Imaging Deep Sky Objects

4.Focus the camera using the telescope’s focus knob. The focus point for the SSDSI-II will be approximately 15mm inwards from the eyepiece’s focus point. If you are having trouble determining best focus, try focusing on a bright star near the planet. Use the Planet setting in the Screen Stretch Window. You can also use the histogram functions for most accurate focus; this will be explained later (see “Focusing”). Click the Stop button in the Camera Control Window when camera focus is achieved.

5.Now, in the box beneath the Mode box, choose Autosave. Set the number of images you would like the camera to take under Autosave (start with 10 or so), select the ﬁle folder in which you would like to save the images with Folder, and enter in a Base ﬁlename for the captured images. Typically the name of the object being imaged, such as “Mars1”, will be entered here. If “Mars1” is the Base ﬁlename, and you choose to Autosave ﬁve images, then the images will appear in the selected ﬁle folder as “Mars1_0001.ﬁt”, “Mars1_0002.ﬁt”, “Mars1_0003.ﬁt”, “Mars1_0004.ﬁt”, and “Mars1_0005. ﬁt”.

6.Click Expose, and the camera will commence capturing and saving the images.

Now that we have multiple images of the planet, we will combine the images to form one high-quality resultant image. To do this:

7.Select Open from the File menu. Find the folder you indicated with Folder, open it, and select all images for stacking using the mouse left-click and the Shift key. All of the individual images selected will open in Maxim DL Essentials.

Note: In order to combine images, the images must ﬁrst be opened in Maxim DL Essentials.

8.Select Combine from the Process menu. In the pop-up window, you will see all of the images currently open in Maxim DL Essentials. Choose the individual images you want to stack and press the >> button, or simply click Add All. Click the OK button when done.

9.The Combine Images window will appear (Figure 13). For Align Mode, choose Planetary. In the Output box, select Average.

10.Now, you can see how each individual image looks by using the Next Image and Previous Image buttons. If you see an image that looks poor, you can reject it from the stack by clicking the Reject Image button.

Note: At least one image must be used as the reference image for the stacked images to be overlaid upon. The default uses the ﬁrst image for the reference image. If you reject the ﬁrst image or otherwise want to use another image as the reference, click the Set As Reference button when the desired reference image is actively displayed. If the image currently chosen as the reference is rejected from the stack, and another reference image is not selected, you will not be able to Overlay All Images.

Figure 13. The Combine Images window allows “stacking” of individual images into one high-quality resultant image.

11.Now, click the Overlay All Images button. All of the selected images will stack on top of each other to form one resultant image. Click OK.

You have now composed your ﬁrst planetary image. Use Save under the File menu to save your image at this time. To make it look its best, you will want to adjust the Screen Stretch Window to Planet. You may also want to do some image processing, see the section entitled “Image Processing” for more information.

To capture breathtaking images of deep sky objects, such as galaxies, nebu- lae, and star clusters, much longer exposures are needed. As with planetary imaging, you will take several individual images and stack them together to form one high-quality resultant image. But while planetary images are formed by stacking many exposures of less than 5 seconds, deep space images will generally be comprised of individual images of a minute or longer!

Because of this, polar alignment and motor drive tracking must be very accurate. If not, images will be blurred and stars will not appear round. Also, because camera noise increases greatly over exposure time (due to internal heat generation), you will need to suppress the inherent camera noise with the built-in thermoelectric cooler (TEC). Make sure the 3VDC power supply is plugged into the SSDSI-II.