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Nik271 last won the day on September 22 2021

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  1. https://www.firstlightoptics.com/telescopes-in-stock/stellamira-125mm-ed-doublet-f78-refractor-telescope.html OTA is only 4.7 kgs. I don't know of anything lighter among the 5 inch refractors. But it's obviously long (almost a meter at F7.8)
  2. In case you have been following the news you know that a private US company managed to land near the south pole of the Moon. It turns out that the current Moon libration is very convenient to observe this location (which is perhaps why it was chosen for landing spot). I was looking at the south pole region yesterday and noted that Newton was well illuminated. The landing spot is the crater Malapert A which is just next to Newton A and B. It is not very conspicuous crater being on a hilly region but anyway if you look at that part of the Moon here are two snapshots from online moon maps to help you find it. (South is up). I might try tomorrow at the full moon when there is a forecast for clear skies.
  3. I think a lot of the maths (and physiscs) reporting on Youtube is a bit sensational and I can see why: it's too hard to capture many peoples attention doing elaborate computations with series and integrals, so throw them a crazy looking identity to provoke interest. There are lots of interesting (and rigorous) ways to derive the value of the zeta function at -1 with a bit of analysis. Already Euler had a almost complete argument for the closely related eta function. The maths of the video is rigorous, the presentation is in places not.
  4. I think FLO don't normally check the collimation of doublets, simply because doublets very rarely arrive out of collimation. I am sure if there is any issue with the scope they will take care of it.
  5. I managed to see the ray this evening (18 Feb 2024) at about 18:00 with my 102mm ED F7 refractor, using magnification of x120. There was some passing cloud and in the gaps between the clouds the bright ray on Hesiodus floor was evident framed by dark shadows on both sides. It looked to me like a bright door opening on the crater rim and letting the light in.
  6. 4 inch secondary, as big as my refractor for tonight! I was also looking at the trapezium at about 8pm and got a hint of E at x185. I find F quite hard even in my largest scope a 7 inch mak.
  7. Spaceweather.com says the region 3576 is 720MH which is about 140 square degrees on the Sun or 2100 million km^2. I tried to picture it as a square: sqrt of 21x10^8 is about 46 000km, so this is a square with side four times the diameter of Earth. Big!
  8. I just had a good look at it during a few minutes of sunshine. Seeing is poor, just can do x50 but yes totally worth it. It's also very magnetically active so may send out a big flare towards us.
  9. I don't mind being confused with this crowd ;)
  10. It's also worth pointing out that angular separation you can resolve depends on the magnitudes of the stars. Bright stars are the best, for example Castor AB at 5'' will look 5x18=90'' or 1.5 arcminutes apart in your binoculars, so you should be able to split it with excellent vision. On the other hand a similar double star pair of say 9-th magnitude and separation of 5'' may be not resolvable. This is because human acuity depends on the brightness of the objects since the retina uses different cells for low levels of light.
  11. I was lucky too with the clouds, it was clear for two whole hours, 7pm to 9pm. Had a brief view of a shadow transit of Ganymede. Very distinct dark dot near the south pole. The wind was shaking the tube of my 102ED so x120 was difficult. Transparency was decent, M42 was showing its 'wings'. Had a brief look at Keid 40 Eridani. The B/C pair were easy to spot near the orange primary but I could not separate the white and the red dwarf from each other. Finally I just cruised the open clusters of Auriga and Gemini. A very windy but satisfying grab and go session.
  12. Yesterday I had a brief window of clear sky between 8 and 9pm. The main goal was to try Eta Geminorum (Propus) with my Skymax 127. This is a rather close and unequal pair ( orange mag 3.5 primary and a bluish mag 6.2 secondary), which has become quite a bit easier with time. It was discovered by Burnham in 1881 and at the time he wrote that "it is difficult for telescopes of smaller than 12 inches in aperture". Since then the gap has widened from 1'' to 1.7'' separation and of course telescopes have become better and now it must be within the abilities of a good 4 inch refractor in good seeing. I started with my usual tests for seeing: Theta Aurigae, which was very steady at x120 (12mm EP) and Wasat (Delta Gem) which was also showing clearly. I tried a few more of my favorites: Alnitak, Rigel, even Sigma Cass in the other side of the sky, all looking well. So I was reasonably confident that Eta Gem is also possible. At x120 I can only see the orange primary. With a 9mm (x165) there was a hint of some disturbance in the first diffraction ring. Finally I went all in with 6mm (x250, about the maximum of the scope). The primary Airy pattern was not so clean and steady anymore but in moments of stability I saw a bump on the west side of the diffraction ring. Here is my sketch, the blue was more of a teal colour and more faint, I could not find the right colour on my sketchpad. Afterwards a visit to the nearby M35 was a no brainer, I could just about fit it all in with the 24mm Hyperion at x65. The transparency was briefly excellent, I could spot the nearby NGC 2158 as a dim gray smudge. And then of course since I am in the neighbourhood I visited M1. It was showing very nicely (for my suburban sky), the elongated shape was obvious and I could see a hint of structure inside. Perhaps my eyes were well dark adapted by then, or maybe the approaching low clouds helped to block the light pollution. Anyway, now is the season when Gemini is high in the sky, so give Eta a try if you can! Clear skies and thanks for reading, Nik
  13. I definitely noticed improvement in contrast when I replaced my basic SW mirror diagonal that came with my Skymax with a dielectric. But even then there is a bit of light scatter around Jupiter. I think the mirror surfaces are not as smooth as in premium scopes, which is fair at this price point.
  14. I believe it's planet X OP is talking about. The problem is that the area of sky the models suggest is too big and the chance of occultation of a star is very small. It's better to look for movement but at these magnitudes (mag 20 or more ) you need big telescopes which means small fields of view, expensive telescope time, so the search is still going on.
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