!?!?! grease on objective !

[Wavytone]

Just took a good look at the objective of my 102ED in the daylight... it had some dust particles and streaks of something on the inside of the objective... so I took the objective off for a closer look.

Erk. The objective cell has a nasty sticky grease all over it on the inside surfaces and it has contaminated the objective. I've already found neither Bintel lens cleaning liquid, warm water and detergent nor Windex will shift this goo. All of these are basically ineffective on grease, anyway.

So... is the next step to pull it apart and wash the elements in a more serious solvent for grease, such as mineral turps ?

Pulling it apart isn't going to be easy either the retaining ring is stuck fast. Looks like it might be back to Bintel.

Or is there a better way ?

[GrahamL]

I'd stay away from petrolem based solvents such as turps .

Back to bintel isn't a bad idea ,, how old is the sope ?

[anj026]

Talk to Bintel directly before going any further. They are very good at advice for this sort of thing in my experience. Don't disassemble the lens without first trying other options. Be patient and stay calm!

[Wavytone]

It's only 2 months old.

What I thought were a few flecks of dust on the inside side of the objective turned out to be grease. Also the inside surfaces of the objective cell were covered in it, along with a few inches of the tube.

I can understand why someone might consider greasing a fine aluminium to aluminium thread (to stop it binding). I can even grasp the possibility they intended the grease as a means of trapping dust inside the tube (some DSLR's have a square of what resembles fly-paper for this reason).

But to put it anywhere near the objective...

And the retaining ring is hideously overtightened, I'm shocked the glass has not fractured.

Anyway off to Bintel now as its now fogged with moisture.

[Ian Robinson]

Job for some isopropyl alcohol maybe ??

Turps might also wreck the antireflection coatings .... I'd try a small drop on a contaminated part to before applying it more generally.
Needs to desolve the stuff but not lift the coatings or etch the glass.

I wouldn't risk trying to cleaning myself , if it's only 2 months old , has to still be in warantee , send it back to the seller to be rectified or replaced.

[Wavytone]

The Bintel stuff is isopropyl alcohol. With the Bintel stuff it just smears which suggests this stuff is a petroleum based grease - or possibly vaseline. The alternatives I know of are petroleum-based solvents (mineral turps or petrol), 100% acetone, or a run through a dishwasher.

At this point I suspect is stuffed anyway and probably means a new objective.

Someone makes nice glass - and I bet it isn't Orion:

The rest - quite literally from the lens cell onwards - is crap:
- the overtightened lens cell,
- the use of a very nasty grease near the objective,
- the condition the focusser was in (overtightened to the point the bearings were wrecked), and
- the bent screws on the mount (also Orion)

suggests to me Orion is actually doing no more than assembling the metalwork and sticking their name on it, and they have NO F'ING IDEA what they are doing during assembly. If they had made the glass they'd have half an idea what they are dealing with - and some respect for it, which they clearly lack, suggesting they didn't make the lenses.

[bmitchell82]

I think you got a "Friday" Scope that was put together by the apprentice Fred.... I wouldn't pull the scope apart, ide be sending it back as is so they can sort it out.

Basically if you start putting some harsh petrochemical solvents on your len's kiss that !@#! good bye use them to scare the crows away by chucking at them.

But i guess its your money do with it as you will.

[astro_nutt]

How about this?...collect some of the grease from inside the tube and smear it on a piece of glass..try a few methods of cleaning on this first before doing your lens!
Cheers!

[Ian Robinson]

You bought it new - you have every right to expect the optics to be PERFECT.

Get onto the blower and tell who ever sold it to you that you have found a problem and it's going back to them immediately to be repaired or replaced under warantee as it is defective.

Might be that the lens has oil in the gap and this leaked - this is bad manufacture and rotten quality control.

[gregbradley]

Acetone may be the go. I imagine turps would leave a stain and I have never heard of anyone using turps on optics. It sounds pretty harsh and also likely to stain. It may damage the coatings.

