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Quick question on Guiding set up / PHD2


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Hi,

I wasted quite a bit of time of last nights clear sky struggling to get PHD2 to calibrate.  It failed each time giving me a message of ‘RA calibration failed : star did not move enough’.  My set up is a little unusual as below:

guide scope - Evoguide 50 - focal length 242mm

guide cam - zwo asi 294mc (4.63 um), binning x1

is there a fundamental problem with the set up that you can see or any other tips if you’ve experienced anything similar? I tried running the new wizard set up and even uninstalling PHD2 and reinstalling.
 

just for reference, the imaging set up is a Meade 8” lx200, focal length 2000, with a 0.62 reducer, bin x2, and a zwo asi 294mc pro so I think if I do manage to eventually calibrate the guide vs imaging scale with be ok ish.

any help would be much appreciated.

andrew

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Did you try to calibrate at or near 0 degrees? Or a better question where were you pointing for the calibration? Might not be the answer and it's a pretty wide view on the guidescope too but just a thought.

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Agreed, location looks absolutely fine... Oh and I checked the scope/camera combo and not a lot different actually to my WO 200mm/120mm mini so that looks fine too.

Basically no idea, sorry 🙂

Edited by scotty38
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6 hours ago, scotty38 said:

Did you try to calibrate at or near 0 degrees? Or a better question where were you pointing for the calibration? Might not be the answer and it's a pretty wide view on the guidescope too but just a thought.

That depends if he's pulse guiding or st4..if pulse guiding then yes, calibrate on the meridian/ equator intersection but if st4 then every target before and after flipping will need to be recalibrated

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5 minutes ago, newbie alert said:

That depends if he's pulse guiding or st4..if pulse guiding then yes, calibrate on the meridian/ equator intersection but if st4 then every target before and after flipping will need to be recalibrated

I did assume pulse given he's using 294mc cameras and I don't think there is an ST4 port, well there isn't on the Pro at least...

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2 hours ago, scotty38 said:

I did assume pulse given he's using 294mc cameras and I don't think there is an ST4 port, well there isn't on the Pro at least...

I've no idea on zwo camera's, never had one

Edited by newbie alert
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Thank you for your help / offer of help everyone.  I won’t need to post my logs though as I wiggled a couple of cables and PHD is now actually communicating with my mount 🙄.  Slightly embarrassed 😳 

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4 hours ago, vlaiv said:

Don't be. I think almost everyone wiggled a cable or two at some point :D

Definitely. And replaced them if they needed too much wiggling. ;)

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Think I might although they are decent quality - Lyndy Cromo.  After getting calibration to work and running guide assist I tried actually guiding and it went crazy, literally off the graph with RMS over 10”. After a short but intense sulk I deleted the PHD profile and set up again from scratch.  Guiding was around the 1” RMS mark which I appreciate could be better but I’m viewing it as a triumph.  I’ll see what happens next time we have a clear night 🤞and if the problem happens again I’ll buy some more cables.  

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Once you have the cables sorted, run the Guiding Assistant as well... it will measure backlash as well as suggest suitable values for the min move parameters...

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What @daz said. 🙂

Don't fiddle with parameters while guiding. It won't break anything, but you won't be able to tell anything from what you changed anyway. Let it guide for at least an hour (unless it really is all over the place). Then view the guide graph in PHD Log Viewer (link on the PHD site). This is a very handy tool for trouble shooting and guide tuning.

Btw, as asked before; what mount do you use?

Edited by wimvb
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2 hours ago, daz said:

Once you have the cables sorted, run the Guiding Assistant as well...

Will do.

 

1 hour ago, wimvb said:

Don't fiddle with parameters while guiding.

No fiddling of parameters was done - only wiggling of cables 😂.  Must admit I only let it run for a few minutes but I think when the RA graph goes off the  scale and RMS is over 10 is a good indicator something is awry.  I’ll follow your suggestion to guide for an hour (if the opportunity arises again ☁️)  but I might need some expert assistance in analysing guide graphs.  It’s an EQ6R Pro btw.

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3 hours ago, Priesters said:

It’s an EQ6R Pro

Depending on seeing and where you point it, that mount should give you <0.5" guiding for extended periods. 

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15 hours ago, wimvb said:

Depending on seeing and where you point it, that mount should give you <0.5" guiding for extended periods. 

At high dec and decent-ish seeing this should be achievable. At celestial equator, values around 0.8" are more realistic.

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Sadly the saga continues...

There was a couple of hours of semi clear skies last night so I thought I'd test guiding again, run GA and apply recommendations.  I used exactly the same PHD profile that I had ended my last 'successful' session with.  I was disappointed to find that when I started guiding it was way off -  on one run it was so bad the guide star disappeared from the star profile in PHD in a matter of seconds.  It was as though each PHD pulse was exponentially sending the mount the wrong way, however, at least it was clear PHD was communicating with the mount.  Nevertheless, I did still check cables were connected firmly and I re-checked the mount for snags and any other obvious mechanical issues.  When I tried again I got the same result with one attempt ending with PHD giving an error message to say guiding had failed as Dec was unable to recover.  The experiment was a little hampered by passing clouds but I'm pretty confident that was not the root cause.  I also checked mount tracking when not guiding and as far as I can tell it was ok.

