I have a small, 80 mm achro refractor I'd like to sell. Problem is that
the lens appears quite dirty. I believe they are spots caused from
dewing up where dust/ dirt sticks while wet and then of course stays
there when dried. I tried some non-aerosol compressed air and little
difference was made. Don't have a lot of $ to spend for elaborate
cleaning tools, but what more could I try that's simple, cheap, and
won't harm the lens. Could I do anything with Everclear and cotton
swabs? That's about all I have on hand.

On Thursday, July 22, 2021 at 9:47:42 AM UTC-7, Ruk wrote:
> I have a small, 80 mm achro refractor I'd like to sell. Problem is that
> the lens appears quite dirty. I believe they are spots caused from
> dewing up where dust/ dirt sticks while wet and then of course stays
> there when dried. I tried some non-aerosol compressed air and little
> difference was made. Don't have a lot of $ to spend for elaborate
> cleaning tools, but what more could I try that's simple, cheap, and
> won't harm the lens. Could I do anything with Everclear and cotton
> swabs? That's about all I have on hand.

Use soapy water or alcohol 99%, than rinse it with distilled water well.
Repeat if still not clean enough!

On Thursday, July 22, 2021 at 12:47:42 PM UTC-4, Ruk wrote:
> I have a small, 80 mm achro refractor I'd like to sell. Problem is that
> the lens appears quite dirty. I believe they are spots caused from
> dewing up where dust/ dirt sticks while wet and then of course stays
> there when dried. I tried some non-aerosol compressed air and little
> difference was made. Don't have a lot of $ to spend for elaborate
> cleaning tools, but what more could I try that's simple, cheap, and
> won't harm the lens. Could I do anything with Everclear and cotton
> swabs? That's about all I have on hand.

Try to sell it as-is and let the new owner decide what to do.

On Thursday, July 22, 2021 at 9:47:42 AM UTC-7, Ruk wrote:
> I have a small, 80 mm achro refractor I'd like to sell. Problem is that
> the lens appears quite dirty. I believe they are spots caused from
> dewing up where dust/ dirt sticks while wet and then of course stays
> there when dried. I tried some non-aerosol compressed air and little
> difference was made. Don't have a lot of $ to spend for elaborate
> cleaning tools, but what more could I try that's simple, cheap, and
> won't harm the lens. Could I do anything with Everclear and cotton
> swabs? That's about all I have on hand.

Cheap achro scope like that, just throw it in the washing machine than hang it out to dry.
It'll be fine!

On Thursday, 22 July 2021 at 12:47:42 UTC-4, Ruk wrote:
> I have a small, 80 mm achro refractor I'd like to sell. Problem is that
> the lens appears quite dirty. I believe they are spots caused from
> dewing up where dust/ dirt sticks while wet and then of course stays
> there when dried. I tried some non-aerosol compressed air and little
> difference was made. Don't have a lot of $ to spend for elaborate
> cleaning tools, but what more could I try that's simple, cheap, and
> won't harm the lens. Could I do anything with Everclear and cotton
> swabs? That's about all I have on hand.

Everclear would work fine. Cotton swabs are good. Use short strokes, not circular ones.

On 22/07/2021 20:06, W wrote:
> On Thursday, July 22, 2021 at 12:47:42 PM UTC-4, Ruk wrote:
>> I have a small, 80 mm achro refractor I'd like to sell. Problem is that
>> the lens appears quite dirty. I believe they are spots caused from
>> dewing up where dust/ dirt sticks while wet and then of course stays
>> there when dried. I tried some non-aerosol compressed air and little
>> difference was made. Don't have a lot of $ to spend for elaborate
>> cleaning tools, but what more could I try that's simple, cheap, and
>> won't harm the lens. Could I do anything with Everclear and cotton
>> swabs? That's about all I have on hand.
>
> Try to sell it as-is and let the new owner decide what to do.

+1

Unless you know how to clean optics properly without putting fine
scratches into the surface you could do more harm than good.

Optics will tolerate a few fly spots on them without them making any
discernable difference. A Newtonian works pretty well with a big chunk
of the mirror obscured. A few minor spots won't make any difference to
the image quality until the dirt gets so thick it affects light grasp.

Improper cleaning with the wrong method will ruin the optical surfaces.
Most people are inclined to press too hard and be using materials that
are unsuited to cleaning optics safely (traces of silica in them).

If you must do it then use short mostly radial strokes and very light
pressure letting the water do all the work of lifting the dirt.
Rinse afterwards with distilled water.

Assuming it is an air spaced achromat try not to get water into the
airspace between the element that will not do it any good at all.
(ie don't dunk it in a bowl of water)

--
Regards,
Martin Brown

On Thursday, July 22, 2021 at 12:47:42 PM UTC-4, Ruk wrote:
> I have a small, 80 mm achro refractor I'd like to sell. Problem is that
> the lens appears quite dirty. I believe they are spots caused from
> dewing up where dust/ dirt sticks while wet and then of course stays
> there when dried. I tried some non-aerosol compressed air and little
> difference was made. Don't have a lot of $ to spend for elaborate
> cleaning tools, but what more could I try that's simple, cheap, and
> won't harm the lens. Could I do anything with Everclear and cotton
> swabs? That's about all I have on hand.

Here is a video with important suggestions and tips for cleaning lenses...
https://www.youtube.com/watch?v=JkxbB1rkSGI
The kits mentioned run about $25 not including shipping.

I think the best strategy is just to include information and pics of the dirty lens, advertise it "AS-IS" at a somewhat reduced price and let the buyer decide how to proceed. Telescopes in this size range are not exactly rare, but they are still valuable to someone who wants one. It is best not to damage them through incorrect cleaning techniques.

https://media.giphy.com/media/SuIDKboVhHgtLPG6zm/giphy.mp4

On Friday, 23 July 2021 at 04:54:50 UTC-4, Martin Brown wrote:
> On 22/07/2021 20:06, W wrote:
> > On Thursday, July 22, 2021 at 12:47:42 PM UTC-4, Ruk wrote:
> >> I have a small, 80 mm achro refractor I'd like to sell. Problem is that
> >> the lens appears quite dirty. I believe they are spots caused from
> >> dewing up where dust/ dirt sticks while wet and then of course stays
> >> there when dried. I tried some non-aerosol compressed air and little
> >> difference was made. Don't have a lot of $ to spend for elaborate
> >> cleaning tools, but what more could I try that's simple, cheap, and
> >> won't harm the lens. Could I do anything with Everclear and cotton
> >> swabs? That's about all I have on hand.
> >
> > Try to sell it as-is and let the new owner decide what to do.
> +1
>
> Unless you know how to clean optics properly without putting fine
> scratches into the surface you could do more harm than good.
>
> Optics will tolerate a few fly spots on them without them making any
> discernable difference. A Newtonian works pretty well with a big chunk
> of the mirror obscured. A few minor spots won't make any difference to
> the image quality until the dirt gets so thick it affects light grasp.
>
> Improper cleaning with the wrong method will ruin the optical surfaces.
> Most people are inclined to press too hard and be using materials that
> are unsuited to cleaning optics safely (traces of silica in them).
>
> If you must do it then use short mostly radial strokes and very light
> pressure letting the water do all the work of lifting the dirt.
> Rinse afterwards with distilled water.
>
> Assuming it is an air spaced achromat try not to get water into the
> airspace between the element that will not do it any good at all.
> (ie don't dunk it in a bowl of water)
>
> --
> Regards,
> Martin Brown

Only time you should clean is when dust or dirt is noticeable or you suspect a spot may be from something that etch the coating or lens.