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Thonolan

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Everything posted by Thonolan

  1. No problem! The helical top of the ES coma corrector is very smooth in action indeed. Feels almost like an oversized 1:10 micro focuser wheel and doesn't need any kind of locking mechanism for any setting. I learned these coma corrector tricks from Don Pensack (Cloudy Nights forum) who is one of the most experienced observers I know.
  2. I don't have a Paracorr but as far as I know you can use it the same way. Insert an eyepiece and use the tuneable top until it's the correct setting. Assuming it's in focus, you don't need to touch the scope's focuser anymore. Whenever you insert another eyepiece you just have to use the tuneable top until the new eyepiece is in focus. That's the correct setting for it. This way you won't need a red light to see the A, B, etc, marks, and won't need to remember the settings for each eyepiece either. I see on your signature that you have TV eyepieces. Your 26mm Nagler needs setting "F" according to Tele Vue website. If that's the first eyepiece you're going to use that's all you need to know. Turn the tuneable top to F setting, focus, and when you're going to use a different eyepiece you just need to move the tuneable top until this new eyepiece is in focus as well. This is especially useful for non-TV eyepieces as there is no table with optimum settings anywhere for other brands.
  3. No, it doesn't work like that. You need different settings for each eyepiece (unless they're parfocal of course). It's very easy to use, even in the dark, because I use the helical top as focuser. Imagine you have a certain eyepiece in the corrector, of course correctly focused and with the proper corrector setting. Whenever you insert a different eyepiece, turn the helical top up or down until that new eyepiece is focused as well. That's the correct setting for it. I don't touch the focuser at all unless I want some very fine focusing that involves less than, say, 1 or 2 mm focuser movement. Please note that corrector settings would be wrong for subsequent non parfocal eyepieces if you use the focuser instead of the helicap top of the coma corrector. So you only need to know the correct setting for one eyepiece. And if you don't even know the correct setting for one eyepiece there's a way to figure it out. Screw out the helical until the lower part of it it's 13.5 mm above the lowest possible setting as showed on this picture: This way, the focus of the optical system will be exactly on the top end of the helical. I put a piece of translucent tape on the top end, and then, looking at a very bright object with the scope (I used Sirius, but it can be a bright planet or the Moon), I focus it with the scope's focuser on the "screen" created by the tape. The helical should be still at the 13.5 mm mark. Now, if you knew the exact position of the field stop of your eyepieces, without touching the scope's focuser at all, you'd have to screw the helical in or out until the focus is exactly where the field stop is. So, for instance, if the field stop of an eyepiece is exactly where the body of a 2" EP meets the barrel you wouldn't need to touch anything. But that's not always the case. For instance, I need to screw my ES100 20mm in about 10 mm from that position (so the correct setting is 3-4 mm above the zero point of the scale) until it's in focus. That means the field stop of this eyepiece is 10 mm above the point where the EP's body meets the 2 inches barrel. This may seem difficult or tedious but remember you only need to do it once. And believe me, once in the correct setting I can't see the slightest hint of coma in any of my eyepieces. Hope it is clear enough. It's not easy to explain something like this when you're not using your native language.
  4. That's right. For me that's ideal as my Skywatcher 10" dobsonian needs extension tubes for every eyepiece. Having the ES coma corrector I don't need them anymore - in fact there's still about 30 mm of spare in travel with the corrector attached. And it's a quality product. I couldn't be happier with it. Mine lives in the focuser so feel free to ask any question about it. There aren't many reviews of it as far as I know. Maybe I should write mine some day.
  5. Like this? Cooling down a big mirror with fans can make a HUGE difference at high magnifications. Didn't the scope include a light shroud?
  6. Yeah, those build quality issues are hugely disappointing. There are not many reviews out there but so far I had read it's an excellent design. However this seems to be similar to what it's reported from Explore Scientific dobsonians.
  7. Keep in mind you'll never be able to see the Andromeda galaxy as a spiral with a 18 inch scope. It's much bigger than the widest possible field of view with any eyepiece. What you observed is just the galaxy nucleus. Be patient. A huge dobsonian is not exactly the kind of telescope I'd recommend to someone without a considerable amount of observing experience.
  8. I love my SQM-L, and I'm regularly measuring the sky darkness (or brightness) during my observing sessions. My best readings are around the 20.90 mark which is not bad I suppose, even though I have to suffer some terrible medieval style street lamps nearby. Most nights it reads between 20.80 and 20.85. Waking just one kilometre away from the small village the sky darkens to 21.20, but there's nothing like the comfort of a nice home observatory.
  9. A superbly detailed report of a beautiful scope. I wonder if you've written any subsequent impressions elsewhere in the forum? Couldn't find any. I may buy a big dobson in a few months and I was already considering the combination of Sumerian and Nichol Optical. This is surely a reassuring report! Thanks.
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