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davejlec

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About davejlec

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    Nebula

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  • Location
    Methuen, MA
  1. Hi Cuandur- Reading the last part of your post I'm thinking that you might have put your telescope out of collimation if you turned any adjustment screws- not to worry as re-alignment of the primary and secondary mirrors to the eyepiece is not difficult when using one of the basic tools, such as a Chesire, that insert in the draw tube of the focuser. Your 130 mm reflector can likely magnify up to about 200 power on the best nights ( 40x per 25mm aperture) but you will probably want to use 110-150 power for the clearest views on most nights. I use a 120 mm f/6 reflector for the brighter Messier objects, moon, double star and planets but can only push the magnification so much before the view begins to dim and loose resolution. Of course, checking up on the transit times of the planets will ensure you're observing them when they are highest above the horizon. A quality zoom eyepiece ( 8-24 mm focal length) might be a good investment if you'd like to use the highest magnification - usually the AFoV widens as magnification increases - in combination with a Barlow lens your scope would reach about 160 X. Best luck.
  2. davejlec

    Mirror Cell question

    If your prototype is for a 12" mirror, you may want to check out a double plate mirror cell design made from a high-grade plywood. A 6-point PLOP designed cell would be more than adequate to provide support, (esp. if the mirror isn't full thickness) Basically described, a top plate with 6 contact "points" pivots on a (20 mm or 3/4") steel ball bearing that is sandwiched between the top and bottom plates, recessed washers hold the bearing in position . The "points" can be short pieces of dowel that are screwed and glued to the top plate. The mirror is attached to the dowels with silicone- it's important to use removable spacers between the mirror and top plate until the silicone fully cures - this prevents any torsional stresses to the mirror and applies them only to the plate. The design also includes 2 edge support points for the mirror. 12.5 6point cell (1).pdf
  3. davejlec

    Eye relief VS fov. FIght !

    John, Good to know that about the AFoV's not always being as advertised. Wasn't sure if the 58 degrees were more than advertised or the 67 degree were less than advertised- thanks!
  4. davejlec

    Help!

    Welcome to SGL and congratulations on your first scope purchase! It's helpful ( and less frustrating) to start with a low magnification eyepiece such as the 25 mm- much easier to aim the scope at specific objects with the wider field and generous eye relief. Very rewarding to be able to match a sky chart with the actual sky and this is a great time of year with the winter constellations in view. The hobby really got started for me with a star map, a few astronomy magazines and moderately dark skies. Since you mention you've no experience with a telescope, here's your first observing task to tackle with your son - Locate a constellation or two and a celestial object or two and learn the names and location of a few bright stars. Know your celestial bearings ( N,S, E and W) and know how to locate Polaris, observe how groups of stars appear to move over a few hours in different locations in the sky and witness Earth's rotation. For terrestrial viewing your scope can probably be pushed to a magnification of about 80X before the image degrades due to atmospheric turbulence ( many spotting scopes magnify 60 X or less). Have fun and please report back on your success!
  5. davejlec

    32mm plossl vs 25mm BST ED

    I own 4 of the BST Starguiders ( 7, 9, 15 and 25 mm ). Surprisingly, I find that their 58 degree field of view is equal to or better than some older 67 degree Super Wides. The 25 shows a bit of astigmatism near the edge but not the other shorter focal lengths because they have one or two extra elements that essentially perform as a Barlow lens. The twist-up eye cup is easy to use- a no frills eyepiece. At 4 times the cost I bought a single 9 mm, 76 degree Morpheus ( 8 elements ) which is excellent in every respect, but the 9 mm BST is almost just as sharp minus the extra FOV.
  6. davejlec

    Eye relief VS fov. FIght !

    If you're observing in colder temperatures then having a little extra eye relief can prevent the eye lens from fogging. I think most modern eyepieces add an extra element or two to achieve this, plus apparent field is wider as well, compared to 4 element eyepieces. I own a few 58 degree AFOV eyepieces that seem just as wide ( maybe even slightly wider) than a couple 25 year old 67 degree Super Wide Angle eyepieces, so that's a bit puzzling to me. I wear glasses for driving but prefer not to while observing so extreme wide fields above 82 degrees wouldn't be for me.
  7. davejlec

    Mars is a dot on my 10" dobson?

    Try an off axis aperture mask made from cardboard if the full aperture isn't cooperating when planets are not far above the horizon. Use a large enough circular piece that completely covers the front end of the tube- a long strip of cardboard taped to this acts as a rim and fits over the end of the tube. Cut out a 3-1/2" to 4" circle that is off axis from center and in between the spider vanes- you don't want to see the vanes or the secondary when looking through the focus tube , if you do, you've cut the aperture too large.
  8. Hi Victor- Thanks for that 1st light report! Brought back a memory of when I had seen a partial solar eclipse with solar filters taped to my 10 x 50 looking thru a sunroof glass. Did not think of optical quality then and was just amazed that the calculated timing of the eclipse ( by a Sky and Telescope contributor ) was exact to the second! After I gave away the 10 x 50's to a neighbor I purchased a copy of the Helios Apollo 15 x 70 binocular, it's just branded differently - Orion Resolux, Astro Physics and other brand names all essentially the same binocular. The individual focusing does take some getting used to but I think is better suited for astronomy.
  9. davejlec

    learning the night sky

    I think finding celestial objects using nothing more than an atlas or app is one of the best ways to maintain an interest in the hobby. Apps are great for getting information like distance, etc., seeking out the object by star-hopping is the time tested way to become familiar with the sky.
  10. Sometimes an off-axis aperture mask can help to sharpen the views if your optics are not cooling fast enough and your observing time is limited. They're easy to make ( even from cardboard) . I usually use one for splitting close binary stars and for seeing sharper detail on the planets.
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