Seben Zoom 8-24mm, Cheap Zoom Eyepiece

[Ricochet]

6 hours ago, Dave In Vermont said:

If you have a specific question about a specific eyepiece, you could write it up and send me a PM. I'd be happy to pass it on. The schematics of these particular 8 - 24's, perhaps?

The schematics aren't really enough in this discussion. You would need someone who is able to determine the glass types used for each element and coatings used on them.

I think it is reasonably safe to say that everyone is happy with the idea that the Seben/Skywatcher/Celestron/Vite zoom is one eyepiece and that the Vixen/Tele Vue zoom is another. What you have said is that the only difference between the two zooms is the use of lanthanum glass for a single element. Now I haven't had the opportunity to look through a Vixen/TV zoom but I have looked through a Skywatcher (I assume as it was unbranded) and i find it difficult to believe that the difference between the optical quality of the zoom I looked through and the reputation of the Vixen/TV is down to changing just one element.

[Stu]

9 minutes ago, Dave In Vermont said:

From what I see using my F5 ST80, my Vixen and Hyperion 8 - 24mm Zooms work just fine.

It's interesting, why don't we all just use ST80s and Seben zooms then, are we all just fools?

Are you saying that the Hyperion Zoom is the same as the Seben clones? I don't think so? You are also discussing the Vixen as if it were the same with just the 'minor addition' of Lanthanum glass, which you could say is the same as comparing an ED80 to an ST80 with just the minor addition of FPL53 'glass'. One scope I would be very happy with, the other less so.

4 minutes ago, chiltonstar said:

(I prefer the word "similar" to "identical").

I suspect this is nearer the truth Chris. I'm sure there are detail production differences between the different brands depending upon exact spec and cost such as edge blackening, QA etc. I'm sure someone takes the bottom 20% of eyepieces which don't get scrapped!

Personally I just wish @John would stop being so lazy and actually show an interest in eyepieces and learning about them..........

 

........oh, hang on a minute.....

[Bigwings]

Tried one in my Dob (f4.7).

She let out a groan and demanded I buy her a Baader 8-24.

She is happy now. 

[Stub Mandrel]

I know someone who imports machine tools from China.

Everything Dave says is true with respect to lathes, milling machines, grinders etc. etc. and all the tooling that goes with them.

There are some important points to know, though:

If you go to the good manufacturers (and they can be very good) you can specify the components and QC you want for your product. You might see what appears to be the same lathe from a dozen of more suppliers (yes this include many big US, Japanese and German brands) and each one is different in detail. Some of the differences (QC, circuit boards, bearings) are invisible to the average buyer. I'm sure this is exactly the situation with Vixen's special glass.

An upside of this is that the QC demanded by the bigger buyers can trickle down. While cheap EPs may not get expensive glass, the factory will use the same process to make all the focusers, for example.

It's also important to know that (for machines at least) there may be several factories making a similar product that has evolved from the same original design. These could be iMax B5 battery chargers or mini lathes. If you don't know the supplier and trust their  QC you could end up with anything.

BUT, and it's a big but, what about all the really cheap versions to be found? The Chinese factories never throw anything away - if a batch of parts/machines/eyepieces fail QC someone's cousin/friend etc. will pay a pittance for them and they get dumped on the market. Its not like Europe or the USA where they would get scrapped or trashed deliberately. there are even people who make machine tools by assembling overstocked spares - ones that may even be meant for different manufacturer's versions of the same basic design, sometimes creating strange hybrids or resulting in batches of total basket cases going on the 'low end' market.

Lots of very foolish people judge all Chinese manufacturing by the cheap crap on ebay "I'll never buy Chinese made rubbish" they tell someone over their iPhone... truth is , if you know what to look for and where to buy you will do OK.

Also, buy big items from reputable dealers. these days they are usually cheaper than eBay or Amazon (look at the prices of new scopes on eBay!) plus you get after sales service, a genuine warranty and backup spares.

[Nyctimene]

My Seben 24-8 zoom works quite nice in my smaller f/5 scopes, whereas my Baader Hyperion Zoom MkIII can be used up to the 8" f/4 Hofheim traveldob. I'm pleased with the Seben - rather small, lightweight, good for any grab-and-go set, and for a very reasonable price. No worries about damaging or losing one, when doing outreach, or observing early (with some wine or single malt remnants in the blood circulation....).

 When I want perfect  on-axis views, I always return to my Orthoscopics.

Stephan

 

[Dave In Vermont]

6 hours ago, Stu said:

It's interesting, why don't we all just use ST80s and Seben zooms then, are we all just fools?

