EQ-5 SynScan Star Alignment Help

[trevboyd]

Hi all

I've got a new CG-5 with the EQ-5 SynScan upgrade fitted. I'm very pleased with the mount and motors - a joy to use when observing the moon at high power.

I'm having big problems trying to perform a star align with the SynScan though.

The steps I've followed so far are:

• 
  [li]Polar align the mount using the built in polar scope- I think this is pretty good, at least as well as I've done in the past with my EQ-5[/li]
  [li]Mount the scope and weights[/li]
  [li]Set the RA and Dec so that the weights are pointing north and down and the scope is pointing north[/li]
  [li]Powered on the SynScan, entered my location and time[/li]
  [li]Selected to perform a 2 or 3 star align (I've tried both)[/li]
  [li]Selected Capella as the 1st star, as its nice and easy to spot above the house[/li]
  [li]The scope starts slewing, but it ends up nowhere near Capella - further to the left and down, near Mars[/li]
  [li]I centre Capella in the eyepiece and select Mizar as the 2nd star[/li]
  [li]The scope starts slewing, but it ends up nowhere near Mizar[/li]
  [li]I centre Mizar in the eyepiece[/li]
  [li]SynScan says either "Alignment Poor" or "Alignment Failed"[/li]
  [li]If it says "Alignment Poor", I try using the GOTO to find something (eg the Moon)[/li]
  [li]Scope slews in general direction of the target, but ends up some way off target[/li]
  

I've tried this lots of times, and am always careful to power on with the scope in the right "park" position (as I understand it), but with the same results. What am I doing wrong?! Help!

Trev

[cygnusx1]

Ensure the 2 stars are on opposite sides of the meridian, or if 3 star aligning 2 on 1 side and 1 on another

[Kaptain Klevtsov]

Double check your location and the date format. Those are the usual gotchas. Also double check that Polaris really is Polaris as that would obviously mess things up.

Kaptain Klevtsov

[GazOC]

..and daylight saving is correct.

[James]

.. and when you do a three star alignment start with one on the meridian*, then one to the east and one to the west. Pick stars that are at least 30 degrees above the horizon.

James

* This is something that isn't in the Synscan manuals but lurks on Skywatchers website. I had some problems getting my EQ6 aligned as well as I wanted until I started doing this.

[GazOC]

To get Skyscan working for visual use I've never had any trouble with polar aligning and a one star alignment. I've even gotten the daylight saving wrong before now and had to slew in RA the 'extra' hour to the star and the alignment was still successful.

[trevboyd]

Thanks for all the suggestions guys! Appreciate it!

I don't have many options for which stars to pick at the moment due to the full moon and bad LP, but I'll try some different ones tonight.

I'm pretty sure the mount was polar aligned properly. Is it possible to remove the polar scope from the mount to try that, as I guess its possible I has aligned on another star near Polaris that wouldn't normally be visible to the naked eye? On my EQ-5, I just put Polaris near the centre of the hole in the mount, which seems to work reasonably well...

My biggest question is whether its normal for the mount to end up so far off target when slewing to the alignment stars? It feels like its so far off (e.g. last night it was nearer Mars than Capella) Is this normal? Is it OK to have to make such large corrections on the alignment stars? Is it possible that I'm not starting it in the right park position?

When you power it off and on again, does the computer "start from scratch" or does it keep any information from a previous alignment? The first time I did it several nights ago, I don't know how good the polar alignment was, as it was very cloudy and I couldn't see Polaris properly. Could this have any effect on subsequent alignments on different nights or not?

TIA

Trev

[GazOC]

The mount "forgets" everything except the location when switched off IIRC. I'd be surprised if you had the wrong star for Polaris, there isn't really much in that part of the sky to make that mistake.

The alignment star is usually pretty close and just needs centering rather than any large adjustments. I don't mean to cast aspersions, but have you double checked your location? Maybe E instead of W or something similar, sorry if this is telling granny how to suck eggs..

[trevboyd]

Thanks Gaz

The mount "forgets" everything except the location when switched off IIRC. I'd be surprised if you had the wrong star for Polaris, there isn't really much in that part of the sky to make that mistake.

