Amateur Astronomy Video 4 – Eyepieces, Focal Length, Magnification

This is my 4th video in my series about Dobsonian Mount telescopes. It is all about understanding eyepieces and their relation to the telescope. Learn how to determine the magnification of an eyepiece with your telescope and how to choose new eyepieces.


Da Lu says:

I agree with all the comments here below… Very helpful for me as I am to get my first telescope this spring…

Michael Del Rossa says:

looks like my astro tech , looking for a 2″ zoom threaded eyepiece. Know of any?

John Owens says:

Thank you for the video. Very helpful.

MWH says:

quite helpful, thanks.

Michael Wilson says:

I was hoping you could explain why I saw an unobstructed view of the sky and then, the next time I brought it out, I could see the secondary mirror and its supports. Light source would be behind it but it illuminated the secondary mirror. I’m new to this and think I am doing something wrong.

Kyle Bender says:

what do you need to see nebulae I have a skyprodigy 130

Fred Kukowski says:


Doesn’t aperture create field of view?

If you have an eye piece with 100o field, it won’t matter if your aperture only opens to 60o field…..

78 Tranz Am Man says:

I love that 17mm you got. Great for my Mead ETX-125 and Zhumell 12″

Lip stick says:

Did you say that was 12 or 14″ telescope???

Which leads me to ask? Which is better a 14 or 12″ telescope for video and photography of Jupiter, Saturn, and Mars to start with???

How much did each bellow cost???

Slabsurfer says:

yes excellent video

Glen Ramroop says:

Great Explanation Benjamin In Layman Terms, Thank you.

Smiley Noel Productions says:

I just want a good eyepiece for my xt6 enough to have a very good view of the outer and inner planets can any one of you help me out

ashwin cool says:

i have an 8 inch dobsonian,its highest magnification is 480 ,what would be the best magnification range for this telescope to see planets

RELI GI says:

If baader hyperion 13mm is good in 10″ GSO?

John Dogood says:

This video was extremely helpful. It made a somewhat difficult topic seem concise and easy. Keep up the great work!

Mc99911 says:

so looking online i can get an explore scientific 82 degree eyepiece for $160 and it costs the same for a 68 degree baader Hyperion eyepiece, is there any reason?

sarblade says:

Thanks for this upload, this took a lot of the mystery out of eyepieces and magnification! One thing that you could mention next time is loss of light when the different lenses are used. The more its bent, the more loss!

Michael Wilson says:

Lay my last. His explanation of the focal point made sense and I removed the Barlow. Thanks from a noob.

musiclucho says:

Good video Benjamin!!! Forgot to mention that you really don’t get the total of FOV that comes (AOFV) with your eyepiece because you still have to divide the AFOV in the magnification and then get the true field of view (TFOV)

zytigon says:

Hi Benjamin, What magnifications do the Baader eyepieces give you ?

I’ve bought a GSO 10″ dobsonian reflector a few days ago. I’ve only got a 10mm & a 15mm plossl eyepiece. There has been thick cloud since I got it. What lens would I need to find galaxies & nebula easily ? Would I need a 25mm or 32 mm while seeking the object then switch to a 20mm ? What eyepiece is best for the Andromeda galaxy ? If I wanted to reduce the cost would it be best to get a quality 20mm and cheap 25 / 32 mm ? Do people get more for their money using a 6″ reflector with top quality eyepieces compared to a 10″ reflector with cheap quality eyepieces ?

DarkSagan says:

Awesome video. I need that eyepiece…but 350.00 damn

Nick Sci-Tech says:

Another great vid, keep it up 🙂

Gander Stein says:

I cannot believe how comprehensive you were, with such a terse video. Nice video.

RELI GI says:

That is GSO 10″ ?

James Webb says:

Great video! Have you ever looked at building a telescope?

Alberto G says:

Awesome videos, thanks!!

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