Tracking problems

[raymo]

Can anyone help? I have been happily doing subs up to 100-120 secs
with my 8" f/5 Newt for ages. Of recent times I have been aligning using
Sirius and Fomalhaut. All good anywhere in the sky. The last two sessions
I have used different stars [Rigel and Achenar], and my tracking has gone all weird. I got round stars on the Rosette at 60 secs, so thought my tracking was poor, but acceptable for what I was planning for the session, but on the LMC could only get round stars up to 15 secs. Went back to the Rosette and got 60 secs again, but even 60 secs is way short of normal. I have a little out of balance to keep the gears meshed. It didn't
matter how many subs I took; the very poor tracking stayed the same.
I'm not even sure that the poor tracking has anything to do with the alignment process, but I can't think of anything else that has changed.
raymo

[glend]

What time of night was this ? How close to the meridian was the LMC? Tracking around the SCP can be problematic, and given you got longer subs going back to the east tends to point to that. I was imaging last night and used Canopus and Achenar on either side of the meridian both of which were at around 55 degrees of Alt at the time of alignment around 11pm on the east coast. Did you leave some weight on ths RA axis when balancing?

[raymo]

Thanks for the reply Glend. I always have a little weight working against
the drive. It was about 9pm W.A. time [midnight eastern time], and
Canopus was about 20 deg east of the meridian. I have used Canopus
and Achenar before, and will try them tonight. I neglected to mention that last night I was using my little 80mm f/5 ref, so tracking was more than doubly horrendous.
raymo

[raymo]

Well, tonight was even worse. I tried 4 different pairs of stars over a period of nearly 3 hrs, and when below 1 deg of error I would get nonsensical readouts, and the scope would miss the next star by 10
or 11 degrees. On the fifth pair, [Rigel and Canopus], I eventually got down to less than a minute of error on both axes, but the best tracking
I got with my 80mm f/5 refractor was 20 secs on M42, and barely 15
on NGC 2070. I normally get around 200 secs with this scope. I have
no idea what is going on. If this carries on I might give up imaging, and
get the trusty 10" Dob out.
raymo

[glend]

Raymo what version of Synscan software are you running on your handset? And have you upgraded that from what has worked previously? There have been some recent threads dealing with errors alignment in V3.35? When you say nonsensical readouts what does that mean exactly, do you have an example?

Secondly, what happens if you test it with the 8" newt? I am thinking that the 80mm might be too light to properly load the drive (and push the tripod down on its points), and keep slop out of the alignment. Has anything changed in your mount set up like tripod placement? I know my NEQ6 needs to be pushed down to get the leg spread right before I put on the spreader, Just trying to think of possble causes.

That 80mm refractor will be much lighter than the newt and you will probably have had to extend the tripod legs to get the EP height up for the refractor; so if you have extended the tripod legs significantly it won't be as stable, expecially if you have less weight on the mount. Did you extend the legs? Are the clamps tight? Do you have a weight you can attach to the centre lock bolt to pull the tripod down on its stops? Check the tripod first I think, as it's all about that base.

[jenchris]

If it has suddenly gone awry, I'd suspect the power supply connection.
I have a friend with an heq5 who cant get decent tracking.
He uses a mains transformer and I suspect it is that.

[raymo]

Thank you for your replies Glen and Jen, [I'm a poet and didn't know it].
Firstly Glen, I have been running 3.35 successfully since not long after it came out. A typical nonsensical readout would be for instance, after an iteration I would have a readout of say Mel + 1' 48" and Maz + 2' 20", and after the tiny adjustment was made, the next readout might be
Mel - 59' 10" and Maz - 1deg 10" 20". The 8" Newt is my last option which I shall try on the next clear night. The R.A. axis is a little stiff on my HEQ5, and I think you might have hit the nail on the head when you say maybe the 80mm is too light. I have tracked successfully with it
before though, some 6 months ago. I don't extend the legs; I sit on a low stool. The tracking error is continuous and steady in one direction, which
suggests to me that an unsteady platform is not the cause. I've had occasional hiccups before, but never had the scope miss it's next
alignment star by 10 degrees +.
Jen, I don't think my power source is the problem. I use a car battery
to power the mount, and 240v to power my laptop, and the camera
[through it's 12v adaptor]. The car battery always has sufficient power, as I have a 2 amp charger connected to it during my sessions. The car battery setup has served me well for over 50 years of viewing and
film imaging.
raymo

[jenchris]

Right, put a tick against that, I suppose it wouldn't be the connection at the mount?

