Accessories

One of the joys of this hobby for me is the wealth of interesting bits of equipment required to push the boundaries further and to experiment with new techniques. Of course you can buy some excellent devices to cater for this; but for me , the enjoyment lies in improvising using cheap/free materials and solving problems using a home workshop.

This page gives basic details of a number of devices I have made (and a couple I have bought) to help my visual observations and photographic work. I can’t claim credit for all the ideas but I have designed each part to suit the materials and tools I have available. I am fortunate to have a fairly well equipped small workshop in my garage, but most of these items could be made by anyone willing to try a bit of DIY. The challenge is to adapt ideas and develop them for your individual needs - don’t forget to share them though!

Web cam Adaptors

I have been experimenting with a Phillips Toucam Pro web cam for astrophotography work. For this purpose it is necessary to mount the camera in a suitable position in the optical path. This can be at "prime focus" - the point at which the main lens (or in my case, mirror) brings a distant object to focus. This is close to the usual position of the eyepiece in a telescope but does not provide a greatly magnified image (just a brighter one due to the large, light gathering aperture of the scope). For a larger image the light must pass through the eyepiece and this is where the web cam adaptor comes in handy!

This unit can be used for all kinds of photography by changing the camera mounting collar at the end of the tube. It fits into a standard 1.25" focuser. An eyepiece (most commonly a 25mm one reclaimed from an old pair of binoculars in my case) is held inside the unit. The position of the eyepiece and the overall length of the tube can be varied to give very high magnifications although with this benefit comes the problem of arranging a steady mount!

The web cam generates AVI video files. I usually shoot clips of about 100-400 frames saved on an old laptop. These files are then transferred to a slightly more powerful machine via a zip drive. The AVIs are processed using free software called Registax2. This ingenious program aligns all the frames and stacks them to create an improved image. This can be further refined by adjusting the relative values of processed layers as well as colour and contrast. The output I usually use is JPEG and I sometimes tweak the images a little using Photoshop. It is important though, I think, to try and reflect what you saw when visually observing - not create something that wasn't there!

A recent addition to the collection is a small strip of expanded foam! I use this to wedge a standard 1.25" eyepiece into the collar from the back of the BS Astro unit. This means I can more faithfully reproduce the scale of images seen visually through any eyepiece - helpful for wider views and for demonstrating scope performance to others.

Collimation Tool

Collimation is the alignment of the optical components in the scope. In the case of a reflector this includes the primary and secondary mirrors and the focuser. I initially tried to do this visually with some success - the scope worked pretty well, however I wanted to make sure I got it right. In order to help I made this tool;

This is an aluminium tube with a small central hole at one end (where you put your eye) and a set of cross hairs at the other end (which is inserted into the focuser). I found a piece of tube which was part of an old TV Aerial and turned an insert to fit either end. The cross "hairs" are made from strands of fine wire separated from some electronics cable. I am fortunate to have a small lathe which makes this a fairly straightforward job in metal, but I have seen some good versions using 35mm film cases, made with limited tools.
All the tool does is ensure that your eye is positioned on the centre axis of the focuser and is "looking straight". All that remains then is to move and adjust the relative parts so that concentric reflections/views of the primary/secondary/focus tube are seen.
I did find that my scope was quite poorly collimated and although it probably isn't perfect now, I have noticed a marked improvement in the images produced.

Finder Scope

One accessory I quickly decided I needed was a finder scope. I did have a tiny one which came with a now defunct 40mm scope but this was poor optically and only picked up very bright objects. Here is the finder I eventually made;

The optics for my finder are from a damaged pair of binoculars. The objective assembly simply unscrewed but the eyepiece required some attention with a hacksaw and file to release it from the frame of the binoculars and make it cylindrical. These elements are held in short off cuts of white PVC waste pipe which have a wide split cut down the length. These are then wedged into either end of another length of the waste pipe. I painted the inside of the short lengths with some matt black BBQ paint and lined the main tube with some rolled up black paper. The whole job took about 20 mins.!

By experimentation I realised the optimum position for the cross hairs that help in aiming the main scope is at the focal point of the eyepiece (obvious if you think about it) This corresponded nicely with the end of the cut-off eyepiece, so all I had to do was cut some slots. Making sure two hairs actually cross in the middle is not an easy task as I found when I made the collimating tool but I remembered a technique used for marking out the centre of a bar in metalwork at school - namely use three lines. If, as is often the case, the lines do not properly cross the diameter of the circle, a small triangle appears in the middle. So, I used a craft knife to score some slots in the soft alloy of the eyepiece tube, cut three hairs from my daughters favourite "Bratts" doll (don't tell!) and super glued them in place.

I have added a diagram to explain.

This has probably been done before but not seen by me. The finder works well and the object you are aiming at is clearly visible in the small "target" triangle, not hidden behind a cross.

On the right is a view of the completed "head" of my scope showing the finder held in a traditional "ring "mount made from mild steel strips which are rolled and bent into shape before being spot welded together and painted with the obligatory matt black BBQ paint!.NOTE I HAVE NOW UPDATED THE FINDER SEE BOTTOM OF PAGE!

SLR Camera Bracket

In order to take long exposure astronomy photographs it is necessary to track the subject. An obvious way to do this, if you are fortunate enough to have one, is to fix the camera to your driven telescope mount. This technique, known as "piggy backing" is common for taking photographs through the normal lens of the camera rather than mounting the camera so the image comes through the scope itself. I have been keen to try this kind of photography so I have been making a bracket suitable to fix the camera to the 25mm square truss tubes of my scope whilst allowing a degree of adjustment.

This is very much a "work in progress" shot! This photo shows the completed bracket with “MinisolarCam” on board!

LED Torch

Not very high tech, this one, but very useful nonetheless! I utilised a small torch which had been "adjusted" by the children and was destined for the bin. Although the bulb was beyond hope, the battery holders and switch were salvaged and a short length of two core speaker wire was soldered to the appropriate terminals. At the other end I soldered a standard red LED and sealed everything up with some black Duct tape.

It isn't very pretty but provides just the right amount of red light to find things dropped in the grass etc. without ruining your night vision.

I usually put the battery end in my coat top pocket with the LED trailing out. I can hold the LED between my teeth leaving both hands free for fiddly jobs!

Observatory

This is still a long way off! I am sketching out some designs for a compact observatory. Although living in Selsey (close to the sea and on a peninsula) provides some quite clear skies, there is almost always a strong breeze (or tornado!). This makes observing a bit tricky and photography downright hard. An observatory would of course overcome the wind problems and also provide a permanent home for my scope and reduce setting up time to almost zero.
My garden is quite small with surrounding trees and streetlights near the boundary. I hope the roof will help cut out direct glare from the lamp posts but there is not much I can do about the trees. The scope therefore needs to be sited fairly centrally to allow low views of the eastern end of the ecliptic (the path of the sun and planets across the sky) hence the design below;

The diameter of the inner brick 4" wall and dome is about 8 feet. The height is 7 feet. The outer 9" wall provides a seat for the garden and the gap between it and the inner wall will either be damp-proofed and filled with soil to make a raised flower bed or will contain lots of planters and large pots for plants. The lightweight dome will be made from plywood ribs covered in thin plywood strips. the dome will be coated with GRP (fibreglass) coloured to look like a lead roof. The whole dome will rotate on a tubular steel ring fixed to the wall. I will need to design some nylon wheels or similar and provide retaining "hooks" for those windy nights! The viewing slot will probably bolt into place when closed and a small crawling height door (only about 1 metre high) will secure access.

I hope to commence construction in the near future.