SkyWatcher 10" Dobsonian GOTO Setup Issues

[bluesilver]

Hi,  I currently have the 10" SkyWatcher Dobsonian with GOTO

I have just been playing around with it viewing planets for the last few months,  using either the motors to slew the scope around or when i have it on my trolley cart,  just manually moving it around.

The only reason i have been doing this is because i just for some reason can not get the GOTO system to align with the stars.

I am trying to do the two star alignment and so far having no luck at all,  i figure i am doing something wrong or must have missed a important step somewhere.

I tried it again last night and this is what i did,  so hopefully someone might be able to find what i have done wrong hopefully.

1.  Sat scope on a perfectly flat leveled base.

2. Using the app called Syncanlnit 2.0  I set up the SynScan  as it instructed,  and all looked correct as it was suppose to be entered.

3. I then chose to begin two star alignment,  and as i am not familiar with the stars,  i used the app called Skysafari to help identify the correct stars.

4. I selected the first star,  found it in the sky and using the controls on the SynScan,  slew the scope around and centered the first star.

5.  I then went through the list to find the second star that was visible in my viewing location,  and selected it.

6.  The scope then goes off to locate this star by itself,   This time the scope did a full 360 degree circle and about another 1/4 of a turn before finally lining up on what was suppose to be the second star,  but it was way off,  almost a good 120- 180 degrees off,  ( can't remember exactally now,  but wasn't any where even close to it )

7.  So i then using the controls,  moved the scope around to where the second star was,  centred it and then the SynScan said alignment successful.

8.  I thought i would test it out to see what happens when i chose it to go and look at the moon,  being a easy target to spot.

9.  Scope slew around and finally stopped around 90 degrees or more from it.

This is pretty much what happens every time i go out and try to do a two star alignment,  sometimes it doesn't do a complete 360 degree turn before locking on what is suppose to be the second star.

I am obviously missing some important steps or more i am guessing but yet to figure out what.

 

Firstly right at the start, 

1.   Do i have to download anything into the unit before i even start?

2.   Dose the scope have to be facing anywhere in particular to start with?  I am just putting it down anywhere and then starting it up.

I have just found a page telling me it has to be facing North and the tube laying flat at 0 degrees,   but is this only for equatorial mounts,  ( the ones that have weights on them,  sorry if i have the wrong name for them)

And if so,  is facing North only if you are in the Norther Hemisphere?  as i am in the South,  should i be setting it up facing South,  or still North.

Sorry if that part sounds confusing.

I am kind of at a loss at the moment,  I am hoping someone can see what i have done or doing wrong.

Any information would be greatly appreciated.

Cheers.

 

 

 

 

 

 

[JOC]

1 hour ago, bluesilver said:

I have just found a page telling me it has to be facing North and the tube laying flat at 0 degrees

I have the same set-up as you (except for an 8" scope).  You won't do better than sysnscan init 2 - it's usually what I suggest to folks.  Do not forget the leading zeros, correct East or West and to do the date in the 'American' format as shown on the app.  Buried deep in the instruction book on a Skywatcher Dob. it does say about starting facing North and in the horizontal position.  My Dob has a scale on the side so I can do the horizontal bit.  To sort out Celestial North which is what you need I attempt to find the pole star using the mobile phone version of Stellarium and the plough (big dipper), then I drop the scope straight down to the horizontal and turn on the computer.

Despite doing this I am familiar with what you describe.  What I have found is the driven goto mount is very balance sensitive.  It is well worth doing the calibration just as the scope was sold to you.  No dew shields/heaters, no heavy EP's, no additional finder scopes, even down to using the 25mm and 10mm that the scope was sent to you with - this is worth bearing in mind as you 'drive' to targets - don't do it with heavy EP's installed and on level ground.  I also find it seems to help to use the arrow keys on the box to make the final adjustments to get the star central and to finish with a movement upwards - daft as it sounds.

When it works it is fabulous, but I continue to find it the most frustrating thing when it doesn't and even after two years ownership I still have as many bad nights as good, though it has to be said I am an infrequent user of the system so 2 years is not so many uses.  HTH

[Geoff Lister]

8 hours ago, bluesilver said:

I am trying to do the two star alignment and so far having no luck at all,  i figure i am doing something wrong or must have missed a important step somewhere.

