7.2mm - 21.5mm Zoom

[N22]

Got my seben zoom eyepiece today 2014. Build seems good, wasn't that impressed at first with the zoom, it took a little getting used to.

Had a look at the moon tonight, and was quite happy with its performance, comparing it to my only other eyepiece, 15mm plossl celestron.

Sent from my LT30p using Tapatalk

[Johnny4365]

I'm not sure I'm following you.

The widest actual(true) field of view you can get in your scope with a 1.25" EP is with a 32mm 52 degree plössl, it is about 52*32/1000=1.66 degree, while if you get,

e.g. a 28mm 58 degree Max Vision, you'll get 28*68/1000=1.9 degree, framing the Plejade beautifully.

MV 28mm has much better edge correction than a Panaview, at essentially the same cost, and the exitpupil under 6mm will also enhance the darkness of background than a 32mm.

Interesting post YKSE. I've loads to learn about astronomy so I may be confused myself. But I got the impression that generally when viewing with a wide FOV in a fast scope only the centre of FOV will be clear and the rest will be distorted  (Astigmatism ?).

I'm beginning to feel the need for a book, is "Choosing and Using Astronomical Eyepieces" good ?

[John]

Interesting post YKSE. I've loads to learn about astronomy so I may be confused myself. But I got the impression that generally when viewing with a wide FOV in a fast scope only the centre of FOV will be clear and the rest will be distorted  (Astigmatism ?).

I'm beginning to feel the need for a book, is "Choosing and Using Astronomical Eyepieces" good ?

That can be true for low cost wide field eyepieces but the better quality ones overcome this and can be sharp right to the edge of even fast scopes. You pay a price for this of course 

The book you mention looks good to me although I've not read it. The author posts on this forum reasonably regularly 

[YKSE]

@Johnny4356

I've just got the book, a very comprehansive I must say, a quick scan shows a lot of interest details.

Just as John says, low cost EP will show more astigmatism, e.g. I will not be surprised if your zoom shows quite some astimatism for focal lengths around 20mm, while the 28mm Maxvision (unbranded Meade SWA, if you have not read about it) will be much sharper near the edge, and shows more and much darker sky than your 40mm plössl.

[moriniboy]

Here is a TS next to a Seben, difficult to tell apart from the lettering but there is a 135 euro price tag for the TS and a 80 euro for the Seben.

Feels exactly the same, will get back on the views shortly.

Seben on left.

[moriniboy]

Note: it is my intention to use these ep's purely for solar work, I have not tried stargazing with them yet....

Quick comparison using a 102mm ED F7.5 refractor and a 2" solar Lunt wedge

Apart from a minor adjustment of the focuser between ep's I could not tell the difference. In fact the Seben was easier to use as the internal grease used was less viscous than the TS one.

Next I tried daytime viewing on a group of trees 1 mile away.

The same small re-focus was evident as before between ep's and they both showed a softening towards the field stop, once again identical views were obtained.

To my eyes these are just re-branded versions of the same ep, with the Seben coming out on top price wise. Quality of finish was identical however the Seben does not come with a box (only useful if re-selling I find)

I would like to test these at night to see just how well they perform astronomy wise, it may be that the focus softening is not too intrusive, we will just have to see.

[Merlin]

I have the OPTIC STAR-branded, 21-7.2, planetary zoom. They have two versions, mine's the cheaper version. It works well with the PST.

[Astral Enigma]

I have the other Opticstar branded zoom - the more expensive (£199) version. As far as I can work out, it's quite possibly the same as the Skywatcher Hyperflex 8E (but don't rely on that!) - at least the markings are identical and in the same font and externally it is physically identical as far as I could see.

Whether it's any better than their one at half the price, I don't know. Other than use the two side by side how can you tell? Having bought one I'm not planning to buy the other to find out... 

Is it any good? Well, initially I was far from convinced, but as a relative newbie it's highly likely my expectations were too great. Over time I've found it easy to use and reasonably good, but not sharp, images of plants down to around 10mm. After that it gets blurry - but of course seeing conditions are a huge variable. I've set it at 10mm and swapped to my Baader Hyperion 10mm prime, and noticed very little difference - if anything slightly preferring the Opticstar, whilst a friend doing the same test at the same time with me thought the Hyperion was sharper.

There don't appear to be a lot of Opticstar eyepiece users out there - anyone else got any thoughts?

[cyrille-86]

hello ,

Today I have bought this orbinar zoom EP (7.2-21.5) on eBay .  I would like to know if somebody did other "test" with this EP,on night sky ?

Johnny4365 May be ? What feeling about it ?

Thank You

Sorry for my bad English , I'm french !

[andre2]

Hi, my orbinar zoom got broken today. I think that dust comes inside the zoom and while zoom in someting get wrong( i think). should i buy one again for my PST solar telescope or should i save Some money for the better build pentax XF 6.5=19.5 zoom? Thanks!!