Tony Gondola avatar
I have been having a problem lately that when there is the slightest breeze, PHD2 looses lock on the guide star. This is eating up a lot of time while it settles itself to start guiding again. Is there a setting to look at that can make it less sensitive to this issue? I'm running standard settings and run a calibration and  guiding assistant regularly, accepting the values it gives me. The setup is a 150mm F/6 Newt. on a EQ6R-Pro. Everything is well balanced. The guiding setup is an 80mm F/5 doublet with a UV/IR cur filter feeding a 585MC. Exposure is set to auto 1-5 sec.
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Himanshu Pandey avatar
Try to increase the search box size from 15 to 30 pixels, this should help deal with all but the strongest gusts.

Jim Waters avatar
I agree.  Try increasing the search size box.  Also its best to use a mono guide camera.
Tony Gondola avatar
Can't change the camera and it generally works well. The box size change makes sense as it is currently at 15 pix. I'll give that a try tonight.
andrea tasselli avatar
You gotta have a wobbly setup if the default doesn't work well. I'm in wind country and the default works well all the time. Even if imaging is close to impossible.
John Hayes avatar
How stable is the scope?  If you were to put an eyepiece on it to watch a star and then tap the tube with your finger, how much time does it take for the vibration to die out?  Increasing the search box size is a good suggestion but you also want to make sure that the system is mechanically very rigid.  Ideally, a moderate tap shouldn't produce hardly any motion and the damping time should be almost immediate–say ~0.1 sec.

John
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Tony Gondola avatar
Andrea and John, I'll double check that everything is tight and balanced and I'll give the tap test a try although I'm not sure how I could effect the damping time if it's too long. I could lower the frequency by adding mass as all the moment arms are already as low as I can get them.
andrea tasselli avatar
Hard to say without looking at the setup but in the years I found two main culprits: one is not tight enough central bolt (the one that secures the mount to tripod/pier) and the other is loose bearings on RA. I assume that you run the EQ6 within its specs and the cradle/tube rings are well tight and the comments above apply to any such system.
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Jim Waters avatar
I agree with the above assessments.  I would check for other causes first and not widen the tracking parameters.  Something is loose is the setup.  If there's a helical focuser on the guide scope make sure its not wiggling around.  Same for the mounting of the guide scope if you use rings.  Start at the top and work down to the tripod.

Since you are using a Newt check for mirror flop.  

Jim
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Tony Gondola avatar
I'm ok on weight limits. Thing is, it's been working great up until the last two sessions. I will check the tripod center post though, great idea. I'm not feeling any play in RA or DEC.
Tony Gondola avatar
Imaging tonight so I'll see what I find.
Himanshu Pandey avatar
I could be wrong but the default search window size had been increased in one of the development release of the app from 15 to 25.  Try switching to ver7 for many other improvements.
Chris Strang avatar
Most likely it is your computer if you are using a power hub. Go into power management under device management.

All the way to the bottom is Universal Serial Bus controllers. Most of the hubs (devices) will have a Power Manage setting. There is a box that reads “allow cpu to turnoff this device. Uncheck this box for all lines. Each USB port is spec for 0.5 amps. If your hub’s voltage is a little higher than the computers there is no amp flow so the CPU thinks it is not in use and turns it off. Hope this helps. Chris
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Tony Gondola avatar
Chris Strang:
Most likely it is your computer if you are using a power hub. Go into power management under device management.

All the way to the bottom is Universal Serial Bus controllers. Most of the hubs (devices) will have a Power Manage setting. There is a box that reads “allow cpu to turnoff this device. Uncheck this box for all lines. Each USB port is spec for 0.5 amps. If your hub’s voltage is a little higher than the computers there is no amp flow so the CPU thinks it is not in use and turns it off. Hope this helps. Chris

Good thought but no power hub here.
Tony Gondola avatar
Himanshu Pandey:
I could be wrong but the default search window size had been increased in one of the development release of the app from 15 to 25.  Try switching to ver7 for many other improvements.

I'll give that a try...
Chris Strang avatar
USB problem. I should have added. You may think you have no POWER HUBs, but many devices such as cameras have auxiliary USB outputs, some mounts, and other devices. In all probability they are powered hubs. Even when you uncheck the power management box at times it becomes recheck for some reason. Also, if some drivers cannot load (PoleMaster - QHY) turning off Memory Integrity setting in Windows Security usually helps. Chris
Tony Gondola avatar
Chris Strang:
USB problem. I should have added. You may think you have no POWER HUBs, but many devices such as cameras have auxiliary USB outputs, some mounts, and other devices. In all probability they are powered hubs. Even when you uncheck the power management box at times it becomes recheck for some reason. Also, if some drivers cannot load (PoleMaster - QHY) turning off Memory Integrity setting in Windows Security usually helps. Chris

The guider does go through the on camera hub but I thought that was passive. I'll double check that setting next time I'm powered up.
Tony Gondola avatar
Ok, I finally solved the problem.

On mechanics, everything was tight except the central tripod shaft ad the azimuth adjustment bolts. Thanks Andrea for that tip. That improved things a bit but I would still loose lock during guiding. Doing John's rap test, the system stopped oscillating after about a sec.

Last night I installed the latest dev. release of PHD2, ran a new calibration and guiding assistant. The wind was about that same as it had been through this entire ordeal so I started watching the behavior of PHD2 very carefully. It was loosing lock whenever the HFD of the guide star dropped so I decreased the min. HFD value to 3.5. That improved things but lost lock would still happen with a good gust. I then opened up the search box to 25 pixels and increased the camera gain to 95, again a bit better. The last move was to remove the uv/ir filter from the guide scope. The filter was giving tight stars but was reducing the SNR. PHD2 seemed to be happier with bloated but bright stars. Now I was no longer loosing lock but the guiding was all over the place. I had taken the suggested MinMo numbers from the guiding assistant and they were pretty large, up around 65 for RA and DEC. Once I dropped those values to about half of suggested, guiding clamed down and was rock solid for the rest of the night.

Thanks to everyone who helped out on this. Hopefully my experience can help others who run into the same issue. PHD2 is simple but not always right. It's worthwhile to get in there and carefully tweak settings if needed for you conditions and system.
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Médéric Hébert avatar
Not related to your issue, but have you tried an IR pass filter instead of the UV/IR?
Tony Gondola avatar
I have and I got good results with it. I may go back to that once I'm really sure that things are back to normal with guiding.