I've got the 10" truss-tube version, with Synscan, and find the setup very easy and accurate. My UK garden is located about 51.5 degrees North of the equator. I have added a bubble level to the base, and use a small wedge, under one of the feet, to get the base level, and a hiking compass to start with the OTA facing magnetic north, and the altitude scale at zero. At the end of a session, I usually use the "PARK", Home" option in the Utilities menu, and the OTA ends up pointing roughly where I started from. I use the "Brightest Star" 2-star alignment, and have produced a table of 17 brightest stars visible from my garden, and within that table, highlighted 3, 4, or 5 of them, visible at dusk, for the middle of each month of the year, together with their rough direction and altitude, attempting to get a good pair with close to a 90 degree azimuth and 30 degree altitude separation. This gives the Synscan software the best chance of eliminating the remaining errors in my mount levelling. For the last month, or so, I have been using a manual slew to Jupiter, and then let the mount move to Arcturus (1st star), then Altair (2nd star). This gives me almost spot-on GoTo.

At power-up, the Synscan software sets the mount and motor encoder stored values to zero, and this, at least in the northern hemisphere, equates to level and North. All changes from this position rely on the mount counting clockwise or anticlockwise pulses as the motor/mount turns. I cannot see a problem with this also being true if based south of the equator. Your manual latitude and longitude inputs will have informed the Synscan software that you are in the southern hemisphere, so it should be able to calculate your local Az/Alt co-ordinates of a chosen alignment target, and, once aligned, the correct GoTo and tracking drive to the motors.

If you have a PC, I would suggest you download the free "Stellarium" planetarium program. I ran it for Sydney, Australia, and at dusk, a Brightest Star alignment starting with Jupiter (high-ish west), Arcturus ( lower north-west), and finally Rigil Kentaurus (higher south-west); should get good alignment.

I hope that this helps.

Geoff

[JOC]

23 minutes ago, Geoff Lister said:

I cannot see a problem with this also being true if based south of the equator

Ooops, I hadn't noticed this bit^^^^  the OP is in Australia - I don't know then if it starts facing North or South, but if things are exactly 180 degrees out of true maybe start facing the other way??????  the other stuff I wrote is probably all OK though.

[Geoff Lister]

1 hour ago, JOC said:

Ooops, I hadn't noticed this bit^^^^  the OP is in Australia

If you dig down deep enough, you should come to the underside of the OP's mount ⛏️ .

The Virtuoso 90's Dob. mount (tracking, but not GoTo) uses the NCP as part of its start-up sequence, and reverses the initial setup and subsequent start-up sequences if in the southern hemisphere.

However, Synscan uses the northern horizon, and not the NCP. This is independent of the latitude (except at the North Pole - ambient temperatures probably below operating range of mount), so even at the South Pole (again thermal constraints) there is a northern horizon for the encoder(s) zero datum settings. The GoTo and tracking calculations should then only need date, time, longitude and latitude to do the sums.

With Synscan, once you have entered the longitude and latitude, the handset stores it in non-volatile memory. It also remembers the date that was last entered (USA format). It is very easy, as you keep pressing "enter" as you step through all the items that you don't need to change, to forget to change the time from the start-up default of 20:00:00.

Geoff

[bluesilver]

Thanks for the replies,  appreciated.

There is a few comments in there that i am not quiet sure about though sorry.

1. The post by Joc,   you mentioned,  Do not forget the leading zeros,  not really sure what you mean by this though,  the leading zeros in which part exactly?  sorry just got a tad confused on that bit.

2.  With celestial north,  is this what you mean by true north,  not magnetic north?  If so,  i have this part worked out at least,  but i did mine on celestial south,  i am 13 degrees to the east of magnetic south if that makes any sense.

I also have the scale on the side to get it to 0,  so hopefully that part is also sorted.

3.  You also mentioned doing a calibration,  never even new this was possible or was an option,  any chance of telling how to go about doing that? ,  it would be greatly appreciated.

I have heard of it been done on equatorial mounts,  but not the altazimuth mount that the SkyWatcher Dobsonian has.

4.  When you are talking about using the arrow keys on the box,  are you talking about the hand controller?  If so,  i do remember the instructions saying to finish of with a up and sideways movement to help lock it into place so to speak.

