HEQ5 Synscan

[russ]

Martin & CC,

Emails enroute - let me know if you need the autoguiding tutorials?

Regards

Russ

[Kaptain Klevtsov]

Checking stuff today after work, well in a break from it anyway.

Last night when pointing at Saturn (yes I can find that) I noticed that the tracking was boing..one..two..boing..one..two..boing so I had guessed that each boing was a stepper motor step. Not so. In the bible it states 9 million odd steps per revolution. By my sums thats about 100 pre second as there are 86400 seconds per day. So its NOT the steppers. Could be the backlash in the gears is too tight. Reset that ready for another go tonight. I had set it quite tight so I guess that could be the problem. I had also (in my wisdom) reset the backlash in the motor / gear combination which seemed a little baggy. We'll see tonight if it is better.

Nicked the boy's planisphere for a browse (pound shop one that Santa brought him 'cos he's learning about planets at school) but it doesn't show the names of many stars. He can have it back now.

Last night was missed as we had to go see her friends for dinner and drinks. A pleasant evening improved by the poor weather.

For tonight I'm going to try to load up starry night on the lappy to find the stars more easily, and plug in the webcam thing.

I'll let you know how it goes.

Captain Chaos

[MartinB]

CC - set starry night sky for big city light pollution to help you decided on good alignment stars.

Martin

[Kaptain Klevtsov]

Great idea.

Another thought that I had was setting up the setting circles to get me in the ball park. Would that work?

Captain Chaos

[MartinB]

Whoohooo! Brave man. Another area rich in frustration. you need a good polar alignment. Excellent article by Greg here http://stargazerslounge.co.uk/index.php?topic=2455.0.

Those stars really shouldn't be that hard CC.

Martin

[Kaptain Klevtsov]

But if its cloudy, then I could possibly fool it into thinking that I had aligned properly to get close to something. Or should I just go there manually using the setting circles?

I thought that doing it once would be enough and then after that it will goto correctly.

Captain Chaos

[MartinB]

Don't know CC. If it's very cloudy with just a small area to observe I guess you could polar align using a compass and getting the latitude set correctly on your mount. then slew your scope to invisible alignment stars using setting circles then ask it to goto but you are multiplying error on top of error and the results are likely to be pretty iffy to say the least. If you can see polaris then you might be in with a shout :?

Martin

[Kaptain Klevtsov]

Re the backlash - got that sorted. I had got it too tight and that was causing the jerky movement. All OK now.

I've got a minor gripe with the polar alignment which might be sortable with your help. When I've "parked" the scope (so that it remembers where it is - right?), put it away and then got it out again, the main (RA?) shaft is in the wrong place to polar align. The plan was to polar align before hanging the 'scope on it. The park position leaves the counterweights hanging straight down (as in no load on the cogs) so I could drag the mount about until it's pointed the rigt way. The hole doesn't line up so that I can't see through it and the polar scope pictures are in the wrong place. I'm wary of swinging the weights around as that might overload them with the lack of the 'scope to balance the thing. Option 2 is to hang the scope, then drive it to the right orientation, then polar align. That means dragging the mount and 'scope around which I think is a bit dodgy.

Am I missing something? I am hooping that there is an option to specify the park position with the 'scope horizontal as that's easier to put it on and take it off.

Also still getting alignment Probs as sometimes I can't see through the EP as it's in the wrong place when I've pointed it at the star that it wants to go to.

Whats the likelihood that I can polar align, then set it up on just one star once I've got it aligned once on three stars?

Captain Chaos

[Ambermile]

Hi CC

The Park Scope option has nothing to do with the scope remembering where it is wrt the sky and everything to do with remembering where the worms are wrt the gears. It is a PEC thing, not a postition thing, so moving the scope to align next session is no problem.

Arthur

[MartinB]

Great M42 by the way CC

Martin

[Kaptain Klevtsov]

Hi CC

The Park Scope option has nothing to do with the scope remembering where it is wrt the sky and everything to do with remembering where the worms are wrt the gears. It is a PEC thing, not a postition thing, so moving the scope to align next session is no problem.

Arthur

Poo! I thought that if I parked the scope it might remember where it is.

Never mind, Ive got some charts to use now, I know where the Al Quida star is, the Sheraton and even the Maserati Merak!

Captain Chaos

PS wonder if the rain will stop?

[Kaptain Klevtsov]

The boing boing bit is back, and worse still I know it's not gear backlash!

