Which is better: 5mm, or 10mm+ 2x Barlow?

[Ubik]

I've just bought my first telescope, a Skywatcher Evostar 90, and have used it once, so far I'm very happy with it. I've been reading around and it seems the consensus is that it would be a good idea to upgrade the eyepieces, in particular the 10mm (It came with the standard 10mm and 25mm eyepieces and a 2x "deluxe " Barlow). So I've decided that a Vixen NPL 10mm is the first thing on my shopping list. My question is whether the second thing on the list should be a 5mm eyepiece or a new 2x Barlow (£30-40 budget)? I would guessing that the 5mm is the right choice, on the principle that the more glass that the light has to go through the more light is lost?

[Catweazel]

I would guessing that the 5mm is the right choice, on the principle that the more glass that the light has to go through the more light is lost?

Hi Ubik, generally speaking this is correct. The advantage of barlow lenses, however, is that they double up each EP, so as you say, your 10mm can also be a 5mm with barlow. The other added bonus with barlows, is that the eye relief on higher powered lenses can be quite short, and barlowing a lower powered lens means that you keep the longer eye relief of that lens.

[NGC 1502]

Hi and welcome to SGL.

I think I'd wait a bit and get some more use out of your new scope before buying more eyepieces.

I've googled your scope, looks like a 90mm with 900mm focal length. If you use a 2x barlow with the 10mm eyepiece that will give 180x. You may well find that's pushing the scope too far, whatever the adverts may say.

Perhaps others with the same scope may comment, but I think 130x would be more useful more often.

The Vixens are good eyepieces. But entry level barlows are often a big compromise, personally I'd get a higher power eyepiece rather than a lower priced barlow. Not everyone will agree to that I'm sure, but it's just my opinion.

HTH, Ed.

[Ubik]

NGC 1502- yes it is 90mm by 900mm. I did use the 10mm EP + Barlow on Saturday night (180x mag) and was pretty impressed with the view of Jupiter. But that was the first time I'd ever looked through a proper telescope so I have no frame of reference I suppose. Anyway Vixen NPLs don't come in 5mm, only 6mm, which would give me 150x so maybe that would be better from what you're saying.

Catweazel- how much of an issue is eye relief for a 5 or 6mm EP, given that I don't need glasses?