Originally Posted by mental4astro
Fnski,
Do not consider the Baader Hyperion line for your dob. These are designed for refractors, SCTs and Maks as they all produce a convex focal plane. Newtonians produce a concave focal plane and these Hyperions, because of the optical mismatch will result in an image with significant aberrations that make the purchase of these eyepieces a waste of money.
These aberrations can be tolerated ( some people more than others), but the cost of the eyepiece needs to merit the compromise. Having to work with the modest budget you have, a good inexpensive 2" eyepiece for your dob would be a 30mm GSO SuperView. Also not an optical match for a Newt, but for the price the degree of aberration present is ok. If you are shelling out the same dollars that a Hyperion costs, you will find better suited eyepieces for your Newt.
The Hyperion line was most significant in my understanding of optics, in particular the relationship between scope design and EP design, and how they work to produce the final image. As if turns out, it is easier and cheaper to design and fabricats eyepieces for scopes that produce a convex focal plane. Scopes that produce a concave focal plane present a unique set of optical properties that make designing EPs to suit much more difficult and significantly more expensive to produce. Because few people take the time to properly inform themselves about optics, most of the recommendations and reviews on EPs is shrouded in ignorance and blind Brand loyalties that do nothing to progress the astro cause.
The Hyperion Zoom eyepieces actually do work really well in Newts, but the design of these zoom EPs has nothing to do with the neat single focal length eyepieces. The only thing they share in common is the same "Hyperion" name.
Another good and inexpensive eyepiece for your dob is the GSO 15mm SuperView, the smaller brother of the 30mm I mentioned above. Again not an optical match, but the 15mm shows less aberrations than its big brother. Both of these eyepieces have a generous 68° apparent field of view, which is much larger than the 52° provided by plossl eyepieces.
Another lot of inexpensive but great eyepieces for your dob are the TMB Planetary Type II line. This line while firstly designed for refractors, the complex nature of contemporary EP designs also means that some "non Newt" eyepieces can perform really well in Newts. Some better than others - take the SuperView line. The TMB line is unique that the entire line does quite well in Newts, and of course some individual focal lengths better than others, but even the poorest performer in Newts does very blooming well. I've tested the entire line fod this purpose in both Newts and refractors. The 9mm does very wel, and the 5mm is a ripper in Newts, and both of these will serve you very well. The only focal length of the TMB line I would give a miss is the 6mm. All the others for their price are great.
As for plossl eyepieces, while they are an optical match with Newts, slow ones in particular, this 150 year old design has certain practical shortcomings that newer contemporary designs leave them for dead, especially as the focal length gets shorter than 25mm. As the focal length gets shorter and shorter with plossls, the eye lens (the lens you look into ) gets smaller and smaller, while the eye relief also gets shorter and shorter until you need to park your cornea on the eye lens to look into the eyepiece.
These TMB's, making use of new glass types and newer designs mean that the eye lens across the entire line is big 20mm (yes, even for the 2.5mm!) & the eye relief is really long and easy to use. The AFOV of these TMB's is also 58°, compared to the 52° of plossls.
Now, if your budget is less restricted, it opens up other EP choices. But if you need to be careful of the $$$, the ones above will serve you very well. I still have my 30mm and 15mm SuperView eyepieces. While I've moved on to other EPs, and bought and sold dozens to have the kit I have now, I've kept these modest EPs because they are really easy for novices to use, and they are my main outreach EP's. I also have kept half a dozen of the TMB's because they are really bloody good, and I've seen them outperform $400 eyepieces!
Because of the nature of optics, I don't blindly follow brands for my eyepiece selections. Istead I use as many different EOs as I can in as many different scope types as I can, and decide for myself what works best for the different scopes I have. Most of my EPs work best with either convex or concave focal planes. Very few perform really well with both.
Alex.
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