PVC Telescope: A Modular Optics Lab in a Tube!

PVC Telescope: A Modular Optics Lab in a Tube!

Reflector telescopes use mirrors, refractors use lenses. To make a reflector you precision grind a mirror, for a refractor you need to play with at least two lenses-more of you want color correcting and distortion minimizing qualities.

It's quite simple really. Light gets focused between two lenses: the main objective lens at the end of the tube that gets pointed into the sky and the eyepiece. However different colors of light are different wavelengths. Different wavelengths focus at different places. 

This makes your telescope into a prism: colorfully blurry!

When a nice focused green wavelengths falls perfectly on the eyepiece that means the red and blue waves are a little too in front of and too past the eyepiece to be on focus. This problem is called chromatic abberation and some really expensive refractor telescopes have it. It's something that you can: get used to; hate and buy a reflector (mirror) telescope; or pay even more money to correct. Adding additional lenses can bring the red and blue to the same focus point, this is called an achromatic len(s).

Now, to be clear "blurry" isn't exactly accurate as a description of chromatic abberation. The views is very crisp, but tripled slightly: you'd see the moon with a red moon slightly misaligned with a blue moon slightly misaligned with a yellow moon. All very crisp but distracting.

Many telescopes that are refractors (lenses not mirrors) show this tripled misalignment just along the edges of bright objects as color fringes and flares. Even really, really, really expensive refractors can have a little color fringing from chromatic abberation.

If you want to see chromatic abberation on your own just aim a pair of binoculars at an electrical power line hanging from a telephone pole. Of you hey just the line in focus with a bright, clear sky behind it you'll notice yellow and purple highlights along the edges of the line. Shiny highlights on the line may also have weird color aberrations. The better the optics, the less color fringing.

The glass of the lenses absorbs and passes light waves through at different rates. Reflector telescopes (mirror) bounce light off a mirror-the mirror reflects the light, but doesn't absorbs it. The light bounces and isn't passing through it so reflector telescopes don't have problems with chromatic abberation. 

I wanted to build a refractor of my own design that allowed me to swap different lenses in and out to experiment with correcting various flaws including chromatic abberation. A modular optics laboratory in a tube! I decided to use PVC and headrd to Home Depot with calipers, pad, pencil and a tape measure.

But first I needed a nice lens. I bought a cheap one for $7 on Amazon. It was an Ajax Scientific Polished Glass Bi-Convex Spherical Lens, 100mm Diameter 500mm Focal Length. Nice lens!

1x 3" PVC flat top cap (not the domed/rounded bubble top)

3x 3" PVC 3x3 repair couplings (that are smooth inside, not with an internal ridge)

1x 3" PVC 3"x2 foot foam core pipe

1x 4" PVC 4"x2 foot foam core pipe

A big objective lens

Wood saw to shorten both pipes (hack saws don't cut straight with PVC easily)

Telescope eyepiece or bi-convex lens or eyepiece from binoculars

Black spray paint

A big ring cutter drill bit to cut a hole for eyepiece or lens (.965", or 1.25", or 2" or whatever your focuser needs if you're using a focuser instead of just plunking an eyepiece into the hole in the end cap).

At Home Depot I bought a 4" PVC white pipe and painted the inside black to reduce glare and increase contrast. One insert (repair coupling) with hole in the center pushed in followed by this lens followed by another insert. These trap the lens in the tube.

Another insert with hole at other end of pipe allows a 3" PVC pipe to slide in and out to adjust focus. At the end of the 3" pipe pit a 3" end cap with a hole in it to hold an eyepiece of to fit a telescope rack focuser.

Extend the tubes for close focus like neighbor's house, push them in (shorten) for father focus like the sky, moon and stars. All with so much chromatic abberation they looked like a psychodelic Andy Warhol print! My first view was of a street light a couple blocks away. The abberation was so bad it looked like a bunch of multicolored poles barely touching, not merely "misaligned" slightly. 

Medium distance focus is about 20" from lens to eyepiece (focal length is 500mm f/5). So you'll have to cut the tubes to short lengths. This shows the effects of differing focal lengths on telescope designs: magnification (greater or less zoom with the same eyepiece), brightness (f-stop/speed) and field of view (wide angle).

The magnification (zoom-in) of a telescope equals its focal length divided by the focal length of whatever eyepiece you have in it. Every time you double the magnification you loselose 50% of the sharpness of focus and 25% of the brightness! 

