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1. Introduction:
Planetary imaging is by far the most instantly rewarding type of astrophotography. Rather than trying to
maximize exposure time you are trying to minimize it to capture the small windows of superior seeing.
This tutorial will cover every detail and step needed to take a detailed picture of Jupiter (and other
planets), from image capturing to final post-processing.
2. Camera Selection:
One thing a lot of people do with planetary astrophotography is try to use a camera that is not well suited
for the task. For example, a DSI Pro I may be able to get an image of Jupiter on the chip, but the minimum
exposure rate and most importantly, download speed, are not well suited for the application. If you are
going to go to all the trouble of trying to produce a good image of Jupiter (image post processing is labor
intensive!) you should make sure you have the right camera for the job. Here is a list of important camera
properties to have for planetary imaging:
High Download Speed
High frames per second (fps) are crucial for planetary astrophotography. The more frames you can capture
during the imaging session, then the more frames you can stack and the more processing you can do to
pull out fine details in the planet without creating noise in the image.
Sensitivity
It’s imperative that the camera you use has a very high sensitivity. The higher the sensitivity, the lower
the exposure needed during capture and thus the more frames you can capture and stack.
Monochrome or Color?
The choice between a color and monochrome camera is an endless debate on the Cloudy Night forums.
However, if you look at all of the most spectacular images created by amateur astronomers, they are
made using a monochrome camera. That is not to say monochrome cameras do not have their drawbacks
and disadvantages. Monochrome cameras are more expensive due to the need to have filters, but result
in an image with better resolution. Color cameras do not need expensive filters and the post-processing
can be much simpler. Take a look on the Cloudy Night forums and see example images posted by other
amateur astronomers.
My Planetary Imager
I use the ZWO ASI120MM USB 2.0 camera. This camera is currently the most popular planetary imagers
on the market today. If you search the Cloudy Nights forums, this camera is even what the “amazing”
pictures come from. There is a guy down in Australia that takes the most amazing pictures with this
camera and a C14. It has many advantages, from the “relatively” low price range (~$300) to being
incredibly small and compact. It also comes with a neat 150 degree lens that screws directly on the
camera. You can get some great night videos by placing the camera on a tripod and setting the exposure
to every few seconds. It can also function as guide camera (even has a built-in guide port). This camera
does not have thermoelectric cooling, but that is really not needed for planetary imaging.
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Figure 1: Photograph of the ASI120MM camera
Table 1: ASI120MM Details
Camera Specifications
Sensor: 1/3" CMOS AR0130CS(Color) /
MT9M034(mono)
Resolution: 1.2Mega Pixels 1280x960
Pixel Size: 3.75µm
Exposure Rage: 64µs-1000s
Supported Resolutions
1280X960@35FPS
1280X720@46FPS
1280X600@55FPS
1280X400@80FPS
960X960@46FPS
ROI: Supported
Interface: USB2.0
Bit rate: 12bit output（12bit ADC）
Adaptor: 2" / 1.25" / M42X0.75
Dimension: φ62mm X 28mm
Weight: 100g
1024X768@54FPS
1024X600@69FPS
1024X400@101FPS
Working Temperature: -5°C—45°C
Storage Temperature: -20°C—60°C
Working Relative Humidity: 20%—80%
Storage Relative Humidity: 20%—95%
800X800@66FPS
800X640@82FPS
800X512@102FPS
800X400@108FPS
800X320@158FPS
640X560@98FPS
640X480@113FPS
512X440@123FPS
512X400@135FPS
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480X320@165FPS
320X240@215FPS
2X2Bin：640X480@35FPS
3. Imaging Equipment
Once you have selected an imaging camera specifically dedicated to planetary imaging, there are several
other pieces of equipment needed in your optical train for planetary imaging.
