Is wide angle wasted on planetary viewing?

[Bart]

Hi All,

I've read somewhere that wide angle is wasted on high power ~200x viewing. Does anyone have any views on this. The reason I ask is that I am contemplating either an Explore Scientific 82 degree giving me about 190x for about €110 or a TMB Planetary 58 degree giving me 208x for about €45 for a 10" Dob. Is it worth the extra money. Thanks for any comments or suggestions

Bart

[Breakintheclouds]

I'm sure you'll hear both sides of this one, but generally I'd say that very wide field of view (>60 degrees) isn't really worth the candle. Traditional planetary eyepieces such as orthoscopics have very narrow fields of view, but people are fine with that as you're focusing your attention on something very small in the centre anyway.

But having said that, what I personally value more than FOV is eye relief. For planetary viewing, although my Baader genuine ortho is technically the better eyepiece, I find myself using my cheaper TMB planetary a lot of the time just because it's more comfortable to use - the ortho requires you to be scaping the glass with your eyelashes. It also gives a wider field of view than the Baader, but I don't think I notice it at all. And perhaps that answers your question?

[Bart]

Thamks Breakintheclouds, yes, I kind of expected your reply.I have to say, I'm tempted by the 82 degree but suspect it'll be a waste. Does having a wider angle mean less nudging in a Dob, or does it make any difference?

[daz]

I seem to remember that most planetary observers will want want a narrow field of view to get better contrast on a planet's features - orthoscopics for example.

The degrees you mention, as I'm sure you know, are apparant field of views - what would give you a better idea is the true field of view for your scope.

Here is a link to a formula that shows the calculation: True Field of View calculations - Forums - Astronomy.com - Online Community, Forums, Media Galleries, Blogs

After all this, it is of course, a purely subjective view if you want to observe planets in a wider angle

[Nibor]

I seem to remember that most planetary observers will want want a narrow field of view to get better contrast on a planet's features - orthoscopics for example.

The degrees you mention, as I'm sure you know, are apparant field of views - what would give you a better idea is the true field of view for your scope.

Here is a link to a formula that shows the calculation: True Field of View calculations - Forums - Astronomy.com - Online Community, Forums, Media Galleries, Blogs

After all this, it is of course, a purely subjective view if you want to observe planets in a wider angle

For a FOV calculator is this worth a try??

Field of View Calculator | Sky at Night Magazine

Note:- the default calculation is for use with a camera! However you can switch to the visual mode option.

I have found it very helpful in understanding my kit's characteristics.

[dweller25]

I'm a planetary observer and use Pentax XW's because .....

1. They have 20mm eye relief.

2, They are reasonably wide angle so I don't have to nudge much with the Dob.

3. They are sharp.

BUT I find Baader Orthos and TV Plossls to be just as sharp but not as comfortable.

[daz]

That's the one from 12DString - http://www.12dstring.me.uk/fov.htm - but Yes, will do the job and show the FoV on objects as well

You can also input details of EPs that you have and are not in the list

[daz]

Eye relief is indeed another factor to consider, as others have intimated.

As a spectacle wearer, I actually take mine off to observe with and prefer to have my eyeball up close to the lens, but again, this is a subjective opinion.

[NGC 1502]

Does having a wider angle mean less nudging in a Dob

Hi Bart, yes, a wide angle will mean less nudging. However, the wide angle/less nudging idea is only useful if the eyepiece gives sharp to the edge views. No point (in my opinion) if the view is only sharp in the centre, you will still be nudging to keep your object away from the edges.

I've been hung up on long eyerelief for years and love my Radians and Vixen LVs for that reason. But recently I borrowed a clubmates

Nagler 9mm type 6, with "only" 12mm eyerelief. I was surprised to find that I had no problems at all seeing out to the field stop, and it was sharp to the edge in my 10" Dob.

Good luck in your choice, Ed.

[cgarry]

I have never understood the idea that planetary observers "want" a narrow field of view. They may be happy to put up with a narrow field of view as their target is small, but I cannot see how a narrower field of view improves the detail of the planet.

Personally I prefer a wider field of view, that way I get to see all the planets moons and close by stars rather than being restricted to the planets disc. For me this puts the planet into context and makes observing it more enjoyable. Also these high power EPs are likely to be pointed at the moon once in a while and in that situation a wider field of view really improves the view allowing you to explore.

As others have said there are various other factors to weigh up before making your EP decision, including cost. Good luck!

