Hi all, in another area of the forums I mentioned I was bulding an RC and got some interest. Rather then Hijack that thread I thought I would post here.
I am watching the F1 at the moment so I will just post a few pictures of where I am up to. I just got to the stage today where I cut the CF tubes to length and put it on the mount to have a look
A bit later on I will post a little history around the project and how I did it. No CNC, unfortunately, just by hand on my home workshop..
I am nearing first light and here it is trying out the mount.
I too am watching the F1... but will definitely be watching this thread... I look forward to more info about the project... It looks fantastic atop that paramount, although it looks somehow bigger than other 12.5" RC's I've seen photos of...
Great work, looks fantastic
Please do not mention the result of the F1 Grand Prix as us poor people who don't have fox sport or whatever have to wait till tonight to watch it
OK, so here is the compressed version of the build, to some pictures along the way, here are a few.
This build has given me many excuses to acquire things, the scope itself seems to be only the tip of the iceberg for what I have talked my wife in to
It was probably about august '07 when I was browsing and sw a guy in Italy had built a 12" RC. At that pont an RC just meant $$$ from RCOS and I wasn't aware that you could buy the optics to build your own. He bought his optics from a guy in Italy for a couple thousand euros. At that point I thought perhaps I could build one. I then found Paul Jones at star instruments supplying optics for a 12.5" RC for $2200USD from memory. I learnt that he supplied optics to RCOS and thought this was good enough for me. I bought them and it took ~four months for them to arrive.
It was at the end of december that I thought I had better start doing something abot the scope knowing that the mirrors would arrive soon..
Now, a couple of fortunate things happened in between. One was that I decided that my G11 was not going to carry a 12.5" RC for photography and I convinced my wife that I needed a paramount. This consumed a number of hours over a few weeks.
Once the paramount arrived it was clear that I cold not pull this thing out every night I wanted to use it. It was huge and even with a permanent pier that I planned to put in the yard it was not going to be practical. I decided I needed to build an observatory. I decided on a dome and how to build it. It became apparent that this was going to take considerable time to build using up all my weekends for some time.. I talked to my wife, again, thinking that maybe we should buy one rather then use up all my weekends when we had small children. Lucky for me, again, we agreed (sort of) and I had a sirius 3.5m automated dome shipping over. Some people have noted that my wife may be a push over
These are two benefits that seemed to happen all because of the 12.5" that I hadn't built yet..
So I went down to the workshop and started to prototype out of wood. I didnt want to waste expensive aluminium without a full size model. I have never built a cassegrain design before so I more or less copied the RCOS design. It had an advantage that I didnt need to do compound angles for the trusses, the disadvantage, not that I see it as one is that the center section is larger then any other section..
So, here are the initial pieces out of wood and the first pieces I machined, the connectors for the trusses. There was a reasonable amount of time consumed doing these..
OK, so the basic design looked ok. The big issue for me was how to design the mirror cell for a cassegrain. I knew it would be different from a db but I didnt know the best way to approach it..
After a bit of reading I decided on a cell that completely contained the mirror and made sure that the mirror was not supported at all by the center hole. This was mainly to prevent any distortion but apparently n case of disaster it lessens the risk of breakage in a fall.
This type of cell was going to cost a fortune if I machined it from solid. So was buying over 30mm thick plate to do the other pieces. I decided to make patterns and have them cast. I found a guy about 5 minutes away that charges $22 per kilo. This included the aluminium and having the casting T6 heat treated. This was the way to go for sure so I made four patterns to be cast - the mirror cell, the backplate, mid section and ring for the spider. I can't remember the cost but it was a fraction of the price if I had bought plate.. It machined very well which was nice.
They all went on the lathe to clean up the casting and get them to size. The backplate and center section then went on the mill to square up the sections that I would be joining. All went fairly well here..
At this point something happened, or rather nothing happened. I got sidetracked and didn't do any work on it for over a year, didn't touch it at all..
I had a WO FLT 110 and WO megrez 90 on my mount and sold them to get a fsq 106. That satisfied me for a while but widefield started to get old and I was itching to get in to galaxies and other smaller objects.
This got me motivated to get back in to the build. One thing to note was that a friend of mine bought the same optics as me after hearing about them. He doesn't' have a workshop but did have a friend in china who runs a machine shop. He also doesn't have a paramount so he was going to go for a lightweight carbon fiber tube. He sent me his design and I found that the spider he designed would suit my scope as well. Given the cost to have it done in china it didn't seem sensible to do it myself when I had to buy the material. I got him to do two of them and this arrived a couple months before I resumed the project..
At this pot I had to finish the cell, machine the cell/baffold support and make the baffles. I nice guy, Mike Jones, a professional optician designed the conical baffles for my specific optics.. More pics of this part below.. One is of the form for the primary baffle, a couple of machining the baffold/cell support, the cell triangles unfinished and the collimation bolts. I decided to mill a sphere in the end and glue steel balls. It makes the collimation smoother.
