Barlow or eyepiece

[Din]

Hi all

Just acquired my first telescope, a SW Evostar 150. I've managed to use it once when the weather cleared briefly and was treated to an excellent view of Jupiter and three moons. The scope came with 2 eyepieces, 10 mm and 25 mm. With the 10 mm I was able to enjoy 120 x magnification.

I would like to push the magnification higher and the blurb tells me 300 x is the maximum.

I think I could either go with a 3 x Barlow or a 4 mm eyepiece. Correct me if I'm wrong but the Barlow should give me 360 x mag when used with the 10 mm and a 4 mm eyepiece should give 300 x mag. (1200 mm focal length).

Are there any problems pushing the mag beyond the recommended? Does the use of a Barlow degrade the image at all? Are there any eyepiece manufacturers to avoid? Seems to be a huge range of prices.

Cheers

Ed

[Astro Imp]

For viewing Jupiter it is seldom possible to push the magnification above about 180x because of the unsteady atmosphere, it will be very unusual to get any advantage in viewing planets at 300x. The aim is to get the maximum contrast along with a clear sharp image.

[Din]

Thanks for that Alan. Are there any instances when going above 180x is worthwhile?

Ed

[John]

Thanks for that Alan. Are there any instances when going above 180x is worthwhile?

Ed

The moon and binary stars can benefit from higher magnifications.

I've owned a few Evostar 150's and they do seem to top out at around 180x - 200x in their standard form.

[cantab]

Are there any problems pushing the mag beyond the recommended?

The image won't come to a sharp focus and will be dimmer. You'll have a smaller field of view, faster movement of objects with an undriven mount, and worse vibration, all for no benefit. That said I've observed at 175x in my small refractor - but only because it's a cheap scope and I lack a more appropriate high-power eyepiece for it.

Does the use of a Barlow degrade the image at all?

A good one won't, but a bad one certainly can. I don't think your scope particularly needs one though, they're most useful for short focal ratio ("fast") scopes where you'd otherwise need a very short focal length eyepiece for high power.

Are there any eyepiece manufacturers to avoid?

I think most of the major brands are decent. It's off-branded stuff on eBay you want to be a bit wary of, do your research before buying. The price range is as much as anything else down to the array of designs.

[Din]

Thanks for the advice.

I think I will try a 6mm eyepiece. 200x may be ok on the HEQ5 mount.

I will avoid eBay.

Cheers

Ed

[Angus Wright]

My first scope was a Vixen 102mm achromatic refractor on a GP mount. The 50x per inch rule meant 200x max. I bought a 4mm eyepiece that gave 250x as an experiment, it was a cheap eyepiece. Only once did I see more with the 4mm that the 5mm (200x) the scope came with and presume the atmospheric seeing was the crucial factor. On a night with cracking seeing you should get 300x from your scope, but those nights are few and far between.

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[jabberwocky]

Don't avoid eBay, there are some great deals on eBay, if you can find them. I've bought televue eyepieces on there at 60-70% of new price. Always know what you want though, as said above dont be tempted by Non branded stuff. Decide what you want and then search for it on eBay,