[update in Progress] Bring Your Heritage to the Moon !

[Version française ici]

!!! Warning !!!

Big update in progress ! the french page is up to date, please refer to it for 3D files and instructions

Ah, the Sky-Watcher 130 Heritage !

Perhaps one of the most inquired about telescopes by beginners, thanks to its affordable price, and the one about which the regulars have the most mixed opinions because of its technical limitations.

Its mirror is very good (for this price range, let’s be reasonable here), the general design is well thought out and it’s very compact and easy to carry.

But then, its wobbly eyepiece holder, its single branch spider, its floating mechanics, all these constitute drawbacks when you want to dabble into astronomy under proper conditions.

So, how do you turn this inexpensive little telescope into a real war machine?

The adventure began during the Great Lockdown in Spring 2020. I spent the first few days catching up on Netflix (like everyone else) and then I started chasing my tail. Like everyone else. I had to build something, anything! And then, I stumbled upon this: my little telescope, which I have used only a handful of times to observe the Moon and Saturn and which had been collecting dust in a closet since last summer.

When I visited various astronomy online boards, little did I know that I was actually sticking my finger into a black hole that will end up swallowing me for nearly 18 months. Being a total newbie, I learned things the hard way, looking for a solution to each and every problem that I encountered, only to find out that someone else had already brought it up and resolved long before.

A few (hundreds) of hours later and there I was, with a more or less functional first version. It is then that I discovered the Stellina: a fully automated “2.0” telescope, incredibly compact and devilishly powerful … with a hefty tag price near €4,000.

And this was my eureka moment: it was what I wanted to build, even though I didn’t know it at the time! Only, I wanted a DIY version that would be more efficient and above all much cheaper (although a little less plug-and-play, I have to admit).

I was back to the drawing board, with (many) visits to the workshop and the purchase of a 3D printer. In the meantime, I spent the winter on a small side project (namely a homemade camera with a full redesign of the electronic board), and, by the end of spring 2021, the first version of the Mark III was released. The last tweaks took place during the summer and the project is currently in its final stage.

Here is the tutorial, it will allow you to build this mod all by yourself from the off-the-shelf tube and a handful of parts.

On the budget side, you’ll spend some €250 for the supplies and various materials (excluding tools, of course, and electronics, see step 3). Concerning the 3D printed parts, you’re looking at almost 90 hours of printing with your trusty printer, and just under 1 kg of filament.

And if you don’t have the telescope yet, you’ll find it here for instance : PierroAstro - Optique Unterlinden - AstroShop

To complete this change, you will need the following hardware:

• a 3d printer

The project was carried out on a Prusa i3 MK3S + , but most printers will be able to manufacture the parts. The largest piece is the AZ axis crown, which is 21cm. The highest part is the light shield, but it can be cut into 2 parts. The most critical parts are those with a standard T2 thread. The settings shown are named after PrusaSlicer, the name may differ depending on your slicer, but you should be able to find them all easily.

Experiment with the test pattern below, until you have successfully printed this part. If it passes, it's won for the rest! Take the opportunity to test the printing with different settings depending on the parts of the part: standard quality (0.2 mm layer) at the bottom, and maximum quality for threading (from 5 mm).

The files provided are in STL format (the only format available on Instructables), but you can find files in 3MF format here , with the presets for PrusaSlicer.

• the filament course

All parts are made of PETG . This material is not much more expensive than standard PLA, it prints easily and has better mechanical properties. We can of course use PLA for assembly accessories, but optical parts in particular need a maximum of rigidity . If you are familiar with printing technical plastics, such as Nylon or Poly-Carbonate, or even filaments loaded with carbon fiber, it is even better, but not at all essential.

There is one part that is best printed in flexible filament (the "flex" family), which is only possible on direct drive printers. Don't panic, a piece of PETG and felt pads will also do the trick.

