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digital_davem

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Everything posted by digital_davem

  1. Hi Welcome I have a 660, recently acquired as well. I'm fitting it out with more modern parts - I have added a 1.25" eyepiece holder so I can use it with contemporary eyepieces. My coffin box was missing the tripod and most parts of the mount so I've added tube rings and an arc-swiss bar so I can use it on my camera tripod. Casting envious eyes on proper mounts though. One for the future. My next step is some kind of finder as that is missing from my kit,too.I've ordered a Vixen/synta finder mount and I'm hoping that little screw that holds the stock mount on will be enough - don't fancy drilling the tube. I happen to have the sun filter. Nasty, dangerous little thing. I was considering destroying it as a favour to someone's eyesight but if you are a completist and promise faithfully it will never be used, I can send it to you. Cheers Dave
  2. How big is the Rigel - it looks awkward in the pic. My scope is the classic long refractor but the tube is a mere 76mm across. Will it fit ok?
  3. http://www.ebay.co.uk/itm/121788143581?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT Cheers Dave
  4. I've not actually been able to see anything through the 6mm or 4mm! The H20 works but is dim and has a very wobbly looking outer image circle. I suspect vignetting. If I screw the little brass lens on the end of the eyepiece (I assume this is the Barlow out of its tube) it works much better with a crisp outer image circle. The two Antares plossls I got in 1.25" size seem vastly superior. I'm considering throwing away the sun filter as a threat to live and limb.
  5. The £27 got me the box, the OTA, dew shield, visual back, prism diagonal, terrestrial prism corrector, 3 eyepieces, the collection of tubes I now believe to be a Barlow, a mystery naked cemented doublet lens about a centimetre across in a plastic tub, two eyepiece filters, a heavy weight, an arm to put the heavy weight on, two flexible cables with knobs on, a collar and bar for the sun thing, the sun thing plate, some wingnuts and misc bist of foam in plastic bags. Missing was the tripod and most of mount.
  6. It looks good and for such a great lens too. Any idea how much and where from? I bet it will be a lot more than my duct tape but functional version
  7. Don't worry, I'm definitely working on the cheap. My 660 outfit cost £27 and that has set the tone for what seems a sensible price for accessories! Talking of cheap, I've managed to figure out a way to mount my OTA on the stronger pan and tilt head I have by removing the arca swiss clamp from the ball head and fixing a manfrotto QR plate under it where the ball head normally fits then attaching the whole thing to the arca swiss bar I have fixed to my rings. It's all lighter duty than the usual dovetail stuff but along the same lines. The pan and tilt is a lot easier to use than a ball head. There is still a bit of flex in the tripod. I haven't yet worked out whether it is it the centre column or the legs. There is a video mod on youtube about how you can do without the centre column for a more rigid mounting. I might try that. It also occurs to me that if a EQ mount is just a pan and tilt with a built in offset from the horizon, would a 3 way pan and tilt not make a cheap EQ? Just set the offset to match the Earth's inclination, then it should track. Or am I thinking my geometry all wrong? I was out last night with my camera rather than telescope. Using a 300mm lens, 2x teleconverter and facturing in the 2x crop factor of my m4/3 sensor, I got the equivalent of 12x which was just right for the Pleides. I found that anything slower than about 1/10th sec was showing some double imaging. Don't know if that is the tripod wobbling - does the earth spin that fast? And boy, are the unprocessed results noisy! I do quite a bit of long exposure photography using 10 stop ND filters so I'm used to 5 minute exposures but that are always at base ISO and of something more substantial than dots of light. I can't see myself being anything other than a dabbler at astro photography, that seems a recipe for poverty...
  8. What have you upgraded to? Not that I want to seem as if I'm copying everything you do (although I have been looking at the skytee2 ;-) ) - especially as I haven't even looked through it properly yet.
  9. Just a bit of fun and satisfying some curiosity... Looking at entry level refractors like the SW ST80, many of them seem to be relatively short focal length. Which makes me wonder why a telephoto lens can't make a good telescope. Even a fixed focal length lene will have 4 or 5 elements and ought to be well corrected. So, I had a look through my gear cupboard.... First up, an old M42 Chinon 200mm f3.5. I cobbled together an optical back from old tubes and eyepiece holder and lots of duct tape. It works! With a 25mm EP I have a 50mm f/3.5 200mm refractor with 8x magnification or 16x with a 12.5mm EP. Next up, something more ambitious: Sigma 100-300 F4 constant aperture zoom. The 100-300 is a big, heavy lens with it's own tripod collar built in so it's almost a telescope in waiting. It has a 75mm front element. I added a 2x teleconverter to turn it into a 3"/75mm 600mm f/8 APO. With my eyepieces this provides 24x or 48x. So, question is, how come a dedicated telescope with a humble 2 element objective is better than a multi-element APO arrangement camera lens capable of covering the full 35mm frame to very high quality. Optically, what stops this being an effective alternative to traditional refractors? Like I said, just a bit of fun...
