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johninderby

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Everything posted by johninderby

  1. The MPCC is really only needed with the 13mm, but helps a bit with 13mm +1.5 = 8.6mm. The 6mm doesn't need it. Televue recommends putting a 2" barlow into the focuser first, but as the Antares is very short it will fit into the Paracorr when the tuneable top is set to the correct setting, but I think it can just contact the Parcorr lens if turned all the way down so you have to be careful. That's correct. With the Baader fine tuning rings on the 2" barrel, which are needed anyway to set the MPCC at the correct distance from the eyepiece, there's enough room to fit the 1.25" barlow element in-between the eyepiece and the MPCC. Very neat and compact. John
  2. Hi I would put the AC710 as being tied with the Televue 1.25" barlow, which means it's about as good as it gets in barlows. If only Televue had made the barlow element removable. The problem with the AC710's clamping ring is that it won't work at all with the William Optics type tapered barrels. It can't clamp tight enough to contact the tapered part of the barrel, which means you'd have to pull the eyepiece half way out so that the clamp would be on the straight part of the barrel. Works fine with standard eyepiece barrels though. I had the 8mm Ethos as well as the 13mm but sold the 8mm (for nearly what I paid for it) and got the new 6mm Ethos. With the 1.5x it now gives me 4mm, 6mm, 8.6mm and 13mm and if I use the little 1.25" barrel extension on the 6mm there's 3mm as well which pretty well covers things at the higher powers. John P.S. All you need now is a foot thick reinforced concrete pad to put the scope on with the Ethos, 2" barlow and Paracorr and your all set.
  3. Hi I have one of the AC555 Magni-Max and have tried it and actually it's not too bad for a simple doublet achro barlow, better than expected and a bargain at that price. It would hit the lens in the Paracorr, although you could probably use a Parfocal ring (or two) on the Ethos as a spacer to give enough clearance. With a bit of careful measuring perhaps? The AC710 APO barlow is a bit more expensive than a Televue barlow (and I can't tell any difference in performance) but has the advantage of the removable barlow element. I haven't had chance to really test it properly yet but it is noticeably brighter and sharper than the Magni-Max which you'd expect at the price difference. John
  4. Hi I had the 13m Ethos - Antares 1.6x 2" Barlow - Visual Paracorr combination and found that while it worked it was just too long and awkward and more importantly HEAVY ! I sold the Antares 2" barlow and Parracorr and now use the AE AC710 1.25" Supreme 2x APO photovisual barlow as the barlow element can be unscrewed and put on any eyepiece making it a 1.5x barlow. Also bought the Baader MPCC. The new combination fits right into the focuser and more importantly hardly weighs any more than the Ethos on it's own, so I don't have to rebalance the dob. The Antares 2" barlow does work very well, but is not as good as the AE 1.25" barlow so I'm actually gaining in performance. The Paracorr and MPCC are equal in performance. The Badder 28mm and 14mm fine-tuning rings put the MPCC at the correct distance from the eyepiece and still gives enough clearance to use the 1.25" barlow element. This combination is also right for the 6mm and 8mm Ethos. The new combination actually saves over one pound in weight ! I also bought a Mogg 0.3x 1.25" Extension Tube as this can be used in-between the 1.25" barlow element and the eyepiece to make it a 2x barlow, although the MPCC won't fit as well of course. Unfortunately both the Antares 1.6x 2" barlow and AC710 1.25" Supreme 2x APO are only available from Scopes'n'Skies, not my favourite astro dealer but there seems to be no other choice. I'm very happy with the combination now. John
  5. I've got an OO 14" dob as well. It doesn't actually take much airflow to cool the mirror down, and in fact too much airflow doesn't work that well. If the cooling air moves too fast it doesn't have time to pick up heat from the back of the mirror. Hence the small size of the fan that OO fits. Yes some of the Americans do go to crazy lengths to cool their mirrors down. Still I suppose it gives them something to do when it's cloudy John
