Problem focusing with new barlow lens

[cushbag86]

Hi Guys,

             Recently purchased an astro revelation 2.5x barlow lens. I cant get a sharp focus with it. I focus in as far as I can but not quite getting a clear image. Any ideas? Thanks Cush.

[YKSE]

It'll be easier to answer your question if we know what your telescope is , and what eyepiece you're using together with the barlow when you have this difficulty.

[cushbag86]

Ive got the Skywatcher 120 600  refractor. Im using astro revelation plossl 12 and 6mm lenses. Thanks!

[Sandancer10]

Hi you could try putting the Barlow in the focuser until just past its collar - it worked for me.

[YKSE]

I don't have experience of that scope, nor focus difficulty, there's another discussion here about focus difficulty which you may keep an eye on.

http://stargazerslounge.com/topic/204277-trouble-focusing-after-adding-a-barlow-lens/

Hope you get it sort out in some way.

[Reeny]

The Revelation Barlow pulls the focus point quite a bit further into the tube.

You may need to:

- modify the focus adjuster,

- use a different eyepiece which can focus further out,

- or use a different Barlow.

The 2.5x Revelation is OK on our 8-inch SkyWatcher dobsonian.

But I needed to shave 3-5mm off the 3-inch scope focusser to make the barlow work properly on the little-un.

If you have any spacers or collars - get rid of them, and try again.

This is the 3" with the black plastic locking collar trimmed down by about 5mm.

The focusser tube is only a few mm from maximum inward travel, but it focusses no problems now.

The 2.5x Barlow performs best on the Dobsonbian scope, where it isn't a problem.

 

[Reeny]

PS - On a 600mm tube, the 12mm at 50x will barlow up OK to 125x magnification.

But the 6mm will rarely give a clear image at 250x magnification, unless the seeing conditions are absolutely perfect.