Mars is growing daily in size and brightness as it approaches opposition night on 13 October 2020. On that date, the “Red Planet” will shine at magnitude -2.6 and be 22.4″ in diameter. At 5.5° above the Celestial Equator, it will be well placed for northern observers. Enjoy it while you can as it will not reach 22″ again until the year 2033! See our prior post on the Mars Opposition to learn why this will be the Last “Best” Mars Opposition for Northern Hemisphere!
Visual and Imaging Magnification Accessories for Mars
Properly designed Barlow lenses can do wonderful things: They amplify the power and at the same time slow the telescope’s f/# which is more forgiving of eyepiece performance.
Tele Vue Barlows are designed to be as optically neutral as possible given the simple negative lens configuration. Optimum aberration correction and ultra-high efficiency multi-coatings provide exceptional sharpness and contrast with virtually no light loss. They are even tested for performance at f/4 — the same full-field testing as all our eyepieces.
Tele Vue Barlows are available in 1¼” barrels (2x & 3x) and 2″ barrels (2x BIG Barlow).
Barlow: Rodrigo Carvajal’s (Santiago, Chile) Mars Imaging Strategy
Though he’s new at planetary imaging, Rodrigo Carvajal has already been featured on our Instagram page. Mars will be high in the sky in Santiago this year and Rodrigo will be employing a Tele Vue 3x Barlow in his 11” Dobsonian to reach a 4200-mm effective focal length for imaging Mars. He achieves amazing results with this setup using manual tracking!
My setup consists of a Homemade 11” f/5 Newtonian reflector with a Zambuto primary mirror on a dobson mount. I guide the scope manually while imaging. I am planning on a tracking platform later, but I am fine manually tracking now. I use a QHY5III178C camera and a TeleVue 3x Barlow which gives me the right image scale for planets with my telescope. I do 60 to 120 seconds videos that I then stack and process to get a final image.
I would like to add another TeleVue Barlow or Powermate in 2x, 2.5x or even 4x later to have different focal length options for changing seeing conditions.
I do visual observing too and I use 6 mm and 4.5 mm Delos eyepieces for lunar and planetary and 13 mm Ethos and 9 mm Nagler T6 for DSO with my 11” Dob.
You can find Rodrigo’s images on Instagram at @shadalf.
See our website for more information on visual and imaging applications of Tele Vue Barlows (mobile site).
For imaging, you can place an appropriately sized planetary camera in the eyepiece holder. However, Powermates™ have a special advantage for imaging: the visual tops unscrew to accept specific Tele Vue Powermate™ T-Ring adapters. This allows for square and secure attachment of cameras and T-threaded accessories. Most any commonly available DSLR, astro-camera, and even some industrial cameras will work with Powermates™.
Powermate: Frederick Steiling’s (Missouri, USA) Mars Imaging Strategy
Frederick will be imaging Mars at a focal length of 7820-mm with his 2x Powermate and astronomy club C14 scope. His setup will be similar to the one he used for the 2018 opposition with the addition of an Atmospheric Dispersion Corrector. He lists his gear as follows:
Scope: Celestron C14 (Astronomical Society of Eastern Missouri scape at Broemmelsiek Park)
Barlow/Magnification: Tele Vue 2x Powermate
Mount: Celestron CGE Pro
Camera: ZWO ASI174MM
Focuser: Moonlite 2.5″ CSL
Filters: ZWO 1.25″ RGB + Astronomik 742 IR-pass filter
Correction: ZWO Atmospheric Dispersion Corrector
Pairing the ASI174MM with the C14 and a Tele Vue 2x Powermate sets the stage for excellent planetary data acquisition.
Pairing the ASI174MM with the C14 and a Tele Vue 2x Powermate sets the stage for excellent planetary data acquisition. This combination provides an image scale of 0.15″ / pixel, making for a great “lucky imaging” resolution, even under the soupy skies of the midwestern US. Cutting through the wavy atmosphere and bettering the opportunity to do so are the most critical aspects of planetary imaging, especially at a high focal length like this, and there are a few approaches that I take to this end.
First, keeping exposure times as short as possible can not only increase the number of frames captured but will also give a better opportunity to freeze very momentary stability in the atmosphere before it begins bouncing and waving again. To aid in this approach, I typically boost the camera gain between 50-75% to provide a good balance between shortening the exposure time without over-noising the data, and set the exposure time by aiming for a histogram peak that reaches around 60% of full range.
Second, using a fast connection on the camera (USB3) with a PC/laptop that can keep up (USB3 port to a solid-state drive) will ensure that download/storage bandwidth can keep up with the acquisition speed of the camera.
Third, when using a monochrome camera like the ASI174MM, an IR-pass filter like the Astronomik 742 can mitigate poor atmospheric seeing that is typically more problematic in the visible spectrum. The IR data – on its own as the luminance component or when blended in combination with true luminance data – can help bring out sharp detail when combined with RGB data in processing.
Lastly, once back in the comfort of home and using a planetary stacking tool like AutoStakkert!3 to analyze the video data, it is important to have a discerning look at the quality-ordered frames to determine what percentage of frames are worthwhile to approve and stack. With a 3-minute video at 15ms exposure length, even selecting only the best 10% of frames will stack 1200 frames!
There are many challenges in achieving clear, high focal length views through Earth’s atmosphere, but these approaches combined can give an excellent chance to do so during this year’s Martian opposition.
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