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digital_davem

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Everything posted by digital_davem

  1. Given the amount of slop, i wont be locking them at all. Still don't understand why there so much movement. I don't think k the gears in this thing would be much use in a clock or watch....?
  2. When the locking clamps are unlocked, is the worm drive doing anything - it feels like it is bypassed.
  3. Makes sense. So the movement is in worm drive rather than the main bearings?
  4. Hi I'm not sure what to do with the counterweight on an alt az (it's kind of obvious on an EQ) so I screwed the bar into the top mount and put the weight in the middle. It does help - now I can nudge with the clamps unlocked reasonable smoothly and it doesn't drift under the scope's weight. It's very usable like this. I still don't really understand why such a huge mount isn't rock steady, though. There should be zero movement with the clamps locked. Given that a simple cheap camera ball head is completely steady within its weight limit it doesn't say a lot for SW's quality control. The clamps are effectively useless as they don't clamp!
  5. Very nice, looks exactly like my Prinz 660 before I refurbished it. They can easily be upgraded to use standard 1.25" eyepieces by swapping the visual back. Someone should preserve this classic...
  6. Hi Knighty I wish I could be so sanguine as you, but my experience has been very disappointing. Example: observing Jupiter. I line up the planet in my finderscope and lock down the mount. Jupiter in smack in the middle of the eyepiece view. I then adjust the focuser - the resulting movement is enough take the planet entirely out of the field of view of the eyepiece. Or when "nudging" with the clamps unlocked I position the planet right in the centre of the view, then let go of the eyepiece and it jerks to some other position. It can end up anywhere in the field of view, usually right at the edge necessitating further adjustments. Observing then can only get done in brief interludes between adjustments. I do agree that the slack doesn't seem to affect use of the slow motion controls so much, once the scope has moved and settled at the lowest point of the slop. However, the lack of tightness with the clamps unlocked makes it difficult to track by nudging. And when you clamp the locks tight, there really shouldn't be any movement at all from a 3Kg scope on a mount rated for 2x 13kg. My manfrotto camera tripod heads are perfectly rigid when clamped and they are one tenth the weight and dimensions. It's just simple engineering. I remember seeing posts on here that say the skytee can have the play adjusted out by tightening internal bolts and I have seen a step by step guide for the left-right axis but not the up down. Can anyone help out with this?
  7. Hmmm... the only reason I bought mine at all was because of the problems I had with previous mounts and the assurance that the skytee would fit the bill and would be "rock solid"....
  8. Hi I got my Skytee just over a month ago and have had a small problem with movement of its axes. Basically, there is about 1mm of play in both the main axes with everything clamped down as tight as can be. This shows up without a scope mounted: just gripping the "T" and twisting back and forth with my hands reveals a sudden movement. I've sent videos to the supplier and obtained permission to attempt to tighten it up without risk to the warranty. However, how to do it? I've seen talk of grub screws and lock nuts and the like but it would be handy if anyone has a step by step guide, particularly on how to adjust the up/down axis which is the one that is most annoying. Using the right tools is a concern as well, that warranty amnesty might go out the window if I'm belting it with a club hammer :-) This link goes to a video showing the problem: video Any help would be appreciated. Cheers Dave
  9. Had a brief outing in the garden last night before it clouded over. Seems to be quite a lot of movement in both axes of the Skytee. Even with everything clamped up tight, if I grab the eye piece and wiggle it, the objective end wobbles up and down about an inch! Not smooth movement but simple slop. I know the Skytee has a bit of a reputation of being quirky but is this just an adjustment issue or should I be thinking of returning it for replacement?
  10. Just to stay off topic for a bit longer... A black hole event horizon marks the point where gravity is so fierce, light would have to exceed the speed of light in order to achieve the escape velocity necessary to get away from the black hole. As light can't go faster, it is the cause of not being able to see what it is going on in that particular region. The expansion of the universe at a rate greater than the speed of light is another cause of not being able to see what it is going on in a particular region. In both cases the seeing problem is a limitation produced by the light speed barrier but the regions are not the same thing. One is a hidden region because escape velocity is higher than light, the other is a hidden region because it is moving away from us faster than light can come towards us. The qualities of each region are very different, the only commonality is that we can't probe those regions using light. So, no, not being able to probe those regions is frustrating but not evidence that we live in a black hole.