The RA axis is sticking for about 30 degrees of travel. I thought that I'd cured this evil thing but no, its back.

Turns out that I hadn't got rid of it by resetting the backlash in the gears, what I had done is put the 'scope on the other way. This was because a two star alignment had it thinking that some stars were buried when I goto'd them so I guessed it knew which end of the 'scope was the in end. That way the aligning misses the nasty bit on the things I tend to point at. Now that Saturn has moved into the nasty bit the sticking has come back.

Tonight I got some serious twanging in the drive so I took the lid off to watch the gears and use the timing of the boings to get a handle on what's going on. Turned out that the boinging had nothing to do with backlash as the boings weren't in time with any of the periods of the geartrain. By moving the counterweight I stopped the slip, but not the boinging, so I was puzzled. When I came to take the 'scope off I did the "park scope" option and the drive started to slip (brrrrrrrr noise!). I had the lid off so I could see that the slipping was the stepper motor not being able to step (relief!) rather than stripped gears. After shutting down the power I manually put the 'scope where there would be no load on the cogs from the counterweight and took the 'scope off and put it to bed in it's van. After taking off the counterweight I found that the RA axis is stiff to turn at some point which causes the boinging in the tracking.

I will definitely need to take it bits in a serious way to get to the bottom of this, it seems to me that the bearings are too tight or the shaft is bent. As I can't imagine the latter is the case I am hopeful that I can reseat the bearing or just loosen it up a tad.

Any pointers to an exploded diagram of the HEQ5 or pictures of one in bis would be very useful here, as would any experiences of taking one apart. A slice picture (sexual arrangement in technical jargon) would be even better.

After reading what I have written above I have realised that putting the 'scope on the other way wouldn't change this at all, so either I have tried pointing in a direction that I did before (is Saturn where M42 was then? Must check that) when I had the original problem. Putting the 'scope the other way round would take the Dec. axis 180 degrees off, but nothing else.

I'm going to try driving the axis through 180 degrees with the motor tomorrow, then loosening the lock and winding the 'scope back by hand, to see if the stiff bit moves or stays where it is. That will be a clue as to where the stiffness is.

It's fun this, isn't it?

Captain Chaos

[Grant]

I found this, but I have no idea if it matches what you have or if it's any help:

Heres another:

From this site: http://astro.dhis.org/heq5.html

Theres also this: http://www.astrosurf.org/avex/eclate-eq6/disassembling-eq6.html but it's for the eq6, but I wonder if anything is similar for both mounts?

Anyway, hope something there helps,

Good Luck,

Grant

[Kaptain Klevtsov]

thanks guys, I'll check this out after work today.

Captain Chaos

[Kaptain Klevtsov]

Ok now for an update. I got in late from work about 8:30, put the oven on to heat up and fetched the HEQ5 head indoors to have a look at it. RA axis was very sticky all round and the Dec. axis had got sticky. Something is amiss with it!

Oven hot and pizza stuck in, 15 mins to look at yesterday's Saturn AVIs, 15 mins to eat pizza then have a look at the thing next to the diagrams above.

Some of the stickiness has gone, looks like something in there is freezing at low temperatures. Followed the links (above again, gthanks again chaps) and discovered the truth about the awful nasty grease that they put in these things.

Plan A, wait for it to warm up and see if the axes free up. Had a shower, watched Question Time and then tried the mount. Free all the way in both axes. Q.E.D. New grease required this weekend.

Now to get kitted out with some diesel to degrease the cogs, lithium based cold resistant (i.e. not made from dirt disolved in water) grease to get, got the rubber gloves, got a toothbrush to clean the cogs (must get a new one for my teeth).

Will let you know if I mess it up or if it just gets better.

Captain Chaos

[trekker308]

Don't know if this any use to you CC, but there is Yahoo group for the HEQ5 - I belong to the EQ6 group and I've found some of the bits in the 'Files' section to be useful re adjusting mesh etc:-

http://groups.yahoo.com/group/HEQ5/

Best of luck!

[GordonCopestake]

A lot of people buy their grease from Halfords as they sell quality synthetic grease (green goo) for push bikes.

