Skywatcher Synscan 2 star align query.

[squeaky]

Sorry Squeaky - you're right - I double checked myself and realised when I posted I was reading from the wrong manual. The AZ Synscan Goto doesn't have 3-star align - just Brightest star and Two Star align. Three Star is in the EQ manual so please accept my apologies for confusing you.

Unfortunately I can't edit posts for some reason so my mistake is there for all to see lol (d'ohhh). Anyway - stick to a quarter of the sky as I mentioned and the "finishing" movements as described and two star align will still do the biz for you. Use the PAE (on either handsets) to refine accuracy when moving to other parts of the sky. It will track an object for a good 30 mins before drift sets in.

Phew! I thought I was going nuts or had made a serious mistake somewhere!

Last time out - even with PAE I was seeing the images drift between each take (approx one minute apart) by two to three "star diameters".

I've found that there is a definite delay on my beast before the mount starts to move when moving at speed #1. That's if I press and hold a left or right arrow key. If I just do very short "blips" of a key it, doesn't seem to matter how many I do, the mount doesn't move. I'm watching the base with a DTI and can easily spot 0.00025" of travel (or not, as the case may be). So to all intents and purposes - while alignment and targeting were pretty close - I don't think I was actually tracking.

I "think"

Hmmm.... from memory...

Since my FOV for the camera with 2x Barlow (to get a focus at Prime) is approx 20 arc mins - I reckon that the drift in AZ I see between subs one minute apart is in the region of 20 arc secs.

The sky rotates at 15 deg per hour which is 1 deg per 4 mins which would be 15 arc mins per minute. So I must actually be tracking then! Just not tracking correctly.

[squeaky]

Hi,

I have the 250px goto and this set up works for me:

1. Make sure it's on flat ground

2. Turn on and enter data, time and location etc

3. Select two star alignment, this is my best choice as I have limited views and I normally find the 2nd star is out of view

4. Select a star and use the finder to get the star into view - either manually or by nudging the handset

5. Use my a 16mm or 24mm ep to centre the star, reduce to a 6.4mm to get it right in the centre - this really helps the goto to get things in the FOV when viewing later

6. Choose the second star (I have attached the list and charts for the 3.08 version), it's rarely in the FOV so I need to nudge the scope.

7. Repeat steps 4 and 5

8. Start viewing

Hope this helps, good viewing.

Paul

Hi Paul,

With the exception, it seems, of using Polaris from the alignment list - I've got that procedure off pat. Honest

I use a builder's level to ensure that my base is completely level and I also use it to ensure that my OTA is horizontal when I power on.

I use my camera's live view via Backyard EOS to centre my target. As I've said, my FOV is approx 20 arc mins and I can use the 5x zoom to ensure that my target star is exactly on the centre point of the graticule. That seems like it should be pretty darn accurate to me (?).

Got the list and star charts printed and laminated, thanks

[squeaky]

Being about a degree wrong would make sense, that is the difference between Polaris and the earths axis. Which since you appear to not be using a polar scope would match up.

Alignment using Polaris is never a good idea, something up there is taken a "0" and Polaris is usually it, any division by 0 in whatever algorithm used causes problems. Usually manufacturers advise against it and I am surprised that Skywatcher do not.

Forget using a compass.

The whole setup sounds as if it is intended for visual and for visual I would expect some drift. It just does not tend to be rigorous enough, mainly because it doesn't matter as much. And you may not like it but you have a classic visual system - large, heavy Alt/Az dobsonian mounted scope.

When using an equitorial mount the set up for imaging is quite time consuming. Then do not expect an exposure time of more then 60 seconds before drift takes effect. Using an Alt/Az based mount the effect has to be worse as you will have field rotation included in the mix.

Another point is that goto is used to locate an object, expect to have to centre anything once it is located. To track accurately imagers use a guide scope and system. If goto was good enough they would not spend the money on a second scope, camera and laptop after all.

The 300P is certainly not lightweight, drive accuracy has to be a problem, simply too much weight for the drive train to accurately control. You cannot alter the balance either and what the balance set up for a visual dobsonian will be different to that for imaging. The 300P will also have a reasonable focal length, (NOT f number) and the longer that gets the greater any tracking errors are amplified. Imagers use short focal length scopes for a reason.

Yep. I should have bought an equatorial mount. So I'm saving up for one. If I live on beans on toast for a year I might just about do it by next October

[brantuk]

Yeah - it was a long day yesterday as you mentioned earlier lol

I don't use dobs for imaging - only for observing - I tried to capure saturn once in the 300P with a dslr and the accuracy just wasn't enough at the mag I was using. Yes - there is a small delay when slewing or using goto before you see any movement. Like it's trying to "wind up" before actually moving. It's the same on all I believe - even my eq mount. You can of course choose the slew rate to speed up arrow key depresions - but you'l have to slow them down again for centering up. Tracking is barely perceptible - I find I only notice it in the eyepiece if the alignment is off and I get a bit of drift.

