Jump to content


Rob Sellent

  • Content Count

  • Joined

  • Last visited

  • Days Won


Rob Sellent last won the day on November 14 2019

Rob Sellent had the most liked content!

Community Reputation

854 Excellent


About Rob Sellent

  • Rank
    Star Forming

Profile Information

  • Location

Recent Profile Visitors

The recent visitors block is disabled and is not being shown to other users.

  1. Judging by all the threads you've set up this week, I imagine you're rooting for some cosmic phenomenon that will indicate dooms day for Earth. To wet your appetite, have a gander at the life cycle of stars like the Sun or else massive asteroid impact.
  2. A megaparsec is a million parsecs (mega is a prefix meaning million; think of megabyte, or megapixel) and as there are about 3.3 light-years to a parsec, just one megaparsec is quite some distance. Now multiply that megaparsec by 900, 3,000, or what have you.......
  3. In a sense, to view the Sun in H-alpha I feel the question is to either go for a Quark eyepiece or a dedicated H-alpha telescope and to be honest I don't feel there is a correct answer. In general, one important feature in astronomy is aperture and this also applies to solar viewing in white light and H-alpha. Looking just at the Lunt scope (50mm & 60mm) one will find that they are beautifully designed H-alpha fracs and work exceptionally well. They have the advantage of being solely dedicated to H-alpha, need no time to be up and running (great for 'grab and go') and with something like
  4. We know that cosmic rays (atom fragments that rain down on the Earth from outside of the solar system) are constantly raining down on Earth. The higher-energy cosmic rays are generally reflected away by the Earth's magnetic field and atmosphere while the lower-energy rays can reach us on the ground. By all indication, this means that the planet is around 99.99% protected from space radiation. As you'll appreciate the quantitative biological effects of the remaining 0.01% cosmic radiation is poorly understood and is subject to ongoing research. However, we can make a plausible guestimate.
  5. My advice: stay active on SGL (probably not going to happen) find an astronomy club in your area and join it ask these people lots of questions at the club, watch folk use their equiptment find a mentor after a few months you will have a better idea whether AP is your thing.
  6. A lucky friend you have Not knowing what accessories the budding astronomer has already, and no idea of budget here are a few suggestions: cheap and effective seating arrangement (ironing chair, drum stool) an evening accompanied under truely dark skies donuts, snacks, sweeties hip flask (purely medicinal use only) proper red torch (not cyclist type) which can be suitably dimmed S&T's pocket sky atlas Baader solar film to make a solar filter equipment case keeping bits and bobs in one place Illustrated guide to astromnomical wonders (B
  7. Welcome to the forum For a very good introduction to astrophotography that will serve you well and will save you a lot of money by making sure you don't head off down some dodgy or misinformed lane or an expensive dead end with equipment - it's worth getting a hold of a copy of Making Every Photon Count by Steve Richards.
  8. I think a 3x Barlow would make a f/5 scope behave like a f/15. In effect, tripling magnification, reducing TFoV by a third and likewise the exit pupil. Depending on the Barlow you may need more out focus to accommodate for the narrower light cone being produced. A possible sollution is to unlock the Barlow-EP combo from the focuser and slowly bring it out and see if you can reach focus.
  9. In terms of visual reference, I tend to avoid images and focus instead on sketches from seasoned observers. Using them as a guide and understanding them as the best representation I'm likely to see myself. The linked video of Saturn probably presents a run of stacked images passed through some kind of software to tidy the image. With a power of 300x and an exit pupil of around 0.3mm it is not a handy guide for visual work. Nevertheless, on any reasonable night of seeing my 4" Vixen offered more visual information of Saturn this late summer than the video. However, no matter how muc
  10. In no manner has my own collection been as exhaustive or as profound as many of the other members'. My telescope history runs as: Tal 100 - my first scope purchased about twenty years ago. Built like a tank, good optics and well corrected f/10 achromatic. To this day, I still consider it a fine first time scope. Worth more than any asking price the Russian gem was donated to charity in 2014. TeleVue 76 - the little 3" is still arguably one of the most attractive scopes I've ever seen. Its primary function was for solar white-light but over the years I have grown to admire its night t
  11. From my understanding it takes a good few millions of years for a large mass star to gradually die, less than a quarter of a second for its core to collapse, perhaps a couple of hours for that shockwave to reach the outer layers of the star, a few weeks to months to brighten as a Supernova, and then it just fades away with time. I recall observing the supernova in Messier 82 a few years back but can't remember it staying bright in the sky for long. With the 10" in action if I said it lasted a few weeks, I don't think I'd be that far out. Anyway, here's an amazing extract of the death of a
  12. Just to add to the complication (bear in mind I do not own either type, so just going on numbers)... Weight - + 1 for Ethos Eye relief - + 1 for ES92 On axis - both Contrast - I've always been a sucker for TV's field fo view contrast, so I'm guessing + 1 for Ethos Re-sale - if you bought secondhand and resold, you really wouldn't lose out either way. Focal Lengths - +1 for Ethos (more choice)
  13. Thank you all for such great replies. Its interesting to see what you guys are using and how your eyepiece set ups are in a good state of flux and evolution. The secondhand astronomy market being so poor in Spain and so tricky either to buy or sell decent used gear, I tend to drift towards the dictum, 'Buy once, cry once.' I also try to buy eyepieces that are recognised as working well without any aberration or distortion in any focal ratio scope be it an f/4, f/5, f/6 or what have you. I've found that scopes come and go, but eyepieces more often stay. Like Stu, I have a full set of
  14. To the question 'what is maximum useful/optimal magnification?' There seems to be a whole range of ideas.... 0.45mm x aperture in mm. 2mm x aperture in mm/50x per inch of aperture. 1mm x aperture in mm/25x per inch of aperture. focal ratio of scope x2 / focal length of scope (2mm exit pupil). focal ratio of scope x1 / focal length of scope (1mm exit pupil). Half focal ratio of scope / focal length of scope (0.5mm exit pupil). TeleVue recommends 2.5x mm of telescope aperture. Experienced observers going way beyond even these limits etc and so
  15. Just thinking outloud. But it might be worth placing the eyepiece's barrel a little way out of the focuser (cm by cm) and see if it comes to or near to focus. If so, it might be a 'problem' with the primary mirror's placement. If it is possible, raising the primary mirror just a small amount towards the secondary (mm by mm) might help. P.S: If that sounds a but mad, it might be an idea to hunt down a local astro-club and get some of the regulars to check over your system. For sure, it will be purely a mechanical problem which shouldn't take too long to fix. P.P.S: Looking at the phot
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.