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Piero

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Everything posted by Piero

  1. Regarding your question about collimators, I use the 2" Glatter laser with 1mm aperture stop and 2" Glatter tuBlug for adjusting the focuser and primary axial alignments. I prefer the Catseye Telecat XL for centering the secondary mirror under the focuser, a once in a while adjustment.
  2. Hi, There are many factors determining the balancing of a dobson, not just short f-ratio or heavy mirror. The size of the altitude bearings as well as the number and how teflon squares are installed, are also very important. Being a truss design, the telescope is very portable at both F4 and F5. Between the two I would opt for an F5 (you did not mention, but you will also need an adjustable chair). 12" F4 is as tall as a 8" F6 or 10" F5. For that size, a solid tube offers more advantages in my opinion. F4 dobsons are nice but many factors become critical aside from eyepiece quality
  3. Here are some shots taken during a nice session observing the Moon. And here a video: VID_20190909_222618~2.mp4
  4. It depends. The angular coma free region is constant across magnification, although coma is often perceived at low power rather than high power. I believe the reason is due to how coma is revealed, as the star is a point source - brightness increases with mag -, whereas the comatic blur is more like an extended object - brightness decreases after a certain mag -. For bright stars and planets, coma is well noticeable at high power, unfortunately.
  5. I agree with Paz. LP is a major filter unfortunately. My TV60 on the dolomites (21.2) showed much more detail on anything but planetary targets than my Skywatcher 8" F6 dobsonian used in a location affected by severe light pollution (18.4).
  6. If it's not offset, the downside could be an unbalanced field illumination. This is generally more critical in imaging than visual. There's nothing perfect in this job (collimation), just a requirement to remain within tolerances.
  7. I can move the sec mirror closer to the primary mirror along the axis, but cannot slide the secondary mirror along the 45 degrees axis. I would not do the latter anyway.
  8. This is what I've done. It helps with balance too
  9. Congratulations! Need to try to spot Triton.
  10. I found out the "correct" size of my secondary mirror! Minor axis: 57.15mm Major axis: 85.725mm It was supposed to be 62mm minor axis. Anyway, with the new correct measure, the central obstruction is 18.73% . On a positive note, contrast should be better. Using the laser I could also notice that the secondary is currently not offset along the mirror axis and that it's about 2mm titled. Not a big deal as my larger ep field stop is 38mm, but I will adjust it when back home.
  11. Thank you gentlemen! I will take advantage of this clear evening as rain is expected tomorrow! Wish you clear skies in the UK!
  12. I'm currently on my annual leave in Italy and the sky has been clear all day with no air turbulence. The telescope is out - of course - and I managed a session before dinner. I thought about sharing some photos taken with my phone and a couple of sketches.
  13. The square attachment is for the secondary mirror alignment as shown in Jason D's posts on CN.
  14. My 2 Glatter's laser collimators arrived with a 1mm aperture stop which reduces the laser beam and also makes concentric rings. It's a great tool. For more details about collimation with a RC, I would ask @FLO.
  15. Thank you! That certainly helps. It would be very difficult to move the telescope around otherwise!
  16. Lovely report, Iain! I enjoyed reading it. Thank you for sharing.
  17. Thank you, John. I'm still in the process of getting acquainted with this telescope. Due to many new components, there's a bit of learning curve, but it's getting there, I feel. I have just come inside from a session with this telescope. Just a few open clusters in Lacerta and the blue snowball nebula in Andromeda.
  18. Other few things for my dobson: book by Vic Menard, Catseye template, 1/4" white triangle, and Catseye Telecat XL.
  19. Replaced the black (why black?!) doughnut with a 1/4" Catseye white triangle. It is considerably easier to see and the triangle silhouette allows me to align the edges to the primary mirror collimation bolts. After carefully removing the central spot as described on the Catseye website I attached the triangle using their template (image 1 and 2). Then I collimated the focuser (image 3) and the primary mirror axes. The latter using the tuBlug (image 4). Alternatively, both the axial alignments can also be checked on the 1mm aperture stop attachment (image 5 and 6). Fina
  20. As you like the "low power + zoom" combo (me too by the way !) and want a wider FOV, what about improving this? Here could be a long term solution: invest in a good 2" diagonal (this allows 2" filters) current 32mm plossl => 35mm TV Panoptic or 30mm APM UFF current Baader zoom => Leica ASPH zoom Baader VIP barlow to combine with the Leica zoom (you need an extra £30 Baader adapter to prevent the VIP from touching the mirror diagonal) You might need some altitude counterweight, but this can easily (and cheaply) be solved with a wrist counterweight attach
  21. In my opinion if you want to improve the views of DSOs, you should consider a telescope of larger aperture. Something like a 10in dobson will also complement your refractor. Secondly, I would try to understand what you don't like about the views you get with your current plossl and zoom, and if you can or not live with it. Said this, you mentioned "transmission". The highest transmission is on-axis. The eyepieces with the highest transmission I found are Vixen HR, Docter UWA, and Zeiss zoom diascope 20-75x, particularly when combined with Baader VIP Barlow. None of the above i
  22. That 1.25" spacer screw on the BCO barrel? If so, what is the distance from the top surface of the 2"-to-1.25" adapter to the BCO barrel included? That's your X (in millimetres).
  23. The formula for the VIP Barlow 1+(64/64) is for the VIP as it is sold with the 2 X 15mm spacers and bottom ring.
  24. You are not using the two 15mm spacers. So you need to subtract 30mm. Minus another 5mm due to the lack of bottom ring.
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