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bingevader

Budget zoom for school.

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Hello all,

I've been thinking for a while that it would be a lot easier if we had a zoom eyepiece for school rather than me running around changing over eyepieces.

Obviously, this would be a budget eyepiece.

Firstly, because the school budget won't stretch to much.

Secondly, it's going to have little fingers all over it.

So, we're looking at the range of 7.2-21.5mm eyepiece clones that seem to be in abundance at the moment.

(OVL, TS, Omegon, Opticstar, Orbinar, Seben in no particular order).

I'm hoping that with all the experience on here, we can choose a suitable EP and rule out any duds.

If anyone has any experience of any of these for night time observations (mainly), I'd be very grateful.

Cheers

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I have a number of zoom eyepieces ranging from cheap to very expensive.  The best cheapest version I have is the Seben 8mm-24mm.  Avoid the cheaper Seben 7mm-21mm unit, very poor by comparison.    🙂

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I have the TS 7.2 - 21.5 and it is an excellent zoom eyepiece and performs well in any scope I’ve used it in. 

Avoid the 7 - 21 zoom eyepieces as they are a cheaper and inferior design.

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I'd stick with the Celestron/Meade 8-24mm zoom and their generic equivalents.  They are a known good quantity very similar to the Vixen LV zoom from which they were cloned.

The 7.2mm to 21.5mm zooms are of good quality optically, but they have very limited eye relief and are very stiff to zoom in my experience with them.  They also have narrow apparent fields of view.

Watch out for the cheapest zooms.  They're a mix of glass and plastic lenses.

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I use one of the 7.2mm - 21.5mm zooms. Very decent performer for it's cost. The field of view at the longer focal length end is a bit narrower than the spec says but it's wider than specced at the shorter end. Its sharp though and I often use it with a Baader Q-Turret 2.25x barlow as a high power zoom.

I used this combo recently at an outreach event showing the folks Neptune at 280x on a manual alt-az mount in my ED120 refractor - many folks enjoyed the view of the outermost planet on that evening :smiley:

Mine is not stiff to zoom - very smooth in fact. The twist up eyecup is nice as well.

 

zoombarlow.JPG

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6 hours ago, John said:

Its sharp though and I often use it with a Baader Q-Turret 2.25x barlow as a high power zoom.

I think we'll probably need a barlow at some point, especially with one 'scope. :)

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For outreach sessions I carry the above plus a 30mm Aero ED 2 inch eyepiece for a set that gives decent performance across a wide range of applications. Not so expensive that I worry about them getting finger marks etc on the lenses either.

 

 

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18 hours ago, bingevader said:

I'm assuming the barlow helps a bit with the eye relief?

Yes, the barlow pushes the eye relief out a little. The eye relief of that zoom is quite comfy without the barlow though and it has a twist up / down eye cup.

 

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I have the 8-24mm BST Starguider zoom.  This seems to be a clone of other similar models (Seben,  Celesttron etc).  It was relatively cheap, and is of reasonably good quality. Only drawback is that the zoom action is so stiff that I have to take it off the telescope to adjust the zoom setting.

Like others, i have heard bad things about the 7-21mm models.

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On 20/01/2020 at 14:37, Cosmic Geoff said:

.... i have heard bad things about the 7-21mm models.

So have I.

The 7.2-21.5mm zooms are pretty good though.

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It must be word of mouth then, because I've searched around a bit and can't find many "bad things"! :D

Anyway, we ordered and have received an Opticstar 7.2-21.5mm zoom and 2x barlow.

The zoom looks decent enough and the action of the zoom itself is smooth and easy.

I'll let you know what the views are like when we get the chance! :)

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Only a brief, half hour, chance last night, but very promising.

It's a good sold bit of kit and as I said above, smooth in action.

I didn't have anything to hand that was a direct comparison, so used the 25mm and 8mm TV plossls!

The conditions weren't great with twinkling stars that wouldn't come to focus in any EP so this will need further playing with.

However, the views of M42 were lovely.

The nebula fitted it with room to spare at 21.5mm, but obviously not as much room as the lower power TV plossl.

At 7.2mm however, it had a wider field of view than the 8mm plossl.

The image was favourably comparable and objects remained in focus across the field of view.

I only compared the extremes, but I do have a 15mm plossl that I could use to look at the middle in future.

The zoom isn't parfocal between focal lengths, but I assume this is to be expected because of the design.

I couldn't fit the whole of the Double Cluster in at 21.5mm which is a shame, but not unexpected.

M36, M37 and M38 looked suitably impressive.

Very much a first glance before the clouds rolled in and on a poor night, but very pleased so far. :)

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Out with the school children last night.

What a convenient set up!

Little tweak of the zoom, little tweak of the the focus and away you go! 

Doesn't stop them leaning on the 'scopes or knocking the tripods though. :D

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9 hours ago, bingevader said:

Doesn't stop them leaning on the 'scopes or knocking the tripods though. :D

For the tripod legs, try putting blinking red LEDs at their feet.  For leaning, try using a kitchen step stool with a nice handle they can lean against instead of the telescope:

spacer.png

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When I'm doing outreach I find that the younger observers do have a habit of grabbing the eyepiece with one or both hands before putting their eye to it. I always try and explain up front why this is not a good idea but there are always a couple whos enthusiasm runs away with them a little !

 

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I do my preliminary, "chat", it makes little difference.

I think it's about being physically connected to the 'scope.

Apparently, experiential learning is all about being hands-on. ;)

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