Are you saying that the Hyperion Zoom is the same as the Seben clones? I don't think so? You are also discussing the Vixen as if it were the same with just the 'minor addition' of Lanthanum glass, which you could say is the same as comparing an ED80 to an ST80 with just the minor addition of FPL53 'glass'. One scope I would be very happy with, the other less so.

I suspect this is nearer the truth Chris. I'm sure there are detail production differences between the different brands depending upon exact spec and cost such as edge blackening, QA etc. I'm sure someone takes the bottom 20% of eyepieces which don't get scrapped!

Personally I just wish @John would stop being so lazy and actually show an interest in eyepieces and learning about them..........

 

........oh, hang on a minute.....

'Similar' vs. 'Identical?' I was referring to the mechanics. Not the optics - the lanthanum makes a great difference in this respect. Which explains why I have the Vixen.

No, the Baader Hyperion is an entirely different animal. I merely mentioned that I have both of these brands. The Baader is an excellent piece of glass, it's just a bit heavy and bulky to drag all over town with me while already lugging a telescope/tripod.

Shall we start an armed conflict over semantics? I rather think not. Nor do I care to play 'Clyde Tombaugh meets Mr. Hyde' - so I shall retire from this thread.

All I'm trying to say here is that the Seben 8 - 24mm Zoom is a perfectly good zoom-lens. And if I needed another zoom, I wouldn't hesitate to buy same. While a lot of eyepieces and zooms from China used to be of questionable quality, they have improved a great deal in recent years. And that was my point.

Dave

[Stu]

6 minutes ago, Dave In Vermont said:

'Similar' vs. 'Identical?' I was referring to the mechanics. Not the optics - the lanthanum makes a great difference in this respect. Which explains why I have the Vixen.

No, the Baader Hyperion is an entirely different animal. I merely mentioned that I have both of these brands. The Baader is an excellent piece of glass, it's just a bit heavy and bulky to drag all over town with me while already lugging a telescope/tripod.

Shall we start an armed conflict over semantics? I rather think not. Nor do I care to play 'Clyde Tombaugh meets Mr. Hyde' - so I shall retire from this thread.

Dave

These are not semantics, Dave, you can't in one breath say 'Remember - the Vixen differs from the Seben by the lanthanum lens-element, other than this minor addition, they are optically the same beast.' And then the next you are referring to mechanics. It is confusing for those interested in buying.

We were clearly talking about the Seben clones at f5, so then to introduce the Baader implying that they are all ok at f5 is again misleading.

[rwilkey]

The Seben zoom is good because it is not made by Seben, it is a clone of the GSO one as others have said, this ep in no way raises the reputation of this aweful company.

[Mangleworsle]

Don't know if any one has mentioned this but I am lead to believe that GSO products are marketed in the UK as Revelation Astro.

[Mangleworsle]

Having read through the the Posts in this topic I think there is a bit of the old Hi Fi syndrome occurring, ie I have paid hundreds of pounds/Dollars for this it must be good, it has special bits ( in Hi Fi this culminated in having to have the speaker connecting wire the correct way around, cable manufacturers and dealers made a fortune out of this ). Lanthanum has been quote as one of these special bits, but a bit of research will show that it is used by a large number of lens makers in fact every iPhone has a lens with Lanthanum included and so most likely do the rest of the mobile phones, apart from the very basic version. I believe that a lot of these special attributes are nothing more than marketing hype.

Clear Sky's to all

Jim

[John]

4 minutes ago, Mangleworsle said:

Having read through the the Posts in this topic I think there is a bit of the old Hi Fi syndrome occurring, ie I have paid hundreds of pounds/Dollars for this it must be good, it has special bits ( in Hi Fi this culminated in having to have the speaker connecting wire the correct way around, cable manufacturers and dealers made a fortune out of this ). Lanthanum has been quote as one of these special bits, but a bit of research will show that it is used by a large number of lens makers in fact every iPhone has a lens with Lanthanum included and so most likely do the rest of the mobile phones, apart from the very basic version. I believe that a lot of these special attributes are nothing more than marketing hype.

Clear Sky's to all

Jim

Thats a bit unfair on some very experienced observers who have actually compared the various options

When I've posted reviews on here most of the equipment I've been testing has been loaned to me rather than being my own. Easier to be impartial that way

Still, you are welcome to your views of course

 

[Stub Mandrel]

20 minutes ago, Mangleworsle said:

I think there is a bit of the old Hi Fi syndrome occurrin

There's an idea  - put a green coating on my lenses with a felt pen!

[Mangleworsle]

I understand your feelings, but it is something I have come across on numerous occasions, and much to my embarrassment was part of the industry that concocted these things, as an engineer coopted to the marketing department of a well known electronic and optical manufacturer.