If you're looking at something bright like a planet or the moon that's fine-but for faint nebulae and galaxies it might make you unable to even find your target in the sky. 

Useful magnification is twice the diameter of the objective (lens or mirror) in millimeters. 50mm lens x 2 = 100x top magnification.

1000mm focal length ÷ 100x = 10mm eyepiece needed.

Remember though: my design slides in and out so I can change my focal length slightly, but not my objective diameter (unless I swap out the front lens). I can change my magnification by changing eyepieces.

My telescope has a 100mm diameter objective lens. Twice 100mm equals 200x maximum magnification. 

Its 500mm focal length ÷ 200x desired magnification = 2.5mm eyepiece needed. Those are expensive, but I've got a wonderful 3mm eyepiece that gets me close enough. However, in my larger telescope that same eyepiece will give me 400x magnification! Everything effects everything else in the optical chain.

Too close...zoom out or claws out!

Once you've played with focal length and eyepieces you can add a concave lens in between to try and correct for chromatic aberration, etc. Alternatively you can use a double or bi-concave lens instead of an eyepiece. This is really a telescope laboratory in a conveniently simple modular package!

So less than ten bucks for the lens and about thirty-five for the pvc if you don't have it around the house compared to big bucks for a 4" refractor astrograph telescope (plus you'll have to scrounge up a focuser and maybe some other lenses to experiment with correction).

It's quite a large and heavy beast! 

Here it is mounted on top of a rather long, metal, 1970s Tasco. PVC is incredibly heavy, but if you take care and balance it well it moves easily. Even on a terrible mount. Tasco had the worst mounts in the business, but an even bigger tragedy were their eyepieces. They were the small 0.965" size and atrocious! 

I bought an adapter for $9 on Amazon that is a 90° elbow: one end fits into the 0.965" opening in the telescope; the other side has a 1.25" hole that accepts professional 1.25" eyepieces (but not 2" Diameter ones). If you have an old Tasco buy the adapter and some cheap 1.25" eyepieces and you'll be blown away! A 20mm, 12mm and 9mm are a fine set for most Tascos. The mount will still be criminally terrible: jerky, wobbly, prone to falling, etc.

I also took some old slide and film projector lenses and converted them to use as eyepieces. They have varying outside diameters so some had to be spun up on a metal lathe and smallerized, others were too narrow and needed tubing or duct tape wrapped around them for a snug fit.

You can find old lenses like this cheap or free all over the place. Even if you're using a store bought telescope it's neat to increase your eyepiece collection for free and have fun doing it!

At dead center of the photo above you can see the 90° adapter on the Tasco and upper right is the eyepiece simply stuck into the end of my PVC telescope.

Woah, the colors! Chromatic-Cat says meow!

TAKE THAT COPERNICUS! with a COMET LOVEJOY POSTSCRIPT.

TAKE THAT COPERNICUS! with a COMET LOVEJOY POSTSCRIPT.

The Moon has left the sky;

Lost is the Pleiads’ light;

It is midnight

And time slips by;

But on my couch alone I lie.

-Sappho (circa 580 B.C.)

Copernicus never saw Mercury? What follows are some of my quick photos of Mercury which serve to prove that I'm a better astronomer than Copernicus. 

Well...not exactly: you see, while Copernicus never bothered to write explicitly  in his journals that he did indeed see Mercury (I suppose he was much more modest than me ), he almost certainly did see Mercury! Further, he did extremely complex mathematical calculations which involved all he known planets--including the path of Mercury!

He did write in one of his works that were he was there was lots of fog in the mornings and evenings and lots of tall trees, etc. that made viewing Mercury difficult in Poland. "Difficult" as in annoying or hard, but not impossible. Remember, whenever Copernicus was trying to view Mercury (or any other star/planet) it wasn't for pleasure-he needed precise measurements so he could work on mathematical theories of planetary motion such as slight trepidations (oscillations) caused by gravitational forces and their orbits, etc. 

So, what did Copernicus do while in the foggy forests of his native Poland? He just wrote letters to his friends in other places who sent him measurements of their observations of Mercury. He then went inside his house and did maths. Very groundbreaking, difficult, awesome maths.

