Az -Eq6 strip down

[oymd]

3 minutes ago, wimvb said:

They are the top screws in your own image, and indicated in @david_taurus83 first image

Oh, of course. Yes. Those are the DEC screws of course. The RA is on the back. Sorry. I’m an idiot!!

[wimvb]

2 minutes ago, oymd said:

And should I start with DEC then RA, or it doesn’t matter?

RA is always engaged and moving in the same direction. That's why backlash is less important in RA. But it helps to have a slightly east heavy imbalance to help keep the gear cogs engaged.

There's no need to take the scope off. But I wouldn't put a heavy load on it either. To use my method with Guiding Assistant, you need at least a guide scope with camera on the mount.

[wimvb]

You can just see one RA allen screw near the bottom here (not indicated, but next to the cable).

[oymd]

1 minute ago, wimvb said:

You can just see one RA allen screw near the bottom here (not indicated, but next to the cable).

Yes, sorry. I get it now. 
 

By the way, I never really understood what EAST heavy meant?

Does that mean that when balancing RA, with the counterweight shaft horizontal, the scope should be HEAVIER on the EAST (right) side of the mount?

But wouldn’t that still make the scope heavier on the WEST side of the mount as well when I swing the OTA around?

How can the OTA and all the imaging gear be heavier on just ONE side (EAST) of the mount?

Sorry, pretty sure it’s another dumb question, but it’s one I don’t understand. 

[wimvb]

That's actually a very valid question. East heavy implies that you need to adjust the balance of the scope/counter weights after doing a flip. When imaging towards the East, the scope is on the West side of the pier, and the counter weights on the East side. The counter weights should be slightly further out than perfect balance. After the meridian flip, you are imaging towards the West. The scope is on the East side of the pier and the counter weights on the West side. Now the scope side needs to be heavier, so the counter weights need to be shifted up the counter weight bar.

In practice, you try to get a good balance with as little backlash as possible. You then accept a small difference in guiding/tracking accuracy between East and West. Or you can just do your imaging on one side. If you decide to image just East of the meridian, you switch to another target when the first one passes the meridian.

[bluesilver]

This is a very interesting and detail instructions around backlash.

What i have done and i am guessing i have done it incorrect,

But i kind of adjusted my backlash when everything was off the mount, 

I removed the belt and I just adjusted those grub screws so that everything was tight and bound up,  then i just loosened then a bit by bit until i could move the main gear cog with my finger and kept on adjusting until i got rid of the backlash, just buy trying to to move the mount head by hand.

I haven't played around with that worm end float though, ( the large screw in behind those black plastic covers that adjust the pressure on the worm gear bearings )

I haven't tried the backlash movement when it is loaded up with all the gear on it yet though.

I always thought that if you couldn't move that main gear cog by your finger it was too tight and binding too hard.

Have it got it all wrong and need to tighten it up more or adjust the pressure on the worm drive bearing more?

 

[wimvb]

5 hours ago, bluesilver said:

Have it got it all wrong and need to tighten it up more or adjust the pressure on the worm drive bearing more?

Use the PHD guiding assistant first to see if you have a problem. "If it ain't broke, don't try to fix it."

[david_taurus83]

I never bothered with the east heavy thing. It takes long enough to setup each time and get PHD calibrated, ensuring a meridian flip goes smoothly etc, without having to faff about with counterweights again and risking upsetting everything at 1am! Besides, I reckon I can move the counterweight 2 or 3 inches on my current mount without it swinging one way or the other, such is the gunk SW use to grease the mounts.

[oymd]

12 hours ago, wimvb said:

That's actually a very valid question. East heavy implies that you need to adjust the balance of the scope/counter weights after doing a flip. When imaging towards the East, the scope is on the West side of the pier, and the counter weights on the East side. The counter weights should be slightly further out than perfect balance. After the meridian flip, you are imaging towards the West. The scope is on the East side of the pier and the counter weights on the West side. Now the scope side needs to be heavier, so the counter weights need to be shifted up the counter weight bar.

In practice, you try to get a good balance with as little backlash as possible. You then accept a small difference in guiding/tracking accuracy between East and West. Or you can just do your imaging on one side. If you decide to image just East of the meridian, you switch to another target when the first one passes the meridian.

oh, wow...really?

So, with the east side heavy thing, when imaging EAST of the Meridian BEFORE the flip, the counter weights should be ever so slightly heavier?

Then as the mount flips and starts to image WEST of the meridian the OTA should be ever so slightly heavier?

