barlow 5x

[shyam]

hi

1.25 Inch 5x Fully Blackened Metal Barlow Lens / T Adapter for Telescopes -  can this support on my astromaster 114 eq bird jones reflector telescope? 
  shyam menon

[RT65CB-SWL]

Hi Shyam.

I am not au-fait with 'bird-jones' type of 'scopes, but from what I understand from since becoming a member of SGL, they have an in built-in element in the drawtube/eyepiece holder that is supposed to give you some extra magnification, i.e. 1.5x - 2x

Many 'Barlow' lenses above 3x are normally used when imaging rather than visual.

Personally I would upgrade your OTA. Apologies in advance if I appear negative.

[LukeSkywatcher]

^^^^^^^What he said. 

I'm thinking that a 5x barlow would be way more than a 114mm scope can handle. 3x and above are mostly used for imaging. I'd get a 2x barlow. 

 

[Demonperformer]

The extra lens corrects the spherical mirrors in these scopes. I would agree that 5x is probably NOT  your best bet. You will always see more on a smaller bright image than a big faint one.

[RT65CB-SWL]

The extra element that @Demonperformer refers to, make 'bird-jones' type OTA's a pain in the backside when collimating.

If you do go for a Barlow lens I would suggest a 2x max. I used to have a 'non-bird-jones' type @114mm & 900mm f/l (or thereabouts) and tried 3x Barlow and was very disappointed when used with an H20mm [Huygens] e/p. This was before Plossl e/p became defacto when buying a telescope.

[Zeta Reticulan]

I sometimes use a GSO 5x Barlow on an 80mm short tube achromat for visually observing the moon and planets. In that way I can utilise orthoscopic or Plossl type eyepieces of between 18mm & 12.5mm focal lengths to achieve magnifications high enough for planetary observing. 

I think it all depends on what eyepiece focal lengths you are planning to use with the 5x Barlow. If you stay within the magnification limits of the aperture size of the scope I can see no real problem. 

With a 114mm aperture (approx 4.5 inches) the maximum magnification would be about 228x. In very good conditions you may push 270x for lunar observation (60x per inch of aperture), although this will probably not be often achieved.

Also, some 5x Barlows may have a tendency to produce slight vignetting if they don't have enough clear aperture width.

If you stay within reasonable magnification limits for the specific target there should be no problem using a 5x Barlow IMO.

[Cosmic Geoff]

Apparently the focal length of this telescope is 1000mm.  With a x5 Barlow the focal length becomes 5000mm.

With a 25mm focal length eyepiece, the magnification becomes x200

With a 10mm eyepiece, the magnification becomes x500 (unusable).

Get a x2 Barlow if you must, and it's as the others said. If the Barlow costs more than a few pounds, you'd be better advised to save up for another OTA.