GoTo Alignment Woes

[Brushman]

Hi All. 

Having a nightmare achieving alignment.
I've read a lot, I've tested a lot. I've sighed a lot. 

I have a 250px GoTo Skywatcher Dob. 
Motor is powered by a Baader power supply.

The problem seems to be that every time I align the first star and confirm the input into Synscan handset the motor inexplicably engages and drops by a couple of inches. (I adjust the scope back before continuing alignment) When it automatically slews to the second alignment star it seems to get the horizontal/az alignment right, but the vertical/alt is way off; in tonight's test it was off by roughly the amount it inexplicably dropped. Sometimes after alignment it intermittently shoots up and down too. Safe to say that tests after alignment are very unsuccessful - it slews but is way off targets. 

• The set up on the handset is correct - I use the 'SynScanInit 2' app to make sure everything is inputted correctly (date format, time zone, daylight saving etc)
• The scope is in a horizontal position facing Polaris before I switch on and begin alignment.
• I use the handset to navigate to the alignment stars.
• 'Brightest Star' & 'Two Star Align' has the same issue - For tonight's test I used Deneb and Capella.

I'm pulling my hair out over here - I'm hoping someone out there has experienced the same problem and can share a fix!

 

[joe aguiar]

Is that a brand new scope?

I would probably return it and get a regular dob without goto and it be half the cost and just add a rigel or telrad. 

But guess that doesn't help your issue. 

I just see soo many posts with goto not working over the years.

Joejaguar 

[Brushman]

I got it second hand, but original owner hadn't unboxed it. Had it for almost a year now and it took most that time to resolve a hardware issue. 

I'm happy with the deal I got and I want to get it working for the tracking so I can take some short exposures (I know it's not an AP scope but you can still get some good shots!)

[cletrac1922]

First of all welcome from Land Down  Under

When you siting the Dob, how are aligning north

There are 3 Norths

1. True north, which is the meridian line between north and south pole

2. Magnetic North, which is direction compass points. Depending on where you are on earths surface, magnetic north can be either east of west of true north, known as magnetic variation

3. Grid North, this is the lines on a map. Before advent of GPS, we all used to use a street directly, the top of the map street directly is north

As I am in the southern hemisphere, and setting up my EQ mount with goto, I have to face the north leg south

I use a compass to align the mount, allowing 12deg E for magnetic variation

You should be able to do the same, setting base of your Dob facing north

You using Polaris also to align the base of your Dob?

Next step is to ensure you entering your GPS location correctly into the SynScan controller, time as well

I also have the SynScan WiFi adapter, and SynScan App

Not sure what the difference between the SynScan App and the SynScanInit 2 is

Have you tried going back to the original SynScan controller, and see if you able to do a two star alignment with that

I also use a car jump start pack to power my EQ mount, which will work with your Dob as well

More stable power source

All else fails, then one night go along to your local astronomy club, guys there will only be too happy to solve your issues

My club, I am the go to person for Dob issues, including collimation 

John

 

 

 

 

[Adam1234]

I have the same scope and the vertical axis is normally always off for me too. Not always by a lot, but some nights can be worse. 

Do you use the up and right arrows when centring the alignment stars in the eyepoece? I've heard that helps.

When my alignment is off I slew to a bright star close to the object of interest, make note of how much it is off, then when trying to view my target , use the hand controller to adjust the axis by the approximate amount I had to adjust to centre the bright star, then compare what stars I can see to SkySafari or Stellarium so I can see exactly where I'm aiming at. Sometimes that can be a bit difficult when trying to find an object that hasn't got any easily distinguishable stars close by though.

Also is your mount level? That could probably affect alignment, that's probably the issue I have as my garden is not level, I need to built a small level platform or something and see if that helps.

Maybe also use a few different sources to determine your coordinates and elevation? I recently looked at a few different sources and one told me my elevation was 19m and another 12m! 

[Brushman]

6 hours ago, cletrac1922 said:

First of all welcome from Land Down  Under

When you siting the Dob, how are aligning north

There are 3 Norths

1. True north, which is the meridian line between north and south pole

2. Magnetic North, which is direction compass points. Depending on where you are on earths surface, magnetic north can be either east of west of true north, known as magnetic variation

3. Grid North, this is the lines on a map. Before advent of GPS, we all used to use a street directly, the top of the map street directly is north

As I am in the southern hemisphere, and setting up my EQ mount with goto, I have to face the north leg south

I use a compass to align the mount, allowing 12deg E for magnetic variation

You should be able to do the same, setting base of your Dob facing north

You using Polaris also to align the base of your Dob?

