Skylog: Looking Up!

Let's Try Some Imaging!

Some caveats:  My astroimaging experience is very limited. My own telescopes are manually operated (no GOTO) with no cameras. The only imaging I have done is using robotic telescopes. With the capabilities of these higher-powered scopes and the ability to capture more light over time to see dim objects, I had to do some research on "what to look at" beyond Messier and famous named objects.  Give me a list of object names or NGC numbers and I really would have a hard time selecting something. Show me pictures... and I can immediately point out what I'd like to try to image.  Hopefully, these websites and suggestions will help you to select and successfully image night sky objects.

First, use your planetarium software to make sure the object is above the horizon and high enough in the sky to be visible during your imaging session.  This seems obvious, but I actually have tried on more than one occasion to image something that was too low in the sky to be seen. Also take time to find out where the object is relative to the moon.  The moon really washes out images.

You also need to know some information about the telescope and imaging equipment you will be using. Specifically, what the "field of view" (FOV) is for the system you are using.  Having a small FOV can mean the possibility of seeing more detail on small objects. If you are hunting for NEOs or comets, you may want a wider field of view to help you spot movement.  Knowing the FOV and size of your target object will help ensure your image turns out more like you hope. Check out this page at the Faulkes Telescope Project; in all the images, the red square has the same FOV. As an example, the primary cameras used at MyTelescope.com have a FOV of about 10' (arc minutes) RA by  8' Dec.  The Whirlpool Galaxy (M51) is 9.8'x 7.8' so will nicely fill the view.  The smaller Ring Nebula (M57) is about 1.4' across but will still be clearly visible in that same FOV.

At the sites you are considering, read through all the user guides and FAQs and watch any tutorial videos they offer. Check out their forum and look at images others have taken, questions and solutions.  The systems that offer you more control often charge based on the amount of time you use, so you want to be as efficient as possible when imaging.  Here are links to the specifications for a few online systems where you have varying control over the imaging process.

1. Go to Simbad and make sure you are on the "Identifier Query" page
2. Enter the identifier for the object you are considering ('NGC 4490', 'M13', etc.), then click the Submit ID button.  Simbad will move to a new page loaded with information about the object. 
3. About halfway down that page, under Plots and Images, click on the "Aladin applet" button. You will leave Simbad, and the online version Aladin will automatically launch and load the object you selected.
4. Overlaying the photo will be some data layers that help identify nearby stars and other objects. If you click on something on the image, you can see the list of nearby objects at the bottom of the screen. You can turn them off by removing the checkmark of the red  and blue layers at the right side of the screen.  You should then just see a black and white image of the object labeled DSSxxx at the right.

• Look at the scale at the bottom of the image. This will give you an idea of how large the object will appear in the imaging system you plan to use.
• Click the "Dist" button to the right of the image to draw a line across the image and get the distance covered by the line.
• The red down-pointing arrow tells you what the image is centered on.  Look at the Cocoon Galaxy ( NGC 4490) or Whirlpool Galaxy (M51) and see how it centers on the larger of the two interacting galaxies. If you move the mouse over the image, you can see what other coordinates you might use when imaging to better capture the entire system in your image.
• Select the DSS layer and click the Pixel button. You can adjust the brightness and contrast levels, and many other adjustments (and there is a handy 'reset' buttton, just in case!)  I often lighten and darken the image significantly to see how it might look 'right from the camera.'
• Want to save your Aladin image for reference?  Click the disk image at top left, or use the File menu.
• If you add a layer and want to remove it, click on the name of the layer at right, and then the Del button to delete it from view. Do not delete the bottom-most DSS layer - or you delete the image!
• You can also enter coordinates, and then use those red and blue identifier layers to figure out what is in view.  I have used this on old 'coordinate missions' at Slooh to figure out what I was looking for.
• Delete all the layers at right, and you can enter new coordinates or an object name into the Location box at the top of the screen (rather than going back to Simbad).

• Take some pictures and see what happens.  I have found I can get some nice B&W images with exposures of 5 minutes or so.
• Post what you want to image in the Astronomy.FM forum and ask for suggestions from experienced members.
• Look for other images for the object on the internet - many people include the settings they used.
• Weather and moonlight will affect your images; try imaging the same object at different times.

NGC 4490 luminance only (MyTelescope.com)

NGC 4490 LRGB (color) (MyTelescope.com)

M57 as imaged from Bradford Robotic Telescope

M57 image from Bradford Robotic Telescope after further processing by David Donnell