ghost image

[sweepy]

Hi, 

I recently purchased a new pair of binoculars, 8x42 roof prism viking navalux. I was reasonably pleased with them until the first time I used them to look at the moon. There is a hazy ghost image of the moon to the left of the actual moon through the left hand eyepiece. Ive made sure they were clean, and looked through with the other eye to ensure its not me.

Im taking them back on thurs, but looking at anything else you can't see anything wrong, just the moon. What do I tell them is wrong and how do I demonstrate it.

Thank you for your patience with my ignorance

[Kropster]

definitely sounds like something is wrong with the optics.

Looking at a bright light might show the same effect...... but you might need to have a fairly dark background to it.

I think the brightness of the Moon is enabling you to see the faint secondary image that you probably wouldn't notice in normal daylight use.

[ronin]

Chance that there is a problem with the roof prisms. Unlike the porro variety the roof prism binoculars are actually 2 prisms back to back. The alignment of these can cause problems, they can seperate a bit if they get a knock, also overheating etc can cause problems.

Before you haul them back take a look at a light through them, you may then get the same ghost image, that then can be used to demonstrate the problem.

Viking usually produce some excellent binoculars, seem like you have simply had bad luck.

[sweepy]

Ive tried putting a white circle on a black screen on the laptop and can just about see it. Ive had them just over a month but didn't see the problem till I looked at the moon. Lets hope they are reasonable.

[Kropster]

Maybe a torch on the other side of the room might show it.

[sweepy]

Good idea, soon as it gets dark i'm trying that.

[LukeSkywatcher]

You weren't looking at the Moon through a window by any chance?.

[sweepy]

No 

Just been back to the shop and Kropsters idea with the torch worked perfectly. They offered a refund but I decided to upgrade to the vistron model with a bit of a discount.

Thank you all very much for your help