When Should You Clean A Telescope Mirror?

Any owner of a telescope will be aware that there will come a time in the life of the telescope when you will need to clean the mirror inside it. Given how expensive telescopes can be, and how difficult it can be to replace parts of them, this can cause some fear! 

Cleaning your telescope mirror becomes a time that is dreaded by telescope owners and space fanatics alike! The reason for this is because cleaning these mirrors is no easy feat and requires extreme care and patience. 

This has led many telescope owners to only clean their mirrors every 5 or 10 years. Some owners actually avoid this completely and deal with the tiny specs of dust that eventually show up! 

But how often do we actually need to do it? And why is it such a dreaded task? 

The mirrors of a telescope are notoriously delicate. They can be damaged beyond repair with so much as a fingerprint mark or a slight bit of pressure from a finger. This makes cleaning them very difficult… especially if you tend to be heavy handed! 

The thing is, telescope mirrors are drone to dust, grime, grease, build-up, and lint. This can wreak havoc on your observation experience, especially if you plan to take photographs with your telescope. 

This can also be made worse depending on where in the world you tend to use your telescope.

For example, if you tend to stargaze on the beach you may find sand particles on the mirrors, whereas if you are in the desert looking up at the happenings on the moon, then do not be surprised if you find some desert dust! 

That being said, whilst mirrors can get dust and other particles on them, this is not generally a huge issue, and the amount that gets onto the telescope mirror is usually only minuscule.

This means that many owners may not even realize that dust and other particles have built up for a number of years! 

With this in mind, it is perhaps not surprising that the common timeframe for cleaning your telescope mirrors is indeed 5 to 10 years.

As it turns out, this is not solely because telescope owners are too scared to touch the delicate mirrors, but simply because they do not need to be cleaned more often than that! 

As well as this, it is worth noting that many experts actually advise against cleaning your telescope mirrors and diagonals. This is because they are so susceptible to damage, even just from some slight pressure from a fingertip or rubbing too hard. 

So, cleaning your mirror every 5 to 10 years is totally acceptable! However, if you feel that even after this tie your mirrors are still looking clean and shiny, then do not feel as though you need to clean them. Unnecessary cleaning should be avoided at all costs! 

On the other hand, if you feel they need to be cleaned more often because of very noticeable dust and other issues, then go ahead and clean the mirrors to your heart’s content. Just ensure to follow our guide below for cleaning diagonals! 

How do you clean the diagonal of a telescope?

Cleaning the diagonal of your telescope requires lots of care and gentle handling. The mirror of a diagonal is usually a high efficiency mirror, and as such, it is super prone to scratches and tarnishing. 

When dust or any abrasive materials or substances touch the surface of a diagonal, permanent damage can be done. Therefore, it is very important that you take extreme care and follow our instructions carefully. 

To avoid any mishaps, you should only clean the diagonal mirror if and when it is absolutely necessary. It does not need regular cleaning and upkeep as this can cause more harm than good. 

As we have mentioned earlier in the article, this is one of the reasons why many people will never clean their telescope mirrors! Most people will only do it every 5 to 10 years or so.

They are too scared of causing destruction to their very expensive telescope and the hard to replace parts such as the diagonal. 

Guide for cleaning a telescope diagonal 

If you have come to the realization that it is absolutely essential that the diagonal of your telescope gets cleaned right now, then you can follow our steps below. Our guide gives you all the information you will need to make sure you do this as efficiently and carefully as possible: 

1.Use a clean, dry rubber syringe from the drugstore to blow air onto any specks of dirt, dust, and grime on the surface of the mirror. 

Do not touch the mirror with your fingertips and only blow small amounts of the syringe air onto the mirror at a time.

Do not be tempted to blow at the diagonal with your own breath as small amounts of saliva will likely land on the diagonal and cause damage. 

2. Using a lens cleaning wipe, add some 90% isopropyl alcohol and make a sort of cleaning pad.

If you cannot get isopropyl alcohol then you can use Methanol. This will be used to wipe off any grease and other residues that could not be blown away by the syringe. 

3.Very gently wipe the pad across the surface, ensuring you do not put any extra weight onto the pad. Do not rub or touch the diagonal in any way. 

4.Do not be tempted to use any glass or window cleaners as this could cause irreparable damage to your diagonal.

The reason for this is because of the high water content in them. As well as this, you should never use actual water or soap on any part of your telescope. 

5.If there are any marks on the mirror or if there is a residue left on the diagonal do not attempt to rub it off. Instead, you should leave it alone. Small marks should not affect your viewing experience. 

Gordon Watts
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