SynScan Goto questions

[NigelCampbell]

Hi all,

After 3 weeks of constant cloud cover I finally got to use my Skywatcher 150P Goto.

Though I did get to see some good targets - Saturn of course and M3 (I was South facing) I had some issues getting the alignment to work on the Synscan and had to manually hunt around for targets.

Does anyone have any helpful tips on how to ensure a good 2 star alignment (hoping to try again Friday night so Arcturus and Vega would be my 2 stars).

First question:

Choosing Arcturus: Handset gives me coordinates to slew to but there is no readout when I slew the scope - is there supposed to be? (obviously I know where Arcturus is but why give coordinates if you cant follow them?)

Once that was done and centred it slewed to Vega but was off by a reasonable margin. I centred and it said alignment done.

I chose Saturn as the first easy target but it was off by a similar margin to Vega.

Second Question: How critical is the centreing of the target - exact centre? would this be better with the 10mm or 25mm eyepiece in?

Third Question: My lat and long were incorrect (but only very slightly) would this account for the problems?

Finally: What else should I do to get good alignment - what doesn't the manual tell me? Any and all tips very welcome.

Despite all of this it was a brilliant first experience and I am totally hooked!

[Demonperformer]

Can only really comment on question 2:

I tend to align using firstly a 32mm to get it close, then change to my 12mm reticle, so that it gets it smack on. This second part of the procedure I have only started to do recently, but it has sure improved the result.

HTH

[Donkeiller]

Nigel, welcome to the Forum. Your Synscan mount can be very accurate if setup correctly;

1) is it level?

2) correctly Polar aligned?

3) correct date format?

4) Correct position format- as correct as you can get it.- I use my car's Tom-Tom (sat nav), or Google Earth for lat/long.

5) Centreing is needs to be done accurately. I use a eyepiece to give about x100 and defocus the star so it fills much of the F.O.V. that way you can judge whether it is central much better.

6) Don't expect the slew to the second alignment star to be accurate- you will have to adjust it manually and centre as above.

7) Make sure your power supply is adequate. I use a 17AH gel battery.

If you tick all these boxes you will get accurate gotos- they should always be in the FOV of your 25mm. You can manually centre them and then activate "auto-tracking" and view without further adjustment for a good 30 minutes.

[Parallax]

What the manual doesn't tell you -

When the mount has slewed to the first alignment star, instead of centreing it with the hand controller, loosen off the clutches and manually push the scope until the star is centred. It's a bit of a fiddle but this will "fool" the mount into thinking that it has got the 1st star bang on. (Fine adjustment can be made with the HC). Slew to the 2nd alignment star and centre it using the HC. Try and use the 10mm ep if you can.

The more accurate your lat and long, the better.

This assumes it is an EQ mount? Not sure about Alt/Az.

HTH

Steve

[NigelCampbell]

Sorry - My Bad should have pointed out that its an AZ mount so no Polar align necessary (also no clutches to loosen)

[Demonperformer]

In that case, a level tripod is a definite 'must'

[foundaplanet]

I discovered that mine performs much more accurately when the scope is balanced properly. If thats of any use to you...

[ronin]

Level the tripod and the scope.

Point the tube North and check that it is level.

Always a good starting place even if they don't need it.

Data, Lat and Long entered I think as Long then Lat.

Long will be be either East/West or +/-

Think they are East/West but if +/- then anything West is -ve.

The time zone is 00, this can be missed and they default to a timezone in the US. They then get damn confused even if the Longitude entered is correct, from which it could determine the timezone.

Date is US format but I think make it pretty obvious, think it comes up as mm/dd/yyyy. DST is On or Yes.

The point is that they need all the information and the more accurate the data and set up better.

Centre with the 25mm and then switch to the 10mm if enough time. I have a feeling that you may have to complete the alignment within a certain length of time. If you take too long then the initial position could be out of date as far as the scope is concerned.

No need to rush but taking 10 minutes may render the whole thing no matter how well done invalid. Realise that in 4 minutes the sky has moved by 1 degree, may seem small but the moon is 1/4 degree (I think).

[Cornelius Varley]

Slightly off the thread here Nigel, but your sig says you have a SW150P Goto. Do you mean a SW130P AZ-goto?. The SW150 ota is a bit big for the AZ mount.

