PHD2 Guide Graph advice

[dyfiastro]

Hi everyone

I am currently out imaging for the first time and watching the graph. I had a bit of a headache getting to this stage as it seemed all over the place but would like any advice and input.
Does the graph look ok or can anyone see anything wrong / ways to improve?
I notice everything seems calm and every so often a get some strange spiking.

Any thoughts and input would be great.

[Mike Hawtin]

Your second screenshot clearly shows declination backlash, you can see the dec trace drifting up and PHD sending corrections but they are unable to stop the drift until the backlash is overcome.  You will need to adjust the dec worm engagement to minimise the play in the gears or consider guiding dec in one direction only.  As for the spiking it would be useful to know what mount you are using and the load it is carrying, how well you are polar aligned, balance (East/West biased or neutral) and what the conditions were when you took the screenshots etc.

 

Mike

[dyfiastro]

2 hours ago, Mike Hawtin said:

Your second screenshot clearly shows declination backlash, you can see the dec trace drifting up and PHD sending corrections but they are unable to stop the drift until the backlash is overcome.  You will need to adjust the dec worm engagement to minimise the play in the gears or consider guiding dec in one direction only.  As for the spiking it would be useful to know what mount you are using and the load it is carrying, how well you are polar aligned, balance (East/West biased or neutral) and what the conditions were when you took the screenshots etc.

 

Mike

Thanks for the reply.

I am using a heq5 pro synscan with the upgraded belt drive. I had a 130pds, 9x50, qhy5l-iim and a fuji xt1 attached.

It was well balanced and there was only a very slight breeze. When I drift aligned both directions.came out below 1 arc minute (I think that is what it was saying)

[Mike Hawtin]

I've not used an heq5 so I can't say if your RA guiding is normal or not, I do know that on my AZ-EQ6 I have small spikes of +/- 1" in RA and that they occur in the same place in the worm cycle and give me a rms figure of 0.5"  in RA at zero degrees Dec so I should imagine that there is room for improvement on your mount although what you have now does not look disastrous.  What I have found on my mount is the suggested figures put out by the "guiding assistant" tool for min movement and backlash compensation always result in a much worse guide graph.  I would suggest you keep to a one second guide cycle to start with and set RA and Dec aggression to 100, Hysteresis and MinMo on both axes to 0.01 and see how you get on at that, the 0.01 value is not a mistake, I've found that setting a zero value inhibits corrections for some reason at least in Dec.  The received wisdom is that these settings will result in the mount "chasing the seeing" but they work very well for me.  I will up the guide cycle to two seconds if the seeing is poor and drop the aggression settings when guiding at higher declination to smooth things out a bit but that is all I change.  I'm afraid that it is very much a case of trial and error with these mounts and when making changes to your settings try to alter just one thing at a time to avoid confusion, also don't overlook the guide rate settings you are using, some mounts need a high rate and some respond better to a lower one, my mount works well at 0.3x sidereal.

 

Mike

[Skipper Billy]

1 hour ago, digitalcyanide said:

Thanks for the reply.

I am using a heq5 pro synscan with the upgraded belt drive. I had a 130pds, 9x50, qhy5l-iim and a fuji xt1 attached.

It was well balanced and there was only a very slight breeze. When I drift aligned both directions.came out below 1 arc minute (I think that is what it was saying)

The belt drive kit doesn't help remove backlash from the worm drives - only the primary gears - a good read through this should help you get rid of the backlash in the worm drive.

http://www.astro-baby.com/heq5-rebuild/heq5-m1.htm

Also, unbalancing the rig slightly will help - make sure the rising side is the heavy side so that the gears are always meshed. It sounds simple but creates havoc when you do a meridian flip - the best cure is to get rid of the backlash following the guide above (no pun intended )!

 

[Skipper Billy]

PS - I have a very similar setup and with a bit of patience you can get the graph a lot flatter .....

 

[Skipper Billy]

Increasing your exposure time may help - at 1 sec. you might be 'chasing the seeing' - try 3 or 4 seconds - it might help.

[cfpendock]

16 minutes ago, Skipper Billy said:

Increasing your exposure time may help - at 1 sec. you might be 'chasing the seeing' - try 3 or 4 seconds - it might help.

Exactly.

Chris

[Andyb90]

I tried more precise balancing on my belt modded HEQ5 the other night and the graph was all over the place.

So I think the advice to unbalance is good. I'll be reverting back to that next session.

I've bottled it a bit on the full strip down, so I'm getting the mount serviced by Astrotec UK.

Andy.

[dyfiastro]

Thanks for info everyone, I will take aloof at getting everything tighter tonight and unbalance it a little  I am yet to take a look at my first set of images which I took last night so will see what they are like tonight.

 

Thanks again

[Skipper Billy]

On 5/4/2016 at 15:36, digitalcyanide said:

Thanks for info everyone, I will take aloof at getting everything tighter tonight and unbalance it a little  I am yet to take a look at my first set of images which I took last night so will see what they are like tonight.

 

Thanks again

There's a bit more to it than tightening everything - its adjusting until its free of play but not binding - it can take a while to get it spot on - decent Allen keys and a swear box usually help :-)