Cheers,

Chris

[John]

I'm very firmly in the "very wide field of view desired" camp with regard to all my observing, high power planetary and lunar included. The fact that I use undriven, alt-azimuth mounts is a factor as well of course but I do like the wide views too

Over the years I've owned and used many of the the more established planetary eyepieces such as classic "volcano top" and Baader Genuine orthos, Tele Vue plossls, Celestron Ultimas etc and enjoyed them but I've concluded for now that, for me at least, my Ethos / Barlowed Ethos eyepieces deliver comparable sharpness, contrast and light scatter control and to that add more comfortable eyerelief, large eyelenses, and the very wide angle of view that I crave

I suspect this is a topic that will be driven very strongly though by personal viewing preferences rather than "right or wrong" and fortunately the market offers something for every taste, and budget, at the moment

[Macavity]

If I'm trying to use higher magnification (typical for planetary viewing?) I tend to "lose" NARROW exit pupils in large areas of eye-lens glass. So, rather than simply field of view, I found e.g. "HR planetary" eyepieces easier to USE than Baader Hyperions. Maybe I'll eventually graduate to traditional Orthoscopics (whatever). On the other hand, I don't *do* short eye reliefs well.

If you're manually pushing a scope it's desirable to keep ANY object in field for longer times?

[MatthewC]

I use a 9mm Nagler and a 7mm Nirvana on planets. The benefit of having the 82 degree fov is a lot less nudging and more time observing.

[PeterW]

Dobsonian... go wide angle so you don't lose what you are looking at. I got a 5mm Nagler for that reason. Modern eyepieces are pretty good, so you shouldn't lose much. If you had a tracking mount and were mainly into planets then there are nominally better choices.

Cheers

PEterW

[andrew63]

If you can handle the short eye relief - A good plossl eg. TV would virtually match an ortho for detail and have the slight benefit of a 50 deg rather than 40ish - that can make a small but noticeable difference.

andrew

[johninderby]

I'm also in agreement with using wide angle eyepieces for planetary observing.

There was a comparison test a little while ago on Cloudynights where they compared the Ethos to Zeiss Abbe orthos for lunar and planetary observing. The result was essentially a tie with the opinion that if forced to choose the Ethos would be the winner.

Another factor that can affect the perception of better sharpness and contrast in an ortho eyepiece is that with such a narrow FOV you are concentrating on just that small area. With a wide angle eyepiece there's simply a lot more to look at so you tend not to concentrate on a small area, and even though the eyepiece may be showing just as much detail as the ortho, it's not so obvious at first glance. You have to adopt a different observing technique with the wide angle eyepieces and learn to focus in on small areas.

John

[John]

...There was a comparison test a little while ago on Cloudynights where they compared the Ethos to Zeiss Abbe orthos for lunar and planetary observing. The result was essentially a tie with the opinion that if forced to choose the Ethos would be the winner.....

Wow

I knew the Ethos were good but I didn't realise they were that good.

I'll have to look that report up.

[andrew63]

to get it in a bit of perspective - as lovely as an ethos lens is, a lot of people are unable to buy one as a planetary eyepiece - after all you could almost buy a complete set of TV plossls for the same price!

a lot of us use ES Meade Celestron UWA and work just fine for that purpose if you need a wider view than 40 to 50deg.

andrew

[michael.h.f.wilkinson]

I use Radians for planetary work (60 deg FOV) which was a real improvement over Vixen LV (45 to 50 deg FOV). When I got my 8mm Radian, the 9 mm LV (50 deg) and even more so the 45 deg 7mm LV felt cramped. The main reason I avoided short focal length Naglers (and orthos I used to have) is their poor (abysmal in the case of orthos) eye relief. 60 deg gives a slightly nicer view, especially with Jupiter's moons. It also makes finding them easier, because you do not first have to centre things carefully in the wide field EP. A Delos at 72 deg sounds very tempting indeed.

The wider field is also useful when finding planetary nebula, many of which can take (or even need) high magnification, because they can only be distinguished from a star at high mag. At Olly's place we used about 150x magnification with my 14mm UWA, which was very useful on NGC 6891

[John]

to get it in a bit of perspective - as lovely as an ethos lens is, a lot of people are unable to buy one as a planetary eyepiece - after all you could almost buy a complete set of TV plossls for the same price!

a lot of us use ES Meade Celestron UWA and work just fine for that purpose if you need a wider view than 40 to 50deg.

andrew

Thats a good point Andrew, the original question was on the value, or otherwise, of a wide field of view for planetary observing

[JamesC]

Wide angle = less nudging in an undriven mount.

Long eye relief = much more comfortable to use and better for sharing views.

Sharp to the edge = I wouldn't like to compromise on this in a planetary eyepiece.

Personally I find 60 degrees at 250 times is adequate. That would suggest that 50 degrees at 200 times would also be adequate, but the more the better.

[rwilkey]

I prefer wide-field and good eye-relief over everything, a wide field glass is incomparable when viewing anything like planets, the object remains the same size whatever, but the net result is longer and more enjoyable viewing times in my opinion, my question is, why not make viewing easy - It is then more pleasurable surely?