• a drill press

No need for a professional machine tool! a simple column support for drill is enough, it is to drill more easily and quite straight . This kind of model ( Castorama or Amazon ) will do.

Don't forget to put a martyr board on the vise, otherwise it will end up in Gruyere (and your wood bits won't like that at all)!

• of drills and milling wood

A box of wood drills (2 to 8 mm), and flat bits ( as here ) or wood cutters ( as there ) of 22 and 32 mm.

• the common small tools of any good workshop

pliers, screwdrivers, ALLEN wrenches, flat wrenches, soldering iron, neoprene glue ...

• some hardware

wood screws, metal screws ... details are specified in each part. For metal screws, prefer those with a hexagonal head, which are more solid.

• of threaded inserts

If you've ever tried screwing into printed plastic, you must have found it works ... once! And then, it's a bit of a disaster. So take the plunge with the metal insert! There are assortment boxes that will be used again for future projects. Be careful, not all inserts are created equal, Ruthex is a safe bet.

• a collimation tool

We are going to dismantle the secondary mirror, so it will have to be adjusted at the end of the operation . There are plenty of accessories, from the simple cheshire (a specific eyepiece to collimate your device) to the laser collimator ... browse the Youtube tutorials to find yours.

• some PPE !!!

Or "Personal Protective Equipment". How stupid to lose an eye, how to use the telescope next! Cut-resistant gloves , a pair of protective glasses , a noise-canceling helmet are the essential companions of the careful handyman.

• The drilling guides (and a little magic key)

If I told you "Then you have to drill a hole 43.5 mm from the bottom left edge, offset 13 mm from the rounding here ...", it would not be easy! But don't panic, here is a series of guides that will allow you to drill in the right place the first time! As a bonus, the model of a DIY hook wrench , to unscrew the nuts of the tubes (those with the 2 small holes, that you wonder how the hell to disassemble them!)

These parts are for "single use", they will no longer be used once the modification of your telescope is complete (except the key). You can print them with any material, any color and with your standard settings.

First step, correct the basic defects of the telescope!

These are not even really flaws ... To come out with such a tight price, Sky-Watcher had to make compromises, some more annoying than others, but nothing that cannot be fixed when you are motivated!

The centerpiece of a telescope is its mirror, and the 130 Heritage's is pretty good. For the rest, let's see what we can do.

The secondary school cage

This is the part which is located at the end of the 2 telescopic tubes, on which the eyepiece and the finder scope are mounted, and which supports the secondary mirror. The 2 main faults are:

• the mirror support which has only one point
• the eyepiece holder that has an abominable game

Let's go straight to the point: we change the whole room! 3D printing allows miracles at home, so let's not shilly-shally, and make our own secondary cage. And by the way, we are going to add a light shield, to avoid being bothered by this lamp, there, the one just at the corner of the street...

The part is in 2 parts, which allows to print the T2 thread (necessary to fix the focuser) flat and thus have a nice regular thread. As noted above, this part is the most technical and will push your printer to its accuracy limits.

A side effect of this modification is the change of the focal plane, the new focuser is found further than the origin. But no problem, thanks to the Flex-tube system, you can shorten the tube. Use the set of shims provided to find the correct setting (it should be around -25 mm).

Pro tip: print them in white or even in phosphorescent, to find them easily at night, and put a little marker on the top of the numbers to read the sizes more easily!

Material list :

• ZWO helical focuser : PierroAstro - Unterlinden optics - AstroShop

After having tested several models, it is the most practical and the best suited to this modification.

• red dot sight : PierroAstro - Unterlinden optics - AstroShop

Among all those who have been tortured (for science!), this one wins the 1st prize hands down. It can also be found on the side of air-soft accessories, it is a generic model. If you buy it without its stand, a 3D model is available. It's a fistful of euros saved.

