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Merlin

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Everything posted by Merlin

  1. I've seen the Omicron2 white dwarf in a Prinz 60mm/f.11 refractor some years ago; it was more obvious with averted vision. The White dwarf orbits the red dwarf in 240 years and the pair orbit the primary in 8000 years. There' s all the time in the world in astronomy. As you say, this is an interesting trio, showing three stars in different stages of stellar evolution.
  2. One thing we can't avoid when hand-holding binoculars is the heart beat. I find that a triangular frame with hand grips at the bottom is more steady than a monopod.
  3. A solution I've found to keeping the weather out of the 8-inch Newtonian was to put an optical window on the front of the tube. I went to Asda's and checked out their clocks. I settled for a £6 clock with a glass front that, with its aluminium collar, is the same diameter as the tube. The collar fits the tube like a glove.The glass itself is very thin and very clear. One concern I had at having a DIY unworked optical window was the possibility of astigmatism. I saw no optical defects in moon and star tests. Purists might wince at the thought of making this mod, but it works for me. Of course, it's necessary to cover the back of the mirror cell too. Cool down time for the 'scope shouldn't take any longer than for a SCT.
  4. It's been my experience that M33 is easy to see in the right sky conditions. Years ago, before the proliferation of insecurity lights, I saw this galaxy from the back lawn lining on my back with 8X40 binoculars. The Galaxy was so distinct that I thought it was a small white cloud and almost directly overhead. I checked a star map and saw that the "cloud" was M33.
  5. If you need a mirror recoat there's www.scientificmirrors.co.uk .
  6. For spltting close double stars we can go quite some way beyond the theoretical limit of magnification, as stars are only point sources.
  7. Lunt are good. I have a LS50f etalon attached to a small refractor. I can also double-stack it to the PST. I need a KG3 filter to replace the fogged one in the B600. I once bought a replacement from a British firm, but I can't remember who. They only charged £3 plus £2 postage. Can anyone recommend a UK supplier?
  8. Small 'scopes are okay for showing planetary details, but for deep sky objects, that's where a bigger 'scope comes into its own.
  9. I have a neighbour whose security light was ludicrously angled. I pointed out to him that security lights illuminate other people's premises making it easier for burglars to see where they are going. He saw the logic of that and has switched his light off altogether.
  10. I have a number of types of binoculars, including 7X50 and 10X50s. I tend to use the latter more than the former bins. The difference in magnification makes it more difficult to hold the 10X50s steady, so I mount them on a frame ( a monopod is okay ) with hand grips and find them much steadier. A 7X50 gives wider fields for comet searches, etc.
  11. Star images are stretched. It looks like the optics are out of collimation, but I'm no expert.
  12. Nice yes, but too small an aperture for serious astronomy. Give me a standard 8-inch Newtonian anytime.
  13. A main point to make with a new 'scope is to have decent eyepieces. Some cheap but optically good 'scopes are supplied with poor eyepieces. This can give the wrong impression that the 'scope itself is bad.
  14. Is there really much point in having a monster 'scope, if we are not doing research projects?
  15. The bins don't dew up David, as the y point downwards to the mirror. I've found that it's the diode that's sensitive, at about 5C, rather than the batteries. If I cover the diode for a short time with a fingertip to give it some heat, it comes on but only for a couple of seconds or so. There are laser pens that can take quite a lot of cold before wilting, it's just knowing from where.
  16. I use a laser pen on my bins on the homemade binocular mirror mount and discreetly. We might as well ban kitchen knives too if lasers pens are regarded as a bad thing. We are not the types who point lasers at aircraft. A problem I have with laser pens is finding one that doesn't wilt in cold weather. Can anyone recommend a good supplier?
  17. I've applied two solutions for holding my own 70mm binoculars. One was to make a triangular frame from a neighbour's discarded Zimmer frame, with the bins attached to a top bracket. Bicycle handle bar grips were push onto the tube bottoms. The second very comfy solution was to make a binocular mirror mount. This is a supremely comfortable way to scan the skies, if we don't mind an inverted image. A Newtonian reflector inverts the image and nobody seems to object to that.
  18. Add a foot-long extension to the top of the main tube. It's too short at the top, letting in stray light. They make the tubes short to make the'scopes look more compact. Place your eye at the extreme edge of the eyepiece tube without an eyepiece in it, look in andyou will be able to see outside of the top of the main tube. This is were lots of stray light is entering. I made my extension tube on the 8-inch Newt from rolled camping mat, lined with black art card.
  19. Come now Peter, There's no such thing as a Dobsonian telescope. Let's be more specific and give credit to Issac Newton. As we know,John Dobson knocked up a simple push'an'pull altazimuth mounting, and he wasn' t the only one to knock one up. I always find it irritating when retailers refer to "Dobsonians", implying that Dobson invented a type of reflecting telescope, although he was a good mirror maker.
  20. I have a homemade binocular mirror mount and can greatly recommend them. Anyone confined to a wheelchair would also find amirrormount convenient to use, by simply mounting it on a platform across their lap. Luckily, I was able to acquire a high-precision first surface military mirror for just £3 on a flea-market some years ago. It can take much higher magnification than binoculars can yield.
  21. Several months ago I saw a Opticron 8x24 binocular on a local flea market stall. The binocular was in mint condition with excellent optics and with good eye relief for a specs wearer. How much did I pay? Just £3.
  22. The last time I tried to donate a astronomy book ( in mint condition ) to the local library, I was told that it doesn't accept donations now. Alas, we are heading for a paperless library.
  23. I've had Rukl's book for many years. There could have been more text on the physical features of the craters rather than describing the characters that the craters are named after. For outdoor use, the plates should be in black and white. It seems to be more of an armchair book.
  24. I have several specs of bins collected over the years. l solved the shakes problem in two ways. Firstly, I made a triangular frame in aluminium from someone's discarded Zimmer frame ( I've since made a second one ) and pushed bicycle handlebar grips on the bottom. As we know, binoculars register every heartbeat, unless we have a cardiac arrest ( chuckle ), but a holding frame greatly reduces this. To remove the shakes completely, I constructed a binocular mirror-mount that takes a range of binoculars up to 70mm .
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