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hrgreen

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About hrgreen

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    Nebula

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    Cocoa FL
  1. It IS quick and easy to set up my basic scope. The construction is light enough that at 78, I am able to lift the Rocker Box and VMB with (full thickness) mirror into and out of my car, and mounting the struts/front ring takes only a few minutes. There is no doubt about where anything goes, and no adjustments to make except minor collimation. Installing all the accessories does take some time. A club member has a standard 18" Obsession and sets it up alone, but he carries the mirror separately. I'm not willing to handle the mirror, and I prefer to uncover it only after everything else possible is done, and cover it before any teardown. The UC's are made to nest into a light, compact package; standards would be too large for my car and too heavy for me. My operative question was "what scope would give me the most aperture, but be within my physical limits?" Hal
  2. Rob, I got the Nexus WiFi rather than getting a WiFi for the AN, so no. Read the CN and AF discussions on the Nexus; many prefer it. Hal
  3. A few additional notes I found it easiest to keep the VMB and Rocker Box together when moving the scope in and out of the car, although the rubber band method will allow me to re-assemble them alone. A little more weight to handle, but OK. I changed cars to the even smaller Prius C, which has almost no room behind the back seat, and found I could load everything after the seat folded down. I obtained a Nexus DSC/WiFi to use in place of the Argo Navis. I do like it better; got tired of spinning that AN dial and filling out names. It links to SkySafari 5 in my I-pad. The display is easier to read, and I have more choice of alignment stars. The scope has not shown any evils since I readjusted the bearing, but I believe with heavy local light pollution, it could gain from a larger light shield opposite the eyepiece. Hal
  4. My installation of the ServoCat Jr. drive system went well. StellarCat doesn't have a template or good photo for mounting the ALT motor on a 15 UC, but I was able to figure it out. I also realized that there is a disadvantage to the ServoCat. Normally, a person working alone would want the (Virtual) Mirror Box and Rocker Box to be separated for transportation, because together the weight is kinda high. But putting them back together is complicated by having to thread a cable the length of the lower ALT bearing while assembling, seemingly impossible for one person. I found someone has figured out a way to do it with rubber bands, so have to try it. I noticed that the scope could rock slightly in elevation when at low angles. It seemed logical that this had to do with the front upper bearing fold-out pieces not being aligned. I made a radius template, which showed one was off. Found that the hinge bolts were not fully tightened on that side. Took minutes to fix. Really like this scope and what I can see with it. Hal
  5. Thanks again for your replies. I don't have a good picture of the scope, maybe later, but there are some on the Obsession website. Faulksy, I have a Paracorr II, but have not tried it yet. Things have been looking pretty good without it, although I haven't looked closely for coma yet. Besides Televue EP's, I have ES 4.7, 8.8 and 14 mm 82 degree. These seem quite good. I want to compare the 8.8 to my 9 mm Nagler when I get a chance. The ES were bargains at the introductory prices, about $80, and I plan to keep them for public star parties. Hal
  6. One thing I didn't mention that makes setting up the scope easy is using Howie Glatter's 2" collimator and Tublug. These allow aligning the primary while providing a Barlowed target image easily seen from that end, without removing the shroud. They are very well made and make short, foolproof work of the job. I also have a crosshatch accessory that shows exactly the centering of the secondary. I highly recommend these. Hal
  7. Though I have had this scope for some weeks, there hasn't been a break in cloud cover until last mid-week here in east central Florida. Finally got first light. Dobs are new to me, so much to learn. The scope is mechanically an ideal compromise for me, as the Virtual Mirror Box is within my safe limit to lift (45 pounds) in and out of my small car. The ALT upper bearing is hinged, and can be folded, then the ring can sit on top, making a package that can fit into just about any trunk or boot. Also, being an f4.2, it doesn't require me to use a stepstool. Its truss design is made with quick but sturdy connectors using captive fingerbolts, and the trusses and ring are light. In other words, a good one-man scope. At home, I store it in a front bedroom with