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Seben Zoom 8-24Mm, Cheap Zoom Eyepiece

Strangely Brown

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Spec-Chum

Spec-Chum

Posted
Posted

I had a (very) quick go with the EP last night. Got a good view of Saturn and I loved the zoom! Makes it so much easier, but then the rain came without warning!

The scope didn't even have chance to cool down so very unfair to base a review on that "half light".

I was impressed with what I did see tho...

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DrRobin

DrRobin

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Hi Spec...

Glad the Seben is working out for you. Now all you need is a bit less cloud to give it a really good test. One thing I noticed it that the focus is not quite perfect over the entire zoom range (understandable really, it is very hard to achieve with this type of eyepiece), so I zoomed all the way in, focussed and then at minimum zoom it wasn't very far out.

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Spec-Chum

Spec-Chum

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Certainly is! :(

One thing I did notice tho, the thread on the bottom to attach filters is almost all covered by the bottom lens holder and you can't screw a filter in fully. It seems to hold it OK, and I've only tried it with my cheap moon filter and not my more expensive UHC filter yet.

Has anyone else noticed this?

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DrRobin

DrRobin

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Hi Spec.......

Glad it is working out for you and lucky you finally got a bit of clear sky. No such luck up here. The Sebens are good value for money, give great views and fairly easy to get on with.

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DrRobin

DrRobin

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Hi Ant,

The Sebens work pretty well on a variety of scopes. I sold mine but tried it on an ST80 and a 127 Mak. I think it was easier to use than either of the stock eyepieces which came with those scopes. i never tried it on my 250mm dob (also sold), but there are others on here who have 200m dobs so they should be able to give you a comparison.

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Spec-Chum

Spec-Chum

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Mine works very well on my 200p.

I've been meaning to post a first light report on it, but not had chance yet. What I can say now is don't expect the world and you won't be disappointed, this EP really is a bit of a bargain...

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Spec-Chum

Spec-Chum

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As promised, here is a first light report from using my new Seben 8-24mm zoom, sorry it's a bit late...

I had a play with the zoom function whilst the scope was cooling down, so this part is not a report on the image quality just how the Seben is to use in general.

I was just generally browsing the sky and zooming in and out of nowhere in particular. I found the Seben a pleasure to use. It fitted perfectly into the EP tube, with no slack. The twist zoom move had sufficient friction to make sure you knew you were turning it, but was lose enough so a minimal force was needed to zoom. I also like the fact that it was what I’ll call “free zoom” as opposed to a “click zoom” in that the zoom is infinite between the range, and you don’t have to “jump” between 24 and 20 or whatever.

Eye relief was quite generous also, and I didn’t have any issues whatsoever with having to be too close or blackouts anywhere on the zoom spectrum.

I did notice, however, that the filter thread on the bottom is partially covered so whilst I could fit a filter on it, it wouldn’t screw all the way in. It did seem to hold OK though, so probably not an issue.

After about an hour of zooming in and out at random stars like a mad man ( I really do love just scanning! I’m sure I’ve spotted many Messiers, but no idea which :D ) I did a star test with my 8mm BST just to ensure the scope was cooled and set out to find a suitable target to test the image quality. I’m quite new to this, but I thought Alberio would be a good test of colour and contrast.

With the Seben on its lowest magnification I took aim at Alberio and was very pleased with the view 2 nice sharp stars with very bright colours nicely contrasted against the background albeit centred in a “tube” caused by the limited FOV at this magnification. The only downer was the image was nowhere near as impressive near the outer edge of the image, about on par with my stock 25mm, plenty of streaky stars, but for this price, I can live with that…

I proceeded to slowly zoom in, gently adjusting the focus as I go, and got to about half way, so about 16mm. Still sharp, still contrasty still impressive, especially now the FOV has substantially increased also! Again, still soft at the edges, but let’s be fair here, you don’t buy any zoom for all round image quality…

I wind the focus all the way to 8mm fiddle the zoom slightly and wow, what a view! Alberio at it’s finest! Really contrasty, bright colours with pin point sharpness and a excellent 60 degree FOV. Again, soft at the edges, but I was very impressed with the Seben on this magnification!

