Planetary Imaging and Saturn Opposition 2021


Every year when the planets reach opposition, I try to image them. Each year I learn new tricks and apply them. Saturn reached opposition on August 2, 2021.

Despite the clouds, rain, and smoke, I have been set up for planetary imaging every clear night. The seeing is unpredictable which makes planetary imaging to be “lucky imaging”. I was fortunate to capture several gigabytes of data of Saturn and capture to date, my best image of Saturn. I captured this with my Celestron 9.25” EdgeHD, a Televue 2.5x Powermate, and a ZWO ASI462mc OSC camera. I also use a ZWO Atmospheric Dispersion Compensator (ADC) to assist in imaging the planets when they are low to the horizon.

Here are some trick I have learned for planetary imaging.


1. Let your scope come to temperature and cool down. This will help with stability and consistent focus.


2. Ensure your optics are aligned and you have a precise collimation. I do this on a star nearby the planet. I defocus the star to see the airy bands. I use Bob’s knobs on the front of the scope on the secondary mirror to make slight adjustments. One of the benefits of having my scope mounted in a dome and on a pier, is that the collimation holds well. I make the slight adjustments to ensure the star and the bands are perfectly symmetrical. This will help sharpen your image and achieve fine focus.


3. Use an electronic focuser. For focus, I use a ZWO Electronic Focuser (EAF). I control it through the ASIair app and with the ASIair Pro for fine focus without shaking the scope.


4. Use capture software which will allow high frame rates and speed. I use my laptop with Firecapture loaded on it to capture images.


5. Use a high speed planetary imaging camera. The cameras come in different specs and with different pixel sizes. When the seeing is lousy, my ZWO ASI174mc OSC camera performs nicely. When the seeing is decent, my ZWO ASI462mc OSC camera performs nicely with the smaller pixels. The high speed planetary camera allows me to capture as many frames as possible in the shortest amount of time. This is critical due to the planets’ rotation. For imaging Jupiter, I image as many frames as I can in 150 seconds. This prevents the detail from blurring. For imaging Saturn, I image as many frames as I can in 600 seconds. I control the frame rate by lowering the exposure and compensating with gain. The lower the exposure, the greater the frame rate will be. I capture all my files as Serial (*.ser) format to ensure reliability and raw uncompressed data.

I stacked the serial file of Saturn in Autostakkert 3, adjusted wavelets in Registax, and adjusted curves, saturation, and final sharpness in PixInSight.


Here are the settings and metadata from this Saturn image:


FireCapture v2.7 05 BETA Settings

------------------------------------

Observer=Unknown

Location=Unknown_City

Scope=Unknown_Scope

Camera=ZWO ASI462MC

Filter=B

Profile=Saturn

Diameter=18.52"

Magnitude=0.18

CMI=105.0° CMIII=333.1° (during mid of capture)

FocalLength=5250mm (F/22)

Resolution=0.11"

Filename=2021-08-03-0435_3-U-B-Sat.ser

Date=030821

Start=043021.916

Mid=043521.928

End=044021.940

Start(UT)=043021.916

Mid(UT)=043521.928

End(UT)=044021.940

Duration=600.024s

Date_format=ddMMyy

Time_format=HHmmss

LT=UT -4h

Frames captured=22273

File type=SER

Binning=1x1

Bit depth=8bit

Debayer=yes

DebayerAlgorithm=NearestNeighbor

BayerPattern=RG

ROI=792x644

ROI(Offset)=600x96

FPS (avg.)=37

Shutter=26.94ms

Gain=287 (47%)

AutoExposure=off

AutoGain=off

Brightness=1

HighSpeed=off

USBTraffic=100

WBlue=95

WRed=52

Histogramm(min)=0

Histogramm(max)=0

Histogramm=0%

Noise(avg.deviation)=n/a

eADU=0.168

AutoAlign=true

PreFilter=none

Limit=600 Seconds

Sensor temperature=22.1°C


A special thanks to Greg LaMonica, who took me under his wing and taught me how to maximize my planetary imaging with the unstable and turbulent seeing. He also gave me tips with Autostakkert and Registax. Thanks Greg! 🤩