  6. Yes it won't do much unless it is blowing on the back of the mirror. Dust doesn't seem to be a problem, but if you're concerned buy a fan filter which is only a pound or two (PC case fan filter) and stick it over the fan. While the main point of a fan is to cool down the mirror quicker it can also be left running while observing if the air temperature is dropping faster than the mirror is cooling. So long as it doesn't cause vibration. One thing that is becoming more popular in the US now with larger mirrors is to have two small fans in the side of the tube that blow across the mirror's surface while observing. Apparently it keeps the air just above the mirror's surface mixed and stops a thermal boundary layer from forming that can cause distortion. Another approach is to suspend a fan just above the front of the mirror that blows down into the centre and again stops a thermal layer from forming. A bit tricky as you have to line up the supporting wires with the secondary vanes to prevent additional diffraction spikes. Hope I haven't confused you but there are a lot of ways to use a fan on a dob or newt. John
  7. The Antares 32mm Plossl is available from Rother Valley Optics for about £25.00 http://www.rothervalleyoptics.co.uk/antares-32mm_d1527.html They're a very good place to deal with, as well as FLO of course. You can get it a few pounds cheaper from ScopesnSkies but I would rather pay a few pounds more from Rother Valley Optics and get proper service. John
  8. That's why I went away from power tanks. The gel batteries are fine, but the chargers supplied (and on some tanks the internal charging circuitry as well) are so poor that it can be difficult to get a proper charge no matter how long it's charged for. I now use just the gel cell on it's own and use a proper charger. Result: my 7ah battery lasts about as long as a 17ah power tank. By the way if checking battery voltage with most regular voltmeters you won't get an accurate reading unless there's a load applied to the output. There are battery testing meters and some voltmeters with a battery testing function that have a load built in. The load can be anything such as a 12v light bulb, motor etc. Gel cells if left discharged will reverse polarity on some of the cells and result in a scrap battery, so always charge up your battery as soon as it's discharged. If stored with a full charge a gel battery is good for about a year before it's discharged enough to damage its self. John
  9. The only thing I will use is Baader Optical Wonder cleaning fluid as it simply won't harm any lens coating. Just make sure to only use their micro fibre cloth as theirs is ten times finer than a camera cleaning micro fibre cloth. Do blow any dirt or dust off first. Bunch up part of the cloth and spray the fluid on the cloth and then gently clean the lens with a circular motion using no preasure. Never spray the fluid on the lens directly as some could seep under the edge of the lens. I've used it to clean SCT and Mak correctors, Newtonian mirrors and even Ethos eyepiece lenses. etc. John
  10. I had a chance to try the William Optics SPL eyepieces recently and was very impressed. Good eye relief, not too heavy, sharp and contrasty. In use they just feel like eyepieces that cost twice as much. John
  11. Auto Shut-Off Finder True Technology 20/10 red dot finder http://www.trutek-uk.com/2010rdf/2010.htm Don't like the looks of the finder, but has some interesting features. John
  12. The Skywatcher bolt pattern is 85mm apart so you would have to enlarge the holes in your OTA slightly. The plastic plate under the focuser is just a filler piece to match the OTA and isn't really needed. Here's the installation instructions for the Orion Crayford (same focuser). http://content.telescope.com/rsc/img/catalog/product/instructions/29300.pdf John
  13. I think that the common view is that a 4" APO refractor is roughly equivalent to a good 6" reflector, which judging from my experience seems about right. Perhaps a better way to compare refractors and reflectors is by price and by what you get per £100.00 spent. I've got a small APO refractor, Mak and a Dob and each has it's own strengths and weaknesses. John
  14. Steve Here's a few questions (including earler question about removing OTA) about the new system, once you've had the chance to assemble one: Can the scope be used manualy, or only by the handcontrol? Can the OTA be removed? If the OTA can't be removed what's the total weight of the scope? What sort of power supply or battery capacity is recommended? John P.S. If the OTA can't be removed can a SkyWatcher Dobsonain Moving Trolley be coming soon?
