Help Me Out (Eyepieces)

[Heavygun1450]

Hi,

This whole summer I have been watching the planets with my binoculars. Recently I found a old telescope in my family members garage. Its in ok shape, but problem is its missing the eyepieces. Its a Celestron Powerseeker #21055 Refractor 60mm Aperture 700mm Focal Length. The barrel size is 1.25 in. I want something cheap to get me into astronomy! As for what I want the eyepieces for, I want to look at Mars, Saturn, Jupiter, Venus, Mercury, planets only because its such a small aperture. I do not want to spend too much on the eyepieces, just something to get me started. I know the telescope isn't much of a performer, but it should do. So I would expect probably a 6mm or so focal length with a 2x barlow for planets. If anybody could link me to the apporpriate eyepieces it would help me out alot, as its very confusing for me getting into this specifically if im not sure im getting a appropriate or quality eyepiece for what im doing. Thanks help a new guy out

[Putaendo Patrick]

The maximum magnification of a telescope can be roughly calculated by doubling the aperture in millimeters, in your case about x120. A 6mm EP will achieve this, but there is little point in trying to push this upward with a Barlow - the deterioration of viewing quality will defeat the benefits of higher magnification. You should get nice views of the planets, but without very much detail.

A Barlow could extend your range of magnifications. For example 20mm and 12mm EPs with a x2 Barlow would effectively add 10mm and 6mm.

Lower power EPs are often less demanding and you may be able to find a cheap secondhand 20mm or 25mm from someone upgrading the supplied EPs which came with their telescope. Very cheap higher magnification EPs are generally much poorer in quality. I would suggest getting a Plossl design EP which will cost about 25 pounds - Celestron Omni, Skywatcher SP or Revelation are possible options.

However, a problem with higher power Plossls is that they have very short eye relief (your eyeball needs to be very close to the glass). A 12mm Plossl used with a Barlow will give you the 6mm but with a little more eye relief which you may find more comfortable.

[Ruud]

Hello, welcome,

your telescope has an aperture of 60 mm. That means magnifications up to 2 x 60 = 120 times are feasible with it. If you go higher the image will get bigger, but you will not see more detail: the image will also get blurrier and darker. On many nights the atmosphere will allow a magnification of 120x, so you are in luck. Another fortunate circumstance is that your telescope has a focal ratio of 11.7 (700/60), which means that most eyepieces will work just fine in it. 

The focal length of the telescope is 700mm. The magnification you will get from any given eyepiece is 700 / (focal length of eyepiece).

Maximum magnification: a 6 mm eyepiece will give 117x, a 5 mm eyepiece will give 140x (a bit much, but probably still usable on the Moon). With a 2x Barlow (I think you will want a 'shorty', it will sit better in the diagonal) you get the same magnifications from 12 mm and 10 mm eyepieces respectively.

Lowest magnification: a 32 mm 50° eyepiece will give you the largest true field you can get using a 1.25" diagonal. Magnification will be  700/32 = 22x, the true field of view will be about 50° / 22 = 2.3° of sky.

Plössl eyepieces have an apparent field of view of about 50° and are good budget eyepieces. I recommend a 12mm and a 32mm Plössl with a 2x Barlow. Your magnifications will be 22x, 44x, 58x and 117x.

Under 10mm, Plössls have such a short eye relief that they are uncomfortable to use. If you must wear glasses because of astigmatism, even a 12mm Plössl may have too little eye relief. In that case, an alternative 12mm would be better.

Others will know the brand names of recommendable budget eyepieces in your location. For Plössls, GSO, with a 52° view, is a decent brand.

<Edit: I notice that I unintentionally repeated most of Patrick's answer. We must have posted at about the same time.>

[Alan64]

Choose the 32mm(22x), to help you find the objects you want to observe, then ramp up the magnification accordingly: 20mm(35x), 12.5mm(56x), 7.5mm(93x)...

http://www.rothervalleyoptics.co.uk/antares-plossl-eyepieces-125.html

You're going to want the cheapest barlow you can find, but if you do, the views will be cheapened, so go ahead and splash... http://www.rothervalleyoptics.co.uk/antares-x2-twist-lock-barlow-lens-125.html

You'll never need another one, and as you go from telescope to telescope in future.  Most if not all beginners are under mistaken belief that it's just a barlow, and need not be as good as the eyepieces. 

Nothing could be further from the truth.

[Timebandit]

Hello and welcome to SGL.

I would not get the barlow and spend the money instead on a decent eyepiece. For the money the BST Starguider seem to get good reviews and a strong following, so worth looking at. When it comes to magnification I would go for a 6mm for planets. As the scope aperture ratio limits the magnification eyepiece that you can go to.  Don't make the mistake of trying to push past around the 120x mark otherwise you will just get a blurry poor image.

The best magnification is not how high you can get your scope to go ,but the most detail you can get from the correct eyepiece for your given scope and seeing conditions.

   As with planets to get the most detail it also helps considerably observing from a dark site, this way you can get the most out of your chosen aperture.

 I hope the above helps☺