when you take your 'scope outdoors ? In other words, how you are operating this 'scope outdoors in terms of power supply, is not clear.

Can you help us out on a fuller explanation ? An extension cord perhaps ?

4) Finally, yes, try some FRESH AA batteries in the mount rather than the power source you are using and check the effect. They will only give you something like a couple of hours' use but that will suffice to determine and compare the mount's electrical supply acceptance.

Do NOT though, connect both external supply in the presence of the batteries at this stage because as soon as the external supply is connected, the batteries go into a dormant state. Primarily, we need to isolate the internal battery power source from the external for the purpose of power source comparison.

Hoping this may reveal a little more as to the reasons for this odd behaviour.

Best regards,
Tel

BTW. That IS a Nexstar 8 you have there !

#15 Lbrasci

Lbrasci

    Sputnik

  • *****
  • Posts: 35
  • Joined: 20 Dec 2012
  • Loc: South Florida

Posted 02 February 2013 - 03:41 AM

Hi Lbrasci,


Yes, that's the external power supply's receiving socket and I now see, from your earlier image, the cord feeding it from your mains wall socket; presumably via a suitable transformer.

Now, with the use of a transformer supply, there are a number of aspects to consider.


1) What is its rating ? (Input voltage/output voltage and max. current rating).

I also have to say that I wasn't sure what you meant by 120w ? Did you mean Watts or Volts or ...... ?

2) The cord connection, (jack plug), at the mount, should be of 5.5 mm outer diameter/2.1mm inner diameter. What you might find however, is that the jack plug's inner diameter is the more standard 2.5mm variety, which can lead, in this application, to possible intermittent electrical supply to the mount.

Does the connection feel at all loose particularly at the mount ?

3) You say you use mains supply from your wall socket as demonstrated by your first posted photo. However, is there enough wire there for when you take your 'scope outdoors ? In other words, how you are operating this 'scope outdoors in terms of power supply, is not clear.

Can you help us out on a fuller explanation ? An extension cord perhaps ?

4) Finally, yes, try some FRESH AA batteries in the mount rather than the power source you are using and check the effect. They will only give you something like a couple of hours' use but that will suffice to determine and compare the mount's electrical supply acceptance.

Do NOT though, connect both external supply in the presence of the batteries at this stage because as soon as the external supply is connected, the batteries go into a dormant state. Primarily, we need to isolate the internal battery power source from the external for the purpose of power source comparison.

Hoping this may reveal a little more as to the reasons for this odd behaviour.

Best regards,
Tel

BTW. That IS a Nexstar 8 you have there !


Hi Tel,

1. Transformer supply input 100-240v 50/60hz 0.8A and output 12v 2.0A. Yea electricity supplied fom outlets is 120 volts.

2. Yes the connection does feel a little loose at the mount. I wonder if I am using the wrong transformer supply which is causing the problems.

3. I connect to outside/exterior outlets so there is always enough wire. No extension cord used.

4. Ill buy some batteries and test.

Thanks for your help and patience.

#16 Tel

Tel

    Cosmos

  • *****
  • Posts: 9125
  • Joined: 31 Mar 2006
  • Loc: Wallingford England

Posted 02 February 2013 - 05:10 AM

Hi Lbrasci,

No trouble at all ! I just hope we can crack this one ! :idea:

One or two thoughts overnight:

If you basically "kid" your 'scope into thinking you're setting it up for an observing session, i.e. by entering, say, 10:00pm (or 22:00h), and today's date, you can of course experiment with the problem at any time today and thus not have to wait until any "real" stars appear !

All you have to know is the rough positions of your chosen alignment stars, (in your choice Sirius and Capella), and make a mock alignment in the comfort of your living room as they say !

According to my estimation, Sirius will be almost due South from Florida at ca. 10:00pm (22:00h) while Capella will be due North so that in making your mock, (daytime), alignment, with its entered, false time, your 'scope should slew in turn, to these directions.

If however, the 'scope slews as you stated, some 90 degrees away from either of these positions using either mains or AA battery power, then this two stage experiment shows that it's unlikely that the problem is power supply related.

