AZ-EQ6 has a case of the hiccups

[jambouk]

Knocked my AZEQ6 out of polar alignment and left the Canon on the ED80 doing 4 x 10 minute unguided sidereal-tracking-rate subs on a brighish star to the west; stacked in DSS with alignmment turned off. I'm not sure if I'm surprised at how straight the line is, or how subtly wavy it is

I think I should have used a longer focal length scope to make the wave more pronounced.

James

[kendg]

Just waiting for some clear skies to try the same thing. 

[Owmuchonomy]

My mount has been replaced so just waiting for clear skies to validate the replacement.

[spaceman_spiff]

From the first image, it looks like the mount drifted reasonably slowly in RA before settling down again...Strange. 

I'll keep an eye out for this with my AZ EQ6.

[1parsec]

If you have the balance in RA too perfect the mount could track at each side of the backlash. 

Try offsetting the balance so the East side is a bit heavier.

[kendg]

OK. Another update. 

I think I may have found the problems.

2 problems for certain. 

1) backlash. RA has quite a bit and DEC has a little.

    working on getting this one solved.

2) OTA balance

    forgot to re-balance after adding a larger battery pack to my camera.

Working on getting these things resolved before the next clear nigh. Clear nights are turning into a bit of a rarity lately here.

Clear all day then the clouds roll in. 

Once these 2 things are resolved and I build a dew heater. Really needed when it gets freakin' cold here.

Got to -5 with 95% RH the other night. The red rod was "just" barely useable and my telrad was completely frosted u[p.

Even with the dew shield I was only able to use the scope for about 45 min.

So, nichrome wire is on order and I'll have a new dew heater shortly after it gets here. I'll need it for -20 to -30 weather.

At least the skies are really clear when it gets that cold. 

[spaceman_spiff]

Good to hear that you tackling the problems! Let us know if that sorts it out!

With regards to the dew heater: make sure you use a fused dew heater controller (preferably using a PWM dimmer circuit). Here's a good link:

http://www.blackwaterskies.co.uk/2013/05/a-cheap-multi-channel-dew-heater.html

 

[kendg]

Yes. That's the link I've been using as my guide.

PWM controllers, nichrome wire, fuse holders all on order (and spares too).

Probably do at least 3 heaters. 1 for the scope, one for a guide scope (eventually) and one for the telrad.

Maybe even do one for my chair too 

[kendg]

Well, looks like the hiccups are gone. I think it was down to a backlash and balance issue.

Polar alignment is pretty close and I'm up to at least 3 minute subs. Haven't tried longer, but maybe tonight.

Now on to making dew heaters (when all the parts show up) and working on imaging with flats and darks.

Nice to be able to sit in the house now and control the scope via wifi. Just need to find plans for a USB focus control now. 

Slowly making progress.

Thanks all for your help so far. It's been great.

[spaceman_spiff]

Just thinking out loud here, this is what I imagine is happening:

When tracking east of the meridian and after balancing the OTA in DEC and RA, the mount effectively pushes the OTA from east to west. If extra weight is added to the OTA, it will then start moving from east to west by itself (without being pushed) by the mount. Now the RA worm gear reaches the other contact and prevents the OTA from moving east to west as fast as it wants to. However, a gust of wind, excess grease in the gears or other sporadic event could also temporarily prevent the mount moving east to west by itself cause a temporary freeze in RA movement (the target then starts to drift). After a while (depending on the amount of backlash in your RA), the worm gear engages and starts to push the OTA east to west. The OTA then overcomes whatever caused it to freeze and moves west by itself.

This could lead to the sporadic drifting in your mount.

To overcome it you could:

- Reduce backlash (you are already doing this!)

- Weight the OTA so that it wants to move against the RA drive (West to east when you are east of the meridian)

- Re-grease the RA (and dec) worm gears to reduce any patches of higher friction).  The skywatcher grease may not perform well in sub-zero Canadian temperatures! I'm thinking of doing this myself but not sure if it is a good idea, it might cause more problems than it solves. I will probably start a post on re-greasing soon.

Let us know how you get on tonight.

   

[kendg]

Almost all the backlash is gone. 

There is literally zero backlash in DEC. Changing direction on the paddle is very smooth.

