Focal Length

 

 

It's hard to know what focal lengths you know when you start Astrophotography, because frankly, you've never seen these dim objects in the sky before.

Here are a few of my images of deep sky objects, and the focal lengths I used:

This is my latest Andromeda image.  I still plan to work on this image some more.  But as a reference, this was shot on a Nikon D5300, with a 70-300mm Tamron lens, at 300mm, and because it's a crop sensor, it was an equivalent 450mm focal length.  This image is cropped vertically slightly, to fit a wide screen, but is the full width of the original image.  This was a stacked image with post processing.  Many people have shot Andromeda with a 135mm prime, or at 200mm and crop their images.

This was shot with the same D5300, and same Tamron 70-300mm lens, also at 300mm, or 450mm Equivalent.  This image has been cropped more significantly than Andromeda, as it is smaller in the sky than Andromeda.  People have shot Orion also with a 135, 200, 300, or even 600mm lens.  Going longer,  like to a 600mm lens, would be pretty sweet for Orion, though you would need a very good polar alignment so you could have a long enough exposure.

This is the Triangulum Galaxy.  Again, with the same D5300, same lens at 300mm, or 450mm Equivalent.  This is cropped a little.  This galaxy is a lot smaller than Andromeda, and smaller visually than Orion as well, and very dim.  Cropping any further down that I already did, makes this image look pretty pixelated.  More images would improve it (I took about 15 images, 2 minute exposures).  I think more focal length would definitely be better, but it can be done at 300mm, or 200mm if you have a better quality lens that will resolve the image sharper.

Here is Peleiadies.  Same D5300, same lens at 300mm, or 450mm equivalent.  This is cropped a bit as well.  The stars of Peleiadies are very bright in the sky, and can even be seen within city limits, if you city is smallish like mine.  It is a smaller target than Andromeda... but much... MUCH brighter.  Not Jupiter bright, but it's actually the very first target I found.  I was looking for Andromeda, and say this out of the corner of my eye.  I had to use constellations to find Andromeda, because it was too dim to the eye, but this I could see.  The stars in this star cluster are pretty easy to both find and image... but because this is a reflection nebula (the nebulous clouds to not emit any light, only reflect light from the nearby stars) the gases are much dimmer, and requires some effort to bring those details out.  I am still working on it :)

So that is all of my deep sky objects for now.  If some of you viewing this would like to submit a signed image, and include the camera and focal length you used, I would be happy to post them in here.

I also found this website that shows a variety of images, along with what focal length they were shot at:

https://www.pbase.com/samirkharusi/focal_lengths