Barlow Lens
Depending on the native focal length of your imaging telescope, you will probably need to have a barlow
lens in order to capture the finer details of the planet. It is important to have a magnification that matches
the ideal arc seconds per pixel of your camera. The arc seconds per pixel of your camera and imaging
setup can be calculate by:
arcsec/pixel =
𝑃(206265)
𝐹
(1)
where P is the pixel size of your camera (mm) and F is the focal length of your imaging setup (mm).
Depending on what barlow you have, there is some adjustment on the amount of increased magnification
you will be getting. Once you have filter wheels and other accessories between the camera and the barlow
lens, your magnification will increase. The figure below shows the magnification of TeleVue barlows with
varying distance from the imaging chip. I typically image at 3.0X magnification (filter wheel in front of the
barlow), which is pushing my little 8 inch Meade SCT a bit. You can either put the filter wheel before or
after the barlow, depending on what magnification you want. Figure 2 below shows the effective
magnification of several TeleVue barlows depending on the distance from the chip of the CCD camera.
Figure 2: Magniciation of various TeleVue barlows at varying distances from the imaging surface
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Filters
If you choose to use a monochrome camera, you will be using three filters for basic imaging of the planets;
R, G, and B. There are high end filters (Astrodon) and low end filters (Meade) available today. If money is
tight, the Meade filter set (~$35) is the way to go. However, these filters are not parfocal (meaning you
have to refocus between each filter) and they do not have an IR blocking filter built into each color filter.
That means you have to use two filters in series for each channel you image, i.e. clear IR filter + Red filter,
etc. This causes you to have a slightly higher exposure since you are losing more light. I started out with
the Meade filters and have since upgraded to Astronomik. I have found that the post processing involved
with Astronmik is much less than the Meade filters and the amount of light that reaches the chip is
noticeably increased. A comparison of the light curve for the Meade and Astronomik filters are shown
below in Figures Figure 3Figure 4.
Figure 3: Spectral transmission of Astronomiks LRGB Type IIc filter set
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Figure 4: Spectral transmission of Meade’s LRGB filter set with the IR filter placed in series
In order to switch between the R, G, and B channels quickly enough during an imaging session a filter
wheel is a must. Jupiter rotates so quickly that you are limited to how many frames you can take per
channel before rotation becomes too much. This can be mitigated by using programs like WinJUPOS which
we will talk about later on in this tutorial. I use a basic manual Orion 5 slot 1.25” filter wheel. There are
much nicer filter wheels available that have the ability to automatically switch between channels via a
USB connection to your computer and your image capture software. I believe the biggest advantage of a
motorized filter wheel is that the filters are completely sealed from dust in the imaging train. I currently
use some electrical tape on my manual filter wheel to help prevent light leaks and dust from entering at
the manual slide.
Mount
Unlike imaging DSOs you don’t need an incredible mount or a guiding camera/telescope. I have seen
amazing pictures (much better than mine) from people using MANUAL tracking. However, it is greatly
advised to have a mount capable of tracking since you will be so incredibly zoomed in on the planet you
are imaging. There is enough headache already! Therefore it is important to have a good polar alignment,
but you don’t need something that will keep Jupiter smack dab in the center of the chip for hours on end.
Small movements of the planet you are imaging over time can easily be corrected with a slight slew of the
mount. If the planet you are imaging is slowly drifting across your chip, then when you stack the images
you are effectively reducing any dust spots that you might have.
Focus
Focus aids are very important. It is beneficial to have a Bahtinov focus mask and a micro focuser. The
primary mirror focuser on SCTs is very course and moves the object to be imaged around the chip, making
you re-center each time after focusing. This can make it almost impossible to know if you have achieved
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perfect focus. Therefore it is worth buying a microfocuser that attaches to the back of your SCT and allows
fine focus adjustments without any image shift.
Optical Tube Assembly
It is beneficial to be imaging with a telescope that has a natively long focal length. SCTs are by far the most
popular choice for planetary imaging for amateur astrophotographers. The larger the aperture, the more
precious photons you will get and the more details you can pick up. Some of the best planet photos I have
seen were taken from a C14. However, a larger SCT also means you will suffer from “mirror flop” and
several other problems, but this does not outweigh the benefits of a larger aperture.
