MCinAZ

I'm curious to know how you attached the critter barrier to the floor joists. Are there cleats on the joists to support the plywood? This is a very good looking build. With some good weather, it looks like you should be able to finish the major work in a couple of weekends. Then it will be time to decide on an observing program which utilizes the facility sufficient to justify all the money, time and effort. After completing my last observatory, I found myself feeling a bit guilty if the roof wasn't open on clear, moonless nights. Perhaps you could take up occultation timing...

Be careful to avoid creating a water trap if you put the EPDM on the inside of the joint. Not that I've ever done such a thing, mind you. [Not after the first build, anyway.]

Current rating (as James is most likely aware) is a function of cable length, whereas voltage rating is determined by insulation material and thickness. Here in the US, 15 A circuits are generally wired using 14 gauge wire, while 12 gauge wire is used for 20 A circuits in residential applications. That's a relatively useful guide, but assumes wire lengths typically found in single family housing. A competent electrician will use larger wire to supply outlets at the far end of a McMansion. Cables for dew heaters, thermoelectric coolers, telescope drives and any other high current (whether continuous or surge) applications requires some forethought. It's never a bad idea to measure the voltage at the load end under operating conditions after (or even before) pulling a new cable if there's any question about series drops. As for conduits supplying the piers, my experience suggests making them plenty large and leaving a pull string in place. In the three years I had my last observatory, I changed wiring configurations at least half a dozen times as I added and replaced equipment. I supplied only low voltage to the pier, so I eventually needed separate 16 V, 12 V and 5 V runs in addition to a couple of separate USB links, Gb ethernet and one or two dedicated control/status cables. My conduit was about 60 mm ID, which was plenty for the cables themselves, but pulling the last few cables with connectors attached through the elbows was a bit of a challenge.

A nice looking build. For scale, how tall is the door opening on the west wall? I can't see well enough from the pictures if you have gussets at the top of the vertical portion of the rolling roof where it meets the pitched supports. I would be a bit concerned about parallel shifting under wind or snow loads without some type of bracing in the east-west direction. Of course, this may be addressed when you close in the south gable. Is snow load a concern in Somerset? It wasn't for the three observatories I built in the Phoenix area, but certainly is in northern Arizona.

How do you attach the OSB to the roof frame? Will you be using self-tapping screws driven in from the top, screws coming through holes in the framing from the bottom, or something else entirely?

It's been a while and many updates to VirtualBox since I've tried it, however I encountered no similar issues using PHD Guiding in a W7 VM with my Lodestar USB guide camera. I've since migrated to GoQat as it is a native Linux application. The latter requires a bit more tuning, but works quite well once the appropriate settings have been configured. In general, I've seen somewhat mixed results with USB devices and Windows software running in a VM. Prior to purchasing the Lodestar, I spent a fair amount of time trying in vain to get SBIG's drivers talking to an ST-i. Also no joy using a P & E microcontroller debug interface for some S08 development. Many other devices, among them several printers and my HP scanner, work as well from the VM as natively. Since I don't need to do a lot of hardware control from a VM, I don't worry about it too much, but if you have some hardware that must be hosted from the virtual environment, it's probably good practice to do some research to be sure it will work. A minor correction to an earlier post: VirtualBox is supported by Oracle, who also provide some proprietary (though free of charge) extensions.

Hi James, Collective reply to all three of your posts. First, as I mentioned, FITS would be great but I can post-process to create files in that format from TIFF. If you eventually add FITS support, that would be excellent, however it probably doesn't warrant special priority. Second, I was looking for something in the range of 50 frames per second. The number you determined is way better than good enough. A back of the envelope calculation indicates that more than 10,000 320x240 frames could be stored on a 1 GB RAM disk, so that may be an option for keeping I/O overhead from being a significant factor. A tmpfs file system is trivially easy to configure, and so long as one copies data to non-volatile storage after an observing session, that ought to be a reasonable path. Latest word I've gotten is that QHY has a cooled camera in the queue which may be a bit better for the type of work I'm interested in. I may wait a few weeks before acquiring a camera, but I hope to be using oaCapture at such time as I do. (Or, I may just get impatient and buy either an AS120MM-S or QHY5L II to get started, and move to a cooled camera later if there's sufficient reason to do so.) Thanks for the prompt reply to my inquiries. -- Mike --

Hi James, It appears that you've done excellent work and made remarkable progress on oaCapture in the year since you started work on it. In addition to planetary imaging, your program would be well suited for capturing speckle interferometry data sets. As with planetary imaging, speckle interferometry is a technique which combines data from many very short exposures of double stars to overcome atmospheric seeing effects. The processing steps are dramatically different, however the basic data capture task is similar. Cameras based on the ON Semiconductor (formerly Aptina) MT9M034 sensors, such as the QHY5L II and ZWO AS1200MM show signs of being very good choices for this type of work. As with most scientific imaging tasks, lossy compression is detrimental. In the oaCapture documentation, it is mentioned that TIFF image export is supported. For speckle interferometry, FITS files are ideal, however TIFF images can be post-processed to FITS without too much difficulty. Using your ZWO camera, could you provide an estimate of the frame rate one might expect with a very short (e.g. 1 ms) exposure time when exporting to TIFF. In addition to full-frame images, the frame rate for a relatively small ROI, say 200 x 200, would also be useful. I realize that there is some dependence upon the capabilities of the host computer, but any information you might provide would be valuable. -- Mike --