Acetone is something you can use. As I recall it was recommended by RCOS to clean their mirrors with - one approach.

I also think it is a good idea to check it out on something else before trying it on your lens which you need to be certain before potentially wrecking your lens sort of thing.

Greg.

[Wavytone]

Well it's cleaned and re-assembled now. In case anyone else needs to do this you will need:

- a lens spanner (see below),
- a packet of Johnson cotton pads (the things girls use to remove makeup)
- industrial acetone from Bunnings ($10 buys half a litre, chemists charge a fortune),
- a wooden clothespeg,
- a pencil,
- a drinking cup,
- a couple of very well-washed linen teatowels for the work area.


I made a lens spanner to open the cell using 2 screwdrivers and a block of wood. I found a pair that happened to have straight blades and shafts which were a tight press fit in a 5mm hole (see photo). I used a pair of calipers to measure the cell and get the spacing of the screwdrivers exactly right.

- Cover a work area with the tea towels to provide a soft clean surface such that the elements can sit on it and not pick up any dust.

- Using the lens spanner, loosen the retaining ring and remove it. The lenses will stay in the cell. I would not recommend trying to hold the cell with one hand and the spanner in the other, for two reasons - one slip and the blades will scratch the lens; secondly if you drop it this will be the end of your lens.

Instead I clamped the lens cell to the bench and used both hands to gently place the spanner in position and rotate it using both hands.

- Using an inverted cup and a couple of pads to support the lens by the centre well off the bench top, unscrew the cell, then gently ease the cell off the lens, making sure you do not rotate it, and keeping both elements of the lens together.
- The lens elements are airspaced, with a metal spacer ring between.
- There are a series of 4 pairs of holes around the periphery of the lens cell. Orion forced some sort of waxy gunk into these which keeps the lens elements from shifting laterally.
- Once the cell has slid off the elements be careful not to rotate it as I am fairly sure the gunk above is important to keep the lenses precisely centred with respect to each other.

- Using a cotton swab dipped in the acetone, swab a small patch on the side of both lenses to clean off the black stuff they have coated the edges with, without disturbing the alignment of the lenses and the cell.

- Using the pencil, place a set of lines on the edge of the lenses and the cell, so that you can get these marks aligned again when you reassemble it. I use a group of 3 lines so that if one rubs off during the cleaning there are still two more.

Make sure you also put a "V" mark on the side of each lens so that you can tell which way round the elements belong. The convex element is nearly symmetric so it is quite hard to tell which side is supposed to face the focal plane.

- Now you can lift the top element off. Using a wooden clothespegs instead of your fingers to grab a cotton pad, dip it in acetone, then swab a lens surface. This will save your fingers from the acetone. It should come clean. Repeat for both sides, then do the bottom element, and put both elements to one side on the tea towel.

if you want to clean the edges note there is more black gunk that will come off. Just be careful not to wipe the pencil marks off.

- Clean the cell too, mine was greasy.

- Reassemble the cell, ensuring the elements are aligned and aligned in the same way they were in the cell, using the pencil marks. Using the spanner to close the retaining ring it should be firm but not tight; otherwise the lens will be overloaded and the glass may fracture in cold conditions - aluminium shrinks more than glass. Mine was, in my view, dangerously tight in the first place.

The acetone in my case dried off almost instantly leaving a clean surface.

Looking at the city lights the lens image is OK, have to wait for the skies to clear for a star test.

PS grease is a non-polar molecule and getting it off requires either a non-polar solvent or else a caustic solution that will turn it into soap, which washes off (as in a dishwasher). For non-polar solvents acetone is one obvious one but paint thinners are also likely. Turps I tried on window glass - it won't dry clean, but thinners do. Thankfully not needed.

The pale green coating on these lenses is almost certainly zinc cryolite - OK in itself, but what bothers me more is how well the coatings have adhered to the glass underneath, or not; if the solvent gets under the coating it will come off in patches.