I have had an interesting "observation" over the past week or so. As most of you here already know, Mars just isn't going to be rising very high this opposition - a maximum of 28 degrees for observers at 40 degrees North, like myself. And it won't reach culmination until after Midnight, so we're observing it even lower down.

I observed it earlier in the week at about 17-19 degrees above the horizon; later in the week it rose earlier and I was able to observe later, so I saw it between 22-25 degrees. I was able to make out Syrtis Major and Minor, which sort of looked like raccoon eyes looking left. Yesterday I was able to just make out the albedo feature near Utopia on the other side.

But something else I've been seeing is bizarre. I've been seeing Mars lit up in red, white, and blue. And it wasn't even Memorial Day! It was as if I was seeing chromatic aberration in my scope. But that isn't possible, as I was observing with a Mak, where chromatic aberration is basically non-existent. I thought I was going nuts, but at an outreach event last night, someone else saw the same thing I was seeing. What the heck was going on here?

We started hypothesizing. Maybe the meniscus was introducing CA the way an achromatic refractor's objective would? Could it be some sort of optical illusion based on the eyes' relative insensitivity to light from the red end of the spectrum, and the white and blue was some kind of compensatory effect? Or could it be atmospheric effects from Mars being so low in the atmosphere - that the atmosphere itself was acting as a lens?

It turns out it was the latter, a phenomenon known as atmopheric dispersion. This is where the thickness of the atmosphere closer to the horizon causes the light to react the same way it would through an achromatic refractor. The atmosphere bends the light differentially, causing the colors to arrive at the scope at different focal points, leading to the colored display. The top of Mars, the part furthest away from the horizon, has the bluish tint, while the bottom has a reddish tint, which is a bit distinct from the actual orange-red color of the planet itself.

 

Wow, that's an interesting report. I have never seen this effect. I'll look for it if the clouds ever depart the mid-Atlantic. It's the same sort of effect that causes the 'green flash' as the Sun sets.

 

Not only is atmospheric dispersion a recognized visual aberration, but just like anything else, where there's a visual aberration, there's a product that will eliminate it - the atmospheric dispersion corrector, natch.

https://astronomy-imaging-camera.com/products/accessories/zwo-adc/

 

I haven't seen the wild colors (I have two Maks) but I have definitely observed atmospheric turbulence (before peak) due to the low altitude of Mars. It reaches about 35 degrees above the horizon here down south (32.84 N) That's great that there's a product for the dispersion. I'll have to put the ADC on my list

Reggie

 

I just noted this thread, or I would have written sooner. Ah well...

I, too, have been noting some wild & wonderful colors with Mars this time. Which I've also deduced is a result of the light plowing through the deeper parts of our atmosphere. Shimmering from deep and dark ruby-red, and reaching a crescendo of bright orange. As I wrote it recently 'up-the-way' - it is like Sirius on acid.

Up here in Podunk we may not be at the best of latitudes for observing the "God of War" - but he's certainly compensated us with a superb light-show!

The colors, dude!

Dave

 

I'd rather not have the colors and be able to see the polar cap. Acid trips are fine for those that want them, but the colors are messing up my ability to see detail, and that, the Dude does not abide.

 

Here was my most recent Mars observation attempt. I think many of you have much better conditions than I do.

Wednesday May 25 2016. 72 degrees, no wind. 3/5 trans, seeing 4/5

Finally got a break from the clouds.

Orion XT8 Intelliscope used manually. 2" 70 25 mm, 1.25" 8-24 zoom, ES 82 6.7 and HD-60 4.5

10:30 to 11:30 pm.

Mars - around 30 degrees - ES 82 mostly. 180X

Filter#12 Saw some indiation of darker areas top and bottom but no other detail

Filter 21 - simialar results

23A - No added detail

No filter - Pale white/orange overall, sort of a melon color. Similar view to #`12 but after a while I got the impression of baseball kind of sticking pattern from top right to bottom left. Maybe a faint glow at top right, perhaps an ice cap.

#56 - no more detail

80A - Pretty blue overall color but no new detail

82A - Similar to view with no filter


I was just happy to be out with a somewhat clear sky.

 

Ed, instead of using all of those filters, what about just getting what I'm convinced is the single best filter there is?

I find that the Baader Moon & SkyGlow filter is a terrific Swiss Army knife of filters, great on all the solar system objects. Mine lives on the end of my diagonal; I never take it off. The first time I used it was on Jupiter, and the Great Red Spot popped right into view, where before I had to observe it with averted vision, mainly through its absence - the little notch in the equatorial belt where it resides.

On Saturn, it helps split the A and B rings to reveal the Cassini Division, and lets me see banding on the surface. On Mars, it lets me see the surface albedo features easier. And on the moon, it removes glare, making it easier to see more detail. I don't know how it does it, but it does it well.

 

Will consider that for future purchase. Right now the till is nill for adds and upgrades.

 

I saw Mars at Opposition (22/5/16) around Transit (01:06 BST) at about 193x with a 130mm reflector. I could make out some surface detail (obviously nothing like these VPA pictures) even though it was at 15.9° in altitude from my latitude.



Later,on the 29th, now at 225x and using a Baader Neodymium filter, I could make out even more of the maria, although the northern polar cap was only hinted at.



In later sessions I’ve watched it phase and get smaller. I have seen more of the polar caps at around 250x and 257x and found #8 Light Yellow, #11 Yellow Green and #82A Light Blue filters helpful for seeing surface features. If I'm lucky, the weather may let me get a few more observations in, even if they're virtually twilight.