Next step is to ensure you entering your GPS location correctly into the SynScan controller, time as well

I also have the SynScan WiFi adapter, and SynScan App

Not sure what the difference between the SynScan App and the SynScanInit 2 is

Have you tried going back to the original SynScan controller, and see if you able to do a two star alignment with that

I also use a car jump start pack to power my EQ mount, which will work with your Dob as well

More stable power source

All else fails, then one night go along to your local astronomy club, guys there will only be too happy to solve your issues

My club, I am the go to person for Dob issues, including collimation 

John

Hey John,

The base is facing Polaris with the scope in horizontal position - that's all the aligning I do before switching the GoTo on. 

Just to also clarify, there is no EQ mount in place here. Just the GoTo which I control via the original handset - I don't have the SynScan wifi.

The other app I mentioned just confirms my gps and elevation - I'm confident this is all accurate. 

Regarding the power source I also have a power tank but I experience the same issue. 

If I have you stumped then your advice of heading to the local astro club is probably valid here, I'm long overdue getting involved.

Edited December 12, 2019 by Brushman

[Steve Clay]

Have you checked to see if your mount has the latest firmware for the motor controllers?

Have you tried altering the backlash settings in the handset.

Steve

 

[Brushman]

26 minutes ago, Adam1234 said:

I have the same scope and the vertical axis is normally always off for me too. Not always by a lot, but some nights can be worse. 

Do you use the up and right arrows when centring the alignment stars in the eyepoece? I've heard that helps.

When my alignment is off I slew to a bright star close to the object of interest, make note of how much it is off, then when trying to view my target , use the hand controller to adjust the axis by the approximate amount I had to adjust to centre the bright star, then compare what stars I can see to SkySafari or Stellarium so I can see exactly where I'm aiming at. Sometimes that can be a bit difficult when trying to find an object that hasn't got any easily distinguishable stars close by though.

Also is your mount level? That could probably affect alignment, that's probably the issue I have as my garden is not level, I need to built a small level platform or something and see if that helps.

Maybe also use a few different sources to determine your coordinates and elevation? I recently looked at a few different sources and one told me my elevation was 19m and another 12m! 

Hey Adam, thanks for response.

Do you mean using the up and right arrows only? ...so in some cases slewing the long way around. (I haven't tried this yet)

Mount is very close to level - I'm not sure that this is what would cause the motor to engage after alignment and do its own thing though. 

My coordinates seem consistent across multiple sources, but my elevation does not - off by 25M according to a few other sources - I'll have to sort this and report back.


One question for you though - does your scope automatically move around on its vertical access during or after alignment? 

[happy-kat]

The up and right arrows only need to be used for the last movements when centering on the chosen alignment stars.

[Brushman]

35 minutes ago, Steve Clay said:

Have you checked to see if your mount has the latest firmware for the motor controllers?

Have you tried altering the backlash settings in the handset.

Steve

 

I'm on SynScan 4.31.05, I believe there is 4.31.10 as of this month to update to (and I will), but I was experiencing this problem before then too.

I've not heard of backlash settings before... a quick read up sounds like this is just for the speed/lag when controlling the slew - would this have any hand in automatically moving the motor without any input?

[Steve Clay]

possibly. you could change the settings to zero and see what happens.

Also are your clutches nice and tight. I don't have this mount but found balance and clutch tightness important with the AZGTI, where the alt was always slipping.

Steve

[masjstovel]

How do you power the mount? You sure you feed it with sufficient amount of ampere?

[Brushman]

21 minutes ago, Steve Clay said:

possibly. you could change the settings to zero and see what happens.

Also are your clutches nice and tight. I don't have this mount but found balance and clutch tightness important with the AZGTI, where the alt was always slipping.

Steve

I'll give it a try and see - thanks for the suggestion!

Yeah, its as tight as it will go - the unwanted movement is motorised)

[Brushman]

19 minutes ago, masjstovel said:

How do you power the mount? You sure you feed it with sufficient amount of ampere?

Baader power supply plugged into extension cable. I have also used a celestron powertank with the same results. 

[masjstovel]

Ok, I dont know what your mount requires and all, but i had simular symptoms as you and that was that i had a 1.5A power supply and my mount needed 2.5A.

[ollypenrice]

 

14 hours ago, Brushman said:

Hi All. 

Having a nightmare achieving alignment.
I've read a lot, I've tested a lot. I've sighed a lot. 

I have a 250px GoTo Skywatcher Dob. 
Motor is powered by a Baader power supply.

The problem seems to be that every time I align the first star and confirm the input into Synscan handset the motor inexplicably engages and drops by a couple of inches. (I adjust the scope back before continuing alignment) When it automatically slews to the second alignment star it seems to get the horizontal/az alignment right, but the vertical/alt is way off; in tonight's test it was off by roughly the amount it inexplicably dropped. Sometimes after alignment it intermittently shoots up and down too. Safe to say that tests after alignment are very unsuccessful - it slews but is way off targets. 

