Eyepiece Startup

I am awaiting the new Orion 10" Intelliscope. After much research and agonizing I have decided to go with this as my starter set of EPs.

It comes with a 25 and a 10 and I was planning on adding a Nagler 11mm along with a Televue 2x & 3x barlow. This will give me:
48x 25mm
96x 25mm with 2x barlow
109x 11mm
120x 10mm
144x 25mm with 3x barlow
218x 11mm with 2x barlow
240x 10mm with 2x barlow
327x 11mm with 3x barlow
360x 10mm with 3x barlow

I know the 11mm Nagler is close to the 10 that comes the scope but I think that range of mag is good and hopefully the Nagler will provide a better view than the supplied EP. At least it will have a larger AFOV.

Any suggestions?

I would recommend that you concider another EP. Maybe a Panoptic 19mm or a Nagler 16mm as they are in the same price range and would make a better spread in the coverage of your EPs. They are both 1.25" EPs and would be nice.
The 11mm, is just too close to the 10mm. Also remember that you will probably get other EPs later and you want to have a good selection of focal lengths in the end.
The 25mm = 12mm with a 2x barlow, too close to 11mm and 10mm. The 16mm Nagler would give 8mm and 4mm with your barlows. The 19mm Panoptic would yeild 8.5mm and 4.25mm.
327x and 360x is probably pushing beyond the usable limits of your scope except on a perfect night. Even then it will be pushing. You need to stay around 240x and less for good viewing and you need wide field to see some neat objects like globs and nebulas.
The 3x barlow is going to make your view get might dark with only 10" of aperture if you ask me. Might be better off with just a good 2x barlow or maybe a 2.5 PowerMate, but they are expensive.
Usually the 8.8 Meade UWA is about all I can use on the 15" DOB. Sometimes the air is good enough to allow more but rarely. SO don't go for all high magnification, you need low mag with wide FOV too.
My $.02 worth! :^)

Floyd

Kenny,

In my opinion there are 3 eyepieces that are really important in a collection.

The first one is the lowest power eyepiece that you would reasonably use. For your scope that might be an eyepiece in the 30mm to 32mm range. (A 32mm eyepiece would yield a 6.8mm exit pupil)

The second eyepiece is the common high power eyepiece that takes in account your local seeing conditions, your scope's optical quality, and whether or not the mount is driven. In my opinion it's a pain to push a dob at over about 200x. For that you're looking at something around 6-7mm (200x @ 6mm)

That third eyepiece is the one that splits the difference and finds a happy medium in both magnification and true field. Something in the 14ish mm range might be ideal.

So where am I going with this...

My suggestion: Don't bother with the barlows and look for 3 good eyepieces in the above focal lengths. It looks like you were prepard to spend about $500 for eyepieces/barlows. If that's a fixed budget, I'd suggest something like a 7mm & 14mm Pentax XL and a 30mm Ultrascopic. If you shop around you might be able to swing the 3 for about $500.

Why ditch the barlows? They add more glass into the optical train and it can be a pain to constantly switch eyepieces in and out of them. I find myself rarely using barlows unless I need/want a really high power view and I don't have an eyepiece with a short enough focal length available.

-Bret

I hope you like Barlows - I'm not ultra fond of them (though, I've got four of them). As far as I'm concerned the view is never quite good as in the straight eyepiece, though I'm told Powermates are much better

The best exit pupil for detecting and viewing galaxies and most other faint DSOs is 2mm. Your 10mm delivers that. If that's the focal length you use the most, then upgrading to a Nagler makes sense, the only question is whether to get a 9 or 11mm - I'd go for the 9mm.

Anyhow, if I were you, before starting the spending spree, I'd just get one 2X Barlow and start getting a feel for what powers you use the most during actual observing. Also, if you get an extension tube (e.g. like a long filter adaptor) it will increase the magnification of your Barlow.
Renato

I recommend building your eyepiece collection around four "magic" focal lengths that maximize different aspects of your telescope's performance. I call these eyepieces the Maximum Light, Maximum Field, Maximum Definition, and Maximum Resolution eyepieces.

The Maximum Light eyepiece is the unique focal length where both the total amount of light in the eyepiece, and the brightness of individual objects, are at their maximum possible value. This is the focal length where the exit pupil exactly matches the size of your eye's pupil. You can get the exit pupil by dividing the focal length of the eyepiece by the focal ratio of the telescope. For young people the eye pupil size is around 7 millimeters but usually decreases to around 5mm by middle age.

The Maximum Field eyepiece is a low-power eyepiece that has a field stop almost as large as your telescope's drawtube. Since most manufacturers don't specify the field stop, you can get an approximation by multiplying the focal length by the apparent field of view. For 2-inch eyepieces, to get a very large field stop this number should be in the area of 2500; for 1.25-inch eyepieces, around 1700.

The Maximum Definition eyepiece is a high-power eyepiece that yields a very "smooth", sharp image for planetary viewing. I find that about 25x per inch works best for me. When the power gets above this the image starts to become "grainy" due to defects in the eye that become obvious when the exit pupil is less than a millimeter.

The Maximum Resolution eyepiece is the oft-quoted limit of 50x per inch, beyond which further magnification is usually useless.

You'll need at least one more focal length to fill the wide gap between the Maximum Light and Maximum Definition eyepieces. If these magnifications are 5x and 25x per inch respectively, I find that about 15x per inch is a good choice. I don't use magnifications slightly above Maximum Light (8-10x per inch) very much because the small gain in visibility doesn't really offset the disadvantage of a smaller field of view.