planetman83

Guys, I am having second thoughts about the 3D printed secondary holder. I am afraid of its stability and rigidity. I will glue the 5.3" secondary mirror to a 12mm birch plywood with silicone and then I attach it with screws to a piece o aluminum. The mirror will touch only to the plywood, will it be ok like this? 1) Will I have astigmatism? 2) Is there any chance the mirror will detach and fall from the silicone?

The 1 1/8" star nut is too small for the 28mm inside dimeter tube! It just goes in and gets out from the other side.

Yes, there is a friend of mine that is experienced helping me out. I have a question: I just tried a 1 1/8" star nut to a 28mm inside diameter carbon fiber tube and the star nut is too small. I though these star nuts are for 28mm tubes. Am I wrong? How can I use them to a 28mm inside tube?

The truth is that I am rebuilding a used 24.4" telescope making it smaller and lighter. The builder of the previous one just told me that he took into consideration all these factors and that the dimension of the ring is the correct one.

I did not know about this to tell you the truth. Is it so serious? I am 636 to 620 only. They are feet for small furniture, something like this.

The mirror is 620mm and the inside diameter of the upper cage is 636mm.

This was my goal, to make the mirror box and upper cage as small as possible in order to fit easier in the car. They are 28cm each. The truss tubes will be carbon fiber so they are stiff holding them together.

I assembled the mirror box today. I used glue for birch plywood and over 30 wood screws.

How thick are your bearings?

mapstar, I have seen your built, it is world class, congratulations! And you holder made of carbon fiber is what I would like to do but I cannot work this material and it is very expensive to find someone to build something like this. I attach some new photos. The CNC cutter finished the 1st batch, mirror box and upper cage wood. I don't like the 24 number. maybe I will make it again with laser.

What do you mean standard? The truth is that I am rebuilding a used 24.4" telescope that is too big for my taste. The mirror cell and the mirrors are the only things that are going to stay the same. So the mirror cell is like the one in the sketches. 18 point made of stainless steel. I will upload photos tomorrow.

The tube assembly is going to be something like the following sketches. I cannot attach the truss tubes on the upper cage in solidworks. I have added the weight of everything I will use on the upper cage. The bearings' diameter are 1.4x the mirror diameter's and you can see that the center of mass is a little lower than the bearings. So I think I go around 1.3-1.5x at the final design. I am not designing a classic design. My design will be lighter, with as light upper cage as possible, carbon trusses etc. This is why I don't follow the old classic recipe. For the alt and az movement I will not use ebony star and teflon, but teflon, ball bearings and insted of ebony star I will use thin steel.

Guys, what is your recommendation about the thickness of the bearings and the rocker box? I am thinking 27mm for the bearings and 24mm for the rocker, sides and bottom.

I have read that if the opposite vanes are parallel and 90 degrees with the other 2 vanes, then the spikes are single and just a cross. I own a 16" with the same design and the spikes are just a cross.

Jim, here are some more detailed photos of the spider. I need to paint it again. The spider vanes are not 4 pieces but only 2. I printed the holder again with PETG and with an improved design. I am now waiting for the cnc cutter to finish the upper cage and mirror box wood parts.

I think that the main reason is that you can easily cut and edit wood. Who can do the same with carbon fiber? Birch plywood is also very light and durable. It is also very well looking, like a furniture. Many dobsonian telescopes are made of aluminum but it is not for everyone who wants to build his own scope. You need the right tools to bend it, glue it each other etc.

Hello, my name is Manos Tsikalas. A few days ago, it came to my hands a 24.4" f/3.2 primary mirror and a 5.3" secondary, made by John Nichol optical , so my duty is to make a very beautiful, functional and well made truss dobsonian telescope. My friend Dimitris Manousos designed a very clever sketch of a secondary holder that we already printed. They are 2 parts that hold the secondary together like a sandwich. It is a little larger than the secondary in every dimension so it does not deforms it. I personally made the spider and the system that aligns the secondary. I made the spider vanes at 80mm offset to each other. At this geometry the spider vanes are mostly loaded in tension when you try to rotate the holder. A very important thing here is for the height of the upper cage to be as small as possible. I have calculated that it will be 28cm total. I am going to use carbon fiber truss poles for the trusses and for the struts of the upper cage. Using carbon fiber stiffens the construction and the weight stays low. I will kydex or 2mm birch plywood inside the cage also. The goal for the upper cage is to be no more than 6-6.5kg, moonlite 2 speed focuser included. The height of the mirror box is going to be also 28cm total. I made a draft sketch of the upper cage and of the mirror box. I haven't decided yet about the truss connections to the mirror box and to the upper cage. There are many solutions, but I am trying to find the best, easier and more durable. Do you have any recommendations?

So, did you use the scope for astrophotography? Please share your impressions.

Did we finally learn if the dovetail is included?

This is something I don't know how to read and understand. First time I hear about it. What is your outcome?

The truth is that I am not new to imaging. I have changed many setup the last 13 years. I observe using a 16" f/4.5. I collimate with the tublug and 2" laser tools, so collimation will not be a problem. I know that the f/4 's length is smaller and the focal length is smaller so more frames will be good compared to f/5. The biggest problem for me is how well the corrector will work on f/4 compared to f/5.

If I choose the f/4 over the f/5, the advantages are that with smaller focal length, most frames will be good, the frames will be brighter but the disadvantage is that the stars will be worse at the corners, right?

I could try IF I ALREADY HAD the setup. That's why I' m asking before buying. Anyway. What about the corrector? Which one will work best?

Thank you very much for your help. So yes, the full frame sensor helps a lot with noise. So if I accept that I will crop and keep let's say the 60-70% of the length of the image, is going to be good enough then?

Hello guys, I am thinking of buying the ts photon 6" f/5 in order to do astrophotography with my canon 6D (full frame). I don't want to autoguide. I think that 40-50sec frames will be enough with ISO6400. I want to ask: 1) Will a skywatcher eq5 Pro is capable of driving this setup? 2) I know that there will be coma. Is this coma corrector going to fix my field well enough ? https://www.teleskop-express.de/shop/product_info.php/info/p6706_TS-Optics-NEWTON-Coma-Corrector-1-0x-GPU-Superflat---4-element---2--connection.html Where can I see a photo sample with this setup and a full frame camera?