[mental4astro (Alexander)]

I thought I'd write a few notes on my experiences with the Russell Optics eyepieces I've been lent. Again, they are:

65mm Super Plossl XL
72mm Super Plossl
85mm Super Plossl XL

The test scope I used was my Orange Tube C8, and used as a comparison eyepiece my GSO 30mm Superview.

This first use of these eyepieces was under new moon conditions under urban skies from my backyard in Sydney. I'm looking to get to use these EPs at a dark site in the next few days.

I have to say first off that the Delrin material used in the body is brilliant! It's warm to the touch compared to metal body EPs. I didn't like much the experience of exchanging EPs from the RO's to the metal ones! The fit into the 2" diagonal was fine, with the 85mm a little more snug.

Next thing to be noticed is the enourmous eye lens on these buggers. Upto 42mm in diameter with the XL's. The lenses are also noticably multi-coated.

After locating the target object of M8 in the GSO, first into the diagonal was the 65mm. Gosh! The eyerelief is extraordinary! I had to pull my head back from the EP a full inch to be able to see the whole FOV. This only got longer with the others, about 50mm for the 72, and a full 3" to use the 85mm.

The AFOV in the 65mm is larger than with the GSO, but the limiting factor with these EPs is the barrel, this is called vignetting. At 2", the FOV potential of these EPs is crippled. The AFOV is wider, it is the exact same size for each EP, but the FOV does get smaller going up in FL. This also manifests with the last 5 to 10% of the FOV loose light intensity very quickly, resulting in a soft field stop, not a sharp, crisp finish. I actually don't find this objectionable. Expecting to see this, I was not surprised to notice it, and it is not a real issue as one never really focuses on the edge of the FOV when observing.

While the eye relief was unexpected, and took a few moments to get used to it, the 65mm is actually quite comfortable to use. I can't say the same for the others. As the night wore on, I began to find the 65mm much easier to use than the GSO.

There is one draw back to using long FL EPs in urban areas, the background sky glow does get brighter. This made distinguishing the nebulosity of M8 more difficult to make out as contrast is reduced. However, the stars themselves are still nice and crisp. A quick view of Omega Centauri had the GC's image resemble that through binoculars - a fuzzy undefined ball. Concentrating a little on the image did begin to expose resolution detail, but it was faint.

I actually couldn't make out any distortion to the stars across the FOV of all these EPs. My guess, apart from the slow F/ratio of the SCT, is that the vignetting reduces the potential distortion area to outside the visible AFOV. My GSO still displayed a tiny amount of astigmatism in the very last 5% of its FOV.

This first experience was an interesting one. The 65mm is a really easy EP to use. For urban areas, this EP may not be the best choice if trying to see DSOs, but it makes a fine finder EP. The two others, not only do they show a smaller FOV due to vignetting, but the eyerelief on these is ridiculously long.

I'm excited at the prospect of using these at a dark site, particularly the 65mm. I'm hoping to be able to use these also in an even slower Maksutov scope, along side the C8, and maybe a few other EPs too. But that's a few days away if the clouds behave.

Mental.