Homemade/modified telescope
or improve your cheap "department store" achromatic refractor
and other tips and tricks that enhances your viewing

 
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Basic telescope improvements
Build telescope
Take the scope appart
Modify Dewcap
Improve focusser
Collimation
Chromatic aberration

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If you first want to learn about telescopes I would like to recommend my webpage here

Here we go...
You might have read elsewhere on warnings to avoid department store type of telescopes, mostly costs around 35$...60$. Not only are the optics small (small aperture and 0,96" eyepieces) and not good for showing you much. The diameter of the objective lens determines how much light can be gathered to form an image. It is usually expressed in millimeters. Often those telescopes as an objective lens of 50...60mm, and if your lucky 70mm.
The telescope usually comes on a very flimsy and shaky tripod that won't keep the telescope stable for aiming and viewing. Such telescopes have demoralized many would-be astronomers and caused them to run away from this exciting hobby.

Magnification
The rule used by amateur astronomers is 50X per inch of aperture or 2 X objective aperture in mm. This is for quality optics, as the optical quality goes down so the ability for the scope to give clear images at higher powers. So with this information we can conclude that the highest power a 60mm refractor from a department store can resolve is 125X.

Perhaps you own one of these scopes. My first advice is to discard it if possible (or use parts of it to build your own), and buy a quality telescope from a dedicated telescope store. But I presume, because you're reading this, that you are committed to making the best use of it. What can you do to make it more usable? Well, plenty.

1th, get better eyepieces
Ask any astronomer, and they will tell you that the eyepiece is half the telescope. The optics in the eyepiece focus the light from the lens or mirror into your eye. We'll see later how to improve those cheap eyepieces.
The eyepieces that are packed with department store scopes are, unfortunately, even lower quality than the scope itself. They are often mostly plastic, with optics that will give you fuzzy images. They have a very narrow field of view, so you get the feeling you're looking at the universe through a straw. And you have to place your eye very close to these eyepieces in order to see anything (called poor eye relief).

2nd, prevent reflections
The tube of the telescope was, luckely, painted matt black and had one single baffle (small ring aprox. halfway in the telescope tube that limmits the reflections seen from the focuser).
-- Solution one?: do nothing (but do spray it matt black if it has a shiny entirior).
-- Solution two: try to get your hands on flocking paper (or black velvet or black felt) and glue it on the inside. Believe me, it will make a big difference, surely when you use your telescope in city lights, or when viewing the moon... It will improve the contrast and loose some of those reflections that tends to get into the eypiece when viewing bright objects.
-- Solution three: use another baffle and flock it (see figure and explanation below)
The inside of the dewcap was shiny black plastic (same as the ouside): no good!
-- Solution one: sand the inside down with a coarse sandpaper and paint it flat matt black.
-- Solution two (best one): try to get your hands on flocking paper (or black velvet or black felt) and glue it on the inside. It will keep light from reflecting from the inside the dewcap and getting into the objective lens.
The eyepieces same thing or worse: shiny!
We need to remove all internal reflections inside the eyepieces themself and (if needed) clean the lenses as well (read about it here). None of those eyepieces I saw had any baffling or are even lacking flat black matt paint! Shiny black plastic isn't all that dark! Just keep it in the light, straight or under an angle, and you will clearly see the reflections. Any reflections are loss of light and can cause ghosting or glimmer. I even saw eyepieces where the chrome part of the eyepieces was chrome on the inside too!!! The Barlow lens that came with the scope was exactly the same way: the bottom was chrome and so was the inside! Also, the entire tube was shiny black plastic. My God, that was a looooong light tunnel to be seen through the barlow. Completely useless.

3th, stabilize the mount
Here are some simple techniques you can try to make the mount more stable.

-- Grease the chrome arm (right side of the scope and mount) that fits into the opening where the bolt fastened it.
-- Grease the rotating parts of the top
-- Tighten the wing nuts at the top of the tripod. This will make everything stiffer.
-- Lower the tripod legs. The lower the scope is, the less motion can occur.
-- Suspend a weight from the tripod head. Get a 1-liter box and fill it with sand and with a strong rope or other means hang it from the bottom of the mount head. The extra weight will prevent the mount from moving and dampen vibrations.
-- The aluminum legs can be opened at the top or bottom if you take some care. This will allow you to fill the aluminum legs with sand. This absorbs vibrations, though you will have a heavier mount.
-- Try vibration supression pads. These pads are round rubber discs you place between the ground and the bottom of the tripod legs. They absorb vibration in the tripod legs. Commercial pads cost about $50, but you can get results cheaply by using those kneeling protecting mats and cut three round parts out of it. Any thick rubber-like material will do.

