Scratched the coating on my scope need help!

[Jake127]

So I will start by saying I can't believe I would even think of doing this, especially with a $2,000 refractor. I noticed lots of dust on the front element of my scope and it would not blow off using my lens blower so I did something stupid and I knew never to do this but I started wiping the front element with a microfiber cloth and scratched the coating. 

My question is will it ruin or degrade the quality of the image? It is a 5.5inch refractor. I do astrophotography.

I attached an image of it

the big scratch is in the bottom left

[Charic]

Is it definitely a scratch, not hopefully just a smear and to be honest in full screen with the  image enlarged, of the three potential marks I observe, it was the last one I noted? I have edited to show what I see! 

I think the first option is not to panic, hide your face in shame maybe, but you won't be the first to mark something, but try imaging and see if it does cause any ill effect?

[Highburymark]

Difficult to see where the scratch is from the pic - but very unlikely it would make any difference to the scope's performance

[Peter Drew]

I would be very surprised if it will make any difference to visual or photographic results, the value, if you decide to sell it in the future, might be a different matter.

[Timebandit]

Hello and welcome to SGL

Sorry to hear of your unfortunate incident when cleaning. I think a lesson to us all that try your best not to touch the lens unless you really need to. And if you have got to clean your lens then make sure anything you use is spotlessly clean and grit free.

From your photos the scratches will probably have a lot more effect on your mind and kicking yourself for ever cleaning the scope. But from a visual or AP point of view I doubt it will have any impact at all on the quality of image 

I hope the above helps

[pete_l]

46 minutes ago, Jake127 said:

My question is will it ruin or degrade the quality of the image? It is a 5.5inch refractor. I do astrophotography.

Almost certainly not. A great deal of dirt has to accumulate on an optical surface before it has any measurable effect on image quality, or visual performance. A tiny imperfection like this will be completely invisible. Especially after subs are aligned as the scratch will be on different parts of each one, so it will be processed-out.

[Jake127]

Thanks to all so far of the reassuring comments, and yeah it was a bad picture I will take a better one when I get home later to show. When you look at the lens in person the scratches are pretty distinct and I do think that the built in field flattener may have a coating to help but I agree with what timebandit said how the scratches will have more of an impact on my mind than the quality of the image and is hopefully true and this is a refractor so the coatings do matter as much but a Newtonian, you can't image or look through a scope if it is not coated. 

[DRT]

27 minutes ago, Jake127 said:

you can't image or look through a scope if it is not coated. 

Hmmm? I don't think that is correct. We have had telescopes for centuries and coatings for a few decades

 

[Jake127]

33 minutes ago, DRT said:

Hmmm? I don't think that is correct. We have had telescopes for centuries and coatings for a few decades

 

A Newtonian needs the coating otherwise nothing will reflect off of the mirrors surface is what I believe. 

[DRT]

11 minutes ago, Jake127 said:

A Newtonian needs the coating otherwise nothing will reflect off of the mirrors surface is what I believe. 

A Newtonian needs a mirror. A mirror does not need a coating, although it will benefit from one.

[Jake127]

19 hours ago, DRT said:

A Newtonian needs a mirror. A mirror does not need a coating, although it will benefit from one.

But the reflective surface is a coating on the glass right? So if the reflective coating is not there then it would be a piece of grinded glass. The reflective surface is put on the glass in a vacume using all types different chemicals that are ionized I believe and the stick to the surface because it is the only mass in the vacume chamber so the reflective surface is a coating.  

[steppenwolf]

Different kinds of coating. A Newtonian glass mirror has a ground concave surface on which a metal coating is applied  and then to protect the metal coating a transparent 'overcoat' is applied. A refractor does not NEED a coating on its lens elements but applying one reduces reflections from the glass surfaces so more of the light passes through the glass lens and off on down to the eyepiece/camera.

[DRT]

58 minutes ago, Jake127 said:

But the reflective surface is a coating on the glass right? So if the reflective coating is not there then it would be a piece of grinded glass. The reflective surface is put on the glass in a vacume using all types different chemicals that are ionized I believe and the stick to the surface because it is the only mass in the vacume chamber so the reflective surface is a coating.  

 

4 minutes ago, steppenwolf said:

Different kinds of coating. A Newtonian glass mirror has a ground concave surface on which a metal coating is applied  and then to protect the metal coating a transparent 'overcoat' is applied. A refractor does not NEED a coating on its lens elements but applying one reduces reflections from the glass surfaces so more of the light passes through the glass lens and off on down to the eyepiece/camera.

And a mirror does not need to be made from glass - it can be made from polished metal

[steppenwolf]

1 minute ago, DRT said:

And a mirror does not need to be made from glass - it can be made from polished metal

Ah yes, Speculum mirrors like wot Newton used to make -  not used one of those since Adam was a lad!

[RichLD]

Check out this article, it really does give some idea of how much a lens can be damaged before you'd notice any difference in the image...

[DRT]

21 minutes ago, RichLD said:

Check out this article, it's really does give some idea of how much a lens can be damaged before you'd notice any difference in the image...

The smashed lens says it all - we should all remember that the next time we see a speck of dust on a refractor lens!

 

[Timebandit]

22 minutes ago, RichLD said:

Check out this article, it's really does give some idea of how much a lens can be damaged before you'd notice any difference in the image...

 

warning . May I suggest you do not try this experiment on your expensive refractor. As you may get different results? ?

[kirkster501]

Don't worry about that "scratch".  It is nothing and will make infinitesimal difference to the image.

[pete_l]

2 hours ago, DRT said:

And a mirror does not need to be made from glass - it can be made from polished metal

The glass does nothing except act as a base to hold the extremely thin layer of aluminium (or silver, in the old days) that actually does the reflecting.

[Alien_Photons]

Jake.

A heart breaking exiperence no doubt. I have broken and damaged a few things over the years. We live and learn.

Kevin.

[Louis D]

1 hour ago, pete_l said:

The glass does nothing except act as a base to hold the extremely thin layer of aluminium (or silver, in the old days) that actually does the reflecting.

Mirror grinders do their testing using nothing but the partial reflectivity of the raw glass prior to coating to see if more figuring is needed.  So technically, the glass does reflect somewhat.  After all, when you flip your rearview mirror to dim high beams, you're just using the reflectivity of the glass alone.

[mikeDnight]

10 hours ago, pete_l said:

The glass does nothing except act as a base to hold the extremely thin layer of aluminium (or silver, in the old days) that actually does the reflecting.

The glass doesn't do nothing. It's the accurate figure on the concave mirror surface that forms the image. The aluminium coating merely enhances reflectivity.

Mike