[glend]

Hmm, so its an HEQ, now I am not so worried about the weight. Jakob runs an 80mm refractor on his HEQ and doesn't seem to have any problems but he is autoguiding on his targets but seems to find them ok after alignment.

What if you do a two star alignment and then go back to your first alignment star after it says alignment successful - does that first star appear exactly in the centre of the field of view? If yes I would then slew to a nearby target and see if you can track, then move say 90 degrees further and see how it goes. I am suggesting trying to determine where the errors start.

BTW are you using PAE on your tracking target to correct for that sky zone?

[raymo]

Yes it's an HEQ5 Pro GoTo. I have always been able to track for around
100-110 secs anywhere in the sky, provided I have taken the time to get the error down to less than about 30", so I've never found the need to use PAE. My tracking now is appalling everywhere in the sky; 15-20 secs
max. with the 80mm, should be around 200-240 secs. One thing that intrigues me greatly, is when I am getting to the final tiny adjustments,
one of the two stars I'm using will be close to the square in the reticle EP,
but when I move to the other one, it is outside of the reticle EP's F.O.V.
altogether. I have also noticed that the go to accuracy varies significantly
regardless of how well I do the P.A. Last night it was Canopus and Rigel.
Canopus got closer to the square with each iteration, as it should, but
even when the error readout was down to around a minute or two, Rigel
stayed outside the F.O.V. each time I moved to it. It is so weird.
raymo

[Larryp]

Raymo, have you actually checked the condition of your battery even though you have a charger constantly connected? If the battery is not in good condition, you can still have problems.
The Synscan system seems to need a very healthy power supply to work properly.

[raymo]

Thanks Laurie, I'll check it out with a load tester. That reminds me of my daughter's car which had extremely high mileage on it, and the mechanic
suggested she get rid of it, because one cylinder was about shot, and was causing it to misfire. We bought it from her as a runabout town. A couple of months later the battery failed. New battery, no misfire. The battery had been making and breaking.
raymo

[Merlin66]

Raymo,
The tracking accuracy doesn't have much to do with the GOTO accuracy...
A good PA and balance, (and power supply!) usually fix things.

[raymo]

Yes I realise that the two are not really connected, but I just seem to have problems with both at the same time. I'll have to take a look at the drive gears. I don't recall whether the drive shafts have flats on them.
Million to one shot, but maybe the drive gear is slipping on the shaft.
raymo

[raymo]

Last night I was able to get round stars at 90 secs, and could have probably got longer, on NGC 2070, but as soon as I went across to
try and get some more subs of M78 I was down to a max of 8 seconds, no matter whether I balanced the tube neutral, against the drive, or
with the drive. Weird!!!!!!
raymo

[Camelopardalis]

You're not along raymo! Me and my EQ6 have a love-hate relationship, regardless of Synscan version. The past 6 months I've been using the same scope/camera setup and despite my best efforts, the lengths of subs I can take varies wildly from one New Moon to the next...3 months ago I fluked 5 minute subs, this month I could only manage 2, and I even had to throw a bunch of those away. In the summer heat, my uncooled camera can't stand the longer subs anyhow :sadeyes:

I've resigned myself to having to drift align. It's time consuming, but the better results I've got seem less related to the polar alignment routine and more on the attention to drift in my subject area. Once give gone through a couple of iterations of the Synscan polar alignment, I align the camera so that motion of RA and Dec follows the horizontal and vertical grid pattern on the camera live view. I'll then start taking subs of about a minute and then make an adjustment in one axis, take another sub, see if the trailing gets better or worse, then continue/counter it until the trailing is minimised. Increase the sub length gradually and adjust and repeat. Then work on the other axis. It's a bit tedious, and might take an hour or two, but I've had such varied experiences with the polar routine I'd rather just trust my eyes. It's not a proper drift alignment, but it seems to work more reliably.

