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Old 30-08-2017, 10:30 AM
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multiweb (Marc)
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ASI ZWO 120MM for guiding

Has anyone used one of these for guiding with PHD? I did a bit of testing and the fastest frame rate (0.05s) seems to be a bit low like there is a delay in displaying the sub. (8bit FIT). I used the camera ASCOM(late) driver.
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Old 30-08-2017, 10:44 AM
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Atmos (Colin)
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I used one for guiding for quite some time without any issues
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Old 30-08-2017, 10:48 AM
glend (Glen)
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It is a pretty sensitive little guide camera, widely used. I just replaced my less sensitive ASI130MM with the ASI120.
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Old 30-08-2017, 12:14 PM
hamiland (Anders)
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0.05 Seconds seems bit fast, and you would potentially be chasing the seeing with that setting, however it depends on your optical train for guiding. I usually run 0.5 or 1 sec guiding subs with the same camera. Assuming that you meant to say "slow" instead of low? Are you using a USB hub, is it the USB 2 or 3 version, and what hardware are you running on?

I have found that with PHD with fast subs such as you are describing I did have issues not dissimilar to the ones you are describing.
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Old 30-08-2017, 12:20 PM
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I'm using one. Normally 2 to 3 second exposures.
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Old 30-08-2017, 12:32 PM
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Thanks for the feedback. Yes I wouldn't guide at 0.05s unless using an AO but I have a lodestar for this. Just pointing out that setting an exposure of 0.05s in PHD doesn't even loop under 1 frame per second, compared to other guiders, such as a QHY5 or lodestar which will cycle through a lot faster. So my question was if it's a natural behaviour of the camera or if there is a bottleneck in the driver or hardware. I'm using USB2.0 and it was a direct connection from laptop to camera. When using FireCapture no problem at all. I can sustain very high frame rates. I tried in PHD1 not PHD 2.
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Old 30-08-2017, 01:01 PM
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Why guide at 0.05 sec? The mount can't react to changes that fast.
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Old 30-08-2017, 01:09 PM
hamiland (Anders)
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Not sure actually, I have seen the behaviour in PHD2 and never actually stopped to think about it. I don't have an AO device so guide using longer exposures which works 100% for me. As you say at shorter exposures the camera works well in Firecap. You could try sending a message to ZWO and or PHD support maybe if it's of real concern?
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Old 30-08-2017, 01:13 PM
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Quote:
Originally Posted by peter_4059 View Post
Why guide at 0.05 sec? The mount can't react to changes that fast.
An AO with a bright star will practically work at 7Hz no problem. The mount is bumped whenever the guidestar gets out of a predefined area within the guider's FOV. So you need to be able to sustain higher frame rates with a very sensitive guider to run an AO.

Quote:
Originally Posted by hamiland View Post
Not sure actually, I have seen the behaviour in PHD2 and never actually stopped to think about it. I don't have an AO device so guide using longer exposures which works 100% for me. As you say at shorter exposures the camera works well in Firecap. You could try sending a message to ZWO and or PHD support maybe if it's of real concern?
Not a real concern as I will likely guide at 1s minimum. Just something I noticed yesterday and wondered about when I plugged it into a guider to the lappie and was running the loop in PHD.
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Old 30-08-2017, 01:20 PM
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Now you've got me curious... I'm going to have to have another play and see if I can work out what's going on..... There's another thing on my Astro todo list... (Might have to be down the bottom as there's the likelihood I'll break something in the process )
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Old 30-08-2017, 01:22 PM
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Some lazy programmer probably solved a race condition in the driver with a "sleep(1);"
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Old 30-08-2017, 01:26 PM
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Some lazy programmer probably solved a race condition in the driver with a "sleep(1);"
Looks like Iberian JavaScript to me Ricardo...
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Old 30-08-2017, 02:32 PM
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Looks like Iberian JavaScript to me Ricardo...

That would be "siesta(1)", Marc
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Old 30-08-2017, 02:40 PM
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Quote:
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That would be "siesta(1)", Marc
Might download the new ASCOMigo version.
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Old 30-08-2017, 02:46 PM
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Quote:
Originally Posted by hamiland View Post
Now you've got me curious... I'm going to have to have another play and see if I can work out what's going on..... There's another thing on my Astro todo list... (Might have to be down the bottom as there's the likelihood I'll break something in the process )
It's working fine in PHD2. I can get down to 0.5s easily, 0.1s pushing it but that's more than adequate. Must have been a PHD1 issue. So all is well.
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Old 30-08-2017, 02:52 PM
hamiland (Anders)
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Sounds like it is 1 better indeed
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Old 30-08-2017, 02:54 PM
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Quote:
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Sounds like it is 1 better indeed
Indeed PHD2 seems to support a dedicated ASI ZWO driver so no need to go through ASCOM anymore thereby bypassing the siesta() issue.
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Old 08-09-2017, 08:21 PM
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I use one with PhD2 no troubles. Usually 0.5 seconds. I have a really old netbook for it as well.
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Old 10-09-2017, 12:28 PM
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I have one I use for guiding. I use 1 sec.

But I do have problems where it split frames, so my guide star is lost until I stop the camera and start again.
So I will be replacing the camera with ZWO new mini cameras.

I have the USB2 version and I have read that its the USB2 version has this issue, and upgrading the drivers do not work.

Ben
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Old 10-09-2017, 02:07 PM
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Thanks for the feedback. I hope I don't run into any of these issues.
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