EQ6 Pro tuning

[Ivor]

I have been continuing to have problems with my guiding with no amount of modifications to PHDguiding2 seeming to fix the problem, I continue to get images with squashed stars and find it hard to pull out the details in target. This is the last target I  tried to process, I stopped at this point as I'm not happy with quality of details in M51 to the mount movement.



I've previously replaced the bearings in my mount and decided to revisit the internals to double check whether there was any play in the worm gears. Having put it all back together I'm now struggling to get the gear and worm to mesh correctly. My workflow is as follows:

1.       Loosen the RA worm carrier bolts

2.       Loosen the RA carrier upper grub screw (on repeat make ¼ turn adjustment)

3.       Tighten the RA carrier lower grub screw (on repeat make ¼ turn adjustment)

4.       Tighten the RA worm carrier bolts

5.       Move mount 360

6.       If mount binds stop and goto step 1



With each ¼ turn the range of movement increases until I get to a 120 degree range of movement after which I can't make any further adjustments with the grub screws. So I'm now stuck and not sure how to get around the problem, any suggestions? What am I doing wrong?

[The Thing]

I would loosen off the grubby adjustment, use the handset to do a driven rotation to find the tight spot (will sound different), adjust the worm by just pressing the carrier body with your hand (you have control of the tightness of the fit) after loosening off the grub screws (they are a rrright pain), then tighten the hex bolts and run around 360 to check. If you tighten the clearance too much at a loose spot it'll bind. This works a treat on my HEQ5 and is quick. I tighten the grub screws lightly after all is set i.e. they take no part in adjustment process.

BTW Eventually I dismantled and reassembled the whole RA axis assembly as the clutch body casting was not set properly on the shaft and pushed on the worm gear brass lump which was then was binding at the opposite point making me think the binding was caused by the worm adjustment. All centred up now.

[Ivor]

It's taken me a lot longer than planned to get back to my mount but I have now fixed the gearing. The problem appeared to stem from the alignment between motor and the worm, they are realigned and the mount rotates nice and quietly with no problems.

- cogs

Unfortunately I'm left with a lot of backlash and I'm not sure what to check and adjust to remove it, What would people recommend I check?

[Ivor]

With the help of Julian I resolved the backlash issues but one of the grub screws had worked loose on the polar scope which meant it was no longer centred so I have been trying to resolve this over the last couple of months. Following a tutorial on Astronomyshed I managed to get close but couldn't get it perfect using my eye as a small change in the angle of sight would change the central cross away from the background object I was trying to realign to.

I decided to get around the problem by building a polar camera out of a SPC880 which was a challenge in its own right as I needed a XP machine to flash the camera to a SPC990 to work on Windows7. My only remaining XP machine is a old netbook with the screen smashed, getting it working provided challenging as all the browsers were out of date and the download sites didn't support the old browsers and wouldn't let me in.

I got there in the end and connected the camera to polar scope and centralised the scope. I've now got it to a point where it is really close, the question is whether it is close enough, the grub screws don't really allow for super fine tuning so I could find further changes makes it worse.

The video below shows the current alignment, the goal is for the tip of the aerial to stay on the polar circle and it sways by a small amount do you think this is close enough?

https://flic.kr/p/umqpUo

[JohnP]

well it looks pretty darn near perfect to me... dont think mine is that good.....

[Carole]

well it looks pretty darn near perfect to me... dont think mine is that good.....

ditto

Carole

[RobertM]

That looks really good ! especially if you consider how much Polaris can move depending on how central your eyeball is in the polar scope.

Robert

[Ivor]

Great nearly there then. This all started with my elongated stars so I'm adding OAG to the image path to remove any flexure just need to work on the space for the Lodestar and ST8300, hopefully I'll get this done before DSC.

[JohnP]

Ivor - when I was actively imaging I remember spending a year or so trying to solve the exact same problem you have... elongated stars - It was driving me nuts.. Eventually I bought an OAG and the first night I tried it I went from my previously normal elongated 1 or 2 min subs to 10 min perfectly round subs - in fact I can even remember doing a 30min sub cause I was so chuffed. So I am sure OAG will help solve your issues along with all the other changes you have made. Just a couple of pointers;

1. Focusing your camera through OAG can be somewhat tricky (especially in middle of night) so I would highly recommend setting it up in daylight & focussing on a distant object before you start your night time session.
2. Don't worry if the stars through the OAG have weird shapes - mine typically look like half moons... as long as your guiding S/W can calculate & fix on centroid it doesn't matter.
3. Finally, make sure you cable tie or tether all cables to scope tube or like as even dangling cables can cause shift as scope rotates (found that out as well)....

Good luck - john.

[Ivor]

Some good points there John, thanks. I've already tried to align them once but the ST8300 doesn't work well during the daytime as the shortest exposure time is about 0.5s so I'm going to have to do this in two parts. Firstly I'll get the ST8300 focused and locked in and then during the day repeat the process for the Lodestar. Fingers crossed!

[RobertM]

I've not had a problem with focusing with my OAG and lodestar with real stars, in fact I find it much easier.  I did this recently at 2000mm f/l and 2s exposures but it'll be much easier now the summer Milky Way is rising earlier.  Start at one end of travel then move it about 0.5 mm between exposures.  With that refractor you'll have loads of stars to focus on - the area around m57 is ideal for this.

As John mentioned be careful with your cable management, especially with the usb cable from the lodestar - fix it well to avoid any movement as best you can and avoid dangling cables.

Hope it goes smoothly.

Robert

[Ivor]

Well as nothing I try seems to end up simple, anyone seem banding on a Lodestar before?

[MarkS]

I can't comment because I don't have a lodestar.  But you've managed to create quite an arty image - "silhouette of tree through venetian blinds"   

Mark

[Mac]

Turn on 2x2 binning, it should disappear.
If i remember there should be a venetian blind correction tick box in the loadstar software. (its been a while since i last used it  )

Mac.

[Ivor]

I've received a reply from starlight express (pretty impressed I got late last night) and they said it's often caused by insufficient power from the USB cable so I've plugged into the power hub and it seems to be working. I managed to do a brief bit of guiding last night before the clouds came in which is a massive improvement.





All I need to do now is to get the pacing right with the lodestar, QHY8L (decided to use my OSC instead for now) and flattener and I'm imaging again!