PHD2 loss of function

Open PHD Guiding Project PHD2 Guiding Troubleshooting Help Needed
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framoro avatar
framoro avatar
Hi everyone,
did anyone ever experience a sort of loss of function of PHD2 during guiding?
It is a couple of weeks that PHD2 starts guiding conveniently but after 50-60 minutes the stars start to trail. The particular thing is that the guiding parameters and the curves do not change and continue to seem adequate. At that moment, if I stop PHD2, the stars look more round than with PHD2. I must calibrate again and then the guiding restarts to be convenient. I am using an ASI224 as guiding camera.
did anyone experience something similar? Any suggestion?
Thanks in advance.
CS
Francesco
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andrea tasselli avatar
andrea tasselli avatar
What are you guiding with and what are the respective focal lengths (guiding and imaging)? From what you said it could be differential flexure but to be sure we'll need info on your setup.
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framoro avatar
framoro avatar
Hi Andrea,
Thank you for your reply.
I am guiding with an ASI 224 (3.75 mcm pixels) on an Orion mini 50 guide scope (164mm focal length).
My telescope is a Photoline 102 F/7 (714 mm focal length) and my imaging camera is a Canon 77d (3.7 mcm pixels).
My problem is that the guide works well for about an hour, then stops to work, or even worse, it guides in the wrong direction with stars starting trailing, so that if I switch off the guide the mount by itself follows better. If I calibrate again it starts to guide well again.
Francesco
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andrea tasselli avatar
andrea tasselli avatar
I think your best bet is still differential flexure between guide scope and main scope, as you said that the PHD guiding graphs are ok despite the star trailing in the main scope. This usually is a telltale sign of differential flexure. The ratio of guiding to imaging pixel scale is 4, which is still acceptable so not much to gain there. Does the issue occur irrespective of where you point the scope at? If not sure do a test and see if it changes pointing at the zenith, 60 degrees and with the scope as near to horizontal as possible.
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framoro avatar
framoro avatar
Thank Andrea,
I need to study this differential flexure stuff…
CS!
SicIturAdAstra avatar
SicIturAdAstra avatar
@framoro framoro
Hi,
I was thinking about differential flexure too. Four questions:
What is your mount?
Where does it happen? I mean, where is pointing your scope when it goes off the road?
Is it well balance and cable managed?
How your guide scope is mounted?

Hope you find what's wrong, there is nothing more frustrating than to be in the dark like this.
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framoro avatar
framoro avatar
@framoro framoro
Hi,
I was thinking about differential flexure too. Four questions:
What is your mount?
Where does it happen? I mean, where is pointing your scope when it goes off the road?
Is it well balance and cable managed?
How your guide scope is mounted?

Hope you find what's wrong, there is nothing more frustrating than to be in the dark like this.

Thank you SicIturAdAstra (beautiful nick...)
The mount is a SW AzEq5
It happens close/little after the passing of the meridian
The mount is well balanced but cables can be managed better...
The scope is mounted on a vixen bar on top of the main tube.
I will organize the cabling better and try to make the guiding tube more stable (it is a little bit moving in its adjustable bracket).
I have noticed that this did not happen when I was using a 120 MC camera whose weight is 20% less than the one I am using now. I don’t know if this change in weight may have had some influence in the guiding tube stability...
CS
SicIturAdAstra avatar
SicIturAdAstra avatar
@framoro

Weird. So something has changed with the camera. Have you tried with the 120 again (if you still have it)?
I thinking of a few things:
You say the 224 is heavier, how is the focuser on the guidescope? Could it be that the camera slips in certain position of the setup, thus being slightly out of focus?
Have you done a dark library with the 224? And if you have done one with the 120, make sure you're not using it with the new camera.
What version of PHD are you using? Maybe try the latest dev version, it has multi star guiding, it helps a lot for precision.
If nothing works, I would reinstall PHD and the ASI drivers.
If it still doesn't works, you should try another usb/serial cable (or whatever cable you're using to connect the mount to the pc).
Or maybe you're using an Asiair, in this case I can't help you! ;)

Also, you can download PHD log viewer, with it you can analyse the guiding. And it shows events like, for example, the loss of star or if the star mass has changed. This could give you hints on what's happening.
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framoro avatar
framoro avatar
@SicIturAdAstra,
The guidescope focuser is on the front close to the lens. So the weight of the camera should not have an impact of the focuser. On the other hand the adjusting screws of the bracket were loose and the scope was not steady. Yesterday evening I have tightened the screws making the scope more stable. I have taken 2 hours of images with round stars… So it is possible that the guidescope was unstable (maybe due to more weight on the camera side), leading to differential flexure and the trail of the stars… I will try again soon to see if the problem is fixed.
I have sold the ASI 120, so I cannot try to put it back on.
The version of PHD2 is the last one (2.6.9), but have not tried the multistar guiding. I will try it to improve my guiding.
Thank you again for your feedback and suggestions.
CS
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