A small bit of backlash in RA. Just a couple of nudges needed when changing directions with the paddle. I'm going to work on getting that down a bit more.

Polar alignment now is very close.

Mel is 00:00:35

Maz is 00:01:17

Getting 4 minute subs now and the stars are still pretty round 

One other thing that does bug me a bit.

I do the following for setup 

1) starting from parked position

2) 2 star alignment

3) polar alignment (usually just minor correction needed as the mount is never moved)

4) 3 star alignment

The first start on the 2 and 3 star alignments is always out of the field of view i=on the camera (DSLR) but only in 1 direction.

Pressing the left direction key for a bit brings it right into the center. The next star(s) are very very close to the center. Just minor corrections needed.

The stars used are Vega, Deneb and Cappella for the 3rd star.

Looking forward to when you get around to a re-greasing post. I might be tempted. I've got some great low temp lithium grease for bearings on my tractor. 

Thanks to you and all the people on SGL, I'm making a lot of progress.

[Owmuchonomy]

If you are starting from Park then there is no need to do step 2 or 4 or even 3 really.  You are just undoing all the good work you have previously done.  The GoTo accuracy is improved if you disable the encoders.  You may find this removes your first star misalignment. I always use this arrangement.  If however you wish to manually move the mount make sure you switch them back on and let them settle for a few seconds!  The 2 star and 3 star alignments do different things.  Use 3 if you wish to take account of cone error for visual observation and use 2 if you are imaging one side of the meridian.

[kendg]

If you are starting from Park then there is no need to do step 2 or 4 or even 3 really.  You are just undoing all the good work you have previously done.  The GoTo accuracy is improved if you disable the encoders.  You may find this removes your first star misalignment. I always use this arrangement.  If however you wish to manually move the mount make sure you switch them back on and let them settle for a few seconds!  The 2 star and 3 star alignments do different things.  Use 3 if you wish to take account of cone error for visual observation and use 2 if you are imaging one side of the meridian.

OK. That makes perfect sense and will save me time 

Looks top be a case of "just because I can do it doesn't mean I should"

Sometimes I can get too carried away doing things.

I like to do the 3 star alignment last, just in case there is a bit of cone error.

Thanks a lot.

[Pompey Monkey]

OK. That makes perfect sense and will save me time 

Looks top be a case of "just because I can do it doesn't mean I should"

Sometimes I can get too carried away doing things.

I like to do the 3 star alignment last, just in case there is a bit of cone error.

Thanks a lot.

Good to hear that you are getting on top of the hiccup problem

As for alignment, what's that? Goto? What's that also?

Do you work with a laptop/computer when you're imaging? If so, go to a plate-solving solution. It's like witchcraft when set up correctly and saves heaps of time.

[kendg]

Yes I use a laptop. Mainly so I can connect to it from inside  the house. It gets darn cold here in winter. 

Which plate solving solution will work with a Canon DSLR? That-s the only camera I have attached (so far).

Now you have my interest 

[Pompey Monkey]

I use Astrophotography Tool (APT), of which there is a free version that works with two different (also free) plate solvers. These are PlateSolve2 and All Sky Plate Solver (ASPS). I use ASPS because it can doo a "blind" solve i.e. no prior knowledge of the telescope's position is required.

In APT, it is as simple as pressing the "Auto" button to get the 'scope current position. This takes an image and solves it, and syncs ASCOM position (the same as one star alignment). Then, chose an object form the database or define an RA and Dec., press "Goto" and off it goes: The mount slews to where it thinks you want to be, a picture is taken and solved and the position is refined accordingly. With my CCD, it takes anout 20-25 seconds to solve an image and 2-3 iterations to get to where I want to point withing a handfull of pixels. 

I can fire up the 'scope and be pointing at my target, ready to focus in around five minutes!

There is some initial setting up to do (and ASPS is very fussy about the image scale), but as long as the camera is roughly focussed enough to get some stars in the image, it works.

APT: http://www.ideiki.com/astro/

There are other solutions out there, for sure. But this one works for me, and also worked previously with my DSLR on the same mount.

[kendg]

Something to try. Thanks for the info.

Greatly appreciated.