Telescope Eyepieces?
Frizel Asked:
I have a newtonian telescope with focal length 500mm and 114mm diameter. What Telescope eyepieces should i use for best planet observation?
Reply:
To see detail on the planets you need magnification - the more the better. You can calculate the magnification you're getting by dividing the focal length of your 'scope (500mm) by the focal length of your eyepiece. So, if you want a magnification of 100x you'll need an eyepiece with a focal length of 5mm, 200x will need 2.5mm. It would also be close to what your 'sope's theoreticaly capable of - x100 would be much more realistic.
The problem with short focal length telescope eyepieces is that they tend to be uncomfortable to use - you have to get your eye very close to the eyepiece. The distance you can put your eye behind the eyepiece is called the eyerelief. You can get eyepieces that offer acceptable eyerelief even with short focal lengths, but I suspect they cost more than your 'scope. A way round it is to use a barlow lens. These are simple lenses that increase the focal length of the 'scope, so you get more magnification with the same eyepiece.
To be honest, your 'scope isn't the best choice for planetary viewing - it can't support much magnification. If you're just seeing what you can do with it then that's great -you'll see Saturn's rings, some detail on Jupiter etc. If planetary viewing is what you want to get into though I'd consider a new 'scope before I started buying any more telescope eyepieces.
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Subject: New scope with crap eyepieces? – by: Crescent: Hello everyone,
My first telescope arrived a few days ag… http://bit.ly/bg7KoI
There are several things that could potentially be wrong. First is that either the eyepiece or the telescope's objective lens or mirror is dirty. Avoid anything stronger than soapy water when cleaning glass surfaces.
If that doesn't fix it then your telescope's collimation may be off. That's not as easy to correct because it involves re-aligning the mirror (in reflectors and cassegrains) and knowing how to tell when it is spot-on. There is something called a "star test" that can check for collimation. Refractor lenses rarely get knocked out of collimation after the scope has been completely assembled. But they aren't always perfectly aligned to begin with, and once constructed it is horribly difficult to adjust the lens.
It's also possible that your eyepiece is screwed up mechanically; if one of the lenses comes loose or a part falls out then you'll be in trouble. Try another eyepiece to see if it works better.
If none of your eyepieces are able to focus at all and you don't suspect a collimation problem then it may be that your telescope's focal point doesn't occur in the same spot where the eyepiece is put. If the scope is "farsighted" you can attain focus by buying a longer focusing tube that will put the eyepiece further back. If it's "nearsighted" and the focus is inside the telescope tube, then you are pretty much S.O.L.
Your 24mm eyepiece will give you 76x on this telescope, which is a good low power, suitable for viewing open clusters, large galaxies, and large nebulae. To view the planets, you are going to need a much shorter focal length eyepiece. say around 8 mm focal length (228x). Such an eyepiece will also be useful for viewing planetary nebulae and globular clusters.
There are a wide variety of eyepieces available on the market at a variety of prices — generally you get what you pay for. The two leading brands of eyepieces are Tele Vue and Pentax. Tele Vue has several different lines of eyepieces defined by the width of their apparent field of view:
Plössl 50°
Radian: 60°
Panoptic 68°
Nagler 82°
Ethos 100°
In general, the wider the field of view, the more expensive the eyepiece is. An exception is the Radian series and some of the Naglers, which offer longer eye relief than other eyepieces, making them easier to use for people who must wear glasses. You will probably be surprised at how expensive some of these eyepieces are. There is a good reason for this: a wide field eyepiece is more versatile than a narrow field eyepiece, and so one eyepiece serve the function of two or three narrower field eyepieces.
You should choose binoculars
Thank you for this review.
Getting the powertank, tripod, telescope, eyepieces and observing list all ready to go for a few hours of fun tonight at the eyepiece.
Five superior grade Plossl eyepieces, all fully mu…
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Start small and work your way up. You should be able to just drop in each eyepiece and then fine tune the focusing.
As magnification increases, you'll have more trouble locating your target. Vibration in your scope will also be highly magnified. The image will get less bright, too.
It will become painfully obvious if you use a 3x barlow. Magnification is not always your friend.