Televue 12mm Nagler for sale - SOLD

[Argonavis]

Televue Nagler 12mm

excellent condition

a supurb eyepiece

2"/1.25"

in original box

$420

[Argonavis]

Price reduced to $380 including registered post.

BinTel new price $475

[AstralTraveller]

Do you know why the 12mm is so much more expensive than the 11mm and 13mm? Surely it can't just be the 2" barrel.

[Argonavis]

It can, actually. To quote Roland Christen (a top optical designer and worker), there are 4 things that determine the cost of an eyepiece:

1. degree of polish
2. type of coating
3. length of production run
4. size of the glass

1. Polish for twice as long, minimum, as it takes to get the grey out, that is the rule of thumb in the industry for a good deep polish. This is the Zeiss standard, and they don't deviate from it. Take twice as long, costs twice as much. You can see where it is possible to shave off some cost. A manufacturer will say, lets see if they'll notice if we only go 50% longer? NA! They'll never know the difference. Lets see if they will notice if we only go 25% as long? NA! they'll never see the difference. Lets see if ... etc. No, they'll never see the difference, BUT you will be celebrated all day long and praised for offering the eyepiece for LESS MONEY, right?

Is it necessary to polish for twice as long? The answer is yes, since below the fine ground surface is a thin layer of sub-surface damage that cannot be seen, but shows up later after the glass undergoes the coating process where it gets heated to 600 DegF. It puts ever so slight haze into the optical path.

2. Most eyepieces, including most premium eyepieces, do not have an efficient multi-coating on all surfaces, and some are only multi-coated on one surface. It goes like this - as the lenses come off the production line, they are multi-coated on production coating machines, without regard to glass type or index. This results in a nice rainbow of colours (reinforces in the purchaser's mind that, by golly, I got a real multi-coated eyepiece here).

Unfortunately, that rainbow tells me right away that the coatings are not optimal, just average, and, believe it or not, sometimes they can be worse than no coating at all. Zeiss coats each glass according to it's own unique index value. It requires constant monitoring by skilled technicians, as well as adjusting the formula. The other thing is the type of evaporant that is used. Some produce a so-so coating, other, more expensive materials produce a very high transmission coating. High index glass is the hardest to coat properly, it wants 4 or even 5 layers, whereas pretty much all the popular eyepieces I've seen use typically 3 layers, or even only one layer for very high index flint elements. This results in a yellowish tint to the image, and a blueish glow coming out of the eyepiece.

3. The longer the run, the lower the cost, because setup and tooling can be amortized. The more popular an eyepiece is, the lower will be it's production cost. How do you make it popular? Make it cheap! How? See part 1, and 2.

4. The larger the glass element, the less number you can put on a multiblock.
Lenses are made on multiblocks, 20, 30, 40 at a time. If you can make 100, cost goes way down. Multi-blocks have finite size limits, so the smaller the element, the lower the cost. However, there is a limit to the size of the blocks. The thing that governs the size of the block is the lens radius. If the radius is 4", then max block size is about 3". This means that short focal length lenses end up on smaller blocks than longer ones. Longer ones, of course, are larger, thus limiting the number that can be blocked.

So for the same time and money, you make substantially fewer 2 inch eyepieces thatn you can make 1.25 inch eyepieces. It is not only the lower numbers you can batch manufacture, but as well as the higher glass, coating and transport costs. They all add up.

[AstralTraveller]

Thanks for the very informative reply. You certainly justify spending the extra money on quality eyepieces. However I'm still not sure I understand how that works in this case. I'm assuming that polish and coating and production run are constant across the Nagler range. That leaves size of glass. Are the elements in the 12mm larger than the others? If not then we are back to the metal barrel.

cheers,
Dave

[Argonavis]

Beyond what I have posted is all speculative. Only Al Nagler would know his production costs. If you ring Televue (best in the early morning here for late afternoon in New York) you may well end up talking with Al on the other end of the line. You can only ask, he may or may not tell you. He tends to be secreative about the commercial side of his business, as you would expect. But he may give you a reason. He doesn't do email. Alternatively you could post your question on the Cloudy Nights eyepiece forum:

http://www.cloudynights.com/ubbthreads/postlist.php/Cat/0/Board/Eyepieces

I am sure you will get lots of opinions.

Note that the 7mm and 9mm are type VI Naglers, the 12mm is a type IV.

There are differences, as explained on the Cloudy Night review pages:

http://www.cloudynights.com/item.php?item_id=1737

and

http://www.cloudynights.com/documents/naglers.pdf

[TakMan]

PM sent.
Also which version is this 12.

Regards Kyle

[Argonavis]

It is a type IV