What's the best Barlow.

[vince 66]

Oh we'll never say never. I've been looking for a 3.5 to 4 mm eyepiece for some time now. Although I like orthos a lot I feel that 4mm may be a bit to tight for me. So I am thinking about barlowing my XW eye pieces. I would buy the 3.5 but it's a lot of money to spend on a eye piece That would only get used once in a while. I used to have a Nagler 3mm to 6mm zoom eye piece but the floaters drove me mad. So will I get as good views with a barlwed XW as I would with a 3.5 XW.

[John]

If you used a 2x Powermate on the 7mm XW the quality of view will be practically the same as the 3.5 XW gives Vince. I've tried it !. The trouble is that the Powermate costs almost as much as the 3.5mm XW. A good and lower cost alternative would be the Explore Scientific 2x Focal Extender. This is a 1.25" device but very like a Powermate in performance terms.

If a 4mm would do the Vixen SLV range offer a very "XW" like experience but with a 50 degree field of view and a price tag of just over £100.

I do have a 3.5mm XW as it happens - I thought I might have bought it from you some time ago ?. Or maybe that was the 5mm ?.

[NGC 1502]

 I used to have a Nagler 3mm to 6mm zoom eye piece but the floaters drove me mad.

I may well be wrong on this, as I'm fortunate in not suffering from floaters in my vision, but I thought they became apparent when using very high power with the resulting tiny exit pupil.

So if you suffered from floaters with the Nagler 3 - 6mm zoom, won't any high power EP do the same ?

Apologies if my understanding about floaters needs updating.

Regards, Ed.

[Stu]

I may well be wrong on this, as I'm fortunate in not suffering from floaters in my vision, but I thought they became apparent when using very high power with the resulting tiny exit pupil.

So if you suffered from floaters with the Nagler 3 - 6mm zoom, won't any high power EP do the same ?

Apologies if my understanding about floaters needs updating.

Regards, Ed.

No Ed, you are completely correct.

As you say, floaters are a result of small exit pupils, they can be an issue starting below 1mm but generally I find them ok on planets down to 0.5mm. Below that in my opinion is only useful for doubles and lunar work.

So, Nag zoom at 3.5mm, 3.5mm XW or 7mm XW powermate will all be the same in terms of floaters. The only way around it is bigger aperture to give high mag with large exit pupil sizes.

In terms of the best barlows, PowerMates are great as they do not degrade the image and maintain eye relief which is good for the longer eye relief eyepieces. For orthos though a barlow can be useful as it allows you to get high mag with more comfortable eyerelief. The Baader VIP barlow is excellent, and very flexible as an option.