HEQ5 GOTO Mount Problems

[anthony.tony]

Hello I have my Skywatcher HEQ5 GOTO mount -I have started having problems with the Goto- When I Do a 3 star Alignment Now -It say Align,ment Successfull but the Mount dose not go to The Right Coordinates it will slew and goto the Object but not to The right Place -It has worked well up to the last couple of Weeks . Tony.

[Merlin66]

What version Scanscan?
If it worked ok before then could be PA or balance issues....

[Shiraz]

+1 for PA, plus double check entries in the setup (eg date, location, daylight saving etc) and time to make sure that these are right - it is easy to inadvertently mess up a setting (eg location) and it is then retained.
It would also be worth checking the mechanical operation - clutches work OK, bearings are free and worm mesh is not too tight.

When it slews to the wrong place, how far off is it?

[anthony.tony]

I juist updated the the Firmware today -It was live and learn but it went OK - I'll Try again tonight .I'll Check my Polar alingment as well I have the Mount Fitted to a pier.As long as the Ground has not shifted -Tony

[Merlin66]

Hmmm
I'm still running V3.27 - it seems to be more stable.....

[raymo]

I have heard of many problems with the later versions over the last couple of years, so I have stuck with 3.27 and never had a problem.
I eventually decided to update, and have just acquired the necessary
RS232 cable, but now I am wondering all over again whether I should
or not.
raymo

[MattT]

I use 3.35 and have no problems with it. I only do a 2 star align though. I have read somewhere that you run into problems doing a 3 star align. Try 2 star align and see what happens.
Matt

[LewisM]

The latest firmwares go to the target precisely, then slew AWAY off target some degrees, but ONLY when doing a 3 star align. I found mine with 3.33 would hunt back and forwards for several iterations before stopping AWAY from the target.

2 star align works though.

But, since I want the accuracy of a 3 star align , I reverted to 3.27. Don't plan changing it either.

[anthony.tony]

I'd Like to thank you all for your Input- I downloaded one version then found the 3.35 version Like you said it works now -It dose a dance on some objects pulls up on them then dances back and forward - Not on all some it pulls up on Target -some it goes over then comes back on target-The main thing is it works again-The Download added Camera control- And some fine tuning adjustments for Encoders- There is a Function for the Polar scope Illumination but my mount dose not cater for it -I am Amazed at all these extra functions -- Tony

[raymo]

It sounds as though I should stick with 3.27[why fix what aint broke?]
Can any one tell me if there is a way to revert to my present version
if I don't like the later one. My mount is about 5yrs old, so am I right
in thinking that I won't be able to utilise the polar scope brightness
control that later versions apparently offer?
raymo
P.S. Sorry, I didn't notice that someone earlier said that they
reverted to an earlier version.

[Camelopardalis]

I updated to 3.35 today and am out tinkering with it now. So far out of about a dozen gotos all have been within the field of view at 165x with a 3-star align and polar alignment correction, some bang in the centre. Will keep an eye on it.

[anthony.tony]

How Dose the Camera Control hook up and Work - Tony

[coldknights]

Hi Tony on the synta mount we are selling we made a special wire up and drilled a hole in the mount , to mount the 2.5mm TRS plug onto see pictures will upload pic of the wire we made.
Not sure if the eq5 and eq6 have the same capability as the mount we are selling the name of the connector is what skywatcher refer as a snap connector.

http://www.iceinspace.com.au/forum/showthread.php?t=111377

Also read this PDF on the ALLVIEW Mount link below

http://ca.skywatcher.com/upfiles/en_download_caty01363042331.PDF

[Camelopardalis]

It definitely dances on some objects, although I didn't managed to discern a pattern. I'll try the 2-star tonight with any luck.

The polar alignment correction in the later versions is useful though, especially if you don't have a good southern view.

[Steffen]

I found that the usefulness of the polar alignment routine outweighs the importance of 3-star alignment, I'm happily using 3.35.

The only thing 3-star alignment accounts for is cone error. You can easily determine the presence of that and correct for it if necessary without the help of electronics.

Apart from the additional problems with 3-star alignments, both 2- and 3-star alignment seem to use algorithms that aren't entirely robust. Depending on the chosen/available alignment stars the pointing accuracy can vary substantially, even if you take great care with centring the stars in a reticle eyepiece.

Cheers
Steffen.

[big-blue]

I had go-to problems before I checked out and substantially corrected the cone error in my mount.

I had been using Ver 3.35 for a while and was enjoying the new polar alignment aspects, but also finding go-to errors on one side of the meridian.

I eventually found my mount had significant error within the mount itself. Basically, the mount head (the bit that clamps the telescope rail) was itself not 90degrees from the Dec axis.

The steps I followed to identify this error in the mount :
1. In daytime, pick a fixed target in the telescope on the horizon. Do this with the Dec shaft (the weight shaft) horizontal (check with a spirit level). Put the target in the centre of a low power widefield eyepiece.
2. Undo the rail clamps, Remove the scope-rail assembly, turn the Dec shaft through 180degrees and re-mount the telescope to look for the same target. Do NOT move the scope in RA at all, just up-down around the (horizontal) Dec axis. If you are lucky, the target will be centred in the eyepiece, and not Left or Right displaced.
3. If it is out, gently push the scope body L-R to see which direction provides correction. This will indicate which end of the mount head is a bit low and could benefit from shimming to square it up so that the telescope rail sits at a true 90degrees to the Dec axis.
4. If the target is not centred, then shim the mount head a bit at a time repeating steps 1&2 each time to minimise the error. I used thin sheet metal : best for shimming as it does not compress or creep under the scope rail.

In my case, following step 2, I could not even see my target in the eyepiece. I estimate the cone error was ½ degree or more. I suspect there are limits to the Synscan 3-star cone error correction, which become more critical with a long FL (narrow field) scope such as my SCT.

There may also be some additional parallel error between the mount rail and the optical axis of the telescope. Steps 1 to 4 above should be independent of this additional parallel error. I reckon such parallel error can only be found by starting (again) with step 1. above, but this time keeping the scope on the mount and rotating the whole assembly via RA (polar) axis till the scope is on the other side and the Dec axis is again horizontal. If the target is off, then this time the shimming is done between mount rail and the telescope tube. I found my telescope was OK in this regard. This of course assumes the telescope is well collimated to begin with, as optical mis-alignment can also introduce some extra errors.

Most net searches on ‘cone error correction’ treat the whole scope plus mount as one assembly, which is OK if you only ever put the same scope on the same mount the same way around. However I found it useful to separate cone error within the mount itself from any additional non-parallel error between mount rail and optical axis.

Having found and corrected such gross error as I had, I am now enjoying much greater pointing accuracy on both sides of the meridian (which when missing, was the clue that set me on this path).
I may have been unlucky to have so much error in the mount itself, and your mileage may vary !

I could have also attempted to remove and re-align the head, so that it sits square when re-fitted. Having now glued in my shim correction, I will leave it there and enjoy some repeatable accuracy for a while.... before I tinker further!

for info, may be useful for others.
cheers