Telescope Buying Guide: Barlow Eyepiece

Video Transcript

"Another option to purchasing eyepieces is what is called a Barlow. A Barlow is essentially a tube here with a lens at the end of the barrel, and that magnifies the eyepiece that you're using in your telescope by a factor of two or three, depending on the Barlow. Two or three being the most usable. If you're wondering why you might use such a device, well typically your telescope will come with at least one or two eyepieces of different focal lengths. This is a twelve millimeter eyepiece here, and if you can see the lens we have to look through is not very generous and it kind of be kind of difficult to find that sweet spot. So let's say this eyepiece gives me 200 magnification in the telescope I want to use. This eyepiece right here with a much more generous lens, gives me 100 magnification when I put it in my telescope. And as you can see, greater surface area on the lens there makes it easier for me to look through and easier to find that sweet spot. So in order for me to achieve the magnification that this eyepiece has but still keep that generous relief, I'm going to insert the Barlow. Here is a 2x Barlow. I'm going to put it inside the eyepiece here, or excuse me inside the diagonal. I should take this lesson myself. And then the eyepiece goes into the diagonal. Now I've doubled the magnification of my eyepiece. Now this 100 magnification gives me 200 magnification, and it could be kind of a handy little tool to have. Again, I don't recommend more than a 2x Barlow--200 magnification even is a little bit high, but in order to save the price of another eyepiece, and to get a little bit more generous eye relief, a good Barlow will run you about a hundred bucks and could be a good investment as well. Another fun accessory for eyepieces is called a binoviewer. For planetary and lunar work, these will absolutely spoil you. Well the idea is to get input to both sides of the brain by getting the light to both eyes. When you have both eyes on the telescope here, 20 magnification, 50 magnification really seems to fill out more and give you that 3D effect. So a binoviewer is a way to essentially turn your big telescope into a binocular viewer. I've inserted the binoviewer here. It does take two eyepieces this time of equivalent focal lengths. I insert them into the binoviewer here, and just like a set of binoculars, as I approach the binoviewer, I adjust the inner pupillary distance by starting with them wide, and then I'll just bring them in until the two images merge, and I see one sight. For me, I really love using the binoviewers on the moon, on Saturn, on Jupiter... it really makes those guys pop, a 3D effect. However when you do get into deep sky objects, objects that are a little dimmer, a little harder to see, the benefits of a two inch eyepiece will become apparent. Because as of now what you're doing is taking an inch and a quarter of light--binoviewers are an inch and a quarter barrel--and splitting that into two eyes. So the brighter objects look really well, but if you're going to go for deep sky, for the dimmer objects, a two inch eyepiece lets in more light and will give you a better image."