Long story short, my old mentor Jens Østergaard Olesen passed away in January. The widow had given his old 110/1650mm Steinheil refractor to a newly started, local astronomy club, who then decided to sell it to me for a song, because they realized that a restoration was way out of their league, and that selling it to someone else would mean a very complicated and expensive shipping job.
I've seen the scope in his observatory many years ago, but never actually used it. Jens mentioned once that it had a zone in the objective and that images weren't super crisp, although quite useable at low to medium magnifications. He preferred to use his Zeiss Meniscas 150/2250, which I can easily understand, owning one myself.
I picked up the scope Saturday forenoon, along with its mount and pier, and the original eyepiece box. The mount and pier are not original Steinheil, but made in Denmark by Astro Mekanik in Aalborg, so they're also historically interesting. The mount is in more need of attention than the telescope, and I've not started work on it yet. Meanwhile, I made an adapter plate so that I could use the Steinheil on my Vixen Saturn mount. The Steinheil sits on the Saturn as if they were made for each other. I didn't even need to move the counterweight.
The scope needs some love and care, but is otherwise in quite good condition. The OTA is hand painted, and not very pretty at the moment, but not rusted or badly corroded. The tube is steel or iron, with the lens cell, focuser housing and finderscope holders made from some kind of alloy. It's gray and oxidizes into some gray-white fine powder. Focuser countercell and drawtube is brass, as is the finderscope. Everything except the focuser drawtube is painted, as it was originally, though the paint is not original.
The 8x25 finderscope is massively overbuilt, with five (!) or so internal baffles. The eyepiece is a 30mm Mittenzwey without crosshairs. Contrast and sharpness is exceptional for a finderscope. It is ridiculously overbuilt. The AFOV is not super large, about 40°, so centering an object accurately without crosshairs is actually very easy. Eye relief is good, and the very tall holders keep it well away from the main scope, making it fairly easy to look through, even at high altitudes. The eyepiece and objective were dusty and a little greasy, but after a simple cleaning they looked immaculate.
The focuser is very big, and very, very strong. It will need a cleaning and the brass needs polishing. It has many baffles, but I've not counted them.
The tube has been painted with a brush at some time, and not very professionally... It needs to be stripped and repainted. The same with the tube rings. There are a LOT of baffles in it. I counted at least 11!
The three tiny screws holding the objective to the countercell were missing, but I found some prefect replacements in my "Big jar of tiny screws that might come in handy one day". 
The objective was lightly dusty, and had what appeared to be a water stain between the lenses, but looked otherwise perfect. I gave them a light cleaning and put the objective back on the scope and regreased the focuser with WD-40.
After thus giving the OTA a first inspection, I made an adapter plate for it, so that I could mount it on my Vixen Saturn mount. This took less than an hour, as I already had a suitable plate lying about, I just needed to drill holes. Sunday forenoon, I was ready for first light. The scope came with an adapter for 1.25" eyepieces. I used my INTES Herschel wedge and a 21mm Hyperion. First views were mixed. I could see some good details, but contrast was mediocre. If I refocused, I could find a position with great contrast, but soft details... Hmmm. Not exactly promising, but I needed a star test to be able to tell exactly what was going on, though I had a suspicion that it wasn't a zone.
Sunday evening was crystal clear, but with a brisk wind. I set up right after Sunset and took a look at the Moon, using a 17mm Hyperion. I immediately saw the same thing as on the Sun. And now my suspicion grew even stronger: It wasn't a zone, it was spherical aberration. By carefully focusing, I could find a position, where the detail was rather good, and there was minimal haze. And the image got better as the scope cooled. This was textbook undercorrection behavior. As soon as I could see Capella, I aimed the scope at it and did a star test, using a 10mm Hyperion, which removed any doubt: Textbook undercorrection. And quite a lot of it. I estimate at least a wave or so, certainly more than a half wave.
But the views, with careful focusing, weren't all that bad at 165x. In fact, they were quite good, when seeing allowed. And there was extremely little false color. So little, in fact, that I will argue that this must be some kind of semi-apochromat. There is much less false color than my 80/1200mm Vixen achromat! Here's a photo through the 10mm Hyperion at 165x:
I also tested the original eyepieces. There's a 25mm (66x), 15mm (110x), 10mm (165x), 7.5mm (220x) and 5mm (330x). They have an unusual diameter, 28mm, but the top is slightly larger, making an almost perfect fit into a 1.25" diagonal! They were all sharp, but somewhat hazy, probably from greasy lenses. AFOV is about 40°. Eye relief range from fairly good on the 25mm to non-existant on the 5mm. The eye lens on the 5mm is less than 2mm across! The little bag contains the original 28mm eyepiece sleeve. There's also a solar filter, in the back of the case, to screw over the eyepiece... It's cracked and there's actually a dent melted into it on the inside!! I'll keep it for historical reasons. There's also a 9mm Meade MA and a 18mm Unitron Kellner thrown in for good measure, but I've not tried them.
The next day, I took the objective apart and inspected it. The lenses sit in the Steinheil configuration, as you would expect, given the manufacturer, with the flint forward, the crown at the rear. The lenses were VERY thick and had VERY strong curves for such a long focal length lens. This strongly indicates that this is not an ordinary achromat, but some form of semi-apo, as ordinary crown and flint wouldn't have required curves anywhere near this strong. I removed the spacers and measured one of them: 0.21mm. I then respaced the objective to 0.05mm with small spacers made from household tape. This should have a positive effect on the undercorrection, but whether it's enough to completely correct it, I can only say after doing a follow-up star test, and the weather is acting up today (which I guess is a good sign!)
More to come.
Clear skies!
Thomas, Denmark
