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telescope eyepeices?

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A few people have said now that the max magnification is not so true.

I have these pieces




barlow lens

What combination of these will give me the best magnification to see for example saturn? and which will give me the best to see star clusters etc. I dont want to be putting things together if its not as good as it should be. Apreciate the help guys

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It all depends what scope you have. Generally I would say that your barlow lens (I'm assuming it's a 2x one) will work well with your 20mm and 12.5 mm eyepieces but using it with the 4mm will not work well as the power would be likely to be too much for any scope. So using the barlow lens in this way will give you the equivilent of 20mm, 12.5mm, 10mm, 6.25mm and 4mm eyepieces which is a good range in most scopes.

Star clusters are usuallly best at low to medium power (eg: 20mm, 12.5mm) wheras Saturn can stand some magnfication so the 6.25mm and even the 4mm could come in handy there.

Many folk new to the hobby rush into high magnfications thinking that these give the best views which is a mistake. A telescope is, in my opinion, firstly a light gathering tool (hence the obsession here about the size or aperture of your main mirror of lens). Magnfication is used to examine the collected image more closely but too much magnfication is not a good thing.


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Mitchell, it's worth bearing in mind, that you will be able to see Saturn (ok it'll be very very small) using the 20mm ep. You can just about make out the rings in a pair of 10x50 binoculars, same with the moons of Jupiter. Best bet is to start with the low magnification eyepiece, then work up, gradually increasing the magnification. See what gives the best, least wobbly view (this will probably change from night to night), if you go beyond that, the view will just detiorate.

As an example, I did try to view Saturn in my ST80 with a 5mm ep, and a 5x Barlow (400x mag, the scope is an 80mm). The view was rubbish, but Saturn filled the FOV completely. In a singular brief instant I got the impression that the view was 3D before it mushed out.

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Can you post your scope details?

There are however some rules of thumb which may help you.

1 The maximum useful amount of magnification is about 50x the scope's aperture in inches. So if your scope is say 4", the max useful mag is around 200x

2 However, in the UK we are not blessed with the best viewing conditions and if you can achieve good visuals above about 250x you've done well

... and to ensure that you can calculate the magnification correctly, it's the focal length of your scope eg 1000mm divided by the focal length of the EP eg 20mm (with any adjustment of the EP's focal length when using your barlow) This isn't a rule of thumb, it's a formula

... and just as Doc says, have an experiment!

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my scope is 3" reflector so i guess i can achieve 150, i try my 4mm with the barlow but the focus is no good. what i dont get is i could use my 4mm and get 175 * or use a 12.5 mm with the barlow 3* to get 168. is it better to not use the barlow.. gosh i hate being nooby spose its the fun in learning thanks

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OK, here's' the news. Your 76mm 700mm f/l scope isn't a bad size. Your eps are probably, but not necessarily, Huygens or Ramsden (marked with a 'H' or 'SR' along with the length. If the eyepieces are marked with a 'K' or a 'P', they are better quality Kellners or Plossls. If you measure across the bottom of the ep, and it has a diameter of 1 1/4", that is a good thing.

If the eyepieces have a diameter of slightly less than an inch, see if there is an insert in the focuser that can be removed to allow insertion of a 1 1/4" ep. This will be usefull later.

If the Barlow is of the smaller size, and plastic, carefully drill a largish hole just behind the glass, and drill some smaller holes further down the tube, and see if you can play piccolo tunes on it, as it's useless for astronomy. In any case, put the Barlow and the 4mm ep in your sock drawer, as you won't be using them again.

It sounds like you only have the 12.5mm ep, though these sets typically come with a 20 or 25mm ep as well. If that's all you've got, that's all you've got. Use the 12.5, and its 56x magnification. You can see a lot with this power. I recommend the Orion nebula, the Beehive and the Pleiades, and the Moon and Saturn just now.

If that 12.5mm ep is a Kellner or Plossl, and 1 1/4" then it's a good start. If it is 1 1/4" you can equip yourself with a few inexpensive PLossls, and improve your viewing experience immensely. If it is neither, and you can insert a 1 1/4" ep in the focuser, you can still cheaply and easily build a working set of eps.

You don't need a lot, but I would suggest eps of about 12 and 32mm, and a decent 2x Barlow. This would give you magnifications of 22, 44, 58 and 116 which is a very useful set well suited to the capabilities of your scope. This would cost me less than $100, so shouldn't be much even in t'UK.

To answer your question above, the reason they put a 4mm ep and a 3x Barlow in the box was to support the ludicrous claim that they can achieve 525 power with your scope. Technically, they can, but the view isn't worth much. So, yes, it is better not to use the Barlow, or the 4mm.

The good news is that for a few pounds more, you can get much enjoyment out of your scope.

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If the Barlow is of the smaller size, and plastic, carefully drill a largish hole just behind the glass, and drill some smaller holes further down the tube, and see if you can play piccolo tunes on it, as it's useless for astronomy.

Ha ha hah hah ah ah ha! That made me spit cereal all over my laptop.


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well i have got 28 days to take this tscope back, maybe i will use it untill then and see what i can get and maybe i can buy a better one once i have pushed this one to its limits lol. ok cheers damn i no what you mean whenever i use the barlow or the 4mm or even together you cant focus in... is there any telescopes that do what they say? what do you guys think of this ??

Celestron Powerseeker 127EQ.

might try this as it is also covered by a 28 day return policy so i can take it back if its a bag of balls, its also within my price range. cheers guys

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Mitchel, give Steve at FLO a call. He's got good scopes. For the sort of money of the powerseeker 127, you can get a 150mm Dob. The movement will be a lot easier, you will get a really good scope (so everyone says, although i've never used a reflector :)). The other option would be the 130pm, same sort of aperture sa the powerseeker, but again, you know exactly what you'll get, and lots of people started with the 130pm and still use them (it has a motor for tracking the sky too).

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