help w/ telescope lens'?

Question

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

Answer 1

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.

Answer 2

I'm assuming by "10" you mean you have a telescope with a focal ratio of f/10.

Perhaps you have a Meade DS-2070AT?

If so, the focal length of your telescope is 700mm. You should be able to see the rings on Saturn with the 25mm and barlow but the image will be small.

The higher magnification you use, the more difficult it will be to get a clear image. Sometimes there is a lot of turbulence in the atmosphere, even if it seems calm and clear, and on those nights it will be hard to get a good image. Also, if for example you kept your telescope in a heated house all day and then took it out in the cold of night and tried to use it immediately, you might get a poor image.

So wait for a calm night. Let your telescope sit outside for a few hours and then put your 25mm in the focuser and aim it at Saturn. Focus slowly until you get a sharp image. Then you can try it with the barlow.

Answer 3

The 25 mm eyepiece with no barlow is the lowest magnification.
The *smaller* the number the greater the magnification is. The barlow makes the eyepiece you put in 2 times smaller (more magnification).

You should see Saturn near Regulus, it rises in the east in the evening. If you're not seeing anything you're probably looking at Regulus, a star, which has no detail.

Are you observing from a roof or a field? Well try to position yourself so that the chimneys and roads and buildings are further and not directly under. They make heat that makes everything blurry.

Wait until the planet rises higher too. At least 30º is good.

Always go from low power up to high power, and stop when you don't like the view anymore (too blurry). But sometimes if you wait awhile, it will pop into clearer view for just a second.

Also, don't go on a night with alot of twinkling in the stars, those nights are bad nights for looking at planets.

Now and next two months Saturn is near opposition, and closer than during the rest of the year.

Answer 4

The 9mm should give the most magnification. Saturn is a long way for a small telescope. You're unlikely to see the rings that clearly but that will depend where you are on earth.... The focuser will need to be adjusted to your eyesight and will be related to the distance of the object. I suggest you focus on a star and then turn to Saturn.

Answer 5

The answers above are great, so pay close attention to them. One other point, too: when you "up" the magnification, you magnify *everything*. So, if the atmosphere is unsteady, especially very high up, you will magnify that unsteadiness as well.

So, you may have to try several night running to get a clear *and* steady view.

Seeing the rings should be no problem. You target should be Cassini's Division. That will be at the very limit for your telescope and a real test for your eye, too!

Go for it!

HTH

Charles

Answer 6

maximum barlows slide into the focuser tube and also you insert the eyepiece interior the barlow, yet there are different configurations. interior the barlow, insert the bottom powered eyepiece you've. Then slowly turn the focusing knobs until eventually the picture is sharp. Barlows in reality strengthen the magnification so extra commonly than not you should zoom out to concentration.