Seben 24mm to 8mm zoom eyepiece

[Relpet]

I am fortunate to be able to spend about half the year, mostly summer months, in south-west France.  In the spring of this year I bought an 8" Dobsonian to take up astronomy as a new interest under deep velvet skies.  (Where have they been lately?).

I have been astonished by the interest shown by nearly everyone I know here, including good friends - the owners of a nearby gite.  As a result of this interest I have entertained up to ten people at a time, including guests from the gite, who want to see the craters of the moon, the rings of Saturn, the moons of Jupiter and so on.

I have paid them due courtesy in showing them these heavenly bodies through a range of EPs from a wide angle 2" 30mm  to a 5mm 1.25".  Queues form and I find I'm laying down EP's on a padded tray in such disarray that I have to leave them overnight before sorting them into their respective end-caps and boxes.  I love showing off the wonders of the universe but there must be an easier way.  Maybe a zoom lens is the answer for informal star parties like mine.  The budget is tight and I'm really doing this to make life easier for other people ( and me!) during these informal sessions.  Almost as an afterthought I took a look at the Seben.  Reviews were reasonably positive for something which, including delivery from Seben in Berlin by DHL to an address in France, came to less than £50.  It took three working days to reach me.

It came in a hard plastic case, a conical frustum with a screw-cap at one end.  The EP itself had two further end-caps.  The case would withstand very rough handling.

The EP itself is surprisingly light, weighing in at just under 200 grams.  Maximum diameter is just under 5 cms; 10 cms in length.

An easily removable rubber  eye cap, when removed, reveals a threaded element to fit a T-mount.  This threaded element itself threads into the main barrel of the EP.  I found if I screwed the EP too tightly into the T-mount the main barrel would unscrew leaving the threaded element in the T-mount.  The second time I did this I had to use a patent jar opener to separate the element from the T-mount.  Not recommended practice.

Since seeing four planets in five minutes last Saturday morning I have seen nothing but cloud in the sky since.  This evening the moon appeared briefly so it was out to the barn with warm clothes thrown over the pyjamas, trolley the Dob out of the barn and line up with the Seben.  Frankly I was astonished at the quality.  The zoom operates smoothly, without click stops.  A small amount of adjustment to focus has to be made as you progress from wide-angle to close-up but nothing that does not come naturally.  The full disc of the moon shows  at 24mm with sharp focus and focus stays sharp, after adjustment, at full zoom.  I can hear the cries already of "Wow!" from next summer's visitors.

I have to leave for England shortly and, the way the forecast is going, planetary observation with the Seben seems unlikely before I leave,  As it is I got about ten minutes with the moon this evening before the clouds rolled in.  So this report is necessarily abbreviated in terms of actual use.

I did manage to fit a borrowed Nikon D5100 to the EP but before I could get the ISO and shutter settings right the moon disappeared.  So, sample photos taken were not indicative of the quality as seen through the EP itself and would be a misleading advertisement.  If I get a chance before I leave I will post pictures of an acceptable standard.  Those I did take showed promise.

Purists, high-rollers, technophiles, anyone who wants the best may turn up their noses at this EP but I can see it doing exactly what I want it for - to give a lot of people a lot of fun under starry skies next summer.  Four EPs for the price of one?  Suits me, especially as my more precious EPs can be restricted to personal observing.  I hope this is helpful to anyone considering a purchase.

[triton1]

People on here do say good things about the 8 to 24 same as the Celestron I think it's the 7 to 21 that's to be avoided.

[keithatrochdale]

They work well on PST and PST mods, so convenient!

.

[Dave In Vermont]

I have the Vixen counterpart to the Seben 8 - 24mm Zoom. It's more money due to it's Lanthanum lens-element, but they look like twins. And this is my grab & go eyepiece for doing outreach work in local parks. It is a very convenient solution to having my gear include a bunch of loose EP's. I think you'll continue to find yours to be a good solution too.

They're also fun for people to look through and use. Coax your audience to play "Lunar-Skydiver." That's always a hit at informal parties!

Thanks for the end-user report on your Seben. I'll add that one to my list of brands worth suggesting to those looking for a good, inexpensive-ish Zoom EP.

