Problems with 6mm and 9mm eyepieces

[kljucd1 (Daniel)]

Hi,

I bought myself a little kit of lenses, which include 6mm and 9mm lenses. My problem is that when I use either of these, I think it usually happens when also a barlow, I get this strange circle of light that travels through the FOV with the object that I am looking at. This makes it difficult to see the object.

I am not sure if anyone can understand what I am trying to describe, but does anyone know why this happens and how I can fix it?

I have attached a photoshopped version of, sort of, what I see, but cannot take a photo directly as the camera does not see this.

Let me know if you have any ideas.

Thanks

Daniel...

[dannat (Daniel)]

Is what you are looking at still in focus - I understand you are saying you look at something and this extra piece of light ball pops into view? is this correct?

[kljucd1 (Daniel)]

Yep, your description is correct.

I remember the object was never focussed properly when this was happening; I wasn't actually able to get it to focus when this was happening.

Thanks

Daniel...

[dannat (Daniel)]

I am guessing soemthing is wrong with the optics in the barlow or ep -and that you are getting stray light bounced off the oject you are trying to view in another area of the FOv. I would ask the retaier to check it for you if you havn't had it long, or else try a different scope/barlow/ep comination

[AstroRudi]

Hi,

this is a very interesting question ! I am doing astronomy since 35 years and I recently bought a (rather famous) 5 mm eyepeice and I had (for the first time in my life) an effect similar to the one you describe: when looking after bright objects, the background around the object is not black, but takes over a reflection from the bright object and makes the background of (nearly) the whole filed of view "shining".

I tried a lot of thing to avoid this effect of "shining" (I blackened the edges of the eyepiece lenses with a black text marker etc), but it did not have any effect. I believe the thing is called "scattering" or "ghosting", but I have no idea from what it comes in the case of my eyepiece.

I am wondering whether the eyepiece producer is testing new glass sorts !

Clear skies

Rudi

[iceman (Mike)]

Hi Daniel

What objects were you looking at when this happened? Did it happen on all stars or just bright ones?

[okiscopey (Mike)]

Are the lenses all clear when you look through them during the day? How about when you reflect light off the front and rear elements? I'm wondering if it could be internal condensation (esp. if it comes and goes) or a thin film of contamination on one of the lens surfaces. Also, I'm assuming nothing 'rattles' when you shake the eyepieces!

[kljucd1 (Daniel)]

Hi,

Iceman - I have only noticed it when looking at Jupiter. When I first got the lenses I had a quick look at the moon but of course the moon was too bright and so it may have hidden the effect. Most stars are just a bigger dot than they are with the naked eye, so I don't really see any problems with those either.

Okiscopey - First off, I very happy to report that nothing rattles . As for the other suggestions you raise, there is finger prints on them but this is the case on all my lenses. As far as coming and going, I know what you are saying but this effect happens everytime I look at Jupiter.

Maybe I just have dodgy eyes

Thanks for you ideas guys, even if I can't fix the problem I can still learn a bit more from this problem, and you guys.

Daniel...

[Solanum]

When viewing very bright objects like Jupiter I sometimes get some ghosting with certain eyepieces, presumably caused by internal reflections off the elements. I have found that moving my eye back slightly can solve the problem (keeping within the available eye relief). Does your eyepiece have long eye relief?

[kljucd1 (Daniel)]

Hi,

I will have to find out about the eye relief as I am not sure. As we have clear skies today, I will be able to try your suggestion anyway.

Thanks

Daniel...