barlow lens??

[sparks1]

Hi all,

can any one out there explain why a barlow lens is the lens to have!! and why, whats the difference with a barlow and any other??

(new to this)! thanks

steve.......................................

[Odd Dob]

A barlow is something you use in conjunction with your other eyepieces. It effectively changes the focal length (increases it), it increases your repertoire of focal lengths. On its own it does nothing.

[Bizibilder]

As Odd Dob says a barlow is a lens that effectively increases the focal length of your telescope. A 2x barlow "doubles" the focal length of your scope. The end result is that it "doubles" the magnification of any eyepiece that you use with it.

For example: My Skywatcher 200P has a 200mm diameter mirror with a focal length of 1000mm. A 10mm eyepiece will give a magnification of 1000/10 = 100x. With a 2x Barlow in place the same eyepiece and scope will give a magnification of 200x.

To use the Barlow you simply place it in the focusser tube first and then place the eyepiece into the barlow tube.

The advantage is that for the cost of one barlow lens you can, in effect, double the number of magnifications from your eyepiece collection - very useful!

Barlows can also be used with cameras to give increased image size on the sensor.

You do have to be aware, however, that magnification is not necessarily a good thing in astronomy!! For the Moon and planets you are usually restricted to around 200x - 250x by the atmosphere - you simply wont see any more by going higher. this is called "seeing" (or rather the lack of good seeing). For stars and DSO's you often only need a magnification of 20x - 50x (or even less!) for the best views.

[M4lcs67]

I am new to this astronomy malarkey, but was told by an experienced stargazer that they can be a very useful tool. Also there are different types and qualities. Some good and some bad. I bought a Celestron Ultima 2x Barlow and so far it is doing really great.

[brantuk]

The Celestron Ultima is the best I've used in the £80 ish bracket. Good value for money are the cheaper Tal barlows - beyond that the Powermates are regarded as the very best. As above a 2x will double your focal length (I think of it as halving the eyepiece mm). But do remember you're putting more glass in the light train - anything but the Powermates will degrade the views

[sparks1]

thanks for that info on barlows (now i know what they are all about)

cheers!!