 

I just remembered the last time I observed Mars (5/7/16) I could definitely see the northern polar cap without any filter.



I observed from around Transit (21:32 BST) for about an hour. The transparency wasn't good and I dropped the magnification down to 200x and eventually to 150x using a 6mm Hutech Abbe orthoscopic with no filter.



Even at only 150x the polar cap was very distinct and I could still see maria.

 

I was lucky and got to view Mars a bit tonight (22:15 BST, 15.3°S, altitude 14.9°, Libra) but the transparency wasn't good and I only saw fleeting detail at 150x with a 6mm Abbe orthoscopic and at 257x with a 7mm Celestron X-Cel (with Barlow) and a Baader Neodymium filter . I could see the phase though.

 

I got a look at Mars on Friday night. Azimuth 11.1°, 15.2° altitude (Libra). The transparency wasn’t great but it’s one of the last chances I’ll probably get at Mars. At 250x I thought that I could see Syrtis Major and a flash of the Hellas albedo feature. Mars seemed an unusual yellow-orange colour although I was only using a Baader Neodymium filter. The phase was quite distinct.

 

Thank you for the great report, MTN, your describing the 'yellow-orange' colour matches what I've been getting from 44.29° latitude as well - to an extent. However I've also been noting a deep-red also. This variability may indicate the 'seeing' on different nights? I'm sure I don't know an exact causation, only the effects of something happening up there.

This parade of different colours is what has really been the most fascinating aspect of this opposition for me. It may not be in an ideal latitude for close-up viewing - but this shifting of colours has made it outstanding nonetheless!

Enjoy your observations, MTN, and keep those great reports coming.

Dave

 

Cheers Dave. I was pleasantly surprised to catch Mars on Friday, although low cloud eventually came in to end observing it. I'd just changed eyepieces to try for 281x as well. I'm still getting an 0.52mm exit pupil for that magnification, it's good for the Moon, but I thought I'd give it a shot at Mars after observing at 250x for a while. Unfortunately, as I was trying to find Mars in the small 8mm TeleVue Plossl eyepiece, the clouds came.

I agree, it has often been a deep red, although this is the first time since early in the Opposition I've seen this yellow-orange colour and even then it didn't seem so apparent. I am guessing the latitude has something to do with it, at 52° 27' I’m observing Mars at anything between around 14° and 18° altitude. Luckily, I'm at a high geographical altitude, and being on the edge of the greenbelt, not a great deal of light pollution especially to my south. It's been unusually wet and damp here though for the time of year and this is affecting the overall transparency. The Sun's out at the moment though ... could bode well for tonight!

 

I managed to get a look at Mars for around 20 mins at 21:30 BST, 9° S, 15.4° altitude (Libra). I observed at 281x which is the highest magnification I’ve used on Mars so far.



Transparency wasn’t particularly good but I could make out some surface albedo features. It was again a yellow-orange colour. The northern polar cap was also visible.

 

Mak, I don't want to rain on your parade, but are you sure you're really seeing the polar cap? The reason I ask is that there is a phenomenon called atmospheric dispersion which, especially when Mars is at such a low altitude in the sky, will make you see things that aren't really there. It fooled me, and I was observing it at about 25 degrees or so!

See my post, #2, above; I also wrote a blog entry about it. See if this bears any resemblance to what you've been seeing:

https://jgroub.wordpress.com/2016/05/26/may-25-2016-mars-part-deux-and-atmospheric-dispersion/

 

Well, I'm fairly sure I am seeing the northern polar cap, it's in the position predicted by Cartes du Ciel and the Virtual Planet Atlas. Also, I couldn't really see the cap around the time of the Opposition itself, although I thought that there were faint suggestions of it. That could very well have been the atmospheric dispersion that you mentioned. Later, a few weeks after the Opposition, the northern polar cap became more evident, although again, that's often the case with Mars as the caps are often easier to see a while after the actual Opposition. There are times when I thought the polar cap was quite visible. I'm observing from a geographical location quite a high altitude above sea level (edge of a glacial valley) and I live in a village right on the edge of the greenbelt. The nearest town is about a kilometre away and I'm several kilometres away from the nearest city. Basically a Bortle Class 3 'rural sky' . In fact, after a couple of streets to the south of me (which I'm higher than) it's mostly farmland until the Welsh Border. Depending on the night I've been observing, I've actually been able to recognise surface features. It is getting more difficult now. I'm pretty sure I saw the Syrtis Major Planum on Sunday night and the white albedo object above it (in my inverted and rotated jpeg from the VPA) which I believe is Hellas Planitia. The northern cap was not so distinct as it has been in the past few days though. At 281x, using a TeleVue 8mm Plossl and a 2.5x TeleVue Powermate I'm getting about a 0.52mm exit pupil. It's probably too high a magnification for the conditions, but I tried it anyway.

 

I got another look at Mars on 18/7/16 around 21:45 BST (Transit was 20:49), 13.3° azimuth, 14.8° altitude (Libra). I was observing at 257x with a Baader Neodymium filter. The transparency was slightly better than the last time I observed Mars. The planet seemed quite sharply defined even at this altitude and the phase was apparent.



This time Mars was more of a deep red colour. Syrtis Major was quite easily identifiable and seemed very well defined, although Hellas Planitia seemed more muted. I thought I could detect the dark Meridiani Planum area as well. The northern polar cap could be seen.