Even with a smartphone, calendar app and plenty of email alerts to notify me exactly when and where to look for Mercury it took me two years of trying! Mercury hugs our sun. Most of the year it's hidden in the blinding sunlight of day. However, a four to five times a year it strays just barely away from our sun so that you can aim a telescope at it (Mercury, not the sun) and watch it. You get a week to get it early in the morning and then wait months later to see it at sunset (meaning, literally like a few minutes after sunset).

I'm not a morning person, I sleep until 10am most days. So the morning appearances were ruled out. I had to wait for evening sunset Mercury appearances. The first few times I missed even seeing it as the 'bright star' everyone else (seemingly) on Earth was marveling at. I was at work (in a library) and grabbed my HUGE Konus 20x80 binoculars and ran out the front door:

  

So what did I see? Well, here's the thing: it was the same night that the International Space Station was flying overhead so everyone in the parking lot (an annoying large amount of people) were asking me about the ISS. I got so flustered (I'm shy) that I forgot I was using binoculars (which show a normal right-side-up image) and not a regular telescope (which shows an upside-down image). I kept going from Saturn up to Venus instead of Venus down to Saturn and a little further down to Mercury. It would have been so easy to see had I just swiveled down instead of up.

Another time I had everything lined up and just as the sky started to dim just a tad as our sun dipped below the horizon: boom, I noticed a HUGE tree limb in the way. I big tree, so I jumped in my pickup truck and drove about a mile away and STILL was blocked by other trees. Normally I would have been irritated but I just laughed it off, "now I know what Copernicus felt like". 

Finally, over a year later, I was able to see Mercury. I watched it for over half an hour! I used my big binoculars and it looked like a bloated, fat dot the color of pinky-orange Neapolitan ice cream:

There it is in the photo above. Dead center, the orangey-pink dot poking through the clouds. I took this picture by sticking my cellphone up to one of the eyepieces on my binoculars (which were on a tripod at the time).

After seeing it in my telescope I moved to my 8" Zhumell reflector telescope. What I saw was pretty amazing: it looked like the old Apple Computer logo: a three-color-striped blob with a bite taken out of it! Mercury goes through phases like our Moon and the planet Venus. Full round circle, mushed oval, crescent horn sliver, etc. At first I thought my telescope was broken, but no: being so low in the horizon made its light refract through the atmosphere (and smog) and get all distorted color-wise, and it wasn't in a full-round phase at the time.

I was so happy after my two year hunt that I forgot to take photos.

Here's one I took recently--it's a casual shot. Why? Mercury was right next to Venus so it was extremely easy to view. I grabbed a better eyepiece, put it in the telescope and just as I was about to look I noticed a wall of clouds coming: so I just peacefully observed instead of rushing to take a photo in the few seconds I had. Here's the crumby pic I did manage when Mercury was in a fuller phase and higher up in the sky:

Due to the bloat of Mercury, I'm thinking the above picture was taken with a 3mm or 9mm eyepiece in my 8" telescope. Anyway, that was at 6:30pm January 12, 2015. It was 19 degrees outside! So I went back in due to the cold and clouds. I was happy. 

Then at 9:30pm I ventured back out and was treated to The Comet Lovejoy just below the Pleiades! Each night during about a week-and-a-half of observations Comet Lovejoy moved closer and closer to the Pleiades. It looked like a hazy grey blob, possibly on one of the nights I may have sensed some slight green color-but no tail. Too much light pollution in Metro Detroit.

Anyway, that's why I started this post with the Sapho poem mentioning the Pleiades: it paved the way for Comet Lovejoy after viewing Mercury earlier in the night, along with Jupiter, Jupiter's four Galilean Moons: Io, Europa, Ganymede and Callisto; our own Moon, Venus and even the Orion Nebula (which was so bright it was visible with the naked eye as a blue smear). 

Not a bad night. Not a bad night at all...

I'm Opposed to Saturn...We All Are at the Moment

I'm Opposed to Saturn...We All Are at the Moment

At the end of May 2015 Saturn is at opposition which gives us the best and brightest view of it all year.

Here's a lousy afocal astrovideo I took of Saturn through my 9mm eyepiece and 8" Zhumell reflector telescope on May 23, 2015. The actual view was much better than the cheap cellphone could convey.

A cheap telescope will show you at least the ring, which with even the cheapest binoculars on a tripod will look like Mickey Mouse ears. Early astronomers thought it might be a moon on each side. I thought, "how could a ring look like two moons?" but I went out with cheap binoculars and lo and behold! It did look like a big circle with two smaller circular 'ears'.

