More homemade parts for your telescope
and modifications






Modify or build a finder
Homemade collimating eyepiece
Oil-spaced achromat
Solar filter cap
Homemade tube extension/anti-reflection cap


Modify/build a Finder

I had a finder to "molest" laying around. Actually it was a cheap finder of my son's cheap department-store telescope. Because I had no use for the finder on my homemade telescope and needed an optical finder with a bit of magnification. My Skywatcher-Pro 130mm Newtonian telescope has a red-dot finder, which is excellent, but to be able to use my Skywatcher telescope for dusk-/dawn-/day time observation and to better pin point the stars (my red-dot finder has no magnification) a secondary finder was needed. So I decided to make my own finder with an achromatic lens. The cheap finder I had wasn't suitable because of its plastic lenses with a huge aperture stop. It had a 20mm aperture, but only 1 cm effective aperture because of the field-stop behind it...
no need to explain any further!


Improve a air-spaced achromat with and oil-spaced doublet achromatic lens


Collimating cap

If you do not know what collimation is then please read this first. In short: Collimating a telescope is lining up its optical components (lenses, mirrors, prisms, eyepieces) in their proper positions.
If you have a cheshire collimation piece then you can skip this...but this is a cheap alternative...not as good, but still...
"collimating cap":
- if your scope has 1,25" eyepieces: out of a plastic 35mm film canister (black with gray lid). Drill or punch a small pinhole (+/- 4mm) in the exact center of the lid and cut off the bottom of the canister. Replace the lid.
- if your scope has 0,96" eyepieces: use an protection lid that came with your scope (like one of your diagonal or the one used to protect the
eyepiece holder). This is of transparent material. Drill or punch a small pinhole (+/- 3mm) in the exact center of the lid. Draw a diagonal with a thin black permanent marker.

This device will keep your eye centered of the focuser tube.

Homemade Solar filter cap

Please observe the following safety precautions with EVERY solar observation:
1. Prior to each and every solar observation session, check the filters fit and - if necessary - tape it to prevent slipping. Never use the filter at the eyepiece, only attach it onto the front of the objective, in front of the Schmidt-plate (SC-owners) or in front of the tube of a Newtonian-telescope. Otherwise it can become dangerously hot inside your instrument and inside your eyes.
2.If you use a binocular, protect both objectives with a filter. Also make sure, that the viewfinder of your telescope is properly covered, either with foil or with the original dust cover. Unprotected views through your finderscope would have the same catastrophic consequences for your eyes as a look through the main telescope itself!
3. A filter made of foil is relatively resistant to breackage in comparison to a glas filter. However, care should be taken with sharp pointed objects.
4. Emphasize the importance of caution to those observing with you, especially children. Intentionally removing or damaging the filter can endanger their eyesight. This is no place for jokes. Never leave the telescope outside unattended during the daytime!

To aim the telescope, do not use your finder! Instead, point the telescope until it casts the smallest shadow possible behind it.

What do we need?

It is all pretty strait forward as you can see from the images. Just be sure it does not come of your telescope easily! It takes only a moment to damage your eyes.
The film must be mounted flat and free of any tension - Only this will provide first class Solar images. The quality Baader Astrosolar safety film is very high.
Try to prevent as much as possible any wrinkles or strain on the film as this could lead to deterioriation of optical quality.

don't let the little wrinkles fool you, it seems worse then it is and it stretches perfectly flat once placed over my telescope.

Cut a perfect circle of the size of your telescope aperture out of the lid.
Sand the entire cilinder (bucket or whatever) inside and out with fine sandpaper. Paint the outside with white paint (prevents from the cilinder heating up from the Sun).
Measure the size of Baader solar filter you need according to the aperture, but make it a bit larger. Add glue all around the inside of the opening and press the film on it. Slide the film evenly over it so you don't have any large wrinkles. When satisfied let it settle. Just to be 100% sure it does not come off I have placed some thin transparent sticky tape in a hexa layout. Sand the top of the tape.

Finally, paint the inside flat black as you can see above.

I bought a second round cookie container (bucket) to use the lid as protection cover.

Please observe the above safety precautions with EVERY solar observation!

Homemade tube extension Dew/Anti-reflection cap

All finished. Looks pretty cool doesn't it...

If you live in a light polluted area like I am a tube extension to the front of the scope does really help alot. It keeps out unwanted stray light hence improving contrast.
What do we need?

This is the cookie bucket with the bottom cut off. As I wanted to fit this particular type of container, I needed to fit it on the inside of my Skywatcher scope. Actually I've found that this works very well in any case. It's a matter of slidng it in the scope (works only if you have Newtonian telescope of course).
Anyway, to make it fit my Newtonian I placed double sided sticky tape as you can see above...

Here is where my painters cardboard comes into action... I've cutted a strip of this pretty sturdy material of 6 cm and ...well the diameter length you need ;-)
Sanding the outside and the inside of the container will not help only to hold the paint, but also the glue for the black felt (flocking paper) and holds the double sided tape much better.

I used some black felt and glue spray to fix the felt inside. The black felt, or even better; flockingpaper, really does a better job preventing stray light or reflections then flat back paint does!

Finally finished... As you can see I've painted the outside blue and the lid. The lid is ideal to cover up the dew cap, hence your telescope when using it or storing this homemade extension cap.

The homemade extension cap on my Skywatcher Explorer.
It's a pitty I didn't had the exact type of paint of my telescope for the cap at the time...


Astrophotography, info about telescopes, tips & tricks, homemade scopes and lenses etc.

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