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Kickin' it old skool....

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#1 pogobbler

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Posted 18 November 2011 - 02:17 AM

Just got in from the frigid outdoors after 10-15 minutes observing with my brand new scope I just finished assembling this evening. It's definitely an old school refractor, a near-replica of one of Galileo's scopes I tossed together using a couple lenses from Surplus Shed. Though it made me long for even a cheap 6x30 finderscope, it was a very instructive, though brief, observing session.

Inspired by Galileo, himself, and a brief bit in the Hobby Q&A in an old S&T giving the specifics of the lenses in two of the old man's scopes, it consists of a plano convex objective, 30mm x 1000mm, stopped down to 16mm, and a double concave eyepiece lens of 22.83mm x -35.53mm, as close as I could find to the 37mm x 980mm objective and 16mm x -47.5mm eyepiece. This combination gives my version a magnification of about 28x versus Galileo's 21x.

Having a clear night and not wanting to wait to work out a more permanent and secure mounting, I taped it to the head of my photo tripod and took it out. After a couple attempts to first find and then focus on first Betelgeuse then the Moon through the bare tree branches, I ended up focusing on some lights in the distance to get a decent infinity focus. Then it was back to the Moon. Even through the tree branches, it was actually a pretty good view, once I managed to get it into the miniscule field of view. There was obvious distortion and chromatic aberration, but there were craters clearly visible on the terminator and, if anything, the view was a bit better than I might have expected, looking much like-- surprise, surprise-- the sketches Galileo made of the Moon.

I should take a moment now to interject about the "joys" of using a scope with a single negative lens for an eyepiece. The one thing anyone used to a modern scope would immediately notice is how different this makes the viewing experience. I'd heard before of the sort of view this would give, and it was as I'd heard, but it's not until you use a scope like that that you really understand how different it is. Just having this extremely small area in the center of... well, I can't really call it the center of the field of view, because you don't view anything in the blacked out area visible in the eyepiece around this small center where you can see an image. It makes you appreciate a simple Ramsden or Huygens eyepiece. It's odd, too, how you can move your eye around the eyepiece to see more of the potential field of view. The very limited field of view makes it very hard to find objects, as well, obviously, and it took a bit of searching and moving back and forth over approximately where the object should be to find it. That and the cold limited me to 4 objects tonight.

After the Moon, I went to look for Betelgeuse again and found it. Not much to see, being a star, but the image was reasonably sharp and didn't really show any obvious CA, which was, I'm sure, mostly due to the 16mm aperture not making the star bright enough to where CA would be obvious. 16mm ain't a lot of aperture, only a little over twice the maximum aperture of the human eye, when you think about it. Anyway, given that I was in the area, I had to go looking for the Orion Nebula. I did come across some stars in the area, but can't say I definitely found it. It was getting cold and my patience was wearing thin by then, so it was on to the last object for the evening. C'mon, we all know what this object had to be, right? Jupiter, of course. It didn't take too long to find and when I did, I really couldn't help but think back to that magical night over 400 years ago when man got his first glimpse of the larger worlds beyond our own through the eyes of Galileo. The CA on Jupiter was obvious, as you'd expect, and yet... the view did have some magic to it. It was clearly a disc and the moons were clearly visible, too. I can only imagine the excitement, shock and surprise that Galileo must have felt when he had his first view of Jupiter and its moons. To be the only person on Earth in on this little cosmic secret. What that must have been like.

That was it for me; I was cold enough and I'd have the scope other nights to use. It was an interesting night, though, and gives me some new respect for the man, himself, though I had no shortage of respect for Galileo before. It also puts my other scopes in perspective; each one-- each finderscope, even-- is way beyond the capabilites of this modest little scope, and yet none of them will ever make anywhere near the contribution to our knowledge of the universe we live in that the direct antecedent of this telescope did.

#2 Mr Onions

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Posted 18 November 2011 - 05:02 AM

What a briliant experiment and well worth the effort on your part to recreate that most famous of telescopes.
Great write up.

#3 mark8888

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Posted 18 November 2011 - 06:43 AM

It didn't take too long to find and when I did, I really couldn't help but think back to that magical night over 400 years ago when man got his first glimpse of the larger worlds beyond our own through the eyes of Galileo. The CA on Jupiter was obvious, as you'd expect, and yet... the view did have some magic to it. It was clearly a disc and the moons were clearly visible, too. I can only imagine the excitement, shock and surprise that Galileo must have felt when he had his first view of Jupiter and its moons. To be the only person on Earth in on this little cosmic secret. What that must have been like.


Indeed!! Thanks for the really interesting, well-written, and profound post. Heh not too often that one can call a post on an internet message board profound, but it applies here.

#4 t.r.

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Posted 18 November 2011 - 07:27 AM

This Observing Project may be for you...

http://www.astroleag...lileo_club.html

#5 Mr Onions

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Posted 18 November 2011 - 11:29 AM

So using a 16mm stop on my 3" and using a 32mm plossl would qualify for this as it yields a 18x magnification.
I think pogobbler may have started something here.

Perhaps a smaller stop should be used to allow for superior modern optics.

I imagine Galileo didn't have multi coatings or even a Feather touch focuser and i've never seen any images posted by him so he couldn't have been that good.

