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Piero

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Everything posted by Piero

  1. My docter was sold second hand at a honest price at the time, but the same price became a crazy bargain some years later following the new sky reaching cost of this eyepiece. My glatter collimation was bought new when Howie Glatter was still alive and it was way more affordable than the current cost (despite the design being the same!). Years ago I bought a s/h 30mm ES 82 deg and I consider it a bargain for what it offered.
  2. Mm.. - my 12" f6 Lukehurst dobson (bought new) was very disappointing. After substantial redesign I am very pleased with it (it is a favourite one), but oh boys how much effort and time spent on it.. - a Lunt 50mm bought used. Nothing wrong with the telescope, but I simply did not get on with it and didn't find the views particularly impressive given the small aperture. It was sold almost immediately without regret. - Vixen LVW 42mm. Bought new and was not particularly impressed by the views. Sold. Same for a Baader BCO 10mm and Vixen NLV 30mm. - TV plossl 20mm (lenses assembled incorrectly, still have it) and nagler zoom 3-6mm (too much play in the central column, returned). I've also had some excellent gear on my hands though. Just thinking about my current telescopes, Docter, Zeiss Zoom, VIP Barlow, Vixen SLV 5mm, Vixen HR 2.4mm, etc.
  3. @Don Pensack mentioned that If it is bi-concave, it could be in either direction, though only one direction would be correct. I have no idea whether the VIP element cell accepts only one direction or both. It would be good to test your current assembly (e.g. in day and night time) to see whether the barlow works as expected.
  4. In the village where I live the LED streetlights are much better than the old non-LED ones for the same reason you stated. Here the LED tend to be warm (a bit orange) but the light is considerably dimmer, much better directed to the street and better shielded. BTW, many of the new street lights here seem to be like number [3] shown in a previous post.
  5. My favourites based on what I tried: - docter - Zeiss zoom d-vario 20-75x (at f6, not at f4) - Vixen HR 2.4mm (also had 3.4mm and 2.0mm) - Vixen SLV 5mm (also had 9mm) - Delos 6 (also have/had 12mm, 8mm, 4.5mm) - N22T4 - N9T6 (also have /had 2x 13mm and 2x 7mm) - 24 Pan (also had 35mm) - 7mm APM XWA (also have/had 20mm branded Lunt, 9mm and 4.77mm) - 30mm APM UFF I tried many others of course, but these are/were those that I would call the best ones I tried.
  6. I think you meant "D". I never tried a Pentax XW, but following your argument (some of?) these should reach focus at around "A" (3 x 0.1" ~ 8mm) in the PC2.
  7. At cellular level, you need to reduce mTORC1 activity as that protein complex activates S6K which triggers a negative feedback loop to IRS1, the insulin receptor substrate 1. In T2 diabetes, mTORC1 is hyperactive, causing a persistent inhibition (and degradation) of IRS1, leading to insulin resistance. Metformin acts by increasing AMPK activity which indirectly inhibits mTORC1. Both calorie restriction and physical activity increase AMPK and decrease mTORC1 activities. Therefore, they both make the cell sensitive to insulin again. There are other cellular signalling pathways involved, but this is a critical one. I would certainly cut off red meat (and calories) and do regular exercise. -- I tried to find out a diagram. This shows far more than what is necessary here, but the point is there (discard the NFkB pathway to the left and GLUT4 to the right). At the bottom, the diagram says IRS serine phosphorylation by S6K. That phosphorylation leads to the degradation of the substrate. A lack of substrate in the cell makes the cell insensitive to insulin (coming from outside the cell).
  8. As far as I can tell, mine is eyepiece = ).( = telescope. ")" , facing the eyepiece, seems more concave than "(" , facing the telescope.
  9. I just checked mine and the lens facing the eyepiece seems more concave than the one facing the telescope as Don suggested. I had to check this several times as it is not obvious. Both lenses are concave. I have never dismantled the element of mine (and never will!), but I would imagine that some retaining rings are in place in the cell so that the combinations for assembly the lenses should be very few if not just one. Why don't you contact Baader to confirm the exact order?
  10. I use my Tak FC100-FT on an AOK AYO2 on a Berlebach UNI 19 with double clamps. It is very stable even with the central column raised up.
  11. Looks like we will soon move into another hobby: "visual satellonomy"! How is tracking going to work though?!
  12. In that eventuality satellites will also be long gone, so we, well, our future generations, will experience really dark skies! To remain with Rutger Hauer, it does not seem to me that the fellas in Salute of the Jugger (1989) were much interested in visual astronomy! 😂
  13. I assume you did not take apart the VIP lens element from its cell, right? 🫣
  14. Hi, The orientation of the VIP element cell is "up" (towards the eyepiece) where those two opposite circles are. See my first image. I would imagine you played with them to take the cell out from the 1.25" nosepiece. Louis' diagram above ( https://stargazerslounge.com/topic/413443-need-help-to-reassemble-baader-vip-barlow/?do=findComment&comment=4411253 ) is very clear. Also, in that diagram, #29 is a ring which I did not include in my post above. That ring allows one to screw a 2" filter right at the bottom of the 2"-to-1.25" reducer. It works as 2" to T2 adapter.
  15. I think the future of visual astronomy will be lunar and bright planets observing, due to the increasing light pollution and number of satellites. As a society in general, I think we are heading to a "blade runner" landscape without replicants or flying cars (at least in the short / medium term). As we approach that, I also think that there is a good chance that we face some very brutal war setting us back to another middle age. It seems a cyclic pattern in history.. On a positive side, middle ages also means dark skies, although I suspect that visual astronomy won't be a priority then..
