PHD guiding

[acarleton]

i have just tried guiding for the first time and i have run into a few issues. i use a QHY5l-ii with an orion 50mm guidescope and use autoselect to pick a star in PHD guiding. PHD does its thing, configuring and i get a green box, guiding has commenced. the issue is that i look at the worm and it is going a little crazy, fluctuating significantly above and below the line. i thought that this might be a Periodic error issue however it seems that the RA and dec line follow a very similar path. sometimes i can get guiding for about 60 seconds with decent accuracy, but at this point i think my unguiding is more accurate than the guiding. does anyone know what could cause this? does the camera need to be oriented in a specific way (RA slew goes perfectly horizontal) or is this indicative of a PE issue? thanks for the help.

Aidan

[Screwdriverone]

Hi Aidan,

Sounds like your Polar Alignment is off.

Go to the brain symbol and turn off the guide output, turn on the cross hairs and capture images again, select a star, put it in the centre of the cross hairs and watch it for about 1-2 minutes. As PHD is NOT telling the scope to move (because you disabled the output in the brain) you should see if the star moves away from the cross hairs.

What I do to align the scope using the guidescope and PHD is just this, but first I select a star either east or west about 30-40 degrees up from the horizon. If the star moves off the cross hairs, adjust the ALTITUDE bolts (the up-downs) and see if you can slow down the star's drift. Recenter the star after the bolt adjust. After a while if you get some improvement, slew to a star overhead (so the scope counter weights are horizontal and the tube is perpendicular to the counterweights (like a T) and pointing pretty much straight up. Repeat the drift check with a star in the cross hairs and ONLY ADJUST THE Azimuth bolts (the left-right ones) until you can slow down or STOP the star drift.

Go back to an east or west star, check it again, adjust as necessary, rinse and repeat and see if you can keep the star IN the crosshairs for a few minutes and then turn ON the brain guiding output. CHECK the box that tells the program to FORCE the calibration, wait for the calibration to finish and then see what the graph does now.

That's what I do, once you think you have it dialled in, MARK the tripod leg positions on the ground so you can plonk down the scope next time and get going quickly again.

Of course I would also check the tube is balanced in RA and DEC as well as if it is too heavy, PHD has a bugger of a time pushing and pulling the scope if it is heavy one side or both....

Give this a go, sorry for the essay ;)

Cheers

Chris

[acarleton]

never mind the essay, any help is appreciated. i have played around with the balance, getting it just right, even so, an unbalanced scope wouldnt result in the RA and dec worms following each other. it certainly does seem like a polar alignment issue, i thought i had it fairly well polar aligned but that might not be true. i will give it another go tomorrow.

[mithrandir]

You should also know that perfect balance is a guiding nuisance. Any slack in the gearing means the motors don't always have control of the mount. (There must be some slack otherwise temperature changes will jam the gears.)
You want the balance to be slightly heavy on the east side - which means rebalancing after crossing the meridian. This means the RA motor is always pushing the load.

[acarleton]

yeah, i try to get an east bias on the balance.

[acarleton]

okay ... this seems to be the second issue i cant resolve (i still can't get a crisp view of planets in my camera) maybe i am doomed never to be good at this stuff. sooooooo, i checked the balance, perfect, little bit of an east bias, checked the polar alignment and in 2 mins the star moved a couple of pixels but it was pretty good. then i enabled guiding and ooohhh boy. i have attached an image of the worm so you can see what is happening, this is worse then before. it seems that the corrections do nothing and then completely over correct. the first worm shows how it went wen i just left it for a while and the second one shows me stopping guiding and then fiddling around with some of the settings, it doesnt seem to make much of a difference. the key thing to note is that the star seems to move away from the centre of the cross faster when it is guiding then when guiding is off :screwy:

very frustrating, any thoughts would be good

[Merlin66]

Aiden,
I'm sorry to say, that must be one of the worst PHD guide graphs I've ever seen!!!
There is something seriously wrong with your set-up or software/ settings...
You say you're using a QHY5L-II and a 50mm guide scope - I assume this is a "finder guider" arrangement...
Double double check the adaptors/ brackets for any sign of movement - even this slightest.

I regularly use a Lodestar but at the native f10 of my scope.
On the NEQ6pro I normally get the guiding to graph well within 0.2 pixel.
(If it were only a PA issue you'd see the guider making the continuous Dec corrections to overcome the "drift" but the RA should be relatively stable.)

[acarleton]

yes i agree, probably the worst possible graph, it was a lot better the first time i tried it (not perfect but better). good point about PA... everything seems fairly secure, i will try reinstalling PHD and start from the ground up.

[blink138]

hello aiden i am not very experienced at this either but i did read once that if you utilise the PEC with PHD that they can work against one another, if you are using PEC that is
pat

[acarleton]

I am not using pec so shouldn't be that but thanks for the suggestion

[kosh]

I'm no expert Aiden, but when I look at those screens, I have noticed very quick " sample " times in PHD, the top one has a 0.1 second exposure and the second graph has a 0.5 sec exposure. My understanding is that you should never be under 1 second when guiding as you "chase" the star. Have you tried between 1-3 second exposures?
I have the same guidecam, guidescope and mount and have never had it quite that bad, even when starting out.
Of course I could be completely off but worth looking into.

Goran.

[acarleton]

Thanks for that, I will try that too

[Peter.M]

Did you try imaging with the main camera? I say this because in PHD2 you have to tell it the focal length of the scope and the pixel size for it to give those horizontal lines any meaning. This might be that you have setup the scale wrong and your error is being amplified, having said that it shouldn't be taking that long to respond to guide pulses either.

I should have mentioned on the left hand side of the graph under settings you can change it to display in arc seconds or pixels, try changing it to pixels.

[Screwdriverone]

Hi Aidan,

I'm curious as to why you have AO switched on?

As far as I can tell with your equipment list you are not using adaptive optics with your guiding?

The error at the top of PhD is talking about theAO needing a bump and if you don't have it, this could be making everything screwy.

Just connect the guide camera, the mount, sample some images, start guiding to learn and then see what happens, AO should not be active

Chris

[acarleton]

okay, so first i have to say that i have no idea about a lot of this stuff, so everything is new ... i didn't know what AO was, but you are right, that makes no sense to have turned on, i will turn it off ... i have put my gear away for tonight so i will have to test it later. would AO turned on cause such a major issue?

with regards to any other configuration (pixels, arc seconds), i basically installed connected and guided so i have not entered any details about the scope or guidescope, the camera or mount. i am guiding off the camera, directly connected to the mount.

[acarleton]

I couldn't wait to test this out so i roughly aligned my scope (just with a compass) and started guiding ... perfect !!!! Thank you so much Chris for correcting my incompetence and stupidity. it has been a very frustrating week.

:D:):D:):D:):D:rofl::D:)

[Screwdriverone]

Lol, bring on the emoticons Aidan :)

Glad I could help , I know how frustrating it is to have problems with PHD and not know how to fix them.

There will be no stopping you now eh?

Cheers

Chris