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pregulla

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Everything posted by pregulla

  1. These values from minimum/maximum/optimum magnification don't mean much. Usually people think more in terms of exit pupil (aperture divided by magnification, or eyepiece focal length divided by focal ratio, so 30mm eyepiece in F/6 scope will give 5mm exit pupil). There is no minimum magnification, but if exit pupil is larger than your dilated pupil the image won't become brighter as you go lower in magnification, still may be useful if it provides larger true field. If the exit pupil is way larger than your pupil then you'll begin to see a shadow of secondary mirror as a dark area in the center of the field. I doubt you'll run into this issue unless you are trying to observe the moon with 40mm eyepiece or something like that As rule of thumb it is not recommended using eyepieces that provide exit pupil larger than 7mm (That's 42mm eyepiece in F/6 scope). If you are observing under light polluted skies exit pupils larger than 4 or 5mm may provide too bright and washed out images. Still might be worth using it as a finder eyepiece to get larger field of view. There is a tradeoff between image brightness and magnification. As magnification goes up image brightness reduces. General rule is that optimum is somewhere in the middle around 2mm exit pupil. It's a very rough guideline, larger exit pupil for dimmer objects, smaller for brighter objects, some objects are best viewed at much higher powers than that, some need much lower powers to fit in the filed of view. But very roughly "optimal magnification" eyepiece would be something in the 10-14mm range. Theoretical maximum magnification is usually considered around 0.5mm exit pupil, that's 400x for your scope, but seeing (atmospheric stability) will become the limiting factor way before that. I would get 2" eyepiece in the 30mm range. Something like 30mm UFF or 28mm UWA is a good budget option, but even something as simple as 30mm Superview will provide enjoyable viewing experience even if it's going to be a mess at the edges. You can also get a zoom eyepiece + barlow, that will cover all other magnifications fairly cheaply and you can play with it to find out what magnifications work for what and what fixed focal lengths would you like to get. I use 30-18-11-7 for DSO and zoom+ barlow for moon and planets.
  2. Usually 7x50 won't give you wider FoV than 10x50. You get lower magnification but narrower AFoV. Not worth spending 50 pounds on IMO.
  3. I think as a complementary scope to the Mak fast achromat should work fine. At lower powers for DSO CA isn't much of an issue, and for higher powers you already have the Mak. I use 120mm StarTravel as a complementary scope for my 12" Dob and love it for that purpose.
  4. Svbony ED line might be worth a look. 10x42 have great reviews. I have tried Svbony ED 10x50 and they were on par with Bushnell Legacy 10x50 in terms of aberrations across the field, but with better stray light control, better eyecups and better mechanically overall. Being roof design also makes them significantly lighter and smaller.
  5. I would think it won't make much of a difference. Shorter focal length will allow you to reach lower magnifications and wider field. It will make the object brighter but also the sky background, so no much help on visibility. For most object optimal magnification will be within range of your SCT. Smaller central obstruction of reflector over SCT may help somewhat with contrast, then F/6 or slower should theoretically have better contrast, but I am not sure how noticeable will it be in practice.
  6. I was able to register them on ES site. They also perform optically as you would expect from ES eyepieces - sharp almost to the edge and have perfect fit and finish. The astronomy market is too small to set up a line for fake ES eyepieces that would not be obviously fake. Bottom line - I am sure these are genuine.
  7. I have bought quite a lot of stuff from them. Including few ES eyepieces and some miscellaneous stuff. I had a good luck for the most part. One ES eyepiece had a spec on field lens that didn't seem to impact performance and I got a 30% partial refund. Another eyepiece had optical defect and I returned it for a full refund, AliExpress paid the shipping. So there is a risk of getting a QC reject for ES stuff, but on some items the price difference makes up for the risk (some eyepieces I got for less than half of what I would have cost me from EU/US stores). I would first look for sellers that offer free return, not all of them do, then if item is not good you just return it and all you have lost is time.
  8. EQ1 and AZ3 are mounts included with the telescope. OTA is just the telescope, no mount.
  9. Using filter changes focus, so you can't focus and add it later. Maybe you can get a less aggressive filter of same thickness and try using it for focusing.
  10. It all depends on your budget, preferences, observing targets etc. There is no single answer on what should you get. 2" eyepieces offer larger field of view at longer focal lengths, there is no difference in performance in shorter ones. I would suggest adding 2" eyepiece in 30mm+ range, for wide filed low power view and as a finder eyepiece. It also quite different experience compared to stock plossls. There are a lot of options depending on your budget from Panaviews to Naglers. When you don't know what to buy, a zoom + 2x barlow is a good option. It gets you covered until you figure out what your preferences are.
  11. I started by purchasing a low power 2" eyepiece, a zoom and a 2x barlow. That had my needs covered for a while and I didn't feel the urge to add anything else until I figured out what my preferences are. I would recommend something in the 30mm+ range, like PanaView or Aero ED and Hyperflex 7.2-21.5mm zoom. I would also highly recommend getting a red dot (or Rigel/Telrad) + RACI finder. Makes starhopping much more comfortable.