I decided to pit the Seben against my 8mm BST now (it’s easily a match for the stock 25mm and beats the 10mm by miles…).

I keep Alberio in the centre of view and put in my BST and after a quick fiddle of the focuser I’m all set and, well, the stars are there, and they’re clear but they’re not as sharp or colourful as with the Seben? Are my eyes deceiving me? I swap them back…Nope, definitely shaper and more colourful with the Seben. I was kinda shocked to be honest. This is beating my BST?

To be fair, the BST was much more contrasty, as in the sky was darker and the stars were brighter, but you could certainly see more actual colour in the Seben, the BST appeared a little “greyer” or “washed out”, the BST was also softer, not by much, but you could tell the Seben was Sharper.

Another thing I noticed was that the BST seemed to be more zoomed in then the Seben, even though they were supposed to both be 8mm, the Seben seemed more like 9 or 10mm.

This is not a conclusive visual test by any means, and I also had a rattle on my BST which needed to be tightened, so that may have had something to do with it, but all in all I’m very impressed with the Seben, especially at the higher magnifications and you’ve gotta don your hat; the Seben even MATCHING the BST is impressive enough, let alone BEATING it.

I really need to test on Saturn when I get chance, as I suspect the Seben will lose out on detail there, but, for Alberio at least, it holds its own and then some…

Pros:

  • A generous 60 degrees FOV at (so called) 8mm
  • Nice feel to the zoom
  • Very sharp image at the centre of the FOV
  • Excellent contrast
  • Better than my 8mm BST on Alberio????
  • PRICE!

Cons:

  • It’s not parafocal, and refocusing after doing a big zoom was a bit of a pain, especially if, after you zoomed in on the Ring Nebula like I did, there was just a big blur in the middle with no stars in view to ensure I was in focus!
  • The FOV is only 40 degrees at the lowest magnification :( just the time when you’d want more! This is somewhat compensated though, by a rather generous 60 degrees at 8mm :)
  • 8mm doesn’t seem to be 8mm (more like 9 or 10mm)
  • Quite soft around the edges
  • The filter screw thread is semi-obstructed, but seems to hold OK
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Spec-Chum

Spec-Chum

Posted
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Oh, and while I remember, I did try to Barlow it too. Just for a bit of fun.

Too much eye relief on the lower and mid mags caused severe (and I mean SEVERE on the low mags!) blackouts, but it was reasonably effective on the higher mag end (from about 12 down) but there really is no point of Barlowing a zoom and using it at low / med mags anyway...

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Strangely Brown

Strangely Brown

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Hey Spec-Chum,

Your review was great- with pleasingly similar findings to mine.

I am sure that (like me) you found that it certainly does come as a surprise to note that it beats the BST: especially so on the Ring Nebula and on Saturn...

I must say though, I have had no problems adding a filter to mine; it offers a very snug fit on my Baader Neodymium Moon and Skyglow filter- but I actually prefer the view without it (it seems to me to be a little like wearing sunglasses...)

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Spec-Chum

Spec-Chum

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Yeah, it was a pleasant surprise but I feel it's only fair to mention the BST is sharp across the entire FOV and not just in the centre, like the Seben.

I really do like the Seben, and it's now my workhorse EP, but after further testing I must update my review to state the BST does beat it when I want to see more detail, especially on larger DSO's such as M13.

The Seben is only better on small objects that pretty much fit in the centre of the EP (Albireo for example)

Still a bargain tho...

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  • 5 months later...
Eastridge

Eastridge

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Posted

I also bought one on the basis of comments here and happy for what I paid for it.

Edge softness isn't an issue for me ( although I appreciate it is for many) but do intenbd one day to get a fixed EP in the middle range for quality, this is very useful for seeing what mags work best and general 'scanning' around.

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John

John

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I picked up one of these as well for a public viewing session that I'll be doing shortly. The one I got from e.bay looked identical to the Skywatcher one and came with a plastic beaker container thingy. In my F/7.5 refractor it works pretty well between 8mm and 18mm but gets rather narrow and astigmatic in the focal lengths beyond that. It's better than it really ought to be for what I paid for it :smiley:

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