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If you save to a file format other than .fit, you will need to check the
Auto
Stretch
box, or otherwise
Stretch
the image to change the
Output Range
(in the
Stretch
command window) to match the
Size Format
(in the
Save As
window). Otherwise, the
Output Range
will likely exceed the
Size Format
,
and the saved image will be ruined (will turn all white).
For example, say the
Output Range
is set to create image brightness values in
16-bit format, while the
Size Format
of a specific file format (.jpg, for example)
may only support 8-bits. Since the 16-bit format sees 65535 brightness levels,
and the 8-bit format can only support 255 levels, all of the levels above 255
in the 16-bit image (i.e. the vast majority of the 16-bit brightness levels) will
be saved at the maximum 8-bit value of 255. So the saved .jpg will have very
little brightness information from levels 1 to 254 and almost all the brightness
information at level 255. Thus a white image results.
Other Features
Flip
– Flips image orientation. “Folds” image about vertical center.
Mirror
– Creates mirror image of current image orientation.
Zoom
– Increases or decreases level of image magnification on computer
screen. When you zoom in too much, you will start to see the squares of indi-
vidual pixels. When zoomed in, you can use Quick Pan; simply hold down the
Ctrl
key, then left-click and drag the mouse on the image.
Night Vision
– Toggles Night Vision mode. The red background helps preserve
your night vision.
Window menu
– These functions alter the way multiple open image frames
are arranged and displayed within MaxIm DL Essential. These functions are
very useful for organizing the visual display when processing large numbers
of images for stacking.
tips
Focusing
One of the hardest things to do in planetary imaging is achieving good focus.
You can simply watch the
Live Video
window to focus, 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 Color 1x1
mode.
2.
Set Frames
to 1.
3. Turn off
Dark Subtract
.
4. Pick
focus
beneath the
Mode
selector and then click
Expose
. The camera
will take repeated exposures, until you click
Stop
.
5. If you point the telescope at a bright star, you can focus more accurately
“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 sev-
eral images in succession, because the number will bounce around with the
seeing.
Note: If the MaxPixel reaches 255 (in 1 frame capture mode), the image is satu-
rated and all three focus numbers will be inaccurate. Either pick a fainter star,
or adjust the camera’s Exposure settings using the Setup button.
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 imag-
ing session. This ensures at least some of your images will have an excellent
focus. It is also not uncommon for telescope movements to alter the focus
slightly, so be sure to refocus for 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 seeing and transparency 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
program on your computer. Then, unplug and re-plug the camera into the
computer’s USB port. Now, open MaxIm DL Essentials, and the
Live Video
Window
should appear indicating re-established connection between camera
and computer.
