eyepiece advice needed

[peacefrog]

Hi.

I've bought a Meade ETX 90PE goto telescope and it came with only one eyepiece, a Meade Super Plossl 26mm. I want to buy a barlow lens. First, can anybody advise me on which to buy? Like what's value for money, what are best, and what to stay away from. Second, while I've been looking around I've seen 2x, 3x and 5x barlow lenses. Most seem to be 2x. Is there a reason for that? I mean the more the magnification, is there degrading of the image? I'm just wondering why the 5x seems less popular than the 2x.

Any advice welcome.

Thank you.

[pbyrne]

Hi there

A barlow to be on the look out for is the Celestron Ultima 2X, this is an excellent barlow and they come up second hand occasionally, it is one I have used in the past and can highly recommend it.

Your 26mm will give a magnification of 48, a 2x barlow will give x96, a 3x will give x144, a 5x barlow will give a magnification of 240. What the barlow will also do is increase the focal length of the scope. the 90 PE has a focal length of 13.9, 2x = 27.9, 3x = 41.7 and a 5x = 69.5. A focal length this low will be impossible to see through, as will 41.7, so with the ETX I would stick with the 2X.

Hope this helps.

[brantuk]

I have a Tal barlow - very good budget ep - hard to beat for the price. The Celestron Ultima seems a firm favourite here though I don't have one (bit pricier too). 2x is usually a good start - higher powers (3x, 5x, etc) get used a lot for imaging.

Your Mak has a 1250mm focal length at f/12.8 - nice and long for sharp moon and planetary viewing. The thing to bear in mind with magnification is that in the UK, around 200x is probably the max you would want to use due to the lack of good seeing. It would have to be a very clear night free of atmospheric disturbance.

So a 10mm ep would give a mag of 125x - barlowed would double this to 250x (probably a little too much). A good 6mm ep (or a 12mm barlowed) would be around the max 200x mark - so you have a guide. It's a small aperture though and a barlow introduces more glass for the light to travel through which can have a "blurring" effect.

Sometimes a lower power ep will show a smaller but clearer image than a higher magnification. I'd suggest a good quality 8mm might give best results at a reasonably high mag (156x). To view larger objects - a lower power ep would be useful (eg 20mm to 25mm) but make sure it's a wide angle (60 degrees at least).

Hope that helps

[peacefrog]

Thanks pbyrne, it does indeed help. I will go for the 2x.

As for makes, I would still be interested in other peoples opinions.

[dweller25]

The Celestron Ultima actually gives around x2.25 magnification. It is an excellent Barlow.

[peacefrog]

Thanks brantuk, that is most helpful. Very well explained. I feel wiser already. Much obliged.

[Tink_Archived]

The Celestron Ultima actually gives around x2.25 magnification. It is an excellent Barlow.

its good to read a few opinions on this barlow I managed to purchase one off a member on here today from the for sale section, looking forward to getting hands on it asap