5.  As i am in the Southern hemisphere,  am i suppose to be starting of South instead of North,  i am guessing it doesn't really matter yet as you mentioned,   it will just be 180 degrees out if it is wrong.

I can understand what you are saying Goeff  about the two systems working together,  at least a basic understanding anyway.

There is something fundamentally wrong with what i am doing at the start or somewhere.

If i can please find out some answers to the first 4 questions,  it might help me to at least get those steps true and correct and help me sorting out my dramas.

Very much appreciate all the inputs and advice,  great information here.

It is appreciated.

Cheers.

Peter.

 

 

 

 

 

[Geoff Lister]

Hello Peter,

To get the best alignment an tracking, it is best to try to get the mount level. This removes azimuth errors from the altitude axis, and vice versa.

The "start facing North" is not so important; a level mount will have sorted this out as soon as you have centred your first star. Do not get concerned about the differences between celestial and compass North.

As you select the first star, Synscan will request that you slew to an azimuth angle and altitude angle. I usually first raise the tube to the desired altitude angle using the scale on the mount, then slew in azimuth, standing behind the tube and lining it up roughly, by eye, with the target star. This usually places the target star in the field of view of the finder scope. Pressing "enter" reduces the slew rate from a maximum "9" to a more modest "4" so that you can centre in the finder and then in the eyepiece (and as you mention in '4', try to make the last movement up and right, to eliminate backlash in the drive gears). The next "enter" locks that reading.

Now, this is where the level mount scores. When you select the second star, the mount will perform an automatic slew to where it calculates the star should be. With a level mount, that calculation will be more accurate; placing the star nearer the centre of your finder.

In your '1', the longitude display requires 3 digits for the degrees, on my case "002", not just "2". The latitude degrees, and both of the minutes require 2 characters each.

In your '3', I think that JOC is mentioning that, to be able to use manual handling as well as motor/button movements, the clutch grip has to be light. I found that with a Barlow + binoviewer + 2 eyepieces, the altitude drive was slipping, and I had to add a compensating weight at the primary mirror end of the tube.

Geoff

[JOC]

7 hours ago, Geoff Lister said:

I found that with a Barlow + binoviewer + 2 eyepieces, the altitude drive was slipping, and I had to add a compensating weight at the primary mirror end of the tube.

Phew!  At least someone suffers from my same issue - it isn't just me!

Callibration = alignment = the star set-up - 2 star, 1 star, brightest star etc.  In fact have a play with brightest star I find that's pretty useful.

Celestial North - I haven't the foggiest whether that's also called true north, but it's the direction you would be in if you pointed at the Pole star and laid the telescope vertically down to the horizontal position

Leading zeros - on the Lat and Long settings - if you are say 4" 3' 1 you might need to enter 004" 03' 01

As you are somewhere interesting you will need to experiment or read the manual or ask someone else which direction you need to start of facing in, North or South, but although it's buried in the text my instructions do say start by facing North.  You already seem to understand this as you note that you are starting celestial south.  If it's not working do you have a way of fathoming celestial North to experiment with?

8 hours ago, bluesilver said:

When you are talking about using the arrow keys on the box,  are you talking about the hand controller?  If so,  i do remember the instructions saying to finish of with a up and sideways movement to help lock it into place so to speak.

I am talking about the arrow keys on the hand controller,  apparently the encoders are clever enough to take a manual push, but I think it seems to have a bit more finesse to use the arrows to finish and then you can do the final click that you describe.  In fact I have since discovered, if I remember to use them, that the movement arrows are really handy for keeping objects central if I am not using the full tracking options.

Another thing that I've noticed is if I am giving it a manual shunt it is all too easy to push and move the whole mount on the ground and not just the rotating part - this obviously throws off any alignment that you are doing.  Recently I've tried doing all the calibration movement with the arrow keys even thought let it move by itself tries my patience - I haven't fathomed how to change the speed.  My most recent acquisition is the  WiFi Dongle controller for the mount which uses a mobile phone connection and this makes controlling the telescope much easier than the handset IMO, but you do need a WiFi link or MiFi dongle to hook it up to.

[bluesilver]

Thanks again for the replies,  appreciated.

