Impatient Tutorial
What is this thing?
If you're here to play around--perfect. That's what playgrounds are for. Spend most of your time in the Image Framing tab.
- For the first example, select Target Type and choose Solar System. Select Target Name and choose Moon. The moon is about 1 light-second away. You can move the Telescope Focal Length slider to adjust zoom.
- Next, select Target Type=Galaxy, Target Name=Sculptor. We are looking at galaxy that is 11 million light years away!
- Finally, select Target Type=Nebulae, Target Name=Trifid. This object is only 6000 light years away, Zoom out to see a large portion of our own galaxy, the Milky Way. Change Optical Filter Type to Narrowband. Notice how other nebulae brightly stand out. Stars are being born in those areas. Narrowband filters allow specific wavelengths to pass, associated with glowing hydrogen and oxygen in these star forming regions.
Get started in astrophotography
I want to get started in astrophotography, but don't know where to start.
- Note the three tabs: Image Framing, Capture, and Enhancement. These generally correlate to selecting equipment, choosing the setings to use it correctly, and procesing the raw images to make them look great. For this example, choose the Dumbbell Nebula. Choose a focal length that looks good. Now go to the Image Capture tab. Note the image gets brighter with more exposure, and more noisy with less exposure. You may need to adjust the bottom Brightness slider as you go. This only adjusts how the image is displayed; It doesn't affect the raw data.
- Although longer exposure time is generally better, you may choose a short exposure time if your tracking is poor. Move the Exposure slider down to about 1.5 seconds. Now move the #subs slider to the right. Even with noisy images, averaging several together will reduce that noise.
- Now move the Light Pollution slider to Suburban. You may need to pull back on the brightness slider. Note the hazy background from city lights. We'll take care of that in Enhancement.
- Choose the Image Enhancement tab. Move the Gradient slider to about 40%. Notice how the light pollution fades away. This process mathematically subtracts the effect of city lights. It's not as good as going to a dark location, but it certainly helps. Adjust the saturation and brightness to your liking. Also click on the color wheel if you want slightly warmer or cooler tones. Although we often strive to get close to the natural color of the human eye, there is certainly room for artistic license.
Select a new telescope or camera
Let's say you're in the market for a new telescope or camera. Let's use the Playground to help with our selection.
- For this example, select the Triangulum Galaxy, and choose the Narrowband filter
- Set the focal length how you like. Now move the Camera Sensor slider to the right. Note the increase in field of view. Wait--this is the opposite of zoom! Does this mean I can select a small telescope and just use a small camera? Technically yes, but small cameras and telescopes collect less light than their large counterparts. You can use this Playground to try and see the results for yourself.
- Go to the Capture tab. Note how noisy the image is. Try increasing exposure time and number of subs. In the previous example this helped with noise, but not here. Why? Since this is a dim object with narrowband filters, we get very little light to work with. Our image is now dominated by a form of camera noise called dark current. Some astronomy cameras can be electronically cooled. If we move the temperature slider to the left, we see that noise go away. Now we can increase exposure and subs to see image improvement.
- In the Enhancement tab, we can clean up this image with gradient removal. We can also alter the color towards the red, to see the nebulosity in this object. We may also want to increase saturation, to help those nebulae stand out.
Image from my suburban backyard
What if you want to image a faint target but don't want to travel?
- Select the Rosette Nebula, Color version. In Capture, move the light pollution slider to Suburban. Adjust the other sliders--Exposure to 100 seconds, and Subs to 30, Temperature to -5.
- In Enhancement, adjust Gradient and brightness. Try as you might, the image still looks pretty bad. You can even see artifacts from the algorithms that are synthesizing the image. The bottom line is, we are down in the weeds. Although we can subtract the light pollution with gradient removal, we cannot subtract the extra noise associated with the suburban lighting.
- Back to Framing, this time choose Narrowband. Use the same Capture settings as before. Now when we enhance the image, we have a much better image. Even though we have less signal with narrowband filters, we also have less noise from light pollution. The end result is a win. Not as good as if we had gone to a dark location, but not to bad.