In carrying out this experiment, make sure your transformer cord is a tight fit at both ends. This you can effect at the mount, by CAREFULLY spreading the two halves of the receiving pin to gain a tighter cord fit.

Your transformer's specification is OK. Just make sure the cord connections are sound at both ends as described and, if you can, check the continuity of the cord wire itself.

Once we've established that the 'scope is slewing roughly to where it should and not some 90 degrees "off" each time then we can begin to accurise its performance.

One question though: the "90 degrees off" you recorded; is this consistent or can this "angle of miss" be random ?

Interested to learn how you get on,

Best regards,
Tel

#17 Tel

Tel

    Cosmos

  • *****
  • Posts: 9125
  • Joined: 31 Mar 2006
  • Loc: Wallingford England

Posted 02 February 2013 - 06:21 AM

A couple of afterthoughts :

1) Don't buy re-chargeable AA batteries.

Most only give a nominal 1.2 Volts leading to only a total of 8X1.5 = 9.6 Volts instead of 12 Volts to power the 'scope. This is insufficient, at least for the purpose of this expeiment, when a full 12V is required.

2) The Nexstar 8 is particularly sensitive to pre-alignment. Level the tripod with a bubble level and, after attaching the mount and tube, also level the tube in its pre-alignment horizontal position on the mount.

3) Point as near to due North as you are able. (Compass)?

This should help a little further to iron out some more of the variables.

Best regards,
Tel

#18 Midnight Dan

Midnight Dan

    Voyager 1

  • *****
  • Posts: 11436
  • Joined: 23 Jan 2008
  • Loc: Hilton, NY, Yellow Zone (Bortle 4.5)

Posted 02 February 2013 - 10:05 AM

Hi Lbrasci:

I'm coming in a little late to this party, but it looks like you're getting the usual excellent help from Tel and others. Just wanted to add a couple of thoughts.

When you set the scope to north and level, do you do so BEFORE turning the power on? When powered on, the scope assumes that the current position is north and level so you have to do that first. If you use the handset to slew it to a north/level position before alignment, then be sure to power it off then on again so it resets the software to the new position as north/level.

Also, I believe Tel suggested you abandon the use of the GPS at this point. Have you tried it again with the GPS disconnected?

-Dan

#19 Tel

Tel

    Cosmos

  • *****
  • Posts: 9125
  • Joined: 31 Mar 2006
  • Loc: Wallingford England

Posted 02 February 2013 - 11:11 AM

Hi Dan,

It is possible that this power "switch off" is a necessity when North aligning the Nexstar 8 and certainly can do no harm to perform, but having bought its successor, the Nexstar 8i, back in '06, this step was not required.

Indeed, such was the case with the N8i, that the "Auto Align" procedure required one to switch on, enter time, date and confirm HC retained data, and then, to a further HC prompt, "Move the optical tube to its North and Index position".

Once this "Move" was established and "Entered", the HC would merely proceed to the next stage of the alignment operation. (Note however that there are no index marks on the original N8, so accurate bubble levelling is advisable. Index marking can of course be made/added on a DIY basis at any time).

Incidentally, the method I used to use to ensure I had a good "North Alignment", was to place Polaris in my EP before starting any alignment procedure and then, by means of the "down" button on the HC, bring the OTA back down to align the index marks without moving the mount at all in azimuth.

In Lb's case here, however, this may not be so easy or even an option at Polaris' altitude of ca. 26 degrees in Southern Florida, compared to my UK ca. 52 degrees !

On the other hand, if he does have free access to Polaris with his 'scope, I believe it's a good method for achieving an accurate, initially required "North" alignment.

Best regards,
Tel

#20 Midnight Dan

Midnight Dan

    Voyager 1

  • *****
  • Posts: 11436
  • Joined: 23 Jan 2008
  • Loc: Hilton, NY, Yellow Zone (Bortle 4.5)

Posted 02 February 2013 - 11:29 AM

Hi Tel:

Indeed, such was the case with the N8i, that the "Auto Align" procedure required one to switch on, enter time, date and confirm HC retained data, and then, to a further HC prompt, "Move the optical tube to its North and Index position".