My Setup
My complete setup for planetary imaging consists of the following: ASI120MM camera, 3X TeleVue
Barlow, Orion Manual Filter Wheel (with Astronomik LRGB), and an 8 inch Meade SCT on a Celestron
CGEM.
4. Imaging Software
There are many free programs available today that can be used for image capture with almost any USB
camera. FireCapture is one of the best, allowing you to program specific settings for each color channel
that is to be shot. It has many customizable options and if you are going to use WinJUPOS, it also has a file
saving convention for that which can save you hours. For this tutorial, the image capturing process will be
discussed in detail using FireCapture in section 6.
5. Collimation and Preparation
Seeing is king, as they say. It is important to have a good grasp of what the night sky conditions are going
to be like and if it is worth it to go to all the trouble to try to image. You can have the best camera and
telescope and on a mediocre seeing night your image will look something like an image from a toy
telescope.
If you are using an SCT, then collimation is IMPORTANT! You cannot get detailed images of any planet if
you are not properly collimated. Collimation is something that is greatly dependent on sky conditions,
which can easily limit how well you can collimate your telescope on a given night. There are several tools
that can help you when collimating your SCT, some more useful than others. Below are some methods to
achieving good collimation with your SCT. You should check the collimation of your telescope before
EVERY imaging session!
Basics of SCT Collimation:
Collimation involves adjusting the secondary mirror so that it is perfectly aligned. On most SCTs there are
three adjustment screws on the front of the telescope that when turned, adjusts the alignment of the
secondary mirror. A slight adjustment of collimation can mean the difference between seeing details in
Jupiter’s bands or a vague smudge. If you plan to collimate your scope a lot (it should be done before
every imaging session) then it may be useful to pick up some of Bob’s Knobs to allow for easier and finer
adjustment. The first step of collimation is to view a bright star near the zeneith at prime focus with the
telescope (no barlows, etc). As you go in and out of focus, you will see the donut get larger and smaller.
The initial step of collimation is to make this donut round and uniform. The concentric circles within the
donut must be aligned and symmetric. Once the rings in the donut are fairly centered, you will want to
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switch to a higher power eyepiece. It is also recommended that at this point you collimate with the
imaging train you will be using. It is important to allow your telescope to come to thermal equilibrium
with the ambient environment, or you will have tube currents wreaking havoc on your image. After you
have centered the rings do the best of your ability, you should then achieve focus and see the “airy disk”
if sky conditions are great. Final tweaks are made to center the star within the elusive airy disk.
The Duncan Method:
Collimation may also be achieved by using the focus mask shown below. Find a fairly bright star near the
zenith and place the mask over your telescope so the gaps are opposite of the collimation screws. By using
a 400X magnification eyepiece you will see curved images of the gaps. As you adjust focus they will flip to
lines pointing at the center. Adjust the opposite screw accordingly, and once collimated all of the lines will
perfectly cross. This procedure is shown in Figure 5:
Figure 5: Collimation process using a Duncan focus mask
MetaGuide:
When seeing isn’t great, or even if it is, this program will allow you to get much more accurate collimation
of your telescope. MetaGuide stacks images in real time to help you see the airy disk when collimating. It
will also tell you in what direction you need to adjust the secondary mirror. Figure 6 shows an example of
MetaGuide during the collimation process. This program is free online.
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Figure 6: Screenshot of the MetaGuide UI (http://www.astrogeeks.com/Bliss/MetaGuide/)
Finder scope
This may seem trivial, but it is imperative that your finder scope is VERY accurately aligned with your OTA.
Either align your finder scope during the day on a distant object or use a crater on the Moon. Once you
have a rough alignment, it is best to slew to a bright star and use a low magnification eye piece to further
align the finder scope. Increase the magnification of the eye piece as needed for increased accuracy. The
go-to on your telescope you will let you down 9 times out of 10 when at high magnifications.
