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Re: I believe it's usually more common in 4WD cars etc Yes! But you will have to pay. Cheap Chinese rubbish, in most cases, will not fit the bill!! The unit above looks excellent. Jeremy.

How does radiation heat a gas?
JRWASTRO replied to billyharris72's topic in Physics, Space Science and Theories
Greetings Billy, You have raised many questions that only a course in physics will help answer. I could offer a few buzz words to aid in your research. 1. Re: thermal energy and black body radiation. Thermal radiation is exactly that  radiation one can feel as heat, from a bar radiator for example. This energy will be in the vicinity of 8 to 14 micrometers (human body temperatures) and 3 to 5 micrometers in the case of Jet engine exhausts. Buzz words : See StephanBoltzmann law and look up Ultra violet catastrophe  See Wein's displacement law. 2. A Black Body can and will emit "Thermal Radiation" depending on its temperature. BTW. Black bodies are not black as such they can be dull red (hot) or white hot or extremely cold (above absolute zero). 3. About Buzzword : Look up Entropy and the work of Ludwig Boltzmann 4. You should study about the dual nature of radiation  waves and particles. The waves will be electromagnetic waves  orthogonal electric and magnetic fields  look up "Poynting Vector" Good luck in your research, Jeremy 
JRWASTRO started following Scope Handles... 'Andles for Scopes! :D and Charging AGM battery from car

Hiya Msacco, Here is a very robust unit : https://www.redarc.com.au/smartstartbcdc This will suite your 75Ah deep cycle battery. Jeremy

Re: send commands to my mount via Matlab without passing trough a Synscan controller but I'm not sure if it is doable. Brave man! You can do anything with MATLAB and Simulink ( https://au.mathworks.com/products/simulink.html ) How much cash have you got ? These mathworks chaps charge like a "wounded bull" ! Have you seen the open source approximation to MATLAB called OCTAVE ? Jeremy.

I have a 10" dob like the one you have and place a 20 Ah battery as close to the centre as is possible. The OTA just misses the battery. As they say " a miss is as good as a mile". This arrangement works well but I am looking for a "cheap" lithium battery of 20Ah but, so far, I have been unsuccessful. Hope this helps. Jeremy.

Greetings Brodie, Re: B " In space, the angular resolution of the Keck telescope is govererned by the diffraction limit. " Really ? Where did you read this ? About diffraction limited optics, These books have definitions of what it means when an optic is diffraction limited: 1. Introduction to Fourier Optics by Joseph W. Goodman See p. 129 " An imaging system is said to be diffraction limited if ..... " 2. Aberration Theory Made Simple. (SPIE PRESS Tutorial Text) by Virendra N. Mahajan See p. 79 " The aberrationfree image of an object is also called its diffractionlimited image .... " 3. Basic Optics for the Astronomical Sciences (SPIE PRESS) James B. Breckinridge P. 227 10.2.2 Highangularresolution astronomy: stelar diameters. BTW : Nice picture of the Keck Telescopes on the front cover. 4. Diffraction, Fourier Optics and Imaging Oran K. Ersoy p.142 " An optical system is diffraction limited if ... " Ersoy, here, refers to Goodman (ref # 1 above). I have other books but the above references will help you answer your question. Jeremy

Frustrating astronomy ?
JRWASTRO replied to Fieldsy's topic in Getting Started General Help and Advice
nil desperandum . This is the cure all in two parts : 1. According to Douglas Adams, I quote " 85% of all known worlds in the Galaxy, be they primitive or highly advanced, have invented a drink called jynnan tonnyx, or geeN'NT'Nix, or jinondonicks, or any one of a thousand or more variations on the same phonetic theme. The drinks themselves are not the same, and vary between the Sivolvian 'chinanto/mnigs' which is ordinary water served at slightly above room temperature, and the Gagrakackan 'tzjinanthonyks' which kill cows at a hundred paces " 2. https://www.craftginclub.co.uk/joinfreeginspecial?om_campaign=omme_de8a9efcb34_1816_3101&om_send=72c0b67ce098420495697aefbc72fcf8&utm_campaign=omme_de8a9efcb34_non_members_free_gin_170519&utm_content=freegin170519&utm_medium=email&utm_source=ometria Jeremy. 
Two points: Point 1. OK with equation 78 when A and B are the sides of a right angle triangle. B is the hypotenuse. If A/B > 0 then the angle theta tends to 90 degrees. Cos(90) = 0 and Sin(90) = 1 (angle in degrees) Seems to be a mixup here, perhaps what was meant: Lim ((sin(a)) ) / a > 1 a > 0 It is written like this because as the angle a=0, sin(a) = 0 and the division 0/0 is meaningless. When the angle is tends to 0 radians then a = sin(a). If A/B = sin(a) when a > 0 then we can say the angle a in radians is a = A/B Point 2. One does not need to go through the above reasoning if one uses the definition that on a circle (radius r) the length of the arc (S) is S = r * a where a is the subtended angle at the centre of the circle. For very small angles the arc and chord may be taken to be of the same length. Distance to the star may be calculated from: r = S/a. Angle a may be measured by the large land based telescopes. I see no problems here. Re: You can measure the position of the star ie the centroid of the star image to much greater precision than the resolution. Yes of course. Good point. Jeremy

Greetings Observers, Here is a link telling us about Jupiter being in opposition. It will be very bright and large : https://inthesky.org/news.php?id=20190610_12_100 Hope the weather is excellent on the 10June19. Jeremy.

Scope Handles... 'Andles for Scopes! :D
JRWASTRO replied to Macavity's topic in Discussions  Scopes / Whole setups
Typical Vixen. Excellent quality. Jeremy. 
Re: is the optimal sublength for a particular telescope, camera and SQM combination ... all condensed from this article. That said, there are some on here who disagree with the specifics. For a bit of discussion, see this thread. Wonderful. I will read "this article" slowly and in detail. Why? Because Quote: σe=newhere ne is the number of electrons collected by the pixel and σe is the standard deviation of the number of electrons expected between pixels all exposed to the same light intensity. End quote. Here he alludes to Poisson distribution. This article deserves reading. Thanks. Jeremy Addition: Just read the article and it is excellent. Beautifully explained. I have taken note! JRW

Scope Handles... 'Andles for Scopes! :D
JRWASTRO replied to Macavity's topic in Discussions  Scopes / Whole setups
Re: Scope handles are a very useful feature usually omitted by the manufacturers on budget scope designs. So True, Geoff. One of my telescopes has a built in handle. The finder 'scope doubles as a carry handle and is placed so that there is almost "prefect balance : Re: Hmm perhaps one of these could be adapted. Looks like a pretty, if not expensive, engine crane. I have one of these in my shed but it is all manual. Jeremy. 
Re: " But it doesn't rhyme. " OK. But you've got to admit my attempt is not too bad. Alright I've taken the bait. What are those formulae, in your signature, all about? Jeremy.

RE: ... Shouldn't that be sine theta over sine phi  angle of incidence and angle of refraction? I think theta has a nice ring to it. Poetic licence allowed us to remove the subscripts!! Naming angles? Take your pick. The two angles may be (theta1 and theta2) or (theta_i and theta_r) or (phi1 and phi2) For me Theta and phi have always been associated with angles eg. polar coordinates ... (r,theta, phi). A sine wave: sin(omega * t +phi) , we could write theta = (omega * t + phi) . How's That ? Jeremy.

There was a caveman named Snell He was really the spear fisherman from hell He could tell by the bend of the spears end It was sine theta over sine theta well, well ! My best attempt at doggerel, Jeremy.