wheelbarrow handles installed, and having installed a few short ramps, I can wheel it fully assembled into my front yard. There are braces to further stiffen the ALT bearing if you see a need; I haven't yet. The standard 2" focuser is a dual-speed FeatherTouch. NO tools are needed for assembly. Everything fits the way it should. I ordered mine with 10K DSC's and the Argo Navis, which I'm still learning to use. I also installed a Stalk and StellarCAT's Powered Ground Board kit, to allow powering the Argo, secondary dew heater and fan from 12 volts, with complete cable management. StellarCAT originally designed the ServoCAT GOTO drive for Obsessions, and I'll be installing the Junior version in a week or two. Many don't feel the need for this, but I find that using high power without a drive keeps me unpleasantly busy. I picked the Junior because it is quieter, and my neighbors might thank me. The lightweight structure seems pretty rigid even without the braces, but not having owned any traditional Dobs, I can't compare them. The bearings seem quite smooth. The mirror is a Galaxy standard-thickness, but I ordered a premium figured one, with an interferometer-measured Strehl value of 0.971. Hudek supplies a comprehensive printout on request. There probably are few times local seeing will allow appreciating this, but I don't plan on ever replacing this scope, so I went for it. So far, I have had just time to look at the planets and a few globulars and double stars, using 8, 13 and 21 mm Ethos and a 4.7mm ES. The two nights were relatively dry and steady for Florida, and Saturn showed more ring and surface detail than I have ever seen, including on our local college 24" (which needs cleaning). Jupiter also, but I didn't have a needed neutral filter. M5, M13 and M92 showed more stars than I have ever seen. Star images both sides of focus looked good, The images held up well even at 340X. I come to this scope from a Celestron 9.25 HD on a CEM60EC mount, a very nice combo. It would certainly be better for AP, but I opted for visual, and this unit blows it away so completely for faint stuff that I am very pleased I made the jump. Hal Greenlee
  8. (Not being an optical engineer, I apologize if I have any of these details wrong, as I'm trying to quote info from the Zambuto site) The best measurement of the quality of a mirror is thought by many experts to be the Strehl ratio. A perfect mirror would contain 83% of the light from a point source within the first difraction ring. The Strehl ratio is the percentage (usually given as a fraction) of that 83% that a real mirror is measured to contain. An excellent mirror would have a ratio of 0.97-0.99, a very good mirror 0.94-0.97, and so on, down to a so-called "diffraction limited" mirror at 0.80, which actually is poor, and its faults are evident. The Strehl ratio is properly determined by measuring not just a few, but hundreds or thousands of points on the mirror surface. It supposedly will give the least ambiguous indication of the quality of an image a mirror can produce with extremely good seeing conditions. The problem is that Strehl ratios tend to be quoted that are calculated from P-V or other numbers by makers playing it rather fast and loose with their advertised specs. These involve wishful thinking, and are questionable. Other shops use modified interferomter measurements of relatively few points. This has invited criticism of companies; one comes to mind immediately that offers cheap Dobsonians. A precision interferometer is the only way to make many measurements in a reasonable time, and they are too expensive for many shops. If a shop has an interferomter, it should be able to offer the customer a computer-generated picture showing the shape of the entire surface, making obvious any zones, turned-down edges, etc. Temperature equilibrium and effects of orientation of the mirror can be plainly seen. The importance of the Strehl ratio is not primarily about how bright the focused image will be, but is more about how much light is diffracted outside the first zone that can degrade the contrast and sharpness. Other specs such as 1/10th wave are today considered outmoded because they can overlook problems. Disclaimer: I cannot say from personal experience that I could tell the difference between a 0.90 and a 0.97 mirror, especially under usual seeing conditions, Since proper Strehl testing requires costly equipment and experience, the prices "reflect " this. I personally would opt for an honest 0.93 or better. I paid extra for a Galaxy 15" with 0.971. Hal