Peter

[Demonperformer]

the moon is 1/4 degree (I think).

Minor point ... actually about 1/2 degree

[NigelCampbell]

Those are excellent tips. I shall try them all tomorrow night and let you know how I get on.

[NigelCampbell]

Slightly off the thread here Nigel, but your sig says you have a SW150P Goto. Do you mean a SW130P AZ-goto?. The SW150 ota is a bit big for the AZ mount.

Peter

You are correct Peter, I shall amend my sig

[ronin]

Never could remember the diameter of the moon, really should. Knew it was either 1/4 or 1/2.

Lot easier if given the dia in km and the distance in km. Maths is easier then memory.

Main thing about a goto is simply getting everything right and there is always some odd little bit hidden somewhere.

I had one at a public evening a few months back. For some odd reason it decided it was on an eq mount not an alt/az. I have never had it on an eq. I could simply not locate the option to change the mount. Eventually I packed it away, took it home, read the manual several times and eventually gave up and cleared everything out and started again.

What happens is when you enter information some of it is simply not redisplayed for changing. So if that is the bit you don't have right, thinking time zone, you find you cannot change it easily afterwards. That is really why I say make sure everything is correct, assume nothing.

I have also set them up indoors and used a planesphere to say what stars should be roughly where. Just practise but warm, lots of light, chairs to sit in when in a state of despair, coffee at hand. Oh yes, some of he errors you can/will make can be plain embarassing. As I said I couldn't tell my own scope to change mounts.

[DoctorD]

Hi

It's also important to approach each alignment star in a manner consistent with the way the GOTO works.

I found an article on the Nextstar mount which suggested always approaching from the left and below - that is using the right and up arrow on the handset.

I have the Synscan AZ and have watched it approach a target this way.

This removes any backlash from the system (or rather ensures it's taken up to the same extent - my mount has about 7 arc minutes of backash in both directions).

The more accurately you centre the alignment stars the better - as Demonperformer says start with a wide field eyepiece and work up to your highest magnification.

The manual state a pointing accuracy of upto 10 arc minutes -

You may have to find the object in a

Wide field eyepiece and re-centre as appropriate even with the best alignment.

There are other threads about the lack of rigidity in the Synscan AZ tripod which also results in pointing inaccuracies. These can easily be fixed using epoxy glue and not extending the tripod fully.

Hope this helps.

Paul

[DoctorD]

Just another point - I do not think it matters how long you take to align the second star - the mount will calculate the position based on the actual time you centre the star and build it's map of the sky from this.

I use Polaris for the first star - point the scope north and set the altitude to 53 degrees (mine has a rough scale stuck to the mount) - the scope will not slew to the first star as it has no reference to work from unlike a EQ mount that does.

The more level the mount the more

likley the second star will be in the field of view, however the mount needs at least two points of reference. Single star alignment relies on a level mount but much prefer 2 star alignment.

You can also use the PAE function to improve GOTO accuracy on any particular part of the sky - simply select a bright star near the object you are looking for and hold down the ESC key for two seconds - recenter the star using the arrow keys and press enter. Then GOTO the desired object. This improves the mounts model of the sky.

Clear skies

Paul

[NigelCampbell]

This is really excellent advice. I shall persevere. (Never met a piece of technology yet that couldn't eventually master).

[ronin]

I do not think it matters how long you take to align the second star - the mount will calculate the position based on the actual time you centre the star and build it's map of the sky from this.

Hate to disagree but I have no reason to believe that whoever wrote the software took this into account. The original intention would have been to write software and as quickly as possible and at minimum cost. To do the above the scope needs to know what changes to apply to the first alignmnet star position, as the scope is not aligned that compensation is not yet determined and so cannot be applied.

It would be nice if it was in there but commerically I would doubt that the inclusion of such a feature was considered. It is a lot easier to check a timer/counter and if X time has elapsed simply invalidate the alignment.

I work on safety critical software (cost £millions) and if our systems are not set up quick enough it is a simple check of has T time elapsed if Yes then setup = Invalid, System halt. Very easy, very cheap, no problem.

The software is not written by astronomers and is written to minimum cost. An algorithm to compensate for the user taking a long time costs Synta money. You might put it in and I might as well, but not I suspect whoever it was contracted out to. If I were doing alignment software I would have a start position of Polaris as an option. Easy for the Northern Hemisphere astronomers.

