Maxbright Internal Reflections
Posted 03 April 2013 - 06:33 PM
I've been loving my Baader Maxbrights, and all the advantages of using two eyes. However, I've noticed that on some bright objects, as I move the telescope, I see angled reflections on both sides of the view. I've checked to see where these reflections are coming from and they're simply direct reflections coming from the prisms just adjacent to the opening on the telescope side. Is this normal? I can't imagine that this is due to miscollimation - to correct for this, the prisms would have to more fairly far. Perhaps I need to use eyepieces that have rear lenses located far down enough in their housing to avoid these reflections? Is this normal? Does anyone here have experience with this??
Posted 03 April 2013 - 07:23 PM
Posted 04 April 2013 - 01:09 AM
Anyway I just purchased a Siebert Black Night BN25 binoviewers so I will be able to compare...
It seems to be a well-known issue with these entry-level chinese binoviewers.
Posted 04 April 2013 - 02:35 PM
The rear lens of every eyepiece is different, and I think catch these reflections differently.
Could anyone here suggest a bino pair that doesn't have this issue?
Posted 04 April 2013 - 04:22 PM
I should expect these reflections to be a bit more clipped on long focal length scopes, due to the angularly smaller objective (as 'seen'' from the BV) effectively narrowing the light source. Compare the BV-alone aspect with that on a fast scope and then a slow scope, then report back.
What you see here you see in miniature as the exit pupil, flanked by the same pair of scaled down reflections. If your eye's iris is large enough (and with BVs it usually is), it will take in the whole lot, leading to the perception of ghost images from bright objects outside the FOV crossing the view as you pan about. If the exit pupil is about equal to or larger than your iris, you only experience the ghost images if you iris is offset so as to take in the flanking 'fingernail' of what are in essence highly clipped, off-axis ghost exit pupils.
Posted 04 April 2013 - 05:24 PM
Posted 04 April 2013 - 08:51 PM
I don't have a binoviewer, and so you're in a much better position to explore the envelope.
Posted 05 April 2013 - 06:30 AM
Posted 05 April 2013 - 10:04 AM
I wonder if it might also block some of the reflections from the prisms you're seeing? And I wonder if adding a disk like that is a modification that one could make on certain lenses to minimize or eliminate such reflections? I don't know, though, what the effect of adding such a disk has on blocking the light cone and then possibly lowering light transmission as a result. That's something else which is discussed in that thread.
Posted 05 April 2013 - 11:11 AM
Posted 06 April 2013 - 06:26 PM
i saw it in my pair of WO binos, machining really good prisms would be expensive -on god binoculars i see they make an etch in the prism to prevent the reflections
Posted 06 April 2013 - 08:30 PM
So I've been able to adjust the eyepiece holders so the image circles align better but I've found that baffling the for eyepieces isn't as easy as I first thought, without reducing the fov. Curious about notching the prisms - will see what Harry thinks, curious if this is cost effective...