Bright dot in my eyepiece

[journeyguy]

Hi,

Just bought a new eyepiece and gave it a try out. I noticed a single bright dot that flew around the view erratically. At first I thought it may be a fly or something in the scope but when I looked there was nothing there. I thought I'd try again the next night and the same thing happened. I tried it with my factory eyepiece the one that came with the scope and it wasn't there.

Does this sound like a faulty eyepiece? Has anyone else experience something similar?

Thanks,

guy

[Oblong]

I've had something similar when looking at bright objects (planets) at higher magnifications - it seemed to be something in my eye, or possibly a ghost reflection off my eye (i.e. reflecting off mutliple surfaces, one of which was the eye). By performing some frantic blinking, and making sure my eye was at the correct distance it sorted itself out. Another possibility, particularly for eyepieces with generous eye relief, is scattered light from a source off to the side. A bit of judicious playing with the rubber eyecup can help.

[Stargazer_00]

It's the reflection of whatever you are looking at reflecting off of your eyeball back onto the eyepiece I think.

[Dave 2112]

I've had the same thing happen, thought it was a fly or something in the scope at first. Playing around with lenses for a bit and I twigged it only happens with one particular lens, and not all the time, only when looking at something bright.

[Stargazer_00]

I'm Quite sure it's whati said. Although I don't know what the experts value that issue

[journeyguy]

It's the reflection of whatever you are looking at reflecting off of your eyeball back onto the eyepiece I think.

Now this would make a lot of sense as it seemed to happen most when looking at Jupiter. So I can take this as a general occurrence and not as an EP fault then...

Still quite annoying and didn't seem to experience it with my other eyepiece. Hmmmm.

[John]

I've seen a similar effect in some eyepieces but not all types. It is annoying though.

Can I ask which eyepiece shows this effect and which don't ?

[paul mc c]

I had this when using a 25mm TMB eyepiece,very annoying,it looked like a reflection on the inside of the lens coming off what i was looking at.

[journeyguy]

I'm getting it with the Starguider 8mm BST explorer. It is very distracting...

[John]

Have you tried twisting the top of the eyepiece upwards, away from the eye lens of the eyepiece ?. You may be able to find a position where this bright spot is not visible or at least reduced.

[journeyguy]

Have you tried twisting the top of the eyepiece upwards, away from the eye lens of the eyepiece ?. You may be able to find a position where this bright spot is not visible or at least reduced.

Yes is that a fine focuser? I will give it a go tomorrow with an optimistic view on a clear night. Thanks for getting back

[ronin]

It is not a focuser, the cap should be up if you view without glasses, it is to get the eye at the right position. You may find it more comfortable fully up or not quite fully up.

Have read of this with some people cannot recall if it is getting the eye at the right place or if it concerns the exit pupil size.

[E621Keith]

It's reflection off your eye. You see it when you observe very bright object like Jupiter.

It affects some eyepiece more than others. I've seen it in Vixen LVW and it's particularly bad in Nikon NAV-SW if the eye position is not right (no glasses, eye cup not extended).

[chiltonstar]

I have it in a couple of wide-field eyepieces, but not in my older Plossls;; as stated, it's a reflection off the surface of the eye. If you have enough eye relief, I find it disappears if you look at a slight angle into the EP.

Another solution might be to get your eyeball anti-reflection coated with a dielectric film......

Chris

[Stargazer_00]

The dancing of the light is the movement of your eye. It's amazing how much your eye moves without you realising it.

[E621Keith]

...

Another solution might be to get your eyeball anti-reflection coated with a dielectric film......

...

Might well get the lens re-figured and replaced by ED while you are at it. The eye is a poorly grown achromatic doublet with just about every optical aberration in the book.

[Stargazer_00]

i had mine deconstructed, reshaped with lasers to correct astigmatism introduced by the lens and then reassembled.

Worked pretty well, only a bit more than a paracorr mk 2 as well!

[Dave 2112]

I'm getting it with the Starguider 8mm BST explorer. It is very distracting...

Same here. I get it in my 8mm BST and its the only eyepiece it happens in for me.

[Stargazer_00]

It's not really a property of the eyepiece in my experience. I've seen it come and go on different eyepieces. I look at jupiter alot and have noticed this before but it's not a common feature. It seems to be certain positions of eyeball and eyepiece rather than a fault in the coatings etc.