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martinl

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About martinl

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  1. Although they look manual, Fuji XF lenses are entirely electrically controlled - electric focusing and electric aperture. Unless someone builds an adapter with electronics built in we unfortunately won’t be able to use our Fuji lenses with astro cameras.
  2. Used, you may be able to find a Pentax 28mm XL (55 degrees). They are supposed to be nice, but I haven’t tried one (loved the 7mm XL I had, though). New, I’d be tempted to go with the RKE. They have a cult following for that special “floating” effect and would be fun to try out.
  3. I used this very eyepiece with an f/5 Newtonian and while I could certainly see coma towards the edges it never detracted from the views. I never tried it with a Paracorr, though. People say that once you try a Paracorr you’ll never go back, so I try to avoid trying one.
  4. My reasoning for opting to pull rather than push air was similar to @Space Hopper’s. Pyrex, and especially quartz, mirrors don’t change their figures massively due to thermal expansion. The main goal of mirror cooling is to reduce the boundary layer in front of the mirror and to reduce tube currents. Best is probably to have a fan blow across the mirror face to scrub the boundary layer, but that often involves cutting holes in the tube (been there, done that, didn’t like it). Since my mirror has a slight turned edge I opted to put a baffle a few cm in front of the mirror with a hole a few mm s
  5. Blowing is generally considered more effective for cooling. It also keeps hot air from the observer to be pulled in from the top and interfere with high power views. That said, I’m a contrarian and opted to suck. That works as well, and keeps moist air close to the ground from being pushed into the tube. If you attach the fan or baffle with Velcro you can easily swap it around to see if it makes a difference to your views.
  6. The main issue with undervolting fans is that they may not have enough power to start spinning. Usually you can get them going by giving them a flick with a finger in that case, kind of like starting an old airplane. I’m not sure if larger fans, like this 140mm one, is more likely to suffer this than smaller ones. I would expect so and would probably look at a slightly smaller one.
  7. It should work. No guarantees, of course. Personally I’d skip the speed controller, a 900 RPM fan at 5V should spin slow enough on its own, but it won’t hurt anything.
  8. Another vote for Noctua fans, they are usually very quiet (=smooth), which is what you want for a telescope. I use a 92mm Noctua on my 220mm Newton and it is plenty even at reduced speed. I bet a slower revving 12V Noctua powered directly by a 5V USB supply would work fine. Just attach the red and black cables from the (non-PWM) fan to the plus and ground of the USB cable (USB pin-outs can be found on line). I’ve thought about doing this on my scope and simply power the fan using a small USB power bank attached to the mirror cell. One less cable to trip over. A little air movement goes a
  9. Yes, it has a bit more eye relief. Wether it has enough to use comfortably with glasses I don’t know, it seems to depend on the user. Instead of the 27mm Pan I got the Explore Scientific 28mm that some users claim has a bit more eye relief than the 27mm Pan. In any case it works just fine with my glasses. If I were making the same decision today I would get the APM 30mm UFF over either the 27mm or the 28mm, but Don’s suggestion of the 24mm APM UFF is also interesting if one wants to stay with 1.25” eyepieces.
  10. Yes, absolutely. The only downside of the 24mm Pan is that it is a bit too short on eye relief to use with glasses. If I didn’t wear glasses to observe I would still have mine.
  11. My understanding is that the Schott logo was a time-limited marketing deal between Skywatcher and Schott that has now run out. They still use the same glass (changing it would require major optical redesign), they just don’t advertise it. I agree the green is unsightly. I got a Russian Intes instead - that thing is SUPPOSED to be unsightly, it is part of the charm!
  12. Yes, it is a remarkable eyepiece, no doubt. However, in practice I find I prefer around a 70 degree field of view, lighter weight and a bit longer eye relief and it’s too nice a piece of kit to sit unused so better that someone else enjoys it!
  13. 3M VHB tape is extremely sticky and doesn’t seem to deteriorate over time. I think that would work to attach the finder base where you want it. It also comes off cleanly when no longer required.
  14. Excellent condition with only minor signs of use on the 2" barrel. Glass is perfect. Comes in original box with end caps and paperwork. £580 / €635 Price includes insured and signed-for delivery to the UK / Europe. Bank transfer preferred. For PayPal please add 4% to cover their fees.
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