2x vs 3x barlow lens

[penno (John)]

Hello to all, I was wondering which barlow lens to buy for my SAXON F15012EQ3 Newtonian Reflector Telescope.
my telescope came with a super 25mm wide angle and a super 10mm lens.
My understanding of a barlow lens is that if I buy a 2x barlow and fit my 10mm lens to it, it would increase its magnification from 120x to 240x is that correct. the focal lengh of my telescope is 1200mm.
could I buy the 3x barlow and get a possible 660x magnification from my 10mm lens or would it not be possible with the focal lengh being 1200mm.

[marki]

Yes the 2x will double "the power" but it will also cut a sizable chunk of light that reaches your eye. Barlows magnify but they also make object appear dimmer. Unless you live on a high mountain in Chile you will never use 660x as the atmospheric conditions will not allow it so forget the 3x. Don't be fooled by the power game unless you enjoy viewing unresolved blobs at the eyepiece. I would suggest that you save and buy some good quality eyepieces that are suitable for your focal length as these would be a far better investment.

Mark

[JD2439975 (Justin)]

Hello John

The 3x will give you 360x magnification not 660, but that was probably a typo.

360X is usable on the planets but as Mark said introducing that extra glass into the optical train just makes things blurrier, better to get a dedicated EP for the job.

I went the barlow route myself and am not overly impressed with them, especially as they were cheap ones & my EP's are not.

[penno (John)]

Hi again thanks for the replies, I have taken your advice and I am not going down the barlow route.
I have seen this one its a SAXON ED2 5.2mm 1.25" Eyepiece.
Could anyone tell me what the ED2 means please and would it give me good magnification on the planets and the moon.

[JD2439975 (Justin)]

John, the ED stands for 'Extra-low Dispersion' which means less chromatic abberations (the blue-red fringing) on the edge of objects.
The 2 I imagine is just a version 2 of a previous range.

Running it through David Green's eyepiece calculator gives...
Exit pupil - 0.65mm.
Magnification - 230x.
True FOV - 0.24 deg.

I've read not to go below 0.50mm exit pupil, which on your scope equates to 300x mag (sorry about the 360x before, was thinking of my own scope), and anything above 400x requires excellent & rare seeing conditions.

Those figures should give you Jupiter & it's four main moons nicely in the field of view without pushing magnification of seeing conditions too hard.

As for value for money or quality of the EP I can't say, never having used one.

Hope that helps.