Orion 52080 Focusing, Camera Control Window, select Light Raw 1x1 mode, Turn off Dark Subtract

Focusing

One of the hardest things to do in imaging is achieving good focus. You can simply watch the computer screen to focus (Focus in the Camera Control Window), but you can focus “by the numbers” on a bright star to get the best focus possible. To do this:

1.In the Camera Control Window, select Light Raw 1x1 mode.

2.Set the exposure time to 1 to 5 Seconds, depending on how bright the star is.

3.Turn off Dark Subtract.

4.Now beneath the Mode selector, pick Focus, and then click Expose. The camera will take repeated exposures, until you click Stop.

5.Point the telescope at a bright star, and you can focus “by the numbers”:

• MaxPixel is the value of the brightest pixel in the image. When you are in focus, it will be at its highest value. You will need to look at the value for several images in succession, because the number will bounce around with the seeing.

Note: If the MaxPixel reaches 65535, the image is saturated and all three focus numbers will be inaccurate. Either pick a fainter star, adjust the camera’s Analog Gain settings using the Setup button, or use a shorter exposure time.

•FWHM, or Full-Width Half Maximum, is the width of the star half-way down the sides. This provides a highly accurate measurement when you are close to focus. When you are at focus, it will be at its lowest value. This number will vary due to seeing, so it is best to look at several images before decided.

•HFD, or Half Flux Diameter, is similar to FWHM, but works much better than FWHM when the star is badly out of focus. It can produce a usable number even when the star looks like a donut.

Refocus often throughout your imaging session. This ensures at least some of your images will have an excellent focus. It is also not uncommon for tele- scope motions or movements to alter the focus slightly, so be sure to refocus after slewing to any new astro-imaging targets.

Choosing a Site for Astro-imaging

Once you have a focused image, you may find your image shifting and washed out. This can be caused by many environmental factors. Poor seeing (move- ment of molecules in the air, such as heat rising) and poor transparency (mois- ture, smoke, or other sky contaminants) will all serve to reduce image quality. That is why most major astronomical telescopes are on high mountains in thin air, to get above much of the transparency and seeing problems. Also, wind will move your telescope and affect images. Your eyes viewing through an eyepiece can change slightly to compensate for disturbances like these, but

the camera can not. Keep these factors in mind when choosing an observing site for astronomical imaging.

For the best astro-images, we recommend finding a location with dry air, some altitude, and away from city or streetlights. Even a nearby hilltop in the coun- tryside can provide better viewing conditions than many convenient backyard locations.

Loss of Camera Connection

If the computer connection to the camera is interrupted, you will need to re-establish connection. This can happen due to several reasons; if a cable becomes unplugged, the computer “freezes”, or the software/hardware other- wise temporarily loses the data coming from the camera.

To re-establish camera connection, first close the Maxim DL Essentials pro- gram on your computer. Then, unplug and re-plug the camera into the com- puter’s USB port. Now, open Maxim DL Essentials, and the Camera Control Window should appear indicating re-established connection between camera and computer.

Using Focal Reducers and Barlow Lenses

Focal reducers and barlow lenses change the effective focal length of a tele- scope. These lenses are inserted between the camera and telescope when imaging to change image scale.

Focal reducers serve to decrease the focal length of your telescope. This increases the field of view seen by the camera (decreases camera magnifi- cation). This can be very useful for obtaining images of wide-field deep sky objects, such as the Andromeda Galaxy or the Pleadies star cluster. Focal reducers will usually thread onto the nosepiece of the SSDSI-II.

Barlow lenses increase the focal length of your telescope, which makes the camera’s field of view narrower (increases camera magnification). This is useful for planetary imaging. Keep in mind that when the focal length is doubled, the image will become four times dimmer, so a longer exposure may be necessary. Barlow lenses are generally inserted in the focuser’s drawtube and secured with the thumbscrew on the focuser’s drawtube, and the SSDSI-II’s nosepiece is inserted into the barlow and secured with the thumbscrew on the barlow lens.

Filters

Any standard Orion 1.25" filter will thread into the front of the SSDSI-II’s barrel.

For some types of planetary imaging, you may want to use color filters to bring out subtle details. Try using several different color filters on a planet to see which filters help best show planetary details.

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