  11. Thanks. That makes sense in that it explains why I prefer the crispness and "look" of views at 100x compared to 150x with scope. I'll try some double stars to see if the higher mag works better.
  12. Yes, a refractor. According to much published wisdom aperture in inches x 50 is the max magnification you should use. My scope ought to be good at 150x by the reckoning but I prefer it at 100x, just looks better, if smaller. I suppose these formulae don't really take into account seeing, transparency, light pollution, thickness of the atmosphere. Perhaps if I were pointing the scope at the zenith from the Atacama desert 150x would be a piece of cake. Perhaps not so easy in south London, especially to the north where on a good night the sky is a yellow/orange glow...
  13. Don't knock £70 telescopes! My 76mm f/16.4 classic refractor cost £27! My 130p reflector with eq2 and tripod cost £45. :-)
  14. When I look at Jupiter through my 76mm f=1250 f/16.5 achro I see a very small circle with a line across the northern hemisphere and a line across the southern hemisphere, no more detail (the moons are pinprick sharp). This is at 100x with a 12.5mm plossl. If i use my xcel LX 7mm for 178x, I see a larger, blurrier, dimmer Jupiter with the same detail. F16 protects me from chromatic aberration unlike your fast scope but not sure that huge magnification with a small aperture is the way to go. 100x should be OK through a 3" refractor but Jupiter won't be huge at 100x, certainly not a centimetre across. A 4mm eyepiece is tricky to see through. My scope was originally fitted with a 0.965" 4mm ortho and I could barely see anything through it!
  15. I have a 130p on an Eq2. With the legs at their shortest, I find it fine when seated. It's nothing like the challenging of keeping a f/16 long tube achromat steady. Is the 150p so much wobblier?
  16. Wider field eyepieces. This was a puzzler for me to start with because of my understanding of optics from a photographic background. Some said a photographic background is a hindrance but it isn't once you understand the somewhat different terminology used in astronomy and the various mechanisms at work. Think of it this way, a telescope tube without an eyepiece is exactly like a camera lens. Light enters the front and is focused at the focal plane. At the focal plane, the image that is formed is not a point but a circle. The shorter the focal length of the objective, the wider the field of view it can see and the lower the magnification. In 35mm camera terms, a 20mm lens is a wide angle lens with a big field of view and everything looks pretty small. A 1000mm lens has a narrow field of view and everything looks big. A telescope is just the same. A 300mm telescope is considered to best suited to wide field, low magnification work. A 1500mm telescope is best suited for moon and planets where a wide field isn't needed. So, without an eyepiece, the field of view and the magnification seen at the focal plane is determined only by the focal length of the objective. This is the "first stage" of the telescope. The "second stage" is the eyepiece. Cameras don't have them! Eyepieces are really just kind of like magnifying glasses that look at the optical circle produced by the objective and and additionally magnify parts of it. Short focal length eyepieces magnify parts of the optical circle more than longer ones but see less of the circle as a result. Longer ones magnify less but can see more of the optical circle so give wider fields of view. What has this got to do with the so called super/extra/ultra wide eyepieces like Naglers and the like? I'll use an imaginary telescope and made up number to illustrate as I don't have real figures to hand: Let's say I have a simple refractor with a 1000mm focal length. Let's say that without an eyepiece it creates an image circle at the focal plane that is 40mm in diameter. If you stick a camera at the prime focus, that is what it would record, a circle 40mm in diameter (let's assume we have a big sensor!). When you use a "standard" eyepiece, you zoom in and see a magnified piece of that 40mm circle. The amount you will see depends on the focal length of the eyepiece. A short FL ep will "zoom" in an magnify the central region and exclude the edges of the circle from view. A longer ep will see more of the circle but everything will be less enlarged. However, short or long focal length, the eps will still see only a part of the circle, say the inner 10mm section for a high magnification ep and the inner 20mm for a low magnification ep. There will still be some parts of the out ring of the circle that is missed by the eyepiece. It is this missing part of the circle that explains where widefield eyepieces do their stuff. So what do