Telescope Barlow Lens - A Strange Example Of How They Work ( by Reflactor )
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- Опубликовано: 21 сен 2024
- This video shows how the Barlow Lens works on a telescope while demonstrating one of the strangest types - the variable power Barlow Lens by Orion.
#telescope #barlow #lens
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2) Soundtracks used with permission from my video editing suite, Camtasia
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Discussed in this video:
The Barlow Lens
Dobsonian telescope
#reflector
#reflactor
@reflactor
I picked up a 1 1/4" no-brand variable Barlow around 30 years ago for around $5. I bought because I was curious and it was cheap enough for a gamble. It is simply the tube with the lens elements and no stops. The lens is held into place with an O ring. It works surprisingly well but you need the right conditions that allow for higher magnification.
Thanks for the comment. I wondered how the Meade Barlow made the adjustment (it doesn't have slots).
My first telescope was a 1963 terrestrial 60 mm Tasco. It had click-stop magnifications 15x, 30x, 45x, 60x. I’m pretty sure it had a variable Barlow.
Some premium eyepieces seem to be designed as regular Ry pieces with built-in Barlows.
Yes. The SVBony Gold-band and Red-band eyepieces both have a few with permanently attached Barlows.
Thanks for not saying smash the like button, you've earned your like
LOL, I never smash the like button, but I do press it. Or boop it.
Love the thumbnail picture 😂....hope you don't need to look very high in the sky with that monster
It's amazing what you can make with Microsoft Paintbrush. Hahaha.
Very informative. One of the best on here
Thanks!
Every Barlow that I have ever looked through that was stronger than 2X stole so much light that the image became too dim to view comfortably. Even higher end units like Tele-Vue's. I recently constructed my own 2X Barlow using Red Henry's technique of repurposing a camera teleconverter lens. It seems that the quality of this lens allows for the nearly 100% transmission of light.
I obtained a 52mm Plossl from Steve Case that was made using Red Henry's method and it provides exceptional views. The lenses themselves are not perfect and you can tell they come from a well-used set of binoculars, but the view is perfect from edge to edge.
2:39 that was so smooth I had no choice but to laugh and then hit the like button. 😂
Haha, thank you for watching (and pushing the Like button!)
There are Celestron OMNI barlow and SVBony sv137 that have lens unscrewed and screwed directly to eyepiece (it is filter thread) and it gives x2 or x1.6 accordingly. So it is also "sort of variable focal length".
For any simple reducer of barlo the magnification reduction is calculated as (1 - d/f) where f is barlow/reducer focal length and d is distance between eyepiece/sensor focal plane to the lens itself. In case of barlow since it is concave lens its focal length is negative so it creates magnification, for reducer it is convex and focal length is positive so it creates reduction.
Finally with every barlow/reducer you can play and change spacing to achieve different reduction/magnficiation factors. In fact it is almost even exactly x2 or x3 since all eyepiece have slightly different location of focal plane.
Thank you for your comment. This will come in handy.
Barlows do effect the eye relief on many types of eyepieces, less so on designs that effectively have a barlow built in like naglers and many others
I remember the Meade version from the late 90s /2000s but i never bought one as i dint think i would like one that changes.. I like the Orion but yes dust can get indide so another issue to think about however if its in a case all the time it should block dust
Good point and true. Most of mine are in cases. Interesting note - the case that this came in was a foam case, but it was from the 1990's and the foam had become powderized, coating the lenses. I had to clean it very carefully.
Please do a vid on those RKEs you got!
I see you are a person with fine tastes. :) I'm pretty excited about the RKE's - I've been looking at getting a set for a long time. They are featured quite heavily in my (soon to be released) video on the Astroscan telescope.
@@reflactor So you got the telescope too! Cool! Yes those eyepieces have a good reputation. I have never seen a complete set like that.
instant like klicked
Thanks! I hope the video was helpful. :)
@@reflactor interesting as always. youre a friendly guy. Even without any new Info its fun to watch you tinkering with stuff
I've got some tinkering videos in the works - stay tuned!
