Astro Meandering

It has been a while since my last astronomy post, having to spend all night studying tends to reduce sky watching activities. There have been several developments however.

The 200mm telescope has proved itself as a semi portable device, it was successfully dismantled and transported to Scotland by car where it was reconstructed with no ill effects. The de/construction process takes about 15 minutes and appears with not really change the required mirror tilts for columnation. The telescope was not actually used up there ( :( ) as Scotland in summer only really gets dark in the morning and the trip to Scotland was actually for an Orienteering carnival - something that generally requires the maximum amount of sleep possible!

One deconstruction/construction cycle later and the scope is now working back down south. I took it out for a quick test last night, the forecast promising clear sky and the moon offering a good target for finder alignment and focus testing. Of course the forecast did not include the predictable appearance of thin high altitude clouds after such a warm day so I only got to looking at the moon and a brief look at Andromeda before everything became obscured.

With a nice full(ish) moon I also had the opportunity to  test out my new phone's camera and the darkening filter I have had in my eyepiece box forever. I have put the nicest photos below, but be warned my skills are still low, I have yet to get the exposure settings right, and I really need to come up with a way of holding the phone that is not my hands so that I can fix the positioning of the camera aperture. There is however a marked improvement over using my old phone (not surprising) or the mighty 76 millimeters of the Drinking Straw, though I think the latter is more to do with mow much more stable the 200mm's mount is!

A full moon in a single image, showing some nice detail on the terminator (to the left).

No Moon-photograph session is complete without a photo of Tycho Crater.

200mm Scope: Drinking Straw Successor

The Drinking Straw successor is complete! which means,  I actually completed a project I set out to do ... in a reasonable time.

Complete!

Mandatory down the barrel shot

The ingenious 'double eyepiece location' - which hopefully will mean that I never have to pull off a feat of gymnastics to reach the eyepiece!

Please, hide your surprise.

As a recap, I have wanted to upgrade my smaller 76mm scope (the drinking straw) for a while since it became obvious that I had reached the limits of its capabilities. A couple of Ebay trips later and this step up had defined itself as a 200mm Newtonian reflector (given that I had a 200mm parabolic mirror).

One of the trickiest things to do with the drinking straw was keep it stable and non-shakey. This was largely due to the equatorial mount I opted for, firstly my own hideous creation, and then due to the properly made one being very, very heavy. The mount did have its benefits, like allowing for simple RA/Dec pointing and target tracking, and I enjoy using it. The thought of trying to replicate/use something similar, but scaled up for the 8 inch mirror, made my inner engineer very happy - but would not have been feasible in a device I could use in a reasonable timeframe, and also move around. Next time, next time. Instead I opted to follow the instructions from Stellafane on 'How to build a Dobsonian' given that I had already read the guide several times, it was easy to read with lots of information, and it seemed to be a bombproof way of getting a usable instrument.

So, onto a brief summary of the build - including interesting happenings, blinding insights and banal construction descriptions. In my previous post I talked about the design process which should have made it clear that I was deviating from the standard concrete pouring tube Dobsonian somewhat. Experiences with getting the length and balance point of the Drinking Straw wrong, repeatedly meant that I wanted to keep these properties of the tube as adjustable as possible. My solution was to have the optical tube made of three boxes all sliding along a set of poles. The three boxes held the mirror, interfaced with the mount, and held the secondary mirror/focusser/eyepiece respectively.

The design, with three boxes.

The build began with the mirror cell - which went together beautifully after I had managed to find all the bits (the springs were hard to track down, I ended up using RS having tried at least a dozen different hardware stores). At this point I think it would be good to add that I was beyond the range of the lovely laser cutter and its friends, but I did have access to my Dad's tool collection including a brilliant jigsaw.

The mirror cell, part of the way through construction (the pole holes are yet to be cut and the side mirror supports have not yet been added.)

The next step was to start building the boxes. My initial plan was to have boards perpendicular to the optical axis (with holes cut in them) as structural braces/imitation baffles, the box would then be made of four rectangles of plywood on the sides, held together primarily by the braces. This did not quite work out, which I will talk about later.

