Cleaning refractor front lens face

[Sirius Bizness]

I have an ED refractor that has dust and dew spots on the outside lens face. I want to clean this face but not sure if I might damage it. Does this face have any coatings on it or is it sensitive to cleaning? What is the best way to do it?

Thanks

Martin

[John]

The front and rear surfaces of refractor objective lenses are coated and some care is needed to avoid damaging them. As it happens I cleaned the objective of my Vixen ED102 a few nights ago. I used the Baader Optical Wonder fluid and their micro fibre cloth. I followed the instructions and sprayed the fluid onto the cloth rather than the lens. The lens has come up very well.

Don't be tempted to take a short cut on this - an objective lens is very expensive to replace, if it could be replaced at all.

[Keiran]

Martin, im just wondering how long you have owned your scope?

Does the dust and dew spots affect the viewing? if not i wouldnt touch it.

As john said the best thing for cleaning the optics of the frac is baader fluid. But do not clean mirrors with it ie reflectors or mak etc

[Sirius Bizness]

Thank you for the advice John...really appreciate it. Glad I asked before doing anything stupid.

How durable is the coating? I am wondering what it would take to damage it and what would it look like? Do they wear with repeat cleaning? On a side note...what exactly is it?...I am an engineer and these things interet me (bit geeky I know) but can't find anything about it other that the glass is referred to as FPL53.

Keiran, I have had the ED80 for a few months now and I just picked up a 120ed today .

The dust etc makes absolutely no difference from what I can see since using the ED80 so I will just leave it be for now. I am just being fussy as the Equinox 120 is beautiful and I couldn't stop looking at the green effect in the lens (whilst being slightly iritated by the dust).

Out of interest, would this have more of an effect on AP as that is what I am working towards.

Thanks again

Martin

[Keiran]

As long as you take your flats bias and darks that will get rid of any dust camera noise etc.

[John]

I think the FPL-53 element is the rear (inner) one on the ED120 and the outer (front one) is crown glass. I don't know the composition of the lens coatings but the ED range seem to be deeper in colour than the Evostar / Startravel achromat refractors. Coatings are an area where manufacturers like to keep things to themselves, presumably to maintain their competitive edge.

A bit of light dust here and there is quite normal on an objective lens after a few uses. I find a high power lens blower (manually operated) gets rid of most of it.

My Vixen ED102 uses different glass and coatings to my Skywatcher ED120 but they both seem very effective scopes

[Sirius Bizness]

I think you are right as I can't find anything on the internet about the coatings. There is lots about the glass but not the coatings. I found some good information on cleaning, which is inline with what you suggested, in a TMB telescope manual. I do not have a manual with my 120ed. Do skywatcher scopes come with one? Is there anywhere I can download one from as I have tried serching but couldn't find anything.

The manual i read online suggested cleaning only 1-2 times a year maximum in order to preserve the coatings.

[John]

I've never seen a Skywatcher manual for an ED scope to be honest but there are loads of articles on the web for cleaning refractor objectives. My Vixen ED objective has been cleaned twice in it's 12 year life. 1-2 times a year would seem excessive to me.

[PaulC-I]

Baader cleaning fluid is the best product widely available however I use disposable wipes. Using the same cloth over risks bringing contaminates over from over cleaning sessions. Even if washed the cloth could absorb hard particles from all manner of sources.

Sorry to be OCD on this but I always vacume close to the surface of the glass to lift any hard particles to ellimate them being wiped across the coatings with the cloth. A combination of this and a fine camel hair brush and a blower works well before the cleaning fluid and cloth is used.

If in any doubt Leave Well Alone! Dust on optcis does not defrade the image however finger smudges are worth considering removing as the natural acids present could permanently mark the coatings.

Just my experience and opinion YMMV

Hope this helps

Paul

[ollypenrice]

I wouldn't clean too often but actually the coatings are very hard. (That's not an invitiation to go mad, though!!!) One important thing is to use a curved wiping action since curved scratches (God forbid) will not be as visible as straight ones. It is not a lilely scenario but the professionals make a curved action a habit.

Because my stuff works very hard I do have to clean a couple of times a year but I've yet to have a mishap.

Olly

[Islander]

You'd be surprised how little effect a bit of dirt on an objective lens has on the image

Have a look at this blog article...

http://www.lensrentals.com/blog/2008/10/front-element-scratches

[Sirius Bizness]

Sorry for the stupid question but how many bits of glass or lenses are there in a doublet refractor. A lot of the dust is on the inside face from what I can see. Is there any glass after the front cell or is it dust coming in through the focusser that is landing there. Is there anyway to clean the inside without dismantling?

