NEQ6 Bad tracking issue?

[Perkil8r]

Last night I was out early on so was late setting up. I put the mount on it's pads in the usual spot, made sure it was level, which it was. Went through my usual routine for polar alignment and got polaris bang in the middle of the small circle. Set it to the home position spot on. Turned on the mount and went through setting location (no problem there), date (yes month, day, year) and time with DST selected. No problem, all of that was correct.

 

Started 3 star alignment, it was a country mile off, so centred, enter, move to next star. A country mile off Did all 3 all a mile off but corrected as it went on. Then slew to Arcturus, a mile off   so parked the scope back at home, no problem there, it went straight to home. Turned it off and started again, same thing so did it again, yet again . Fourth time though and it was pretty much spot on with all 3 stars, just a tiny adjustment was required. Checked through polar scope as an hour had now passed and polaris was still dead on the line of the bigger circle in the correct orientation to be correct.

 

Great I thought, move to target, spot on   bang in the middle of the chip. Start to image with the ED80 and 350d so not massive focal length. 2mins, great I thought, just check the first one make sure all is well and I'll leave it running while I go have some beers. Star trails   tried a few more subs, all the same, star trails around 10x the size of the star! Checked sidereal rates hadn't altered or anything stupid, battery showing full charge, so dropped it back down to 60secs. Still star trails but not as bad. roughly 50% had star trails of 2-4x the star size, the rest were pin point.

 

So.......

 

Any ideas what the problem could be? A few days ago went through the exact same alignment etc and plonked the 200p on. slewed straight away spot on but was getting star trails on anything over 60 secs so I assumed the polar scope was slightly off centre. I thought that might be the problem last night so I have checked this morning and it is off by a very very very small amount, certainly not enough to cause that kind of tracking error. I have ruled out:

 

Polar alignment: - polaris stayed on the line the whole time and when I was packing away I re checked the PA and it was bang in the circle for that time as it had been for the start time getting on towards 4 hours apart.

 

Not got Polaris: - must have been polaris or else it would not have been staying on the line in the polarscope over that amount of time.

 

Tripod Level: - checked but with PA spot on that would not make any difference anyway.

 

Scope Balance: - Double checked twice at the beginning and again at the end.

 

Other: - The scope was tight in the mount, no movement relative to eachother.

 

 

Any ideas????

[Sheila]

sorry Mike, but i used to have this trouble with both the EQ5 and the 6.  sometimes it was very good and other times it was awful.

 

I never did find out what the problem was.... i had assumed it was a blonde issue  but obviously not.

 

Maybe someone else can come up with something this time?

 

Sheila

[+Graham]

Mike.

This may sound like a stupid question but bear with me.

Is it tracking too slow or too fast. ??

 

one thing you can try as a test is this.

 

Manually line up and run a sub on a star in the S to SW area so the weight is on the east and the rig is in a horizontal position.

Flip the mount over and do the same again on the same star but with the weight on the west . You will probably have to disengage the limit stops.

 

Check the subs and see the difference.

[Perkil8r]

That's the weirdest part Graham, over the hour it was running on 2 min subs before I deleted them, the stars were still in the same place from start to finish, within a couple of pixels anyway. So I'm not sure as it is actually running at the wrong rate if that makes any kind of sense?

[+Graham]

Yup makes perfect sense.

What would help your cause greatly is to get the camera hooked up to a lap top.

Then if you run something like BYE you can watch what it happening in 'real time'.

BYE has a 'target set up screen' for want of a better way of putting it.

On here you can overlay a reticule.

Run at say 10 second subs.

Center the star in the reticule and you can see if it drifts and in which direction.

You can then correct this drift by either moving the weight balance or altering the mount adjusters.

[Perkil8r]

I've found some play in the RA axis, probably around 10-15 minutes I would estimate. Will adjust the worm and see if that cures it or not.

[+Graham]

I've found some play in the RA axis, probably around 10-15 minutes I would estimate. Will adjust the worm and see if that cures it or not.

 

oohhh thats not going to help much with the goto, mind it should not affect the tracking a great deal unless you are pointing at the zenith.

[Perkil8r]

Don't know really, but if there's a breeze and it has play it could make it wobble maybe?

[+Graham]

Thats very true Mike.

Thats the problem with being obs set up dont need to consider these things unless its blowing a gale.

[glider]

Is your tripod setup on paving slabs, are you walking around it a lot some nights and not others?