Which implies that someone has to be physically present beside the mount AFTER the flip, stop the tracking, and change the balance? Is that what experienced imagers do?

Or, if you just do not want to be near the scope so late at night, one would assume that we make the counter weight side ever so slightly heavier, and DO NOT image past the meridian?

So what do imagers do with regards to REMOTE locations? Is this weight shift done remotely?

Very interesting.

[wimvb]

25 minutes ago, oymd said:

Is that what experienced imagers do?

Not really. The very best have high end mounts that need perfect balance. And as @david_taurus83 already wrote, most mounts aren’t that sensitive to balance. In many a mount, the problem is solved with grease. But you may experience a difference in guiding. It’s a case of ”don’t sweat the small stuff”. If you do an automated meridian flip, you can’t even rebalance the mount. I know I don’t. If I find that for some reason the guiding is unacceptable on one side of the meridian, I image on the other side only and figure out what went wrong the day after. Or I collect RGB on the side with poorer guiding, and luminance on the good side.

[oymd]

On 19/09/2021 at 16:11, wimvb said:

Yes. You can apply calibration at any declination, but PHD doesn't like it to be too high. There is a difference between DEC and Altitude. DEC is a number of degrees north of the celestial equator. Altitude is the number or degrees above the horizon. For me at 60 degrees latitude, the celestial equator is at an altitude of 30 degrees above the horizon (due south). This is also DEC 0 degrees. You can safely do your calibration some 10 - 15 degrees north of the celestial equator (for me this is an altitude of 40 - 45 degrees, when looking South). This may even be better, because if you calibrate too low (above your local Southern horizon), you well get a larger effect of the atmosphere and more seeing related problems.

Below your horizon sounds strange. in the Northern hemisphere, the altitude (degrees above the horizon) is always

(90 - your Latitude) + DEC

As I wrote before: for me an object is at altitude 30 + DEC, because I live at a Latitude of 60 degrees. If you live at a Latitude of 50 degrees, the altitude of an object is 40 + DEC. Normally you calibrate at or close to DEC = 0 (the celestial equator), which is at a local altitude of 90 - your Latitude.

Objects with a Declination (DEC) that is higher than your Altitude, are always North. Zenith (pointing straight up) has a declination which is equal to your local Latitude.

According to your Avatar information, you are located in or near London, which is at a latitude of 51 - 52 degrees. So, you would do your PHD calibration at an altitude of 38 - 39 degrees above the horizon. If you have bad local atmospheric conditions, you can calibrate at 45 - 50 degrees altitude, which is at a declination of 6 - 12 degrees.

Thanks wimvb for that...very informative.

Can you then please clarify why I see such VERY high DEC readings in my Stellarium.

Tonight I tried calibrating again, and I got the message: Failed, RA star did not move enough?

I think I need to sort my RA and DEC backlash. I will do that over next weekend, as there was simply no time today. I just loaded my existing calibration data, and I am currently guiding at 0.5-0.7rms, which is not bad.

Can you please clarify why those DEC values are so HIGH when my counter weight bar is HORIZONTAL, and the telescope is JUST FEW DEGREES pointing upwards from being also completely HORIZONTAL and parallel to the ground?

I was practically pointing at just above the treeline (basically tall bushes, not even real trees) pointing NORTH in my garden to try to calibrate. Pointing really low, yet DEC values are so HIGH?

P.S. I am currently away from London, at latitude 30.

Edited September 20, 2021 by oymd

[wimvb]

58 minutes ago, oymd said:

Can you then please clarify why I see such VERY high DEC readings in my Stellarium.

The explanation I gave you is when you look due South. When looking due North (as in your images), the celestial equator is below the horizon, by the same amount it is above the horizon when looking South. Dec is the angle from the celestial equator towards the polestar. If you are 51 degrees latitude, the cel equator is 39 deg below the horizon in the North, and a star with declination of 69 degrees, will be 30 degrees above the horizon. The Polestar is your latitude in degrees above the Northern horizon.

Your 2nd image with HIP 47193 shows a declination of 81 degrees and an altitude of 21 degrees. The difference of 60 degrees is the amount that the cel equator is below your Northern horizon. This means that your location (latitude) is 90 - 60 = 30 degrees.

When you look due East or West, the celestial equator crosses the horizon, which means that DEC and altitude will be the same. From this it follows that the altitude of an object with a given declination depends on the azimuth angle (compass direction).

Did you do the phd calibration with your telescope pointing to the south and near the meridian (assuming you are in the northern hemisphere)?

