Corrector Question

[75BC (Brendon)]

I have a couple of questions with a back story I’ll TRY to keep short.

The other day I was trying to remove a few bits of hair and crap that had ended up on the corrector plate of my scope. Now, I know all about cleaning only when absolutely necessary. I have a severe case of OCD and made every mistake imaginable with my previous scope. Upon buying my new CPC1100 last year I told myself I was going to have to deal with my condition or end up making the same mistakes with a far more expensive piece of equipment. So far, I have done pretty well, as before I would have had the thing in pieces cleaning every possible part.

Anyway, while very gently brushing the stray bits with my very soft brush I’ve spread a blob of (unseen at the time) something sticky /greasy. My lovely wife went to Jaycar yesterday to get me some isopropyl alcohol and the gentleman there asked what it was for. My wife said it was for a telescope and his reply was that IPA should not be used on glass. Although I was pretty sure this was not correct I quickly re-read some online tutorials on cleaning and found on the Starzonia site a comment about IPA possibly staining newer type coatings on corrector plates. https://starizona.com/acb/basics/using_cleaning.aspx

So finally my questions.
1. Is the Starzonia comment true about newer coatings being stained by isopropyl alcohol?
2. More importantly, I’m using cotton wool with a mix of about 50 / 50 IPA (99%) to distilled water and the spot is being quite stubborn to remove, smearing all over. I’m having to go over it quite a few times (very gently). Is going over it so many times doing any damage?

in advance.

[iborg (Philip)]

Hi

I have no idea about IPA and corrector staining, but, if what you are trying to remove is indeed a greasy substance then increasing the proportion of IPA should do the trick.

I would have started with 100%, but, I do not this to be correct.

I will mention that if it is a silicon based greasy substance, this may still not work. I just don't know.

Good luck

Philip

[75BC (Brendon)]

Hi Philip,

The reason I’m using a 50 / 50 mix is because of what I read about the staining. I thought better to start with a milder solution just in case.

It is coming off, it’s just taking a lot of going over as it seems to smear rather than simply being removed.

[Camelopardalis (Dunk)]

I've used a 50:50 mix before and it hasn't stained, but you need to use a very soft cloth. It's the water content that does the staining, but it cleans right off.

[croweater (Richard)]

This may help Brendon. http://www.televue.com/engine/TV3b_page.asp?id=103.

[75BC (Brendon)]

Thanks for your replies Dunk and Richard.
The gunk is coming off using the 50 / 50 mix. It's just taking a bit longer than I thought. I might up the strength a bit and see how it goes.
That TV site I saw for the first time when I was checking I had everything right with the IPA. That was encouraging.
I haven't seen evidence of staining yet but stopped to check what people here thought and it was getting late.

[JD]

I don't know if this helps much - that Tele Vue site information was good - but if telescope lens coatings are anything like camera lenses, you shouldn't have any problems. Coatings on camera lenses are usually applied at quite high temperatures, which is one reason why it's hard to get them replaced. You risk shattering the glass though thermal shock. I assume telescope coatings are the same. The point is that, as long as there are no foreign particles in that residue and as long as you don't press too hard, you should be okay. The vibe isn't good but the risk isn't as high as you think. They're pretty tough.

My experience is with high grade camera lenses (it's part of my job) and I have yet to (knowingly) damage a coating through cleaning.

One practice which works is to fold lens tissue in one direction until you get a sort of roll about the size of a cigarette. Then you rip it in half and it leaves a very soft but firm part to clean with. It's actually firm enough that you can use quite a bit of pressure. For pretty obvious reasons, I never really pushed all that hard.

[janoskiss (Steve H)]

TeleVue recommends cleaning their EPs with Windex. Even though it's TeleVue, I was still sceptical at first but eventually gave it a go and it does work very well. Been using it on EPs for many years and no problems. I've also cleaned the corrector plate of my Mak with it a couple of times (once every few years).

Most of the time I use just a blower or compressed air gun on low pressure. Occasionaly a soft bristled lens cleaning brush. And rarely Windex and cotton balls. Of course I don't spray the Windex directly onto the EP or the corrector plate but onto the cotton balls (if too saturated, transfer the cleaning fluid from one ball to another fresh one). And of course, always 'easy does it', and change the cotton often. Once with the Windex moistened cotton and once with dry should do it and leave no residue.

[75BC (Brendon)]

Thanks JD and Steve.

Thank you to everyone who replied. Seems I was being a bit paranoid (cautious). Finally got round to finishing cleaning it and came up good as new. Used a 70:30 IPA to Distilled water mix and lots and lots of cotton wool.

As I only really cleaned the one area it looks a little funny. But I’ve now learnt (from the experienced folk on here) if I spend more time looking through the other end, I won’t notice it.