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Peter Drew

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Peter Drew last won the day on December 7

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About Peter Drew

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    Sub Giant

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  • Location
    Astronomy Centre Todmorden U.K.
  1. I think it is likely that the secondary/corrector assembly is preset at the factory and no user adjustment is provided. We have a donated Bresser version and this has the conventional Newtonian type secondary adjusting screws. Because of the design, you can't really use the usual collimating aids, I've found the best option is to use an artificial star and adjust the primary mirror cell screws until the defocused "star" image is both round and evenly illuminated at the periphery. I wouldn't recommend removing the corrector lens, replacing it accurately is likely to be a lottery.
  2. Peter Drew

    Observing Comet 46P

    Just in from a session on 46P. Found quite easily in 15x70;s depite not knowing its exact position. Found it again in the 80mm finder on the 20" Dob. In the 20" itself it was surprising that the comet didn't look significantly brighter, probably due to the higher magnification. The comet virtually filled the field of view, there was the suspicion of a tail but suspicians don't count.
  3. Peter Drew

    ST102 focuser movement

    As JamesF says, the adjustment facility is provided by the two very small grub screws.
  4. Lovely view of the conjunction here at 5pm in the 16" SCT, both easily in the same field at 400X. Very strong wind so unable to take advantage of what looks like good transparency.
  5. A "quadroscope", hmmm.
  6. Peter Drew

    Binoscope Project

    The 80ED's are not exactly equal in length but it's the photo that makes them look staggered. The binoscope in the background is my 6" F5 achro made from Skywatcher OTA's.
  7. Comet magnitudes are integrated figures, that is to say the magnitude is derived by compressing the surface area of the comet to that of a star which theoretically creates a brighter than observed image. Large faint comets such as this one have a low surface brightness which make them difficult to see naked eye. It would be better if comets were compared to galaxies, M31 is brighter than the comet for instance.
  8. Peter Drew

    Binoscope Project

    Trial parallelogram mount for my 80ED binoscope prior to making a heavy duty one for my 6" F5 achro binoscope.
  9. Peter Drew

    Splitting the Trapezium

    There can't be many F7.5 Newtonian reflectors with 35% obstruction?
  10. Peter Drew

    Polishing glass plates

    I'm a great believer in experimentation but my gut feeling is that this project isunlikely to be successful, not impossible but unlikely. The thicknesss to diameter ratio of the 400mm work piece to the 150mm diameter of the quartz flat suggests that even orbital polihing action could result in zones. Although quartz is harder than glass, all cutting devices are harder than the materials that they cut but the softer materials always end up blunting them. Still, what do I really know about this?. Good luck.
  11. Peter Drew

    Zoom eyepieces

    I've had a 8se for a few years now, the F10 works well with zoom eyepieces. A binoviewer is fantastic with this telescope on the Moon and planets. Welcome to SGL.
  12. Peter Drew

    200p/EQ-5 Battering Ram

    Does it work in Australia?
  13. Peter Drew

    New, cheapest Mars filter.

    I usually leave the light on in the observatory for observing the Moon and planets other than looking for planetary moons.
  14. Peter Drew

    Focuser slippage

    You just attach one end of a band to something on the drawtube such as a diagonal and the other end to a fixed item on the focus mount. with a suitable elastic tension, the load on the drawtube is balanced, resulting in a smooth slip free motion.
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