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Old 30-08-2016, 03:10 PM
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OneCosmos (Chris)
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Anyone using the ZWO as a guide camera with PHD?

Hi,

I have been happily guiding with the lodestar for sometime but have switched to guiding through a smaller focal length guidescope (Orion mini guider - 162mm FL) to guide my 900mm fl main scope. To be honest it does seem to be working with the lodestar but I wanted to see if the ZWO 120 MMS would give even better results due to its smaller pixel/higher resolution - just wondered if it would improve the accuracy of the corrections/guiding.

With the lodestar I don't use the ST4 port because mine has that rubbish white cable with pins the size of gnat's teeth and of course if falls out if there is a slight breeze in Singapore So, I'm pulse guiding via EQMOD.

I have never used a webcam before for astronomy and I really don't know how to make it actually work! I have the driver installed etc and PHD 2.6 will connect to it if I choose the ZWO option in the camera choices. I then use the brain to calculate the step/ms as usual and set the exposure time to 2s I couldn't see anything - completely white even with the gamma display slider turned right down. If I changed the exposure to 0.2s I saw stars. I was concerned though because I have also believed that anything less than about 2 seconds leaves you chasing seeing - but this is a video camera so I thought perhaps it works differently somehow. I selected a star and told PHD to calibrate. I can't remember the error but it was almost immediate and said something iike the camera didn't take a 2s exposure and stopped or something. Someone told me I would have to click the advanced camera settings and change the frame rate as it would be 60fps or similar, but that button ius greyed out - perhaps because I wasn't connecting with the ST4 port?

I found ZWO instructions online but it was based on a much earlier version of PHD when there was no ZWO camera option.

So, please if anyone uses this camera for pulse guiding or ST4 guiding with the latest PHD please let me know what you had to do to get it working.

Cheers,

Chris
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Old 30-08-2016, 03:22 PM
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Atmos (Colin)
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I've been using an ZWO ASI120MM-S for about a year now without any problems.
I've used the ST-4 port with PHD2 and just use the On-Camera as the Mount and it sends the guide pulses through the ST-4 cable that way.

If you're talking to a mount you can put it in as the Aux part just after the mount, just means it reads information from the mount.
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Old 30-08-2016, 03:42 PM
glend (Glen)
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Personally i had a lot of trouble with PHD2 and my ASI130mm guide camera. PHD2 would drop out, freeze, and was generally unstable. I switched to Metaguide, which supports ASI cameras natively, and have never had a problem again. Metaguide is designed fir high frame rate video type cameras like the ASIs and my research at the time suggested PHD2 could not cope with high frame rate video, preferring slow exposures. Now it maybe that a new version of PHD2 was subsequently released but i have stuck with Metaguide as i understand it and it just works.
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Old 30-08-2016, 05:19 PM
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peter_4059 (Peter)
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I'm using it with phd2 and eqmod puse guiding with no problems. I use the ascom driver for the ASI but it also works with the native ASI driver
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Old 30-08-2016, 06:21 PM
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OneCosmos (Chris)
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Well I have just downloaded the very latest release version of PHD 2 (2.6.2) and like 2.6.1 when you choose the camera there is a specific ZWO option which is what I was choosing. It did not however allow to access the advanced camera features.

I am now connecting using the Windows WDM option and choosing my camera model and resolution from the list. I have also connected the ST4 cable to the mount. I have heard this is the better option anyway as pulse guiding can be slow. I on;y used pulse guiding because tghe ST4 c able with the lodestar is the worst design in the history of connectors!

The problem now is that the advanced camera settings have lots of options I have never set before (never presented with the lodestar) and the help on the ZWO site is hopeless because it is all based on PHD 1.4!

I have attached snips of the three main tabs of the advanced camefra settings. You see I have changed the first one to seconds and set an exposure of 2s

Chris
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Old 31-08-2016, 07:47 AM
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OneCosmos (Chris)
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*update*

it wasn't clear last night but there were enough stars to do a few guiding tests.

Firstly, to reiterate the key point of my last message the advanced camera options do not become available if you select the dedicated ZWO camera option but do if you choose the Windows WDM option and then select your ASI camera from the list.

In the end though, the solution didn't have so much to do with the camera I connected to but rather how I connected to the mount.

Normally I open POTH and connect to the Sirius dome and also use POTH to connect to the EQ8. Thereafter everything that needs to connect to the mount just connects to POTH - which as I've mentioned is connected to the mount. So in SG Pro I connect to POTH, in PHD I connect to POTH.

The only way I could get the ZWO to work as a guide camera though was to connect the ST4 guide cable from camera to mount and then in PHD for the mount select the On Camera option. Set the gain the default is way too high, mine is now I think at 50%, set the exposure to seconds with an appropriate number and calibrate.

At first I got errors every time I tried to guide saying it stopped because the mount started slewing, which wasn't true. In the end I realised this was because pulse guiding was still enabled in EQMod, once I turned that off the camera calibrated fine and the guide graph looked good. Actually, I thought the graph looked far more flat with the lodestar but I put that down to the fact that the lodetsar has 8.3 micron pixels whilst the ZWO 120 has 3. something pixels. The higher resolution acts like putting a barlow on the lodestar so although the RA and dec lines seem busier I presuming it i within a far more narrow range on the chip.

Unfortunately mostly cloudy turned in to almost completely cloudy so I don't have any subs to assess if guiding is yet successful, but if it is it may transform things for me.

The mini Orion guidescope just sits in the finder bracket on the focuser which means I will be able to remove the long bar sitting on the main rings which curently holds the Orion ST 80 guidescope. This has two massive advantages for me:

There is more tolerance in the position of the dome shutter so that even if it isn't perfect both main scope and the mini guider can still see the sky - not always true with the separation between the main scope and the ST80;
When I decide to switch to visual for an evening as I like to do the bar really gets in the way of where my head needs to be!

For others another advantage would be reduced weight, but not an issue for me as the EQ8 is well within its capabilities with or without the bar.

Just need a clear sky now to confirm things are working.

Chris
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