Need help with my guiding

[RugbyRene]

Hi all,

Well last nights session was yet another in a long lines of wasted nights of imaging. My guiding has never worked properly. A good nights guiding is getting an RMS of 1.9. I polar align, I balance I tweak settings ad nothing seems to work. I'm at the point where I either find a solution and get my guiding under control or I give the whole thing away.

But before I launch into an explanation of my issues I'll describe my equipment & set-up routine:

Equipment

• Mount - SW AZEQ6
• Main Scope - SW Esprit 100
• Main Camera - ASI1600 or 294
• Guide Scope - SW Evoguide 50 (242mm focal length)
• Guide Camera - ASI120mm mini
• Software - KStars/Ekos running on a RPI4
• Guide Software - Internal guider within KStars (though I have tried PHD2 without success

Setup
My nightly routine is as follows:

• Setup tripod and level
• Load up all of my equipment and balance. I balance in DEC first and then in RA (as per Dylan O'Donnell's advice). I find balancing on the AZEQ6 to be a pain as the clutches are quite stiff.
• Once balancing is done I fire up KStars and PA using the internal PA routine.
• I then do a star alignment so the mount knows where it is (don't we have GPS for this?)
• Then slew to my intended target and plate solve.

So far so easy but this is when it starts to all fall apart.

I start my guiding calibration using the internal guider in KStars. I've tried PHD2 but can never get it to work and I figure why use yet another piece of software when KStars does it all.

Yes I know others swear by PHD but I can't get it to work.

After guiding calibration, the mount starts to guide. It's a bit wonky at first so I always let it settle down for a few mins.

DEC is never the problem. My DEC RMS is always around 0.5. It's RA that's the problem but overall my guiding graph is horrible and regularly hangs around 1.8-2.5 RMS. Over the last few nights I've seen some weird things happening. Here's a list of some of the weirdness:

• On a good night I can get 0.8-0.9 RMS...........for about 2 mins. The mount will guide nicely, I'll have a nice smooth graph and then seemingly out of nowhere the RA graph goes crazy and my Total RMS will go to 1, then 2, then 3 then 4 then off the scale and not recover.
• Guiding will start off bad and never get good. My usual night is starting with and RMS of 2.5 and it never getting any better
• Guiding will start and the plot graph will be all over the place. Total RMS will be off the chart and the only thing I can do is stop it and do a recalibration.

So I'm at my wits end and as I said, I'm at the point of giving it all away as I'm fed up wasting hours (not to mention sleep) trying to fix this. I'm hoping the community can help me diagnose my issues. I'm starting to think it's an issue with RA in the mount. Perhaps the worm gear, belt drive or a combination of those and something else.

Yes I realise there's periodic error in RA on most mounts and I've not done PE training yet but will. Though periodic error can't explain some of the weird things I'm seeing like the mount suddenly flying off in RA for no apparently reason or having good guiding then it getting progressively worse and worse.

Thanks in advance for any help you can provide.

Rene

[vlaiv]

Have couple suggestions that you can try - maybe some of it will help:

1. Don't calibrate where you image - calibrate near meridian with DEC close to 0. That way you'll get most precision in RA calibration

2. What is your guide exposure? Don't keep it too short - set it to 2-3 seconds just to minimize the seeing.

3. Is your RA stiff in any way? When you are slewing does it make funny noise on one part of its travel? You say your clutches are pain - what exactly is troubling you? Could it be that they loosen up after some time and mount starts slipping?

Is there any chance there is cable snag or anything like that?

Sudden worsening of guiding can be due to seeing or local thermals. How high in the sky are you trying to image? Are there any sort of surfaces that will give off heat - like paved roads or large bodies of water (pools, ponds, lakes, whatever)? It can also be due to RA axis starting to seize up or slip or something.

[RugbyRene]

5 minutes ago, vlaiv said:

Have couple suggestions that you can try - maybe some of it will help:

1. Don't calibrate where you image - calibrate near meridian with DEC close to 0. That way you'll get most precision in RA calibration

2. What is your guide exposure? Don't keep it too short - set it to 2-3 seconds just to minimize the seeing.

3. Is your RA stiff in any way? When you are slewing does it make funny noise on one part of its travel? You say your clutches are pain - what exactly is troubling you? Could it be that they loosen up after some time and mount starts slipping?