Edited September 20, 2021 by wimvb

[oymd]

8 hours ago, wimvb said:

The explanation I gave you is when you look due South. When looking due North (as in your images), the celestial equator is below the horizon, by the same amount it is above the horizon when looking South. Dec is the angle from the celestial equator towards the polestar. If you are 51 degrees latitude, the cel equator is 39 deg below the horizon in the North, and a star with declination of 69 degrees, will be 30 degrees above the horizon. The Polestar is your latitude in degrees above the Northern horizon.

Your 2nd image with HIP 47193 shows a declination of 81 degrees and an altitude of 21 degrees. The difference of 60 degrees is the amount that the cel equator is below your Northern horizon. This means that your location (latitude) is 90 - 60 = 30 degrees.

When you look due East or West, the celestial equator crosses the horizon, which means that DEC and altitude will be the same. From this it follows that the altitude of an object with a given declination depends on the azimuth angle (compass direction).

Did you do the phd calibration with your telescope pointing to the south and near the meridian (assuming you are in the northern hemisphere)?

Amazing information wimvb!!!

Ive learnt a lot from your answers!!
 

The south side of my garden had considerably higher bushes than the north side, so I always pointed and calibrated NORTH. Our neighbours are south of us, and they like to grow their trees really HIGH for privacy. The trees are about 3 meters high, so I always tried calibrating while pointing NORTH where I can see more of the horizon. 
 

Ok, I get your point. 
 

Tonight I will move my setup all the way to the NORTH of our garden, so that I can have a better and lower view of the SOUTH sky and try the calibration again. 
 

Ive also read on a thread in Cloudy Nights from 2018 that the possible cause of the error I get: Calobration failed. RA star did nit move enough, might be due to some setting in PHD2 where I should change the setting to move the mount MORE with every calibration step?

Thanks again!!

[oymd]

On 19/09/2021 at 12:26, wimvb said:

This is what I wrote on the Facebook group for EQ6 owners:

 I managed to get the backlash down  from 4000+ ms to about 1300 ms. As it may be of interest to others, here's a description of what I did:

1. Point the telescope just east of the meridian and just north of the celestial equator.

2. Calibrate guiding, guide for about a minute just to stabelise the tracking, apply guiding assistant and measured backlash.

3. Park the scope (pointing north) and loosen the South grub screw. Tighten the North grubscrew about 1/32 of a turn.

Repeat steps 1 - 3.

When I tried to get backlash below 1000 ms, the gears started to bind. Just backing off a tiny bit, didn't really improve things. I also found that it's important to tighten everything in the right order. Tightening the South grub screw before tightening the allen screws that keep the DEC in place, changes the gear meshing just a tiny bit. Enough to change backlash. So I always tightened the allen screws first, before I tightened the South grub screw. I think there's also some hysteresis in the mechanics, and when the gears start to bind, it may be easier to loosen everything and start over, rather than trying to go back in small adjustments.

 

 

And some time later:

A final update:

Tonight is a clear night after several days of rain, but with poor seeing. I opened my observatory to continue tuning backlash. Last time I tuned backlash too far and the mount started to bind. So I backed off a bit before closing up, expecting to have to repeat the entire exercise. But, lo and behold, without any adjustments, guiding assistant measured 248 ms (!). I let it guide for a while and ran guiding assistant again: 314 ms. I'm very happy with that. I will check backlash again when the air is more stable, but for now I'm very happy with this result.

 

Note: the 248 ms and 314 ms backlash was measured at a guiding rate of 0.8 x sidereal. when I measured backlash a few days after I wrote this post, I did so at my normal guiding rate of 0.5 x sidereal, and it was 700 ms.

This image is from during the first night of adjustments

This image is after the last adjustments

 

Btw, if you can feel a wobble in DEC or RA, your backlash is way off. At 4000 ms backlash, I couldn't feel it when I tried to move the axis by hand.

 

Edit:

One more thing you can do: Guide for at least half an hour. Don't change any settings. After that, download the guide log from PHD and look at it in PHD log viewer. Do a frequency analysis of the RA errors. 

This is the kind of graph I mean:

The peak at 480 s is the main period of the worm gear. The 120 s peak is from the RA pulley on the worm side. The very small peak at 10 s is from the RA motor pulley. If you have a high peak here, it will be very difficult to guide out, and you will need to adjust the pulley. All the other peaks will be guided out without any problem. I had this problem two years ago and had to tighten the RA belt. That solved it.

High Wim

I'm planning on doing this BACKLASH fix this weekend.

