Eyepiece maintenance

[Stardaze]

Having picked up a copy this week of ‘turn left at Orion’ I’ve read some

of the preamble and came across the advice regarding cleaning eyepieces,  which pretty much amounts to - don’t ever, if you can. Coming from a photography background, and having quite a few premium lenses, I'm not adverse to using a lens cleaner/ cloth or lens pen. I’ve used a lens pen on one of my EPs already. So what’s your views on this?  Some people do treat kit like newborns , whilst others no doubt will use them as tools - Im probably in the middle. Next order with FLO I’m going to add some baader wonder fluid anyway.

[Ricochet]

There is no reason not to clean a modern eyepiece as far as I am aware. The coatings will be fine if cleaned properly. The only thing to watch out for is that cleaning fluid should be sprayed onto the cleaning cloth, not the lens. If you spray it onto the lens it can travel down the edges of the lens and dissolve the blackening on the lens edges and/or leave marks on the internal lens surfaces. 

Generally the method is 

1. Blow loose particles off with a rocket/bulb blower 
2. Brush off any slightly more stubborn particles with a soft lens brush
3. Use the rocket blower again 
4. Clean oils off the lens with either a lens pen or cleaning fluid and cloth 

 

[Louis D]

Remember, scratches on the objective lens of a photographic lens have almost no effect on image quality unless a bright light is in the field of view and is projected right through it.  Then you'll see flaring.

Scratches on the objective lens of an eyepiece may be very near to the focal plane (field stop) of an eyepiece and thus very easy to see.  Scratches on the eye lens of an eyepiece will cause flaring on every bright star that passes light bundles through that spot.

Just be very careful when cleaning eyepieces.  Resist the urge to clean them in the field in the dark.  Do it in a well lit, dust free area indoors.  Make sure to flick all particles off the lenses prior to cleaning them with a liquid and cloth to remove oils and sap.  Resist the urge to disassemble an eyepiece to clean the interior unless there's obvious fungus.  Rarely does anything good come of disassembly.

Edited June 7, 2020 by Louis D

[Stardaze]

2 hours ago, Louis D said:

Remember, scratches on the objective lens of a photographic lens have almost no effect on image quality unless a bright light is in the field of view and is projected right through it.  Then you'll see flaring.

Scratches on the objective lens of an eyepiece may be very near to the focal plane (field stop) of an eyepiece and thus very easy to see.  Scratches on the eye lens of an eyepiece will cause flaring on every bright star that passes light bundles through that spot.

Just be very careful when cleaning eyepieces.  Resist the urge to clean them in the field in the dark.  Do it in a well lit, dust free area indoors.  Make sure to flick all particles off the lenses prior to cleaning them with a liquid and cloth to remove oils and sap.  Resist the urge to disassemble an eyepiece to clean the interior unless there's obvious fungus.  Rarely does anything good come of disassembly.

Very valid point about camera lenses, imperfections rarely show anything at all. A lens brush should flick off any particles. Do you clean yours occasionally Louis or leave until obvious? I wouldn't dissemble a lens myself, definitely asking for trouble. At that point, they go back for a professional job.

[John]

I use the Baader Wonder Fluid applied via their micro fibre cloth. Never apply the fluid directly onto the glass.

I don't so this often though - perhaps a couple of times a year ?

I have a manual blower to puff off any dust and loose stuff. I always do this before applying the fluid / cloth clean as well.

Some eyepiece designs have the top surface of the eye lens more exposed than others. It's the top surface that gets the dust etc. Rarely need to clean the field lenses (the bottom ones) I've found.

Some eyepieces have large glass surfaces as well but those are easier to clean than the ones that have tiny lenses.

 

[Louis D]

I always wear eyeglasses with long eye relief eyepieces when observing due to strong astigmatism (2.0 diopters), so my eye lenses rarely need cleaning because of that barrier.  I've probably only ever cleaned the eye lenses every 5 or 10 years unless there's obvious image degradation from eye lens crud.  More often, it's my eyeglasses to blame.

[Paz]

One thing I do every time I finish using an eyepiece is blow it with a blower. Particles are much easier to remove soon after they land. Given time, and especially given humidity and a dewed up lense, particles will kind of cement on and become much harder to remove.

[davhei]

8 hours ago, Paz said:

One thing I do every time I finish using an eyepiece is blow it with a blower. Particles are much easier to remove soon after they land. Given time, and especially given humidity and a dewed up lense, particles will kind of cement on and become much harder to remove.

Agree. I don't go through the whole process of cleaning with fluid very often, but after each session I do give the eyepieces a good puff with the bulb blower to get rid of loose particles. Usually give the outer casings a wipe with tissue paper at the same time before putting them in storage. That's obviously not really necessary from an optics perspective though.

[fozzybear]

A question on cleaning eyepieces Len's If the good old wonder fluid not avail could you use spectacle cleaning spray (with lint free cloth) or is this a no no. as had a good look on the forum yet no definitive answer. In order to remove grease stains not debris?

many thanks

Andy

[mikeDnight]

This was originally suggested to me by Nick Hudson of TruTec Astro (ExpertTakahashi retailer). Caloclean spray and Calocloth lens cloth is what I use on all my optics. Although it's sold at almost any opticians, it is designed for high end camera lenses. I've used this on my eyepieces and on my Takahashi objective lens for years. Its excellent! It is also inexpensive and readily available. (Spray onto the cloth rather than directly onto the lenses so as to prevent seepage between the elements!)

 

Edited June 13, 2020 by mikeDnight

[Louis D]

Al Nagler has recommended Windex in the past.  I've used it and it works well.

[fozzybear]

8 minutes ago, Louis D said:

Al Nagler has recommended Windex in the past.  I've used it and it works well.

windex=windolene SC Johnson equiv in Europe? (glass cleaner) well I never...

[Louis D]

45 minutes ago, fozzybear said:

windex=windolene SC Johnson equiv in Europe? (glass cleaner) well I never...

The only ingredient in it that concerns me is the blue food coloring.  Hopefully, it all wipes off.

For really grungy eyepieces on old eyepieces, I've had to disassemble them, note the order and direction of each element and spacer ring, and wash the elements with dish detergent over a thick towel (in case it slips out) in the kitchen sink using my fingertips as scrub pads.  I then lay them on a dry, clean cotton cloth to dry it, giving them a light wiping to avoid spotting.  That's the only way I've found to git rid of some tough grime.

[jock1958]

10 hours ago, fozzybear said:

A question on cleaning eyepieces Len's If the good old wonder fluid not avail could you use spectacle cleaning spray (with lint free cloth) or is this a no no. as had a good look on the forum yet no definitive answer. In order to remove grease stains not debris?

many thanks

Andy

Nowadays I use the alcohol free lens cleaner from Specsavers with Baader cloths which works a treat.

[Stu]

7 minutes ago, jock1958 said:

Nowadays I use the alcohol free lens cleaner from Specsavers with Baader cloths which works a treat.

I used that too, particularly on the FC100DC objective when I cleaned it. Works well.

Baader WF excellent too.

[jock1958]

10 minutes ago, Stu said:

I used that too, particularly on the FC100DC objective when I cleaned it. Works well.

Baader WF excellent too.

It was recommended on a lens cleaning thread a while back but can’t remember by who? 

[Stu]

3 hours ago, jock1958 said:

It was recommended on a lens cleaning thread a while back but can’t remember by who? 

Quite possibly @mikeDnight! 👍