A small 40mm tasco type should still let you see something. Jupiter is even easier because its bigger and almost straight west to the right of the moon.

Here's another video with a 2x barlow attached to the 9mm eyepiece, making it a 4.5mm with higher magnification. 

More zoomed in but darker and less crisp focus. Such is the physics of optics and light. 

A great free phone app for astronomy is SkEye...which you'll need because the planets move around quite a bit (planet is Greek for "wanderer").

I also feel elated after getting some cosmic photons in my eyeballs. 

"The universe as we know it is a joint product of the observer and the observed."

-Teilhard de Chardin

Good night and clear skies to you!

Afocal Astrophotography (is really simple)!

Afocal Astrophotography (is really simple)!

What follows is an afocal astrophotograph I took of Saturn. Afocal astrophotograph is a fancy term for just sticking a camera up to where you normally put your eye to look through the telescope. Afocal: just held up to the regular eyepiece of a telescope, or microscope or binoculars. Astrophotography: when you aim at something in the sky that isn’t a bird or plane. It’s that simple! 



Here is the resulting photography through my 8” Zhumell reflector (mirror, not lens) Dobsonian (mounted on a lazy-susan swivel) telescope. I was using a high magnification eyepiece. I think it was my 3mm Zhumell Planetary eyepiece. That’s why it’s dark and kind of fuzzy. The smaller the mm number in a telescope eyepiece: the higher the magnification (zoom in) but the less light and less sharpness you’ll get:

And that photo above (on a 19" screen) is about as small, but crisp as it was looking with my eyeball through the telescope too! Depending where Saturn is in relationship to earth the rings can be edge-on and almost invisible or more titled so we can see them better. Also, Saturn and all the other planets change in apparent size depending on time of year and how close/far they are from planet Earth.

Later, I took around 10 seconds of jittery, crappy hand-held video and then registered (lined up) and stacked (piled on top of each other) the resulting video frames using RegiStax. RegiStax is a FREE awesome astrophotography program. It took me about 4 hours to download and install it (mostly just the downloading took a crazy amount of time). What’s cool is that when I went back to look at the raw video it was so shaky that Saturn was only in the viewfinder for about 3 seconds. So, 3 seconds of blurry Saturn stacked up and throwing away 7 seconds of darkness.

Directly above this is a video taken through one of my telescopes. The telescope is locked in position. The sideways movement of Saturn is due to the spinning of the Earth. The up-and-down bumps are from the slight wind moving the whole apparatus.

After taking the 10 seconds of video, I imported it and then played around in RegiStax. Once I got my preferred settings in RegiStax I set it to process, that took about 40 minutes. The result was it transformed crumby, shaky low-res video from a 1990s Fuji Finepix 4700 digital camera into this blast of awesomeness:

Notice how you can see at the bottom right where the sphere of the planet actually casts a shadow on the lower part of the ring as it passes behind the planet! You can also barely make out differences in the rings (darker colors).

RegiStax is a FREE (but long) download available here: http://www.astronomie.be/registax/ You’ll want to install it on a desktop because it is HUGE and powerful program. Think PhotoShop for 3-dimensions.

Harsher processing (different settings) with RegiStax of the same 316 frames of video stacked on top of each other:

Because I was sick of holding my old camera (a 1990s Fuji FinePix 4700 'Silver Brick' that I had since college) up to the eyepiece I made a cheesy but free afocal astrophotography bracket out of scraps:

Here is this crazy apparatus mounted on my old tiny telescope. The red ring between the camera and eyepiece is a reel from some white Teflon plumber's tape. It was the perfect size for my old telescope and it's lousy little .9" eyepieces (see below about eyepiece sizes).

It's important to note the different physical sizes of telescope eyepieces and how that obviously makes mounting a camera a real pain! If you want to change magnification you have to change the eyepiece.

The little eyepiece in my hand to the left is what you're probably used to in toy store telescopes and microscopes. It's a .9" Japanese size eyepiece. Tiny, not so great usually. Next to it is some 1.25" format eyepieces. Now we're talking! Better telescopes can accept 2" eyepieces and 1.25" eyepieces with an adapter. Professional quality eyepieces are 1.25" and 2". 

Here is my HUGE Zhumell Z8 telescope with a 2" format eyepiece mounted in it (to the right and higher than the Pepsi can). It has a frosted white plastic dust cover on it and yes it IS almost as big as the Pepsi can!! It's actually heavier than an unopened can of soda (in Michigan we call soda "pop").