Yesterday night I started following your steps, but was stuck at Step 3

When I open guiding assistant in PHD2, I cannot click any of the buttons. START & STOP are greyed out?

[wimvb]

Are you guiding when you start the guiding assistant?

[oymd]

43 minutes ago, wimvb said:

Are you guiding when you start the guiding assistant?

Yes. PHD2 was already guiding

[wimvb]

I haven't had this problem, so had to look it up. The only reference I found was this

https://openphdguiding.org/man-dev/Tools.htm#Guiding_Assistant

But if guiding was active, guiding assistant should run.

[oymd]

On 08/10/2021 at 19:59, wimvb said:

I haven't had this problem, so had to look it up. The only reference I found was this

https://openphdguiding.org/man-dev/Tools.htm#Guiding_Assistant

But if guiding was active, guiding assistant should run.

 

On 08/10/2021 at 16:12, wimvb said:

Are you guiding when you start the guiding assistant?

Hi Wim

So, I did the DEC backlash thing.

Was terrified frankly to damage something.

My main guide was to FEEL no more wobble or play in my losmandy dovetail.

I loosened the allen screws, turned the north grub CCW slightly, then the south grub CW slightly. The dovetail immediately became FIXED, with NO play or wobble. Connected the handset, and did a full NSWE slew, and at the extreme there was binding in one of the axis.

I turned the SOUTH grub ever so slightly back CCW, still no play in the dovetail, and NO binding.

Then tightened the allen keys.

There are NO instructions on the RA axis, as to which one to tighten and which one to loosen, CCW or CW, north or south grub first, so left that alone.

Ran Guiding assistant tonight, but pointed at POLARIS, and I think it did not go well.

I am not sure what to make of the result? Especially the measured DEC Backlash?

I applied the TWO recommendations on MINMO to 0.1 each.

I'm now imaging IC 1318, and I've attached my PHD2 view.

For the first few minutes my RA guiding was at 4.0!!! But then it settled down?

This is FAR FAR more complicated than I thought.

Many thanks

[oymd]

On the other hand, I think the stars look OK in the actual image?

Image zoomed in at 140%

[wimvb]

14 hours ago, oymd said:

turned the north grub CCW slightly, then the south grub CW slightly

This will actually increase backlash. The DEC worm is at the south side of the mount when it is in its parked position. If you the turn the North grub screw counter clockwise, you loosen it. The grub screw will move towards you (North) and away from the worm assembly. This image from Astrobaby's guide shows what I mean. The North grub screw is the one on the right. The South grub screw is the one on the left. The small blue arrow indicates that the left screw is being tightened (clockwise). The large blue arrow shows the movement of the DEC worm housing (dotted line). The DEC worm is fixed in this housing, so it will move to the left as well, coming loose from the main DEC wheel. The main DEC wheel (brass colour) is stationary.

When you tighten the North grub screw, the opposite movement happens.

The DEC housing with the gray worm moves to the right, decreasing backlash. In the picture all brass coloured objects are fixed. If you tighten the right hand side grub screw (small red arrow), you would normally screw it in. But since it already pushes against the brass pin, it will actually pull the entire housing, together with the gray worm, towards the right. This pushes the worm against the DEC wheel.

You always start in a position where you have  backlash which you can barely feel. From that point on, only make very small adjustments.

You should run guiding assistant with the scope pointing South, not towards Polaris. Near Polaris it is impossible to guide, because it is where all RA lines "come together". So, you calibrate and use guiding assistant with the scope pointing South, but adjust backlash with the scope parked and pointing North. The latter isn't really necessary, but it makes talking about North and South grub screws a lot less confusing. When you use the guiding assistant, you should have the allen screws tightened because they keep the DEC assembly fixed. Without that, the whole DEC assembly is floating, and you can't measure a reliable backlash value. The procedure is

• Park scope (looking North)
• Loosen 4 DEC Allen screws a little, so the DEC assembly can move freely
• Loosen South grub screw, ccw
• Tighten North grub screw, cw, 1/32 of a turn
• Tighten Allen screws
• (Optionally) tighten South grub screw, cw
• Slew South to Meridian
• Run Guiding assistant & measure backlash

Repeat

Edited October 10, 2021 by wimvb

[wimvb]

14 hours ago, oymd said:

On the other hand, I think the stars look OK in the actual image?

