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Rating Mars Oppositions, or why you should move to Australia

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#1 Lacaille

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Posted 05 February 2023 - 05:29 PM

Hi all,

 

I am just in the throes of putting together my photobook of images of the planets, which I send out annually as gifts to slightly bemused family members to let them know what I’ve been up to over the past year. This year’s book is proving to be a struggle to fill, as 2022 was wretched for astronomy in Canberra and for much of SE Australia. A certain amount of padding will therefore be needed, of which the following series of diagrams exploring the orbital mechanics of Mars will be a part. I am posting it here in case, like me, you had only a dim grasp of the determinants of favourable Mars oppositions.

I restrict myself in the analyses to oppositions from 2003 to 2035, with the 2035 opposition being close to maximum size for a Mars opposition (24.6 arcsecs at closest approach), at which time, if I am lucky, I would be 78 and, I hope, still pottering about with a C14! If you are interested in studying oppositions way into the future, however, this is a great resource.

 

 

Solar longitude – an important quantity

 

First, I had to get my head around Solar Longitude (Ls), a quantity that tells you where Mars is in its orbit and its seasons. You can get Ls for any date from the Ephemerides tables in WinJUPOS.
The diagram below is slightly adapted from the excellent resources here. It shows the interaction between Ls, distance from the Sun, and the seasons on Mars in a simplified fashion.

 

Mars Fig 1.jpg

 

Note the eccentricity in the orbit, such that Mars varies greatly in distance from the Sun, from 249M km at aphelion to 207M km at perihelion. Consequently, the distance from the Earth at closest approach varies from 54 – 103M km.  Thus, we can have an apparent size for Mars at opposition from about 13 to 25 arcsecs.  Note also that the northern summer on Mars is near to aphelion, while the southern summer is near perihelion.

 

Coincidence of dust storms and close oppositions

 

A key thing that interested me was the interaction of the orbit with the season for dust storms, which I find fascinating to image and measure, but for many people, can risk spoiling a perfectly good opposition, especially when an encircling or global dust storm develops* (Fig. 2). 

 
Mars Fig 2.jpg

 

There are two excellent resources: a compendium of dust storms from 1886-2022 at ALPO by Jeff Beish, and McKim, R. (1999:  “Telescopic Martian Dust Storms: A Narrative and Catalogue,” Memoirs of the British Astronomical Association, Vol. 44, June 1999) for looking at the incidence of dust storms in relation to Ls and the seasons on Mars. 

 

The dust storm season broadly starts at Ls 180 and ends at Ls 330 (Fig.3).  Essentially, this is around perihelion and the southern summer solstice.  In other words, if you get a close opposition, you are also more likely to get dust storms.  Indeed, the very closest oppositions, occurring around perihelion, are bang in the middle of the period from Ls 206 – 308 when, according to Jeff Beish’s latest stats, you are most likely to get encircling or global dust storms**.  Either you must learn to love dust storms, or you must prepare for possible disappointment (noting that the big ones are not that common – 14 in 136 years)!

 

Mars Fig 3.jpg

 

How does apparent size interact with observer location on Earth?

 

Bad news, northern hemisphere folks:  close oppositions tend to occur with lower altitudes for you. The reverse is true for us in the southern hemisphere. Below is the graph showing this (Fig. 4). I used Stellarium to calculate maximum altitude above the horizon for an observer at 35S (this corresponds to Canberra, the centre of the known Universe), and for one at 40N (roughly through the middle of the continental USA, southern Europe, etc.).

 

Mars Fig 4.jpg

 

How do apparent size and altitude interact?

 

Bringing it all together, you get the graphs below***, which show that we in the south tend to get more high, large Mars oppositions than folk in the north (six vs three in the period 2003-2035). But for everyone everywhere it is lean pickings for the next four oppositions. But if you want to capture a big Mars, high up, you will have to wait till 2033, and come to the southern hemisphere.

 

Mars Fig 5.jpg

 

(edited to correct misplaced axis noted by Ray in Post #8, thanks!)

 

Before deciding to emigrate to Australia, though, bear in mind that some folk (e.g., Darryl - Kokatha Man) have overcome the challenges of low altitude to get excellent images at or below 30°.  (I myself, in Canberra, found my images peaked this last opposition at poor/mediocre, because of opacity issues - lots of high cloud - or poor seeing exacerbated by imaging through two thicknesses of atmosphere). Note also that the imaging gods have not been universally kind to us southerners: we in the south also get most of the very small and low oppositions (5 vs 1!), and the rest of the decade (2025 and 2027 oppositions) looks distinctly dreary for us.

 

I hope all this it is of interest to some.  Like many of us, I am self-taught, blundering about in the literature trying to make sense of stuff, so please let me know of any errors before I get my photobooks made up towards the end of February!

 

Regards

 

Mark

 

*I have noted previously that this leads imagers to go through the “Five Stages of Martian Dust Storms: Denial, Anger, Bargaining, Depression, IR filters”.

