Zoom Eyepiece query

[bomberbaz]

Right what I do know about zooms is that just like fixed focal length eyepieces the range and and quality is very broad. You have the budget versions such as some from seben, skywatcher and some others, then you move along to the premium ones from pentax, leica and televue etc.

So i am still wieghing up my options for eyepieces in my middle ground at 1.25 size for use in the Ed ota ( also maybe the dob) and a zoom would seem like a sensible idea. So my thoughts as to what I would like and budget are as follows:

8 - 24mm or thereabouts; decent eye relief of no less than 16mm; open to options on the fov as I understand they are all quite similar; clickstop version would be nice but not essential; price £100 - £150 although happy to consider other ideas but just might be a little longer in saving if its felt worthwhile.

In no rush though, I keep trolling the 2nd hand markets and happy to wait. Waited over 2 months already and thats a record for me 

tia everyone.

ALLOW ME TO ELABORATE: My thinking is I have nice eyepieces at 5,6,6.7 & 8 that do the lower focal ranges. I also have a 22mm SWA from skywatcher that is reasonably lightweight, probably not much heavier than the lower focal length ep's and this will serve as the low power/finder eyepiece giving 1.7 tfov. So if I can get a reasonable zoom that wieghs similar to cover the  mid range I will have quite a nice compact outfit that still makes use of my high power eyepieces for the high mag planetary etc.

[Dave In Vermont]

Steve - I have both the Vixen LV 8 - 24mm Zoom, which has a Lanthanum lens-element, and the Baader Hyperion Mark III 8 - 24mm Zoom - which is both 1.25" and 2" with different adapters included. Both are very good indeed.

With any 8 - 24mm, the 24mm setting is rarely used due to it's very narrow FOV. But this is not a bug - it's the nature of the optical-design.

Happy hunting!

Dave

[Paul73]

The Baadar effort is pretty good. The FOV is limited at the 24mm end and a little soft at 8mm. But, for the money it is quite impressive.

i use mine in my travel setup. But, I wouldn't have it in place of the fixed length alternatives.

Paul

[John]

I've owned a few zooms including 3 of the Baaders for some reason !

The Celestron / Seben / Skywatcher 8-24's are decent buys for around £50 or a wee bit less as travel or outreach options.

The Vixen and Tele Vue 8-24 zooms are the same item as has been mentioned quite a few times on here. Those and the better quality (earlier) Meade 8-24 are a step up from the base Celestron / Seben / Skywatcher zooms although the price has climbed quite a bit too.

The Hyperions are better again IMHO and their FoV in "real life" is a little different from the quoted specs at 42 degrees (24mm) to 65-68 degrees (8mm). As well as the narrowish FoV I found the field stops of mine were indistinct and "mushy" at the 24mm setting. I tended to treat them as 20-8mm zooms. On the Moon and planets they perform well with just a little ghosting at 8mm and a touch more light scatter than fixed focal length mid range eypeieces. I found a noticable difference in light transmission between the zoom (lower transmission) and fixed focal length eyepieces when viewing deep sky objects which was slightly annoying once I knew it was there although for casual deep sky observing it's not a major issue.

With the exception of the amazing little Nagler zooms (not the focal ranges you are interested in) I've not tried the Leica or Pentax zooms. The Leica has a consistent 60 degree AFoV and seems very highly regarded with a price to match. There are 2 Pentax zooms as I understand it with one being fine for solar observing but not so good for nighttime and the other superior but higher priced.

And thats about all I know about zooms !

 

 

 

[Highburymark]

Best option for £150 Steve? Save up a few quid more and get the Hyperion zoom. If you find £150 in the street tomorrow, then go for the Pentax XL zoom which FLO is selling for £299. Both top quality.

[bomberbaz]

Hmm came accross this one from Pentax that I was previously unaware of https://www.widescreen-centre.co.uk/astronomy-eyepieces-and-barlows/pentax-super-wide-angle-eyepieces/pentax-xf-65mm-195mm-125-zoom has anybody come accross one themselves yet?