  10. Hi I was re-fitting the new rings for my classic Prinz 660 today (which required removing the focuser to get them on and off) and I happened to shine a torch down the tube out of curiosity. There are 4 baffles of various sizes that I could see but everything inside looks like shiny metal (it might possible have had some paint once, there is evidence of what looks likes bits of paint spray - or it might just be dirt). Does this au naturel metal finish cause a problem of reflections, or do the baffles prevent that? I've read about people matte black painting their OTAs and/or flocking. Would there be any value in me investigating these options for a 3" refractor? Cheers Dave
  11. It looks very smart and hunky in that pic. Another question - how to mounts attach to the tripod or pillar - is it a standard fitting like camera mounts or are they all different?
  12. The first set back I purchased an 0.956 to 1.25" adaptor plus a 1.25" mirror diagonal. And I've hit focusing trouble. I can focus on terrestrial targets but the stars are great big blurry circles. The problem seems to be that I can't rack the focuser in enough for infinty focus. I suspect the combination of the adaptor and the new diagonal is the problem. With my old 0.956 diagonal + 1.25 adaptor there is no problem. My guess is that my mirror diagonal as a different path length to the old diagonal which uses a single prism. Do prisms lengthen the focal length so the eyepiece needs to be further away? If this is the case I seem to have a few options beyond using the old parts: - get a 1.25 prism diagonal - get a hybrid diagional and dump the adaptor - dump the adaptor and use my mirror diagonal by replacing the original 0.956 eyepiece holder (is this called the visual back) with a new one that accepts 1.25 eyepieces I'm trying to do this with zero expenditure or as near as zero as possible and I favour the third option as it seems the tidiest. But are such eyepiece holders available? The focusing tube has a female thread on the inside but I don't know what type it is. I've measure the (quite worn and loose) male thread on the original eyepiece holder and if I'm measuring it right it seems to be around 35.4 to 35.6mm. I see that there is a fitting called the "small vixen" that used to be used on some Japanese scopes and you can get an adaptor that allows the use of 1.25 eyepieces. But the specs for this say it has a 36.4mm thread. Is it likely that mine is this but just worn down? It is a very loose and uncertain fit. I've attached pic of the original. Thanks and cheers Dave
  13. That mount looks like any other to my untutored eye (i.e. someone who has never seen an EQ mount in the flesh). What are the features that mark it out as classic? It is significantly different from modern mounts? ps That's a neat setup you have there! Is that a converted garden shed? How does the roof work?
  14. I've been trying to find the specs and for the SW EQ5 deluxe there is nothing at rother valley or First Light that mentions weight capacity. There was nothing at 5 other shops I tried either, just the same old vague marketing blather. Eventually, I found a shop with some actual specs - it claims to carry 9kg. My scope weighs 3.2 Kg without eyepieces etc but I'm worried about the torque from the long tube - and also have no idea how to mount the telescope. Pretty sure my arca swiss bar won't fit!
  15. Yes, I noticed that when I first tried mounting the scope on my carbon fibre tripod. The head was visibly flexing with the slightest touch. Swapped to the aluminium as the legs mounting plate is a much stronger casting.
  16. Looked up skytee-2. It looks very impressive but I think the mount, tripod and accessories will cost about 15x what I paid for the telescope - which might be a bit of a gamble!
  17. At the moment I have my OTA fitted with two knock-off Canon 80-200mm F2.8 lens tripod collars (the only things I've found that are the right size and readily available). These have tripod mount feet and are screwed to a 200mm arca-swiss plate. I'm using manfrotto o55c camera tripod legs and a manfrotto 486RC ballhead on which I have replaced the stock quick release clamp with an arca-swiss style screw clamp vice. Not ideal, it's just barely stable as long as you don't touch it but moving it while observing is out of the question. The long tube applies a lot of torque if you touch the eyepiece. Is an Eq5 a really big heavy thing (my 486RC ballhead wll fit in a pocket)? I do have another camera tripod head, a manfrotto pan and tilt head which is bigger and stronger than the ballhead but it isn't arcaswiss compatible which means I'd have to find a way to bolt a QR plate to the bottom of the arca swiss bar.
  18. I kind of figured it would be something like this - what's missing is the detail. Are these EQ numbers some kind of standard like shoe sizes, car wheel sizes, paper sizes or are they some kind of loose-can-mean-anything description? I would have expected that with a scientific discipline like astronomy there would be standards and you would simply measure and weigh the scope and there would be a chart somewhere that told you what size mount you needed. I'm beginning to suspect it ain't so...
  19. Good question! I don't know. In my 1976 edition of the Observers book of Astronomy, Patrick Moore says I do...
  20. I'm looking for something that will provide a solid dependable mount for my classic 3" refractor with its 41/2 foot long tube. Eq1, Eq2, Eqn what does it all mean in reality? Cheers Dave
  21. Hmmm... I suppose that might work but I don't really fancy drilling it. I wonder whether there is something that can mount into a standard 1/4" whitworth tripod socket - I could get a third tube ring with a tripod foot.
  22. My recently acquired classic prinz 660 seems to have lost its finder at some point. Does anyone no whether the finder shoe is a propriatary or standard fit? It is kind of like a giant oversized flash hot shoe but tapered rather than straight. I need to get some kind of finder but I have no idea what the fitting is called or whether there is anything available for it these days. Thanks Regards Dave
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