• Screw M4 x 16 mm x3, countersunk head
• Screw M4 x 20 mm x1, normal head
• 4 x 16 mm wood screws
• Threaded insert M4 x7

Print settings

• layer height: 0.2 mm

For the focuser, the thinnest possible for the thread (from 13mm). No need to print the whole part in 0.05 mm, apart from spending the night there it will not add anything to the print.

• Perimeters: 4
• Top and bottom layers: 10
• Supports: yes, everywhere
• Infill : Gyroid 15%

Secondary assembly

1. Using the spanner wrench, unscrew the 2 nuts that hold the secondary cage on its tubes. Lay your tube flat to work, it's more comfortable and above all it will prevent a part from falling on the mirror!
2. Remove the secondary mirror (central screw): be careful, there is a spring ! Hold the mirror well so as not to let it fly away. Then collect the 3 grub screws.
3. Fit the threaded inserts : 3 for the mirror support, 3 for the focuser support and 1 for the finderscope support. The usual technique is to place the insert at the end of a soldering iron (hot! Use pliers not to burn yourself) and to insert it hot, up to flower, by pressing lightly. The insert will find its way to the bottom of the well. A small quarter turn of the iron, counterclockwise, just before removing it will ensure that the tip does not get stuck in the net.
4. Reassemble the secondary mirror , adjusting it as best as possible towards the focuser (we will do the collimation at the end).
5. To install the light shield, mount the cage upside down on the tubes (mirror facing the top of the tube), present the light shield in the cage and turn it until the 2nd click. The edges should be in contact with the branches of the spider.
6. Put the assembled cage right side up, tighten the 2 tube nuts and secure the focuser support with the countersunk screws. Tighten each screw a little, and move on to the next, so as not to place the part askew and gradually tighten. Make sure you are flat and that there is no play between the 2 pieces.
7. Fit the screw of the finderscope support in its insert, after having installed it in its knurled nut.

Here it is, it's over , you have a world-class high school cage!

If the original red dot finderscope isn't right for you, you can now mount any standard model like the one shown in the hardware list, my favorite.

Tube resting base

Such a small telescope makes you want to lug it around everywhere, but having to disassemble the tube is really not practical ...

The solution: a support block on the base, to keep the tube in position! This is where we find the flexible filament part announced above: it will perfectly hold the tube and absorb small shocks during transport (small! It's still a precision instrument, don't throw it on the ground).

For installation, install the tube vertically on the support, and slide it into the dovetail (without screwing it) so that it is in position but without constraint. Mark the position of the bracket on the wood, and secure it with the wood screws. Then glue the 2 pieces together with neoprene glue.

Well done, the Mark I stage is over! Your telescope is ready for comfortable visual observation.

But after so much effort to point to a barely visible planet or galaxy, what a frustration to see it come out of the eyepiece so quickly ... No problem, there is a solution to this: the Mark II stage.

Do you want more ? Are you that kind of person who is willing to spend hours tinkering with something to save 30 seconds afterwards? If so, I see you. And you wouldn't be here otherwise, would you?

For the Mark II evolution  , we will automate this Heritage so that it  points to  the sky by itself, and  follows the object  you want to see!

Here it will only be a question  of the mechanical part  of this modification, the electronic part will be carried out on the basis  of other existing  and mature projects , such as  OnStep  (the most versatile, but complex to begin with) or  TeenAstro  (a derivative of OnStep which focuses on the ease of realization, and led by a French team). Both projects are capable of piloting the Heritage motorized mount.

The basic principle is to use  stepper motors  to move the 2 axes of the mount. As their name suggests, these motors work one  step at a time , and therefore it allows  precise control of the rotation  of the axes.

come on, let's get it all done!

