Foggy and blurry finderscope

Sconesbie (Scott) · #1 30-03-2015, 10:34 AM

As I mentioned before on another post, my finderscope is a bit cloudy. I can see images through it but surrounding these things (moon, stars, Jupiter and so on), everything looks blurry. I don't think it is fogging up as I can see the centre image ok and can make out the centre cross (the wires).

I have pulled it apart (only the parts that can be unscrewed) and left it over night to dry out as I thought it may have some condensation. Hoping this would fix it as I don't want any thing growing. The finderscope is on a 10" collapsible dob.

Is there a way I can soak it in something like dishwashing liquid or hot soapy water and clean it and leave it to dry naturally?

Physically, I can't see anything else to cause this.

MattT · #2 30-03-2015, 12:46 PM

Hi Scott,
When you say blurry do you mean out of focus or misty? Or both?
I have a GSO finder that was like that. In focus but foggy. The foggy bit came from the eyepiece part so I pulled that apart cleaned it up like I would with cleaning eyepieces and put it back together….like new. I made sure it went back in the order the lenses came out. Pretty simple really.

It could be someone has pulled apart the objective and put it in back to front??? I don't know if the 50mm finders have an air spaced doublet or cemented one, so one or both lenses might be the wrong way round.

Have a look and see, just remember what went where.

Matt

rustigsmed (Russell) · #3 30-03-2015, 02:04 PM

yes my GSO finder was the same as Matt's - the focus was adjustable.

Sconesbie (Scott) · #4 30-03-2015, 03:49 PM

It just happened really. It wouldn't be due to being assembled the wrong way as I have not had it apart before noticing it. In saying that, it can only go back together one way I think. There isn't a way I can put it back together back to front.

One day it was fine then the next, it happened. The view of a star through the finderscope for example is fine but right around the edge of it, is blurry or cloudy. It's like my eyes are playing up or something but it is definately the finderscope. It also makes calibrating the target with the eyepiece a little more difficult.

I can't physically see anything that would make it blurry and there is no growth or dust on any part. That's why I was wondering if I wash it or soak it in a solution of some description, would that help kill anything or clean it?

Regards
Scott

MattT · #5 30-03-2015, 05:25 PM

Ahh you mean at the edge of the field of view the stars are not sharp as they are in the centre, is that right?
If that is there is nothing wrong....as far as I can say...but it's you that have noticed. Just means your getting to be a better observer!

GSO finders are worse on the fuzzy edge than the Skywatcher finders in my experience.

Sconesbie (Scott) · #6 30-03-2015, 05:30 PM

Yes, that's right. The centre is ok with the object in the middle but around it is a bit foggy. The eye piece of the scope is ok, no problem there. Just the finderscope.

The other thing is Orion for example, the three stars in a row (the belt?) are clear but each one has a bit of fog around it.

Maybe it is because I just noticed it.

raymo · #7 30-03-2015, 11:26 PM

It might sound silly, but if it happened just like that, it's unlikely that
there is anything much wrong with the finder. If it was just the last time you used it, maybe the seeing was very bad. It's not unusual to see stars
immersed in mist when conditions are poor.
raymo

Renato1 (Renato) · #8 06-04-2015, 03:54 PM

If you have stars at the centre sharp, and they are out of focus at the edges - then you have a cheap lousy finderscope. Use it during daytime and you should see the same effect. I have a hopeless Seben one which sounds to be just like yours, if not worse.

It may still be useful for finding brighter objects, but the best course of action is to buy a better quality finderscope.
Regards,
Renato