Yeah, I know there's not much around - I just wondered if the polar scope maybe made it easier to see faint stars?

The alignment star is usually pretty close and just needs centering rather than any large adjustments.

Yeah, I assumed the star should be reasonably close, so that's confirmed my suspicions...

I don't mean to cast aspersions, but have you double checked your location? Maybe E instead of W or something similar, sorry if this is telling granny how to suck eggs..

Ha ha - no worries! I have double and triple checked the location - definitely N and W.

Lat = 51 degrees, 35.8 minutes North

Long = 0 degrees, 41.0 minutes West

Looked it up here - http://www.satsig.net/maps/lat-long-finder.htm

Thanks for your help and confirming that I'm not expecting the wrong thing with the alignment stars!

I did wonder if its anything to do with putting the EQ-5 SynScan on a CG-5 mount, but I can't see what it could be? Or maybe I've fitted the motors the wrong way? Does it matter which side of the scope the Dec motor is on? When pointing nort towards Polaris, mine is on the left as you look north.

Thanks!

Trev

Trev

[GazOC]

Even with a polar scope Polaris is the only 'stand out' star you can see. I can't see the the EQ6 tripod or the side of motor being issues either...

[trevboyd]

Here are some photos of my setup with the scope "parked", which I'm sure is right:

Trev

[trevboyd]

Haven't had a chance to try this again - cloudy nights for a few days now...

Now that the moon is past full, I'll have more otpions for alignment stars, so I'm going to try James' suggestion of the 1st star on the meridian, then east, then west. Not overly hopeful, though, as I expect the mount to end up pointing the scope nowhere near the alignment stars regardless of where they are in the sky...

Trev

[James]

The first time you try they may be all over the place. I've often found that until a successful alignment is done the first slews to the alignment stars are often off. Even if its off, slew the scope using the buttons all the way to the first star, centre it then choose the next one which again may be off. The third star should be a little closer but may still be off by a few degrees. Once a successful alignment has been done by using the handset to slew all the way back to the alignment star etc then things will improve.

Don't forget to start off from the Park or Home position - initially this will just be the point where the alignment marks on the mount line up (you are using a CG5?). Once a successful alignment has been done the mount will remember this position and next time you go out, providing you are roughly polar aligned (i.e. you can see Polaris throuigh the mounts polar scope or hole where the polar scope would be) and are reasonably level and start from that same Park/Home position the first slew to an alignment star should be much closer.

James

[GazOC]

Give the one star alignment a whirl as well, its never given me any problems. I've been doing a one star on Aldebaran all winter and its never failed me.

[trevboyd]

Thanks James.

The first time you try they may be all over the place. I've often found that until a successful alignment is done the first slews to the alignment stars are often off. Even if its off, slew the scope using the buttons all the way to the first star, centre it then choose the next one which again may be off. The third star should be a little closer but may still be off by a few degrees. Once a successful alignment has been done by using the handset to slew all the way back to the alignment star etc then things will improve.

OK, I'll try it again and slew it back to the alignment stars regardless of how far off they are.

Don't forget to start off from the Park or Home position - initially this will just be the point where the alignment marks on the mount line up (you are using a CG5?).

I'm careful to start from the park position (scope facing north, weights pointing down as close as I can tell visually). I haven't seen any alignment marks on the mount, I'll have a look this evening. What do they look like? Do they help ensure its in the right park position?

Yes, I'm using a CG-5 - long story - I already have a EQ-5 with dual axis drives fitted, and my wife bought me a C8-N and CG-5 package from FLO for a good price along with the SynScan (heard it is quieter than the equivalent Celestron offering), so I fitted it to the CG-5 cos I couldn't be bothered taking the other drives off the EQ-5...

Thanks again

Trev

[thumbless]

Been reading this with interest and hope it works out.

As i am thinking of getting a synscan for a CG5/C8N is this a common problem and are there any options available for buying goto.

Read that you need 3 star alignment, cold effects electrics and the data base is not as large as the next star.

Seems to me that telling the mount where it is so it can work out calculations are critical, is this a common problem with them .

Been trying to find out if it is worth paying £315 to upgrade the mount or just get a set of tracking motors.

The moon was cloudy again last night so there is no great hurry and i will check it out before purchasing

Davey.

