Looking at the sky

Yes, that is snow on the ground.

I think I may have figured out how to use the EQ3 Synscan thingie. My telescope now finds stars for me. I no longer have to find them myself.

Size matters

Some calculations will seem very intimidating at first. They won't bite.

Telescope

\[\text{Diameter of mirror, }D_1 = 150 mm\] \[\text{Focal length of mirror, }f_1 = 750 mm\] \[\text{Focal length of eyepiece, }f_2 = 28 mm\] \[\text{Resulting magnification}\frac{f_1}{f_2}=\frac{750}{28}\approx{27}\] \[\text{f-number, }N = \frac{f_1}{D_1}=\frac{150}{750}=5\]

Next up is a concept I don't fully understand. Macimum theoretical resolution of a telescope. Capability to see small details. This is apparently a function of telescope diameter and light wavelength. At least in theory. Stuff like aberrations and seeing come in the way, but there is a maximum theoretical resolution. For visual light we get

\[\alpha = \frac{140}{D_1} = \frac{140}{150} \approx 0.93 \text{ arcseconds}\]

So, I won't be able to distinguish details smaller than about 1 arcsecond. For reference, the moon is about 30 arcminutes.

Camera

The telescope is interesting in itself. Let's see what happens if we attach a camera to the telescope. First we figure out the plate scale measured in arc seconds per mm.

\[\text{Width } 3888 \text{ px}; 22,2 \text{mm}\] \[\text{Heigth } 2592 \text{ px}; 14,8 \text{mm}\]

\[\text{Plate scale } = \frac{206 265}{f_1} = \frac{206 265}{750} \approx 275 \text{ arc seconds per mm}\]

Sooo... images I take with my camera will be roughly 1,7 by 1,1 arch degrees.  The moons diameter is roughly half an arch degree. This seems to be in line with my first experimental photos. Waiting for the moon to come up so veryify this. Moon, where are you?

What about resolution?

\[ 1,7 \text{ arc degree divided by } 3888 \text{ pixels gives roughly 2292 pixels per arch degree}\] \[\text{or } 0,63 \text{ pixels per arch second}\]
Seems the camera resolution is comparable to the telescopes theoretical maximum resolution. Cool.

Sky image 4

Look at me! I have four moons. You only have one.

Jupiter, with moons Ganymede, Io, Europa and Callisto.

Finally got the motor on the polar axis running. Just a few more kgs to carry around.

ISO 100, 30s exposure.

Yes, that's right! 30s exposure with no trails!

Unfortunately we had some clouds come in over our sky just as we were getting everything set up. The halo is hopefully a cloud, not an aberration in the scope.

#astronomy #jupiter #telescope

Sky image 3

The Pleiades - gotta catch 'em all!

The Pleiades, M45. Thought to be some 400 light years away.

I do like their names. Alcyone, Celaeno, Electra, Atlas, Merope, Asterope I & II, Taygeta, Maia, and Pleione.

ISO 1600, 1/2s

Can't take longer exposures currently. Haven't hooked up my battery to the motor that rotates the telescope.

#astronomy #pleiades #canon #skywatcher #astrophotography

Sky Image 2

I am the Andromeda galaxy. I can see your house from here.

Andromeda galaxy, M31.
Believed to be 2.5 million light years away.

ISO 1600, 8s exposure

Can't take longer exposures currently. Haven't hooked up my battery to the motor that rotates the telescope.

#astronomy #galaxy #telescope #canon #andromeda #astrophotography #skywatcher

Sky Image 1

I am jupiter. I bid you to sacrifice a white castrated bull in my name.

Jupiter with its moons Callisto, Europa and Ganymede.

ISO 800, 2s exposure.

Can't take longer exposures currently. Haven't hooked up my battery to the motor that rotates the telescope.

Using Canon 400D Digital Rebel XTi for astrophotography

When shopping for a telescope one of the first questions that came to my mind was how to attach the camera to the telescope. Do I duct tape the camera to the eyepiece? Turns out the answer is no and that there is a fairly accepted standard way to do this. Most telescopes seem to have a standardized eyepiece socket. All I had to do was to get something called a T2 ring compatible with my camera and hook it up. See wikipedia http://en.wikipedia.org/wiki/T-mount

Apparently this does not always work. Since the CCD is so far back in the camera it will never come into focus. I was lucky enough to buy a telescope of the Skywatcher brand. They apparently have a clever eyepiece socket that allows me to shorten the distance between the camera and the secondary mirror getting the CCD into focus.

Hello, I am a street lamp

I took a first picture of a street lamp outside my apartment on my first attempt to hook things up. I'm not sure why it's so blurred. I've got three theories:

• There are several layers of glass windows between the telescope and the street lamp. I live in northern Sweden, remember? My windows have got three layers of glass and the shot is out through the balcony window. I have an extra layer of windows there. So four layers of glass.
• The rig was shaking. I used my hand to press the trigger on the camera. 
• Camera was simply not in focus. It's kind of hard to see through the small viewfinder in the camera.

I think the solution to the latter two problems is to hook my camera up to a computer and use it to take shots. More about that in a later post. I think the solution to the first problem is to go outside. More about that in later posts too.