Also the SW version here from flo http://www.firstlightoptics.com/skywatcher-eyepieces/skywatcher-hyperflex-72mm-215mm-eyepiece.html Both the above sit within my thinking range but I think I read that John said you didn't think the 7-21 versions were up to much although the subject was seben at the time. Was that carte blanche to all 7-21's or just the seben John?

If you check the OP I have elaborated on my thinking if that helps. One thing I do notice is they are all going to be tight on ER for me as a glasses wearer but thats life. 

[michael.h.f.wilkinson]

For the eye relief mentioned you should perhaps see if you can get a William Optics Zoom-II 7.5-22.5mm. It is no longer made but clones include the SkyWatcher HyperFlex 7.5-22.5. I use this for solar, and it is the only zoom that really has given me enough eye relief to use with glasses. Its rated eye relief of 18.5-19mm is correct, and I can often extend the twist-up eye-cup slightly.

[bomberbaz]

Cheers Michael, found that version at a provider, the ER looks good. How do you find the performance, and have you used it on deep sky observations at all?

4 minutes ago, michael.h.f.wilkinson said:

For the eye relief mentioned you should perhaps see if you can get a William Optics Zoom-II 7.5-22.5mm. It is no longer made but clones include the SkyWatcher HyperFlex 7.5-22.5. I use this for solar, and it is the only zoom that really has given me enough eye relief to use with glasses. Its rated eye relief of 18.5-19mm is correct, and I can often extend the twist-up eye-cup slightly.

 

[michael.h.f.wilkinson]

Just now, bomberbaz said:

Cheers Michael, found that version at a provider, the ER looks good. How do you find the performance, and have you used it on deep sky observations at all?

 

Haven't used on on DSOs much if at all. I will check it out next time I get a chance to see the stars (around Michaelmas or so, by the look of things). I gather John has used it on the stars, and found that the orthos he had easily beat it at higher magnification. That does not surprise me.

[bomberbaz]

9 minutes ago, michael.h.f.wilkinson said:

Haven't used on on DSOs much if at all. I will check it out next time I get a chance to see the stars (around Michaelmas or so, by the look of things). I gather John has used it on the stars, and found that the orthos he had easily beat it at higher magnification. That does not surprise me.

Cheers Michael and like I say above, my intention is that this will be a mid power eyepiece from around x50 to 110 in the ED100, after that I have individual glass mentioned that comes into play. 

It seems like it would be a balance of performance and comfort from what you say but that's what us speccies have to put up with. I have put that top of the list based on the two criteria of decent performance and eye relieyf. Have to say its fov seems slightly higher than some of the others although stated fov and actual are not always the same. Thanks again.

[moriniboy]

Steve the Skywatcher one you mentioned above is the same as the Seben / TS ones I have, you can borrow it to try

[bomberbaz]

Just now, moriniboy said:

Steve the Skywatcher one you mentioned above is the same as the Seben one I have, you can borrow it to try

Got it nigel, cheers fella, much appreciated. It is the 7.2-22.5 and not the 7.2-21.5 though mate, they are different.

[bomberbaz]

Seben's version at just over 20 quid http://www.amazon.co.uk/Seben-Telescope-Eyepiece-7-5-22-5mm-Astronomy/dp/B00EL5XU9S

SW version at £180 http://www.bristolcameras.co.uk/p-skywatcher-hyperflex-8e-7-5-22-5mm-zoom-eyepiece-1-25-inch.htm

I realise the focal range is the same but I doubt the quality is. However would be useful to try how it feels to my eye, the zoom range and fov so still borrow please nigel

[moriniboy]

Steve,

Wrong Seben version here it is

http://shop.seben.com/sms/shop/index.php?p=b3JnYT1zZWJlbiZncm91cD0yJmxhbmc9MiZjdXJyPTE=&action=products&mode=view&id=190

Which is also the same as my other one

http://www.teleskop-express.de/shop/product_info.php/language/en/info/p4651_HR-Planetary-Zoom-Okular-7-2---21-5mm---1-25----7-Elemente.html

[Dave In Vermont]

I'd very cautious of 7 - 21mm or 22mm Zooms. It is these that often perform very poorly compared to the 8 - 24mm family of Zooms. There may be good ones, but I've heard enough 'disaster-stories' to warrant great caution. Look for reviews from end-users. Not advertisers.

