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johninderby

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Everything posted by johninderby

  1. Gel-cell batteries (as used in power tanks etc.) should always be charged after each use, as if one is put away flat it can actually be ruined after just a few weeks. When the charge in the battery gets too low some of the cells can reverse polarity and then there's no way to save it. Cold also has a big effect on the battery. If the battery is fully charged and then kept indoors in the warm it can be stored for a year before it needs charging again. The worst thing you can do is to store the battery on a concrete floor in an unheated shed or garage, as even a fully charged battery can loose enough charge to permanently damage it in just a month or two. Unlike ni-cad batteries gel-cells have no memory effect so you can give them a top up charge whenever you want. Preferably with an automatic charger, but even with a standard wall charger you would have to leave it on for several days to damage the battery. John
  2. Hi There's been a lot of good advice in the earlier posts, but if it helps at all one thing to keep in mind is that the shorter the focal length (f5 for example) the better your eyepieces need to be. With the longer focal lengths such as f8 or more you can get away with cheaper eyepieces as they're much less demanding. Also with short focal length refractors colour and other aberrations will be more obvious unless you go for an APO type. A short focal length APO refractor with good eyepieces is a good way to go if you've got a big enough budget (more compact and portable and easier to mount), but you could also get a long focal length achromatic refractor with cheaper eyepieces for a fraction of the cost, even if it's not so convenient to carry about, and it would still give decent performance. John
  3. Other factors to consider. Compare the size and weight and portability of the two scopes. The 180 is going to need a much heavier mount. This may or may not be important depending on exactly how you're going to use it, but it's something to keep in mind. OMC OTA - 3.5 Kg Skymax 180 OTA - 7.8 Kg John
  4. There's a good review of the 250 Flextube Auto here. http://www.opticalvision.co.uk/documents/91.pdf The 300 Flextube Auto is reviewed in the August issue of Sky at Night. Regards John
  5. For some more on the book Amazon.com has some detailed info worth looking at. http://www.amazon.com/Exploring-Night-Binoculars-Patrick-Moore/dp/0521793904#reader I've got a copy myself and just got it down off the shelf to have another look through it. John
  6. The previous posts have covered the subject pretty well but have you thought of getting a suitable book such as "Exploring the Night Sky with Binoculars" which is a part of the Patrick Moore series of books? John
  7. There's also another way to think about it. Buy a decent zoom such as the Hyperion and take note of what focal length settings you actualy use the most and then buy a really good ep or two at those lengths. Could save wasting money on single eps that end up not being used. John
  8. I had the Feathertouch Microfocuser when I had my 8SE, best improvement I ever made to the scope. Worth every penny. And on the SE of course there's no problem with clearance when the OTA's pointing at the zenith. Doesn't just transform focusing, but almost eliminates image shift when you focus. The focusing shaft is held by two bearings inside the focuser assembly that keep the shaft in line. The stock focuser only uses one bearing so the shaft can deflect to the side. John
  9. How about a Televue Ethos zoom I'm not holding my breath. John
  10. The Speers Waler zoom is a very good one, but it's drawback is that it's very,very tall and the latest version is a bit pricey. See photo John
  11. Zoom eyepieces can be very good indeed. But do be aware that the words cheap and zoom don't go together if you want a good one. Best zooms: Televue Nagler 2 to 4 or 3 to 6 as they are as good as any Nagler for contrast and sharpness but do have just a 50 degree field of view. Baader Hyperion 8 to 24 Zoom. As good as the regular Hyperion eyepieces but it is a fairly large eyepiece. In general stay well clear of the eBay stuff priced at about £50.00 or so and save you pennies for something better. I've gone through a number of zooms but now just own the Nagler 3 to 6 and the Hyperion, definately keepers. John
  12. Telescope House usually has a sale over a bank holiday, so maybe the August bank holiday? John
  13. I've found that it isn't usually worth importing Televue eyepieces, at least not at the moment. When you add up all the charges UK prices are about the same as US prices. Although if the pound goes up against the dollar any more that could change. I wonder when Telesope House will be having their next 5% or 10% off weekend sale? John