  15. There is no real "right" answer as there's just too many factors involved. Theoretically it would be a refractor if you had no limit on your budget, but in the real world a reflector that you can afford to buy may outperform a refractor of the same price. While the reflector may not perform quite as well as an APO refractor per inch of aperture, the reflector is usually so much cheaper per inch of aperture that you can afford to go much bigger and therefore overcome many of the advantages of the refractor. Then there's the argument about an APO being sharper and more contrasty, but that depends on just what your looking at. The best scope is the one that you can afford and actually use. I'd quite like a TMB 20" APO refractor, but as it costs twice the price of the average house, oh and then add the price of the mount and obs to put it in, it would have to be a BIG lottery win to pay for it. John
  16. If anyone's complaining about the price difference for the Auto version vs. the regular Flextube, do you realise how incredibly cheap that is for a dob drive system? Bargain !!! John
  17. Hi Yes I agree. Why someone would be so concerned about any trace of an eyepiece having ever been used when it is a second hand used eyepiece I don't know. Maybe they just want to look at it instead of through it. John
  18. Yes it's stupid that anyone should bother so much about a couple of little marks. But for instance when I sold a few Naglers recently to fund buying two Ethos eyepieces I got so many enquiries asking "are there any marks on the eyepiece barrel" that I got sick of it and if I answered yes in the case of the one that did they would ask me if I'd take £40.00 or £50.00 less. Arrrrrrgh !!!! John
  19. I've been looking at the photo again to try and figure out how the OTA attaches. It could be that on the driven side there's a gearwheel monted on the OTA that would simply drop onto another gear in the base drive unit. Then the OTA could simply be lifted off without actually unscrewing anything on the drive side. Just the standard screwed in handle on the other side perhaps. John
  20. Yes the A&E barlow, but the problem with that design is that it doesn't work with a WO type tapered barrel. It can't compress enough to grip the tapered part of the barrel so the eyepiece just flops around in the top of the barlow unless you pull the barrel half way out so that the straight part of the barrel can be clamped.. The Baader uses a three point cam locking system. The advantage of the brass compression type is that it doesn't mark up the eyepiece barrel. Ever tried selling a top quality eyepiece with marks from screw type clamps? It can knock the price right down. John
  21. Baader does a self centering one in the 1.25" size called the Click-Lock. Part of their modular diagonal system. About an 1/8th turn on the locking ring clamps the eyepiece in three places. John
  22. The ADM is top quality, you do get what you pay for, highly recommended. I like the way it holds perfectly but doesnt mark up the dovetail. If you want something different there's also the Geoptik stuff that uses a dual clamping system http://www.bazaarbuilder.com/cgi-bin/nickaltair/myshop.php?catparid=320&merchant=nickaltair John
  23. It doesn't actually take much power to drive a dob, that is when it's perfectly balanced. I suspect that the Skywatcher system will be critical on balance. And also it is bound to be a simpler stepper motor system with basic encoders to keep the price down. When Steve puts up the specs and prices later today then we'll know which dob sizes will be available with it. The ServoCAT is a high end / high precision servo motor system that can handle a lot of inbalance, but then again comparing a £1,300.00 to £1,500.00 drive system to one that's probably worth about £300.00 or so would be very unfair. Still the new Skywatcher system looks promising as it would bring a driven dob within the reach of most users. John
  24. Judging by the carrying handles on the side it seems to confirm my first impression from looking at how the Alt drive is attached that once assembled the tube is not removeable and the whole scope has to be carried around in one piece. OK in the 8", manageable for many in the 10" but the 12" could be a problem for many users, that is if the 12" will be available with the system. Hopefully I'm wrong and they have made it possible to lift the tube off the base. John
  25. Hi Neil Get these handles from WDS Ltd http://www.wdsltd.co.uk/Handles%20and%20hinges/Handles/WDS8517%20Handle They're not cheap but are industrial quality. You will need one of the shortest handles and one of the longest handles. Make sure to order the version that has the black rubber covered centre sections. The long handle fits onto the tube rings so get the one that is longer than you need as they can be shortened to the exact length needed by removing one end and cutting the central "pipe" section. You will also need to get hold of two 8mm countersunk head bolts for the long handle. You won't need to remove the mirror cell but will have to remove the secondary mirror and vanes (easy job). Just keep the tube level and stuff the upper end of the tube with some old towels to prevent any bits going down the tube when you drill the holes for the small handle. Use some large diameter "body repair washers" on the inside for the small handle (available at Focus DIY etc). When fitting the handle to the tube rings just drill an 8mm hole through each ring and then countersink the hole on the inside of the ring so that the head of the countersunk bolt won't touch the surface of the tube. As the bolt is now "upside down" with the nut in the hole in the top of the handle it's a bit tricky to tighten up. I seem to remember wedging a flat screwdriver down the hole while I tightened up the bolt. If you need any more info just ask. John
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