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  • Telescope mods, colours in the sky

    I have added a couple of important mods to my scope and mount. One is motor drive in the declination axis which is the next step toward full remote control pointing capability. The other is a good size finder scope that is coupled to a web cam with software that automatically guides the telescope. This corrects any errors in the mechanical drives and will allow for much longer exposures. That in turn makes it possible to photograph very faint features not previously possible.

    As luck would have it as soon as I had these mods ready the weather turned cloudy and it wasn't until Wednesday night that if finally had a chance to calibrate and test the autoguider. It works very well. I still have some items to sort out but the preliminary results are very positive.

    These are the two changes to the scope. Bottom is the declination drive and the top shows the scope on the mount with the new finder scope. The finder is an LX-60 mm Meade refractor.

    Thanks to Duffy of this board I now have both high quality gearmotors for the right ascension and the declination axes as well as the ascension worm provided by him in exchange for various considerations.



    These are real images of two stars that illustrate how much the colour may vary. They are accurately calibrated to display the proper visible spectrum colours.



    This is one of my favorite targets, The Pleades.
    This image capturs much more of the very faint nebulosity than I have done before.


    This is a stack of very long exposures taken on the drive with a 28 mm lens on the camera. The number of stars it reveals is staggering. This is a section of the Milky Way that is an old neighborhood so the colours are heavily shifted toward the Type K spectral range. Our Sun is a type G which is a bright slightly pink white.






    In the works for this winter is a new 10" scope. I have a line on a 10" mirror at a good price that is speced at 1/20 wavelength surface accuracy. That is accurate to 1/40th of a micron. <grin>
    Last edited by Evan; 09-10-2010, 08:21 PM.
    Free software for calculating bolt circles and similar: Click Here

  • #2
    That last photo is awesome,really cool!

    What's the cap for on the DC gearmotor?
    I just need one more tool,just one!

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    • #3
      That last picture is superb!

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      • #4
        It's to reduce noise that interferes with the USB lines. I am running the USB devices at up to the practical maximum distance of about 30 feet. There are several caps on the motor of various sizes that together make for a broad band ac cut filter.
        Free software for calculating bolt circles and similar: Click Here

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        • #5
          Very nice photos evan.
          In laymans terms of 'I don't know a telescope from a black hole in the ground', Why is the first axis (the one with the tiny worm gear) of the scope at 45 degrees almost?
          Is there another motor or plan to motorise that axis?

          Again, total clueless at astrophotography, but would'nt a 2 axis mount be able to point at any point in the sky? Or do you need to actualy be able to rotate the camera too?

          Very strange axis arrangement. Must make for some intresting math to calculate how to make it move a certian way.
          Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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          • #6
            On one episode of a recent Science Channel astro physics program (of which there have been many lately), they were discussing the doppler shift, and how that had led to the understanding of the expanding universe.
            Is that why we see the different colors in your third photo.

            ...also, I've been noticing a very bright star low in the eastern sky the last several nights. What star/planet is that?

            (I claim zero knowledge of the celestial bodies, other than the moon and sun.
            Oh yeah, and the big dipper.)
            Lynn (Huntsville, AL)

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            • #7
              Black_Moons:

              The main axis is set to be exactly parallel with the Earth's rotational axis. That is equal to Even's latitude (He posted it once, but it is probably around 53-55*N). By doing that you only need to rotate on one axis to track the heavens. This is called an equatorial mount and is very standard in astronomy.

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              • #8
                Beautiful scope Evan.

                Are there any discussions on HSM that discuss its construction?

                TMT

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                • #9
                  ...also, I've been noticing a very bright star low in the eastern sky the last several nights. What star/planet is that?
                  It is Jupiter.

                  Is [the doppler shift] why we see the different colors in your third photo.
                  No. The doppler shift is useful for determining the distance of galaxies. Stars in our own galaxy aren't moving away from us fast enough. The colors are due to energy output and imply the life phase of a star. Red giants are enormous, old, and relatively cool. Others are young blue and hot. Our sun is middle aged and will eventually turn into a red giant.
                  Last edited by Tony Ennis; 09-10-2010, 09:52 PM.

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                  • #10
                    I built the scope before I joined this board so the construction hasn't been documented here.

                    There is more here:

                    http://vts.bc.ca/astrophoto/scope.htm

                    A related project is here:

                    http://vts.bc.ca/astrophoto/drive.htm
                    Free software for calculating bolt circles and similar: Click Here

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                    • #11
                      Great photos Evan. You are luck to live in a place where you can see the stars. When I lived in Idaho before I retired, I could set out in the hot tub and watch the stars and enjoyed the heck out of it. Now here on the Oregon coast only a mile from the ocean I very seldom get to see the stars, I miss them.
                      _____________________________________________

                      I would rather have tools that I never use, than not have a tool I need.
                      Oregon Coast

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                      • #12
                        The spider that holds your secondary appears to be the source of spokes in the point source objects in the images - do you suppose that is because of the two-layer/leg design? And I've wondered if taping the gaps would reduce that.

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                        • #13
                          I cut off one of the legs on each spider vane pair but it made no difference. The diffraction spikes are inevitable and cannot be eliminated except by placing the secondary on a glass plate. That then reduces the amount of light by at least several percent if the best possible coatings are used and over ten percent with no coatings. Even the Hubble shows diffraction spikes.

                          In this picture taken during the build you can see how little the spokes obstruct the primary. In order to eliminate the diffraction effect the spokes would have to be less than a wavelength of light thick. That would require a supply of unobtanium shim stock.



                          Here is a view of the present configuration.

                          Last edited by Evan; 09-11-2010, 03:08 AM.
                          Free software for calculating bolt circles and similar: Click Here

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                          • #14
                            Evan,

                            A SPUR gear for the declination axis ? Driven by a spur gear head servo motor ? YOU ??? What, you forget how to make a wheel and worm gear ?


                            Lenord

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                            • #15
                              Declination isn't for tracking, just for slewing. I have to add a slew motor for the polar axis too. That declination motor is geared down a LOT so it works perfectly. It slews at about 1 degree per second.
                              Free software for calculating bolt circles and similar: Click Here

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