 

**Defined by Jeff Beish as follows.   Encircling: Dust storm with major axis that completely encircles either one or both hemispheres of Mars. Global: entire planet covered by dust.  Between 1886 -2022, there were 11 Encircling, and three Global dust storms (the latter in 1971, 2001, and 2018).

 

***I defined small as below 18 arcsecs, and low as peaking below 40° of altitude. You may have your own definitions.


Edited by Lacaille, 06 February 2023 - 03:55 PM.

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#2 Oddyse

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Posted 05 February 2023 - 05:48 PM

   As much as you know about Mars I would take your word about Australia too! Regards from Tennessee, USA


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#3 Lopper

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Posted 05 February 2023 - 06:41 PM

“Five Stages of Martian Dust Storms...”

 

I had not heard that one before. I love it! Thanks for posting, Mark!


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#4 Brianm14

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Posted 05 February 2023 - 08:19 PM

Brought back memories.  Had the great good fortune to travel to Australia six times between 1999 and 2002, spending over six months total there.  

 

Was privileged to be introduced to the Southern sky in detail by a mariner who first learned it in during WWII.  (He used this knowledge to navigate his lifeboat after his warship was torpedoed.)  He taught it to me the way he taught it to “the new lads” during evenings on deck.  The memory still catches me out.

 

Wonderful sky, wonderful people, wonderful country.

 

CS,

 

Brian


Edited by Brianm14, 06 February 2023 - 02:33 AM.

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#5 Foc

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Posted 05 February 2023 - 09:22 PM

Great work Mark!  Good info in nice crisp graphics.  Nice to know that in Au we are the best located for seeing dust storms on Mars.

 

Would make a good review piece or perhaps an additional selling point for you upcoming Mars (with the free Venus section) Photobook.

 

Given the long term benefits for imaging planetary opposition in living in Australia (if you can find good and dust penetrating seeing;..future chapter?) now just need to further extend our longevity to take advantage.


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#6 BQ Octantis

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Posted 05 February 2023 - 09:44 PM

Bloody oath, mate! There's nothing like Australian skies anywhere else on Earth.

 

I also gave the gift of Australian AP a few years back, but mostly DSOs:

 

sml_gallery_273658_7587_483958.jpg

 

sml_gallery_273658_7587_132249.jpg

 

sml_gallery_273658_7587_399469.jpg

 

Had I had your aperture, I might have had more than just a single page of planets to share. But I did capture that late 2020 Martian storm soon after I published…and that was a storybook unto itself! Not sure I had the resolution for a full picture book, though…

 

BQ


Edited by BQ Octantis, 05 February 2023 - 11:24 PM.

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#7 Ashman

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Posted 06 February 2023 - 06:22 AM

Great work Mark and it is also enlightening!


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#8 KiwiRay

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Posted 06 February 2023 - 02:47 PM

Nice summary, Mark! I especially like Fig. 5, which puts the key information in a single, easily digested format. You do have the yellow vertical line defining low vs high in a different place for the northern latitude - 2035 would be on the "high" side for northerners if you used 40° like you did for the south. Mars won't get that high for me here at 47.6°N, but that opposition should still be a very good one for us. 2033, on the other hand, will be terrible.


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#9 Lacaille

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Posted 06 February 2023 - 04:11 PM

Thanks for the likes and kind comments. Lopper, I came up with the five stages during the 2018 global dust storm when there was a lot of frustration about!

 

Nice to know it brought back fond memories of Oz for you Brian.

 

Ross, in terms of merch, I am thinking teatowels with the graphs on them?

 

BQ, that looks like a superb photobook. I got the idea from Ross (Foc), who lives nearby and has been doing an annual one of his astophotos for some years. We both find the manufacturers struggle a bit with our images - we are operating at about 100-200 KB images for planets, whereas the crappiest selfie these days will be in the order of 12 MP.  Jupiter in particular can look very washed out, by comparison with the screen appearance, and the software often yells at you that your image is too low quality as you assemble the book.  Quite demoralizing. 

 

BTW, BQ, I went back and looked at your thread on the 2020 dust storm around Valles Marineris - that was a great thread, especially the way you added updated images, and many others contributed. I also liked your insertions of images from dust storms in the Red Centre to give some sense of what it must be like.

 

Ray, thanks for the pick-up; the error must have occurred when I was moving things around in PowerPoint. I have corrected the graph with acknowledgements!

 

Regards

 

Mark


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#10 BQ Octantis

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Posted 06 February 2023 - 05:41 PM

Printing planets is indeed a major challenge with such few pixels. At 200 dpi, even my largest images are just a 2-3 cm across—definitely not a full page spread like that Carina or Omega Centauri! But it was hard-won data, so I even tossed in my Neptune (that was maybe 3-4 mm across). No one seemed to complain, though.

