SCT Drive Training for imaging?

[Hicks]

I've just finished sorting out an issue with the Dec gear of my LX90 and after putting it back together did the usual drive training on a terrestrial object to account for the changes.

As I mostly use my scope for imaging and the imaging setup has a slightly different impact on the scopes balance, would it be worth training the drives with the imaging setup on instead of the visual setup? Or as long as the scope is balanced with each setup would there be little real difference?

Edited December 2, 2016 by Hicks

[Davey-T]

If you mean the PEC training for imaging , you only do it on the RA drive, if you're guiding using PHD or similar to keep the guide star centred is easier than using an eyepiece.

Never seemed to make any difference to mine though.

Dave

[SkyBound]

Never made much difference to mine either, but, I have always had my backlash compensation setting on zero, when guiding using PHD, it works much better, also as you say just make sure the rig is perfectly balanced with all kit on, this is very important on these scopes, as the gears can't cope very well at all with an unbalanced scope.

i have mine balanced in all axis on my bench and have marks on the balance weight rail underneath so I just slide weights forward to back and screw up or down the threaded shaft the weights are on, depending on the rig I am using, took a while to do on the bench but makes it so much easier outside.

[Davey-T]

I usually balance mine aimed at the area I'm planning to image.

Dave

[SkyBound]

3 minutes ago, Davey-T said:

I usually balance mine aimed at the area I'm planning to image.

Dave

Once did it's balanced in all axis it doesn't really matter where the scope is pointed, it will be balanced...

[Davey-T]

1 minute ago, SkyBound said:

Once did it's balanced in all axis it doesn't really matter where the scope is pointed, it will be balanced...

Got rather a lot of stuff piggy backed on mine so it affects it when it passes the meridian.

Dave

[SkyBound]

Just now, Davey-T said:

Got rather a lot of stuff piggy backed on mine so it affects it when it passes the meridian.

Dave

Yes me too, I always balance with the scope tube pointing straight up with all the kit on, and in the horizontal position too, it only takes the softest touch to move mine in any direction as it is balanced so perfectly, then when the wire loom is added that gives it a little bias on the north / south direction to keep the gears engaged, and the handset sits on the one fork arm to give some bias in that East direction too

[Davey-T]

2 minutes ago, SkyBound said:

Yes me too, I always balance with the scope tube pointing straight up with all the kit on, and in the horizontal position too, it only takes the softest touch to move mine in any direction as it is balanced so perfectly, then when the wire loom is added that gives it a little bias on the north / south direction to keep the gears engaged, and the handset sits on the one fork arm to give some bias in that East direction too

A post by Dr Clay somewhere on balancing Meade SCT on wedge says to balance straight up then rotate east in RA  and rebalance.

Dave

[Hicks]

51 minutes ago, Davey-T said:

If you mean the PEC training for imaging , you only do it on the RA drive, if you're guiding using PHD or similar to keep the guide star centred is easier than using an eyepiece.

 

I didn't mean PEC no. There's an option in the Autostar on the LX90 where you center a terrestrial object, then the scope slews left in RA and asks you to only use one direction to re-center, then it slews right in RA and asks you to use only the opposite direction. Same for Dec. I think it's so the Autostar can work out how much backlash may be in the gearing.

For now I've just trained using my balanced visual setup. I'll see how well it fairs and if there still seems to be issues I'll try to redo it with the full imaging setup.

Does seem to have made quite a difference though. Managed to drop the Dec % down from an excessive 40% to just 15% and RA is at 0%. In both cases I can now finally use the 1x guide speed on the handset and see it change direction without waiting an eternity. Hopefully this helps improve my guiding next session

[Davey-T]

I thought that only affected the pointing accuracy ?

Balance advice.

Dave

 

[Hicks]

2 minutes ago, Davey-T said:

I thought that only affected the pointing accuracy ?

I'm not sure, but if that's the case then I should be fine with the training I did using my visual setup.

Cheers for the balancing info, I'll give that a go later tonight (indoors since it's cloudy again...)

[SkyBound]

38 minutes ago, Hicks said:

I didn't mean PEC no. There's an option in the Autostar on the LX90 where you center a terrestrial object, then the scope slews left in RA and asks you to only use one direction to re-center, then it slews right in RA and asks you to use only the opposite direction. Same for Dec. I think it's so the Autostar can work out how much backlash may be in the gearing.

