Unfortunately, to truly deal with the steep light cone and get excellent edge correction I would need very expensive eyepieces. I must again refer to my rule that no new piece for the scope can cost more than the scope. Oh well, so much for the Nalgers.

Fortunately, at this time, what I have is good enough for my viewing needs.  Here's what's in the eyepiece case as of now.

I still have the original eyepiece that came with the scope. It is presumably a Kellner and from what I can gather it is 27 mm. It probably started out life as a binocular eyepiece as it has a diopter setting. This is very rare in telescope eyepieces and Coulter likely shipped these to make up for the lousy focusing ability of their focuser. It came shipped in the same black and white boxes stamped "Made in Japan" that my much newer Antares eyepiece came in. The eyepiece actually works pretty well. I'd say it has about a 50° apparent field of view. On deep sky objects it is okay but on bright objects it suffers from internal reflections. This is not surprising for a Kellner. How often do I look at planets with a 27 mm eyepiece anyhow? I recently replaced it with the 30 mm eyepiece described below. I still pull out the Kellner for star parties when I don't want to have kids sticking their fingers on the 30mm's coatings.

coulter kellner picture coming soon

 

I recently replaced the 27mm Kellner with this Celestron 30mm Ultima eyepiece which is actually a five element masuyama design. What a difference! I am very satisfied by the new eyepiece. It has a 51° apparent field of view. The eye lens is about twice the diameter of the 27mm which makes viewing a joy.

 

Ultima 18 picture coming soon

My middle of the road eyepiece is a Celestron Ultima 18 mm. It was my first of the three masuyama eyepieces I now own. I was comparing it with the Antares Ultima and the Orion Ultrascopic (both essentially the same eyepiece sometimes called a super plössl.) I settled on the Celestron because it came in an 18 mm size whereas the other two came only in 15 mm. At the time I did not have the 30mm Ultima but knew I would add it in a year. The 15 mm would have been a waste as I can always throw the 30 mm into a Barlow to get the same magnification as the 15 mm. Because of exit pupil considerations I don't want to go to a 32 mm eyepiece in this system. The Celestron was a few dollars less expensive as well which doesn't hurt. It has a 51° apparent field of view. Interestingly, the Orion Ultrascopic and the Antares Ultima both boast a 52° apparent field of view.

Moving down in focal length I have the 12.5 mm Celestron Ultima which provides me with 72x (144x barlowed). It is also a nice eyepiece, very similar to the 18 mm. This eyepiece also has a 51° apparent field of view. 12mm is the "sweet spot" of this scope.

Ultima 12 picture coming soon

I do have one eyepiece that I hasten to even mention. It is a .965 inch Japanese made 20 mm Huygen that was manufactured by, you guessed it, Tasco. It has a very narrow 32° apparent field of view. I had this eyepiece sitting around from an old catadioptric f/7.9 "Tanzutsu" Tasco telescope. I bought it in fourth grade and the scope cost about $30 at a close-out store. It is the same one now sold by Celestron. The only difference is that it is now sold on an alt-azimuth mount and costs $100. It wasn't worth the $30 let alone $100! I wrapped this old eyepiece in electrical tape and friction fit it into a 35 mm film canister so it would fit in a 1.25” focuser. At the time, I had only the 27 mm eyepiece and any other eyepiece was welcome. I also liked that it had a moon filter so that made it useful to keep around. I naturally don't use it anymore as it is outpaced by the 18 mm Ultima but I mention it because it is nice to remember that the people who came before use didn't have nice computer designed super wide flat field eyepieces and they probably would have thought my little Huygen was pretty high tech. I've barlowed it for decent views of the ring nebula before and it produced a fairly bright sharp image. While the apparent field of view is very narrow (like looking through a paper towel tube) you can still see the object you're observing.

The first new eyepiece I bought when I got back into the hobby was a 6 mm Antares Orthoscopic. Antares is sort of a generic brand. All of their products are made by the same manufacturers used by the large brand name companies. The difference in cost usually reflects that the original company is trying to re-coup development and advertising costs. For example, the Antares dob telescopes are simply the pre-digital setting circle Orion SkyQuest line. Now, my scope is really not optimal for looking at planets being that it is f/4.5 but I do enjoy it so I wanted a crisp high power eyepiece. The Orthoscopic is a good design for planets as it has only 4 elements and helps to maintain details. It has a 45° apparent field of view. With a dobsonian, the widest possible actual field of view is important as the target object being observed will move out of the field quickly. This is especially important at high magnification. I could have gotten slightly more true field of view with an Ultima eyepiece like the 18 and 12 mm above but in theory the 4 element Ortho should give slightly better images of the planets. The ultima should have .04° more actual field of view than the ortho. I have read that orthoscopics are not so good for fast scopes like mine as they have trouble keeping up with the steep light cone. There may be some distortion at the edges of the field but I don't usually view Jupiter at the edge of my field of view now do I? I actually haven't noticed much of any problem with this but the eyepiece is still relatively new and I don't use it that often so the jury is still out. I will probably never be able to tell as this scope is not good for planetary viewing. The Ultima is probably a better eyepiece for this scope. Oh well.

I have the ubiquitous orion 2x shorty barlow that does the job. It is also fairly new though so I won't comment on it until I put it thought the paces.

With my eyepieces I get the following magnifications and fields of view.

Eyepiece focal length	Power	Apparent Field of View	Approx Actual FOV	Design	Manufacturer
30 mm	30x	51°	1.70°	Masuyama	Celestron
27 mm	33.3x	unknown		Kellner	Coulter
20mm	45x	32°	0.71°	Huygen	Modified Tasco
18 mm	50x	51°	1.02°	Masuyama/ Ultima	Celestron
30 mm + 2x Barlow	60x	51°	0.85°	Masuyama/ Ultima	Celestron
27 mm + 2x Barlow	66.6x	unknown		Kellner	Coulter
12.5 mm	72x	51°	0.71°	Masuyama/ Ultima	Celestron
20 mm + 2x Barlow	90x	36x	0.36°	Huygen	Modified Tasco
18 mm + 2x Barlow	100x	51°	0.51°	Masuyama/ Ultima	Celestron
12.5 mm + 2x Barlow	144x	51°	0.35°	Masuyama/ Ultima	Celestron
6 mm	150x	45°	0.3°	Orthoscopic	Antares
6 mm + 2x Barlow	300x	45°	0.15°	Orthoscopic	Antares

I also have an Orion Narrowband nebula filter that does a great job of filtering out the ever-present sky glow from the twin cities and suburbs. I do not have the broadband "Sky-Glow" filter as it really doesn't do enough with the amount of pollution present in many local viewing areas. There was a pathetic 20 week backorder on the nebula filter. The whole astronomy industry needs to get their act together! My moon filter is from pro-optic. I went with their filter because it can be stacked with other filters whereas many of the other brands cannot. In reality, this isn't necessairly true. All moon filters can be stacked provided the other filters being used are threaded on both sides.  The moon filter could always be the last one in line and it wouldn't matter. I just like being flexible. I recommend an aperture mask when viewing the moon with the filter as it is still very bright with all 8 inches of mirror collecting light.

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