 

Ah, the 2020 dust storm…such fond memories. It was fun being the only ones seeming to document the 15-year-cycle event while the rest of the world was mesmerized by…some sort of circus, a half a world away. I even came across our page shared on Twitter by some astronomy enthusiasts excited by our work. I'm curious where in your dust storm diagram that 15-year cycle falls…

 

BQ



#11 Lacaille

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Posted 06 February 2023 - 06:14 PM

I'm curious where in your dust storm diagram that 15-year cycle falls…

 

 

Ah yes, I meant to check that - went into WJ just now and, if it started on 12 Nov 2020, it would have been at Ls 313 deg, roughly 8 o'clock on Fig. 1 and inside the dust season, with the southern hemisphere in what passes for high summer on Mars.

 

Regards

 

Mark



#12 Tulloch

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Posted 06 February 2023 - 06:44 PM

Printing planets is indeed a major challenge with such few pixels. At 200 dpi, even my largest images are just a 2-3 cm across—definitely not a full page spread like that Carina or Omega Centauri! But it was hard-won data, so I even tossed in my Neptune (that was maybe 3-4 mm across). No one seemed to complain, though.

When I print mine, I just resize the planets in Photoshop and the photobook software stop complaining. I print mine in 8x11" HD Hardcover layflat option on 440gsm Fuji Film photographic paper, and as long as you brighten up the images they come up really well.

 

They currently have a deal for a 20 page hardcover book for $39.

https://www.photoboo...remium-lay-flat

 

Attached is my 2022 book (image quality reduced for CN filesize).

 

Andrew

Attached Files


Edited by Tulloch, 06 February 2023 - 07:08 PM.

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#13 kevinbreen

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Posted 06 February 2023 - 07:05 PM

You should see my annual send-to-the-extended-family bound tome. It very much resembles the Buke Of Genesis. No photographs, no evidence.

Well done
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#14 Lacaille

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Posted 06 February 2023 - 07:41 PM

When I print mine, I just resize the planets in Photoshop and the photobook software stop complaining. I print mine in 8x11" HD Hardcover layflat option on 440gsm Fuji Film photographic paper, and as long as you brighten up the images they come up really well.

 

They currently have a deal for a 20 page hardcover book for $39.

https://www.photoboo...remium-lay-flat

 

Attached is my 2022 book (image quality reduced for CN filesize).

 

Andrew

Yes, that's who Ross and I use, and with exactly that approach of downscaling until the whingeing stops.  Your book looks really nice.

 

Mark


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#15 BQ Octantis

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Posted 06 February 2023 - 10:04 PM

Attached is my 2022 book (image quality reduced for CN filesize).

I had a rare wave of aperture envy…


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#16 N-1

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Posted 07 February 2023 - 04:27 AM

Glad to read this. We're losing Jupiter and (a bit later) Saturn so this is something to look forward to.


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#17 CPellier

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Posted 07 February 2023 - 05:09 AM

Excellent summary :) 

Another factor to include is meteorological phenomena of the white clouds. They are way more interesting when Mars is in its boreal spring/summer, so when it is near aphelion. This for me conterbalance the small diameter. Blue images can be stunning past Ls 70.

Coincidence of dust storms and close oppositions

 

A key thing that interested me was the interaction of the orbit with the season for dust storms, which I find fascinating to image and measure, but for many people, can risk spoiling a perfectly good opposition, especially when an encircling or global dust storm develops* (Fig. 2).

Finally I see that I'm not alone :) 

My personal stages of Martian dust storms are "surprise, expectation, excitation, fascination" :D 


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#18 Lacaille

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Posted 07 February 2023 - 04:23 PM

No, you’re not alone Christophe!

That’s interesting about the aphelic oppositions! Haven’t experienced one of those since I began the hobby. Thanks for the insight.

Mark

#19 Jeff B1

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Posted 09 February 2023 - 04:05 PM

Mark, credits for defining dust activity on Mars, as you state in post #1, must include those who formulated the ideas or definitions; we, ALPO and others, came up with it were ALPO Mars Recorders (Coordinators) and several professional planetary astronomers, i.e., Chick Capen (Lowell), Leonard Martin (Lowell), Rich Zurek (JPL), James Tillman (U.of Wa), et al, and have lasted a test of time now for several decades.  One may digest or gleam this from: https://alpo-astrono...ing_Mars_6.html  We all worked on this for years and hopefully will be vindicated in time.


Edited by Jeff B1, 09 February 2023 - 04:07 PM.


#20 Lacaille

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Posted 10 February 2023 - 01:43 AM

Hi Jeff,

 

Thanks very much for the excellent reference (now bookmarked!).  I have however just tried to correct my original text accordingly, only to find that the opportunity to edit the post has lapsed.  I trust that your post at least serves as a correction to the record. 

 

Regards

 

Mark


Edited by Lacaille, 10 February 2023 - 01:45 AM.



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