Guiding fine then suddenly blows out

[jase.film]

I am jumping up from guiding on a star adventurer pro to an NEQ6 pro (second hand). I tried it out for the first time last night.

I'm using EQmod and guiding in PHD2 (pulse guiding.)
The graph started out looking fine for about a minute but then suddenly it blows out to 12". It keeps doing this and I have no idea why.

I'm hoping someone here might be able to point me in the right direction of what's going on here. Nothing was snagged - I also tried it by guiding with ST4 and had the same problem.

[Sunfish]

Can be bad alignment . Try a drift align in PHD2 , adjust, and then try again.

Also cone error if your optical axis is not on the mount axis or loose puck.

Did the calibration work ok and have you changed anything since?

[Retrograde]

Interesting that it's happening in both RA & Dec at the same time.
Wind gusts? It was quite windy in Sydney last night.

[multiweb]

Looks like something got jammed. :eyepop:

[jahnpahwa]

After an *incident* with my HEQ5pro (very similar mechanically, smaller payload) I've had a very similar thing start happening. 120secs in the Dec axis wanders off a cliff, never to come back.

I initially thought that it might be a damaged section of the worm drive, but if i stop guiding and restart straight away it is fine for another 120secs.

I'm pulling the whole mount apart this week to see if anything has broken and I'll let you know what I find.

Yours pulling off both RA and dec is a noteworthy difference, but perhaps I'll find something that will be of use to you too :thumbsup:

JP

[jase.film]

I used a polemaster to align but I'll try drift aligning to be certain next time.



This was before it got windy, was actually quite calm when I was trying this.

[Russj]

Low battery voltage or a power supply that is unable to supply 13 volts and the current needed (around 3-4 amps) to run the mount can cause your problem, check if the red led is flashing during operation, this will indicate low voltage.

You need 13 volts to run an NEQ6 ....12 volts is often not enough, I had the same problem.

[Lognic04]

I see you use EQMOD - Try making sure your guide rate isn't set to 0.1x, being the default guide rate for some reason. Also try realign phd2.
Cheers

[luka]

The graph stops short, did PHD actually manage to bring the guidestar back after the huge jump or did it just keep trying?

[jase.film]

Both dec and RA went off to about +/- 12" and the stay there. Sometimes it brings it back for a short while and then it blows back out to +/- 12" but most of the time it doesn't manage to bring it back.



Really? I'm powering it from a powertech power bank (https://www.bintel.com.au/product/powertech-lithium-power-tank/?v=322b26af01d5) and a 12v 5a power supply - because I'm also charging my laptop from it.

Should I use a 15v supply like this one (https://www.amazon.com.au/Universal-Charger-Adapter-Toshiba-Notebook/dp/B0797KTSBF/ref=sr_1_1?dchild=1&keywords=15v+power+supply&qid=1595290590&sr=8-1) maybe?

[luka]

Something else is going on here. I just realised that your RA and DEC are mirror images of each other, they are not just both shifting in the opposite directions.

Few things come to mind:
How good is your guide star? Try a different one.
Run guiding assistant, see what that gives.
Try disabling guiding and let the star drift. See if it still jumps.

[Astronovice]

If the mount does require more than 12V to operate effectively that may well be the problem. Laptop chargers are usually 19V, so the combined laptop plus mount etc. load may well be dragging the available voltage down to 12V or less.

The usual Powertech charger is 15V 2A, so it may be worth using that instead of the 12V 5A power supply you are using just to see if this varies the time elapsed before drop off occurs. This would then be a clue that under voltage is the problem.

Are all of the loads hanging off the Powertech with the 12V 5A supply then charging the Powertech?

If under voltage is the problem I would look for a straight 15V 5A power supply rather than the multi voltage one you suggest to avoid the risk of frying the mount and / or having too large a voltage difference between the charge voltage and Powertech output voltage. Laptop on board voltage controllers normally limit the voltage output from such power supplies to suit and in this case you may finish up with the highest voltage being supplied. Make sure that the dc plug diameter is correct on what you buy and that the connection is “centre pin positive!”.

You know you will be ok with a 15V charger for the Powetech as that is what the Powertech normally uses.

The NEQ6 will also be fine at 15V max but I wouldn’t go above that.

[luka]

The mount does not need more than 12V to function, I am using mine with a 12V power supply and never had an issue. The manual actually specifies 11V-15V, however lots of people had issues using the lower voltages. Lots of cheap supplies out there probably could not provide stable current resulting in a voltage drop and hence the mount issues.

Is the mount "skipping" during slewing? During slewing it pulls most of the current. If it is slewing fine I doubt that the power supply will cause issues while tracking/guiding when it is using much less power.

If voltage is a problem the red light on the mount should flash. Maybe watch the light when it is misbehaving.

But I doubt the voltage is the issue here. If the mount suddenly stopped tracking or the steppers started skipping the star would drift off only in RA and not in DEC as well. But your RA and DEC were basically mirror of each other.

If you are worried about the power supply you could "borrow" the 12V power supply from somewhere in your house. Lost of devices are 12V nowadays. Check your NBN modem, WiFi router etc. As long it has 2A or more it should be fine. And positive tip (which is almost everything).

But as I said I doubt the problem is the power.

Run the mount without guiding and see how it goes. Run it with only RA guiding and see how it goes. Check the guide star. Run guiding assistant. Check guide rate in EQMOD, set it to 0.5 or larger. If using guidescope you can try guiding directly through your telescope (you will need a new profile in PHD2).

[Sunfish]

If the mount is short on power the power light might blink like the Heq5 as mentioned by Lukea. Mine runs only an amp or so at 12v .

Simple question but Is your mount load balanced before you start ? I agree if it is windy the mount will struggle to guide with loose cables and a large dew shield or any fixtures coming loose in the cold. The mount is not powerful enough to run an unbalanced load.

[Slawomir]

Could be backlash in the Dec and/or RA - is it possible to increase the 2500 ms max pulse?

Might be also worth trying to use a small box around the star for guiding - I used to have issues with sudden movements that were caused by some random interference pattern in guide subs, which disappeared when I started using a small box around the star - I guess less traffic/data flows via USB.

But I'm guessing your particular issue is caused by excessive backlash in at least one of the axes.

[The_bluester]

The obvious first question, have you changed anything in your setup since calibrating PHD2? My first port of call would be to re calibrate. The only time mine has behaved like that was when I made some changes that resulted in a change of the guide camera angle and I got ties up and forgot to re calibrate, it guided ok'ish until a whiffle of wind moved the scope a bit then it ran away like that as the guide corrections were not actually moving the scope in the direction PHD expected. While the corrections were tiny (Probably actually chasing the seeing more than the mount) it was more or less OK but when it put in it's first sizable correction off it went just like your graph.

[jase.film]

Retried it last night and it's all working fine. I can only assume it was user error at some point and I had a messed up calibration.
I did switch out the power supply for a 15v 2A one I had but I'm not too convinced it was a power issue.

Thanks for all the suggestions!