help w/ telescope lens'?
I just got my first telescope its a Meade with a 2.8 inch aperature. It came with the following lens': 25mm, a 9mm, and a 2x Barlow.
I know the barlow lens doubles the smaller lens' magnifying power. I would like to know which lens can see the furthest. I have been using the 25 and the barlow together and don't know how far I can zoom in to see say Saturn. I don't know how well I will be able to see this planet. Will it be fuzzy or with my scope will it only be a shining mass in the mirror. Oh my telescope is a refractor. I just want to see the rings of Saturn, if the focuser is all the way out will it be clearer or not?
Oh thanks I have a focal length of 10
Magnification is focal length of the objective divided by focal length of the eyepiece. The Barlow basically increases the focal length of the objective by the specified factor (2x in your case). So you need to know the focal length of your objective. If it isn't in your manual you can get a rough number by just measuring how long the telescope is.
If you have the Meade 70AZ-AR, as shown in the source, then the focal length is 700 mm. So the 25 mm eyepiece gives 700/25= 28 power and the 9mm gives 700/9= 78 power. With the Barlow you get double the power, or 56 and 156.
By the way, magnification has nothing to do with how far you can see, only how big something appears. It isn't the same thing at all. Also, any magnification higher than 50 times the objective lens diameter in inches (50 * 2.8 = 140 in your case) is useless, so the 156 you get with the 9mm and Barlow is really pushing the limit; I suspect you will rarely use it.
The 78 power you get with the 9 mm eyepiece alone is more than enough power to see the rings of Saturn. It will look small, but you will see the rings clearly. You move the focuser to whatever position makes the image clear. That is what it is for, not for zooming in. To "zoom in" you just change eyepieces. There are some zoom eyepieces made, but you don't have one, so you just select one of the 4 possible combinations to get the magnification you want.
25 mm = 28x
25 mm + Barlow = 56x
9 mm = 78x
9 mm + Barlow = 156x
To find the location of Saturn in the sky, try the second source. Saturn is easily seen as a bright star in the sky without using any telescope, just your eyes. When you know which star is Saturn, point your telescope at it using the lowest power (28). Once it is in the field of view, carefully, without moving the telescope at all, change to a higher power eyepiece. You will probably have to re-focus after changing eyepieces. I suggest the 9mm, 78 power one for the best view of Saturn. Your telescope is really too small to get a sharp, crisp looking image at 156 power, but you can try it anyway if you like.
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