I'm with Nicko on this one here .I think the more glass the light has to go through the more degraded the image is . Simple physics . I will not use a Barlow on close doubles . In fact if my main intention is just to get the split I use eyepieces with as few elements of glass as I can get .Simply concentrating on the very center of the FOV .At this point I do not care what the edges of the image look like . But if I'm just enjoying some "old friends" and the surrounding star field I often use a 20mm Meade research grade and Televue 2x .Striking would be the word .