exotics like Naglers do? What they do, is at any given focal length they see more of the objective's optical circle than the standard ep. A 10mm Nagler will magnify the same amount as a standard 10mm (eg an ortho or a plossl) but they can see more of the optical circle. Using these exotics you can have increased magnification AND a wider field of view because they can make use of some of the objective's optical circle that is wasted by lesser optics. It's similar to the using the same full frame 35mm lens with a 35mm sensor, a APS-c sensor and a 4/3 sensor. The lens produces the same optical circle with all three camera types but only the full frame sensor can see the full circle. There are limitations, of course: No matter how wide field the eyepiece, it obviously can only go as far the edge of the circle produced by the objective. If you use a exotic eyepiece of low magnification, eventually it will see all of the circle and the limit of eyepiece tricks will have been reached. Typically, other factors come into play, such as vignetting by the eyepiece barrel or the focusing tube itself. The reason 2" eyepieces permit wider fields of view in simply because the bigger eyepiece barrel and focusing tube remove a source of vignetting and thus you can get to see more of the circle produced by the objective. Sorry the above is a bit of a baby talk explanation but I think it covers the essence of how exotic eyepieces do their stuff.
  17. Yes. The aluminium legs are lightweight but weak with a telescoping action secured by a screw clamp plus they attach to the tripod top plate/spider with bolts that go through plastic end pieces. My DIY legs are not height adjustable but single lengths of wood from top to bottom. The side pieces of each leg are glued and screwed into wooden blocks that make up the centre of each leg. This leads to a heavy and stiff set of legs despite the soft wood used. It is difficult to mount a long tube refractor, even if it isn't that heavy. The long tube gives a big lever action that means the slightest vibration causes considerable movement of eyepiece and objective. I started off using a photo tripod and it was wobbly. The porta ii was an improvement, even more so on the wooden legs. It was perfectly steady if you were just looking through but focusing still caused movement. The jiggling vibration took maybe 7 secs to calm down after every touch and made focusing tricky. I was hoping the Skytee would make it rock steady. My brief foray so far suggests it is a massive improvement but it is not rock steady. Touching the eyepiece with a 100x lens in cause noticeable movement in the field of view but only for about a second which is manageable. There are still a few things I have to play around with: adding a spreader to the tripod, adjusting the skytee tension, using the counterweight.
  18. It was just some cheap softwood from home base. The legs were an experiment , just knocked together crudely but they work well enough I'm wondering whether it is worth the effort to redo them with fancy wood.
  19. Good time for a warning actually. If you decide to repaint a tube and use a polishing machine for shining it up make sure, the tube is properly secured. When the spinning polishing pad meets an unsecured metal tube be prepared to watch your precious telescope disappearing rapidly over the horizon...New paint and all...
  20. The tubes rings were a £10 for the pair and I had to drill the shoes but only took a few seconds. Also covers up the dings in the paintwork where I dropped the tube a couple of times :-(
  21. Will do tomorrow. p.s. Is it just me or has the forum styling changed. The text is about half the size it was yesterday (8pt?) . Can't see any settings I might accidentally have changed...
  22. I have my new mount set up. It's a skytee 2 fitted to the tripod top plate from the porta, a piece of steel tube and a long 10mm threaded rod acting as a pillar extension, the aluminium legs of the porta tripod replaced by home made wooden ones, and the standard skytee dovetail clamp replaced with the larger two bolt dovetail clamp from the porta! My telescope is a refurbished and modded Prinz 660 3" long tube refractor with all modern accessories and a new metallic red paint job. It will now be set to be 100% wet and cloudy for the next 3 months.. Dave
  23. Hi I have a classic Prinz 660 3" long tube refractor and I'm considering replacing the (all metal) R&P with a crayford. However, it has a skinny tube c. 76mm diameter and all the after market ones I can see are made for fatter ones. What about this one, any ideas? http://www.365astronomy.com/365Astronomy-2-inch-10-1-Dual-Speed-Crayford-Focuser-for-Refractor-Telescopes.html
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