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Posts posted by AlentejoSkies

  1. I'd also add that it's good to use what you have - almost whatever you have - for a while and develop a sensitivity to what you want to do next (although it's for sure also good to ask advice so that even if you take the next step quite quickly it will be a good one...)

    • Like 1

  2. What a great night that was.

    Out with my 6 inch f/8 dob watching the planets, first time for a while that I'm on my own so I get out the special reserve kit. Most of the time I'm showing others the sky and there I soon found that people see more with the most basic equipment. But today I can use the binoviewers, push the magnification a bit and take the time to watch, not just to look.

    Jupiter to start. Everything working okay, tube is cool. Seeing is really good ! 6mm SLV showing its worth for the first time. I have a lot of experience in optics but very little in astronomy, so each observing session is a revelation and coming together of theory and practice. When I got this eyepiece last year I just couldn't handle it, thought is was a poor match for the OTA, but now I love it. Learned so much over the last months, just basic stuff like tube-nudging technique, careful focusing, relaxing the eyes...

    So now it's time. It's after midnight and I want to see Mars. And there is detail tonight!! Not a lot, but there is a grey bit, and there white!! That counts as detail.

    Saturn. Low, but let's have a look. 6mm in. I have my first confirmed Cassini Division sighting! A defining moment for a novice observer. It's undeniably there. But at f/8 the 6mm is probably pushing it a bit, I want to try 8mm. Only way at the moment is WO binoviewer with two stacked 1.6x barlows, so I guess we are at about 8mm focal length, that's anyway the only way to reach focus with the binoviwers. Wow, wow, wow, Cassini confirmed and more. Saturn is pink compared to the rings. There is structure visible, this is unbelievable! Saturn is crisp and clear like it's just been born.  I never knew my scope could do that.

    Those WO 20mm wide angle eyepieces in the binoviewer are good I guess, and the Barlow too, but it can't be that they are better than the SLV? Surely not massively better. Is it the advantage of two eyes? Am I somehow able to do better internal image processing like this (or did the seeing just suddenly get really really good?)

    What has changed over the months? Mostly me I guess. I know a bit more what to look for, take a bit more care. I was also watching Saturn last night, not  just looking. There were moments when I forgot to anaylse the image, and just watched the planet from curiosity, and suddenly I saw details jump out as if seeing a friend's face in a new light.

    So I had to start the day by writing. Anyway a bit tired to jump straight into work. Thanks for listening.


    • Like 7

  3. Thanks guys, never gave this a moment's thought before, but for the last few sessions I've been trying it out.

    Both eyes open gives me a kind of spaceflight feeling, with the starfield superimposed on 'normal' reality. Very interesting. But not yet the easiest thing.

    One major benefit of spending time watching the heavens is that I have become a more perceptive observer of my own vision.

  4. Experimenting again last night, got some fantastic views of Jupiter at about 180x using two stacked 1.6x barlows. It's the only combination I have that reaches focus. Tantalising that I can't try lower magnifications without making some modifications. I am very tempted to move the primary up a bit...

    My second scope, the first refractor, coming next month with 80mm focuser travel will give a bit more freedom to play around. I think with a 1.25 " prism diagonal I should reach focus with no barlow, and see how those 3D star fields look like.

    It was a really calm night last night, which contributed a lot to the great view, but it was also very noticeable that I was staying at the eyepiece much longer and enjoying it more with the two eyes.

  5. Ouch, thank you Louis D, there is an issue... I need to re-check the calculations but it seems like the fully illuminated field falls to almost zero. And I need to think a bit about the effect of that - or maybe just try it out. I think that I will try it out for a while as things are, moving the primary temporarily and if I still like it as much after a few months as I do now, start redesigning. At the moment it seems like the advantage of the brain having two images to work with is so significant that it's worth rebuilding specifically to make that work as well as I can. A one-way trip indeed!

  6. Hi,

    Just taken delivery of a mint used William Optics binoviewer (Thanks Wayne!) and it's wonderful.

    I want to use it for now on my homebuilt 6 inch f/8 dob. I have no problem with cutting the OTA a bit shorter, but I wondered how people manage to combine binoviewer and single eyepieces. If I move the primary up 100mm I can use the binoviewer with the supplied 20mm eyepieces, but will have no way of reaching focus without it. I can add the 1.5x Barlow to the binoviewers, meaning I only need to find 50mm, or increase Barlow power by stacking a couple of units, to make it almost parfocal with single eyepieces, but rather inelegant, and only high power.

    Do you binoviewer experts out there shorten the OTA and use extension tubes when not using the binoviewer? Or always use the binoviewer and buy two of every eyepiece?

    Focuser is GSO single speed Crayford with 32mm total travel.

    Thanks for any advice,


  7. Ideal would be EQ5 head with RA drive, on 2" stainless legs.

    I'll be using it purely visual with a long tube 4 inch achromat (6kg) with binoviewer, and often with groups of children. Open to suggestions.

    Could collect from SGLXI.


  8. A fantastic night over here in Southern Portugal. Clear and mild. Moon a lovely orange transparent floating precious gem set amongst diamonds. Probably my favourite view was through the 10x50 binos, and just beautiful too with the 38mm SWA on my 150mm f/8. We had six children and a bunch of adults here passing the binoculars around and taking turns at the eyepiece, my 3 year-old asleep on a mattress outside with us.  Really really great night!

    • Like 3

  9. So, new telescope, lunar eclipse on the way, good reason to get up in the middle of the night.

    What else would you take a look at if you were out there with a few friends in the wee hours of the morning? I reckon we won't want to spend the whole night with only the moon, but how bright is the red moon anyway? What is likely to be visible?

    6 inch f/8 dob and low light pollution

  10. Hello and thank you for this forum. Only joined today but I've been reading for the last few months as every astronomy question I've had so far seems to have been asked and answered here.

    Just finished building my first telescope, a 6 inch f/8 dob from a second-hand mirror set of unknown provenance, and I'm quite happy with the result. What I thought would be a weekend project (I mean, what's so hard about putting two mirrors in a tube?) took me 3 months in the end even with - or pehaps because of - a strong background in physics and optical design. But now I am a telescope owner/maker and the world is good.

    Living in rural Southrn Portugal where the sky is fantastic. Nearest streetlight is a few km away...


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