For now I've just trained using my balanced visual setup. I'll see how well it fairs and if there still seems to be issues I'll try to redo it with the full imaging setup.

Does seem to have made quite a difference though. Managed to drop the Dec % down from an excessive 40% to just 15% and RA is at 0%. In both cases I can now finally use the 1x guide speed on the handset and see it change direction without waiting an eternity. Hopefully this helps improve my guiding next session

When using PHD then that sets all the guide speeds for you, but you must have the backlash compensation setting in the handset on "0" when guiding with PHD, that much I do know, otherwise it interferes with the guide commands.

so not sure what you mean by using the 1x guide speed, I have never used that when guiding, I leave that to PHD, and have had perfect subs of 15 mins..  

[SkyBound]

39 minutes ago, Davey-T said:

I thought that only affected the pointing accuracy ?

Balance advice.

Dave

 

That is exactly what I do, except I do it from on a bench in my workshop, it makes no difference whether it's done outside on the wedge or inside with wedge fixed to bench..  or even if done just on tripod without wedge to be honest, as the balance is the same to achieve.

Actually in my method you can't do step 9, that has to be done on the wedge, and can't be done in Alt AZ mode on the tripod without wedge.. but the rest of it can

Edited December 2, 2016 by SkyBound

[Davey-T]

9 minutes ago, SkyBound said:

When using PHD then that sets all the guide speeds for you, but you must have the backlash compensation setting in the handset on "0" when guiding with PHD, that much I do know, otherwise it interferes with the guide commands.

so not sure what you mean by using the 1x guide speed, I have never used that when guiding, I leave that to PHD, and have had perfect subs of 15 mins..  

Guide speed is normally set to X 1  you can alter it to respond quicker to guider input but all that does is take up the backlash quicker, doesn't improve guiding, opposite in fact.

Dave

[Davey-T]

5 minutes ago, SkyBound said:

That is exactly what I do, except I do it from on a bench in my workshop, it makes no difference whether it's done outside on the wedge or inside with wedge fixed to bench..  or even if done just on tripod without wedge to be honest, as the balance is the same to achieve.

Mines permanently mounted in the obsy but I still need to adjust the balance when imaging high / low in the east.

Dave

[SkyBound]

1 minute ago, Davey-T said:

Mines permanently mounted in the obsy but I still need to adjust the balance when imaging high / low in the east.

Dave

Hmmmm, wish I had an obsy.... very jealous indeed ?

[Davey-T]

I usually set up and check the balance when aimed at the target then run PHD to check guide corrections, ie; all north or all south then adjust balance to correct, it's very finicky imaging at 2500 f/l  

Dave

[Hicks]

1 hour ago, SkyBound said:

When using PHD then that sets all the guide speeds for you, but you must have the backlash compensation setting in the handset on "0" when guiding with PHD, that much I do know, otherwise it interferes with the guide commands.
 

so not sure what you mean by using the 1x guide speed, I have never used that when guiding, I leave that to PHD, and have had perfect subs of 15 mins..  

For 1x I was referring to the slowest speed on the handset controller which has 1-9 speed settings with the lowest referred to as guide speed on the LCD display anyway. I think (but don't quote me) the LX90 when used for guiding in pulse mode actually runs at 0.5x sidereal?

Anyhow, my purpose for retraining was that the Dec axis had significant backlash to the point the guide software never really managed to change direction and when I tried to use the handset for visual observation, the 1 and 2 speed settings wouldn't reverse for a pretty long time. I've fixed up the Dec slop now (worm gear pivot issue) and after retraining I was using the reduction in Dec Percent from 40% to 15% whilst now also seeing even at 1x speed the scope respond to a change in Dec slew direction in a short period of time as a sign of improvement.

I don't use PHD for guiding, currently using Linguider, however I wonder if that too would benefit from 0% setting. I do have RA set at 0% already, there's no obvious backlash and the scope seems quite responsive, but the Dec axis is set to 15% to allow reversal in a reasonable amount of time at slower speeds. Not sure if the Autostar applies those % values when you use pulse mode or only if it applies when using the handset itself?

Either way, the Dec axis slop removal should bring some benefit (I hope )even if the percentage is ignored during  pulse mode guiding.

Edited December 2, 2016 by Hicks