2 inch eyepieces

[aerohound73]

Does anyone think it is better to switch over from 1.25" eyepieces to 2" eyepieces?What are the advantages of a 2" EP? Do you have a wider field of view and see more detail of the image?

[John]

The 2" eyepiece format allows a wider field of view. Thats it really so they are usually found in longer focal lengths and used for low power, wide field viewing of larger objects such as M31, the Andromeda Galaxy, the Veil Nebula etc, etc.

Many folks end up with 1.25" eyepieces for medium to high magnifications and a 2" or two for low power, wide angle viewing.

[E621Keith]

Optically 2" eyepiece can have field stop diameter greater than the 1.25" barrel limit, so a 2" eyepiece can have wider true field of view than 1.25" eyepiece.

Mechanically 2" eyepieces are larger. The 2" barrel gives a stronger connection which is very important if the eyepiece is very heavy. This is why many short focal length 100degs uses 2" barrel even though they are optically 1.25".

General long FL wide field eyepieces needs to have large field stop, so they are 2". (In fact ES is developing a 3" model). Short and medium focal length eyepiece doesn't need the large field stop, so they are made in the 1.25" format. Although now obsolete, there are a number of top quality premium planetary eyepieces in the 0.965" format as well. A 2" eyepiece does not necessary mean better quality or wider field.

[jimmyjamjoejoe]

Depends on your viewing habits really. 2" eps CAN give a wider fov, but then you get into expensive territory because wide views that are good edge to edge require some decent glass.

If you spend most of your time looking at planets, or using mid-high mags, then you probably dont need to, but if you're more of a dso hunter, then a nice widefield low power ep is a very nice thing to have.

Personally, i started out just upgrading my planetary eps, until i bought a hyperion aspheric 31mm for wide views (one look at the double cluster with one and i knew i had to buy one). After that, it got annoying switching around adapters etc, so i bought a hyperion zoom too. I keep that in 2" mode for convenience, and finally feel that between those two, i pretty much have everything i could want.

Basically, at higher mags you can still get impressive AFOVs while using 1.25". I forget the maths behind it, but as you lower the mag (increasing TFOV), you reach a limit on AFOV, because of the physical width of the barrel.

For example, you could have a 10mm 100* ep, but at 32mm, you'd be limited to say 60* unless you went for a 2" ep. I totally made those numbers up so dont quote me on those, it's just meant to show what 2" eps are all about.

[rwilkey]

I find you only need one or two 2" eyepieces for low power work, I have a 32mm and a 28mm in my collection, but you need the 1.25" for planetary and double stars etc, so don't consider getting rid of them in favour of 2", that would be a mistake.

[paul schofield]

Greater field of view with more sky to see make for me viewing through my 30mm Aero (2inch) very comfortable. I only own the one 2 inch e.p and it is also my lowest powered eyepiece too and it works a treat for low powered wide field deep sky observations.

[rory]

Greater field of view with more sky to see make for me viewing through my 30mm Aero (2inch) very comfortable. I only own the one 2 inch e.p and it is also my lowest powered eyepiece too and it works a treat for low powered wide field deep sky observations.

hope it gives nice views with the 200p. ive bagged myself a 30mm aero, but alas havn't had a chance to test it out yet. this is my first 2" too.

[crazyjedi]

All above posts have covered the differences between the two formats. The only reason I have stuck with 1.25 inch is purely financial . The cost of filters increases quite a bit which has put me off buying into the 2 inch market but I will never say never ;-)

[LeeB]

The above just about covers it , as I have a number of scopes and only three have two inch focusers, I only have one 2 inch eyepiece a 42mm for hunting. I also use a 35mm ultrascopic 1.25inch which also manages just over 2 degrees of sky in the one scope that doesnt have a 2 inch.

As above I would get a long focal 2 inch in the 32-50mm bracket and stick with 1.25 for the rest.

[John]

If your scope is an F/5 there is no point in an eyepiece with a longer focal length than 30mm or so as the exit pupil gets larger than your eye can accommodate. You are then, in effect, not getting the benefit of the full aperture of your scope.

This is why wide and ultra wide eyepieces were developed - to keep the exit pupil an efficient size with a fast scope and show lots of sky.

[spurius]

What about wide field of view at high magnification? To answer this question, please dont use acronyms,abbreviations or technical terminology. Im quite daft. Whats annoying is looking at jupiter at 300x is like trying to aim a sniper rifle at Lewis Hamiltons F1 car. My telescop mount is pretty cacas and I have to push the telescope by hand. Cheap telescopes ironically come with tripods allowing fine movement using knobs. Weird that is.

[rory]

What about wide field of view at high magnification? To answer this question, please dont use acronyms,abbreviations or technical terminology. Im quite daft. Whats annoying is looking at jupiter at 300x is like trying to aim a sniper rifle at Lewis Hamiltons F1 car. My telescop mount is pretty cacas and I have to push the telescope by hand. Cheap telescopes ironically come with tripods allowing fine movement using knobs. Weird that is.

what telescope do you have ?

[John]

If your scope is on a mount where you track things manually (ie: nudging) having a wide angle eyepiece for high power use is useful because objects stay on view for a bit longer. It's not essential but it does help. Many people here use such scopes and the technique of tracking this way soon becomes second nature, even at high magnifications.

[E621Keith]

What about wide field of view at high magnification? To answer this question, please dont use acronyms,abbreviations or technical terminology. Im quite daft. Whats annoying is looking at jupiter at 300x is like trying to aim a sniper rifle at Lewis Hamiltons F1 car. My telescop mount is pretty cacas and I have to push the telescope by hand. Cheap telescopes ironically come with tripods allowing fine movement using knobs. Weird that is.

Don't worry, those cheap telescope's mount with slow motion knobs will not hold the scope steady at 300x. It would be like trying to take a night time long exposure picture with a slow telephoto lens handheld while riding a horse running cross country.

The solution to wide angle at high magnification is a Televue Ethos SX. 110deg AFOV will give you more time to observe the object as it drifts across the field. However, they are still optically 1.25" even though they have a 2" barrel. Many low power EP wlll have a larger true field. If you routinely observe at over 200x, you should consider investing in a mount with tracking capability.