  16. I took a couple of pictures of my VIP Barlow. Mine was heavily modified but the lens direction is the same of course. Lens facing the eyepiece: Lens facing the focuser: In its original configuration the VIP Barlow is as follows: - 1.25" to 2" reducer adapter - 2x 15mm T2 spacers - VIP element screwed onto a 1.25" nosepiece - the 1.25" nosepiece It's a great barlow. One of the very best.
  17. @The60mmKid That's a truly lovely scope!
  18. My almost 10 years old TV60 with 24 Pan:
  19. It is not just "newtonians and correct springs". You also need to have good secondary support (spider and holder), focuser (e.g. the bearings support the drawtube differently at different angles) and primary mirror lateral support. Then, if the telescope is a truss one, it also depends on pole length / diameters and pole attachments. With a laser collimator it is quite easy to see whether collimation changes at different levels of altitude.
  20. Only if you have excellent mechanics. I would suggest to collimate at 60 degree. If you are doing some "serious" planetary observation, you might want to collimate at an angle closer to the planet altitude. -- EDIT: Reason for the 60 degrees The primary mirror is supported at the back and laterally. When the telescope points to the zenith, it is 100% supported at the back. When it points to the horizon, it is 100 % supported laterally. Assuming the angle x is the telescope altitude (0=pointing at the horizon, 1/2 pi=90 degree or pointing at the zenith), you could model the back and lateral supports with the functions sine and cosine, respectively (see plot below). The two forces intersect at 1/4 pi, which is 45 degrees. Therefore, one could simply collimate at 45 degrees, as a balance point. Practically, it is pointless to observe at the horizon and just above it as the atmosphere is thicker and the views are more affected by the seeing. The vast majority of observations is done between 30 and 90 degrees, therefore, my suggestion to collimate at 60 degrees.
  21. For an objective way to assess the effects of various degrees of miscollimation, I would suggest to get a copy of Suiter's book (https://www.firstlightoptics.com/books/star-testing-astronomical-telescopes-a-manual-for-optical-evaluation-and-adjustment-second-edition-book.html ). This can also be found in the second hand market. A mild miscollimation in the primary mirror introduces some degree of coma. A severe miscollimation can also introduce astigmatism. If the optics are diffraction limited (1/4 lambda - which is just to say "commercially acceptable"), you want to collimate your telescope better than that to avoid introducing a larger error. In other words, you don't want that your collimation worsens the views delivered by your optics. To do that you need good collimation tools (=robust and collimated themselves) and you need to use them properly. These tools have tolerances, so the key point is to do the best job as possible so that your optics are collimated up to the tolerance of your tool. Assuming that you have collimated your Newtonian as good as possible with your trusted tool, what is enough? Well, if you draw something technically, what scale of ruler is good enough? It depends on the image size you observe. The higher the magnification is, the larger the diffraction disc becomes, the more you are challenging your optics, the more you can see imperfections. Take a 10" dobson. Below 150x possibly any tool can correct well enough. You likely need a good tool for higher magnifications tough. Above possibly 400x, you might even want to use an autocollimator. Of course you can just use a cheap collimation tool for any magnification you want to reach, but that tool will not offer a reading which is precise enough and these imperfections can be detected at high magnifications. Regarding "obsessing about collimation", well.. this is a generic comment. It really depends case by case. Personally, I find that if the optics are not close to ambient temperature, the introduced error is visibly larger than a slight miscollimation. If the mirrors are not supported properly, the introduced error is even larger. Reading comments by members it seems to me that a large number of people simply accepts the mirror supports as they are, meaning without questioning whether these work well or not. In addition to this, it seems to me that very few people use a fan to cool down their optics, justifying this with terms like (it does not have any effect, again, maybe the questions should be - is this fan working okay? Was it installed properly?). Often, the most basic and cheapest collimation tools are also employed (oddly, as cases of Televue and other high end eyepieces are often used). Finally, the statement often reported is: 150-250x is the highest magnification due to UK seeing (the only culprit of the equation!). In agreement with Suiter, collimation is a factor in the stack. There are many other factors to take into account, some of which are out of control, whereas other can be controlled. Unfortunately what people tend to get really fussy about are eyepieces, whereas the rest seems mostly neglected in my opinion. Eyepieces are just another step in the stack. The best eyepieces deliver miserably if other steps in that stack do not perform satisfactory (and yes, I write this by experience). I hope this helps a bit.
  22. Mm.. I think DIY makes sense if you want a medium/large dobson (e.g. > 12") or you want a custom solution. It's an amazing experience though. I'd recommend a copy of "the Dobsonian telescope" by Kriege. "The portable Newtonian telescope" by Highe is also excellent but in my opinion it's more advanced and this can put one off. If you are interested, here's the album showing the building of my 16" f4 dobson: https://photos.app.goo.gl/DAZ8CqeRtJGe83jF8 .
  23. Well, both my 12" and 16" home made dobsons have the focuser to the West when the telescope points to the South (north emisphere). The primary reason is pulling instead of pushing when tracking manually. The second reason is that I slightly prefer this configuration. My dominant eye is left and it is slightly closer to the telescope when aiming with the Rigel or telrad. My 8" f6 solid tube dobson has the focuser installed to the left like most of commercial dobsons. It's usable just fine although I prefer the other way around. 12" and 16" dobs: 8" f6 dob (focuser and eyepiece sold years ago..)
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