• The set up on the handset is correct - I use the 'SynScanInit 2' app to make sure everything is inputted correctly (date format, time zone, daylight saving etc)
• The scope is in a horizontal position facing Polaris before I switch on and begin alignment.
• I use the handset to navigate to the alignment stars.
• 'Brightest Star' & 'Two Star Align' has the same issue - For tonight's test I used Deneb and Capella.

I'm pulling my hair out over here - I'm hoping someone out there has experienced the same problem and can share a fix!

 

Have you tried not adjusting it back after this happens? Just proceed to the next alignment star?

Olly

[Brushman]

Olly, yes in my first attempts that is what I'd do, but to no avail.

So in an attempt to fix I'd readjust to make sure the alignment continues from the point at which the star is centred in the eyepiece.

[banjaxed]

1 hour ago, happy-kat said:

The up and right arrows only need to be used for the last movements when centering on the chosen alignment stars.

I was aware of this procedure with the WiFi app but not the handset, thanks for the heads up.

[Adam1234]

3 hours ago, Brushman said:

Hey Adam, thanks for response.

Do you mean using the up and right arrows only? ...so in some cases slewing the long way around. (I haven't tried this yet)

Mount is very close to level - I'm not sure that this is what would cause the motor to engage after alignment and do its own thing though. 

My coordinates seem consistent across multiple sources, but my elevation does not - off by 25M according to a few other sources - I'll have to sort this and report back.


One question for you though - does your scope automatically move around on its vertical access during or after alignment? 

As some of the other guys clarified, the up and right arrows just for the final centering of the star. You should be able to use any of the arrows for getting the approximate position. 

Just had a thought regarding elevation being different from different sources - could try inputting different elevations and seeing how that affect alignment, I may try that myself and see if has any effect.

Regarding the automatically moving around on its vertical axis - do you mean it slews close to the star, then seems to move around as though it's going away from the star, then move slowly back towards it? I think mine does that, I think I read somewhere that that is supposed to do that? (if we are talking about the same thing that is)

[Geoff Lister]

I had 2 problems with my 250PX.

(1) I found that my OTA was front-heavy, particularly if I used my binoviewer, DSLR or 2" 56mm Plossl eyepiece. The altitude motor would turn but the OTA would not elevate. I tightened, slightly, the altitude axis nyloc nut, and added a weight near the primary mirror end of the main tube. Problem solved.

(2) I also had problems getting the handset to control the fine adjustments in azimuth; so I could not get the alignment star in the centre of the FOV. The fault was caused by one of the ribbon cable connectors, inside the azimuth box housing on the base, not being fully seated on its pins on the azimuth control board. The fault was difficult to locate, as the dodgy connection was under the board, and I had to unscrew the board to find it. The ribbon cables seem to be very short, because each has an added ferrite ring, probably as a post-design fix to get it to pass regulatory RF emissions or susceptibility tests. Again, problem solved.

Since solving these 2 problems, I have had excellent GoTo and tracking accuracy. I often do a Brightest Star alignment at dusk, go in for tea and a warm-up, and return when it is properly dark, with the second alignment star close to the centre of a 25mm eyepiece.

I added a bubble level to the base, adjacent to the azimuth control box. I rotate the bottom of the base until the bubble is pointing in a direction mid-way between 2 of the feet, and, using a small wedge, lift the third foot until the bubble is centred. I power-up with the altitude scale at zero and the OTA pointing roughly north.

I power my Skyliner with a 12V 2A plug-top PSU, (similar to the Baader one shown earlier), but originally provided to power an Ethernet switch. I have also used other 12V 2A plug-top supplies, often used to power the 12V LED flexible lighting strips. Below, are some average current measurements that I made on various mounts. Peak acceleration currents may be a little higher, but I have not noticed any current-limit trip problems.

Geoff

[happy-kat]

Reading the last post your next easy try is to look at weight distribution and add a little weight to the primary mirror end of the tube. My little virtuoso mount is very weight sensitive on the altitude axis and slips of I've not got it right.

[Brushman]

58 minutes ago, happy-kat said:

Reading the last post your next easy try is to look at weight distribution and add a little weight to the primary mirror end of the tube. My little virtuoso mount is very weight sensitive on the altitude axis and slips of I've not got it right.

Hmm, I don't think it's that though as the movement is motorised 🤔

I'm going to take a video of it I think and post - might give people a better idea of what's going on. 

[westmarch]

Don’t know your scope but if you run out of options:

check the date format entry, is it day or month first?
 

check the gps format, is it d:m:s Or decimal degrees (DD)?

Do a hard reset. 
 

Good Luck. 🙄
 

John

[happy-kat]

The virtuoso mount is motorised and I use a synscan handset with it plus a 12v liFePo4 battery and it slips if the weight is not right for the altitude axis.

I need it front heavy for the West and rear heavy for the East.