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8

You may know that a standard Newtonian telescope has two mirrors, they are called the primary and secondary mirror. The E-ELT has five mirrors: The quaternary mirror is simply "mirror number four", counting in the direction the light enters the scope. It's complex because that's where the adaptive optics sits: The quaternary mirror has an approximate ...


2

If a planet is 1000 light years away, there is no way that we could be sure that there is life on it "now". However there is a probabilistic argument: Life takes many millions of years to develop, and the chance of a disaster being so great as to sterilise a planet is very small: case in point, the Earth hasn't been sterilised since the last common ancestor ...


2

If you search for "vixen/synta mounts" you should find lots of compatible mounts and tripods. There is a huge range of prices and level of features. Check out what the specifications say about their load capacity, relative to the weight of your scope.


0

All telescope mounts are calibrated with several known target objects, but to initially line up with said objects it is possible to use eyeballing and then moving the radio-telescope around until reaching a peak value from instruments, which would indicate you are pointing directly at the object. I'm not sure how the professional observatories manage it, but ...


0

I generally agree with the answer above, but have a couple more insights which might help you if you decide to proceed with trying to make your own scope... The lens pairs that James mentioned (crown and flint) are known as a doublet. Glass has two key properties in play here - its index of refraction (how much it bends light) and its dispersion (how much ...


1

You would be better off using lens 5 and 3. Though don't expect much, a simple single lens for the objective and for the eyepiece will give a lot of chromatic aberration (false colour). Refracting telescopes usually use at least two lens of different glass types (crown & flint often in a doublet) and eyepieces usually have 4+ lens. You should be able to ...


3

A high end photographic tripod would probably work but it will be difficult to make small tracking adjustments. So a proper astronomical mount would be much better. An EQ2 mount would just about manage a scope of that size however an EQ3-2 would be a lot more stable and have the advantage that you can either get a goto version initially or upgrade at a ...


0

I think you may be looking at the wrong date? -21.9964 is the first value in the current bulletin B but that is for 3/2/2016. The current bulletin B only seems to go up to 5/1/2016, with -134.3179 as the value. I think you may instead want bulletin A, which shows -0.154825s for today (5/12/2016)? http://maia.usno.navy.mil/ser7/ser7.dat


2

In addition to the diffraction issues pointed out by Conrad Turner, a Fresnel lens would suffer from all the other problems that large lenses in telescopes suffer from: Chromatic aberration Differential sagging under its own weight ("differential" because how it sags will vary depending on how the telescope is pointed) Thermal expansion and contraction The ...


2

A group at LLNL have worked on it with DARPA funding. They had a folding glass system called Eyeglass in 2003 and a flexible membrane system called MOIRE in 2013. They embraced the diffraction and put it to work, totally unlike refractive optics as we know them.


4

The main advantage of a Fresnel lens is its reduced mass compared to a normal lens. Its disadvantages include difficulty of manufacture and diffraction from the discontinuities in the aperture, these I suspect are killers given the practicality of the alternatives, reflecting telescopes, to a Fresnel lens refactor. Diffraction will give reduced contrast in ...


0

Do you have a star chart to allow you to star hop from a known star to smaller stars to your target? Most messier objects are not naked eye visible and with the small field of view of a telescope, unless you know where to look, you're not likely to find something by blindly hunting around. You also need dark skies, as most DSOs are small and dim.


1

In principle a fiberscope eyepiece could work but not very well. By putting one end of the cable flush with the field stop of an eyepiece (few allow this) and the other end exactly in the telescope's focal plane, you'd get a fiber-pixelated image. A binoviewer would require two cables, difficult to align.


7

The competition for permanent positions in astronomy is very tough. The field as a whole produces roughly ~200 Ph.Ds per year, but there are usually only a handful (say ~10) tenure-track positions that open up every year. So perhaps ~5% of Ph.Ds end up in tenure-track positions in astronomy. There are more permanent positions in astronomy that aren't ...



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