5.5mm Bresser 'Plossl' Disassembly

[Mak the Night]

 These are a five element design with a 60° AFOV. The 5.5mm appears to have a 1-1-3 configuration.

I'm guessing not an Astroplanokular.

[Alan White]

1-1-3  is that not 1-1-2 you show?

[Ricochet]

I can't make out the fifth element in those photos either. The barrel says 5 element though so I guess it must be somewhere.

[Mak the Night]

21 minutes ago, Alan White said:

1-1-3  is that not 1-1-2 you show?

I'm fairly convinced the first two are single convex lenses, so I assumed the last group is a triplet. The whole range is supposedly five element.

[Mak the Night]

12 minutes ago, Ricochet said:

I can't make out the fifth element in those photos either. The barrel says 5 element though so I guess it must be somewhere.

The last element is probably a triplet.

[Alan White]

Just now, Mak the Night said:

The last element is probably a triplet.

I could not see from the picture properly, may be my screen.
 

[Mak the Night]

Just now, Alan White said:

I could not see from the picture properly, may be my screen.
 

I thought it looked like a doublet when I first saw it. The first, thicker glass, part of the element must be a doublet.

[Alan White]

Makes you appreciate how small the glass is in such an eyepiece.

The image showing the lenses next to the aluminium section is very clearly showing as a scale.

[Mak the Night]

2 minutes ago, Alan White said:

Makes you appreciate how small the glass is in such an eyepiece.

The image showing the lenses next to the aluminium section is very clearly showing as a scale.

It's only the size of a regular Plossl, so it's a fairly small eyepiece anyway. I originally bought it for my ST80, a few people told me that as an Astroplanokular it wouldn't be too good on an f/5 scope, but it's actually quite good. 

[Mak the Night]

I'm not a mathematician or an eyepiece manufacturer but it definitely states that there are five lenses in three groups.

https://www.telescopehouse.com/eyepieces/bresser-eyepieces/bresser-60-plossls/bresser-pl-5-5mm-60-31-7mm-1-25-inch.html

The first two lenses look like single convex lenses to me. As there are two of them and there are five lenses in total it would be logical to assume that the last group was a cemented triplet. But, as I stated earlier, I'm not a mathematician or an eyepiece manufacturer.

Question: How many beans make five? lol

[YKSE]

2 hours ago, Mak the Night said:

I'm fairly convinced the first two are single convex lenses, so I assumed the last group is a triplet. The whole range is supposedly five element.

I'd propose a simple method which might eliminate the guess work: Shine a flashlight through each of the lens(es), if you see two reflection spots, it's a singlet, three spots= doublet, four spots=tirplet.

[Mak the Night]

1 hour ago, YKSE said:

I'd propose a simple method which might eliminate the guess work: Shine a flashlight through each of the lens(es), if you see two reflection spots, it's a singlet, three spots= doublet, four spots=tirplet.

I tried this with a white light and a red light torch. I saw a lot of spots on all of them & eventually spots before the eyes. I must be doing it wrong. Funny, because I was full of beans this morning. 

Although, on closer examination, I can quite plainly see a line that appears half way in the first, larger part of the bisected outer surface of the group. Which could very well be two cemented lenses also cemented to the third convex lens at the bottom of the group. So, I reckon five beans make five beans. Of course, feel free to purchase one of these and investigate it yourself. It'll cost you 43 beans though lol.

[Mak the Night]

 +   +  = 5

[N3ptune]

Lol

I like to take a few merguez saussages which I cut in slices then cooked this in a pan. Then I add the Heinz tomato beans with some extra tomato ketchup, parsley and a bit of pepper.

I eat that with bread and cheese It's very good comfort food. Obviously this meal will cause serious gas problems the day after.

==================

LOL for the Beanz + beanz + Beanz heheh good one.

 

 

[Mak the Night]

3 minutes ago, N3ptune said:

Lol

I like to take a few merguez saussages which I cut in slices then cooked this in a pan. Then I add the Heinz tomato beans with some extra tomato ketchup, parsley and a bit of pepper.

I eat that with bread and cheese It's very good comfort food. Obviously this meal will cause serious gas problems the day after.

==================

LOL for the Beanz + beanz + Beanz heheh good one.

 

 

Sounds like great comfort food! But, yeah, expect flatulence lol. 

[Ruud]

It looks a bit like a Kellner II or a Bertele, but it's neither, and it is totally unlike a Plössl. Super marketing though.

Interesting post!

For anyone who doesn't have it yet: Lord-Eyepiece-Evolution-Tree.PDF

[Mak the Night]

2 hours ago, Ruud said:

It looks a bit like a Kellner II or a Bertele, but it's neither, and it is totally unlike a Plössl. Super marketing though.

Interesting post!

For anyone who doesn't have it yet: Lord-Eyepiece-Evolution-Tree.PDF

I think the term 'Plossl' has been overused by marketing. I suppose I can see why Bresser decided to describe this as an advanced Plossl design as it does physically resemble a small Plossl. 