You didn't believe me when I told you my telescope eyepieces are as big as a pop can did ya?

If you have a Dobsonian-mounted telescope (on a spinning lazy susan style mount) a great user upgrade modification is what I did to my Zhumell Z8 shown here. Mount in on a milkcrate and cut holes on either side of the mount. These mods accomplish a few things: with the addition of a rubber bumper on the bottom of the tube (so it doesn't bang into the mounting as hard) I can now push the telescope tube upright, then bear hug the whole telescope and grab it by the two new huge holes. I push my chest into the tube which mashes it tightly against the mount (and rubber bumper) Yes, I carry my entire telescope out the door in one piece instead of multiple trips! No more carrying the base, then the tube and trying to assemble them in the darkness. The huge pieces I cut out where also pretty heavy, meaning I have less weight to deal with all around, which is nice. The milkcrate just makes it higher so I don't have to lean down and get a backache or migraine while using the scope. 

The other piece of advice that really, really helps when using this type of reflector telescope has to do with colimation (lining up the primary and secondary mirrors with eachother, and then lining up the eyepiece--all using a laser). Whenever you make adjustments to the secondary mirror mount screws or the thumbscrews of the primary mirror (but not the locking screws) always try to tighten them to get to where you want things aligned. At first I would loosen one side and tighten another. Once I shifted to always tightening, after a few nights of use and colimation things were so tight that they telescope didn't need to be colimated at all! Things just tended to stay put...and that's after the bear hug and walking down stairs and out a door and down stairs of a stone paver patio!  

So, do you have an old Tasco telescope? It's a great telescope with two deadly flaws (that you can fix). For a few dollars you can order a new eyepiece mechanism that will allow you to put 1.25" eyepieces in your telescope! I did this and was blown away by the quality increase when using my good eyepieces in what I thought was a bad telescope. Tasco telescopes are optically fine, they're eyepieces are totally crumby though. 

The second deadly flaw is their criminally negligent telescope mounts (tripods). They're just awful and probably were the main reason that 99% of their telescopes end up "used only a few times, asking $10 for it".  Find a way to stabilize the mount and you'll love the telescope. This may entail wood and metal working, or haunting charity resale shops (Salvation Army, Disabled American Vets) for a deal on a better mount. For $5 I found a fancy equatorial telescope mount, twenty pounds of counterweights and best part was--it came with my old telescope tube! Yep, the grey telescope I took many cool photos with was only $5 for the scope, great mount with weights and a pile of mediocre eyepieces and other stuff! 

I highly recommend the DAV Thrift Store at 8050 N Middlebelt Rd, Westland, MI 48185! The workers are also SUPER NICE!!! They work for charity to help disabled veterans. Probably my favorite place on Earth besides Costco and my own house.

I also like my binoculars big, and mounted on tripods. Above are a pair of great Konus binos I scored cheap off of Amazon brand new.


In later posts I’ll detail my: spectrometers (a few homemade and a store-bought one); infrared experiments and my favorite hobby of all: staring at the sun! Until then just know this: no matter how cheap a telescope or microscope or binoculars you have you can usually stick your camera (even a cellphone camera) up to the eyepiece and take cool pictures afocally. 



For the desktop or laptop Stellarium is a great astronomy tool: stars, planets, space junk and satellites visible from Earth are all easy to find using this software. They charge for the mobile app but desktop version is free and way more powerful. I have it on my phone but always seem to use the free app SkEye, which lets me scroll around and even attach my phone to my telescope and it tells me which way to swing the scope to view my target object. There is an align function that's easy: point telescope at a known object, scroll on screen and tap the object. Do that a couple times and your phone and telescope act as one! 


Remember, telescopes are just light buckets: the bigger the bucket the more light you grab. The eyepieces do the focusing and magnifying (zooming in). In my big 8" telescope looking at the moon is actually a little too bright and painful. I have to squint. Good thing we don't have super-sensitive cat's eyes.

The moon is so bright that most astronomers don't bother to use their telescopes when it's visible because, much like the sun, it drowns out the stars in the sky. Even the ancients were both awed and annoyed by the moon:

The stars about the lovely moon fade back and vanish very soon, when round and full her silver face swims into sight and lights all space.

Sappho

Meow!