Is there any chance there is cable snag or anything like that?

Sudden worsening of guiding can be due to seeing or local thermals. How high in the sky are you trying to image? Are there any sort of surfaces that will give off heat - like paved roads or large bodies of water (pools, ponds, lakes, whatever)? It can also be due to RA axis starting to seize up or slip or something.

1.  I do normally start calibration where I image so I'll try this suggestion next time

2. I normally expose at 1-1.5 sec. If I go any longer guiding just gets worse, not better.

3. RA isn't stiff (that I can tell). It swings freely when the clutch is released. Though when I tighten the clutch it does nothing as I can still move the mount. I also have some very slight play in RA.

No cable snags. Everything is nicely tucked away. 

It doesn't matter where in the sky I'm imaging, I get the same issues.

Your suggestions are good and I will try then but it doesn't explain why the RA will suddenly fly off and never recover.

Rene

[vlaiv]

1 minute ago, RugbyRene said:

Though when I tighten the clutch it does nothing as I can still move the mount. I also have some very slight play in RA.

This should not happen.

When you tighten the clutch - there should no play in RA and only way you should be able to move your scope is putting tension in the system (mount should resist).

By play I mean motion of the scope without this resistance.

[RugbyRene]

13 minutes ago, vlaiv said:

This should not happen.

When you tighten the clutch - there should no play in RA and only way you should be able to move your scope is putting tension in the system (mount should resist).

By play I mean motion of the scope without this resistance.

The RA clutch has never tightened properly and I've always had play (not much but it's noticeable). I'm taking my mount to my local astronomy store to have it serviced.

[vlaiv]

1 minute ago, RugbyRene said:

The RA clutch has never tightened properly and I've always had play (not much but it's noticeable). I'm taking my mount to my local astronomy store to have it serviced.

I think that would be a good idea.

[newbie alert]

I can help you with phd2 but not within Kstars... couple of questions,  do you pulse guide or st4? If you pulse guide then Vlaiv is quite correct on calibration on dec 0, meridian intersection. . But if you use a st4 you should calibrate very near the target and after any flip..

Have you run the guiding assistant 

What did your calibration look like?

Any images of your guide graph?

[RugbyRene]

On 24/01/2021 at 20:54, newbie alert said:

I can help you with phd2 but not within Kstars... couple of questions,  do you pulse guide or st4? If you pulse guide then Vlaiv is quite correct on calibration on dec 0, meridian intersection. . But if you use a st4 you should calibrate very near the target and after any flip..

Have you run the guiding assistant 

What did your calibration look like?

Any images of your guide graph?

I use ST4 guiding and always calibrate on or near the target. I’ve never heard of guiding in another part of the sky and then going to your target. I’ve not been able to image for a while due to the bad weather here in Sydney.

I’ve heard about pulse guiding but don’t understand how it works. Could someone explain it simply?  If it’s more accurate then I’d like to give it a go.

Rene

[Seelive]

I believe that with ST4 guiding, the guiding software is completely unaware as to where the telescope is pointing so it is necessary to calibrate near to the target to get the best guiding results. When the guide software connects directly to the mount, the guide software is aware of the telescope's position so in theory you should be able to calibrate at any sky location and the guiding software will automatically adjust the guiding rates for your chosen target (but normally calibration near the celestial equator gives the best results).

[Merlin66]

When using the ST-4 connection, If you enter your mount details in the PHD box "Aux Mount" it will communicate the mount position to PHD2.

This is the set-up I successfully use with my C11 (for spectroscopy) on the HEQ6 mount.

Works well for me.

 

[newbie alert]

I've  only ever pulse guided, benefits are once you've calibrated you don't need to every time  you start up, and you don't need to re calibrate every target change or after a flip like you do with st4

[Adam1234]

Agree about calibrating near the meridian with dec near to 0. 

As soon as I started doing this my guiding was miles better going from over 1rms to about 0.5. 

I think also taking the time to ensure that my guide scope was in focus was a huge contributing factor too.

 

Adam 

[Merlin66]

I don't have to recalibrate at each session or when changing target.

The ST-4 connection just works for me. Not sure what bad experience you may have had with ST-4 connections.........