2x Barlow (not a shorty) question

I have a couple Barlows of the short type. When used with a astrovideo camera, the camera picks up some internal reflections. Folks tell me that the regular length Barlows have much less likelihood of stray light getting down the longer light path. I don't have any experience with the longer type. If it's a major manufacturer product, are the longer Barlows about the same in performance or can anyone recommend something they prefer?

Roland Beard said:

I have a couple Barlows of the short type. When used with a astrovideo camera, the camera picks up some internal reflections. Folks tell me that the regular length Barlows have much less likelihood of stray light getting down the longer light path. I don't have any experience with the longer type. If it's a major manufacturer product, are the longer Barlows about the same in performance or can anyone recommend something they prefer?

I don't think there's any guaranteed difference between short and long vis-a-vis reflections. Certainly I've never had a problem with my Shorty. But it is decently blackened internally.

You can fashion a tube liner from black felt or construction paper, (roll it up, tape together & slip it in) to eliminate sidewall reflections. You can also remove lens from cell & blacken the sides of lens itself with a felt-tip permanent marker to further address stray light if the lens is not already edge-blackened. This works well for visual use, too.

It may not be light from the sides of the Barlow. I've experienced ghost reflections with Barlow use because light is reflected off the surface of the field lens and back to the Barlow. It all has to do with the curves of the specific lenses and the distance they are separated. You can't change the curve on the camera lens but changing the spacing by using a longer Barlow may very well put reflections far enough out of focus that they can't be detected.

dan