Have fun,

Dave

[Relpet]

Having finished my report at 01.30 I was rather surprised to suddenly awake at 04.23.  Thought "What the heck.  Let's see what the sky has to say."  Blow me down, it's crystal clear.  There's the Great Hunter filling my doorway.  So it's out to the barn again.

Orion Nebula was first on the list.  My eyes are pretty dodgy anyway but the stars from edge to edge were sharp at 24mm, though I had to look straight down the barrel.  Not much eye relief - if that's the right expression.  Zooming in I had to continually re-focus but the trapezium was pretty sharp at 8mm, though the whole nebula looking good at 24mm.  I tried it with a 2" ES 2xBarlow but could not focus beyond 12mm.

Betelgeuse as good as I've ever seen it, at 8mm.  Then what's this coming up.  Looks like Mars peeking between the trees.  Very low on the horizon so difficult to get sharp focus but as good as I've seen it.  Venus has to rise a bit higher to get over the next trees so I wait.  Pin sharp (for Venus) at 24mm but difficult to get much benefit beyond 12mm.  Decided not to wait for Jupiter.  I'm supposed to be cutting up logs with a 40cm chainsaw in a few hours.  So, it's a cup of cocoa and back to bed.  In conclusion, if Revelation had included this one EP instead of the three that came with the 'scope I would have had no complaints.  This is going to be a real treat for casual observers next summer.  Thanks for your helpful comments, chaps.

[Relpet]

Oh, and as well as a sprinkling of meteors one absolute fireball.  Worth getting up.

[seo]

I have a few of them in my "grab 'n go" collection. A 6mm one and the rest are between 10mm and 21mm if I remember well. For the money they cost  they're just fine.   

[John]

I've recently acquired the Celestron branded version of the 8-24 zoom. It sounds exactly the same as the one that you have right down to the plastic container. Quite inexpensive really, for what it is.

It rattles a little but it seems a decent eyepiece. I'm going to use it for outreach / sharing viewing. It's easy to see the field of view and the eyecup is soft so it won't put off folks who have not looked through a scope and / or those that wear glasses to observe.

Worth having in the tool box   

[laudropb]

Very nice report. I have this eyepiece myself and it is a very useful addition to the collection. The only negative I have found is the change in focus when zooming. At times I find getting fine focus can be difficult at the shorter focal lengths.

[Chris]

I've also been very pleased with my 8-24mm Seben zoom, nice report

[Relpet]

Very nice report. I have this eyepiece myself and it is a very useful addition to the collection. The only negative I have found is the change in focus when zooming. At times I find getting fine focus can be difficult at the shorter focal lengths.

Yes, I do agree.  After finding myself under a rather brighter moon tonight with less cloud I was able to play for a lot longer, including with a Barlow.  As I am very short-sighted and have glaucoma focussing is always a bit hit and miss with me anyway.  But it was fun finding out what it could do.

[Relpet]

For those interested in the astro-photography aspect of this eyepiece I managed to take some shots tonight.  I have to say that in most cases the image in the flip-out monitor was sharper than most of the pictures that resulted.  Holding a Dob steady with one hand and pressing the button with the other at 1/45th of a second doesn't make for the sharpest snaps.  I post these only to give people some idea of what can be done.  And it beats trying to use a webcam with a laptop hands down.

[Relpet]

I have the Vixen counterpart to the Seben 8 - 24mm Zoom. It's more money due to it's Lanthanum lens-element, but they look like twins. And this is my grab & go eyepiece for doing outreach work in local parks. It is a very convenient solution to having my gear include a bunch of loose EP's. I think you'll continue to find yours to be a good solution too.

They're also fun for people to look through and use. Coax your audience to play "Lunar-Skydiver." That's always a hit at informal parties!

Thanks for the end-user report on your Seben. I'll add that one to my list of brands worth suggesting to those looking for a good, inexpensive-ish Zoom EP.

Have fun,

Dave

Hi, Dave,

Just up the road I have friends who own a gite.  A couple turned up with four children on Saturday so we offered them the chance to see the moon tonight.  I set up the Dob at their place with the Seben: four grown-ups, four children immediately captivated.  If ever I needed justification for buying this EP tonight was it.  Skies look dodgy for tomorrrow but everyone's ready for a 6 a.m. start to see four planets in the east before dawn.  I wish I'd known of this EP six months ago.  So much easier for sharing the pleasure.

Peter (aka Fang)