  14. I just did a quick check and to buy the 13mm Ethos and 31mm Nagler it works out to aproximately £895.00 delivered with taxes , customs clearance fee etc. from B&H v £886.89 delivered from Telescope House. So it's actually cheaper to buy it from a UK dealer, as well as getting it in 24 hours. John
  15. You're comparing a mass produced dob with a hand built to order one so they're not really that comparable. There are a lot of observers that are happy with their 16" Lightbridges, but they will tell you that the optics could be better and the scopes need a lot of mods to get them working right. Most owners also only paid about £1,000.00 to £1,200.00 for theirs which made them a good buy at the time. However the recent price increase to £1,800.00 must be putting a lot of buyers off now. The cheapest OO with the 1/4PV mirror is a bit better than the Lightbridge, but it's when you go for the premium optics that they get interesting. The 1/10PV mirror is as good as anything that comes in an Obsession etc. you just can't get anything better at any price. The biggest difference between mass produced mirrors and premium mirrors is that the premium mirrors give more contrast, sharper images and will let you use far higher magnification. It's not unusual with 1/10PV optics to be able to use several times as much magnification as with a mass produced mirror. I had a 16" Lightbridge and replaced it with the 14" OO with the 1/10PV mirror. The OO is just so much better in performance, and also is more portable and easier to manage. I'm not against mass produced dobs, I've just bought a 10" Skywatcher dob with tracking that replaces an older Skwatcher one that I've allways been very pleased with, but my long term plans do include replacing the Skywatcher mirror with an OO 1/10PV one. John
  16. I haven't had chance to check out the tracking properly yet, but in a short test it seems OK. Bring on the dark nights! The solid tube OTA is actually about 2.5Kg lighter than the FlexTube so no problem there. The truss components weigh more than you would think. I have added some small counterbalance weights to the tube as I have added a heavier focuser and finderscope. John
  17. Make sure that they do one that can handle a northern latitude setting typical of the UK. I have heard of problems with this brand with this one particular point. John
  18. OK so Skywatcher doesn't actually make a solid tube Auto dob (at least not yet) but it is possible to come up with one. Just take a FlexTube Auto dob and a solid tube dob and swap the bases. The only change needed is to swap the tube mounting parts from the sides of the OTAs. The holes drilled in the tubes are identical so no mods needed, just a straight forward bolt on job. Everyone in the UK was out of stock of the solid tube 250PX so I got one from a German dealer, and it turned out to be one of the new ones in the Black Diamond finish. While I was at it I changed the focuser for a proper dual speed crayford and added a RA 8x50 finder and a laser finder and a mirror cooling fan. The carry handles on the tube came from WDS Ltd. The balance weights on the lower end of the tube are the Astro Engineering ones intended for their SCT balance system. The dual wheel locking castors make it easy to move arund. Very pleased with the end result as I prefer the solid tube and it looks as if it came that way from Skywatcher. Now all I need is some decent observing conditions.................................... John
  19. Solid tube Skywatcher Skyliner 250PX Black Diamond Auto dobsonian Details to follow....... John
  20. That loud crash you just heard is the price of the Meade ACFs hiting the floor. John
  21. EdgeHD Pricing Did some checking around and in the US the EdgeHD 8" for example is 14% more than the regular SCT. John
  22. Rother Valley Optics is still showing the Celestron Dual Axis Motor Drives at £97.87 http://www.rothervalleyoptics.co.uk/celestron-dual-axis-motor-drives_d3277.html John
  23. Re: MetaGuide and Hyperstar Have you tried joining the Yahoo group? http://ca.groups.yahoo.com/group/AstroGeeks/ Or contact the author Frank at freestar8n@yahoo.com John
  24. MetaGuide is the best one I've found, and it's free as well ! You just need a webcam. http://www.astrogeeks.com/Bliss/MetaGuide/ "MetaGuide is a web-cam based tool for precise collimation of the in-focus diffraction pattern of a star. MetaGuide also autoguides and has several novel features that allow optimal guiding of mid-range mounts under typical seeing conditions. MetaGuide can provide insight into both the optics of your telescope, and the tracking behavior of your mount." John
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