Contaminated Tak APO / UK Servicing?

[NigeB]

Hello All,

I'm hoping that someone may be able to point me in the direction of somewhere capable of servicing Takahashi apochromats in the UK.

I have a Takahashi TOA 150 which has been unused for several years due to house moves. I unwrapped the telescope last month and found that there is some form of contamination inside the lens assembly, which appears as a faint haze under flashlight illumination. Images don't appear obviously affected, but I can tell that there is some scatter from the layer when the moon is just out of the field.

I know that Texas Nautical Repair Co. in the USA can service Taks, but it will cost a fortune to ship from the UK and back again. One UK dealer has said they'd be willing to "have a go" but that doesn't exactly fill me with confidence...

Does anyone know of a place that is able to undertake this kind of work, ideally in the UK but failing that, somewhere in Western Europe?

Thanks

Nigel

[Alien 13]

Do you have any pictures of the haze i would be worried because it could be fungus growth not good as it can eat the glass. I would recomend subjecting the scope to lots of daylight (UV) as this can slow or sometimes stop the growth getting worse. I cant offer any advice on servicing but im sure someone will come along.

[NigeB]

Do you have any pictures of the haze i would be worried because it could be fungus growth not good as it can eat the glass. I would recomend subjecting the scope to lots of daylight (UV) as this can slow or sometimes stop the growth getting worse. I cant offer any advice on servicing but im sure someone will come along.

Hi Alien 13,

Thanks for your reply. I've taken an image of the problem, and posted it at the URL below. On very close inspection (having carefully cleaned the front of the objective) it appears that this is made up of particulate material. The majority of the haze seems to have been a reflection of contamination, now removed, from the exposed surface of the objective, and the material that remains is definitely inside the optical assembly.

I took the image with an LED torch shining on the front of the telescope to illuminate the particles, and using a v. fast camera lens, so the depth of field is very shallow and effectively the only plane that is in focus is (what I believe to be) the outward/incident surface of the second lens in the optical train, isolating the particles I'm worried about. 

https://www.dropbox.com/s/ljr0b7gh3o6yjpx/IMG_8941.jpg

Now, I'm aware that this is basically the "flashlight test" which can show up contamination on almost any optical surface (the problem looks worse in the photo than it does to the unaided eye). But it's the fact that the stuff is *inside* which concerns me. I know that dust is very mobile, but I'm surprised that, if this is dust, it can get inside the cell in this quantity.

Thanks again,

Nigel

[Space Dragon]

If you can find a contact for Neil English, [he has his own website dedicated to refractors, as you may well know]  he uses an optician in the UK to clean his lens cells, in whom he has absolute confidence.

I'm sure he'd be only too glad to be of help.

Cheers

[Peter Drew]

Cleaning an objective is no big deal, you could do it yourself. The big deal is separating the components of a triplet and being able to reassemble them correctly to maintain the original performance, the adjustment and collimation of the individual components is a tricky business. 

[NigeB]

If you can find a contact for Neil English, [he has his own website dedicated to refractors, as you may well know]  he uses an optician in the UK to clean his lens cells, in whom he has absolute confidence.

I'm sure he'd be only too glad to be of help.

Cheers

Thanks for that pointer Space Dragon, I've sent Neil an email.

(Thanks Peter also; yes, it's precisely the reassembly and collimation job for which I'm seeking a solution).

[NGC 1502]

I think that contacting Neil English is the best idea.  He's the person that springs to mind (in the UK) best placed to offer advice.

But looking at the pic, it's hard to tell if the dust is between the lens elements, or on the inside of the innermost element.  If the latter, then much easier to sort out, as the lens elements don't have to be disturbed, maybe the lens cell comes off as a unit for cleaning the inside of that back element, far less challenging.

Another option is to live with it, I'll bet the scope would be great if left as it is.

Hope you reach a satisfactory conclusion, Ed.

[NGC 1502]

Oops sorry, just read post # 3 again.  If the dust is indeed between the elements, then part of my post # 7 does not apply.........................

As already said, hope you sort it, Ed.

[Alien 13]

Thanks Nigel for posting the picture it certainly looks like dust so a big phew from me i can only agree with the other comments here about lens cell dissasembly it needs expert hands.

The comment about how dust gets in is a problem ive faced with camera lenses (pressure difference when focusing, temp changes) it always gets in between the glass elements and in most cases has no effect on the image.

Alan.

[NigeB]

Hello Alan, Ed,

Many thanks for your posts. I'm going to wait and see if Neil English has a contact that can handle this kind of disassembly / realignment job, but failing that I will try to forget about it! As you've both indicated, it's unlikely to make a tangible difference to the performance of the instrument. Better to view it starlight from the sharp end rather than torchlight from the blunt end! I appreciate your responses to my post.

Thanks

Nigel

[HD-AP]

Hi

I beleive neil english uses ES reid ,former optician at AE optics luton along with jon owen and jim hysom.

Es reid would be my choice for such work ,he has worked on some very high end projects ,has his own test lab/workshop,and really knows his stuff.And has dismantled and refigured large and small triplet apo lenses in the past.

[Plantins]

As mentioned above, ES Reid is the man to contact.