The Braces were my first attempt at cutting circles with the Jigsaw which I knew was going to be critical to making the Altitude bearings later on. I did my late night research into how people generally cut circles with a jigsaw and came up with a very useful jig-saw jig which constrained the blade to a circular path. Unfortunately for the first few boards to have their holes cut it took me a while to figure out how to keep the Jigsaw blade straight.

Jig saw circle jig, idea scooped from a random YouTube video

A not so successful circle cut.

After cutting the braces out it was time for the far simpler sides of the box - these were just rectangles with some pre-drilled holes to guide the various screws and nails that held the box together.

The next step involved a bit of improvisation. I may have mentioned before that I did not really know hoe I was going to secure the poles in place when I initially designed the telescope. Eventually I cam the the plan of using hose clips secured around a plank of wood (itself secured to the box) that could be used to keep the poles still relative to the box, while still allowing the poles to be released for taking the telescope apart. It turned out that this was a brilliant idea, not because it held the poles securely, it turned out that friction against the braces and sides did a good enough job of that, but because the planks of wood did a far better job of holding the boxes together than the braces!

The first box constructed (which would turn into the pivot box)

Another thing that developed during construction was the finish of the wood used. I knew I wanted to use some sort of wood-stain on the wooden elements of the telescope to weatherproof it, and because I did not like the idea of paint. The final wood-stain used was one I found at the back of a shelf in the garage, supposedly a 'natural oak' colour. So far it has worked quite well.

Next up was throwing together a secondary mirror spider/holder, here I just drilled some holes in an 18mm thick scrap of Plywood for push/pull bolts to go through to tilt the mirror. the spider was a set of steel bracket strips that I bent into shape. The entire assembly manages to stay behind the secondary mirror (from the perspective of the primary mirror) and the steel strips are edge on to the light path while still being quite thick. It is a solution that works well enough for the moment and holds the secondary mirror dead still, but will probably require upgrading in the future. as it is not particularly easy to use the push pull bolts.

The secondary mirror spider, with nice curved vanes. The mirror holder was just a block of wood with some holes drilled in it. I sandwiched some nuts on one side of the wood using a 5mm wood scrap to give each bolt hole a durable thread.

Another view.

The rocker box, altitude bearings and ground plate went together in a couple of days (surprisingly quickly). The altitude bearings took all of my skill at cutting round objects with a jig saw to the limit, but they came out spookily well. The biggest improvement came after I changed to a slightly thicker blade which seemed to wander less easily.

One of the trickiest bits about this last stage was deciding on different wood thicknesses, the process of choosing the other dimensions already has a lot of guidance on the internet. In the end I used:

• 18mm for the bearings and sides (to maximise the bearing contact area), 
• 5mm for the front (to save weight, the front does not have to take much concentrated force that would require thicker wood), 
• 9mm for the bottom of the rocker box and ground board (as it was the only material I had left in sufficient quantity)
• 12mm for reinforcement on the bottom of the ground board.

To protect the ground board from excess moisture and also to give a good set of contact points I screwed three cheap plastic castor dishes (turned upside down) to the bottom of the ground board too, so far these have worked really well.

Test fitting everything in the bearing/rocker box/ground board assembly before coating with wood stain.

Finally there were a couple of later improvements, I added braces to keep the altitude bearings straight and added nonstick pads and laminate to each of the bearings to improve the movement action. The work with the bearings would have been included as part of the rocker box assembly but I was initially quite happy with the simple wood on wood bearing, it took a couple of evenings for my mind to change.

The rocker box all finished, you can just about make out the altitude bearing braces.

Overall this has been an enjoyable project with a concrete outcome, it was a matter of minutes before the 200mm scope was showing things invisible to the 76mm scope on the first night of viewing. Unfortunately it will be staying at home while I travel to Uni but I can still continue to work on bits and pieces for it, I already have my sights set on making a finder of some sort to help navigate around the sky. Additionally eagle eyed readers may have noticed the somewhat gargantuan secondary mirror, which is almost two cm to wide (across the minor axis). At some point I will get around to replacing it with a more appropriate mirror.

200mm telescope: The Drinking Straw Successor

So - I have managed to secure to optical components for a nice 8 inch telescope with the plan to put one together over the summer.

