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About hunterknox

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  1. I prefer cotton wool but each to their own. Look for “Cotton wool BP” on the label in the UK. BP = British Pharmacopedia = medical grade Light touch is a given but I also try to rotate the cotton wool as I move it across the surface so the overall effect is lifting rather than polishing. One swipe per cotton wool ball then discard. Imagine you’re a nurse trying not to cross contaminate different parts of the mirror surface. There used to be a great video online of David Sinden cleaning a refractor lens with the proper technique but I’m not sure it’s available anymore. My worry i
  2. Think about it like this: how much do you worry about your windows with all that intense sunlight bearing down on their massive surface area? Assuming you’ve got a standard refractor with the lenses at the front then the light and heat that hits the first lens is no more concentrated than it is on a window and on the second (or third) lens it’s slightly more so but not a big deal. As John implies: things aren’t getting too intense until closer to the eyepiece end and the Herschel wedge is designed to deal with the concentrated heat and excess light. The former doesn’t go round corners wel
  3. Thanks Shimrod - that looks like a backup option. 2kg is not that heavy in normal terms but not ideal on top of my other gear. Should have said I’m carrying everything off the beaten track so the lighter the better but I realise a compromise might be in order somewhere.
  4. I’m looking for an easy way to power my portable setup, which just means powering an Astrotrac and a dew heater, but I can’t seem to find a stock, light-weight battery that will do both. All the astro power tank stuff seems to either have 12v cigar sockets, or a small DC outlet, but not both. Happy to buy a new dew controller if needed but the only ones designed to power a mount as well as dew strips are on the massive side. Any ideas from the Lounge?
  5. Seeing as it’s likely out of warranty it can’t hurt to take a look. The PST uses a 5-sided prism to bounce the light up to the eyepiece. One face should be parallel with the front on the scope, one with the eyepiece. When you’re turning the focuser you’re just screwing the prism holder back and forth within the black box. The holder isn’t a great design. The prism is “pinched”, if you will, at the slides (like a litter picking claw might pinch some rubbish). It’s not a great way of securing something so it’s not unknown for the prism to slip a little which puts the whole optical alig
  6. I guess the seeing in York must be fairly stable - flip side of the fog you often get. Anything over 180x is a bonus for me but I don't think you necessarily need the highest magnifications for a reasonable star test. Glad to hear there are no optical horror stories thus far though.
  7. What? Problems appeared as I was typing? Sounds about par for the course. Still got my fingers crossed for you for first light though...
  8. Fortune favours the brave! I'm a sucker for alternative designs of anything. Very interested to see how you get on with this one...
  9. I think the phrase "primarily a visual instrument" comes from the original marketing info. I know a few people who've looked through them, myself included. If you can get excited about seeing a faint, featureless purple circle then it's a visual instrument. If you're a normal person then it's for imaging only. Great scopes, but only for a very small niche. I sold mine when I stopped imaging.
  10. Yep. Never really understood why people do it though, except in very specific circumstances (e.g. using a Daystar filter). If you're struggling to get a perfect circle for your aperture mask there was a guy who used to make Bahrtinov masks who traded on ebay as Morris Engraving. He made me a custom Hartmann mask for a very reasonable price so I'm sure he could do an aperture mask too.
  11. Weirdly my older Solarmax has a red front-end etalon and a red objective, so it might be that the etalons have ERFs up front but that they're not suitable for use without additional energy rejection components.
  12. Here's a solarchat thread on he same topic: http://solarchat.natca.net/viewtopic.php?t=4307&p=43819 In summary, check design specifics with the manufacturer but there doesn't seem to be anything intrinsically bad about using oil-spaced refractors.
  13. I suspect that any glass or oil up front isn't an issue - heat gets concentrated at the back of the scope and if anything the oil im a triplet might help to stabilise any temperature differential betwen lenses. That said I do believe that the earlier TEC 140s aren't recommended for solar viewing - something to do with the collet rings? Later versions had a different design and to say they've been used to impressive effect would be understating it.
  14. I would say no, the 66 is unlikely to be better for solar unless the opticstar's a dog. Aperture still rules for solar refractors and the magnification you can use is more likely to be dictated by seeing than telescope.
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