8MM or 5MM for first (real) lens

[Jason Garrett]

Hey Ladies and Gents,

Today my Fiancée received my lens in the post for an early birthday present, however I remembered I wanted the 5MM, but I'm contemplating whether to exchange it for the 5MM.

Telescope Focal Length = 650MM, it's a Celestron 130eq.

6" Aperture

Is it worth the extra magnification? I can always get the 5MM at a later date, I'm just eager to get out in it with this new lens because the ones they send with the telescope are Rubbish!

Oh the lens is a BST Explorer

Thanks.

[c3po]

Hi Jason, the 8mm ep will give you a rough mag of about 82x (scope focal length divided by EP focal length... So 650mm / 8mm). The smallest I've used on my 130eq is 6mm, giving about 108x, plenty for planetary viewing in good seeing.

If you want any higher mag, simply slot in a good Barlow and you're away! in fact, my 6mm hardly gets used unless I'm viewing planetary targets, generally I'm using my larger EP's for DSO hunting. if any thing, my 12mm ep is the most used of my smaller eps and the 32mm is most used overall without question.

personally, I'd stick with the 8mm and go from there, the chances of seeing conditions to use a 5mm in the UK are slim.

[Jason Garrett]

Alright thanks a lot c3po, will do, I was considering the fact we live in miserable UK also lol, however it doesn't seem to be the case today it's scorching!

Thanks again!

[Sirius Bizness]

The 8mm BST is a brilliant EP. Also works well with a Barlow for high mag planetary/lunar. Keep it.

[c3po]

The 8mm BST is a brilliant EP. Also works well with a Barlow for high mag planetary/lunar. Keep it.

talking about barlows, the Tal range (2x and 3x) are simply the best for the money, few places ever have stock as they're so sought after, but i sourced mine from FLO and got lucky!

[John]

Your 5.1" scope should be able to handle the 130x that a 5mm eyepiece gives without a problem. If it's in decent collimation and properly cooled even 180x would be fine on a decent night. Just as well as the planets don't really get interesting until you can get 150x or more on them, in my opinion.

That said, the 8mm BST will make a very nice medium power eyepiece (81x) - good for globular clusters and planetary nebulae. You could always get a decent barlow to get higher powers although a decent one will cost you almost as much as another BST eyepiece.

[nightfisher]

The BST`s are great eyepiece`s, stick with it and add the 5mm at a later date

[faulksy]

i have a nice 8mm celestron x-l in the for sale section but you can have it for £30 inc p+p