Eyepiece diameter for small focal length planetary viewing on a large dobsonian? I have a 12" dobsonian with a 1500mm focal length and want to do some higher magnification planetary viewing. Currently my highest magnification is ~80x via my 19mm eyepiece (calculated here), but I would like to do some viewing at higher magnification.

My telescope is fitted for 2" diameter eyepieces, but I have an adapter for  1¼" eyepieces as well. I'm seeing a plethora of affordable 1¼-inch 9mm eyepieces, but very few 2" diameter options and very pricey at that.

At this point, I see the following options, by increasing price:


1¼" diameter 9mm eyepiece
3x Barlow lens
2" diameter 9mm eyepiece


I've read that the 2" eyepieces yield greater field of view advantages. Is that still true when the goal is a narrow focal length on solar system objects?

Would using a Barlow lens on my existing 2" eyepieces retain this advantage in a meaningful way?

In summary, is there any significant value in keeping to the 2" diameter eyepiece capability of my telescope when doing planetary viewing with low focal length given the magnitude of the cost difference?

I've referenced a "9mm" eyepiece here merely as an example, I'm sure most anything in the 5mm-12mm range would be fine.
I would recommend a quality 1¼" 9 mm or 12 mm eyepiece as the optimal solution. 

You already have a 19 mm so something close to that such as 15 mm would bring small difference, so take a step or two down to a 9 mm or 12 mm Plössl lens.

While a 2" eyepiece usually offers better eye relief (from bigger lens) the cost is also substantially more, and if you compromise on quality by buying a cheaper eyepiece the results will be less than satisfactory - lack of clarity, distortions from imperfections in the glass, etc.

Extra magnification can also be obtained by using a Barlow, but you are also adding extra lenses to the optical path which will slightly reduce the amount of light you are getting at the eyepiece, but also any imperfections will be magnified.

Also, with Dobsonians (usually) not having any tracking mechanisms you will be manually tracking your object of interest, and extra magnification means that it will be moving more quickly across your field of view as well as making it a little more difficult to keep it smoothly in the eyepiece. These are also arguments in favour of a 2" eyepiece over a 1¼" eyepiece, but either way, good eyepieces can be kept and re-used when/if you upgrade your telescope.