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  #1  
Old 20-07-2018, 03:47 PM
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Stonius (Markus)
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First attempt at Mars

The wind was blowing a gale and it was bouncing all over the place, but for a first effort at this planet I'm reasonably happy.

Hoping to get better in more moderate seeing conditions. I'll need to get better at combining the RGB channels. Finding the planet has the correct color, but the poles have the wrong color cast from different channels bleeding over. If I was *only going to do Planetary, I would have gotten a OSC, but this is also going to be my guidecam when I get good enough to play with that stuff too.

2:20am, Weds 18
R 5.9ms
G 3.3ms
B 32.4ms
All at gain 200 on an ASI 290
RC10 with Powermate 2x

Sorry I can't remember how long the actual sequences themselves were. Most likely 120 or 180 seconds.

Any comments or suggestions welcome (other than, uh, try shooting in better seeing conditions, when there's not a dust storm on Mars, or when it's not blowing a gale!!)

Thanks guys.

Markus
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  #2  
Old 20-07-2018, 03:52 PM
GOTO (Geoff)
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Wow, first attempt? Well done.
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  #3  
Old 20-07-2018, 07:59 PM
Mickoid (Michael)
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That's the best detail I've seen on Mars in this forum of recent weeks, so you've done really well. You picked a difficult time to make it your first go. Scientist's prediction on the NASA website think the dust storm may last for months! So much for it's closest approach to earth in 15 yrs. We're getting some of the best views of an orange blob you'll ever see.
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  #4  
Old 20-07-2018, 08:18 PM
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Stonius (Markus)
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Quote:
Originally Posted by GOTO View Post
Wow, first attempt? Well done.
Thanks. I have had three or four misadventures with jupiter so far, but yes, first time on this target. Partly because of timing, partly because of new equipment that I'm madly trying to get the hang of.

Can't wait to give it a go on a still night with good seeing!!

M
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  #5  
Old 20-07-2018, 10:44 PM
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Stonius (Markus)
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Quote:
Originally Posted by Mickoid View Post
That's the best detail I've seen on Mars in this forum of recent weeks, so you've done really well. You picked a difficult time to make it your first go. Scientist's prediction on the NASA website think the dust storm may last for months! So much for it's closest approach to earth in 15 yrs. We're getting some of the best views of an orange blob you'll ever see.
I was trying to pull as much detail from the images as possible to see what the new setup is capable of; to try and get a feel for the 'limits', I guess. To be fair, I never looked at the great red blob through the eyepiece, so I haven't exactly been working towards an image that was true to what was there on the night - all I saw was black and white!

85% of the visible detail was in the red channel, maybe 15% in the green. Apart from the poles, the blue channel was featureless - which brings me to an interesting question.

Mars is red, right? But the red channel needed another two thirds as long to expose correctly when compared to green (I guess the camera's greater response in the green spectrum helps here) but then BLUE? Exposures were ten times longer than the green channel! wow. Not sure if that's normal or not. I guess the chip is less sensitive in that area, plus the object itself itsn't reflecting as much light in the blue region of the spectrum, but wow!

I did grey card tests the other day with these filters and the results were not what I expected either, but I'm going to repeat them before I say what happened just in case I got something wrong.

Now I'm wondering if I should vary the exposure of the other channels at all. I'm trying to get the best SNR per channel, but with the lucky imaging thing, you lose the advantage of short shutter speeds. If I was shooting OSC, I would have one exposure for all three colours in the bayer matrix, wouldn't I? But then I wonder what happens to blue data that is ten times darker than the green channel in post processing. It must be harder for the algorithms to work on dark data. Sure you can just shoot it with more gain for same shutter speed, but it's the same thing really, isn't it?

So which is it? Is it shutter speed or noise that wins? or can you do like with Deep Sky stuff and shoot Luminance? That could give an even brighter (faster, therefore sharper) image and let the RGB channels be relatively noisy?

Sorry, rambling now.

Cheers
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  #6  
Old 22-07-2018, 01:06 PM
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Great effort.
Just to get a planet in the field of view is a big deal in my book.
Alex
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  #7  
Old 22-07-2018, 06:16 PM
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That's excellent Markus.

Feel like I can comment on a planetary image now as I had my first go at it this week - a fuzzy disaster. Think I'll leave it to the pros.
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  #8  
Old 22-07-2018, 10:02 PM
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Stonius (Markus)
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Originally Posted by ChrisV View Post
That's excellent Markus.

Feel like I can comment on a planetary image now as I had my first go at it this week - a fuzzy disaster. Think I'll leave it to the pros.
Thanks Chris. I have to admit if I looked at the raw footage I got I'd say the same about my own stuff, so don't give up on your own footage until you've given it a good go through post-processing. I was suprised to get anything at all from that night. From that session I'd say at least 50% of the detail came from up in post. I regret not having thrown an eyepiece on there before I went to bed now, just to see what it actually looked like visually but I was too tired and was busy conducting another test on 47 Tuc. But anyway these RC scopes are not great for visual because the central obstruction is too big so I don't know what that I would have seen anyway.

Though I do find something really exciting about being able to capture data and then take it away and manipulate it to reveal details that you could never have seen with your naked eye. It's kind of like light amplification astronomy, only with a huge time delay. I'm continually reminded of a guy I used to know who worked in video forensics who did similar stuff - teasing out details from grainy security cam footage to find crims, only he was, you know, catching bad guys.

Quote:
Originally Posted by xelasnave View Post
Great effort.
Just to get a planet in the field of view is a big deal in my book.
Alex
Thanks Alex :-) Reading stuff here has helped a lot. There was a thread only a few days before I went out that gave me some ideas of things to watch out for. I made sure my finderscope was spot on so I didn't have to just rely on go-to's, for instance. and started wide and narrowed in to a smaller field at the start of the observing session; Wide EP, Narrower Crosshair EP, replace EP with Camera, confirm target and then attach powermate, checking finderscope alignment along the way. It's a fiddly buisness this astronomy thing!

Cheers and thanks guys :-)

M
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  #9  
Old 23-07-2018, 11:01 AM
sil
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Good detail there. Did you use Winjunos to derotate the colour channels before combining? 3min is roughly a limit to avoid planet rotation causing detail loss. Roughly. It does seem skies are clearing on Mars, my weekend go was noticably clearer than mid last week and clearest I've noticed in several weeks. Just keep at it while its big and bright and clouds behaving before it drifts away again to make things harder.
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  #10  
Old 23-07-2018, 02:26 PM
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Stonius (Markus)
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Not yet. Thats the next bit of the learning curve, along with pixinsight for DSO's.

There was so little detail in the blue and green channels that I'm not sure it would have made much of a difference, but I'll definitely give it a go when I have some worthy data.

Cheers, M
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