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pregulla

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Everything posted by pregulla

  1. 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.
  2. 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.
  3. 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.
  4. EQ1 and AZ3 are mounts included with the telescope. OTA is just the telescope, no mount.
  5. 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.
  6. 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.
  7. 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.
  8. 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
  9. 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.
  10. 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.
  11. 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.
  12. 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).
  13. 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.
  14. 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.
  15. 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.
  16. 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.
  17. 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.
  18. 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.
  19. 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.
  20. 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
  21. An update after using it for a while. For my purposes (low power wide field) AZ3 was solid enough to carry the 120mm. I added an angled arm with removable counterweight - that solved the diving near zenith issue and made the mount pretty usable, but I still needed to move the tube when going from lower to higher altitudes. Still I am glad I didn't go for AZ4 or AZ5 as I recently scored a used Berlebach Uni17 with GR-III head for comparable price - this thing is super smooth and solid and a pleasure to use.
  22. I have found 11-12mm range most useful for DSO. I usually use 35mm Aero ED as a low power/finder and then switch to ES82 11mm for most objects. Some objects benefit from 16mm or 24mm, but 11mm does the bulk of the work :). BTW for planetary I prefer zoom eyepiece + barlow. Best magnification varies with seeing from night to night and zoom allows to get most of it. I quite often push above 200x on the Moon and Jupiter. On the other hand I found that wide filed eyepieces (ES82 11mm, ES68 16mm) show lateral color in the outer field so the useful field is pretty close to that of a zoom eyepiece.
  23. There is a confusion between two things in this thread. First - decrease in image brightness as a result of increased magnification/decreased exit pupil. Everyone agrees on that, but this effect is not unique to Barlow. If you just use eyepieces with different focal lengths the effect will be the same - dimmer image at higher magnification. Second is reduced light transmission due to extra glass added. With good quality Barlow this effect is too small for human eye to detect. It is unrelated to all the principles described above and this is what people mean when they say Barlow doesn't decrease brightness. Lets say you use 20mm eyepiece. Then you add 2x Barlow. The image got 4 times dimmer because of increased magnification and say extra 3 percent dimmer because of light transmission loss. Now you just use 10mm eyepiece. The image is still 4 times dimmer compared to 20mm just without the extra 3 percent loss. If you compare 10mm to 20mm+2x Barlow you won't be able to tell the difference in brightness. So we can say Barlow doesn't decrease brightness, now that we have taken the effects of magnification out of the equation.
  24. The article is poorly worded (or the author is decieving on purpose?). Doubling the magnification will reduce the brightness by a factor of 4 (or by 75%). It doesn't matter if it is done by using a barlow or a shorter focal length eyepiece. The article makes it sound like a barlow robs you of 75 percent of light that would be there if you just used an eyepiece, which is false. Quality barlow with modern coatings will only loose few percent of light.
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