While I am really excited to see what the new telescopes capabilities will be (the focal length of the primary mirror is not that much longer than the one in my 76mm scope so most of the benefit will be in extra light gathering capability) I am almost more excited about the construction project. Given that this will be a summer project I will be away from the University and its many CAM machines. On the one hand this is good as it means I can use materials that would catch fire in a laser cutter, but it also means that all manufacturing will need to be done by hand!

Counter-intuitively, this lack of laser cutter makes the design step even more important - because correcting mistakes is going to be a pain! Therefore, armed with some idea sketches and optical dimensions I threw together an Inventor assembly to try and get the dimensions right, and usable.

The profile shot, I have a couple of objects for scale (all disabled at the moment lol). They showed that the telescope is going to be very usable, except it may need to be on a table if looking at object near the horizon!

More of a beauty shot, down the optical tube

The CAD work has been a bit of a learning exercise, playing around with texturing and movable joints, as well as how to best use the assembly system. The standout awesomeness was the fact that my Crayford Focusser design could be imported and tried around on the model to make sure it fitted!

Anyway, I am sure that there will be plenty more to talk about/take pictures of soon!

Jupiter at oppositon

Doesn't look like much - until you realise the spots are moons! From left to right we have Ganymede, Io (hidden in Jupiter's glare), Jupiter, Jupiter again reflected off the camera lens, Europa and finally Callisto

So with Jupiter at its shiniest this evening, and the sky at its clearest I dragged my flatmates out to have a quick look through the telescope. One of them had his phone with him and managed to get this picture through the eyepiece! It is no Hubble image - but it does show the moons (three of them anyway).

Visually, the view was rather good, the banding was obvious, either the Southern or Northern Equatorial band (depending on how the image was being flipped in the telescope) was particularly prominent. The gradual upgrades to the 'scope are becoming obvious, the view is now far steadier than before which finally means that the view will stay still long enough to allow me to focus properly and to take advantage of any short periods of good seeing.

Focuser Complete

The focuser is complete!

Actually it has been complete for a week, but I have been too busy enjoying the sky to post about it.

Turns out that I am not yet genius enough to design something to work first time just yet: during construction there were some improvisations I had to make with the original design that I will go through below.

Now that the focuser is working the difference in viewing quality is enormous. Being able to get the focus exactly (okay, not quite exactly) right without shaking the entire scope, as my friction fit focuser did, means that I can get sharp images without the telescope moving itself away from a target.

This will hopefully mean that I can finally start using the telescope to the limit of my optics. This is a welcome change from the limiting factor being something that I have done (or not done!).

The focuser

The focuser still needs a bit of touching up, at the moment the axle bar is a threaded rod which can lead to interesting interactions with the securing bolt and tends to shred the eyepiece holder. It is also 1mm too thin - I am probably going to take a quick trip to the hardware store soon to find a replacement and solve these issues.

Additionally, I managed to find a PVC plumbing fitting that fitted my required dimensions, but now is acting as a brilliant reflector of stray light into the eyepiece - I am going to have to paint it black at some point.

Finally my method of attaching the focuser to the scope can be seen above, it is not very pretty, but works well enough, for now. At some point in the future I may get around to improving the mounting mechanism.

Shot straight through the eyepiece slot. One of the things that did work were the four bearings which, due to a combination of brilliant datasheets from RS and the precision of the laser cutter, are precisely where they need to be.

The revised fastening mechanism. It seems to work quite well.

 One of the things that changed dramatically was the fastening mechanism. I turned out that I had not left enough room for the spring in my design. Looking around the web at other homemade focusers revealed that a surprising number simply used a bolt pressing on the axle to secure it. This also solves the longer term problem of the spring wearing out as the spring is now provided by the structure, it also saves me a wing nut for use in future projects.
I have epoxied a nut on the axle side of the back plate to hold the bolt, with a cannibalised section of the original pusher plate used to provide extra counter-torque on the nut. One of the problems that has arisen from the threaded rod being used as an axle is that it likes to move left to right (up-down in the photo above) when it is turned while under pressure from the bolt. This is usually fine, but can be a surprising pain.

Mirror holder - modified!