Now we are up to date until about a week ago.. I guy I know took my forms and did the CF baffles for me. He does it for a living and saved me doing my first attempt.. I must try it myself though as I am sure once I use it once I will find many uses for it.
I then had to attach the baffold to the scope.. I machined a ring that sits at the front of the baffold support and has 6 bolts to hold and allow collimation of the baffold.. You can see from the picture that I also milled out the side of the mirror cell. This it to aid airflow from the fans around the mirror.
I also machined an adaptor on the backplate which mates to the FLI PDF focuser.
At this point I had the dovetail I had made and a basic rail for the top. I needed two more for the sides. I decided to re-use a dovetail rail that I got with my FSQ. I would adapt this to be the top rail on the scope and it would also allow me to mount the FSQ on top without any additional machining.
So now I only needed to do two more rails. I did these yesterday and today I drilled and tapped to fit them on the backplate/center section. this was the first time I had tried to remove excess weight so they too a lot longer then usual.
I will go back and remove excess weight from the major components next week as the weather tells me there is no need to put the optics in just yet.
I also milled out pockets from the main dovetail rail. That takes me to today where I cut the CF tubes to length and put it on the mount for a bit of fun!
This really is the whirlwind tour of the build but it gives you an idea of what I have done. It skimps on all the problems and decisions I had to make along the way. just hope the scope works It is certainly costing me a fraction of the amount if I had bought it from a known supplier - excluding GSO that is.
Very cool Jason. Sadly, some of us can't follow your steps as we don't have the technical knowledge or ability of machining. Pity, cos I'd give it a bash if I did.
Mate, that is awesome!
Nice workshop too... mill with DRO and a decent lathe... is that a 12" chuck? makes my lathe look like a toy(it kinda is... 7" swing, 4" chuck, chinese)
Very very nice work.
Yes David, that can be a hurdle, although I would say that unlike a mount where you may machine bearing houses or do interference fits there are no such difficulties with this scope.
while you need things to be square and concentric, which the lathe and the mill will do for you there is nothing particularly demanding about the project - other than time!
Alex, you mentioned that the scope looked big for a 12.5" . It is 910mm long from the rear of the backplate to the front of the upper ring. This doenst include the adaptors mounted to the backplate.
It is probably a bit wider then the average 12.5". This is because I thought if I went bigger I might want to just replace the optics and keep the OTA so I thought about making something which I could swap out the mirror cell with one for a 14". So it's ~410mm across, that about 45mm each side larger then the mirror.
It was only a half hearted attempt that I didnt reaaly take to seriously. It's probably too small to fit a 14" but not much larger then required for a 12.5"
I think some of the problem if the distortion that the wide angle gives when you are close up. Even though the mount is very close to the scope it looks smaller with that lens.
Mate, that is awesome!
Nice workshop too... mill with DRO and a decent lathe... is that a 12" chuck? makes my lathe look like a toy(it kinda is... 7" swing, 4" chuck, chinese)
Very very nice work.
Thanks Simon! Not sure of the size of the chuck. The lathe is a 16" 7.5hp, it's a beast to have at home, I am happy about that! I had to take the gap out to swing the center section as it is over 1/2M from corner to corner!
Both the mill and the lathe have DRO attached. I couldnt live without it.
Jason
Very cool indeed Jason... Impressive looking to boot..
I was wondering, if you don't mind my asking, roughly what did it cost for materials and optics.. obviously you can't put a price on your own time and effort.. just wondering what it would cost to buy the optics and the materials required... Last time I enquired at Star Instruments, the 10" F/7.5 RC optics cost around about $2800 AUD.. I would imagine the overall build of your scope (once you've fitted the FLI PDF to it, fans and the like) to be in the ball park of $5500~$6000 + your time, effort and skill.. That would still be incredibly cheap for a 12.5" RC imaging system. Just a shame the mount to carry it is so expensive..
Hello Alex, it's not something I have really kept track of. The optics cost me $2200 USD for the F6.7 RC. Another few hundred USD to get them coated in the US with enhanced coatings and an protective overcoat.
The costs locally were ~ 270NZD for the CF trusses to be made, around 400-500 NZD for the castings including making the patterns.. perhaps another $450 for other aluminium, I.e. machining the baffle support, rear adaptor, dovetail , siderails etc.. If I was to make the spider myself then add another $180nzd in materials. Other then that its just nuts, bolts, fans etc. probably another $150-200in misc pieces..
f I take the high end of my estimate and the USD was ~80c when i got the mirror then it cost me ~ 4800 nzd, round it to 5k. In aussie $$ thats $4140 with todays exchange rate..
Not too bad for what I am getting.. oops, add another $150 to create the forms and do the CF baffles..
Yeah the PDF adds another grand or so AUD to the total... Clearly you could do it with something like a feather touch.. but why would you.. a scope like this deserves a top of the line focuser... either the FLI PDF or the TCF-S...
It is certainly costing me a fraction of the amount if I had bought it from a known supplier - excluding GSO that is.