A point worth mentioning - there is some slack in the AZ drive motor on the upgraded auto's. It takes the gear a short while to engage positively with the turntable gear - there's nothing you can do about that short of getting the upgraded motors that come on the newer mounts. I had mine to bits to discover this. I suspect the Alt motor is the same though I didn't disassemble that one.

[squeaky]

I've just been trying dialing in some backlash on AZ and it doesn't appear to make any difference. I "think" the clutch friction etc are all OK now - only an imaging session will tell me - but I can't seem to eliminate that last bit of delay.

So it very probably is in my motors. But then again - I bought this in April (ordered in March) so should it have the upgraded motors in it? Mine's the one where they changed back from the blue tubes to the black ones again.

[brantuk]

If it was bought brand new as a Goto (ie not handset upgraded auto like mine) then it will allmost certainly have the newer motors which are more beefy and accurate. Mine's two and a half yrs old - purchased before the better motors came out

[squeaky]

OK. So I must have the upgraded motors. Hmmm...

[hemihaggis1]

squeky , brant has a dob , i have dob , with syn scan , i know other people who have dobs and 127 maks , none of them are eq`s they all have identical alignment proceduers ,you will have an a to z synscan handset .... you have the choice of two or three star alignment , they are all the same .... how long have you had the scope for ?? do you have the correct hand set ect ??

[squeaky]

squeky , brant has a dob , i have dob , with syn scan , i know other people who have dobs and 127 maks , none of them are eq`s they all have identical alignment proceduers ,you will have an a to z synscan handset .... you have the choice of two or three star alignment , they are all the same .... how long have you had the scope for ?? do you have the correct hand set ect ??

Leesten vairy cairefully - I weel say thees ohnly once....

I do NOT have THREE Star Alignment available. FULL STOP.

[squeaky]

See also This Post

[Cjg]

I have the AZ4 SynScan goto and there is no 3 star alignment just brightest star and two star.

The one thing that I have found that has caused more "errors" with alignment has been the power supply.

Wonder whether it's also worth running your kit from a different source just to see if that makes a difference too? Perhaps the mains?

And as you live in Sunny Suffolk, then perhaps worthwhile one Friday bringing it along to Seething and NAS? Plenty of experienced users to assist.

Good luck,

Chrs

[squeaky]

Yes, I can either use a 74AH 12v DC battery, or a 10A 12v DC power supply. That's a PSU from an old computer. It doesn't seem to make any difference.

Seething and NAS ... I'll give it serious thought, thanks

[attis25]

I have just bought a Skywatcher 127 Mak with Synscan and am having most of the problems being discussed in this thread and the postings have been really helpful. I live on Crete so I’m very much on my own as far as getting the telescope to work. I have the latest version of the software in the handset and there is definitely no mention of 3 star alignment. There is no documentation on the OTA. I have had to print out the technical spec from the adverts on the web. The Synscan manual looks comprehensive at first glance but there have been a lot of “What do I do now?” moments. When I eventually did get the alignment to work after a couple of frustrating evenings I found Arcturus and Antares the easiest to align on. Incidentally does the tracking only work after you have been through the set up routine? I used the navigation keys to home in on Saturn then went straight to “Tracking” in the setup menu but the tracking didn’t work.

Cheers

Derek

[squeaky]

As far as I'm aware - because the manual doesn't really make anything clear - once you have done a star alignment you do not need to do anything else. Just pick your target and enjoy.

The Auto-tracking on the setup menu is for use if you do NOT do a star align, so trying to use auto-tracking after aligning is probably not a good idea.

I "think"

[Cjg]

As far as I'm aware - because the manual doesn't really make anything clear - once you have done a star alignment you do not need to do anything else. Just pick your target and enjoy.

The Auto-tracking on the setup menu is for use if you do NOT do a star align, so trying to use auto-tracking after aligning is probably not a good idea.

I "think"

Sqeaky, I think that's incorrect. My tracking only works accurately after I've done a successful alignment.

Attis25, just back from Samos, you have superb skies. Take your time to get the scope level, and get a decent power supply; the aa batteries will not last long, and nicads will give you alignment errors. Best is a decent battery or if you are close to the mains supply?

There is on the Ovl ( skywatcher UK distributer ) site a PDF of the instructions. Will try and find the URL.