 

My slabs wobble if I do.

[Perkil8r]

It's sat on pavers sunk into the ground with dimples drilled in so it can't slip about. I was nowhere near it on either occasion.

[glider]

Was it windy?

[Perkil8r]

a little but not bad, have had a lot worse with the eq5 and managed much longer.

[philjay]

Sounds like your suffering from the effects of polar alignment and PE issues Mike.

 

I started imaging with an ST120 on an EQ3 and this had horrendous PE. So much so that I made an indicator on the RA worm so that when it was in the red zone I wouldn't image, this was for about 2 minutes out of 8 of the worms rotation. In the red zone I couldn't even get 40 seconds worth at F6 without trailing. Out of the red zone I could get close to 2 minutes BUT the polar alignment had to be spot on as I would get trailing then.

 

I know the HEQ5 and 6 have better controlled PE but its still there and if you are stretching exposure out to 2 minutes then your pushing it even on a good day I reckon.

 

Try running the PEC routine then see what happens. You will have to train the mount and record the PE then when you are imaging you play it back like a macro

 

If that don't work then it's the black art of autoguiding I reckon mate

[Perkil8r]

PEC training? oh dear...... looks like yet more geek stuff to learn. I'm setting up ready for guiding anyway at the minute so it won't be long now

[Antares_Paul]

Guiding and using Astrotortilla has without a doubt transformed my imaging experience.

I still haven't started imaging in Ha but have been testing my entry level mount's capabilities. Admittedly I have super tuned the HEQ5 but nevertheless I am extremely happy with 1200s subs;

 

 

Single sub. No calibration. Simple stretch.

Image quality not important. Star shape is 

 

I plan an 1800s test next time out. If successful then my HaRGB runs will be 900s RGB 1800s Ha.

 

BTW I guide with a 9x50 finderscope/PHD and the ubiquitous QHY5.

 

Regards.

[Perkil8r]

Guiding and using Astrotortilla has without a doubt transformed my imaging experience.

I still haven't started imaging in Ha but have been testing my entry level mount's capabilities. Admittedly I have super tuned the HEQ5 but nevertheless I am extremely happy with 1200s subs;

 

 

Single sub. No calibration. Simple stretch.

Image quality not important. Star shape is 

 

I plan an 1800s test next time out. If successful then my HaRGB runs will be 900s RGB 1800s Ha.

 

BTW I guide with a 9x50 finderscope/PHD and the ubiquitous QHY5.

 

Regards.

 

That doesn't really help TBH, Guiding will always help with this issue I know, it's the fact I should be able to go longer than 60 secs without it that is doing my head in.

[Guest Kheldar]

That doesn't really help TBH, Guiding will always help with this issue I know, it's the fact I should be able to go longer than 60 secs without it that is doing my head in.

 

Do not fear guiding .... embrace it

[glider]

That doesn't really help TBH, Guiding will always help with this issue I know, it's the fact I should be able to go longer than 60 secs without it that is doing my head in.

Why do you think +60s is a reasonable expectation?

[Antares_Paul]

That doesn't really help TBH, <snip>

 

You sorted your other mount so do the same with the new one. Gear mesh/backlash, balance and cable drag are the areas to concentrate on.

Purely for satisfaction, a complete strip down and regrease 'acquaints' yourself with the mount. Learn it's nuances. Consider the belt drive mod.

 

Or spend 5k on a GM1000 and never consider guiding ...

 

Good luck Mike. I'm actually with you on wanting to resolve this perceived problem. I find overcoming niggles in the kit one of the more rewarding aspects of this hobby. If I am teaching a granny to suck eggs - you have my apologies.

 

Regards.

[Guest Kheldar]

Or spend 5k on a GM1000 and never consider guiding ...

 

 

I know someone who would beg to differ on that score

[+Graham]

I know someone who would beg to differ on that score

 

:lol:

[Antares_Paul]

I know someone who would beg to differ on that score

 

I've never seen a 2 week sub before 

 

Regards.

[Perkil8r]

That doesn't really help TBH, Guiding will always help with this issue I know, it's the fact I should be able to go longer than 60 secs without it that is doing my head in.

Why do you think +60s is a reasonable expectation?

 

I think it reasonable since I have gone to 360secs with the eq5, but I enforced my own maximum of 300 secs to retain 90+% success of subs being good.

[philjay]

What scope was that with Mike?