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Siebert 26mm Super-Wide Aperture Eyepiece


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Let me preface this by saying that this is one of Harry Siebert's “budget” eyepieces, being in the “performance”, or the least expensive of his fine lines of eyepieces.

I purchased this eyepiece on his recommendation, as he felt that the more expensive 2” series would not be a better match for the Celestron 5 scope, with which I intended on using this EP.

I have not yet ventured into the realm of his more pricey “Ultra” Series EP's or his Orthoscopic “Star Splitter” EP's. I am too new to this hobby to venture into the higher priced items, although I know that one generally “gets what one pays for”.

Mr. Siebert recommended this eyepiece to me specifically, because I was looking to do some astrophotography through my C5 scope and he felt that its large front lens would be best suited to my scope, without being overkill (and getting vignetting) as his 2” models might.

I have since purchased several other EP's, including a Baader Hyperion 17mm and a GSO 42mm Superview 2” EP, and must admit that in some respects, my first purchase is not appreciably bettered by the other models. Being the frugal sort, I refuse to spend $3-500 on an EP, if I am not certain how long my interest in this endeavor can and will endure. My wife claims I have a certain “history” in that regard.

Now, I understand I might be comparing apples to oranges here, but please be aware that I am interested mostly in astrophotography of basic objects (moon, planets, some easily visible clusters and nebulae) with a point&shoot camera attached via either a home-made gizmo or more recently, an Orion Steadypix with a modified holder. I have tried a variety of cameras with this combination and, so far, the Samsung HZ15W has proven the best choice for me due to the smaller front lens element, full maual control, and 12 MP resolution. It's higher ISO performance (up to ISO400) is none too shabby either.

I set up a piece of newsprint about 40 yards distant from the telescope. Due to physical limitations, I could not make it completely perpendicular to the sensor plane. However, it is enough to illustrate my point. If you look at my composite, you will notice that one or the other side of the page will be in focus, same for the top to bottom plane. The surface (a garden shed) is actually a tad below my point of view (on a raised porch) and slightly to my left. For these tests, I am actually shooting through a Celestron 8, having sold the C5 a few months prior. Without a moto-focus (this years Christmas present?) accuracy is a bit hit-or-miss, but I tried many shots and chose the best for each EP. Lighting across the page is a little varied due to lighting through surrounding trees.

So what are we actually testing here? I am looking for contrast, sharpness across the field (difficult since I am not perfectly parallel), field curvature, and vignetting with my particular camera. Obviously, your results may vary, depending on the lens of your camera.

Looking at the images, the first thing you notice is the differences in field of view and magnification. The Hyperion has a relatively wide field, but it is a 17mm lens, so it will yield a smaller area of view. The amazing thing about this lens is the difference in apparent contrast from the others. The blacks are a bit blacker and the whites are whiter. (Sounds like a laundry detergent, no?) Sorry about the page being different, but being the last image I shot, a strong gust of wind had come through and torn up the other.

The next thing you may notice is the difference in field curvature between the branded lenses and the generic Plossl. If you look closely, you will also see how quickly the edge sharpness drops off on the generic and how distorted the printed letters are towards the edge (when you can read them).

As you can see, the Siebert is no slouch against the other two mid-range Eyepieces. Flatness of field is not as good as the Hyperion, but certainly equal to the 2” GSO. Contrast, once again, compares well with the GSO, although the Baader Hyperion has it beat. Even vignetting is about equal between the GSO and the Siebert. Naturally, the Hyperion, at 17mm, will take in far less field at its rated 68degrees than the others and so there will be some compromise in the area observed.

But the Siebert is still at least as sharp as the GSO across the field, and possibly a bit sharper in the center. So considering its far smaller size and equal cost, it certainly ranks fairly high for a low to mid-priced EP. I would not try to put it up against one of the premium eyepieces for serious research, but for my purposes, would consider it a stellar performer for the price. Examples taken below shot with the C8 telescope and Siebert Eyepiece. The Barn was 1 ¼ miles distant.

I have owned only five telescopes in about 25 years. I started with a small “Jason” 60mm refractor in NY City. After moving to the Albany, NY area, I graduated about 10 years ago to a Celestron 5 on “GoTo” mount with some very basic EP's. Recently I purchased an 8inch Celestron SCT with German equatorial mount and twin drives. I also received a 90mm Meade refractor. That was a decent scope on an inferior tripod and a poor mount, but it whetted my appetite for another refractor. Recently I added an Orion 120mm f8.3 tube which mounts very nicely and is easily exchanged with the C8 on the existing equatorial mount.

Comparisons


Siebert Testing







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