I bought some generic Kellners when I started and they are not much good compared to SMAs or Plossls. For instance if you have a 25mm and you buy 18 mm and 6mm eyepieces with a 2x Barlow you will have 25mm, 18mm, 12.5mm, 9mm, 6mm and 3mm focal lengths, though I wouldn't expect too much of the 6mm+barlow combination with that scope.Ĭhoose Celestron SMA, MEade MA or (for somewhat better quality if you can) NexStar (or equivalent) Plossl eyepieces and a Celestron Barlow for that scope (an Ultima 2 if you can), avoid generic eyepieces described as 'Kellner' or 'modified Kellner'. If you decide to buy extra eyepieces, combining a small number of eyepieces with a 2x Barlow Lens (which halves the focal length) will extend your budget. The shortest focal length eyepiece you should try to use is 2mm, but that would be almost impossible unless the eyepiece costs more than the scope, so I would say make your minimum a 4mm or 6mm eyepiece. The scopes maximum useful magnification based on the size of the objective ('D') is 192x ((D/25)*60). To see objects with a smaller apparent size you need to have additional eyepieces/barlow lenses that combined will be of a shorter focal length, or do you know this already?In case you don't: It is a short tube refractor designed more for studying wide views of starfields than planets. If Mars looked like a little red blurry dot the chances are that your friend was looking at it through the same (25mm?) eyepiece supplied with the scope that she used to observe the Moon.
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