Stefanosky

[Stefanosky]

Very well, I will see the point where the theoretical center of gravity will mark me and I will try to size the crescents. So now I'm designing the various parts and I've already bought the steel for the cell (which I will build first) so as to check if the weights correspond to those calculated by the software.
I'll update you on the matter soon

[Stefanosky]

Thanks Giulio, maybe i found a solution a little bit “advanced” which if I could master it would be a masterpiece. I use a software called Solidworks for 3d prototyping which I found to have a function (among the thousand thousand) very interesting, created all components in 3d (mirror, cell, box, cage, secondary, spider, seeker, etc) and assign him the materials (consequently the weights) the assembly is then assembled as if it were the finished telescope. At that point, the function is launched that calculates the center of mass of the whole and should return the exact fulcrum. Then eventually changing the box you would have in real time the variation of the center of mass. Found that, it is still not clear to me how to calculate the radius of the crescents

[Stefanosky]

Hi everyone, I started the journey again! I'm designing the structure, once completed I will return to take care of the mirror. In the end I opted for a traditional structure, non light, that I will make in birch wood.
At the moment I have designed cell a 18 points and the relative steel structure that will be positioned inside the box. (I put a printed sheet on the fly with two handwritten notes just to make people understand)

I have practically all the measures I need, sizing of the secondary, of his cage, indicative length of pipes etc..
The question I ask myself is this, not knowing in advance the weights of the various components and their distribution along the axis, how I calculate the height of the box to stay within a range that allows me not to have any nasty balancing surprises in creating adequate crescents?
I followed documents that explain how to have an indicative balance a priori but they assume all the weights involved are known, of all the materials used etc.. There is a more approximate method for dimensioning the height of the box?

[Stefanosky]

Having these days of problems using Cad on my PC I tried to Use clean Atmos for the design of measures.
I entered the same data, mirror 300, focus 1800, cpl 20, distance from the optical axis 249 mm (Data from within 318 mm of the 90mm Inner Case foc) but I get different values.
Negligible with regard to the size of the secondary but almost halved as regards the offset. How is it possible?

[Stefanosky]

Bah, experienced or not your luggage for people like me is pure gold…
Speaking of the focuser, of which models could direct me? So out of hand I would prefer a crayford. Those low profile ingolosiscono me for the possibility of a smaller secondary, minor obstruction and lower weight, But I'm afraid that the blanket is short with certain ocular or other accessories.
Of those “normal” I saw some models but I think they have a height less than that indicated by you of 90 mm (the data to be taken for the calculations is that its just the minimum height?). Then there is the choice of the available travel, some 40mm, 35mm, other 15mm and so forth.
What do you think of this? I've seen more serious stuff like Feather Touch but have very high prices.
https://www.baader-planetarium.com/en/accessories/telescope-accessories/focusers/2%22-bds-nt-baader-diamond-steeltrack.html
Pair this with a Baader Zoom 8-24 Mark IV (that I read a lot of good). It might be a good choice?

[Stefanosky]

All clear! I'll get right to work and when I understand the situation I'll open a thread on the design of what will be (let's hope) my first homebuilt tool

[Stefanosky]

What about Julius, a show… Thank you!
So starting from the desired cpl are pulled out all sizes,. For example, if I was interested doing photography with my camera which has a 22.3 sensor×14,9 mm should calcolarmi the diagonals doing square root of (According to the second more height to the second) and I would get 26,81 mm cpl would be the need to cover the sensor (In this case, the calculations should also take into account the sensor away from the focuser to be added to 90mm). Since I would start them with the other calculations, am I right?
Taking into account that it is not my primary interest to take pictures I would say that a cpl 20 mm would allow me a little all options including any pictures maybe croppando in post production.
For curiosity, leaving out the photographic part and then choosing a cpl 10 mm, in the face of minor obstruction which would have disadvantages regarding the eyepieces used?

[Stefanosky]

All the time you need Giulio! There is no rush
Now that I still think I would not go to increase the obstruction to the habit to attack an SLR for which Dobson is not the right tool. It should then also calculated the offset of the secondary real? Oh well, see if you can figure out farmici then something will adapt to the concepts needed

[Stefanosky]

Giulio I then decided to wood as you consigliatomi, allow me more generous machining tolerances and any changes or additions in the course of work but on occasions there was a need.
Now I need to figure out how to calculate the size of the secondary cash and obviously this dimension.
I currently do not will opt for a low riding so we say that will be a configuration “academic” but having not yet focusers and eye I have difficulty using the different formulas.
You advise me to be an effective method to decide:
-inner diameter of the secondary cage
-axis diameter smaller secondary mirror
doing so precisely to use a secondary “quite right” in a cage “right” which allows me to use a low profile focuser maybe able to exploit most of the eyepieces (I plan to take such a great zoom 8-24) and having to need a full field light enough to use my camera for some shots “on the fly” (sporadic use and limited by the nature of a dobson).
Thank you

Edit: I remind you that we start from a 300mm f6

[Stefanosky]

There are several plugins wp who make “search and replace”, just give it as search postimg.cc and as replace postimg.cc and it should do all the work automatically.
https://it.wordpress.org/plugins/search/Search+and+replace/

[Stefanosky]

Damn all the photos posted via postimg.cc have been deleted
I hope to save them outside the HD.
Edit: I have now discovered that the posts should be modified by changing the link of the photos by replacing postimg.cc with postimg.cc but it doesn't let me edit them because it's been too long

[Stefanosky]

Thanks Giulio, You are my comfort
The problem is that I have nothing with which to test the glass… nor do anything eye structure. I could start to create the structure as if I had already finished the mirror so with the excuse to try to finish it in the best I already find myself with a telescope finished once the parabolizzazione and subsequent aluminizing, so now focal and company should not vary significantly. After I continue with rhonchi the best that I can and maybe I will find the strength to throw myself in foucault
What do you think about it? A greeting!

P.S. Also because now the temperatures would be too high to work best with pitch.

[Stefanosky]

hello Giulio, I am firm, seem strange but the tester for foucault I could not build it Modine, I lost too much time with the one printed in 3d, then I could not put a room for post test and I got the despair. I was thinking about you a few weeks ago as I watched my glass… I miss being blessed parabolizzazione but being a perfectionist damn if they are not in the best condition of doing things rather not do.
Help me!

[Stefanosky]

Well in fact I could avvicinarmici a little eye and then go directly to foucault them and that you will help me Giulio!!!

[Stefanosky]

Is’ hard restart after a break! I have to redo a mental. I read the discussion in the last pages and therefore are firm to the point where I need to print me one or more reference images ron Ronwin2.0.

Virtually imposed in options mm instead of inches, I put diameter 300, focus 1806, 4.92 lines per mm should match 125 lpi which is the pattern that use, the offset is the distance in positive or negative from the correct focal point? Can I put a couple of arbitration values, or should some specific distance?
Once I printed the reflected images as I should compare them? Sorry for the questions but after two or three months I was rusty and I lost my train of thought

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