Widest possible FOV using an 8" dob

Hi all,
I recently bought a used Orion SkyQuest XT8 Intelliscope with a 2" focuser through Astromart and even more recently bought a GSO 30mm SuperView 2" eyepiece to use in my new scope. This is my first scope with a 2" focuser. After comparing the 30mm GSO with a 32mm Plossl (1.25" format) I saw very little difference in the star field around Deneb when comparing the two eyepieces. Any advise on which eyepiece to get for a wider true field of view? I'd like to buy something which would encompass the whole of the Veil Nebula. I realize this may not be possible in an 8" f/6 Newt as it is not a wide field type of telescope. I can't really afford the premium eyepieces, so please don't recommend anything over about $150.
Thanks,
Warren Boyles

Warren: The entire Veil Nebula would require a true field of view (TFOV) of at least 3º. I had the same wish to see that entire object in my 80 mm refractor a couple of years ago, and for about $100 I obtained a 30 mm BW-Optik 2-inch eyepiece from Anacortes that did the job.
But I don't think you can accomplish your objective with the 8-inch f 5.9 Newtonian. With a 30 mm eyepiece you would need one whose apparent field of view (AFOV) is about 120º, and I don't believe that exists; I think the best you could do is to get a TFOV of about 2º with a 41 mm eyepiece that has a 68º AFOV, like a Panoptic, but even that would cost much more than $100. Sorry about the negative response, but I think you alreay knew this answer.

Warren:

The GSO SuperView should give a noticeably wider field of view than the 32mm GSO Plossl but the difference is not huge...

Fitting the entire Veil in the eyepiece is not going to happen in an 8 inch F/6 Newtonian/

The TFoV is determined by the field stop of the eyepiece, the field stop size is limited by the barrel inner diameter, the 2 inch format has a larger diameter so bigger field of views are possible.

The TFoV can be estimated from the focal length of the scope and the field stop of the eyepiece...

TFoV= 57.3 (degrees/radian) x (field stop diameter scope) / (focal length scope)

In the 1.25 eyepiece format, the maximum possible field stop is about 28mm which means that in an 8 inch F/6 scope, the maximum possible TFoV is about 1.3 degrees.

In the 2 inch format, the maximum possible field stop is about 46mm which yields a TFoV of about 2.2 degrees, a whole lot bigger than the 1.3 degrees you were looking...

Expensive Options are various TV eyepieces like the Nagler 31, the Panoptic 35mm and 42mm, these will give you a TFoV of over 2 degrees. But the are out of the ball park for both of us..

An inexpensive option is the Superview 42 which has no field stop but has other restrictions which make for an effective field stop diameter of about 42mm, again a 2 degree FOV. I have one of these, for the money, I think it is an OK eyepiece, not sharp at the edge but it does have a large field of view and is nicely made. The 7mm exit pupil is an potential issue.

Some are quite happy with the Orion Optiluxe eyepieces, I have never used one.. Lots of options, lot of prices, lots of issues...

There is no perfect eyepiece, getting one that suits your budget and provides pleasant views is the goal, and each of us has different tolerances for various aberrations. The biggest aberration is the monetary spending cash aberration which can be quite troublesome, especially with other family members.

Jon

This depends on what you mean by,"the whole veil." The veil has two separate brighter sections, with dimmer areas in between. In my 8" f 5.7 (which is f6 for practical purposes), the larger section on the veil will not fit into a 22m panoptic, which is just over 1.2 degrees int that scope. For about $75 dollars the larger section of the veil will look very good in a B&W 300mm 80 degree eyepice, but the stars in the outer 35% (or more) of the field won't. In either the Siebert 34mm or 36 mm (what i use) observatory grade ($200 new, sometimes seen used for about $150), the veil will look great, and the stars will be much better. You can also get the separate section and the dimmer nebulosity in one view, under very dark skies.

I can get both in the Siebert with my 80 mm, but I confess that the two views in the 8" are in a different league.

Good luck,
lorne Johnson

Another possible option for you is the 2" UO MK70 (70 degree AFOV)which you sometimes find used for around $150.00. Another is the Meade 56mm 2" Plossl. I think the Meade is pretty reasonable new. Also, I have seen a few TV 55mm Plossls second hand for around $150.00. Using the formula Jon gave you can figure out your true fields. The Plossls have an apparent field around 44 to 50 degrees...you will have to check the manufacturer.

The UO MK70 I do own and it works great in my C14. It is supposed to fall off at shorter focal lengths but will probably be OK at f/6.