  9. Two questions I have after reading all posts I could find. 1. The plate glass sandwich mirror is reported as unusually messy during cooling, and not as quick to stabilize as HO says. Do you find this? Have you had a chance to do star tests? People who do refiguring seem skeptical about them. Wonder if a Pyrex would be worth the higher cost. 2. Has HO listened to and corrected the mechanical problems reported? In particular, have they made the GOTO easier to install? How well is yours now working? Wanting an easily transported scope, I'd buy an Obsession 15 UC, but just too expensive, same with the Sumerian. The new ES and Skywatcher 18 UC's look interesting, but too soon for much feedback. Hal
  10. Received a CEM60EC three days ago. Weather not great, so I'm testing what I can inside. There is a new upgrade set on the website (529 I believe) for all four boards, and I had no trouble upgrading. Looks great so far, smooth and free of backlash. Hal
  11. Last month, I had my 925 CGEM working with a StarSense driven by a SkySync GPS. But on the 9th of this month, I got an Auto Align and stars were about right, but Jupiter was way off. I checked the GPS clock data, and everything was right except the year = 2012. Reboots didn't help. Switching to the RTC seemed to fix things. I sent a message to TeamCelestron, and found they know about a bug, but don't have a fix yet. FYI. Hal
  12. Wanting a better focuser for my CGEM 9.25 Edge, I had to consider whether using an eyepiece focuser would extend the back focus too much. The Edge 9.25/11/14 models are specd as having the best sensor image at 5.75" (146 mm) from the large adapter nut. Although visual is not as critical, I was getting very sharp stars out almost to the edge of the FOV with a Nagler 31 and a Panoptic 35 without a focuser, and didn't want to see coma, spherical and aperture reduction because of inserting one. The techies say that adding X amount of back focus is like adding 3X amount of focal length. I tried a Moonlite with 3.29" thread, a beautifully made unit. But the thickness did cause some noticeable deterioration. Plus, it was quite heavy. Moonlite was kind enough to let me return it. The dimensions and weight of the FeatherTouch 2008BCR with 3.29" adapter looked better, so I ordered it. With an Opt diagonal using a 2" nosepiece, I measure about 6.2" from the back to the 2" EP ring (with the focuser racked all the way in), only slightly over spec. And the FOV's still look very good. I recommend this possibility for Edge 9.25/11/14 scopes; don't think it would be as good on an 8. Hal
  13. I had problems with the SSA at first on my CGEM 9.25 because the Calibrate Center operation is not correctly detailed in the manual, and I managed to get the center set out of range (either number over about 1000). When I got that straight, I was getting offsets up to 2 degrees every time I removed and replaced the camera in the dark, where I couldn't see well enough what was happening. This proved to be because the camera dovetail had metal spurs sticking out of the screw holes and interfering with consistent mounting. Some filing and sanding fixed that. Friday night, I went to a star party and set up under about 80-90% cloud cover. Couldn't see Polaris, so just used my IPad compass. I tried Auto Align, not expecting it to work until things cleared more. It surprised me by breezing right through. Centering is now good enough for a 20mm EP regardless of sky quadrant. Hal
  14. I've been using an SSA on my CGEM 925 Edge for about 6 weeks, and am now getting good results. It looks for plate matches in four blocks of the sky, and if any rejects, it is usually smart enough to try a substitute. No need to do more than a rough polar alignment, and takes only about three minutes. There were two problems I ran into. One was when calibrating the camera to match the OTA, it is possible to accidentally set its logical center outside the sensor, killing Aligns. The clue is in the cal numbers, which should be less than 1000 or so. This can only be fixed by a new Calibrate Center operation, preferably on a star near the zenith. The other was inconsistency in Auto Align of up to two degrees after removal and replacement of the camera. I traced this to something I should have investigated sooner; the large camera mount dovetail didn't seem to fit the other half smoothly or completely. This was caused by spikes of metal left sticking out of the screw hole machine work. A file and emery stick fixed it. Hal
  15. What a great number of welcomes! Thank you all. Dana, I'm not a baseball fan. But Red Dwarf, two particular things impel me toward Spain. One is a love of Flamenco; I studied guitar with a very good player in D. C. before having to leave for Florida in '62. The other is your modern high-speed train system, as I am a model and prototype train nut. Proto Star, I'm also very interested in the "boats". My family was mostly Navy, and I had an uncle on the Squalus in1939. When the Nathaniel Greene (sp?) came to the port for missile tests, we traded the crew launch pad tours for a tour of their boat. Wow! I have clear sky until about 1 am, so....... Hal
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