The final modification was probably the scariest, and is likely going to require more work in the future. Because the new focuser is about 3cm taller that my old loo-roll eyepiece holder, I needed to shorten the tube of the telescope by about this amount to move the focal point of the mirror. By pure chance, when I had originally put the tube together I had made the main spars out of two shorter sections of wood bolted together. This meant that shortening the tube was a simple matter of swapping out the shorter of the two pieces with an even shorter piece (as seen in the photo above). I was a bit sad to say goodbye to some of the last remaining original and reliable components of the telescope.
Unfortunately, because he tube shortening only occurred at one end, and the current setup does not allow me to slide the mount attachment point around, this has thrown the balance of the telescope off. Even with the proper mount, the front of the telescope really wants to drop. While I could revert to the old method of hanging a bag of rice from the mirror cell, I think that the longer term solution is going to be rebuilding the telescope tube assembly as this will also allow me to incorporate some of the lessons I have learn't (like having a movable pivot point).

One quick project down, how many more to go?

Telescope focuser

First post for the year is a surprise blast from the past: progress on the telescopes focuser - please try to hide that rolling of eyes.

So, almost a year after throwing the first bits of the telescope together I finally got into the mood to do some serious design work on the last major element of the telescope left - the eyepiece focuser.

Up until this point my eyepieces have been held in with friction and toilet rolls which is not to stable and does not allow for fine movements of the eyepiece. With the gradual upgrade in the other system components the focuser has finally become the weakest link.

A quick google search can show all sorts of brilliant designs - most of which have been made by someone else who is trying to sell them to you. Luckily there are also scattered articles of people making their own - generally with the a high level of ingenuity that most amateur telescope makers seem to possess by default.

In particular the ingenious Crayford focuser design, while used in high end commercial models, has been constructed in all sorts of ways including from assorted wood and plumbing scraps. That sounds like something I can do - especially when I have my trusty sidekick: Mr Laser-Cutter (its a double barrelled name).

I have just finished my CAD model ready for a workshop session sometime soon, which incidentally means I have pictures:

the focuser - note that my CAD skills are limited - I have not managed to put all my parts in an assembly to make the design look completely pretty.

The top view - hopefully the holes for the two bearing holders are visible on the left hand side of the image - the pressure will be applied with a spring pushing a pusher plate against the axle (which will happen on the right hand side of the image.

The pusher plate, I have tried to reduce its contact area with the rest of the focuser while maintaining its ability to stay straight by giving it the bowing in sides.

New academic year == new projects

Another year of Uni has now begun, with the promise of a number of awesome projects to work on. This is not to say that the current work is going to be dropped, the Blake project in particular is continuing with the deadline of being complete by June next year.

However, the excitement always lies with the shiny new projects with all of the potential and none of the pragmatism (yet):

Being on the committee for the university's space society has meant that I was hoping to be able to push some electronics into the normal roster of rocket and rover projects. This push has resulted in the Solar Flare Detector being adopted as a project for this year. Consisting of a VLF radio receiver the end product will be able to track the sudden ionospheric disturbances that usually accompany flares hitting the Earth. Before you go and talk about us heading towards a solar minimum at the moment, which we are, there are still flares to be detected - just slightly smaller and less frequent flares. This project is currently starting up and already providing interest in the society from a broader range of subject disciplines, beyond the usual Aerospace Engineers.

The society is also re-entering the UKSEDS lunar rover competition after our successes last year (we came second), hoping to build on our design which ended up being decidedly improvised towards the end. It is likely the electronics are going to get a major overhaul but this should not be too hard given we now have experience.

Finally (for the moment) being the third year of the degree part of the assessment this year involves a group project. The aim of this project will be to produce a machine capable of solving a Rubik's cube. There are several restrictions that are going to add cool (and not obvious) electronics - I am sure that these will turn up in a future post.

Ongoing projects include the brilliant Blake Project, now cruising to completion - some sneakery is going to allow the accelerometer problem to be sidestepped, again I am sure that this will be written about somewhere else. The track itself is also slowly being completed - the workshop restocked perspex for the new term, and I immediately helped myself and spent a happy couple of hours producing all the parts needed.