[Islander]

The clue is in the name - there are two lens elements in the objective of a doublet

If you remove the objective you'll probably have to collimate - it really isn't worth it unless the dust is seriously affecting your viewing.

[JamesM]

It sounds like you might be better to leave the objective for now as the contamination doesn't sound to bad to be honest. However, if in the future you feel that it is worth a clean, you might like to read these instruction from Astro-Physics on the best way to go about it. In addition, you might want to watch

video for a visual instruction on how to perform the actually cleaning but hopefully your scope isn't as bad as the one in the video!

Lastly, the Baader fluid mentioned here and above by others can be purchased from here at a modest cost and it lasts for ages. Hope that helps.

Clear skies

James

[spaceboy]

I so want to clean the lens on my C100ED but one mistake and there would be endless sleepless nights ahead. Rocket blower and that is it for me. I know it will have to be done at some point but I just know the residue of cleaning fluid will irritate me as much as the dust so as long as the views are unaffected I'm sitting on my hands.

[Sirius Bizness]

doublet...haha...should have guessed! Is the dust I am seeing on the back of the second element or can it get inbetween the two?

James, I will have a read and watch the video. Thanks.

I have just bought the Baader cleaner and also a blower/brush. The brush is ultra fine. Is it ok to use this or can the brush damage the optics.

I will leave then alone once done (for a long time), I just want to get the glass back to a clean standard now it is in my ownership.

Edited May 13, 2012 by Sirius Bizness

[Islander]

Just use the blower - the brush can pick up and harbour abrasive particles. To be honest, blower brushes generally aren't as powerful as proper rocket blowers.

Dust shouldn't get between the elements and if it is, it's probably been there since manufacture. Don't attempt to separate them!

Edited May 13, 2012 by Islander

[George]

Baader cleaning fluid is the best product widely available however I use disposable wipes. Using the same cloth over risks bringing contaminates over from over cleaning sessions. Even if washed the cloth could absorb hard particles from all manner of sources.

Sorry to be OCD on this but I always vacume close to the surface of the glass to lift any hard particles to ellimate them being wiped across the coatings with the cloth. A combination of this and a fine camel hair brush and a blower works well before the cleaning fluid and cloth is used.

If in any doubt Leave Well Alone! Dust on optcis does not defrade the image however finger smudges are worth considering removing as the natural acids present could permanently mark the coatings.

Just my experience and opinion YMMV

Hope this helps

Paul

Methanol is cheaper and nearly all the lens cleaners are based on this. Ive used it for years with no effects on both telescopes and DSLR lenses.

No doubt the purists will cringe

[Sirius Bizness]

James - just had a look through the links you sent and they are exactly what I am after. Really good written and video guides. Thanks.

I am going to do this once to make myself happy and then leave it at that. I think the common message has been less is more.

[Hawksmoor]

Thanks from me to James. Very clear and straight forward information which I found very useful.

George

[Sirius Bizness]

Operation clean complete!

Following the guide that James posted up I went ahead and gave my refractor lens a clean. I will say that the lens probably didn't need it at this point in time but as the scope was used and new to me I wanted to get off to a fresh start.

Blower brush & Baader cleaner.

Before and after shot.

The blower brush did a great job of removing the dust but it then left smuge/swirl patterns. The Baader cleaner then removed these surface contaminants. It did leave drying marks which were then removed lightly using the cloth as a finish.

I can now see two tiny reflective marks on the lens as referred to in the guide. I am not fussed by them. I am very pleased with the result and I shouldn't be needing to do it again for a very long time.

[Belcher]

Looks like a nice job done. You're a braver man than me though. I would probably leave it or take it to a scope hospital !

[lardy]

A site I came across while researching how to clean the corrector plate on my SCT http://www.arksky.org/asoclean.htm

Doc Clay lists the do's and dont's and how to mix a cleaning fluid used ... the Windex mentioned is not available in the UK (ammonia based, UK are vinegar based) but a teaspoon of household ammonia sufficed (Doc Clay's recommendation)

[ApophisAstros]

Just  cleaned my Skywatcher Ed120 and wow what a difference just like new , used the Baader optical wonder cleaner and their cloth.

Roger