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Mars: Red, ‘White’ and Blue.....

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#26 David Gray

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Posted 13 July 2018 - 10:21 AM

Pete.......glad you got going with Mars.

 

Yes....thing is with that NPR: it’s at the blue-end of the dispersion and we can get a case of an effect being suggestive of the feature it is hiding..........Rather like Saturn’s Ring A where contrast/diffraction effects mimic (‘enhance’) the real features underlying. The apodizer deals with that quite well; and the ADC the Mars-dispersion – to get true-blue for the NP..........grin.gif

 

Edit: got your meaning re the SPC but I wandered off  thinking about the blue at the N. limb.......blush.gif

 

Not an option to lower the fence (I built it.....!) and that height is to screen things from passing undesirables on the back road.  Particularly during more visible daylight Venus etc. work....similarly with bright moonlight - drunken passing undesirables!

 

SM Pro does have some tools to add things such as a custom skyline – trees, buildings etc.  But, for the posting here, simpler to copy/paste/crop in Corel Draw (took minutes)..........!

 

Dave.


Edited by David Gray, 13 July 2018 - 10:45 AM.


#27 Uwe Pilz

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Posted 13 July 2018 - 11:47 AM

Some words about the prismatic dispersion: If you don't have a ADC (which is a very promising tool) you have to use strong filters to see anything reliable at the limb. The most modest one I have is a Neodymium filter, but it is not sufficient for the Mars this low (<20° here in Germany). With a orange, blue or dark green filter the dispersion effect should be eliminated. You don't see, of course, the planet in the integrated light.



#28 azure1961p

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Posted 14 July 2018 - 11:03 AM

Trouble with the neodymium is it ENHANCES the prismatic dispersion markedly.  The red and blue intensifies with this filter. In the past at times its been so bad I'd opt for a written instead, usually red as it sharpens poor seeing results better with less scatter than other written colors. Green and blue, while they do enhance some Martian haze, cap features and certainly a lot on Jupiter, it scatters more due to its wavelength , color contrasts aside.

 

Pete


Edited by azure1961p, 14 July 2018 - 11:13 AM.

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#29 David Gray

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Posted 14 July 2018 - 12:45 PM

Crisping-up the limb with strong filters I have long practiced. In that vein the use of a W#22 (Orange)...... darker/more contrasty than the common or garden (grin.gif ) #21....has proved invaluable for rising dispersion-afflicted Mercury on a fair few mornings. Strangely its close 'neighbours' - #23A & #25  - are poorer for this......

 

The later months of the last Mars apparition very fruitful from 2016 Sept to 2017 Feb thanks to much use of the #22 and the dark red #29.

 

Yes the Neodymium is pretty terrible with low planets (likewise the magentas) – but the ADC – more than being promising – is proving a very effective must.  Certainly an order better than the old Ramsden ‘trick’ and, prior to the ADC, the residual CA in the optical train (Binovu+Amici) of the D-K.  More effective in that I am able to get better hue-differentiation than those Ramsden-style efforts which tended to a more monochrome palette.

 

I’ve seen a couple of comments about the ADC doing nothing for the seeing........well it does indirectly – no magic – as I figured recently when looking at Saturn’s satellites.  After some 15-20 minutes I applied the device and immediately they took on more sparkle.  When we consider them at low altitude: due to dispersion they are no longer point sources but somewhat drawn out into short spectra thus dimmed/more seeing-prone; and of course the ADC puts all that light back to a tighter point.....

 

With planets all that dispersion-jumble when seeing not so good is likewise tidied/realigned making it easier on the eye in my experience.

 

Speaking of the Neodymium: awhile back I added it to the filter combos used on Venus when I found it did a great job with restoring contrast in a bright milk sky.

 

A thread here...... https://www.cloudyni...a-neo-surprise/

 

Got limited opportunity to see that through.....but just today the views bear out my impressions and hoping to follow up better this time......

 

Oh yes! Looking good for clear tonight so have left the Neo on hand to see what the ADC does with the dispersion enhancement of that filter.

 

Dave.


Edited by David Gray, 14 July 2018 - 12:47 PM.


#30 Uwe Pilz

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Posted 14 July 2018 - 02:56 PM

Last night I observed Mars again. The dust storm is for that we learn differentiating very low contrasts ,,,

Again I used my 4 inch refractor at 137x/ADC. I tried different filters, the sketch ist a composition of all the views. The sketched detail was best seen with Neodymium filter (and an additional ADC) , the Orion Mars filter, a green filter and an orange filter. The detail at the south polar cap and the north polar hood could be seen best with green, Blue was rather disappointing. It did not enhance the polar regions.

 

It is easier for my to sketch with graphite epncil. I added slightly color which represents the planet in integrated light.

 

the darker area near the meridian is mare sirenum, the darker bow to the right is syrtis maior.

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#31 niteskystargazer

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Posted 15 July 2018 - 10:01 AM

Uwe,

 

Nice sketch of Marrs smile.gif .

 

CS,KLU,

 

thanx.gif ,

 

Tom

 

 




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