  12. I don't think your eyepieces are the ones to blame. On nights of reasonable seeing I had no problem getting clear views of Cassini division with ES82, or celestron zoom and even stock plossl. Maybe you have been observing when the planets are low above horizon or on nights of poor seeing. Or maybe collimation of your scopes is off
  13. Only above certain focal length 2" eyepieces offer larger field of view. For example if you want 82 degrees apparent field of view than for eyepieces with longer focal length than about 17mm you will need 2", if you want 70 degrees - than roughly above 24mm you need 2". At shorter focal lengths 2" or 1.25" by itself doesn't make a difference.
  14. If only one I would pick a zoom eyepiece. For lunar and planets you want to be able to select magnification based on atmospheric conditions, if you can't have multiple eyepieces zoom would be the best (even if you can, some people still prefer zoom). I use Hyperflex 7.2 - 21.5mm + 2x Barlow for Moon and planets.
  15. I wouldn't recommend either of these 2. 82mm Lightbridge has very fast shperical mirror - which mean it has not so great optical qualitry and very large central obstruction (secondary mirror covering large part of the aperture). CELESTRON SCTW-80 is very short achromatic refractor, it will show a lot of chromatic aberration at higher powers. The Moon will probably be bearable, but the planets will be colorful disks. It also seems to come on photo tripod - winch will make it very shaky and frustrating to use for anything other than lowest powers. If you want to spend minimum amount of money possible I would recommend 70mm F/10 achromat. It will have very little chromatic aberration and will perform much better than the two you have suggested. If you can stretch you budget a little more I would highly recommend getting something like SkyWatcher Heritage 130p or other 130mm table top dob.
  16. I have the 35mm Aero ED and very happy with it in my F/5 scopes. It is not perfect, but for given size and weight (350g) I don't think you can get any better. It is a compromise I am willing to make. I also own ES82 30mm and even though it's better corrected and offers wider AFoV I just don't use it that often because of it's size and weight (over 1kg - almost exactly 3x Aero ED weight) . Another 2" eyepiece in that range I have owned was SW SWA70 32mm and it performed significantly worse at 8" F/6 (what I had back then).
  17. There isn't much of a choice for under £30. I would suggest getting HyperFlex 7.2-21.5mm zoom. It costs more than £30, but covers entire range. At higher powers you get wider field of view, at the 21m end it is going to be a little narrower than a plossl. I would also add 32mm plossl for the widest field. A little more expensive option for a bit wider field would be StarGuider series.
  18. Just got MaxVision 6.7mm from AliExpress. The build quality seems to be the same as my ES eyepieces. After a quick look in 8" f/6 dob I didn't see any optical faws either. The stars are sharp almost to the edge. As far as I can tell these are the budget version of ES82. Not sealed and with undercuts rather than taper.
  19. The advantages of 102mm Mak would be that it's more light and compact, suitable for terrestrial observing, and because of slower focal ratio will perform better with simpler eyepieces. If small size and daytime use are high priority, than it is probably a better choice. For 130mm newt goes larger aperture, and much wider maximum field of view , because of it's shorter focal length and 2" focuser (4.1 degress max TFOV vs 1.2 degrees for 102mm Mak). So it would be a better choice for astronomy. If the person decides to upgrade later it can be a nice complimentary scope to a larger DOB for low power views and quick grab and go. Zooms can be as good as separate eyepieces, depends on price point both. I would say that Celestron/Svbony/Hyperflex zoom is a good alternative to plossls or stock eyepieces that come with scopes. Main drawback is narrower field of view at higher focal length end. I still prefer zoom for moon and planets. If you can only afford one eyepiece I agree that Starguider/SW UWA can be a good choice. I would go for something like 5mm, to get that extra magnification for planets.
  20. Seems like a good choice to me, if you can build a mount for it. 130mm is reasonably large for beginner. I like that it has 2" focuser, should be very nice for low power wide field views as well as higher powers for planets. I think good option for starters would be a zoom eyepiece and 2x barlow.
  21. Celestron 7-21 is indeed worse than 8-24mm, but there are other 7-21 zoom eyepieces that are fine. I was talking about Hyperflex 7.1-21.5, shorter focal length will allow some extra magnification without using a barlow.
  22. I think collimation is most likely the issue. The Moon is very forgiving from my experience and may look good even if the scope is not well collimated or cooled down. Maybe eyepiece itself is of poor quality, but it still should perform reasonably well in the center of the field of view and 65x should be enough to see some details.
  23. I guess the problem is the switch from dob to 70mm refractor. Everything is going to look small or dim or both in comparison. The barlow that came with the scope is probably of poor quality. Pair it with not the best eyepieces and high powers and you won't see much. 4mm is too much magnification for that scope as well. 32mm plossl and 7.1-21.5mm zoom should be a good starting set, and may be everything you need.
  24. I use 40mm long 2" extension tube + low profile 2" to 1.25" adapter, about 10mm tall. All my 2" and 1.25" come to focus, 35mm would work too, 50mm is too much. BTW brass compression ring doesn't help to center the eyepiece, it just prevents the screw from leaving marks on the barrel, it even may hold some eyepieces with undercuts worse than just a screw
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