At an even slower pace is the telescope, dredged from the depths of the blog. While I have really enjoyed using it so far there have been certain areas that either need improving or have already been improved. The mount (both tripod and pivot) have both been replaced with far more capable, but sadly not quite as DIY-y, elements. My range of eyepieces has also increased beyond a single dodgy 7.5mm plossl. Using the new setup I can clearly see all four stars in Mizar/Alcor, some awesome detail on the moon, the rings of Saturn e.c.t. However there is still more to do, I would like to 3D print an eyepiece holder and at some point I am going to need to replace the current optical tube frame.

All good things to look forward to, an hopefully write about!

A Summary:

Ongoing Projects:

1. Blake Project (at a slower speed during the academic year)
2. Telescope (gradually improving portability and stability)

New Projects:

1. Solar Flare Detector (cooler acronym incoming)
2. Rubik's Cube Solver (for degree)
3. Lunar Rover Mk. 2. 

On to the Back-burner with ye!!

So, turns out that manipulating many images, rescaling rotating and moving squillions of moon fragments all at once is rather RAM intensive. Or at least it was with GIMP. Several evenings of 100% memory usage for "this program is not responding" later and Operation Sandra Voi is not looking very healthy. That and the fact that I now have a new set of eyepieces with focal lengths greater than 10mm (which means I can see and image the whole moon at once), means that I shall suspend the project until I can image through the telescope slightly more reliably.

Astronomy has not ended for the moment, Saturn is coming up at the moment which is looking very nice, and I have started looking for some of the Messier objects. Of course they are all far too dim to be photographed, so no nice images.

Anyway, onward to the next crazy project!

The telescope continues...

Soooo - I may have built another telescope and not documented the process at all. Which is a bit of a problem as I now have a folder full of CAD files with really odd, but meaningful, names (like: "SlottyThings.ipt", why did my past self do this to me!). Luckily I have some nice work in progress photos, even if my in depth description may be a bit lacking.

The telescope is a 76mm Newtonian reflector with a potentially equatorial mount. The optical tube, and mount were built using the university laser cutter. Unfortunately I am not yet skilled enough to make the mirrors, mirror cell, tripod or eyepiece myself, so they had to be purchased/scrounged.

The optical tube with the two cheaty elements, the secondary holder and the primary cell. I like the fact that it looks like a big ray gun!

Tube clad in a sheet of black fabric to guard against light pollution, with two points of interest. One, the photo is from before the final mount was assembled so the telescope is attached straight onto the tripod. This was way too shakey and has not been done since. Additionally, you can see the £5 telescope in the bottom right corner! Safe to say the new telescope is incomparably better.

Drama shot, now with proper mount. There have been a couple of modifications since this photo to stiffen up the mount and tripod, but essentially the telescope still looks like this.

Of course no project would be complete without an even more ambitious project to follow it. Thus, "Operation Sandra Voi", the plan is to produce a mosaic image of the moon by stitching together lots of smaller images. My eyepiece's field of view is quite limited, so this is the only way I can produce a complete picture of the moon, and hopefully it will look really good when it is done: I can always go back and re-image sections that are either incomplete or of poor quality after a first pass.

"Sandra Voi" is named after one of the lighthuggers from Alastair Reynolds's Revelation Space series, only mentioned in passing a couple of times, it is an exploration ship just as hopefully the project will help me explore astronomy (ha ha, maybe I should have come up with a cool acronym instead). The naming scheme does leave me with a bit of a problem as I haven't thought of a cool enough project to call "Operation Nostalgia for Infinity" yet...

Photo, apologies for any confusion, due to the optics of the telescope the image is flipped, I also have no idea about the rotational orientation! I am fairly sure that it is the boundary between the Mare Serenitatis and Mare Imbrium, with a fairly faint Copernicus crater at the top of the image.

Preliminary mosaic with a nice template in the background kindly provided by good 'ol NASA.

the £5 telescope

Sooooo - haven't posted in a while, but I think this one will be the first of many in the near future.

The title is true (approximately), on the day I built the telescope I spent less than £3.50 - but I already had convenient tubing and tape lying around.

