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martinl

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Everything posted by martinl

  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.
  15. Living at 60 degrees north Saturn transits the meridian at only 9 degrees this year but the seeing was exceptionally steady tonight, with the Cassini division clearly visible in my 150mm Mak at 150x despite the low altitude. The Mak, of course, struggles with low powers so I was relegated to using my humble APM 50mm RACI finder (which didn’t come with a Strehl report (!), perhaps I’ll run it through WinRoddier at some point for fun). 12mm Delos / 17.3x: Saturn clearly had ears, but no separation between the planet and the rings was visible at any time. 8mm Delos / 25.9x: The rings were
  16. Interesting. Galileo’s telescope, which he used to first observe that there was something strange going on with Saturn, supposedly gave around 20x magnification. I can see the ears with my 20x60 binoculars, but I haven’t tried low powers with my refractor. I’ll try my TV85+28mm=21.4x next time I have the chance!
  17. I wouldn’t worry too much about your potential future needs for two reasons: 1. Your EP preferences (AFOV, eye relief etc) will evolve over time, so anything you buy today may not be what you want in the future anyway. 2. Your Mak, being a “slow” scope, is very easy on EPs and there are a great number of cheap EPs on the market that are very good with slower scopes, the BST Starguiders for example. You could buy a whole set that works very well with your current scope for the cost of one single high-end EP.
  18. I just bought a pair of NF Chilkats. They seem fairly good (only had one outing so far) but they still leak heat through the soles. 3h at -8C and my feet were not too happy, despite oversized boots and extra wool socks. Does anyone have an opinion on different types of insoles? Do the aluminised ones work? Felt? Sheepskin? I’d hate to go through the hassle of electrically heated insoles.
  19. Jesus! You only average 2.4 hours of observing per day? That’s it. I’m moving to Toronto!
  20. CONTRASTING is the word you’re looking for. Looks great. Excellent idea!
  21. @jock1958 Interesting. What do you use the flat for, and where did you get the angled piece?
  22. Ask, and ye shall receive: https://www.berlebach.de/?bereich=details&id=598&sprache=english
  23. It should work. A few comments: 1. If your 18650s have built-in protection circuits they are slightly longer than standard 18650s. My protected cells wouldn’t fit in a similar case. 2. That BMS is for LiPos. You’ll want to double check that the over/under voltages are ok for Li-ion. 3. Charge all cells fully before before installing them to make sure they are balanced and give the BMS an easier job.
  24. Hmm... (Slowly removes finger from the “In Cart” button on the Telescope-Express Ercole page)
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