High power zooms?

[acey]

I'm looking for a high-power zoom eyepiece. Apart from TeleVue, what (if any)choice is there?

With my 12" f4.9 Flextube I currently use a Baader Hyperion 8-24mm, TMB Planetary 6mm and Nirvana 4mm. This is for DSO viewing, where I find a zoom to be a great advantage for finding faint fuzzies, and I need high power for the smallest objects.

What I'd ideally like is a 4-8mm zoom to cover the high end. It looks like the only thing that comes close to what I'm looking for is the TeleVue 3-6mm. The Pentax 6.5-19mm wouldn't take me high enough. Are there any other contenders offering focal length in the 4mm to 8mm range?

[John]

There is the Speers-Waler 5-8mm zoom. I've seen great reports of their optical performance. There maybe some issues with them needing more than the normal amount of inwards focuser travel though so it's worth doing some research.

[acey]

Thanks John, that sounds very interesting and I'll look into it.

I've also learned that there's a bespoke barlow for the Hyperion zoom. I'd discounted barlowing as an option but it looks worth considering as a third option.

[Moonshane]

I appreciate and acknowledge your point about 'not Televue' but consider convenience too. for me the only contender in this area is the Nagler 6-3mm zoom. it's superb. consider size too. the speers waler plus a barlow would be like a baseball bat in the focuser

the nagler zoom is a 'little' smaller

used at about £200 they are the best zoom eyepiece I have ever used.

[AndyH]

My Speers Waler 5-8mm zoom will need to be ripped from my cold dead hands. 82° of sharp, contrasty goodliness.

An adapter/extension can be bought for little cost, that fits 'tween the body and bottom doublet, turning it into a 3.12-5mm zoom. Handy if you have a very low focal length scope.

Not terribly easy to get hold of now.

[acey]

The Speers-Waler 5-8 appears to be discontinued - wonder if they'll bring out a new version? Looks huge but the Hyperion 8-24 is pretty chunky too, and 5-8 would fill in the magnification range perfectly, if I could get hold of one. But the TV looks to be a very convenient size which is a big plus.

[keithatrochdale]

Only negative with the TV is 50 deg. FOV, but it is small, light and works well. My Speers-Waler 5-8 is big and heavy but has an 80 deg. FOV.

[E621Keith]

Most zoom eyepieces on the market today were derived from spotting scope eyepieces. A high magnification zoom doesn't have a market for spotting scopes use, so your choices are limited to the few astro specific designs, such as the Speers Waler or TV.

Is there any reason why you discounted the barlow route? A high quality barlow will have negligible effect on the image quality and on some occasion can even enhance it.

[acey]

Is there any reason why you discounted the barlow route?

Convenience, mainly - the Hyperion is big enough already without putting it in a barlow, and while the bespoke barlow appears to be reasonably small it would still involve threading into the Hyperion nosepiece, by which time my target would quite possibly have drifted out of the FOV. Quick eyepiece change matters to me. Also I prefer to have as little glass as possible. But I ought to give it a go anyway with my Meade barlow before forking out for a TV 3-6 (the only option now that the SW 5-8 is no longer available).

[alan potts]

There is the Speers-Waler 5-8mm zoom. I've seen great reports of their optical performance. There maybe some issues with them needing more than the normal amount of inwards focuser travel though so it's worth doing some research.

John is on the money as normal. This is a really good eyepiece but just a little colourful at the very edge. This can be forgiven when you think it is a 82 degree FOV. I sold mine on to a Gent in England on site only because it didn't get used as much as it should with all the other eyepieces I have.

I could never use it at 5mm on my GSO due to inward travel.

Alan.

[acey]

After much searching I found a dealer still offering the discontinued Speers-Waler 5-8mm zoom: Tecnosky in Italy. Their website has English translation and the service was excellent. I used the zoom last night for the first time and I'm impressed. In my 12" f4.9 flextube I had no trouble reaching focus at all magnifications. It's big and heavy, but I knew what to expect and don't see it as an issue. I'll be using this eyepiece a lot. The Tecnosky site now shows it as out of stock, so looks like I got the last one.

[Moonshane]

wow - shows what some ingenuity and persistence can turn up! hope you enjoy it

[Naemeth]

Good to see you've found an incredibly rare eyepiece . Hope you enjoy it!

[Peter Drew]

Yet another clear night (4 in a row!) gave us a chance to try a "shoot-out" between a Speers-Waler 5mm- 8mm zoom and a 3mm- 6mm Televue Nagler zoom on a 220mm aperture achromat of 2700mm FL. The object was the Moon. This gave a magnification range of 335X- 900X. Both zooms performed well, the highest magnifications provided no improvement in detail as would be expected but the images were still decent enough. The SW gave well defined detail right across the 82 degree field which was beneficial at these magnifications but eye placement was critical to avoid "kidney bean" issues. The TV zoom with it's 50 degree field was equal in performance but did not suffer from KB.

Overall, I think that anyone would be happy with either zoom for high power viewing on an appropriate telescope.

[E621Keith]

great report Peter. at f12 I'd expect them to be similar. maybe you could do another installment at f5? I think the SW would still yield great results that said. my main issue with it is the sheer size difference. the image below is with a barlow.

...

I didn't realise a garden hose pipe connector can be use as focuser knob. Nice idea

[Moonshane]

great report Peter. at f12 I'd expect them to be similar. maybe you could do another installment at f5? I think the SW would still yield great results that said. my main issue with it is the sheer size difference. the image below is with a barlow.

compared with