Caveat Emptor,

Dave

[michael.h.f.wilkinson]

The 7.2-21.5 zooms mentioned are NOT the same as the 7.5-22.5. The former are the same as the Lunt 7.2-21.5, which I had, and has significantly less eye relief compared to the 7.5-22.5 I got as a replacement. The latter is larger, and has 4-5mm more real eye relief, I would estimate

[Dave In Vermont]

2 minutes ago, michael.h.f.wilkinson said:

The 7.2-21.5 zooms mentioned are NOT the same as the 7.5-22.5. The former are the same as the Lunt 7.2-21.5, which I had, and has significantly less eye relief compared to the 7.5-22.5 I got as a replacement. The latter is larger, and has 4-5mm more real eye relief, I would estimate

That's good to know! I shall add your reply to my 'Zooms File.'

Thanks!

Dave

[avtaram]

12 hours ago, Paul73 said:

The Baadar effort is pretty good. The FOV is limited at the 24mm end and a little soft at 8mm. But, for the money it is quite impressive.

i use mine in my travel setup. But, I wouldn't have it in place of the fixed length alternatives.

Paul

I used to think the Baader Zoom was a little soft at the 8mm setting until I realised that it needed a little more in-focus travel.

I now use a low profile adapter and find the image is pin sharp.

Avtar

[John]

22 hours ago, avtaram said:

I used to think the Baader Zoom was a little soft at the 8mm setting until I realised that it needed a little more in-focus travel.

I now use a low profile adapter and find the image is pin sharp.

Avtar

Thats a good point. None of the zooms that I've used are truly par-focal as they zoom, they have all needed a little adjustment to get sharp focus after "zooming".

 

[YKSE]

I'd like to guess that's about how the word par-focal been used. My measurement (that's what you do on cloudy nights) showed that focus positions through the zoom rang vary about 0.9mm. Not surprisingly more than fixed focal eyepieces, TV plossls for example, from 8mm to 32mm is said par-focal, the focus position difference between 32mm and 11mm is about 1.5mm.

[Stu]

I thought I read somewhere that if you use glasses but don't use them to observe then no zoom will be par focal for you. Not sure how true that is?

[Paul73]

True in my case.

a small refocus required every time.

Paul

[YKSE]

1 hour ago, Stu said:

I thought I read somewhere that if you use glasses but don't use them to observe then no zoom will be par focal for you. Not sure how true that is?

Can't think of a good explanation why it should happen. I've just measured the positions without glasses, it's the same range. Can it be so that poster made a typo that he actually meant different focus positions for with and without glasses?

Just a side note, longer focal length EPs has larger focus depth, the enomous focus depth in 50mm Revelation made it very difficult to be sure where the best focus is. With a zoom, it's often best to focus in the high mag end, then it'll be very much par-focal when zooming out, our eyes have much easier to accommodate slight defocus in low mag end.

[Dave In Vermont]

I agree that Zoom EP's need a tweak of the focus as you go through their range. Not just the Baader, my Vixen LV requires this as well. If a line of EP's claims to be parfocal - I never believe it. Experience has taught me that they may be close to parfocal, but most always need a nudge.

Dave

[michael.h.f.wilkinson]

Some zooms are considerably more parfocal than others. It is possible to design a truly parfocal zoom, but if so, it will be designed to be parfocal when the image of a star in the focal plane of the scope is converted into a parallel set of light rays (i.e. focused at infinity). If you are near-sighted, and don't wear glasses to observe, you will focus the scope such that the image of the star in the EP is not at infinity, because that is out of focus for you. The parfocal design may therefore not work.

My WO Zoom-II does need some slight refocus, at least at H-alpha, even when I am wearing new glasses, which should be corrected (nearly) perfectly.