> Deep-Sky Hunter Star Atlas
http://www.deepskywatch.com/deep-sky-hunter-atlas.html This is an amazing resource. Detailed atlas of all the sky with NGC and IC objects. All stars up to 10th magnitude. It is more detailed then any of the software available so far. I use it to plan observations and locate fainter objects.
You can print it and have it in your hands. Such an old school feeling! :)
If you have PC on hand during your observation, other good resources are the astronomical databases such as SIMBAD http://simbad.u-strasbg.fr/simbad/ but you need to be more specific in what you are looking for and it is therefore for higher level use.
Another good and more popular resources are Word Wide Telescope and Google Sky. For Mobile, I use SkyEye a very nice app but it shows stars up to 6th magnitude.
Here is one of my shots of M22 Globular cluster in Sagittarius and crop of the same filed from the atlas. Shot is taken in "Kara Tepe" one of the darkest sky in Europe with 200mm f5 telescope and single exposure of 30s and ISO 25600. The smallest dot is a 10th magnitude star. You can see that on the actual photo there is countless stars much weaker then 10th magnitude.
As this is a part of the Milky Way the most fainter stars dissipaters in the noise grain. As stated in the previous article the fainter star is much weaker then the limited magnitude of my 200mm telescope and will go even to 16 - 18+ magnitude.
I recently bought a pocket spectroscope for laboratory use. You can find it at Ali for 5$. It is with glass prism and well build. So I did some test to use with a telescope but did not
http://www.deepskywatch.com/deep-sky-hunter-atlas.html This is an amazing resource. Detailed atlas of all the sky with NGC and IC objects.
Reading a new product that claims to be 100x time more powerful then conventional telescope, I realise that this is just an astrograph with a digital camera that is doing stacked images and show them trought eyepiece or App.
I am so impressed with the K5 ability to quickly gather signal from nebulas (Quantum efficiency) and galaxies, so I decide to take one more K5 and to remove the IR-cut Filter of the old one.
Recently I got one very good lens the Asahi Takumar 135mm 1:2.5. This is fast telephoto lens and from my point of view a good lens should be with aperture from 1:1,2 to 1:2,8.