Thanks for the PDF it looks interesting. I really expected this eyepiece to be an Astroplanokular or some form of Erfle, it seems to be an original design though. I use it in short tube achromats when I want a bit of magnification for certain DSO's. As it isn't used a lot I like the fact that it's small and easily carried in my bag. It's also well made, almost certainly JOC glass and with a smooth chromed brass drawtube. It feels like a quality EP.

[Ruud]

I was wondering why you'd show that particular part of the tree (and distracted by the Televue Wide Field) but now I see there is a Mod. Bertele in the view as well. The Bertele that I thought was similar to the Bresser is elsewhere on the chart, among the Kellner derivatives. Here:

Like some others, I see two singlets and a doublet.

On the chart, btw, the number ε denotes the eye relief. If ε is 0.87 the eye relief is 0.87 times the focal length. Theta is the field of view , the position of the field stop is shown, and to the right in each diagram a small segment indicates the exit pupil.

I have a Televue Wide Field. It's a very crisp eyepiece but it has enormous pincushion distortion. Anything round has to stay in the centre because at the edge everything stretches out ridiculously. TV didn't sell it very long. It was replaced by the Panoptic.

For people who take an interest in Lord there is also this:  http://www.brayebrookobservatory.org/BrayObsWebSite/BOOKS/EVOLUTIONofEYEPIECES.pdf 

[Mak the Night]

I think there are similarities with the 15mm GSO SuperView, which I suspected of being a Bertele as it has four elements in three groups.

Similar to the Bresser there seems to be a 1-1-2 configuration.

Above are the two singlets and doublet of the 15mm SuperView. Another eyepiece I can happily use in an f/5 refractor. 

Above is the field lens of the 5.5mm Bresser. The convex part faces out of the eyepiece. I'm convinced this is a triplet, although there are those here who refute it, which is interesting as they don't provide any proof of their own to show otherwise. Possibly a classic case of CAIS (Cranial Anal Interface Syndrome). The group has an obvious division towards the convex field end, but the inwards facing side, which is flat , shows evidence of a further lens division making three in all. Neither of my degrees are in mathematics but I would assume that makes the final element a cemented triplet. I've examined the other two lenses as closely as I can and there's no visible indication that they aren't single lenses.  I wonder if this idea of 1-1 single convex lenses followed by a doublet or triplet is some sort of newer eyepiece evolution. And, if so, how many modern eyepieces actually employ this configuration?

[YKSE]

On 2018-02-07 at 23:32, Mak the Night said:

I tried this with a white light and a red light torch. I saw a lot of spots on all of them & eventually spots before the eyes. I must be doing it wrong. Funny, because I was full of beans this morning. 

Maybe I didn't use the words correctly. When typing "shine through", I was thinking of looking through an eyepiece, the right word here might should be shine at the lens(es), and look at the lens(es). Not shine nor look at side of a lens.

[Mak the Night]

1 hour ago, YKSE said:

Maybe I didn't use the words correctly. When typing "shine through", I was thinking of looking through an eyepiece, the right word here might should be shine at the lens(es), and look at the lens(es). Not shine nor look at side of a lens.

Possibly. To be honest I examined these lens elements every which way I could. With and without magnifying glasses, table lamps, torches and at as many angles as I could. I looked through them, at them and against different backgrounds. 

I could see no evidence for either of the first two lenses being anything other than singlets. The third element does provide evidence that it is a triplet though. It isn't immediately apparent, but it is there. 

Of course, Bresser may be telling porkies about the number of lenses in the eyepiece, but I don't see why they'd do that. 

What intrigues me is the similarity to the 15mm GSO SuperView which has two single convex lenses followed by a doublet. 

 

 

Hill of beans.

[orion25]

LOL!

[Mak the Night]

8 minutes ago, orion25 said:

LOL!

We few, we happy few, we band of brothers;
For he to-day that sheds his blood with me
Shall be my brother; be he ne'er so vile,
This day shall gentle his condition;
And gentlemen in England now a-bed
Shall think themselves accurs'd they were not here,
And hold their manhoods cheap whiles any speaks
That fought with us upon Saint Crispin's day.

~ Henry V, in Act IV Scene iii 18–67.

[Ricochet]

17 hours ago, Mak the Night said:

I'm convinced this is a triplet, although there are those here who refute it, which is interesting as they don't provide any proof of their own to show otherwise. Possibly a classic case of CAIS (Cranial Anal Interface Syndrome).

I suggest you re-read the thread. No one is refuting what you have said. You have posted some photos that are not clear enough for us to see for ourselves and so we are trusting that what you say is correct. At this point I think you owe everyone else an apology.

[N3ptune]

Maybe they installed a doublet and advertise has a triplet. They do that occasionally has  "the Chinese hard drive scam", this is one example bellow.

They install a small USB key inside a HDD enclosure and they sell it the price of a HDD. This scan could work with the older generations...

http://blog.gsmarena.com/how-do-you-spot-fake-chinese-usb-hard-drives-well-you-take-them-apart/