So we just bought telescope and are fairly new to astronomy. I'm having such a difficult time with the placement of the Barlow lens. I've tried to focus the image with the 25mm eyepiece and then switching to the 10mm eyepiece to get a closer image and that works perfectly fine. When I attempt to place the Barlow between the telescope and eyepiece, it's dark, like I no longer get any light or image for that matter. It's kind of an embarrassing question since I am a high school science teacher and can work a microscope just fine. What am I doing wrong?

When I first started out I had the same problem,
My first scope was not that expensive so when I put a 2X or 3X Barlow
on my scope it would move the position of my scope.
I finally figured out that I had to readjust my scope thru my finder scope with the Barlow on it first
and then readjust the focuser.
Make sure Your finder scope is adjusted to your telescope, I check mine all the time.
I hope that will help .

Michael

Can you tell us a little more about the telescope your using? (Brand, type, focal length, mount, etc.) It may simply be too much magnification for the scope you have.

You bring up a good point Josh. Not just about the factors of the scope and so forth to help.
You said something more important and didn't realize it.
Many people think using a high power is the way to go. Which is not always needed .
In fact it can be more of a curse than a blessing. Few understand the higher the magnifacation, less light gets to the retina. However it's at times needed to split binaries and see other objects. We all heard of this great telescope with 500x. Yeah right.
Also the fact that by increasing magnifaction one is also amplifing defects in the seeing condidtions. Just my 2 cents.
Tom