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About rl

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    pershore, worcestershire, uk

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  1. If you're going to drop 500 quid then a few more details might help. What do you expect to improve by changing the scope? What other accessories are you using and can they be carried over to your new scope? For example, are you using a coma corrector and off-axis guider? These would go with a bigger Newt, but will the mount then be adequate? Personally I don't see a massive gain in going to a 8" f/5 Newt, or possibly even an 8"f/4. Would you be better off improving the camera or the guiding? An ED refractor in this price range will have a shorter focal length and larger field (and no diff
  2. This is the original version from about year 2000. Is there a Zygo certificate with it?
  3. Both mine are several years old. Both have the OO Crayford. They are manageable but could be better. One works fine providing you don't rack in too far (wherupon it falls apart). ..The other is either stiff and lumpy or too loose to be useful ..there is no really happy mean. I've tried a couple of the new ones and both have been beautiful..smooth and tight at the same time.
  4. I currently have both in my possession, both bought secondhand at prices far below the new rate. I'm currently pondering which one to keep. Nice problem to have.. The VX14 gives you the choice of mirror accuracy. I have the 1/10 wave and it makes a superb dob. It's the largest thing I can reasonably lift. Having said that, the tradeoff is that the tubes on the VX series are a little thin and prone to dents if you aren't careful. The CT12 comes as 1/10 wave as standard. I have the f/4 option. It is more rigid than the VX and less prone to dents. It holds collimation better if you'r
  5. As others have commented, the ES92 17 is a truly stonking lump of glass, IMHO better corrected than any of the ES100 range I have owned or looked through. I've detected Cassini's division with telescopes of smaller aperture than the eye lens on the ES17. Depending on your observing environment, the excellent eye relief can let in quite a lot of stray light if you happen to be afflicted by local street lighting or houses. I used to think that the Ethos was a bit tight on eye relief and wished for a bit more, but having owned and used both in a light polluted environment I think the Ethos r
  6. Aperture is king...except when you have to carry it around! I think you need to be very realistic here. Exactly how far are you going to be carrying the kit? Are you taking it to the park in a car and just lifting it out of the boot, or is it a bus job followed by a 200 yard hike? The bigger scope costs more, is more clumsy to handle in the dark, and will depreciate more after you've put a few dents in it at 2am. Got the T-shirt..I had (actually still have) a 5" f/10 refractor I took everywhere for years when I was in my 30s but it certainly gained a few battle scars on the road. A decen
  7. Basically it's all down to using a local atomic reference, which is not subject to drifts due to ageing or temperature..the atoms just work with absolute consistency for much the same reasons that the best clocks are atomic in principle. The basic principle of operation is pretty much immune to small slow temperature variations. A standard grating is subject to all sorts of environmental effects and such spectrometers are usually housed in air-conditioned rooms with exquisite temperature control, fixed down to vibration-damped benches. Yes, I believe you can get somewhere near the same sort of
  8. Some 25 years ago I had the privelige of working for Birmingham University Physics and Astronomy dept under the late Professor George Isaak, who, for the record was one of nature's natural gentlemen. The BISON group did a lot of the early work looking at oscillations of sound waves on the sun, from which models of the solar interior could be derived. We made spectrometers that focussed on a single atomic absorption line ( usually Potassium at 770 nm) using potassium vapour as a local atomic reference. The idea is to isolate 2 wings (called red and blue) as areas in the absorption line either
  9. Referring to the OP's comment about the possibility of using a 12" Newt on an AZ-EQ6...I've run an OO CT12 on mine successfully for visual but it's on the ragged edge. The OTA plus rings weighs in at about 16 kg. Add the Paracorr, and an Ethos 21 and you are are at the limit. And you need steps to reach the eyepiece because the OTA centre of gravity is biased heavily towards the mirror. It's not just the weight..the 12" OTA is so wide the centre of gravity is offset a long way from the mount requiring the use of the counterweight extension bar and 4 by 5kg weights. It does work, but it'
  10. Hmmmmm ..Interesting set of replies. Lots of support for the 21E, 13E,14 Delos, big Naglers, Pentax, Vixen. To pick on one eyepiece is probably a silly question (but I'd volte for the 21E), but maybe the best range is not. Funny thing is, in the 13 years since the Ethos line was first released, every serious manufacturer out there has cloned them and most reviews rate the clones nearly or as good as the real deal. And yet I see no votes yet for the clones...is this just a statistical selection effect or did Al Nagler get something very seriously right that's hard to match? I sold my
  11. A poor thing but mine own..an OO right angle finder. Can we have a thread for the silliest OTA- eyepiece combo? Can anyone match a 30mm ES 100 to a 60mm OG?
  12. Good job... I regularly used to split zeta bootis as a figure-of-eight with a 5" f/10 John Owen achromat when the separation was about 0.9"given decent conditions. It's worth making a drawing with companion stars in the field...in the future you can actually see the orbital rotation over a couple of years if you have a reference point.
  13. You will probably need to keep the Nagler just for a counterweight....
  14. I don't know the particular model you are considering but I've owned several WO scopes over the years...ZS61, ZenithStar 80 mk2, GT81 MK1, Megrez 72...all bought secondhand. All have had excellent optics. The astro-bling comment is valid, as is the criticism about the rate of change of models. There is only so many ways you can repackage an 80mm lens and make it look exciting and original by changing the paint job but they keep trying. But, Pandora bling apart, they are basically very good small scopes optically. Not all the focusers have been so good....as you're looking to use it for
  15. EOS1000D is good. I've got a pair of 1100Ds which have been very reliable. Canon seem to be the best supported by a long way from the astronomy point of view. You can get away without LiveView but it's really painful; I think all APSC format above 450D have this feature but I might be wrong on this one. Other than that they're all pretty much the same. Controlling it through a laptop is a good thing to do..screen is much easier to see. Spending a few quid on a 12v battery adapter is also worthwhile. Check the shutter count before you buy.
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