Sorry I don't have any pearls of wisdom to help your specific problem, but I use a small scope with camera of no more than 3.5kg on the EQ6 and balancing isn't a problem, so it shouldn't matter how little your scope weighs you should be able to get it just a tiny bit out of balance to keep the gears meshed. It should be possible, but I understand and share your frustration!

[raymo]

Thanks for the response Dunk. I get varying sub lengths too, but this is
ridiculous. I checked last night's efforts closely, and got round stars up to
65 secs when on NGC 2070, but on M78 across the other side of the
meridian I got 8 secs. 65 secs is appalling, but 8 secs is almost unbelievable. I'm out of ideas.
raymo

[Camelopardalis]

Btw, I tend to use 3-star align because I'm fairly certain the puck of the mount doesn't hold my scope square with the axes, but maybe that's my undoing too :shrug:

There seems to be an art to the alignment star choosing, but I usually aim for 3 stars in a wonky triangle...so 90-120 degrees apart and with at least a 30 degree difference in Dec between the first two. It's not always easy, at least for a northerner, to identify some of the stars the handset suggests.

[raymo]

Yes, I'll have to try some different stars too. My problem is that I generally use the same few stars, and have never had significant
tracking problems before.
raymo

[Steffen]

Just out of curiosity, which way does the star elongation go, RA, Dec, or both? And whichever way it goes, is it consistent?

Cheers
Steffen.

[alpal]

I suggest you use an OAG.

[jenchris]

Would the backlash affect where your apparent point of aim ends up when you're aligning? Would it make any difference?

My Neq 6 seems to be able to stick pretty much to the target with very little adjustment.

Is the ground your pier sits in swelling up with the recent rain?
I've no idea what I'm talking about, just trying to come up with something you maybe haven't included......
Is your puck cracked?

[raymo]

The elongation is in R.A. only, and is a practically perfect straight line for as long as I have left it tracking, which is about 7 or 8 minutes, which, as the Dec tracking is as good as ever, shows that my P.A. is as good as
usual. I thought for a moment that I may have had lunar or solar tracking
enabled, but not so. It wouldn't have made that much difference anyway.
I haven't thought to see whether the R.A. tracking is running slow or fast, although I can't see how it could run fast. The really confusing thing
is the huge disparity in tracking quality between targets on opposite sides
of the meridian.
Thanks Jennifer for your suggestions; all comments will be taken on board, as they say.
I would use an OAG alpal, but a thin OAG and guide camera are beyond my budget at the moment, plus L.P. would restrict my exposures to not
much more than the 100-120 secs I normally manage.
raymo

[glend]

Raymo, Can you explain what you mean by the disparity on different sides of the merdian? If the RA had slop in the gearing it coud explain the difference. Does accuracy improve as you get near the meridian as its climbing or does jt get worse or remain the same. If you did a series of equally timed exposures on a climbing target it might tell you more about how RA is behaving. Reset and then do the same on the falling side of the meridian. I trust you still have RA balanced with more weight on the bar to keep the gears meshed.

[Steffen]

Synscan (in EQ mode) won't track in Dec anyway, you have to have good polar alignment or the stars will wander off in Dec. The fact that your tracking error is in RA only seems to prove that your polar alignment is good.

Will the displacement in RA get continuously larger over time, or does is oscillate back and forth? If it only goes one way (too slow) than a gear slipping on its shaft is a good lead to follow, especially if the RA axis is stiff. The gear on the worm shaft can be tightened with two set screws, but unfortunately the sprocket wheel, once loose, cannot be tightened on the motor shaft. Sounds like your mount could be a good candidate for a belt mod :)

Cheers
Steffen.

[alpal]

I had the same trouble as you when I started out &
only an OAG can give you guaranteed sub frames - round stars.
Even with my EQ6 correctly drift aligned using the camera
I couldn't go beyond 30 seconds.
Even then - some frames would have to be discarded.

[raymo]

Thank you everyone for your responses. I will check the R.A. drive gear to see if there is any slippage on the shaft. If not, I will do some test
subs as Glend suggested, to get a better idea of what is going on.
raymo