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Andrew_B

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  1. The same eyepieces seem to be sold under the Maxvision brand as well but for whatever reason there don't seem to be any 8.8mm ones available. Must be a popular focal length.
  2. If you're finding it a real chore to set up and break down and it's getting in the way of your observing then it's definitely worth changing for something more convenient that you're more likely to use on a regular basis. There are a lot of smaller options you could get instead but the best choice would depend on what you like to observe and how big a scope setup you would prefer to have. If you like the Moon and planets then something like a Maksutov might suit you perfectly although it's not the best choice if you prefer wide field views of DSOs.
  3. I couldn't tell you about cool down time specifically because I don't have a Dobsonian, but it shouldn't be very long with those outside temperatures. What you can try is have a look through it as soon as you take it out then have another look every 5 or 10 minutes to see how much the view improves and how long it takes until the image quality stays the same. If you can put your scope out for an hour before you want to observe then it should definitely be ready and performing well when you start using it. I've not tried those eyepieces but I do have a Svbony Plössl which I've been impressed by. It gives a lovely bright image, it's sharp across most of the field and very good value for money. I think they're basically the same as the Celestron Omni Plössls but for a much lower price.
  4. Another factor could be whether the scope had cooled down properly. If it went from being indoors and warm to being out in relatively cold night air then it would need time to reach ambient temperature and until that happens you get air currents inside it which disturb the light and reduce image quality significantly. Bigger scopes take longer to cool and tend to be more sensitive to temperature issues from what I understand, especially compared to a small refractor like your Celestron which will be ready to use almost immediately.
  5. Could be that they see a Crayford as being good enough for the smaller and lighter weight scopes that would have a 2" focuser attached. I've got one ordered to put together an FC-76DCU and I wouldn't want to be hanging enormous cameras off it or want a focuser that was very heavy when the scope itself is so light. Prices are getting a bit silly though, and even the low end models are an expensive upgrade.
  6. The Star Adventurer is great for Milky Way photography. It's relatively easy to set up and with a wide angle lens you don't have to worry so much about small tracking or alignment errors. You can then bump up the exposure time for each image and take more in total to produce your final stack. Here's a shot I did with a Samyang 12mm consisting of 100 30s exposures. It was taken in the North Wales countryside so probably Bortle 3 but it was in August so the sky wasn't getting properly dark anyway. It's not amazing because I'm just a beginner but it gives an idea of what that combo can do. The blur at the bottom of the image is a foreground tree.
  7. What are the pros and cons of R&P versus Crayford? I've got a 2" Crayford FTF on the way but I didn't see a R&P option in that size - not that it matters and I'm sure either would be more than good enough for my needs.
  8. I second the suggestion of a modded mirrorless camera. You can pick them up secondhand for very little money compared to what a dedicated astro camera would cost. I got a full spectrum converted 24MP Fuji for just £180 and the performance is very respectable even when shooting narrowband.
  9. Tak doublets have a pretty devoted following and a 5" fluorite doublet would probably sell in reasonable numbers, not least because just about everything else available at the high end in that aperture range are triplets, quadruplets, and whatever else aimed at the imager. Astrophotography drives most of the market but there's still a decent number of visual observers or people who do both and enjoy the convenience of a fast-cooling and lightweight scope. I've just had a look at an old Tak advert from 1990 and the FC-125S was selling for £5,400 back then which is the equivalent of over £12,500 today. Even high end astro gear is far cheaper than it used to be.
  10. I've used both vaseline and candle wax to grease threads and they worked well enough. The reason I chose them was because they were immediately available and I know what's in them so there shouldn't be any nasty surprises and they ought to be relatively easy to remove if they end up in the wrong place. Stuff like molybdenum disulphide grease or graphite grease might do the job well but if they get on your hands and then on your clothes or furniture then it's going to make a mess.
  11. If a scope gets you out observing and you enjoy it then it doesn't matter what it cost or how close it gets to optical perfection. I suspect that people who spend their time worrying about what they can't see because of the limitations of their scope will never be satisfied with what they can see.
  12. Using a wide air space can give better correction with a given pair of elements so that might be an option, but it would mean a larger and heavier scope that might be a bit more prone to losing collimation. That said, the old FS-series were a lot bigger and heavier than their equivalent modern FC-series scopes so perhaps a lightweight but highly corrected 125mm doublet could be a viable option.
  13. It's okay I could appreciate the humour. Like you say there's so many factors involved like presence and size of an obstruction, cool down time, convenience of different designs, local seeing, etc, etc that what counts as a good scope will vary enormously from person to person. Sometimes people get a bit too focused on judging things in terms of easy to compare numbers rather than more qualitative factors and want a single easy answer about what's "best" that they can apply universally.
  14. I think I must have read that info somewhere on telescope-optics.net and this page has the formula for the minimum focal ratio at which a spherical mirror gives acceptable performance as the cube root of 90.15 multiplied by the diameter in inches. For a 6" mirror this would be F8.15 so a spherical F8 optic should be close enough to be good but I'd imagine they'd parabolise it anyway.
  15. I bet that's a really impressive planetary scope and a good 6" F8 mirror is easy to make and apparently should give decent performance even if it's left with a spherical figure. Mind you, you couldn't pay me to own a Newtonian, they're just not my cup of tea.
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