So, the next thing I did was delete the previous 'successful' profile and run the new profile wizard again.  It worked.  Guiding was around the 1" mark, occasionally going higher, mainly due to lost guide stars as a result of passing clouds.  I didn't touch the mount at all in between the failed and successful guiding runs so I'm sure it was running the new profile wizard that fixed it.  This is a sub optimal solution as I really don't want to have to re-run new profile wizard each session, build dark library, calibrate and run GA at the start of each session - it takes me long enough to set up as it is!   I'm beginning to think there is some sort of software conflict because I am running with an ASI 294MC for the guide cam and an ASI 294MC Pro for imaging.  Just for the record, on all guiding attempts, I double checked PHD was connected to the correct camera.  My next step is to swap the guide cam to my Altair 327C to test this theory.  However, I have attached the logs from last night if anyone is interested and can spot something I'm missing.  I have yet to learn how to read these logs so please bear that in mind if you do review and reply.  The deleted profile name was EvoGuide 294 and the new one Evo 294. 

Thanks

Andrew

 

PHD2_GuideLog_2022-01-07_202046.txt

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I had a look at the guide log. The calibration looks very good; orthogonality is ok, and step sizes in DEC and RA are the same. No apparent sign of backlash (the guiding assistant confirms this: only 665 ms, which you don't need to improve.)

I think that a guiding aggression of 0.9 is a bit high, but this is not the cause of your problems. The guiding assistant shows that DEC wanders off quite fast, meaning that your polar alignment was way off. The numbers shown at the end of the GA run again confirm this; 21 arc-minutes is not good. The reason that RA wanders off during the GA run is a combination of polar misalignment and periodic error. Next time you run GA, let it run for at least 10 minutes to get a better understanding of how large periodic error your mount has.

If you create a new PHD profile, you shouldn't need to take new darks, afaIk. Otoh, unless you have a permanent setup on a pier, you need to recalibrate PHD at the beginning of each session, even if you don't take the guidescope/camera off the main telescope.

Regarding the conflicting cameras, this is a possibility. When ZWO cameras were still relatively new, there were several reports of camera conflicts, but I think that software developers both at ZWO and in the astrophotography community have solved most of these issues. Many people run ZWO cameras for imaging and guiding (the ASIAIR is based on the premise that this will never be an issue). But I think that very few people run basically the same camera model for imaging and guiding. I don't know how to do this in Windows, but you might want to check the camera identity by looking at the respective COM port information. (e.g, when I check what is connected to the USB ports of my Raspberry Pi, I get the identity 03c3:294e for my ZWO ASI294MM PRO imaging camera, and 03c3:290f for my ZWO ASI290M-mini guide camera. 03c3 is the vendor ID, and the rest is the camera ID.) If these identities are different, the cameras shouldn't interfere, but if they are the same, you can have a problem.

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Also, try to stick with 2 second exposures. 1 second guiding exposures wont really help you.

I'm a bit suspicious of the normalised guide rates: Ra 17.2 and Dec 15.6 when 13.5 is expected.

Make sure you are tracking at sidereal rate and that the controller knows you have a EQ6R

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33 minutes ago, wimvb said:

I had a look at the guide log

That is very much appreciated.  
 

I too was a bit horror struck by the polar alignment error.  Before starting the session I polar aligned via SharpCap but I’m just wondering whether I gave the Mount a bump when I was checking cables and other mechanical issues.  Next time out I’ll run GA again and see if it improves. Thanks for the advice on calibrating for each session - I hadn’t appreciated the need to do that.  When I created the new profile via the wizard I’m pretty sure it insisted on a new darks library but I’ll check again next time.  I guess it’s no big deal anyway as I can restrict the range of exposures to between 1 and 3 seconds which will cover my usage so it won’t take long anyway.

thanks again for reviewing the logs.

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2 minutes ago, kens said:

Make sure you are tracking at sidereal rate and that the controller knows you have a EQ6R

Yes, at one point I noticed EQMOd was tracking at Custom but when I corrected that it didn’t resolve the problem. I’ll take your advice on the exposures time. A hand controller isn’t involved as I’m using EQDIR so at least I can eliminate that.

thanks for your help.

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6 minutes ago, Priesters said:

Before starting the session I polar aligned via SharpCap but I’m just wondering whether I gave the Mount a bump

SharpCap gives you an accurate PA allright, but where do you set up? Before I put my rig on a pier, I had to avoid setting up on a wooden deck or putting the tripod directly on grass, because me moving around would move the mount enough to change PA. To help with alignment I pressed fence post anchors into the ground for the tripod legs to sit on (the kind with L shaped top, with the vertical part removed). This also helped with polar alignment.

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