6. Image Capture
Once your telescope has been properly collimated then you are ready for image capture! At this point you
will already have your final imaging train hooked to the telescope. Go ahead and close whatever software
you were using for collimation (MetaGuide, etc.) and open up FireCapture. This program is fairly selfexplanatory, but we will go over some of the basic features. One of the best parts of FireCapture is that
you can change the size of the image you are actually saving and downloading to the computer. You can
enter a dimension in pixels for your imaging size by using the ROI option. Make the image size as small as
possible while still allowing breathing room for the planet to move around the chip. The smaller the image
size, the higher the fps you will be able to capture. Gain, gamma, and exposure are easily adjusted in the
program and are remembered for each filter channel you select (top right). It is important to change the
file naming convention to be compatible with WinJUPOS. GO to settings>parameters and select winJUPOS
file naming convention. I prefer to use the saved file type as SER rather than AVI, just because I have found
that with large video sizes (8 gigs) programs prefer SER. Turn on the histogram feature, this will allow you
to see in real time the histogram value and what the average value was for previous channels imaged. As
a rule of thumb, you should try to have Jupiter at a histogram value of ~70% for each channel.
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After collimation you will still be centered on a fairly bright star near the zenith, this is perfect for your
initial focus. Throw on a Bhatoniv focus mask and adjust the focus accordingly. Seeing will go in and out
so take your time, as good focus may be hidden during a period of bad atmospheric conditions.
The next hurdle, once you have made it here, is actually getting the planet to be imaged on your chip. This
can be easier said than done. Make sure you have an excellent alignment between your finder scope and
imaging OTA. Slew your telescope to Jupiter, 9 times out of 10, it will not show up on your laptop screen.
This is no surprise considering the incredibly small FoV you are using. Go ahead and take the imaging
camera off the telescope and insert an eyepiece. You will see an out of focus donut, but do not adjust the
focus! Center the out of focus donut to the center of the eyepiece and then place the camera back on the
telescope. Several iterations of this may have to be done, but eventually you will get the planet on the
chip.
Now, there are several options you can do with regard to focusing at this point. If the star you focused on
with the Bathoniv mask was close to the planet you are imaging, then it might be worth the time to run a
series of image captures at the focus you are at. If not, it is at this point you can either slew to a moon of
the planet and use a bhatoniv focus mask, or use your own judgment when adjusting focus on the planet
itself. When using visual judgment, lower the gamma to 0 and slightly angle the laptop screen back to
increase the contrast of the visible features of the planet. Keep the gain near 50. This is where the
microfocuser shines, if you were to adjust the primary focus knob (moving the primary mirror) you will
also be moving Jupiter around the chip and will have to re-center after each adjustment. You will also be
able to notice mirror flop, which adds another layer of difficulty. Adjust the focus until you feel you can
see the best contrast of the planet visual features. After each focus adjustment, wait several seconds to
make sure that it is not a change in seeing rather than focus. If your microfocuser has a digital readout
display, then you can find the correct focus for each color channel and easily adjust to that number when
you switch filters. The blue filter should need the most focus adjustment compared to red and green.
Once focused, it is time to setup each color channel in FireCapture if you are using a monochrome camera.
A screenshot of FireCapture during an imaging session is shown below in Figure 7. Start by selecting the
red filter and make sure your actual red filter is in the imaging train. Adjust the gain to somewhere near
75 or so (I have used as high as 85). Change the exposure accordingly to achieve a histogram value of
nearly 70%. We are also going to want to automatically limit the time for each channel. In this case since
we will be using WinJUPOS for post processing we will do 300 seconds per channel. Once you have done
this for the red filter, switch to blue on the pull down menu and then change to the blue filter in your
optical train. Repeat for the green filter. FireCapture will remember these settings for future use, but you
will have to do a preliminary check of them at the start of each imaging session (and during) as seeing
conditions will vary.
