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About lenscap

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    Star Forming

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  1. Hi SiD, When you point the scope at 1st star of a 2 star alignment and press "Align", the software notes the RA & Dec co-ords of that star. When you select the 2nd star the mount calculates the difference in RA & Dec co-ords between the 2 stars & drives the RA & Dec axes by the required amounts. Since Polaris is very close to the North Celestial Pole you could make large errors in RA and the scope might still be pointing close enough to the Pole Star for you to accept the alignment, but the mount would be using the wrong RA co-ord and subsequent slews would be innaccurate.
  2. Vlaiv, I have skimmed through the "Magnification" section of this source and it seems that the 2D figure is reached by assuming 4 arc min as a resolution limit for the eye, not the 1 arc min in your first analysis, which accounts for the difference between the 2D & D/2 results. So I suppose the question is, what is a practical, realistic resolution limit for a typical, dark-adapted eye observing a double star through an appropriate telescope exit pupil.
  3. Fantastic! Your processing has revealed how stars warp the fabric of Spacetime; a Nobel Prize awaits
  4. Looking through my notes, I see that I have been clouded out for the last 3 weeks, & only had two clear nights in the preceding month! So when the skies cleared on Monday afternoon I couldn't get the 200p out fast enough, especially as it would be my first chance this year to observe in Orion, albeit with a fullish Moon. Rigel is not a tight double ( 9.4") but I had read that the brightness difference ( over 6 magnitudes ), makes it difficult in an amateur scope. But inspired by a heads-up from @orion25 which suggests it as a good , but much easier, practice target for those hoping to spot the elusive Sirius B, I decided to have a go. Having read that high power is best for such contrasting doubles I popped in the recently acquired 4mm TMB planetary, ( x250 ) and there was Rigel B to the SW of the primary, and so faint beside the fireball that it looked more like a giant planet than a dwarf star. Now that I knew exactly where to look I tried lower powers & could still split the pair with a 10mm generic Plossl ( x100 ). I spent an hour enjoying some new & some familiar doubles & multiples in the constellation before pointing the scope at Sirius. The Dog Star was fairly steady, not the usual flashing disco ball, indicating above average seeing. There was some lateral colour, presumably, since I was using a Newt, an atmospheric affect due to the low ( 17 deg ) altitude. I tried various EP's but no trace of Sirius B. Still it is a difficult target & I didn't expect to crack it at the first attempt, & Sirius will be climbing slightly higher over the next few weeks. ( I realised later that one of the diffraction spikes may have been occupying the pup's expected position; must remember to rotate the tube in the rings next time. ) Great to spend an enjoyable couple of hours under the stars again !
  5. Thanks Reggie. There's a lot of good info in the linked article; well worth a read. Now I just have to wait for some excellent seeing. Since I live in the UK that may take a while.
  6. Hi Nora, welcome to SGL. This manual includes instructions for a very similar telescope & mount. https://inter-static.skywatcher.com/upfiles/en_download_caty01316546551.pdf Hope this helps. Edit; this one is specific to yourtype of scope. SW114-500Manual.pdf
  7. This Sky@Night magazine article has plenty of detail; https://www.skyatnightmagazine.com/advice/how-to-build-a-dobsonian-mount/
  8. Hi Harry, If you are into DIY you could build a full Goto system for that mount using; https://onstep.groups.io/g/main/wiki/home or, https://astroeq.co.uk/tutorials.php I built an Onstep Goto system for an old EQ3-2 for less than £100 including motors & WiFi, so I can control it with SkySafari from my phone. There is a lot to get your head round but once you decide exactly what features you want, the actual build is not that difficult & the result can be as good or even better than a commercial system.
  9. Brilliant. I want one! I would fit out the interior as the flight deck of the Millenium Falcon & charge visiting Star Wars fans to fly themselves around the Universe on Stellarium. I would make a fortune!
  10. Once you know the Right Ascension (RA) of an object just remember that, because of the way RA is defined, a target with a RA of 0 hours will reach its highest point ( culminate) at your local midnight (standard time, not daylight saving) at the autumn equinox, 23rd Sept, and other objects will do so 1 month later for each 2 hours of RA. (Or, more accurately, 15.2 days per hour of RA) So Betelgeuse, RA 5h55m will be at its highest on 22nd December.
  11. SW don't show specs for the fixed-tube 12" Explorer any more but the 305/4.9 collapsible dob is listed with a 70mm secondary. http://skywatcher.com/product/bk-dob-12-collapsible/
  12. Handsome, Witty, Charming . . . . . . . but enough about me.
  13. I started with a 76mm in big city light pollution & even the easy dso's, (open clusters) were very faint. Doubles (and a few planetaries) were OK as said. Much better now with an 8" newt but only the brightest Globulars are interesting and almost all galaxies are just invisible. I don't think any amount of aperture truly compensates for the lack of dark skies, but the bigger the better. I would say an 8" scope is the minimum for decent visual observing of dso's in Bortle7/8.
  14. Deisler, my advice is see how you get on with the straight-through optical finder that comes with the scope, and decide on your upgrade priority based on your own experience. If you like the straight-through finder ( some people do) you may not need a red-reticle finder since you can use the two-eye method to find your first naked eye star. I found using a straight-through finder on my 200p for high angle targets was literally a pain in the neck & back, (and most of the best views are high angle which minimises atmospheric & light pollution). Getting a right-angle finder transformed my star-hopping from an uncomfortable & sometimes painful chore to an enjoyable experience. If you get a right-angle finder you might as well go for a RACI & avoid the mental gymnastics of flipping the image every time you look at a chart. You cannot use the two-eye method with a right-angle finder so you will probably need some sort of "gunsight" like a Telrad or Red Dot Finder to find your first star, but not both on the same scope. I'm such a cheapskate that I just use an empty " sighting tube" mounted alongside the RACI. Whatever you decide, enjoy!
  15. Hi Deisler, One reason is cost (FLO prices); 200p skyliner dobsonian £289 200p EQ5 which is the minimum EQ mount for that scope for visual £479
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