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Old 31-08-2016, 06:47 AM
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OneCosmos (Chris)
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Join Date: Apr 2010
Location: Brisbane
Posts: 354
*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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