Chris

[Cornelius Varley]

When setting up my scope (see my sig) I first find Polaris and centre it in my FOV - then drive the scope down with the down arrow until the OTA is level. Then I turn the power off.

This so that my scope is pointed North and is level as it says in my book that it should be before starting a 2 star alignment.

So now I power up and choose Polaris as my first alignment star.

Since I'll be doing imaging and the weight of my DSLR affects things I align Polaris in the centre of the graticule available via Backyard EOS. Since my FOV is approximately 20 arc minutes and I can use a five times zoom - it means that I can be very accurate here.

At the moment, at between 9 and 10 pm I use Altair as my second alignment star because it's pretty much due South and is a nice angle above the horizon.

All with me so far?

The query is this... after centring Altair in my finderscope because it's usually off target by around 1 deg AZ and about 2/3 deg ALT.... it drifts. A lot. It appears for all the world as if the scope is not tracking Altair at all. It drifts a fair amount in AZ and a smaller amount in Alt - going up and right. So I have to offset in my view continuously. I've tried doing this for five minutes and more in the hopes that it might be some sort of settling or backlash issue but it never does settle. So I have to offset it in such away that it will shortly drift over the exact centre of the graticule and then hit ENTER

After that I get the "Alignment successful" message and Altair will then "stay put" - albeit usually a little off centre. If I then target Altair as a "Named Star" it will re-centre reasonably close to where it was.

But is this apparent non-tracking drift of the second alignment star normal?

If you have a goto mount you do not need to level the telescope and point it north, the mount does need to be level. Also there is no need to switch off and then on again - this is just for the basic auto-track az mounts.

The AZ-GOTO mounts have two alignment methods, brightest star and two star. For the two star alignment it is preferable to use two stars that are equally spaced either side of the meridan, this will give you the most accurate alignment. Polaris is probably a bad choice of star because it is too close to the NCP .

Peter

[squeaky]

Er... yes... as I said - "once you have done an alignment"

[attis25]

Sqeaky, I think that's incorrect. My tracking only works accurately after I've done a successful alignment.

Attis25, just back from Samos, you have superb skies. Take your time to get the scope level, and get a decent power supply; the aa batteries will not last long, and nicads will give you alignment errors. Best is a decent battery or if you are close to the mains supply?

There is on the Ovl ( skywatcher UK distributer ) site a PDF of the instructions. Will try and find the URL.

Chris

[attis25]

Thanks for the information. I seem to have done something wrong trying to insert a quote from Squeaky about the batteries. But I realised when I first set up the telescope that the feeble battery pack was the weakest link in the setup. I've had to jiggle the wires in the battery block about quite often just to get power to the handset but I didn't realise that the AA batteries could be affecting the aligning. A power pack is obviously my next purchase.

Derek

[wilso31]

Hi All

I seem to be having problems inputting my longtitude latitude into my synscan handset.

my is lattitude 53.3646778

logitude -1.35628663

how would i input this in the handset would it be 001.35 and 53.36?

[squeaky]

You also need to ensure that you change (if needed) N or S, and E or W.

I'd be inclined to round up the longitude to 1.36

[Cornelius Varley]

Hi All

I seem to be having problems inputting my longtitude latitude into my synscan handset.

my is lattitude 53.3646778

logitude -1.35628663

how would i input this in the handset would it be 001.35 and 53.36?

The synscan handset requires the coordinates in the format of degrees and minutes. Your correct coordinates should be 001 21W, 53 22N

Peter

[wilso31]

The synscan handset requires the coordinates in the format of degrees and minutes. Your correct coordinates should be 001 21W, 53 22N

Peter

those coordinates are different to what i originally posted is that correct?

[Teslar]

I used my Az4 mount the other night for the first time. It was a little strange in that it differs to what I'm used to with my EQ6 however I found the Az4 to be surprisingly accurate once aligned and taking backlash into account by centering stars with an up and right as viewed movement.

I did find it difficult to fine tune the second star in alignment mode because the mount kept wanting to move up and right after every adjustment. I soon found that I needed to move the mount well off to the left and down (as viewed) let it settle it's movement routine then approach the star up and to the right as viewed. Provided I didn't overshoot this worked well. If I did overshoot I had to drag the scope well off again and re approach. Once aligned I used goto to find and object the held down escape to re centre the object and everything from then was good

I'm going to tinker with backlash settings to see if I can make the alignment movements more responsive but the method I used above did work well and was repeatable in that after viewing a number of objects I could return to any point and it was within the FOV

[Cornelius Varley]

those coordinates are different to what i originally posted is that correct?

Yes. The coordinates you gave were in decimal format, synscan requires them in degrees and minutes.