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Figure 7: Screenshot of an imaging session with FireCapture using the green channel
You will need a significant amount of hard drive space available for each imaging sessions (~100 gigs).
Each 300 second video will be somewhere near 7 gigs in size. Seeing will constantly change throughout
the night. It is important to check your focus between every image capture or every few.
7. Imaging Procedure
In short, here is the basic imaging procedure:
1)
2)
3)
4)
5)
6)
7)
Polar Align Mount
Collimation
Focus (either Bhatoniv focus mask and/or visually on the planet)
Setup FireCapture settings for each channel (RGB)
Run a capturing run (R, G, and B)
Adjust focus on planet by visual inspection
Repeat steps 5 and 6
8. Image Processing
To get the most detail (or any) out of your image involves heavy post processing. Here are the programs I
use for image processing in chronological order, some are repeated:
1)
2)
3)
4)
5)
6)
Autostakkert! 2 (Free)
Registax 6 (Free)
WinJUPOS 10.1.2 (Free)
Autostakkert! 2 (Free)
Registax 6 (Free)
Astra Image (Free Trial – Optional for Processing)
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7) WinJUPOS 10.1.2 (Free)
8) Photoshop (Can get free trial)
The first thing to do after your imaging session is pick through all of your raw red channel videos and see
which ones have the best raw quality. To do this, we are going to use Autostakkert! 2 (AS!2) to stack all of
the images and create a lightly processed stacked image for each set. AS!2 is a very basic but powerful
program, the settings menu is shown in Figure 8.
Figure 8: Screenshot of Autostakkert! 2
Click open, and select the first red channel video file you would like to stack. Select planet (COG) and
dynamic background. For the quality estimator, select gradient for large planets, such as Jupiter and
Saturn, or Edge for smaller planets like Mars and Venus. The noise robustness depends on just how noisy
your raw images are. Typically this should be left at a value of 3, but if your image is very crisp (little gain
used) then you can use a higher value. Click Analyze. This will order your frames in terms of quality and
buffer them in the program. The quality graph will show in grey the image quality over the imaging session
in chronological order, while the green line represents the order of quality that AS!2 put the images in.
Select TIF under stack options. Use the slider, shown in Figure 9, to go through your sorted images. Try to
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decide what percent of the images you would like to use. I usually do not use any images that are below
a quality of 50%. In this example shown, that would mean stacking about 50% of the frames. It is
sometimes better to stack less images than you think, as adding poor images will decrease your noise but
ruin any hope of seeing fine details of the planet. It is worth some experimentation.
Figure 9: Screenshot of the image viewing window in AS!2
Select normalize stack and set it to 85%. This will account for background variations between different
frames if seeing conditions change. For the sharpened image, you can set it to 50% or try other values.
This is simply going to output a slightly sharpened image of your stack. Do NOT use this image for
processing later on, only as a comparison between stacks. There will be image artifacts if you are going to
use wavelets in Registax later on. Select HQ refine and then click Stack. Repeat these steps for all of your
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raw red channel videos. Once done, compare all of the slightly sharpened stacked images and decide
which ones are the sharpest. The fewer you select the better, as the rest of the image processing is
incredibly lengthy, tedious, and will give you a headache.
Once you have selected the best set of images to use, go ahead and stack the corresponding green and
blue channels. Now it is time to do a little processing in Registax of these processed images before bringing
them into WinJUPOS.
