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Advice for a Sky-Watcher owner


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Hi All, Please can you advise me please. I have a Sky-watcher telescope. D90mm F1250mm with a "super 25 Wide Angle long eye relief". I'm new to equipment and I am currently looking for a selection of lens. Thinking of a Plossl lens but unsure of which size. Any recommendations please. Thank you ............Go STS134 !!!!!!!!!!!!:eek:

Edited by cuzzer
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Hi Cuzzer, let's see if I can help a bit...

Generally, the larger the focal length of an eyepiece, the lower the magnification and wider the view you will have. A 32-40mm lens is great for wide angle views and will give bright images that help you see faint, deep sky objects like nebulae and galaxies.

The smaller the focal length, the larger the magnification, so smaller eyepieces such as 15mm, 10mm, 5mm will be better for splitting double stars, seeing Saturn (and other planets!) and they are excellent for Luna. You can find magnification by dividing your scope's focal length (1250mm) by the eyepiece focal length (for instance: 1250 / 25mm = 50x and so on...)

Another option for you is a barlow lens - this attaches between the eyepiece and the scope, usually doubling the magnification. This can make a 25mm perform like a 12mm and effectively double your eyepiece collection -- as long as your eyepieces are not exact multiples of each other. For instance, if you have a 20mm lens, a 10mm lens, a 2x barlow would be pointless!

Plossl lenses are excellent for a beginner, by the way. Wide field of view, pretty sharp out to the edges, and quite affordable. (you can break the bank on fancy eyepieces!) Even the 'bargain' plossls commonly available now are loads better than the old Kellners and stuff that was available 15 years ago, so you can't go too wrong there.

I might also consider a moon filter (about $15 or so) it will help loads when looking at the very bright moon. You might also consider a red LED torch and a star map. If you haven't downloaded Stellarium yet, click <HERE>, it is a free program and will help loads when you want to know what is in the sky tonight.

I hope that helps some,

Dan

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