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Windows 8 Tablet autoguiding


sgazer

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Beside a few Milkyway shots on a tripod at some nice dark campsites here in Oz, I've not done astronomy for a while, so many other things on the go, but it's time to get back in the saddle!

I sold my big guiding setup some time back and now just rely on the SE4 mount and FZ200 camera. As the camera is very light, it works great on the SE mount, which has a built in wedge for equatorial mode. Despite the small sensor on the FZ200, it zooms up to 600mm at f2.8 so exposures can be shorter/lower ISO. It also shoots 14bit RAW, exposures up to 60s.

Being 'into' technology and stuff, my next challenge is to see if I can autoguide the SE mount using a, soon to arrive, Windows 8 tablet!! Including running Cartes Du Ceil to control the mount.

The first challenge was remembering how the heck did I use to connect to and control the mount! After sometime  rummaging around in boxes and my brain I got all the hardware and software together and successfully connected using ASCOM and a serial cable to the handset.

The next hard bit was finding guiding software than ran on my Win7 PC (and thus hopefully Win8).

No luck with Guidedog, PHD ran but couldn't control the mount as it wasn't pulse guiding compatable, finally an old version of Guidemaster actually ran and had the option to disable pulse guiding, first success.

Next a guiding camera. I have a Samsung long exposure CCTV camera mated to a Canon 55-250mm lens which I've used previously though a video-USB converter. This is a bit big and clunky though.

For the sake of a compact and simple setup, I tried out an old Logitech Quickcam 4000 (with a CCD sensor). Unfortunately for the quickcam, technology has moved on and a cheap Ebay CMOS webcam is just as good in low light, but not nearly good enough. I could long exposure mod the Quickcam, but it's a lot of messing around and current tech webcams could be better.

So I settled on the Logitech C270, which had good reviews and was only $38 (about 17 quid).

First tests of the C270 show low light capability to be outstanding. In a dark corner under my desk, it was able to make out details that I couldn't see with my eye. It has full control over exposure down to 0.5s and gain (these aren't accessible from the Guidemaster interface, but are from the Logitech control panel).

Unfortunately, it's not a standard M12 screw in lens on the C270, but it dismantles and detaches quite easily. So next step tonight is to mount it up to the Canon 55-250mm lens.

I'm hoping, fingers crossed, to pick up the tablet tomorrow. So will update my progress once I've figure out how to use Win8!!

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ok, so here's the modified C270. I initially tried with the Canon 55-250, but with the small sensor crop factor, it was equivalent to 778-3535mm! To much for guiding and the lens is a bit slow at f3.5-5.6. 

So I found that a standard 12mm lens fixing attached using the existing holes in the PCB to which I screwed a 2.8-12mm F1.4 zoom lens (170mm equivalent). Much brighter and a reasonable zoom (considering I'll be imaging at 600mm max). I have a 5.6-25mm F1.4 lens on it's way, so that might be better at 340mm equivalent.

The low light performance seems extremely good with this lens, noise is well controlled, even with the longest 0.5s exposures and gain to max. On the next clear night, I'll see how many stars it picks up.

It's a nice compact unit, barely adding any weight to the mount.....

P1050967.JPG

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ok, for the hoards that are following this.....after some tinkering with the tablet and learning windows 8, it worked! The tablet can now auto guide the SE4 mount via USB-serial and ASCOM using Guidemaster.

No issues with CPU performance, only utilizing about 15% whilst guiding, with CDC running too, see below (webcam pointing at a starfield on CDC on the desktop PC)

It looks like a clear night tonight, so once the kids are in bed, I'll see if the webcam can pick up any stars. I really need the 25mm lens, but will try the 12mm for now.

P1050970.JPG

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ok, I missed the clear night due to sorting out an issue with guidemaster. It suddenly decided it could not open my capture device (the webcam). So I spent most of the night uninstalling and reinstalling stuff, which didn't work (everything else could see the camera).

I decided to do a recovery from a saved system backup, which didn't work either, then a resintall of Windows 8 didn't work and the tablet was bricked!