Yes,  i can get celestial North, or compass North and also the same for South.

It is interesting as i seam to be doing everything as described here,  including a level mount.

I did however notice that when i chose the first star i gives me slew coordinates,   I haven't paid much attention to them to be honest and just slewed it to the star that i picked.

I did out of interest noticed that once it said to slew something like 390 degrees or something similar,  can't be 100% sure now.

I haven't been paying attention to the slew angles that it tells me to go to for the first star,  i just figured that i would slew it straight to the star in question.

This could well be the problem then,  but then the issue is that the slew directions would not be where the star is,   this could be interesting,  will have to wait until a clear night to try that out.

 

[JOC]

It's just a thought, but is there any difference in the programming of goto units sold into the southern hemisphere and could you have got hold of a Northern hemisphere one?  I don't know if two different models exist, but someone here might.

Mind you I tried mine last night.  Whilst it got close it wasn't close enough to put objects straight into a low mag  EP and that was with the wifi dongle being used.

[bluesilver]

I don't think there are specific ones for Northern ans Southern hemisphere due to the way that you put in your coordinates,  but could be wrong.

I am interested to find out more about the coordinates that it tells you to go to for the first star,  Why would it give you coordinates to go to if you already know where the star is,  as you have to know where the star is in the first place to star the two star alignment if that makes sense.

Otherwise you would just be setting it up at the coordinates it gives you and that might not be the correct star,  just trying to think though what is going wrong.

It will be something simple,  but next time i will try as suggested and go by the coordinates it gives me and see where that ends up.

It is frustrating,  but i am sure when figured out,  it will be a good unit to use.

 

[Geoff Lister]

As far as I understand it, the handset does not need to give you the co-ordinates of the first star, it is more of a convenience. As I mentioned, above, I use it to set up the approximate altitude angle, before slewing in azimuth. It's one thing to see a star with the naked eye, but it is more challenging to get it in the field of view of the finder/eyepiece.

I too wondered about the need for a different program for the southern hemisphere, but, if I fixed on Jupiter, close to my southern horizon, and travelled due South past the equator, Jupiter would be higher, but everything else would be the same.

Geoff

[bluesilver]

Hi again,  sorry about bring this post back up again.

Just had another idea,  and this might be a basic silly question,  but i will ask anyway

With the SynScan hand held unit,  do they actually need downloading / uploading with firmware or software before you use them?

Mine currently tells me it is version 04.37.03  I haven't done anything to it like adding software or firmware,  i just figured it would of been shipped out to me all ready setup ready to go.

Any ideas on this would also be greatly appreciated.

Thanks.

 

[Geoff Lister]

There is no such thing as a silly question on this forum.

Mine came with the (latest at the time of manufacture) firmware installed. I have not touched the V3 firmware in my Skymax's handset or in the Skyliner's. I believe that the V4-standard handset was introduced because some of the components in the V3 had become obsolete, and the V4 software introduced a couple of extra bells and whistles; but no major bug fixes were required.

Geoff

[bluesilver]

Thanks for the reply,  i thought i might of solved my problems,  sadly looks like it isn't the case.

I thought that before the unit could be used,  it might of had to have some other software or firmware downloaded into the hand controller.

It appears not to be the case after all, 

So the hand set basically comes to you all ready to just plug in,  set your details and away you go pretty much then?

I am a bit reluctant yet to download anything into it unless it has to go back under a warranty claim.

 

 

[Geoff Lister]

16 minutes ago, bluesilver said:

I am a bit reluctant yet to download anything into it unless it has to go back under a warranty claim.

 

Probably wise, particularly as most PCs do not have a native serial port, so requiring a USB to serial converter dongle; some of which are not compatible with Skywatcher's software.

Geoff

[Merlin8r]

Apologies for resurrecting and old thread, but I had an almost identical problem and perhaps I can assist anyone else with a similar issue.

My azimuth was out by a good 30 degrees every time when aligning, and the further from the home position the worse it got. 
 

 After removing the plastic cover on the azimuth encoder, I noticed a spring had detached from its pin. There is a spring either side of the encoder box and they hold tension on the gears inside. When the spring came off, the encoder wheel is tilted inside and free to flap about, causing the error. Once I reconnected it, the mount is again extremely accurate.