What's this on my secondary?

[BGazing]

I know, I know...never turn a flashlight down the catadioptric tube. But I did , for another reason, and I noticed (well, one does notice when one is inquisitive) that, at a certain angle of incidence, darned photons bring out some blue streaks on the secondary. Pic attached. Anyone has any idea as to what that might be?

Mind you, this is not primary, this is enlarged reflection of the secondary, under oblique rays.

[darknight]

dunno, I guess, lens covering peeling?

[Mr niall]

Those look like machine marks, I'd guess residue from applying coatings or final polish maybe? Nothing a bit of sandpaper shouldn't fix....

[xtreemchaos]

if you carnt see it when viewing or in your images I wouldn't worry about it, havnt a clue what it is mate. charl.

[Peter Drew]

Seems like some sort of residue. It's a small proportion of the total area so shouldn't significantly impact on the performance.  You can either ignoe it or strip the whole thing down, try and clean it or send it away for recoating followed by refitting it accurately and then collimating the system. The choice is yours!  

[LightBucket]

It's looks like it's on the corrector plate and neither the primary or secondary...!!

and looks like damage to the delicate coatings... 

[BGazing]

24 minutes ago, LightBucket said:

It's looks like it's on the corrector plate and neither the primary or secondary...!!

and looks like damage to the delicate coatings... 

It's not corrector. What you are seeing is a crop of a picture, reflection of the secondary in the primary mirror.

[BGazing]

40 minutes ago, Peter Drew said:

Seems like some sort of residue. It's a small proportion of the total area so shouldn't significantly impact on the performance.  You can either ignoe it or strip the whole thing down, try and clean it or send it away for recoating followed by refitting it accurately and then collimating the system. The choice is yours!  

Well, this was the only thing I could catch on phone camera to a degree. Visually, once I hit the angle it looks like as if there was something applied with a brush (there are additional marks) or, as someone suggested, not peeled off properly.

A mystery, indeed. Perhaps I should run Lymax cooler for 24 hrs and see if it disappears. 

[LightBucket]

I would like to see the full Image..!

[BGazing]

[LightBucket]

Hmmm, yes I see what you mean now, that makes more sense on the bigger image, well to get marks like that on the secondary, someone maybe has removed it and tried to clean....is that possible, did you buy the scope secondhand..?

or maybe even put something down the open end to the mirror to try and remove some dust or something, I have known people do that, rather than remove then secondary to save re collimating...

[BGazing]

Nope, purchased new.

I have a Fastar compatible tube, so I guess I could even remove secondary without removing the corrector plate...if I only knew how that is done...

[Peter Drew]

That would be your best bet, I think there is an external securing ring, once removed the secondary unit can be withdrawn. If the securing ring is tight be careful you don't rotate the corrector plate. 

[Waldemar]

Yes, the retaining ring should be screwed loose and then you can remove the complete secondary mirror. Be careful!!

The best way to do this is with the scope pointing up, so the secondary can not drop.
There is a little line up feature on it, so you can only put it back in in one way. No room for error.

To me it looks in your picture as if the coating has been damaged when putting the secondary in place, by touching the holder with the mirror in a clumsy way.

I hope I am wrong though...

[BGazing]

32 minutes ago, Waldemar said:

Yes, the retaining ring should be screwed loose and then you can remove the complete secondary mirror. Be careful!!

The best way to do this is with the scope pointing up, so the secondary can not drop.
There is a little line up feature on it, so you can only put it back in in one way. No room for error.

To me it looks in your picture as if the coating has been damaged when putting the secondary in place, by touching the holder with the mirror in a clumsy way.

I hope I am wrong though...

Thanks!

So the scope should point up so that the secondary does not fall out of the scope, correct?

Well, if I clean it and it still shows those spots, you might be right. But what bugs me is the following - it does not look like the coatings are failing, it looks more like there is something extra on it, not less than it is supposed to be. There are no scratches on it...and your scenario is the one in which there was (I guess) a scratching damage...

[Waldemar]

Yes, that is correct. To me the damage does look like scratches..., but if it has been stored upside down in a hot environment, it could also be that the grease on the central tube, over which the primary mirror moves leaked out a bit and fell on the secondary mirror. 

If it is not visible when observing, I would not put too much effort in it. You might make it worse that it is...

[BGazing]

Nah, heard about the grease incident...but never stored it upside down. It is always horizontal.

Sent a photo to my dealer, hopefully there will be a word back from Celestron.

[BGazing]

update, asked vendor, told me to clean secondary and report if it cannot be cleaned.

so tube angled upright, unfasten ring and pull out secondary. no marking needed? did i miss anything?

i reckon i am too much of a wuss to do it right away, yet the courage i need cannot be of the dutch sort (apologies to dutch members of the forum)

[Waldemar]

Like I said there is a guiding pin sticking out on the side of your secondary holder, so it can only be put back in one way.

Don't worry, it is really easy. Do NOT rub the mirror surface with anything!!!
Have a good look at it first before you do anything! Preferably with a magnifying glass.

Clean as suggested in the attached file

I am Dutch!!

CLEANING MIRRORS.docx

[BGazing]

18 minutes ago, Waldemar said:

Like I said there is a guiding pin sticking out on the side of your secondary holder, so it can only be put back in one way.

Don't worry, it is really easy. Do NOT rub the mirror surface with anything!!!
Have a good look at it first before you do anything! Preferably with a magnifying glass.

Clean as suggested in the attached file

I am Dutch!!

CLEANING MIRRORS.docx

I know LOL