4th, remove the slack and improve focuser
The telescope focuser had enormous slack. It wobbled up and down and left to right. To fix it I removed the focuser tube by removing the 2 screw beneeth focuser tube travel.
I stuck "electrician" tape inside the focus tube travel. Three parts of the length of the focus tube travel and separated evenly in the tube.
Test if the slack is gone, else stick another tape over it.
Put a little grease on top of the tape.
Remove the old sticky grease from the focuser mechanics and the tube.
Use a better grease, like for example: Finish Line Teflon-Fortified Dry 12oz. Lube

5th,

You can choose to keep the telescope as-is or rebuild it into a new one like displayed below,
but everything described here can be used to improve your "cheap" telescope without cutting it into pieces


My modified homemade scope
Born April 20th 2008
Name: Rule
Scope I

Now, let us begin to build...
The telescope I had (got it for 10$ from a fleamarket) was a BlueSky D=60mm/F=700mm telescope. I will base my homemade telescope from that type, although you will be able to adjust the modifications as we get along for your type of "cheap" telescope.
First decide if you like to "destroy" your cheap department-store telescope and build from it your own
Keplerian telescope. Or do you "just" want to improve the scope. If you decide to keep the telescope as-is, then I would like to recommend to above tips and tricks (and skip the next chapter ;-)...No no! There are a lot of tips and tricks you can use during the process as how I build and modified the existing telescope and give it a new life...
Well, a new life as a Keplerian based telescope that is. What is a Keplerian telescope? Read all about it
here please, but it all comes down to a slightly improved Galilean telescope. The reason for my decision to make my own telescope from a cheap department-store scope is plural:

Ok, we decided to take the telescope appart

RuleScope I: Keplerian Telescope Design (using one lens as objective):


So, what can I expect to see?
With all these improvements you will get a useable scope, although reducing the size of the scope like I did does not make it a better scope, on the contrary. But you know the reasons (see text).
The companies who market department-store scopes promise you every wonder the Universe has to offer. They claim you will view images in the eyepiece that look like
photos from the Hubble Space Telescope. The reality is somewhat different, no telescope, even very large ones, will give you a view that matches what you see in photos. These photos are taken with cameras set up for hours-long exposures, and use films and CCD detectors much more sensitive than the eye.
However, we do have plenty enough to see through our "cheap" telescope...the Moon is a fantastic sight in nearly any telescope!
You can see Mercury, Venus, Mars, Jupiter, and Saturn easily through the telescope.
Also some double stars (appear very close to one another in the sky) of which the color contrasts can be sometimes breathtaking. The most famous double star is Alberio. A small refractor like a department-store scope actually works well for viewing double stars.
Open star clusters. You might try observing the Orion Nebula(M42), Andromeda(M31), M36, M37, Great Hercules Cluster(M13)...
Only a few diffuse nebulas are observable in 60mm refractors; half of them are in Orion. Among the "known ones" (M42, M8, M17...) we find more discrete nebulas surrounding stars (NGC 2023, NGC 1999....)

Look for some good software (starcharts) that allow you to find all of this and much much more with your PC. My favourite is
Stellarium By Fabien Chereau. It's easy to use and shows you the heavons like you are standing there yourself.
More software can be found
here

the homemade scope (rulescope I)
or online tools

Although only a few galaxies are bright enough to be visible through light pollution, two of those exceptions lie near the Big Dipper. The first, M81 (Map 2), is found northwest of the Dipper's bowl, while the second, M51 (Map 7), is just south of Alkaid, the star at the end of its handle. Although a low-power eyepiece is best for zeroing in on each location, a medium magnification, around 80x to 100x, will probably deliver the best views.

Finally, follow the arc of the Dipper's handle to Arcturus, the bright orange star that dominates the constellation Boötes. Northwest of Arcturus, across the border in the faint constellation of Canes Venatici lies the globular cluster M3 (Map 7). M3 looks like a tiny ball of cotton near a 6th-magnitude field star through small telescopes. Six-inch and larger instruments may be able to resolve a few individual points of light, even from inside a city.

What kind of eyepieces to use

Look for a low power eyepiece to view nebula, open star clusters, and galaxies through. This should be in the 35X to 50X range. The next one you will want is an eyepiece that is in the 75X to 100X range. This would be to look at details in globular clusters, small parts of nebula. Then eyepieces that will give you 50X par inch aperture. This is the high power eyepiece used for planetary viewing when the conditions are correct.

Clear skies!


Astrophotography, info about telescopes, tips & tricks, homemade scopes and lenses etc.
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Astro photography, info about telescopes, tips & tricks, homemade scopes and lenses, how to collimate, online astronomical tools etc.