Long story short, I decided to have a rather strong coffee on Tuesday morning and that evening, having buzzed around all day, I had built myself a 75mm aperture refracting telescope. Why? Well I have always enjoyed looking through my dad's telescope back home, pointing it at Jupiter, Venus, Mars, the moon and whatever else happened to be along my line of sight. I have been having withdrawal symptoms ever since coming to uni, but my recently completed work for the ESA "fly a rocket program" (more on that in another post) tipped me over the edge.

How did I do it? Search up refracting telescope on google and you will get all sorts of lovely diagrams, adverts, pictures and links to educational websites. Trawling through this lot left me with two impressions: 1. Whatever I built wasn't going to produce pretty images - the colours would blur away from the centre of the image, the image would be flipped and shapes may end up distorted as well. 2. Magnification is done at the eyepiece (the place where your eye goes) - a good goal for the main telescope-y bit is to get it as large as possible, both in diameter (to get as much light), and length (as this counters 1.), but these are both limited by the lenses you use.
Off I went to find a nice big lens to put at the front of my telescope, the correct name for this lens is the 'objective'. Hundreds of years of gradual improvements to telescope design started pretty much immediately by getting rid of the standard convex lens as the objective, instead using all sorts of wonderful shapes to limit colour blurring.

HA HA HA. 

75p later I have myself the greatest abomination of an objective lens in the form of a wilco magnifying glass. At 75mm across it is not the biggest lens, but it is a lot bigger than my eye which is actually the important bit. Another ~£1.50 later and I have myself a pair of small binoculars from a charity store, ready to be killed and resurrected as my eyepiece. None of this is going to work fantastically, but all I want to do is not have only my eyes to look at the stars with.

So having spent the entire day polishing my new objective lens I rushed home to begin construction!! The key thing I was concerned about with the focal length of each of my lenses (including the ones from my binoculars). This simply involved pointing a lamp into the lens from a long way away, and then looking to see where the image came out clearly on the other side:

As you can see I had lots of fun with little pieces of tape, the first black piece after the big lens marks the focal length of that lens while the white pieces were used to measure the distance from the target to my eye.

One of the key mistakes I made at this point was to check for magnification. This being my first recent foray into optics, I really didn't want to manage to make an incredibly convoluted way of looking through a cardboard tube, with all benefits brought by the lenses cancelled in some way. As all I wanted to do was see some of my favourite nighttime targets a bit more precisely, I didn't really care how much magnification I got, simply that it was more than none. Thus I spent ages with the white bits of tape, checking angular sizes of things with and without the lenses, only to realise later that magnification comes primarily from the eyepiece, which usually like to sit very near the focus of the scope - which simplified the design immensely.

Construction was very simple:

1. Take cardboard and cut section off with  a length corresponding to the focal length of your objective lens, I tried with a slightly longer tube to begin with but this did not work at all.
2. Cut another much shorter section of cardboard to act as a light shield in front of your objective lens.
3. I then added slightly smaller rings of cardboard inside the two sections at the ends where I was going to put my objective lens to help mount the objective lens and keep it still once the telescope was complete.
4. Then tape the cardboard sections together with the objective lens between them.
5. Now we need to have some sort of mounting for our eyepiece (s). Looking around the web you can see that most mountings allow for the eyepiece to move towards and away from the objective lens to help focus the output image. I took a ring of cardboard with a diameter such that a toilet paper roll could slide through it. I then took a convenient object matching the cross section of my main tube (the end of the tube for when it was a postage tube), cut a hole at its center with a diameter corresponding to my loo paper roll collar, then taped the collar into this hole.
6. Bodge an eyepiece. I am still doing this. Actually looking at eyepiece layouts was a good start, I eventually opted for a Ramsden configuration as this was the best I could do with the lenses available...
   

My conclusions...

£5 for any telescope would be good, but building it has meant that instead of a rubbishy kids second hand novelty scope I have ended up with a passable scope with an alright aperture and plenty of potential. At the moment the telescope mainly just focuses images, without enhancing them too much, but with some more lenses (and a bit of practice) I think that new eyepieces would drastically improve the telescope's performance. The dodgy objective lens reduces the potential utility of the scope: colour bleed and image distortion are utterly pathetic, and this project is missing the crucial element of any true telescope - the mount.

I envision many happy evenings spent looking at random celestial objects with the telescope, but in reality I think my efforts in telescope building may have only just begun...