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Everything posted by AndyG63

  1. I started observing with a pair of 12*50s, and they are great for helping you learn your way around the sky. When I'm observing - my 5" reflector not aided by insane light pollution - I find binoculars very useful when trying to star-hop my way to targets. If you can mount them securely to something (cables ties to a camera tripod, maybe?) I strongly suspect you'll be even more impressed. Andy
  2. Component Shop (a UK company) do very good prices on sealed lead-acids & chargers, and their delivery service is quick, too. Not connected with this company - just a satisfied user! The basic rule of thumb(s) are: * Store the battery in a charged state. * Do not short the battery (do not connect the terminals together without a load). * Top it up when required. * Don't let the battery freeze or over-heat. * Battery capacity is measured in Ah = amp-hours. A 7Ah battery, for example, can nominally provide 1amp for 7 hours, or 2 amps for 3.5 hours. * Charge using a current (usually measured in mA = milliamps = thousandths of an amp) which is no more than 1/4 of the Ah capacity of the battery. (Our 7Ah example shouldn't use a charger capable of more than 1500mA output. Lower is best.) * To calculate charge time, divide the Ah of the battery by the A of the charger. (Our 7Ah example will fully charge in about 14 hours using a 500mA charger.) * You can overcharge a sealed lead acid battery, but they're fairly resilient and moderately forgiving. Put a timer on the charger - better still, unplug it once it's full. * If you're really not sure of the state of the battery, buy a cheap digital meter. Fully charged is usually around 13.2V across the terminals. Fully discharged is around 10.5-11.8V. Andy
  3. Perhaps the word "unbounded" is better than infinite? Andy
  4. You can have an infinite universe without copies of yourself/the earth in it. Think of the positive integers: 1, 2, 3, 4, 5... That's an infinite series, but it doesn't contain PI, any other fractions, negative numbers, etc. Andy
  5. Peak Oil. That, and innate human intolerance. (I'm an optimist, really!) Andy
  6. I see Penrose gets a mention. He's currently suggesting that when an ancient universe, all near-empty and "flat" from any local perspective, finally occurs, it's the perfect breeding ground for a new Big Bang. That's not doom and gloom! That's a cyclical process of continual universes. Lovely! :-) Andy
  7. I have always wanted to get a horde of "Apollo deniers" into a room filled with "Apollo astronauts found alien evidence" believers - and lock the door. Andy
  8. Massive thumbs up for this stuff. ...And it keeps me looking so young, too! Andy
  9. It IS cold. I was contemplating setting up the 'scope to see Venus this morning, but "minus eleven" (let alone the snow overlying sheet ice) put me off a bit! Andy
  10. For all the nay-sayers who moan about the "vast" spending on space exploration, I have to point out that every penny is spent on Earth - creating jobs, producing new technologies and materials; new scientific insights and theories. That's not so bad. And "vast" is not the right word. I see NASA's 2010 budget is 18.7 billion dollars = well under 3% of the military budget. This means space spending in the States is only around 16 cents a day for each US citizen: a figure virtually identical to US pet food purchases. Andy
  11. I've sky-watched since the the mid-seventies, and have seen nothing that couldn't be explained. Why is alien abductions always happen to someone else? ) (The Tornado jet flying across the Moon's disk as I watched one evening was quite a surprise, however.) Andy
  12. Hi Rich - you'll get stars down to about mag 13.3 or so if the sky's dark. Andy
  13. Worth remembering that you could leave the weights for an EQ mount in the car - and maybe the tripod too. A tube with a - for example - 5" mirror isn't too much hassle to carry around. Andy
  14. Great idea, but I've read that there's a technical point with the UK's power stations. You can't simply switch them all off at night, as there has to be some reserve on the go at all times - and running street lights is one practical way to soak up this excess. Andy
  15. A stunning picture. In answer to iamzoso60, the rim is generally 900-1200 metres above the floor, with some peaks, like those seen to the East, reaching 1800 to 2100 metres or so. Andy
  16. The Moon's synodic period is 29.5306 days. Given the diameter of the Moon, the "point of midday" moves at about 15.41 km/s around the equator. That speed, as you note, reduces with latitude, and it does it like this: V = 15.41*cos(latitude) So it drops to walking speed north (or south) of about 75 degrees, and becomes zero at the pole - there, you'd rotate, not translate! Incidentally, why use maglev? Why not just have a giant crawler-transporter wandering around a track of crushed regolith? I'm not sure what you mean regarding the dynamics of your 24-hour-day city's movement, so I can't comment on that. Meanwhile, for the fixed city at the pole, the sun and Earth would always be low in the sky - and occasionally dip below the horizon due to the Moon's axial tilt (1.54 deg) and orbital inclination (5.145 deg relative to the ecliptic). When the Earth was "up", you'd see it go through phases, and this would naturally change the amount of light cast by it. But for a full Earth, since it's about three times as reflective as the Moon, and around 13 times the apparent size, it could be 40 times brighter than a full Moon: a full four magnitudes, making it shine around -16.7. Easily bright enough to read small text by, and you'd have some colour vision too. Andy
  17. Surely that's just the apparent diameter of the secondary, as cast on the primary from an infinite light source? Andy
  18. I agree with cathalferris: I bought this same collimator for my Celestron and, worried about the process, I read up on the technique about twenty times before daring to take a screwdriver to the mirror bolts. But all went well - it's a joy to use. (And collimation frightens me no more!) Andy
  19. Hi Keiran - yes, the vacuum's a constant, but there's (initially) a 1atm differential between your lungs' contents and "outside". The flow would be outwards until your lungs reached a vacuum. This is interesting: So - breathe out! Actually, just open your mouth - the quotes come from this site, and there's a guide to how long it takes to lose pressure from various volumes. If my maths is right, your lungs will be basically empty in a fraction of a second. Once back inside with your hammer, however: ... you may wish to be on your own for a while. Andy
  20. Version 8.0 is the first CS version of Photoshop, released in 2003. Adobe are on version 12.0 (CS5) now. Andy, stuck with CS4!
  21. I've seen several Chinese lanterns over Airdrie on recent nights. Your description is bang-on. Andy
  22. I've read this "keep your mouth open" comment before. I believe it's akin to people escaping from submarines without breathing apparatus. As you surface, you HAVE to open your mouth to let the air escape in order to equalise the pressure. Burst eardrums are not at all pleasant. Maybe after half-an-hour or so you'd be wishing you'd put the factor-50 on - but for a few seconds I doubt you'd tan too much. Andy
  23. You might also have a problem (amongst all the others!) with your eyes if they've been laser-corrected. I know there are eye-distortion/focussing issues with artificially-thinned corneas at extreme altitudes, and there's no more extreme an altitude than a vacuum! Andy
  24. ...and while we're in the kitchen (!) is the water from my condensing tumble drier suitable for mirror cleaning? It is distilled (by definition) and it's certainly cheap and available. Andy
  25. Hmm ... I always leave my Newtonian pointing down, a little. Less chance of anything falling in (though don't ask me what possibly could!) and my (probably erroneous) belief that and moist warm air, when cooling, will not settle on the mirror, but pour out the tube. That said - and on deeper thought - it probably stems from my previous life as a TV cameraman, back in the days of plumbicon tubes, when it was deemed safer to lock a camera off pointing at the floor, than risk it getting a burn by pointing at a light. Now I am confused! Andy
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