[gaelicstorm7]

Hello CC

Man your in for messy job !. I decided to take my EQ5 to bit's to regrease it..........what the F*** type of grease is used in it ! :shock: , it was like black tar, and stuck like whatsit to a blanket, took ages to remove all traces of it from the relevent surfaces, but eventually got it cleaned off regreased and put back together with no bits left over !, here's a couple of piccy's, on one you can see the worm part of the mechanism with what looks like a little black dog [removed word] of grease still in the same position it was applied to when the mount was first assembled I guess !, unbelievable. Yup was a real mucky, orrible job getting it all off, have tried a grease called M494 Silicone Grease, use it alot at work in scientific equipment, -50-200 deg c operating temp range, low viscosity, non melting, excellent low to medium load characteristics and above all it's free , will see how it performs, worse comes to worse will strip it and regrease with something else, at least this will be much easier to clean off.

Once done the mount was much smoother in operation, not noticed any real improvement in the lengths of exposures I can take but the tracking is much smoother, much less jerky.

Good luck !

Alan

[Kaptain Klevtsov]

More update.

Started taking the RA drive to bits this afternoon so here's what I found.

Problem was:-

With the RA lock released the axis was stiff, especially when cold. This pointed towards the shaft bearings rather than the worm bits as they are stationary when the lock is off. First guess was either the grease freezing or differential expansion of the aluminium casting and the shaft causing extra preload when cold. The coefficients are the wrong way round such that the fit will get looser as the mount cools, so that left freezing grease.

OK the mount has been indoors for 20 hours ish and so should be free. Turned it , yes it's free. Turned it some more, trying to find a "notch" indicating dirt in the bearings, and it got sticky. No notchiness, just increased friction. Thinking the nut may be loose, and that I was increasing the preload on the bearings as the nut tightened because of my turning the shaft, I tried turning the other way. Same thing, stiff all the way round.

Took off the polar scope cover, two rings, a plastic washer, the setting circle (disc) and a further plastic washer. This revealed a disc with two tiny allen grubscrews to hold it. Unlocked the grubscrews and took that off. Took off the setting circle (ring) Underneath is a nut which has three radial notches to take a C spanner. Each notch has a locking grubscrew hiding in the recess. Loosened the grubscrews and loosened the nut. Now it turns freely, no notchiness, and the grease is common or garden type, no black stuff in the taper roller bearing.

Tightened the nut by hand - still free and no discernible play, either radial or axial. Tightened it a bit more using a large allen key in one of the notches - same thing. All back together, all OK. Looking good, seems like too much preload on the bearings may have been to blame.

Playing like a kid with a new toy with my new toy, I turned the RA axis several times and then it stuck! It stuck after I had locked the setting circle ring to stop the screw dropping out and getting lost! Loosening the setting circle freed it off again, so thats the culprit. When loose the ring has definitely got end float so I now need to check what happens inside with the lock screw.

The setting circle ring goes under the plate and I'm wondering if the plate screws down to the nut or has adjustment for the setting circle ring. With the ring lock loose everything is fine, but if I lock it the stiffness is back.

For now I'm going to leave the setting ring loose, might take the lock screw out before it drops out and is lost.

Today's questions are:-

The black grease, is that reserved for the worm drive? (Should I still get in there and clean it, or did they get the message at the factory and start using real grease?)

The plate (with the thread that holds the polar scope cover on), should that be tight to the nut, or with a gap?

Also got the Dec. axis one sussed, the lock level was falling tight which caused the stiffness. holding it up made it free again - phew!

Captain Chaos

[moondog]

CC

It seems to be the case on most HEQ5's that locking the RA circle fastens it to the housing and not to the RA axis.(which you would expect)

I have to leave the RA circle screw loose for the mount to work properly as well. I guess it's a design fault.

The Dec circle works properly, so they ought to be able to fix the RA circle problem.

Perhaps putting some of the thick black gunk that you removed from the gears under the RA circle would make it work properly without using the screw! Good luck with the fix. We'll give you an honorary Engineering degree when you've finished.

MD

[Kaptain Klevtsov]

Found the problem. The RA screw is not for rotating the ring, it only goes (loosely) in one place. There is a hole in the ring for the screw to go through.

If the screw is not in the hole, the screw pushes the setting ring, not against the far side of the machined recess that it fits in, but against the shaft nut. The ring is then locked by the screw on it's outer surface and rubbing on the outer surface of the nut. As the nut is not smooth, the grating happens.

Pictures on the website www.gas.uk.net/HEQ5.

HTH

Captain Chaos

[gaelicstorm7]

Glad you seem to have got things sorted CC, I found the black grease to be throughtout the RA gear train, not just on the worm, the whole thing seemed to have been packed tight with it.

Alan