Starguider 8-24mm budget zoom eyepiece

[Cosmic Geoff]

This is a 8-28mm zoom eyepiece, 1.25" fit, branded as "Starguider" and sold by "Sky's the Limit".  The claimed spec includes fully coated lenses, FOV 40-60 degrees (24-8), eye relief 18-15mm (24-8), internal blackening, and a T42 thread under the eyecup rubber.

The suppliers claim that it is the same as the Sky-watcher and Celestron ones which it physically resembles. It also resembles the Seben 8-24mm zoom.  The price was £42 + postage, which would be cheap even for a decent fixed eyepiece.

The eyepiece comes in a truncated cone shaped protective case and looks well finished. However It had an internal rattle sounding as though a lens was not clamped down tight. The zoom sleeve was very stiff to turn but freed up a bit in daytime use. 

A daytime test in the 102mm Startravel revealed that the eyepiece worked and that the 40 deg field did not feel obnoxiously small. 

I was able to try the eyepiece on the night sky the same evening in the C8 SE Nexstar. Conditions: urban sky with moonlight, poor seeing.  I used the eyepiece in a double star hunt with the following conclusions: Optically it seemed to work as well as my 8mm Celestron X-Cel (old model), and 10mm Baader Classic Ortho.  Mechanically, I found that the stiff zoom action was a nuisance as it was hard to know if I was twisting hard in the right direction, and I had at times to shine a red light on the zoom scale, or grip the body to stop it rotating.  The 6/8SE mount has some backlash, and does not take kindly to heavy-handedness at the eyepiece end, resulting in the desired object disappearing from the FOV.

The eyepiece required re-focusing after a change in zoom level, which I found to be a nuisance especially when going to higher power. In the C8 SE the actual field of the zoom at 24mm is not wide enough to guarantee finding objects by GoTo in random parts of the sky, (even when I remembered to set the zoom to 24mm) so I had to use the 25mm kit Plossl for locating and then swap in the zoom eyepiece.

At one point I found I was twisting hard in an effort to zoom the Celestron X-Cel, which has (in the dark) a similar look and feel and weight. This did not go well.

I split several faint double stars at around 3" separation. This isn't a severe test, of course. I also looked at the Epsilon Lyrae double-double near the zenith, which was easily split (as it ought to be) at 8mm (250x) with the stars well separated and showing signs of an Airy disc and diffraction rings.

In summary, the stiff zoom action was a nuisance, and the need to refocus after zooming was disappointing. Both reduce the attractiveness of this device vs separate (possibly parfocal)eyepieces.

I would be interested to hear if owners of similar pattern 8-24 zoom eyepieces had the same issues.

http://www.ebay.co.uk/itm/Starguider-8-24mm-1-25-Zoom-Telescope-Eyepiece-/162523741115?hash=item25d72b7bbb:g:AOUAAOSw5cRZIVNn

[davyludo]

Thanks for the review Geoff. I'm quite interested in trying a zoom eyepiece - especially as part of a grab and go setup (maybe with a single low power piece with a wider FOV to find things). Sounds like optical performance is acceptable...but mechanical quality might be a bit questionable. 

Might give it a bash for that price and let you know if I have a problem with stiff zoom.

[Nyctimene]

Thanks for sharing your experiences, Geoff!

My two zoom eyepieces, a Baader Hyperion Mk III 24-8 mm, and the Seben Zoom 24-8 mm, are rattling, when shaked, the Baader to a lesser degree. IIRC, Baader claims this as proof for not pinched optics. I've never noticed any negative effects of this on image quality. Both zooms need refocussing, when the focal length is changed, e.g. from 24 to 20 mm with the Baader, in all of my scopes, even those with short focal lenghts as 400 mm. 

In temperatures below 0° C, the Baader zoom mechanism gets rather stiff; no experience on this with the (new) Seben up to now.

The Baader Zoom is my most used eyepiece.

Stephan

[John]

Interesting review Geoff

I've owned a couple of clones of the zoom you are reporting on, one branded Skywatcher or Seben (the brand name was not actually on the eyepiece) and one branded Celestron. Both had rattles and the zoom action varied from rather loose in one to a bit stiff in the other. I've also owned a couple of the Baader 8-24's (a mk II and a mk III) and the Leica ASPH zoom currently, although that one is off being cleaned at the moment.

Optically I found the Skywatcher / Celestron zooms work well for their price. I found the field stop at the 24mm position rather badly defined and the field of view rather narrow at that focal length but that is normal for most zooms of this range I've found, including the more expensive Baader.