Material list :

• NEMA17 400 step x2 Stepper-Online motor
• Needle stopper 8x21x2mm x2 123rolling
• Needle stopper 10x24x2mm x1 123rolling
• Thrust washer 10x24x1mm x2 123rolling
• Needle stop 76.2x95x1.984mm x1 123rolling
• Bronze bushing 8x14x16mm x1 123rolling
• Caster M 4x19x5mm x3 123rolling
• Amazon 20 tooth GT2 pulley
• Amazon 6mm tensioner pulley
• Belt GT2 2mm 400 teeth (800mm) Amazon
• Amazon GT2 2mm Belt 335t ( 670mm)
• Screw M4x25mm x3
• M3x20mm screw x8
• Screw M4x20mm x4
• M3x10mm screw x2
• M8x30mm screw x1
• Nylstop nut M8 x1
• Large washer M4 x3
• 4x16mm wood screws x3
• Threaded insert M4 x4
• M3 threaded insert x2

Print settings

• layer height: 0.2mm
• Perimeters: 3
• Top and bottom layers: 4
• Supports: on the shelf only
• Infill : Gyroid 15%

Preperation

1 - Drilling templates

Now is the time to print the drilling templates. They are adjusted to fit perfectly on the different parts of the frame, snapping on the existing holes in the wood.

2 - Assembling the printed sub-elements

Place the casters in their supports , and screw them in place with an M4x16mm screw  .  Lock without exaggerating.

Install the inserts in their location:  3 M4 inserts  in the large AZ crown,  1 M4 insert  and  2 M3 inserts  in the belt tensioner.

If you cannot find a belt of the adequate length, you can buy it by the meter, cut the desired number of teeth, and close the belt by gluing a 10cm end on the back (flat side against flat side), with glue for tubeless tires (vulcanization principle).

Fit the pulleys on the motor axles, leaving a 7mm gap  with the motor body. Place the ALT crown around its axis, on the dovetail support.

Assemble the belt tensioner with 1  M4x12 screw  in the center, one M3x20 screw   for the tensioner pulley and one M3x10 screw   for the tension lock.

3 - Dismantling the frame

Start by separating the 2 parts of the frame by unscrewing the central bolt. Remove the plastic covers from the screws on the vertical part of the mount (the rocker), and dismantle the 3 parts. Also disassemble the ALT axle with the dovetail holder.

Construction

4 - Assembly of the base

Place the template on each of the 3 angles (placing the central stud correctly) and  mark the 3  outer holes with a 3mm drill bit. Drill the 8mm hole  , then the 32mm  hole  with the flat bit (or a wood bur).

Position the 3 caster supports and screw them in place with the wood screws.

5 - AZ motor assembly

Place the small template under the base of the rocker (on the side where the screw holes are cut out), drill the 4 outer holes with a 4mm drill bit . Mark the central hole , then drill with the  22mm bit (by removing the template, of course). Install the motor with the  4 M3x20 screws , the wires facing towards the reinforcement of the vertical part.

Insert the  M8 screw  in the AZ crown, place an  8x21 needle stop  (the needles on the bronze ring side) above, the bronze ring and mount everything on the base of the rocker. Place the other  needle stop 8x21  (always the needles towards the bronze ring) then screw on the Nylstop nut. Adjust the tightening of the nut to have a free rotation without play. You can fit the belt , starting with the engine pulley then rotating the crown: the belt will position itself.

6 - Assembly of the ALT engine

Place the guide on the vertical part of the rocker, drill the 4 motor holes at the 4mm drill bit, mark the other holes  at the 3mm drill bit. Drill the top hole (tensioner) with the 32mm flat bit , and the bottom hole with the 22mm flat bit (motor).

Install the motor with the  4 M4x20mm screws , so that the wires are towards the other motor once everything is reassembled.

Fit the belt tensioner with the  2 wood screws .

7 - Assembly of the ALT axis

Remove the original Teflon disc, and glue the new printed disc in its place . Carefully cut the collar of the original plastic insert , so as to keep only the inner part of the tube.

