Archive for the ‘Astrophotography’ Category

My First Astrophotography Pictures

August 29, 2009

Astrophotography is a complex and expensive hobby. But nothing can stop you from getting some decent results from your backyard. Of course it’s nothing like Hubble beauty you see in Internet, but because you got those pictures yourself they have a special meaning to you.

Let’s say you got your first astrophotography telescope, how to get your first pictures? The simplest and fastest way is this one:

1. Use Stellarium to find the object you want to take picture of. At the time of observation it should be high in the sky (the higher the better, if it’s above 45 degrees it’s considered good already :-) Object should be bright, magnitude ~7 or less is fine, and large enough 10 arcminutes or larger. Messier objects usually fit well for this description.

2. Setup your telescope, hook up camera to telescope and do a 3 star alignment. Don’t bother with drift alignment for now. You probably can not shoot pictures with longer than 30 seconds exposure anyways.

3. Pick a bright star near the object and focus your telescope with bahtinov mask.

4. Go to object and center it, you can shoot picture with maximum ISO setting on your camera, usually you will be able to see the object from one photo in this case.

5. Don’t forget to set your camera to RAW format, you can use any ISO setting, ISO 800 or 1600 isually most common used, but it does not really matter, ISO 100 works just as good, because ISO setting does not change actual sensitivity of the sensor. If you caught photon from distant star you caught it no matter what your ISO setting is.

6. Shoot as many object pictures as you can, without connecting your camera to computer you probably will be limited to 30 second exposure time. These pictures are called lights.

7. After an hour or so — check your focus on a bright star again.

8. After you have a desired amount of lights (the more — the better), put a lens cup on your telescope and shoot some dark pictures (10-20 is enough).

9. Use Deep Sky Stacker software to stack your lights and darks. This is the simplest free one I found, you just open your files and click “stack”. There are a lot of parameters, don’t bother too much with them, go with recommended ones.

10. After you got your stacked picture (a huge TIFF file), open it in Photoshop (my wife is a designer, I am lucky she has one) or in GIMP (this program is free) and process it. Processing stacked image is a science itself, I am just starting, so I am not very good at it. The main things you should do is to adjust levels and curves. Once I learn more about it, I will do a separate post. Keep in mind — this step is very important, your stacked result image will look nothing like the one you can get after post processing.

Here is what I got with my 70mm refractor from front yard. Unfortunately I don’t have a dark place near my house, there is so much light from everywhere , so I can read while I take pictures :-)

M27 Nebula pictured from my front yard with 70 mm refractor.

M27 Nebula pictured from my front yard with 70 mm refractor.

M13 globular cluster

M13 globular cluster. Here you can see I screwed the very middle of it while casting Photoshop spells.

How to Focus Astrophotography Camera (for Free!)

August 3, 2009

I finally got a nice clear night to play around with a new scope, so I have some more info to share. One of the first challenges you face in astrophotography is focusing your camera. You may be used to point and shoot auto focus kind of thing, but it obviously does not work here. Even if you have a sharpest eagle eye you most likely will fail to get a good focus manually. While there is special software which will help you do it, usually you have to pay for it, plus you have to pay for laptop (if you don’t own one already), plus you have to pay for accessories to connect your camera with a laptop (remote shutter to computer cable can easily cost ~$75), shortly speaking — you have to pay :-) When people are short on money, they start to think and mr. Bahtinov came up with a cool device which will get you a sharp focus in a matter of seconds.

This is how bright a bit overexposed star looks on photo with Bahtinov mask on the telescope. I took this picture on my front yard, feel free to redistribute ;-)

This is how bright, a bit overexposed star looks on photo with Bahtinov mask on the telescope. I took this picture on my front yard, feel free to redistribute ;-)

This is the idea: you make a special telescope mask and shoot a bright star with it. You will see 3 lines coming through the star. Top and bottom lines do not depend on focus, but the middle one moves up and down if you change focus. Take a picture, check where the middle beam is, if it is not in the middle — change focus a bit, shoot picture again. Rinse and repeat until you get the middle beam right in between the other two (like on the photo above). This method will probably give you the sharpest focus you can get without computer help. Mine Bahtinov mask looks like this (my wife made it for me :-)

Simple Bahtinov mask made from the burger cardboard pack. Feel free to share this picture.

Simple Bahtinov mask made from the burger cardboard pack. Feel free to share this picture. Paint it black if you want to look professional, in my case I have street lights shining right into my scope, so black paint is just breadcrumbs comparing to it :-)

Pattern depends on your telescope exact specification (clear aperture and focal length), but kind guys already created a nice Bahtinov mask calculator which will generate pattern for you. In my case slots were too thin with default setings, so I tweaked a “slot width” parameter a bit and it worked like a charm!