Newbie question, don't laugh but...

[JohnJ]

What is a Barlow lens and why do we use them?

Cheers

[John]

What is a Barlow lens and why do we use them?

Cheers

A barlow lens multiplies the effective focal length of the scope by a certain amount, usually x2. This means that a given eyepiece will deliver 2x as much magnification when used with a 2x barlow lens.

[LukeSkywatcher]

A very good cheap barlow lens is the TAL 2X. It is too cheap for what it is if you ask me. Glad i have one just incase they ever decide to increase the price of them. I doubt they ever will though because they wouldnt sell as many.

[Ewok]

Question for Jahmanson,

Do you reccomend using barlowe lenses, and which would you suggest ?

[JohnJ]

So if my Skymax 127 is advertised as 300xmagnification and comes with a 2xbarlow that means my scope becomes 600xmag? Do you loose quality? Or am I way off here?

[Jimmy Stix]

Hi John I am a newbie too and I just got the 127 for xmas.

To work out magnification divide the focal length of the scope by the size of eyepiece. I was provided with a 10mm and 25mm so with the 1500 FL that gives me x150 and x60. The Barlow would double these but I understand x300 might be right on the limit of this scope and not that easy to obtain.

[Watcher]

Just remember that the more magnification used, the harder it is to keep a stable and bright image and poor seeing will have a bigger impact.

I have a Skymax 127 which came with a 6mm eyepiece giving 250x magnification without the Barlow. The eyepiece only has a tiny lens to look through. If you use the 15mm eyepiece with the barlow you get 200x and a much more comfortable view.

[JohnJ]

thanks for the replies, really helps a lot.

So just for an example what sort of typical eye piece size and barlow (or not) would be used for viewing the moon?

[LukeSkywatcher]

thanks for the replies, really helps a lot.

So just for an example what sort of typical eye piece size and barlow (or not) would be used for viewing the moon?

10mm is a good EP to observe the Moon with. If you barlow it with a 2x then you are using a 5mm EP which might make things a bit unsteady as the turbulance in the atmosphere will also be doubled and the Moon will appear to be "boiling". On some nights when conditions are perfect this wouldnt really be an issue. But certainly anything from about 8mm-10mm for the moon is fine without a barlow.

[ronin]

With the Mak an eyepiece of 25mm would deliver about 1 degree of view, as the moon is 1/4 you would get all of it in and have a little leeway for drift before you would need to recentre the moon.

If you are intending to pick out individual and specific craters and features then I would guess 150-200x is required. Although at that good tracking and allignmnet would be essentail. Suppose 8-10-12mm would be required for that detail.