Mirror coating or cleaning needed for my 10" OO?

[nitram100]

So I finally got around to using my 10" for the first time in a while and although I know the collimation is not perfect, the visual images have been quite disappointing. 

m81, m82, m63 etc all seem much dimmer than when I viewed them years ago (from a site with much worse loght pollution) I remember distinctly seeing the sunflower shape in m63 but now it's just a fuzzy blob.

I know my collimation is out a little of whack as stars are not pin point and look like little comets in the eyepiece and venus doesn't snap into focus, it has like a ghost of the planet to ht left  of it but would this affect galazy viewing also? 

One thing is that the mirror is an OO 10" and was bought new by me in 2002 and has never been cleaned or recoated, could it be time for one of these to be done? Would that be degrading my image this much?

Thanks for any info. 

 

Martin

[Peter Drew]

Although from your image description the collimation appears to need attention as this will have an impact on the overall performance, 18 years is quite a good innings for a Newtonian mirror.  I would remove the mirror and give it a clean.  Afterwards have a look to see if you can see through the mirror from its back, if you can then a recoat will be beneficial.         🙂

[johninderby]

A mirror has to be really dirty to affect viewing. Could you post a photo of the mirror (without flash). And yes an old mirror may be due a recoating.

https://www.orionoptics.co.uk/OPTICS/mirrorrecoating.html

Edited April 20, 2020 by johninderby

[nitram100]

Thanks for the reply guys, yes I have read that a mirror has to be really dirty to affect performance, which is kinda why I never bothered.

The telescope all of its life indoors in a cupboard, well protected so was never concerned too much about dust, dirt etc leaning more towards the coating.

Will get pic of the mirror up later guys thanks a lot.

 

[nitram100]

[nitram100]

Hi guys, I took some photos of the mirror. 

Does it looks as though as everything is a bit greyish? I definitely remember this mirror being super reflective, now every reflection just looks muddy and washed out, kinda the same image I'm getting in the eyepiece. 

I did that fan mod years and years ago, is it possible lots of dust has gotten in over the years? 

Thanks guys, I also orderd some distilled water and going to give this a clean on Wednesday.

[johninderby]

The mirror doesn’t look too bad at all. Of course you won’t know for sure until it’s been cleaned. Being stored indoors in the dry helps prevent mirror deterioration. It's being stored in a damp enviroment such as a garage or shed for a long time that really causes mirror problems.

Hope to seea shiny clean mirror in a couple of days then. 👍🏻

Edited April 20, 2020 by johninderby

[nitram100]

3 hours ago, johninderby said:

The mirror doesn’t look too bad at all. Of course you won’t know for sure until it’s been cleaned. Being stored indoors in the dry helps prevent mirror deterioration. It's being stored in a damp enviroment such as a garage or shed for a long time that really causes mirror problems.

Hope to seea shiny clean mirror in a couple of days then. 👍🏻

Cheers mate! Looking forward to giving it a good clean. 

I took the mirror out again just to have a look and found the mirror retaining clips were very tight, could this be why I was seeing comet shaped stars and venus ghosting? 

I removed the clips and put them back on looser, able to slip a piece of paper underneath each one. 

Also gave me a little peak of what the mirror looks like under that gunk! 

 

 

[johninderby]

Yes the clips shouldn’t be too tight as it can indeed cause those problems. I adjust until just touching and then back off about 1/8 of a turn.

[nitram100]

Hi guys , just to update , I gave the mirror a clean just now and wow what a difference, I can actually see my eye in the reflection in the secondary now. Going to collimate and get ready for tonight.

The reflection in the mirror in the pic with the specks of gunk is from the kitchen window , the mirror itself is sparkly. I held it up to the light from the back and could only see 2 or 3 miniscule sizes spots where light was getting through, would this be considered fine for an 18 year old mirror coating?

 

thanks guys

 

[johninderby]

Looks like it should give a few more years good service. A few tiny pinholes, while not desirable, shouldn't have any noticeable effect. 🙂

Edited April 22, 2020 by johninderby

[Peter Drew]

Good to go!      🙂

[nitram100]

Have to say I'm impressed at how well this mirror has aged. Glad I went with Orion Optics all those years ago.

[niallk]

Looking good

[nitram100]

Just got in from a lovely viewing session! Definitely a big difference, stars are pin point, definitely more contrast in galaxies, could now make out the sunflower shape of m63 and I couldn't stop getting lost in m13 and m92 in the 82 degree eyepiece, can't bloody wait until tomorrow night cheers guys.

[johninderby]

Nice to hear the first use after cleaning went so well. 🙂

[niallk]

Great stuff!