Install the large  needle stopper  on the axle, slide the plastic insert and put everything back on the wood. Place the first original washer (the one that passes freely through the threaded part). Warning:  there is a slight chamfer, it must be placed  on the wood side  ! Fit a thrust washer, the small needle stopper and the second washer, then the screw washer. Secure everything with the handle. If the assembly is good, you should be able to   completely block the handle while keeping   the axis free to rotate . It is played to the tenth here! If it gets stuck, reverse the first washer and try again.

You can now fit the ALT belt , then adjust the tension using the tensioner. The belt must "vibrate" like a guitar string, but without forcing too much (we are not bullies).

Finish with the protective cover, after screwing in the vertical reinforcement. Place it in the holes of the 2 vertical screws, and secure it with  3 wood screws .

8 - Final assembly

Reassemble the vertical part on the base of the rocker using the 3 screws, then install it on the base of the mount by placing the 3 inserts in their holes. Complete the assembly with the  3 M4x16 screws  and their large washers.

Well done, you have just  motorized your telescope  ! Impressive simplicity, right?

OK, there is still the electronic part to be done now. Do not hesitate to subscribe to the discussion lists of the project you have chosen, you will find support there in case of difficulty.

But now that it moves automatically, we could put a camera in it, right? The Mark III is waiting for you right after!

You are still here ? Did you know that a telescope is meant to be used? Outside, what's more (the outside is "the other side" of your workshop, if you had forgotten)

Sorry ? It is raining ? Has the sky been cloudy for weeks? Alright, so let's continue, to infinity and beyond!

Last step: optimize this tube for astro-photography , or rather what is called " assisted visual ": the observation of the sky by taking advantage of the sensitivity of modern cameras to quickly see objects invisible to the eye, for the purpose of "live", instead of collecting hundreds of photos that will then have to be processed to draw a portrait of galaxies and other star clusters.

Material:

• a  camera

which ? this is the eternal question! (the one that comes just after "which telescope to buy?"). This tutorial will not venture to study the extent of the market ... but at random, a ZWO ASI224mc is a good start, so as not to invest too much

• a  second camera

No, this is not a joke! Well, a little. But it has a different use: while the main camera is busy taking our dear photos, this secondary camera, known as the guide camera, will make it possible, via software processing, to correct the movements of the telescope, to follow the sky even more precisely. , and therefore improve the quality of the photos. And we find our little 224 which is perfect for this job. But since you are not going to buy 2 identical cameras, at this stage you will want a more efficient camera, a perfect excuse to recycle the first one as a guide camera. Clever isn't it?

• a  laptop

You have to connect these cameras to something, run obscure software, adjust lots of sliders ...

and we can find even more things with more and more cables ... in short, we go far beyond the scope of this tutorial, let's get back to basics: we are only going to print another  secondary cage  dedicated to photography. The advantage is to  reduce the efforts  that the mount will have to make, by placing the camera in the axis of the tube.

We are going to recycle some parts already used before: the focuser is back in service, as well as the light shield which is identical and can be mounted on the 2 cages.

Print settings

• layer height: 0.2mm up to 35mm, then as thin as possible (for threading)
• Perimeters: 4
• Top and bottom layers: 10
• Supports: on the shelf only
• Infill : Gyroid 15%

There is only one M4 insert to place to hold the finder scope (or the guide camera), the part is mounted in place of the "visual" secondary. Do not forget the small cover which allows to close the opening for the visual.

Here is. It was simple, it would have been a shame to stop at the Mark II. But you have just put your finger in a gear that could take you far ... for your greatest pleasure!

A carrying bag from the standard French army backpack: it's cheap and incredibly strong!

We can find it at the discretion of arrivals in military surpluses and other Emmaus for a bite of bread, here is an example of a package bag for reference.

The pattern is relatively simple: cut the bag in 2 about 10-15cm from the bottom, sew a strip of scratch around it, and close the top of the bag by sewing the flap along the edges.

By lining the inside with a neoprene sheet (like a wetsuit), you will protect your telescope from shocks during transport.