Oh my..is this a mirror defect?!!

[emadmoussa]

While collimating to go out this evening  I noticed there were 3 or more smears (or something) on the outer edges of the primary mirror. When you look closely from a certain angle you can clearly see them.

I'm under the impression the mirror was rotated because the 3 marks somehow match the three clips. There's one little smear peaking from underneath one of the clips.  When you shed a light on these smears they don't seem reflective like the rest of the primary surface...

No, I have never come near the primary

Is this a defect? Worth talking to FLO about it?

I tried to take a proper photo...but I guess these can show what I'm talking about..

Thanks for looking

[houston]

Id take the mirror out to have a closer look. Put some masking tape on tube and cell with a line on so it goes back in same way.

[sbooder]

They look like bevel imperfections to me it is where the coating has not taken on a badly bevelled mirror.

[emadmoussa]

I have the scope out now and can by looking at the mirror in moonlight see these badly coated or smeared areaS. Does that qualify as a defect to discuss with FLO?

[glappkaeft]

I have the scope out now and can by looking at the mirror in moonlight see these badly coated or smeared areaS. Does that qualify as a defect to discuss with FLO?

Ask them.

[knobby]

1 - I'd doubt much lights gets to the very edge of the mirror

2 - I'd doubt very much if those marks will affect viewing at all

3 - I would worry about it possibly getting worse over time

4 - I probably couldn't be bothered to send it back

5 - Its your scope / your decision you'll have to weigh up the pro's and cons

End of the day, you've noticed it and it's going to bug you now ...

good luck mate

[emadmoussa]

It is not affecting the views. But likeyou say my concern it might get worse over time as the badly coated areas might eat into the intact ones. And yes, I wouldnt be bothered sending it back...unless it is absolutely necessary. I think mirror replacement will be the ideal solution if the current one is likely to get worse...

[glappkaeft]

That the edges of a Newton mirror are incorrectly figured or has artifacts is not uncommon. A friend (Gunnar of the SW 190MN modifying thread fame) could not get rid of his triangular stars without masking away a few mm of his main mirror.

[Peter Drew]

If you added up all the other marks on the mirror shown in the first photo I think they would more than match the edge "smear"  

[emadmoussa]

These are just dust bits that show themselves under flashlight same as the case with all mirrors and lenses

[faulksy]

hi emad, as you say it doesnt affect the views, but how do you no that, flo are great im in talks with them now about my focuser and they are sorting it, if that was my mirror that would flip my head and i wouldnt be able to live with that, but the decision is yours.

[emadmoussa]

I will be talking to Steve or Martin in the morning. Im just hoping this is a defect that is unlikely to aggravate.

[FLO]

Hhmmm...  It is highly unlikely to affect performance, it almost certainly won't worsen and minor blemishes at the edge of a mirror are not uncommon. Also shining a flashlight at any Newtonian mirror will highlight smudges and marks that would not normally be discernible. If, as you say, they are in line with the mirror clips then you might even find they wipe off if/when you clean the mirror.

Are you pleased with the views? If you are then I'd keep it, or at least leave it a while before making a decision. But rest assured if you decide you'd like it changed (now or later) we'll happily do that, though you might need to be patient because finding one with a blemish-free edge will probably take us a while. 

FWIW the marks wouldn't trouble me but if you are concerned please email to arrange a replacement

HTH, 

Steve 

[HD-AP]

presumably this is a new mirror/telescope .

If so these defects appear to extend beyond the mirror edge bevel ?

Are they a coating defect like rail marks seen on some mirror recoats ,due to the way the mirrors are mounted in the coating chamber . Or are they physical damage to the coating caused by rotation of the mirror under the mirror clips .

Either are not really acceptable in a new telescope .You should not see marks like these on a new mirror.

regards

[emadmoussa]

Hhmmm...  It is highly unlikely to affect performance, it almost certainly won't worsen and minor blemishes at the edge of a mirror are not uncommon. Also shining a flashlight at any Newtonian mirror will highlight smudges and marks that would not normally be discernible. If, as you say, they are in line with the mirror clips then you might even find they wipe off if/when you clean the mirror.

Are you pleased with the views? If you are then I'd keep it, or at least leave it a while before making a decision. But rest assured if you decide you'd like it changed (now or later) we'll happily do that, though you might need to be patient because finding one with a blemish-free edge will probably take us a while. 

FWIW the marks wouldn't trouble me but if you are concerned please email to arrange a replacement

HTH, 

Steve

Thanks a lot, Steve. I will drop you an email in the morning with more details on the situation. I hope it won't come to a replacement though .

Thanks again.

[FLO]

No problem  

[LukeSkywatcher]

Hhmmm...  It is highly unlikely to affect performance, it almost certainly won't worsen and minor blemishes at the edge of a mirror are not uncommon. Also shining a flashlight at any Newtonian mirror will highlight smudges and marks that would not normally be discernible. If, as you say, they are in line with the mirror clips then you might even find they wipe off if/when you clean the mirror.

Are you pleased with the views? If you are then I'd keep it, or at least leave it a while before making a decision. But rest assured if you decide you'd like it changed (now or later) we'll happily do that, though you might need to be patient because finding one with a blemish-free edge will probably take us a while. 

FWIW the marks wouldn't trouble me but if you are concerned please email to arrange a replacement

HTH, 

Steve 

I have to completely agree. Whatever it is around the edge..........will/should not make any difference to the performance of the scope.

If you decide that you simply can not live with it, FLO have said they will replace it.

Cant get fairer then that. Personally i dont see the need to replace it.

Camera flash, certainly does highligh things and they seem worse then they really are.

[FLO]

Emadmousa contacted us this morning to say the smudges wiped off easily with a little cleaning fluid so all is well.

We like happy endings  

Steve

[emadmoussa]

Yes, it was a plastic residue from the mirror clips - perhaps resulted from rotating the mirror without loosening the clips. A bit of Baader magic fluid carefully applied was enough to get rid of the smudges. Yes, glad it wasn't a problem with the coating or scratches.

Thanks FLO for the support