Interesting! I owned an original 8 a few years ago when I first got into the hobby. I don't remember that step in the alignment procedure. Perhaps the 8 procedure is different because it doesn't have the index marks?

Of course, my memory isn't that great and it was a few years ago, so I certainly could be mis-remembering!

Posted Image

-Dan

#21 Tel

Tel

    Cosmos

  • *****
  • Posts: 9125
  • Joined: 31 Mar 2006
  • Loc: Wallingford England

Posted 02 February 2013 - 12:01 PM

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. :idea:

Best regards,
Tel

#22 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 44353
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 02 February 2013 - 02:54 PM

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. :idea:

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

#23 Lbrasci

Lbrasci

    Sputnik

  • *****
  • Posts: 35
  • Joined: 20 Dec 2012
  • Loc: South Florida

Posted 02 February 2013 - 03:20 PM

Hi Lbrasci,

No trouble at all ! I just hope we can crack this one ! :idea:

One or two thoughts overnight:

If you basically "kid" your 'scope into thinking you're setting it up for an observing session, i.e. by entering, say, 10:00pm (or 22:00h), and today's date, you can of course experiment with the problem at any time today and thus not have to wait until any "real" stars appear !

All you have to know is the rough positions of your chosen alignment stars, (in your choice Sirius and Capella), and make a mock alignment in the comfort of your living room as they say !

According to my estimation, Sirius will be almost due South from Florida at ca. 10:00pm (22:00h) while Capella will be due North so that in making your mock, (daytime), alignment, with its entered, false time, your 'scope should slew in turn, to these directions.

If however, the 'scope slews as you stated, some 90 degrees away from either of these positions using either mains or AA battery power, then this two stage experiment shows that it's unlikely that the problem is power supply related.

In carrying out this experiment, make sure your transformer cord is a tight fit at both ends. This you can effect at the mount, by CAREFULLY spreading the two halves of the receiving pin to gain a tighter cord fit.

Your transformer's specification is OK. Just make sure the cord connections are sound at both ends as described and, if you can, check the continuity of the cord wire itself.

Once we've established that the 'scope is slewing roughly to where it should and not some 90 degrees "off" each time then we can begin to accurise its performance.

One question though: the "90 degrees off" you recorded; is this consistent or can this "angle of miss" be random ?

Interested to learn how you get on,

Best regards,
Tel


Hi Tel,

I have tried experimenting during the daytime for different stars as I know the location of a star by using google sky app. The 90 degree off is pretty consistent even with other stars i.e. sirius, capella, vega, etc. Thanks.

#24 Lbrasci

Lbrasci

    Sputnik

  • *****
  • Posts: 35
  • Joined: 20 Dec 2012
  • Loc: South Florida

Posted 02 February 2013 - 03:31 PM

Hi Dan,

I have previously tried both:

I have power on and then slewed over to north and level. I also have tried north/level and then turned power off so when i turn on its already north/level. Both methods did not work.

How is GPS turned off/ disconnected? Thanks.

#25 Lbrasci

Lbrasci

    Sputnik

  • *****
  • Posts: 35
  • Joined: 20 Dec 2012
  • Loc: South Florida

Posted 02 February 2013 - 03:36 PM

A couple of afterthoughts :

1) Don't buy re-chargeable AA batteries.

Most only give a nominal 1.2 Volts leading to only a total of 8X1.5 = 9.6 Volts instead of 12 Volts to power the 'scope. This is insufficient, at least for the purpose of this expeiment, when a full 12V is required.

2) The Nexstar 8 is particularly sensitive to pre-alignment. Level the tripod with a bubble level and, after attaching the mount and tube, also level the tube in its pre-alignment horizontal position on the mount.

3) Point as near to due North as you are able. (Compass)?

This should help a little further to iron out some more of the variables.

Best regards,
Tel


Hi Tel,

I'll try item #2 (taking it apart/ leveling )and I use an phone app as a compass. Thanks.






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics