How to Pick the Best Barlow Lens for Your Telescope & Eyepieces | Amateur Astronomy

so you've bought a new telescope it comes with a few accessories probably one or two eye pieces but my guess is the first thing that you're going to think after you take it out set it up and go out for your first night of star gazing is what can i buy next in today's video i'm going to help you answer that question by taking a look at one of the most useful accessories for any telescope a barlow lens if you enjoy this video please like it and join our growing community of amateur astronomers by subscribing to this channel also be sure to let me know in the comments section below any questions that you have about barlow lenses or any experiences that you have from ones that you currently own now let's get started by taking a look at how a barlow lens actually works and how they can be one of the most useful things that you ever buy for your eyepiece collection named after english mathematician peter barlow this incredible accessory for your telescope has the ability to double the magnification of every eyepiece that you own it does this by increasing the effective focal length of your telescope for example my telescope has a focal length of 1200 millimeters when i take a barlow lens it pretty much turns the focal length of my telescope into 2400 millimeters thus doubling the magnification of the eyepiece that i'm using let's take this 25 millimeter eyepiece for example that came with my telescope to determine the magnification for this or any other eyepiece you're going to want to take the focal length of your telescope and divide it by the focal length of that eyepiece so by itself my 1200 millimeter telescope and 25 millimeter eyepiece would provide about 48 times magnification this is a great starting point for lower magnifications to hunt down objects and even get really nice views of the moon in some of the larger deep sky objects now let's take a two times barlow lens and place it right in between the light path of our telescope and our eyepiece my telescope has now turned into a 2400 millimeter scope making the 25 millimeter eyepiece now show 96 times magnification so with one new piece of equipment i've basically doubled the number of eyepieces that i have in my collection when purchasing a barlow lens or any other type of eyepiece you're going to want to make sure you don't push your telescope beyond its capabilities to help determine what the highest useful magnification is for your scope take the diameter of it and multiply it by 30. for my 8-inch dobsonian telescope that's going to tell me that on most nights the maximum that i can push it in terms of magnification is around 240 times on very rare nights if it's crystal clear and steady sometimes i can push it to 40 or 50 times its diameter but those nights are few and far between save yourself the disappointment of blurry views and don't push your telescope on most occasions past 30 times its diameter now that we have an idea of how barlow lenses work along with some useful tips to help you determine the best useful magnification for your telescope let's head outside and do some good old-fashioned observing to test this budget barlow lens with our closest neighbor the moon i'm outside on a beautiful night to test out a barlow lens on the surface of the moon tonight i'm going to be using the astromania two times barlow lens i bought this a few years ago for around 20 and i'll be sure to leave a link to it in the description below but if you simply go to amazon.com and type in two times barlow lens you'll find a number of different companies these days that put out similar products for around the same price to begin with tonight let's take a look at the moon just with our eyepiece the 25 millimeter that came with this telescope this is going to give us about 48 times magnification on the surface of the moon let's start right there to see what we have 48 times magnification is kind of the sweet spot for me in terms of starting out for observing the moon it's a low magnification you're going to get the entire surface of it in your field of view at least with this telescope that i have right here and it just really shows off especially in this early phase of a crescent moon the shadows moving across the moon the mountain ranges the terminator line the device the light and dark portion of it this is my favorite time to get out and observe the moon and it is looking great tonight now let's take our two times barlow lens attach it to the telescope and see what the results are now anytime you add glass to your setup you run the risk of adding aberrations and imperfections i've got to say though this is a pretty clean image especially for this price range for a barlow lens the waviness that you notice is from the moon being low to the horizon in my telescope not fully cooling to the nighttime air one thing i am noticing though is you do have to have your eye kind of right over a sweet spot in order to see the full image if you move or bob your head around a little bit you kind of lose that sweet spot and the image can get a little bit darker that's not a very uncommon thing with barlow lenses in this price range but i still think it's an important thing to point out once you've bought a barlow lens be careful not to duplicate magnifications with future eyepiece purchases remember that a 25 millimeter eyepiece with the two times barlow lens gives the same magnification as a 12.5 millimeter eyepiece without a barlow lens along with a two times barlow lens you'll also find a popular choice being a three times barley lens regardless of whichever type you buy just make sure that you don't push your telescope beyond its highest useful magnification overall i'm very impressed by this we've got a clean sharp image of the moon we have doubled the magnification of our 25 millimeter eyepiece i effectively have created two eye pieces from this one accessory that i bought so as a barlow lens right for you i think the answer for almost everyone in amateur astronomy is yes but the type of barlow lens that you're going to buy is going to depend a lot on the telescope that you currently own if you've just bought your first telescope you're going to definitely want to go with a budget friendly barlow lens for probably under 50. but for those of you with high expectations and high dollar telescopes you're going to probably want to look at something like a teleview barlow lens which can easily run into the hundreds of dollars it just depends on the equipment that you currently own and what you want to get out of your views but for my orion xt8i dobsonian the budget-friendly barlow lens is what i almost always go to for my observing and it almost always pays off in terms of the views if you've enjoyed this video please like it and be sure to let me know in the comment section below any questions that you have on barlow lenses and any ones that you currently own that you'd like to share with others in this community thank you all so much for your continued support and clear skies from late night astronomy [Music]

Channel: Late Night Astronomy

Views: 7,029

Keywords: what barlow lens should i buy, barlow lens for my telescope, how does a barlow lens work, what is a barlow lens, should i buy a barlow lens, what's the best barlow lens for my telescope, how do i use a barlow lens, best 2x barlow lens, best 3x barlow lens, what barlow lens should i buy for my telescope, great budget barlow lenses, best barlow lenses, what barlow lenses should i buy, best barlow lens for astronomy, amateur astronomy

Id: 09tk5GU4HBU

Length: 8min 20sec (500 seconds)

Published: Fri Jun 25 2021