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About MCinAZ

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    Northern Arizona
  1. MCinAZ

    JamesF's observatory build

    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.]
  2. MCinAZ

    Equipment power supply

    You may want to consider consolidating to two supplies, a larger capacity model for the drives, heaters, filter wheel and focuser, and a smaller, very clean supply for the camera. While the camera will certainly incorporate internal linear regulators for the critical rails, keeping the input voltage as stable as possible can only eliminate some potential noise sources. As for voltage levels, I would review the specifications for each piece of equipment to be sure that you're supplying a value which is within design limits. Some telescope drives which will operate at 12 V can tolerate and may perform a bit better at higher voltages, but that may not be true for other equipment in your inventory. I've found re-purposed laptop power supplies to be suitable for applications requiring stable DC voltages across a range of load conditions. Most of your equipment won't be affected by a small AC component or occasional voltage spikes superimposed on the DC level, but it isn't a bad idea to measure the AC voltage level at the load end when everything is operating. This would be most important for your camera, but if you dedicate a good quality supply to that device, you should encounter no difficulties. As discussed in James's build thread, be sure to adequately size your DC supply cables if they are of any significant length to avoid series drops.
  3. MCinAZ

    JamesF's observatory build

    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.
  4. MCinAZ

    JamesF's observatory build

    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.
  5. MCinAZ

    Securing Obs roof from inside

    That building had a small roof, so I needed only four wheels to support it. Each had its own lift mechanism. I chose that approach because the observatory was in the Sonoran Desert where we get a lot of dust storms in the summer. It all worked quite well in the end -- the lift mechanism proved to be entirely reliable and I had no worries about rain or dust intrusion regardless of weather conditions. I bought a small (15 l) compressor to operate the pneumatic cylinders. Provided that I remembered to close the valve on the tank immediately after opening or closing the week, it stored sufficient air for three to five nights of use before needed to be repressurized. I helped a friend build a similar observatory, also in the desert, but we took the more conventional approach and used fixed tracks, relatively small gaps and baffles built into the trim to minimize dust intrusion. While that building doesn't stay as clean through the summer as mine did, the owner finds the level of protection to be adequate. If I eventually build on my present property, I won't go with the lifts. There is much less airborne dust here in northern Arizona and I'm convinced that careful design and construction are sufficient. Apologies for straying from the thread topic.
  6. MCinAZ

    Securing Obs roof from inside

    Though somewhat manual, I agree that turnbuckles are a good solution. I've used these on the two conventional roll-off observatories I've built. I recommend installing them at a about a 30 degree angle to horizontal. If you add stop nuts to the pair at one end of the roof, you can adjust then fix the close position, then use the other pair to pull the roof securely into place at the end of the night. Avoid light duty alumin(i)um parts you might find at a mass merchandiser. Though not on an observatory roof, a friend of mine had one of these fail when the threads pulled out of the Al block. The turnbuckle was used to set polar axis elevation on his German equatorial mount and the failure nearly resulted in his custom 0.35 m astrograph going all the way to the ground.
  7. MCinAZ

    Securing Obs roof from inside

    My decidedly low-tech yet effective approach. I should note that the building incorporated pneumatic lifts so that when closed the perimeter of the roof rested on a foam seal. The C-clamps, one on each side, were only needed to keep the roof from lifting as it could not roll when lowered. We saw winds one night in excess of 110 kph and everything stayed where it belonged. It was my intention to find something similar to the latches Gina suggested but the C-clamps worked so well that I never pursued the notion. And now that the observatory has been decommissioned, I have a nice set of clamps for my workshop. If I still had a workshop. :-(
  8. MCinAZ

    JamesF's observatory build

    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?
  9. MCinAZ

    Software for mount exercises...

    There's no need to go through the ASCOM interface at all. You can simply send serial commands directly to the mount. I've done this many times with both Gemini and A-P mount controllers as well as my Optec focuser using only a modem control program. I've also got scripts linked to buttons on my desktop which will send Park Home and Park CWD commands to my G11. An open-loop sequence script would be a trivial exercise in the Linux environment that I use, while closing the loop by reading status back from the mount would add only a bit more complexity. I presume that should be the case in Windows as well, though I wouldn't have the smallest idea as to how to go about writing one.
  10. MCinAZ

    Astrometry.net local (SGP) doesnt solve ??

    While I have no experience with SGP, I have solved a lot of images using both Nova (astrometry.net web based tool) and PlateSolve 3. PlateSolve is usually somewhat better at blind solving fields (no user-supplied detail regarding coordinates or image scale) and can often solve fields which Nova cannot even when very specific detail is provided. Unless things have changed recently with Nova, Dave Rowe's plate solution algorithm is clearly better. That said, there are some circumstances where PlateSolve fails to solve a field even given the exact center coordinates and image scale. This typically occurs only when a very small (< 1 arcmin) field of view is involved or very few stars are present in the image. I haven't used PlateSolve 2 so I don't know how it compares to PlateSolve 3. If you're using a planetary camera in long focal length optical path, plate solution may not be reliable, particularly where sparse fields are involved. There also seems to be a point where taking longer exposures to bring out fainter stars does little to improve the odds of a successful solution. I suspect this is due to the limiting magnitude of reference catalog data, which appears to be somewhere are 11 or 12 for both Nova and PlateSolve 3.
  11. MCinAZ

    ITMA - oacapture 1.2.0

    As it happens, I've spent the past two nights in the observatory now that it's cool enough to use it again for a few months. The new release of oaCapture came at a very opportune time, as I have used 1.1.0 extensively the past two nights. After installing the Ubuntu 14.04 Debian package on my Mint 17.3 machine, I had to take if for a spin since the sky is again clear here in the Sonoran Desert tonight. The ROI controls are much more straightforward (even if the "Use ROI" button appears now to be extraneous :-) and it's good to see the EXPTIME record in FITS headers, as this saves me a post-processing step. Having corresponded with James extensively over the past couple of years, I know that he has put a tremendous amount of time and effort into oaCapture. All of us who use his software owe him a debt of gratitude for taking on a very substantial task and staying with it over a long period of time. -- Mike --
  12. You can certainly use PS2 stand-alone. I would think in most cases it is more useful to use it as part of a tool chain, and that appears to be possible as well. Another alternative is the astrometry.net tools, either on-line or installed locally. Most of the time, the results are essentially identical, however I've found some particular cases (very small or very crowded fields) in which PS3 could determine a solution where astrometry.net could not. I haven't performed tests to see how well PS2 does in such situations.
  13. MCinAZ

    Free CAD Software recommendations

    I've found QCad to be a good option for 2D work. It takes a bit of time to become proficient, however once you learn how to use it, it offers a lot of capabilities.
  14. MCinAZ

    SGP and PlateSolve2

    After installing catalog data, I found that the M81+M82 and pacman images solved using PlateSolve-3.48 without issue. The other two solved after I manually entered approximate image dimensions. Curiously, when the pacman image is loaded, the image size dialog boxes are populated with approximately correct values. This is not the case with any of the other three files. Looking at your FITS headers, I don't see any obvious reason why the program behaves as it does.
  15. MCinAZ

    SGP and PlateSolve2

    Sky coverage should not be an issue. I've downloaded your files, however I've learned that my current installation of PS3 does not include catalog data. I have those files at home, but won't be able to install them until Monday. I note a slight discrepancy between the center coordinates in your FITS headers and those reported by Astrometry.net. This may be enough to confuse PS2. You might attempt a solution after clearing the coordinates loaded from the FITS headers. Don't know if that will remedy the issue, but its worth a try.

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