Fingerprints on Secondary - SW 130p

[inertia8]

Hi All,

I've read thru a number of older discussions on fingerprints on mirrors and there seems to be no conclusive answer on yay or nay. Some say it will have little affect on performance, others say that whilst this is true the fingerprints contain amino acids and oils from the body, which will eat away at the mirror coating and thus should be removed.. Others dispute this and say that modern mirrors have a protective coating or that the fingerprints won't damage the mirror coating.

The discussion of a protective coating leads to some saying that the mirrors are therefore not as fragile and can be cleaned with care taken not to drag particles across the mirror.

Turn left at orion effectively states - don't try to clean the mirrors until they are effectively unusable, thus nothing to be lost if it goes bad.

I bought my scope second hand and it came with a couple of little smudges on the secondary, I wasn't terribly fussed. Then came a stupid moment last night when I hurriedly setup after watching Captain Phillips, good movie btw, and proceeded to absentmindedly reach in under the dust cap to "pop it out"... naturally my fingers recoiled in horror the instant they touched the secondary, however... more smudges.

Performance, well it was hard to tell, things didn't seem quite as sharp but I'm willing to admit that's either my paranoia from touching the mirror or that the seeing wasn't great after a couple of hot days then a cool change and it was a bit windy in places. Shining a light on the mirror reveals the horror but I've read that very few mirrors will present well under this scrutiny.

Question 1) Does anyone know if the secondary mirrors in the SW Heritage 130P are protected?

Question 2) Should I clean it?

Question 3) If I stuff up, are replacement mirrors available and at what cost?

Thanks

[barx1963]

Question 1) Does anyone know if the secondary mirrors in the SW Heritage 130P are protected?
A) Not sure but would be very surprised if they weren't

Question 2) Should I clean it?
A) Probably not unless it get really dirty. With secondarys, a bit of a soak in lukewarm water with just a drop or 2 of dishwasher detergent, then use some cotton balls to run over the mirror letting gravity moved them (ie not scrubbing) then rinse in demineralised water and sit vertical so the water runs off.

Question 3) If I stuff up, are replacement mirrors available and at what cost?
A) Almost certainly not available as a specific Skywatcher part. You might try shopping online for a similar size secondary. The mirrors on these are 34.5mm on the minor axis which is roughly 1.36". Astro Systems sell a 1.3" mirror for US$50 plus freight (see http://www.astrosystems.biz/secm1.htm) but you would need to see how you go about fitting it.

Cheers

Malcolm

[dannat]

1 -i doubt they would be overcoated on a scope of that price
2 -i would, either use windex or alcohol ..make sure when you wipe it whatever cloth you ue is not dragged across it dry
3. telescopes-astronomy in SA have some cheapies for $35

[inertia8]

I guess I'll try and muster up the courage to remove it and clean it in the coming weeks then... I shall try and confirm if the mirror is coated with the manufacturer.

Ta.

[Monstar]

SKY-WATCHER DELUXE MIRROR COATINGS: Most reflectors today usually have a coat of aluminium as the mirror surface and then an overcoat of silicon monoxide or silicon dioxide to protect it. Silicon dioxide produces a much more durable coat than silicon monoxide but requires specialized equipment to apply it and is therefore more expensive. Protection is needed, because in most reflectors, the mirror is open to the elements and deterioration of the reflective layer reduces the resolution of the telescope. ALL Sky-Watcher reflectors are Multi-Coated with Silicon Dioxide as standard for Optimum Durability and Long Term Performance.

http://www.eurocosm.com/Application/Products/Telescopes/heritage-130P-telescope-GB.asp


Some peoples advice, sheesh...

[barx1963]

Found reference to coatings on the SW website here http://skywatcher.com/knowledge.php?id=10

So definitely coated!

[inertia8]

Thanks for that guys, I guess I can be confident then that if I treat the mirror very carefully I am unlikely to ruin it!

[JZ]

If you do try washing it you could try isopropyl alcohol, which you can get from Jaycar <http://www.jaycar.com.au/productView.asp?ID=NA1066>.

Oils from your skin are soluble in it and with gentle squirting should just wash off without you having to touch the mirror with anything else. It evaporates fast so make sure you drain it all off into a dish. You can mix it 50/50 with distilled water to slow the evaporation. This is a common method for cleaning camera lenses.

Cheers,
Ross...

[inertia8]

Given the collapsible truss design and the mirror being out in the open, am I best off removing the mirror for cleaning or would it suffice to seal off the primary tube and use iso propyl spray with the mirror slanted so it runs off?

My feeling would be to remove it?

[inertia8]

Given I now have the 8" loan scope I've mustered up the courage to remove the mirror and proceed to cleaning it this weekend or next. Most advice is that the fingerprint oils will over time damage the mirror coatings so i'm weighing that against the potential of damaging mirror during cleaning.

The finger prints from my own stupidity have been on there for a month and I have no idea how long the other little finger prints from the previous owner have been on there.

I'm considering the Isopropyl spray at a sharp angle or I'll follow instructions similar to those posted by Malcolm.

wish me luck!

[creeksky]

Hi Inertia, I'm just giving a sugestion,would a yellow cloth used to clean tablets screens work? They wipe my tablet to a mirror finish no fingerprints.So you may avoid harsh chemicals.

[OzStarGazer]

A lint-free cloth should not damage it if you are careful.
In the worst case though there are some secondary mirrors on eBay too.

[inertia8]

I'll be giving the isopropyl a miss, just dishwasher detergent and warm water then rinsed with demineralised.

With a glasses cleaning cloth I'd be scraping the dust etc across the mirror, which can apparently cause micro scratches (sleeks?) because house dust will often be from concrete or some such hoo ha. Better safe than sorry.