My personal view is that fixed focal length eyepieces such as the Celestron X-Cell LX and the Baader Classic Ortho (particularly the last one) provide better overall optical performance but the zooms do well enough to be useful for a quick session and are very useful for outtreach events because they are easy to view though and the view can be changed in the twist of the zoom ring.

 

 

[Cosmic Geoff]

Thanks for the responses. In summary, a rattle and a need to do some re-focusing after zoom are normal.

It's suggested that all these 8-24 look-alikes are made by GSO and the conical case carries a marking: GTZ8-24, MZT8-24 (on mine), etc

I had a mount with the supermarket 70-700 telescope I used to own which was greased with the notorious Chinese glue-grease. As is an otherwise nice helical focuser I bought from China.  And now this zoom too, it appears.

On a subsequent night I found it easier to set the zoom level with the eyepiece in my hands and the zoom scale under a red light, before inserting it in the diagonal.

Any more reports?

[Nyctimene]

5 hours ago, Cosmic Geoff said:

It's suggested that all these 8-24 look-alikes are made by GSO and the conical case carries a marking: GTZ8-24, MZT8-24 (on mine),

The Seben 8-24 came in this strange looking case (reminding me of some "plaste" objects produced in the former German Democratic Republic until 1989 -even the colour!  - and the design called "formschön"); and carries the marking MTZ 8-24. Some kind of time capsule, this look!

Stephan

[DavidJM]

On 8/12/2017 at 09:52, Cosmic Geoff said:

Thanks for the responses. In summary, a rattle and a need to do some re-focusing after zoom are normal.

It's suggested that all these 8-24 look-alikes are made by GSO and the conical case carries a marking: GTZ8-24, MZT8-24 (on mine), etc

I had a mount with the supermarket 70-700 telescope I used to own which was greased with the notorious Chinese glue-grease. As is an otherwise nice helical focuser I bought from China.  And now this zoom too, it appears.

Any more reports?

Bought this zoom eyepiece (8-24mm Skywatcher from Skys the Limit) to go with my Heritage 100P for short back garden stints with no hassle of changing eyepieces. Initial thoughts after a couple of sessions is that for that grab and go quick moment this is a decent combination, the zoom on mine is fine, not stiff at all would actually say quite smooth, don't think the refocusing is an issue compared to changing eyepieces, views at 8mm and above satisfactory but I don't own a swathe of eyepieces at the moment so only the MA's supplied with the scope to compare and the zoom is an improvement on these. Still plan to invest though in separate eyepieces for my 8"

Packaging and labeling on mine matches comments already made so agree that it's likely a GSO generic used my numerous manufacturers (Skywatcher is on the side of the eyepiece)

Summary - not bad at the price for those quick grab and go sessions and happy to have in my eyepiece portfolio

[Cosmic Geoff]

20 hours ago, DavidJM said:

Bought this zoom eyepiece (8-24mm Skywatcher from Skys the Limit)

Did you mean Skywatcher or Starguider? The zoom I bought from Sky's the Limit is branded Starguider.

 

[DavidJM]

7 hours ago, Cosmic Geoff said:

Did you mean Skywatcher or Starguider? The zoom I bought from Sky's the Limit is branded Starguider.

 

Well spotted eagle eyed Geoff!

It's starguider not skywatcher, scopes and eyepieces mixed up

[Mr niall]

ive got the skywatcher hyperflex 7-21 zoom and that does indeed both rattle and need refocussing too! I dont mind though - keeps me from fiddling!

[Dave In Vermont]

The most common perceived 'problem' people report with their new Zoom: "It seems to 'rattle' when I shake it!" Solution: "Don't 'shake' it." 

Every parfocal eyepiece-set I've ever known has  needed a bit of tweaking to re-focus. The same goes for Zoom EP's. Perhaps this should come enclosed with eyepiece-sets & Zooms. On a card. "Minor Refocus May Be Required." "Please Don't Shake Me! - It Gets Me Rattled!"

Have fun all -

Dave

[RobertI]

I have the Seben 8-24mm and I really enjoy using it, especially for finding the ideal mag for a faint object by zooming in and out to see the effect sky brightness v object size. It performs very well indeed for the price.

Yes it rattles and is also rather prone to dust on the inside lenses. The focus does change as you zoom, but only really from approx 15-24mm, from 8-15mm you can get away without re-focussing in my experience. 

Sadly it is next to useless in my Heritage 130P which has a helical focusser!