:moon:

[GazOC]

I think I may have sussed the problem.....

Are you sure that the cogs/ gears on the CG5 have the same number of teeth as the EQ5? The ratios that the motors work to will be all wrong if the mounts are not identical in this respect.

[GazOC]

Never mind, I just checked..they appear to be identical.

[trevboyd]

I think I may have sussed the problem.....

Are you sure that the cogs/ gears on the CG5 have the same number of teeth as the EQ5? The ratios that the motors work to will be all wrong if the mounts are not identical in this respect.

Gaz, I guess this might be an issue, and the mount would have to be taken apart to check. I fitted a cog onto the Dec and RA shafts on the mount (where the slo-mo hand knobs would go) and then the motors fit against those. Obviously, the cogs I fitted came with the SynScan, so they're right, but what if the cogs inside the mount are different in some way?

Trev

[Vega]

I sucessfully use Sirius, Dubhe and Denab at the moment

You can only use Denab in early evening nowadaysnights though. It sometimes more accurate if on the first alignment star you unlock the scope and move it manually to center the star then re-lock.

Matt

[GazOC]

I think the mounts are internally the same (114 reduction) but it's def. worth checking that somebody has actually got a CG5 working with Skyscan before going any further,

[Brinders]

For my three pen'arth, I 'd just say that my experience with the EQ6 Pro is that quite often the first alignment star is well out, the second tends to be closer but still not necessarily in the field of view and the third within the field of view. After that I rarely have a problem. I always make sure the tripod and mount are level and polar aligned.

Brinders.

[trevboyd]

I think the mounts are internally the same (114 reduction) but it's def. worth checking that somebody has actually got a CG5 working with Skyscan before going any further,

I had another go last night, and ended up switching the SynScan to my EQ-5 instead of the CG-5 in the hope that would help. This was prompted by the CG-5 clashing the Dec motor into the RA housing when I asked it to align on Sirius. I assumed it should know better than to slew the motors into each other, and that it was probably caused by the Dec motor being on the "wrong" side on the CG-5.

As I was attaching the RA motor to the EQ-5, I noticed that the motor has two cogs on the same spindle, and that the larger outside one is driven by the motor. I therefore assume the smaller one should drive the mount (otherwise there'd be no point in it being there!) I couldn't remember what I'd done with the CG-5, so I was hopeful this might be the problem... Unfortunately, no. Same problem - alignment stars are well off and after performing a "successful" 2-star alignment, a slew to Saturn resulted in the scope practically pointing at the horizon, not the 43 degrees or so altitude it was at at the time.

On the plus side, the EQ-5 is slightly lighter to lug out into the garden to try with

So I'm still confused.

I did notice that the SynScan handset and Stellarium disagreed on the exact RA/Dec of several objects I tried to slew to. They were a degree or two out (when the handset displays the current position of an object before you tell it to GOTO it), despite having the same location and time info. Not sure if that is indicative of a problem of any sort.

At one point, I turned the SynScan off, moved the scope to the park position, turned it on and did a 1-star align on Capella. The scope was off by maybe 10 degrees in Dec and a little in RA, so I centred it, then selected "Park scope". The resulting park position was around 10 degrees different in Dec to the starting position, which I assume is correct since it "thought" it was "wrong" to start with.

I assumed to start with that my starting position was wrong, but the weird thing is that most alignments or GOTOs are off in both RA and Dec, sometimes by a lot in one and a little in the other, sometimes by a lot in both axes.

Sorry for the really long post describing several problems and issues at once - any advice on any of them would be appreciated Help!

Trev

[James]

Trev,

Sorry for what might be a really stupid question but when you set your scope up do you have the saddle (the bit where the dovetail slides in) positioned so that the screws are on the west side or east, i.e. standing behind the mount looking north are the tightening screws on the left side or the right side?

James

[trevboyd]

Trev,

Sorry for what might be a really stupid question but when you set your scope up do you have the saddle (the bit where the dovetail slides in) positioned so that the screws are on the west side or east, i.e. standing behind the mount looking north are the tightening screws on the left side or the right side?

James

Hi James

I'm not 100% sure to be honest - I think the right?

Trev