12mm and 6mm EP or 12mm EP with 2x Barlow

[RJC]

Hi All,

is there any difference in quality between a 6mm BST StarGuider, or a 12mm BST SG with a SG 2x Barlow?

Thanks

[Ricochet]

There is no 6mm Starguider, but there is a 5mm. The 5, 8 and 12mm Starguiders are well corrected even in fast scopes whilst the longest focal lengths are best used in slow telescopes. This means that in the specific case of the 5mm Starguider vs the 12mm Starguider + Barlow there will be very little difference between them. However, as a general rule if you are using a fast telescope and cheaper eyepieces then adding a Barlow can often improve the correction of the eyepiece. 

I would choose a 5 and 12 over a 12 and Barlow as the eyepieces will be more parfocal, but if you were buying three items then there would be a good argument to buy 8, 12 and a Barlow so that you effectively have 4, 6, 8, 12 instead of buying 5, 8, 12, assuming that 4/5/6mm focal lengths are suitable for the telescope you will be using them with. 

[vlaiv]

I would use 12mm plossl + barlow over 6mm plossl, but if I were to choose between 6mm eyepiece with decent eye relief - I always prefer less glass and simpler setup (no need to handle additional piece of equipment like barlow).

[RJC]

Thanks all, great advice!

[PeterStudz]

I have 12mm & 5mm BST StarGuiders. I’ve used them extensively over the last 3 years, often for the planets and lunar with a Skywatcher 200p Dob. As far as colour contrast goes (obviously important for planetary) the 12mm + x2 BST barlow is slightly better than the 5mm. Quite obvious on Jupiter and when I was observing Mars. 

[Second Time Around]

I'd use the 12mm plus a Barlow.  Some Barlows are dual 1.5x/2x giving 12mm, 8mm and 6mm focal lengths.

Go to https://www.firstlightoptics.com/barlows/astro-essentials-125-2x-barlow-with-t-thread.html

Edited January 9 by Second Time Around