your favourite (most useful) actual fields of view

[troypiggo]

So many variables choosing these eyepieces, but I figure the simplest way to break it down might be the end result in terms of the actual field of view you see at the end of the day. Forget apparent field of view, eye relief, focal lengths, apertures, magnifications.

What are your favourite (most useful) actual fields of view? You can choose up to 3. Would be helpful to explain why.

[Wavytone]

Evidently you have been infected with the Ethos disease...

Field of view is only relevant at low powers where maximising the true FoV s a priority.

At high powers on small objects field of view is irrelevant - the priorities are magnification and image quality.

[troypiggo]

I'm not really thinking of any particular eyepiece. When looking at different makes and models, there's 68, 65, 50, 82, 100 deg (and more) apparent fields of view, and each of those coupled with EP focal lengths affects the true field of view. Unless I'm missing something?

I just figure that what you see in, say, a 68 deg apparent FoV eyepiece at a particular magnification is the same as what you see in an 82 app FoV EP, just the latter is a higher mag.

Is the magnification more important, or what you see in the eyepiece field of view? Maybe I'm thinking of it more of a composition/photographic standpoint?

[JethroB76]

I had a perfectly good Denkmeier 21mm EP that gave similar TFOV as my 13mm Ethos but at a somewhat lower mag. It just didnt get used and I sold it. Being able to see relatively extended objects at a higher mag with a darker background makes the wider FOV worth it to me.

I bought an 8mm and am still tossing up whether to get a 21 or 20mm 100* EP

[Wavytone]

1. 180 degrees, naked eye, lying on the ground looking up.

2. 3.8 degrees, mainly for locating objects and rich-field views of Milky Way

3. 1 degree, DSO's.

4. 0.2 degrees, high power (planets)

[mental4astro]

Hi troypiggo,

I believe I see where you are coming from, but I don't see just how relevant the "wide field view" is when if your scope is a 8" f/15 mak and another's is an 8" f/4. Using the same EP will produce very different results.

I love my 17.5" f/4.5 dobbie, and I mainly use a cheapie 68* EP. My favourite wide view scope, though, is my new 8" f/4 newt. coupled with a 30 year old 28mm RKE eyepiece with its modest 50* FOV. I can interchange these two eyepieces, but they work very differently in each scope.

Would a more expensive Wide Field of View eyepiece make a difference to my visual experience? Maybe. But it adds complications to short f/ratio scopes.

That's all I'm getting at- it is a function of EP properties vs. scope and its ratio. I find it hard to make a valid judgement on the value of what would be an actual field size.

To that I also would add that I wouldn't go near an 82* or wider eyepiece. I find them too difficult to use visually. I have human eyes, not those of a falcon, so I'll distinctly limit myself to my physiological limits, not my pocket's.

Should make for even more interesting discussion.

Mental.

[mental4astro]

Touche!

[troypiggo]

Excellent. That's the sort of thing I was after. :)



Exactly. That's why I'm not asking about a particular EP, I'm asking about the fields of view.



Maybe I'm not being clear. I don't really care what scope or EP you're using. I'm interested in what you actually see when you put your eye to your eyepiece.

Let's break it down. With your 17.5" dob, think about what EP do you find is your favourite and/or most useful. Now, what field of view is that giving you? ie what size objects can you see with it? That's what I'm after.

[mental4astro]

I hear you Troy. Yet that's why I still say it is all a function of the scope and EP. Many of us have a two or more scopes, each with their own strengths and weakness's. Each with different fields of view.

Wavy gave a selection of fields, yet it will depend on the scope. No 17.5" scope/ep combination will give me a 3.0* view. If this is my only scope, then how can I vote on the poll when I'll never achieve this? That's my point.

[troypiggo]

If your scope/EP combination won't give you 3 deg view, it won't be your favourite or most used. It's Wavy's, not yours.

What is your most used scope/EP combo and what view does it give you?

[mental4astro]

Got you mate.

Being arguementative too, :rolleyes:.

Mental.

[Wavytone]

Well I didn't reveal that, did I ? To point out that it is irrelevant, for the most part. Which is why I am not particularly impressed by those squandering buckets of moolah for 100 degree AFoV eyepieces - more than the rest of the scope, probably - while rather more modest 50 degree designs made specifically for f/4 Newtonians can give better image quality, the better contrast, and a unique user experience.

[peter_4059]

Hi Troy,

Just checked Astroplanner with the 13mm LVW and the 10" f5 Newt and came up with 39.921'. I reckon there is no substitute for a back to back comparison - bring on astrofest!

[Wavytone]

Well... If you want a shoot out, I can offer the LVW 5, 8, 13, 22, the NLVW 30, a TMB 30, TMB 40, Vixen LV 50 and VERY rare beastie, a Masuyama 45mm.
Plus a set of Vixen LV's.. As for scopes... a 102mm ED f/7, 180mm f/10 Mak, or f/15 Mak.
The showdown: Katoomba, 17th April.

I'm sure Alex will bring bring the RKE's, just to embarrass the Nagler owners.

[pgc hunter]

I only worry about TFOV when observing large objects (e.g. Rosette, Eta Carina), or when doing widefield Milkywy sweeping. When hunting faint fazzies or planets, magnification and image quality take precedence over TFOV.

[troypiggo]

Thanks for your comments, guys. I guess I have been looking at the requirements from the wrong direction. It seems that magnification is more important than what you see in the field of view.

[pgc hunter]

Well it really depends on the object you are viewing. If you're observing large, extended targets which are best seen at low power, wide fields like the Rosette and Viel Nebulas and large open clusters for example, FOV takes the front seat over mag. But for small targets like planets, Planetary Nebs, most galaxies, compact diffuse nebs etc, FOV is generally irrelevent, you'll be experimenting with magnification instead to get the best view.

[Wavytone]

According to what you are looking at, either maximum field of view (limited by the eyepiece barrel) or maximum magnification limited by the seeing - field of view is NOT relevant on small objects. Depending on the night that could be anywhere from 100X to 300X.

In both cases image quality and eyerelief are important and I'm happy to settle for a smaller field of view for an eyepiece that is comfortable (eye relief), contrasty, sharp, well-corrected view free of ghosts.

[Lismore Bloke]

My favourite EP is the Nagler 12mm T4, great for galaxies.

[casstony]

That's a fairly universal answer that most could agree with I think. I bought a 6"f/5 achro to get 3 degrees and I use my C11 for up to 1 degree on DSO's. My skies rarely let me use high power.

There are so many variables with eyepiece choice (budget, AFOV, transmission, contrast, sharpness, eye relief, weight, eyecup width) and combined scope/eyepiece performance (field curvature, astigmatism, coma) that one observer can't assume they'll like the same eyepiece as another; the best you can do is get recommendations to try for yourself.