NEQ6 guiding failure after meridian flip

I’m using Kstars/Ekos to control my mounts and in theory it’s possible to set things up so the mount will automagically meridian flip if the hour angle increases beyond a certain value.

Having seen it in action it does look quite neat: the current exposure is completed, the mount flips, plate solves, makes any corrections and continues imaging.

Unfortunately in my case the guiding after the flip is beyond awful. I’d be better off not guiding at all. If I stop the imaging run and recalibrate guiding however, it then goes back to guiding quite happily at < 1" RMS. It occurred to me that sometimes when I plate solve immediately after a mount move, I get badly trailing stars in the image, but not in any subsequent images, and that perhaps these two issues are linked. I'm wondering at the moment if it points to a balance (which I doubt, as I think the balance is pretty good) or backlash/worm end float issue. More investigation required...

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On-mount USB hubs

With the proliferation of devices attached directly or indirectly to my telescope mounts it seemed sensible to consider placing a USB hub directly on the mount and running a single USB cable to the controlling PC, rather than having a cable running up the mount for every device. At the moment I have USB connections for the mount itself, filter wheel, guide camera and imaging camera, but I may later add a focus controller, camera rotator and potentially even have dew heaters with a USB/serial interface. If I get to the stage where things are very heavily automated I might even have controller devices for flaps over the end of the OTA for darks/storage and flats that are USB-connected.

Given the move to USB3 for many newer cameras it seems sensible to go for a USB3 hub, and with its own power supply rather than using parasitic power from the host USB interface. Startech were high up on my list to consider as they generally seem to have a good reputation, but they can be quite expensive. In the end I went for a seven-port USB3 powered up from Orico. I’ve had one of these on my desk for a few years and it has been utterly reliable. It also has an aluminium case with end plates held in using screws that might well allow for a proper mounting bracket to be fitted. And unlike the Startech hubs I was looking at which run off 5V and would require an additional buck converter to step down the 12V supply at the pier, the Orico hubs run at 12V and have a standard 5.5/2.1mm power socket, just like all the other kit on the mount. The main negative really seems to be the number of bright blue tell-tale LEDs (one for power and one for each USB socket in use). Some black insulating tape will probably take care of most of those.

For the time being I’ve just zip-tied the hubs in place, but they seem to be doing the job very nicely. Oddly I did find that my Atik 314L+ wasn’t even recognised by the USB hub in the controlling PC, but works fine with the hub. As it’s USB2 I’m not too worried about that going through the USB3 hub. Imaging cameras that are USB3 however I will still route directly back to the PC to try to avoid contention for bandwidth on the USB bus as much as possible.

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Missing icons in Kstars and Ekos

After installing Kstars and friends on my Mint 19 desktop from the launchpad PPA, I discovered that none of the buttons in the application had icons. Some were blank, whilst others had text overlaying them. I only actually realised this wasn’t intentional when watching videos about how to use Kstars.

Searching for possible solutions I found all sorts of possibilities mentioned, but what actually fixed things for me in the end was just this:

$ sudo apt-get install breeze-icon-theme

A restart of Kstars then showed all the icons, which makes it somewhat easier to use as the toolbars can contain many buttons.

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Success with libgphoto2!

Since the last release of oacapture I’ve mostly been working on oalive, an EAA-type application that will share a large amount of code with oacapture. One of the new things I wanted to do with this was to add support for DSLRs — initially Canon, but I’m hopeful that some Nikon and Sony cameras might work too, as I have further plans once I have DSLRs working. This isn’t particularly straightforward as there’s no direct support for this sort of thing from Canon on Linux (and I assume MacOS). However, there is an interface library that has been reverse-engineered (though isn’t desperately well documented unfortunately), so I’ve started getting my head into that.

For the first time tonight I have actually been able to connect from my Mint 19 desktop to my wife’s 1100D (my 450D is in the observatory and she’s not using hers 🙂 set the exposure time, ISO setting and so on, grab an image (a small part of my 3d printer through the nifty fifty lens, as it happens) and display it on-screen. Feeling quite chuffed with myself now.

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Rassin’ frassin’ satellites!

All astroimagers know they can be a pain, but was there really any need for this on the first sub of an imaging run?

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Swimming, 27th August 2019

Eeek! The moment I got into the pool today, I discovered that it was ridiculously warm. There was no chance of swimming a proper set, so I just got on with what I could. A quite unpleasant swim all round, unfortunately 🙁

USRPT distance this year: 172,900m
Total distance this year: 222,900m

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A couple of galaxies

A couple more images from the Photoline 72 and ASI174MM last night. No filters, as for the earlier image of the Iris. M51 is 30 minutes of 90s subs, stacked, stretched and cropped, but no darks. Looking at the full frame it’s quite clear darks are required, but actually I’m not unhappy with it. It’s also clear that this one needs a fair bit more focal length. The Triangulum is also 30 minutes, but 300s subs this time, and includes darks. Needs greater sub length I think.

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A quick snap of Caldwell 4, The Iris Nebula

Whilst the 80ED was working ok M27 last night, I had a bit of a play with the Photoline 72 and ASI174MM. This is 75 minutes of 300 second subs. No filters as I only have one set, but I did take darks for this one. What’s intriguing me is the apparent diffraction spike on a single star to the bottom left. I haven’t worked that one out at all yet.

I have the TSRED 279(?) reducer/flattener for this OTA, and I think ideally it needs it. The frame is slightly cropped to remove the edge artefacts from stacking, but the stars close to the edge definitely look a little stretched to me.

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Start of a new M27

Other than a couple of weeks back as my first test from the new observatory, I last imaged this six years ago. It’s one of my favourites, so an obvious choice to revisit as I’m getting everything together again and ironing out the little niggles. Also trying to remember how to make everything work again, like merging the LRGB stacks together into a single image in PS.

But for the time being, here’s my luminance frame. 110 minutes of 5 minute subs from my 80ED (without reducer/flattener) and 314L+, stacked, stretched and cropped.

I’m not unhappy with it, though I think I need longer subs and more focal length (I think last time I used my 127 Mak). I’m not sure if I should pull the blacks down a bit to get a bit more contrast. But for now I shall go back to scratching my head at Photoshop.

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Waning Moon, 26th August 2019

I took 100 subs (1/500th @ ISO800) for this image at the end of quite a long night last night. The seeing had been excellent, but I’m not really happy with the outcome here. I think perhaps the DSLR doesn’t cope very well on images which are mostly black and then a small amount of very bright illumination. Preprocessed with PIPP, 40% stacked in AS!3, wavelets in Registax 6 and PS for the final tinkering.

I think it could be time for a change of technique for full disc lunar imaging. Perhaps switch to my ASI174MM and create mosaics or drop the focal length a little. Then I could use the DSLR for wide field instead. Needs a bit of thinking about.

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