Open Registax 6, click select, and select your stacked red channel image that was no sharpened. It can be
tempting to use the default wavelet filter in Registax, but it is much better to use the Gaussian filter
instead. It takes a little more work and is more temperamental, but the end result will be worth it. You
will end up with a more natural looking Jupiter. Select Use Linked Wavelengths, pull the slider tab of layer
1 to 100, and then adjust the noise and sharpening values accordingly. I usually have a noise value of 0.25
– 0.35 and a sharpening value of 0.1 – 0.25. Now move the layer toolbar to about 5, set the noise value
from 0.2 – 0.35 and the sharpening from 0.1 to 0.15. For other planets, however, it may be better to
simply use the default wavelet function in Registax. I have noticed Saturn and Mars have a poor response
to Gaussian wavelets in Registax compared to using the default filter. These values will vary from image
to image and there is no cookie cutter method, but this gives you an initial ballpark to try. You can then
save this scheme by pressing the Save Scheme button at the bottom. Saving many schemes is a great thing
to do and will allow you to better compare different image enhancements. Figure 10 shows the initial
wavelet processing discussed above.
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Figure 10: Screenshot of a raw stack with a Gaussian wavelets applied in Registax 6
Repeat these steps for the green and blue channels. These three images will not be used for your final
compiled image, but instead only serve as an initial image measurement in WinJUPOS.
Open WinJUPOS and click Program > Celestial Body > Jupiter. Now click Recording > Image
Measurement…, a screen will appear as shown in Figure 11. Click open image (F7) and choose the red
image you processed through Registax. If you saved with WinJUPOS file naming convention in FireCapture,
then the time of the video will auto-populate. Enter your Geogr. Longit. and Geogr. Latit. Click the Adj.
tab and select Outline Frame > Automatic Detection. This will usually get a pretty good outline of Jupiter.
It is very important that the north pole of the image outline (N) is actually on the north pole of your image.
You can use the ‘n’ and ‘p’ keys to rotate the image. The Page Up and Page Down keys will increase and
decrease the size of the outline, respectively. You can also check the box that says LD compensation, and
this can help aid you in correctly outlining Jupiter. It is better to make sure you are a little over the edges
of the planet rather than directly on. If you fail to outline the entire planet, then you may very well have
a sort of “onion ring” artifact later on down the road. Save this image (under the Imag. Tab). Now repeat
this same procedure for the Green and Blue channels.
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Figure 11: Screenshot of the imaging measurement panel in WinJUPOS
Once you have created three image measurement files (.ims) for each channel, click Tools > De-Rotation
of Video Streams in WinJupos. Where it says original video, click “…” and select the red channel video.
The time fields will auto-populate for you, if not, then make sure you have any program that might have
the video open closed. Now click select the image measurement file you created for the red channel by
selecting the “…” where it says “Image Measurement of a Preliminary Image from the Original Video”.
Click “Start De-Rotation of Video Stream” and WInJupos will start de-rotating your video. WinJupos selects
the frame from the middle of your video as a reference to rotate all other frames to. Repeat these steps
for the green and blue channels.
After you have a de-rotated video for each channel, open AS!2 again. Go ahead and stack the three
channels as you did before, but this time using the newly de-rotated videos. Once done, open Registax
and process the images as before. You may notice that there is a different response to the same settings
you used for the measurement images for WinJupos. After you have all three channels processed, open
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up Astra Image. In this program you can do slight deconvotultion to each photo. However, this program
is pretty optional in post processing unless you are very serious and have excellent data (I only have the
trial version of this and do not really use it much). At this point you may also do some editing in Photoshop
on the three derotated color channels. Be careful in how and what editing you do, because the RGB
combination later can be distorted and it will be hard to achieve color balance.
Now open WinJUPOS again and create measurement images of the three final derotated color channel
images. Then go to Tools > Derotation of R/G/B frames… Select the three measurement images you just
created for the R, G, and B channel. Then select the red channel for the luminance option. You may have
to experiment with the LD values, as lower values can help get rid of any “onion rings” you may produce
in your image. Change the image type to TIFF and then select “Compile Image”. Some planets, such as
Saturn or Mars may look better only doing an RGB compilation. I have found Jupiter to be the hardest in
terms of post-processing and achieving proper color balance.
With the LRGB image you just produced you can do final touches in photoshop, such as curves, levels,
final unsharp masking, etc. Enjoy your final image!
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