I know you can put your barlow in front of your diagonal to up the power.
This is good to know!
Was there any vignetting in combination with the 32mm eyepiece? In my experience with experimenting with Barlows some eyepieces have vignetting and some not. When observing planets it's not too bothersome though. Still, I find it more practical to simply use a shorter eyepiece than inserting an extra piece like Barlow between when changing the magnification.
Good question. I didn't notice any, but the only thing I could see was the planet and its moons. I'm in a Bortle 8 sky, so not many stars show up even in a wide field view like that.
Vignetting is mainly an issue with shorty barlows. Long tube barlows don't have that issue
That method of moving the lens is certainly an easy way (cheap), but it seems that would be fraught with unexpected disastrous results. Don't believe I have ever seen one of the those. My ES 82º set came with a 2X that probably weighs 16 ozs, or close to a ton.
It's not very often that physical violence against an optical tool is effective in astronomy. Some of the bigger ES optics are the size of a pineapple!
Are them orthos, love to hear more about them. Thanks.
The orange eyepieces shown in the video? Those are Edmund Scientific RKE's, built for the Astroscan (the "red ball") telescope.
@@reflactor cool, have a great weekend.
Everyone loves the 28mm rke, as it is perceived as the eyepiece disappearing and the image hovering in space. I never really got that effect, and I sold my Edmund eyepieces, I had the 28mm plossl as well and rke in 28, 15 and 8, and maybe one other, and I think I had another of the plossls. It has been over 10 years maybe 12, so I don't remember exactly. Since collectors paid a decent price for them, it made sense to sell them at the time
I far prefer the 26mm meade smoothside super plossls and 26mm silvertop plossls that used to come with meade and celestron SCTs in the 80s and early 90s. They also have a similar effect as the 28mm RKE because they have a big eye lens and not much of the smoothside body around them to get in the way.
One of the best eyepieces to get this effect is the 35mm celestron ultima/orion ultrascopic/antares elite/parks GS-5, which are no longer available, but it appears the baader eudiascopic that is currently available is the same thing. These are 5 element pseudo masuyama "super plossl" design like the smoothside meade super plossls.
The 32mm meade super plossl is a similar experience. Televue smoothside 32mm plossl is almost the same but the lens is recessed into the body a bit, where the others have the lens at the top.
Still waiting on that astroscan/rke video
Me too. I've got the outline and one of the Astroscans is halfway through restoration. I have to ask one of the designers a question before I send the mirror off to get recoated.
LOL I always imagine that a 2x Barlow halves the focal length of whatever eyepiece you use (without changing the apparent field of view).
I guess, mathematically, they both work out to the same answer!
Can anyone help me please?! I used to take pics through my telescope with a Samsung Galaxy A71 and they looked pretty good. But my A71 gave up on me, so I switched to the Xiaomi 13T Pro, which is supposed to have a better camera. When I try to take pics through my telescope, they look great in the view finder, but once I take them, they look like crap. Planets have a weird blur on them with rainbow colours around and most of the detail is lost, the moon is really noisy, especially in the dark areas around etc... Keep in mind, they look good in live view before taking them. I really need help with this. Thanks!
There may be a few issues at play. Does the Xiaomi 13T have "multiple lenses"? You may be wrestling with that. I've heard that is causing problems with the new iPhones. Also, with the Samsung phones, the real magic was in setting up the camera settings. I have to go into the manual modes to set focus, ISO, and shutter speed. The Xiaomi 13T may have unique ways to deal with that. Good luck. Be sure to watch the setup in the later half of this video here for my Samsung Galaxy: ruclips.net/video/GcpLAZKICw0/видео.html
Orion doesn't build anything, they just buy it in bulk with their name put on it
Bang my Barlow lens? Sounds kinda dumb.
There is no need to do that for most Barlows. But for these adjustable Barlows, it's a viable method.