For instance Vixen use Lanthanum as a marketing tool, all well and good, but every half decent lens manufacturer uses it to increase the refractive index.

So as you can see I am very sceptical of special claims.

Also I own both the Seben 7.5 - 22.5 mm and the 8.0 - 24 mm eyepieces used in my ST102 F4.9 and a Celesteron 70 / 400 F5.7, both work well, the 80 - 24 being the better as I would expect at this sort of price level.

As for using felt pen on your lenses that's up to you, but I feel that you could have missed the point.

Jim

[billyharris72]

It may be a bit unfair to suggest hi fi syndrome, but you be got to admit this is a hobby where products are often hyped to death on bases that are totally ridiculous. My personal favourites:

* Diffraction limited optics - to my knowledge we have yet to build one of these and (at least for refractors, but almost definitely for reflectors too) it's basically theoretically impossible to do so. Yet we see this in ads all the time.

* CNC machined parts. Yep, CNC, a technology introduced to cut costs by making machines more flexible and reducing the need for skilled labour, with very little loss in manufacturing accuracy relative to using skilled labour and dedicated equipment. Cheap, easy and used to make most metal parts these days (except where very, very high levels of accuracy are needed). But slap it on an add and call it premium.

* Debates about coated, multi coated and fully multi coated optics, as if these actually mean something (there is no standard definition), Bak4 vs BK7 prisms, or apo fpl53 vs 51 glass (without any discussion of the other parts of the triplet, or how they are figured, as if the choice of which low dispersion glass is the most important choice)

These do smack of the aforementioned hi fi syndrome to me ( I say that with all due respect to those who have tested kit and have a view on how it performs- that's a different matter).

Billy.

 

[FLO]

When it comes to materials and manufacturing specifications of eyepieces, we don't know.

This is especially true at the budget end of the market where the same eyepieces can vary significantly batch-to-batch! Eyepieces from the same factory, wearing different badges, are very rarely the same. Not just eyepieces, telescopes too. 

At the more expensive end of the market things are more dependable because expectations are higher and reputations are at stake. Even so variations batch-to-batch can happen. 

[John]

The Seben 7.5-22mm zoom seems to use plastic as a lens material for 2 of it's 3 lenses:

https://stargazerslounge.com/topic/239239-seben-zoom-eyepiece/?do=findComment&comment=2594185

 

 

[Stub Mandrel]

1 hour ago, Mangleworsle said:

As for using felt pen on your lenses that's up to you, but I feel that you could have missed the point.

That was a reference to the hifi craze of paying through the nose for special green pens to 'reduce unwanted jitter' on CDs which was no doubt as effective as apply anti-reflection coatings with a sharpie would be.

I didn't think my original comment needed a smiley, but here's one for you just in case ...

[Stub Mandrel]

5 minutes ago, John said:

The Seben 7.5-22mm zoom seems to use plastic as a lens material for 2 of it's 3 lenses, which is novel:

https://stargazerslounge.com/topic/239239-seben-zoom-eyepiece/?do=findComment&comment=2594185

I think the 8-24mm is a much better bet.

Not unusual at the cheap end of the market!

But as a spectacle wearer I can vouch for the quality of decent polycarbonate lenses (which cost as much for a pair of custom-made multi-coated single-element lenses as a very good eyepiece, yet they have significant CA off axis!)

[Mangleworsle]

Hi Stub Mandrel.

Never came across painting CD's with a green pen I am still mainly big black platters.

Suppose that again comes into the same category as getting you cables the right way round.

Sorry about the humour bypass.

Jim

[Mangleworsle]

As I said earlier i have both and you can tell a difference between the 7.5 and the 8.0, but it's not catastrophic, and possibly is a reflection of price in this case.

Jim

[domstar]

This is the best thread ever. I think I want a zoom now.

[Stub Mandrel]

35 minutes ago, domstar said:

This is the best thread ever. I think I want a zoom now.

The price of Seben zoom EPs has gone up by 30% since this thread started...

[Dave In Vermont]

Not speaking:

 

Seben Zoom

 

Now leaving thread.

[Mangleworsle]

Yep that definitely look like mine.

Just seen on the link above that someone has modified the 7.5 - 22.5 using glass elements and gets an improvement. I think I might get a set of parts and try it myself if it gets scratched.

[Ricochet]

8 hours ago, Dave In Vermont said:

Not speaking:

 

Seben Zoom

 

Now leaving thread.

If you don't mind speaking, what is that showing us? Is that a singlet eye lens, singlet in the top movable section and singlet in the nosepiece? Which lenses are plastic and which glass? Do we know how the Seben 8-24mm zoom compares? I have an AE HFO 8-24mm that has a singlet eye lens, singlet-doublet group in the top section and doublet in the nosepiece.