After lots of internet searching, I tried disabling secure boot and finally managed to reinstall Windows 8, phew!

So a few hours later, I was back to where I was with Guidemaster. It worked once and then again it could not see the camera.

I was running short of ideas, none of the other auto guiders would work with my mount, saying it does not support pulse guiding. Then I stumbled across some info about PHD which mentioned setting the mount in the ASCOM settings to EQ. Doh, all along I had it set to ALT/AZ.

Finally, PHD worked with my mount, hurraaa!

So now everything is working, along with PHD. Back to waiting for a clear night to try the webcam. Everything is now assembled on the SE mount, so I'll post a couple of photos of the setup. Maybe it could qualify for the worlds most compact auto guiding setup!

I also modified a USB cable, which will power the Tablet through it's USB port whilst using that same port for the USB hub.

One thing I noticed with the little webcam zoom lens is; it may be F1.4 at its wide and, but (of course) this drops at the telephoto end, down to what I'm not sure, but it was noticeably darker, about F3-4). I managed to find a UK Ebay store which has all sorts of lenses (Australia doesn't have this sort of thing) and found a 35mm F2 fixed telephoto lens for the webcam. So not only a decent focal length, but also quite a wide aperture and only 23 quid. So it's ordered and on its way.

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Still waiting for a clear night.

Whilst waiting, I tried astrotortilla plate solving on the tablet using a photo of the milky way I took with the Fz200. It solved it in 20s, not too bad considering the amount of stars in that image. Couldn't get it to sync the mount and cdc correctly though.

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well you wouldn't believe the technical glitches I've had...maybe you would actually.

After testing the setup all week indoors and it proving totally reliable, the first clear night came on Thursday. So I moved it 4m from the spare room to the driveway. All setup ready to go, tried to connect the camera in PHD......can not open capture device....what the....

I try 3 other webcams, all good. I try this webcam in an Android tablet, all good. I uninstall and reinstall drivers, still same issue. Even other capture programmes can open the webcam, but not PHD and just not that specific webcam which I want to use..... so I give up and go to bed.

Friday comes, another clear night and I've attached the zoom lens to a different webcam this time, although not so good in low light. Everything is working again. I move it the same 4m outdoors, switch on......this time the SE mount says - cannot verify packages....what the.....it's never happened before.

So I spend that clear night trying to reflash the SE mount, which took most of the night.

However, I did get to try out the replacement webcam. Whilst it was able to see the brighter starts such as Vega and Altair, it wasn't able to see much else, so could be a bit inconvenient for finding guide stars.

I made the decision to use the Samsung long exposure cctv camera (SBC-???) instead, as it is amazingly sensitive and always finds a guide star without having to move it. Additionally, I can see what I'm about to image live on the tablet.

But getting a video capture device to work with Win8 was another challenge. After faffing around with 2 of them, I found the Aldi Tevion DVD maker had a Win8 driver online and all seemed good.

So I setup the mount indoors (as it's now cloudy again) to align the CCD camera with the imaging camera. Open PHD and select the capture device......can not open capture device.....what the.......

I was beginning to think it was some kind of practical joke. Everything else could open the capture device including Maxim DL and Metaguid, just not PHD, guide master and guide dog. Again, I tried uninstall/reinstall, no luck.....I was about to give up when I tried 1 last thing....I changed the USB port on the hub for the USB capture device.....low and behold it worked!!! What the.....

So it seems that whether the capture devices (and possibly the original webcam) only work with PHD when in a specific port on the USB hub! Isn't technology great!

Right, so now it's apparently all working and I'm waiting for the next clear night........to find out what has stopped working!

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  • 5 weeks later...

hi

how are things going with your setup?

just found your thread and am so happy to see that i am not the only one trying to do something like this :-)

i have the smallest nexstar GT mount (on a home made wedge) and want to image with it at dark sky campsites (i am based in perth in oz) but never managed to guide this mount because of lack of pulse guiding kind of issue...

that is why i am curious to hear how it goes for you.

so please update the thread with your findings!

thanks mate

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