Image zoomed in at 140%

Stars do look good in the image. You can also see that your DEC guide pulses (red) are all in the same direction. As long as they are, the DEC axis never needs to reverse direction, and you won't notice DEC backlash. You also have a total guiding error of only 0.53 arc seconds, which is very good. I would suggest you leave the DEC assembly where it is. " if it ain't broke, don't try to fix it" applies here. But if you do get jumps or erratic behaviour in DEC, you know where to start looking.

have a look at the Polar Alignment Error. 767472.4 arcminutes make no sense (there are only 21600 arc minutes in a full circle, 360 degrees). This is an indication that the guiding assistant results are not valid. Probably because you were pointing due North.

And that's why this isn't valid either.

 

[oymd]

3 hours ago, wimvb said:

Stars do look good in the image. You can also see that your DEC guide pulses (red) are all in the same direction. As long as they are, the DEC axis never needs to reverse direction, and you won't notice DEC backlash. You also have a total guiding error of only 0.53 arc seconds, which is very good. I would suggest you leave the DEC assembly where it is. " if it ain't broke, don't try to fix it" applies here. But if you do get jumps or erratic behaviour in DEC, you know where to start looking.

have a look at the Polar Alignment Error. 767472.4 arcminutes make no sense (there are only 21600 arc minutes in a full circle, 360 degrees). This is an indication that the guiding assistant results are not valid. Probably because you were pointing due North.

And that's why this isn't valid either.

 

Amazing Wim. Thanks so much. 
 

Ok, since you think my guiding overall is OKish, I’ll leave the Dec housing for now, but will save your instructions just In case I need to go back to it. 

Can you please provide instructions for the RA backlash fix?

Tonight, I’ll point the scope SOUTH, and run guiding assistant and report back here. 
 

My problem with south is that the trees on the south side are really HIGH, about 6 meters high, so there isn’t a clear patch of sky to point too. I will also need to move the scope and mount  ALL THE WAY to the North side of the garden to expose more of the south sky. Which will make my initial setup a problem, as I will not be able to PA using the IOptron iPolar, as the mount and scope will be all the way on the north side of the garden tucked underneath the bushes, and I will have no line of sight to Polaris? Is there a way to PA WITHOUT direct sight of Polaris and north sky? 

thanks again. 

Edited October 10, 2021 by oymd

[wimvb]

4 hours ago, oymd said:

Is there a way to PA WITHOUT direct sight of Polaris and north sky? 

Synscan hand controllers have a built in all star polar alignment tool. But if your mount is level, and you make sure it's level onnthe new lication, you shouldn 't need to change altitude at least.  Use a compass to get azimuth approximately right. In the ballpark may be enough.

4 hours ago, oymd said:

Can you please provide instructions for the RA backlash fix?

As long as you use a guide rate less than 1, RA will never change direction and backlash reduction isn't necessary. That's why there is no backlash routine in phd for RA. You decrease backlash by feel first, as you did in DEC.  On the outside of the mount housing there are smal round black covers, behind which is the worm gear. Two covers (one on each side) near the DEC gear and two near the RA gear. The backlash assembly grub screws are on the sides between these covers. The grub screw nearest the covers will back off the worm when tightened.

See the photos in this thread.

 

[bottletopburly]

Graham has done a strip down on my Eq6 pro 

 

[oymd]

On 10/10/2021 at 19:39, wimvb said:

Synscan hand controllers have a built in all star polar alignment tool. But if your mount is level, and you make sure it's level onnthe new lication, you shouldn 't need to change altitude at least.  Use a compass to get azimuth approximately right. In the ballpark may be enough.

As long as you use a guide rate less than 1, RA will never change direction and backlash reduction isn't necessary. That's why there is no backlash routine in phd for RA. You decrease backlash by feel first, as you did in DEC.  On the outside of the mount housing there are smal round black covers, behind which is the worm gear. Two covers (one on each side) near the DEC gear and two near the RA gear. The backlash assembly grub screws are on the sides between these covers. The grub screw nearest the covers will back off the worm when tightened.

See the photos in this thread.

 

Good morning Wim

PLEASE help me if possible on the thread I started regarding a stuck DEC axis.

I have imaged SEVERAL TARGETS over at least THREE months following adjusting the backlash, with excellent results.

The WO Star 71 has been on the mount for about a year with ZERO issues.

Yesterday, I put the Esprit 100ED on the mount, and obviously had to RE-BALANCE.

The DEC is stuck?

The mount and WO scope was stored safely in a warm room for 4 weeks while I was away on travel. My last imaging session was 22nd November, and everything was working perfectly?!

NO ONE TOUCHED THE MOUNT WHILE I WAS AWAY?