Help! Need experienced opinion on 2nd hand EP just bought..

[vvsloan]

Hi there people,

I wonder if some one can give me an opinion on a 2nd hand EP I've just bought to go with our brand new boxed 200P Dob (which wont be opened or tried out until Xmas, if for nothing else, to aid with secure transport to the house we will be driving it to to..)..

This whole thing being a gift for somebody else, and me never having previously owned a telescope, I havnt ever seen an EP before, so am not sure what is normal to see on the lens/glass or not. Basically, I got very greedy with regards to extras and decided I wanted an 8mm BST as my mother would never be able to afford an EP herself in the near future, and her B'day isnt until next Xmas, so I thought I would break the bank and throw one into her Xmas bundle. Anyway, I bought a 2nd hand one from a guy on AstroBuySell, and during the correspondence, I was at pains to stress that we really needed the lens to be in perfect condition as a brand new one only cost £15 more. He mailed back saying he thought it was fine and he's just cleaned it with fluid to be sure. Now, that evening I sat down for a read of Turn Left at Orion, which in a section about EP's stressed over and over that you should never, ever under any circumstance clean the lens. Even with so called Lens cleaner as it would invariably damage the lens or at least degrade the blue anti-reflection coating. The EP arrived this morning and when I take the caps off there appears to be green/cloudy streak accross the glass, visible at both ends, even if the cap is left on at one of the ends. Is this normal and to do with the internal get-up of the EP? Or should you be able to see nothing sheer glass if at least one end has the cap on?

Sorry for going on a bit but I'd be really gutted if I've bought a damaged EP. I so, so wish I'd just spent the extra £15 and bought a brand new one now

Many Thanks,

Victoria.

[ronin]

The coating on the BST's are a blue/green not blue. So not damaged. Actually mine is Green with a slight hint of blue. Yours sounds exactly as it should be.

You are not going to damage the coating unless it is attacked with completely the wrong stuff.

Odd though it seems people clean optics all the time. You do it to the windscreen of the car with stiff rubber blades and the windows of your house with much worse then a propriatory lens cleaner.

I would simply suggest a cotton wool bud and go over the top lens, it sounds like the cleaner has just left a slight liquid mark - fairly common.

The BST should have a small cloth in with it, you could use that.

The BST has a fairly substantial eye cup and getting at the top lens to clean effectively is probably not easy.

[nicks90]

most lenses are 'coated' and hence have a colour to them, green, blue etc depending on the coating.

yes you can clean the lenses - as long as you clean it with the right stuff and dont attack it with a kitchen scourer and bleach!!! Blowing any debris off it with a puffer (or gently using your breath through a straw) and then gently cleaning it with the proper fluid (baader wonder fluid for example) and an ear bud should not cause any undue damage. Your lenses need to be fairly minging with grease and detritus before you would notice any real degredation in viewing though. So as long as you dont stick your dirty fingers on the lens or drop it in a sand pit, just leave them alone. If they do need cleaning, gently does it.

[RikM]

Avoiding cleaning eyepieces is generally good advice, but occasionally they do need cleaning. They can safely be cleaned using Baader Optical fluid and microfibre cloth or single use lens pads (recommended). As long as you are careful and follow the recommended instructions it is no problem. Have a look at the attached instructions.

http://www.firstlightoptics.com/user/opticalWonder-engl.pdf

If your EP has a green reflection/smear then it is likely that it has not been cleaned very well but hopefully no harm has been done. Get some lens pads and give it 'the final touch' as described in the instructions and see if you get a nice streak/smear free finish. Whatever you do, don't scrub at it or use too much pressure, and please don't use normal tissues. Any grit in the fibre will cause scratching of the lens coatings and this can't be fixed.

[wookie1965]

Does it look like this

[vvsloan]

Thanks all, I'm feeling much better about it now.

Wookie, it looks no where near as green as that! But surely thats got to be something very, very difficult to capture on camera (what colour/shine/coating on a lens should look like) given it all depends on the angle you're holding it at and the lens of the camera?! (but no, nothing like that bright green...)

[Charic]

I'm using the ZEISS lens wipes from Asda, and no problems with my BSTs. The lenses may also have a bit of grease on the glass from the threads of the eye cups, this is easily removed using these wipes. A finger print will be visual if looked at, but you wont see it when actually looking through the eyepiece. My BST`s are more glass looking that the photograph portrayed, that's a result of light reflections?

[vvsloan]

Yes, I think my BST is fine after some further advice and inspection, and I was being a little bit paranoid due to what is written in TLAO and my complete lack of experience in what these things should look like. I suppose it is the beginning of the long process of getting to know your equipment. Doesnt help that I cant try anything out until Xmas either.

Great to know aswell now that contrary to what is written in TL, if needed, you can actually safely clean your EP's without damaging/degrading them.

Once again, thanks people. You people in this forum are awesome .

[wookie1965]

Thanks all, I'm feeling much better about it now.

Wookie, it looks no where near as green as that! But surely thats got to be something very, very difficult to capture on camera (what colour/shine/coating on a lens should look like) given it all depends on the angle you're holding it at and the lens of the camera?! (but no, nothing like that bright green...)

It was very hard to get the wife to hold it at just the right angle i was just trying to show you that there is a coloured coating on the BST 8mm as the eyepiece the wife is holding is one.