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First light Steinheil 110/1650mm

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#1 Astrojensen

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Posted 16 April 2024 - 11:02 AM

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". cool.gif  

 

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.

 

gallery_55742_4772_4977226.jpg

 

gallery_55742_4772_635710.jpg

 

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:

 

gallery_55742_4772_230960.jpg

 

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.  

 

gallery_55742_4772_1089090.jpg

gallery_55742_4772_2994428.jpg

 

gallery_55742_4772_3567130.jpg

 

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


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#2 Weisswurst Josef

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Posted 16 April 2024 - 03:59 PM

Congratulations Thomas!

 

Sounds very good and hopefull.

 

Please provide us with daylight pictures of details from this wonderfull refractor.

Of course you will do and of course have planed this.

 

Clear nights

Andreas


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#3 Sasa

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Posted 17 April 2024 - 04:58 PM

This is great telescope, congratulations. Wilhelm Tempel made many interesting discoveries through similarly sized one (he had 108mm refractor from Steinheil). My old Zeiss AS110/1650 definitely needed after about 90 years respacing to get back to top performance. I hope you can fix yours.
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#4 Terra Nova

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Posted 17 April 2024 - 08:53 PM

That's a wonderful acquisition Thomas, I'm sure you'll make the most of it. It couldn't have found a better home.


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#5 deSitter

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Posted 18 April 2024 - 09:47 AM

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". cool.gif  

 

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.

 

gallery_55742_4772_4977226.jpg

 

gallery_55742_4772_635710.jpg

 

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:

 

gallery_55742_4772_230960.jpg

 

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.  

 

gallery_55742_4772_1089090.jpg

gallery_55742_4772_2994428.jpg

 

gallery_55742_4772_3567130.jpg

 

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

1/2 wave is a lot - in a star test you'd have the classic perfect target on the outside and ringless mush on the inside of focus. Trying to focus would be "trying".

 

-drl



#6 Astrojensen

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Posted 18 April 2024 - 02:25 PM

1/2 wave is a lot - in a star test you'd have the classic perfect target on the outside and ringless mush on the inside of focus. Trying to focus would be "trying".

 

-drl

That is exactly what it was like. I've respaced the objective, but haven't had clear skies since. I did have a brief moment with clear skies in the daytime, but the seeing was very poor, so solar views were inconclusive. 

 

 

Clear skies!

Thomas, Denmark



#7 Astrojensen

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Posted 19 April 2024 - 02:10 AM

Ha! Respacing worked! The spherical undercorrection is now greatly less than before, although it's still present. The scope is now at least usable, though by no means perfect. At best focus, there's still  halo of unfocused light surrounding bright stars. Cooling is important, as letting the scope cool down improves the view a lot. 

 

Had an hour of semi-clear skies last night, amid drifting clouds, and the lunar views are now quite enjoyable at 165x (10mm Hyperion). 

 

A star test revealed some slight miscollimation, so there's something there to work on. Also did a Ronchi test, which looked very puzzling, to say the least. The lines weren't straight, but slightly wavy, so there seems to be several mild zones that doesn't show up in the star test. Unfortunately, conditions weren't good enough to allow a proper examination of the objective, as I was constantly interrupted by clouds. 

 

 

Clear skies!

Thomas, Denmark


Edited by Astrojensen, 19 April 2024 - 02:14 AM.

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#8 mikerepp

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Posted 19 April 2024 - 05:28 AM

What a wonderful scope.  It has character, I really like it!  Glad you solved the under-correction.   I'm sure it will give you some wonderful views.



#9 Astrojensen

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Posted 19 April 2024 - 06:16 AM

I wouldn't say I've solved it. It's less than before, but still an issue. 

 

 

Clear skies!

Thomas, Denmark



#10 davidc135

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Posted 19 April 2024 - 10:07 AM

Any

 

I wouldn't say I've solved it. It's less than before, but still an issue. 

 

 

Clear skies!

Thomas, Denmark

Any Ronchi or knife edge images postable?

If there is no more spacing adjustment available, would you consider retouching the figure?

 

David



#11 Astrojensen

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Posted 19 April 2024 - 11:07 AM

Any

 

Any Ronchi or knife edge images postable?

If there is no more spacing adjustment available, would you consider retouching the figure?

 

David

I shall see if I can grab some Ronchi images, if it ever clears again. 

 

I have considered oiling the objective, as that is essentially the same as reducing the airspace "below zero". I'm thinking about using the kind of non-hardening gel that they use in fiber optics. It has very high viscosity, so shouldn't seep out over time and be much less messy to work with than oil. It's worth a try, I guess. R2 and R3 are probably not identical, but they're close. The objective can be assembled without spacers, without the two elements touching each other in the middle. 

 

 

Clear skies!

Thomas, Denmark


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#12 davidc135

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Posted 19 April 2024 - 03:45 PM

I shall see if I can grab some Ronchi images, if it ever clears again. 

 

I have considered oiling the objective, as that is essentially the same as reducing the airspace "below zero". I'm thinking about using the kind of non-hardening gel that they use in fiber optics. It has very high viscosity, so shouldn't seep out over time and be much less messy to work with than oil. It's worth a try, I guess. R2 and R3 are probably not identical, but they're close. The objective can be assembled without spacers, without the two elements touching each other in the middle. 

 

 

Clear skies!

Thomas, Denmark

I don't think it's very likely to succeed but interesting to see.  David


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#13 clamchip

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Posted 19 April 2024 - 06:13 PM

There may something in here that might help:

https://www.cloudyni...f133-refractor/

 

Robert


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