#6 Astrojensen

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Posted 18 November 2011 - 01:20 PM

This Observing Project may be for you...

http://www.astroleag...lileo_club.html



I really like project #1...!


Clear skies!
Thomas, Denmark

#7 Astrojensen

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Posted 18 November 2011 - 01:52 PM

So using a 16mm stop on my 3" and using a 32mm plossl would qualify for this as it yields a 18x magnification.
I think pogobbler may have started something here.

Perhaps a smaller stop should be used to allow for superior modern optics.


I will humbly direct your attention to this thread:

http://www.cloudynig...Number/4892407/

I imagine Galileo didn't have multi coatings or even a Feather touch focuser and i've never seen any images posted by him so he couldn't have been that good.


:grin:

What are you talking about? He even made a video of his solar observations and posted it on YouTube! The man's a genius! ;)

http://www.youtube.c...h?v=o9kZDMJfWEU


Clear skies!
Thomas, Denmark

#8 pogobbler

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Posted 18 November 2011 - 01:59 PM

I think my next step, after stregthening up and covering the tube with some good ol' duct tape, is to fashion something to mount it onto one of my other scopes so I can use goto to locate objects more easily and to track them once I find them. A more secure mounting might also allow me to more easily find the best focus point. I'm also going to get out today while it's light out and do some terrestrial observation to see how the scope measures up. At the very least, it'll be easier to find the image during the daytime.

I'm probably enjoying this little 16mm f/62.5 scope way too much.

#9 Astrojensen

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Posted 18 November 2011 - 02:36 PM

I'm probably enjoying this little 16mm f/62.5 scope way too much.



:grin: I know the feeling. I constantly tried to find new, difficult targets for the 22mm f/19.6 apochromat and had tons of fun in the process.


Clear skies!
Thomas, Denmark

#10 Mr Onions

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Posted 18 November 2011 - 03:16 PM

What's the cool down time for these 15mm scopes?

#11 Mr Onions

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Posted 18 November 2011 - 03:21 PM

What size finder would I need?

#12 Mr Onions

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Posted 18 November 2011 - 03:25 PM

Thomas thanks for those two links especially your experimentation one.
I once made two 14mm stops for my 7x42 binoculars with great daytime results.

#13 Astrojensen

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Posted 18 November 2011 - 03:31 PM

What's the cool down time for these 15mm scopes?


Depends on the aperture you stop it down from! ;)

A fun thing about these tiny apertures is their virtual immunity from bad seeing - it must be really horrible before they can't show a very crisp airy disk. Castor and Gamma Andromedae are simply stunning in my 22mm f/19.5 apochromat (72mm f/6 WO Megrez stopped to 22mm) at 43x. Vega is textbook perfect.


Clear skies!
Thomas, Denmark

#14 Mr Onions

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Posted 18 November 2011 - 03:34 PM

Oh yes but at 22mm you're using a big gun! ;)

#15 hfjacinto

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Posted 18 November 2011 - 03:50 PM

Thanks for posting this, everytime someone mentions what is a 60MM scope good for I always think Finder, but your post really made me question that comment.

Thanks for postings, it was a REALLY good post.

#16 Astrojensen

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Posted 18 November 2011 - 04:07 PM

everytime someone mentions what is a 60MM scope good for I always think Finder,


*turns humble mode off*

Please visit my CN gallery... http://www.cloudynig...r=55742&cat=500

*turns humble mode back on*


Clear skies!
Thomas, Denmark

#17 hfjacinto

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Posted 18 November 2011 - 04:34 PM

Thomas

That was a selective edit ;)

I know your posts and scopes are great.

#18 Mr Onions

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Posted 18 November 2011 - 05:01 PM

I'll tell you what makes me laugh {and mad at the same time} is when I read a review of a Tak or TV60 and the same old phrase comes up "Of course these are 1hour telescopes"
There are two things wrong with the people who make these statements.
1.. No real interest in astronomy.
2.. A severe lack of knowledge of the night sky.

How do these people observe,have a 1.5 second look at each object in the sky?

#19 Ed Holland

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Posted 18 November 2011 - 05:34 PM

I really need to dig out the lens I made one evening from a piece of perspex. It was a daft experiment to see what one could make with common household materials. I roughed it out using emery paper on the end of a piece of tubing about half the diameter of the workpiece. with some care, this ground a reasonable spherical surface of completely unspecified radius. After that I worked through finer grades of paper to about 2500 grit. At that point I polished out the surface with Brasso - I even tried casting a lap from plaster wall filler, and put the Brasso on kitchen towel on the lap. Technical stuff :). The result was a surprisingly nice looking lens. Focal length was approximately 1 arm's length, and I did try it on the moon, with an eyepiece (tricky as I had no tube to hold things steady or exclude stray light). I ought to dig it out again, set it up in some kind of assembly, take some pictures and post the results.

Ed

#20 PJ Anway

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Posted 18 November 2011 - 07:14 PM

Wow Thomas! I just love orange tractors!

#21 pogobbler

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Posted 19 November 2011 - 01:16 AM

For the full Galileo effect of these stopped down scopes, you should try to scare up a single negative lens to use as an eyepiece. Modern eyepieces make things too easy and are for wimps! hehe






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