One other thing for Nigel, may be good idea to clear everything, Reset the handset. If cleared the handset tends to ask for what it needs, so you get the chance to enter something sensible/correct.

[Fumangord]

Hi Nigel,

I hope you are not experiencing a problem similar to mine. my new synscan goto mount will not align period..!

I am currently in discussion with my supplier but not received a resolution as yet.

It might not be the same glitch as yours so don't get too worried. My mount allows me to align the first star and it even slews to the general vicinity of the second star, that's where it all goes wrong, as the mount slows down to centre on the second star the HC suddenly resets to 000 and the mount slews off to somewhere else entirely. I suspect this is a problem with the actual mount controller, not the HC itself but the electronics inside the mount. The HC would appear to be receiving a miss count from the stepper motor control. As I said no answer as yet, so ATM I am having to use the mount in manual mode only and that is a nuisance as the whole point was to have some tracking ability.

Good luck with yours.

Gord.

[NigelCampbell]

That's not the problem Gord. That sounds like it's seriously Banjaxed. Hope you get it sorted / replaced soon.

[Odd Dob]

What the manual doesn't tell you -

When the mount has slewed to the first alignment star, instead of centreing it with the hand controller, loosen off the clutches and manually push the scope until the star is centred. It's a bit of a fiddle but this will "fool" the mount into thinking that it has got the 1st star bang on. (Fine adjustment can be made with the HC). Slew to the 2nd alignment star and centre it using the HC.

Steve

What's the logic in that then?

Fwiw, I've got a HEQ5 and just use a one star align. Works fine for me!

[sxinias]

A lot of excellent suggestions and a few that don't apply to the SynScan AZ mount.

MOST IMPORTANT: The tripod is a major source of goto error. Watch your bubble level and do a 360 degree azimuth slew. If the bubble follows the tube then your tripod is flexing. Even though the bubble may stay near and inside the centering circle the flexure is sufficient to mess up the alignment and gotos. Tighten all the nuts and bolts on the tripod. The other source of movement on the tripod is rotational movement of the tripod legs in the tripod head leg sockets. This movement is very slight but gets magnified. Solution ... I epoxied my legs to the sockets but before that slipped some toothpicks in the very tiny crack between the legs and sockets. Shirt collar stays will work too. Always install the eyepiece tray on the leg braces to increase rigidity.

The mount is not really fussy about being level ... eyeball will do just fine. Also, as stated in the manual, the orientation of the telescope at power-on is not important regarding alignment but .... on the other hand as someone said, it eases the process. People have their own ways for aligning the mount. I like to park my scope after using it. The next usage I eyeball level the scope and point it north when I power up and by pass alignment. I then do a goto to Polaris, switch to the alignment mode and use it as the first alignment star. Any other star would work, I just use Polaris. Makes the alignment process a little easier. I've never had any success with the SynScan bright star align and use the two star alignment

Polaris makes an excellent first alignment star; stars near the zenith are poor choices as alignment stars

Centering the alignment stars is important ... defocus and use a higher power eyepiece than a 25 mm ... 9 to 12 mm works

Overall time for the alignment: Don't know but often wondered.

Weight. Not a problem with the SkyWatcher AZ mount. It is a rugged workhorse of a mount and can carry 12 pound (5.5kg) loads all night with no problem. I use mine for my 8 inch LX200 OTA and a C6S OTA with a Canon DSLR attached with no difficulties at all. The trick is to keep everything balanced. Been doing this for over two years now. My only issue with the 8 inch SCT is tube strike at altitude greater than 82 degrees.

Direction of the last azimuth and altitude slews during the alignment process. I find that the gear slop in the NexStar 4/5 SE mount is an order of magnitude greater than that in the SkyWatcher SynScan AZ mount. The direction of the last azimuth and altitude movement with the SE mount is important because of this gear slop. I have never noticed the number, direction, or order of slews made to align a star to be a factor with the SynScan AZ mount. The altitude clutch on the SynScan AZ mount is much stronger than the SE mount. I have never attempted to put the loads on my SE mount that I put on my SynScan AZ mount as I don't think the SE mount can handle them.