Currugated Mars...what's going on?

[WayBig]

Do I decided to try Space Cowboy's trick of stacking Barlows, but my resulting processed image has a corrugated look to it as soon as I tweak any wavelets. It doesnt look like normal noise which gives a less random pixelated effect

Gear used: Skywatcher 250 auto-dob, tal x2 + tal x3, SPC900 webcam

The best 1000 frames split out of the avi by PIPP and loaded into Registaxx. 970 of them stacked.

The attachments are

the JPG is the stacked "corrugated" image

the TIFF is the stacked image with no post stacking wavelet processing

the bmp is a sample frame from the avi

Does anyone know what would be causing this, and how to avoid it?

Also, does anyone know how to get the colour back into the image, it is very "washed out", possibly due to using too high a focal length

002.bmp

000.tif

[Space Cowboy]

What frame rate did you use Chris?

[Moonshane]

it looks like the canvas size is wrong (joke!!).

[WayBig]

What frame rate did you use Chris?

10fps,

I didn't get that effect in the avi when using the x3 barlow and extension tube, just when processing the avi with the extra x2. I was wondering if that was just a step too far for the spc.

[Cloudwatcher]

Also, does anyone know how to get the colour back into the image, it is very "washed out", possibly due to using too high a focal length

If you have Photoshop try using Auto Color then the Hue/Saturation tool to get the colour you require.

Some blurring plus use of the Dodge and Burn tools will make it look a lot better.

[cgarry]

Did you need to increase the gamma for the capture with the stacked barlows because the image was dim? It looks to me like noise from the camera made visible by using a high gamma setting.

Cheers,

Chris

[WayBig]

If you have Photoshop try using Auto Color then the Hue/Saturation tool to get the colour you require.

Some blurring plus use of the Dodge and Burn tools will make it look a lot better.

Crikey, i've not got Photoshop, but that looks great. Is that my image did you use the tiff file, what did you do to it in PS, I'll see if I can do something similar in a different tool, maybe gimp.

Perhaps it's a registaxx issue

Thanks

[JamesF]

Yup, I'm in agreement with Chris. It looks like camera noise induced by excessive gamma settings or too much gain.

James

[WayBig]

Yup, I'm in agreement with Chris. It looks like camera noise induced by excessive gamma settings or too much gain.

James

Thanks, the image was dim so I remember increasing some settings. What would be a better way to do achieve a brighter image at high focal lengths. Would it be better to play with the exposure or brightness (I'm using sharp cap) and lowering the gain?

Cheers

Chris

[blusky]

Good seeing is key. Patience, as usual

[Space Cowboy]

High gamma would explain the washed out appearance. I always kept gamma at 0 with the webcam and controlled brightness using gain and shutter speed. The brightness setting is only for on-screen brightness this does not effect the captured level.

If gain needs to be above 80% you need to stack plenty of frames, so for a 6 min avi at least 1000-2000.

I suspect your 3x + 2x stack has produced a higher focal length than the theoretical f30 level...maybe nearer f40?

You should probably have exposure set to its slowest setting for this fl.

[JamesF]

Let me find the settings I used for my recent Mars images. They should make a reasonable starting point.

James

[JamesF]

Here we go:

Frame Rate (fps)=10.00
Colour Space / Compression=I420
Exposure=-4
Brightness=57
Contrast=32
Saturation=0
Gamma=0
ColorEnable=255
BacklightCompensation=0
Gain=15

That's with a 2.5x barlow in the optical train. You're spreading the light over a much larger area, but I'm working with a 127 Mak rather than a 250 dob, so the gain setting may not be too far out.

I'm not sure I'm using the best colourspace/compression setting, but I can't find any definitive information on that.

James

[JamesF]

It's amazing what you can find when you get the right search terms into google

Use the YUY2 codec rather than I420.

James

[WayBig]

It's amazing what you can find when you get the right search terms into google

Use the YUY2 codec rather than I420.

James

James, many thanks for spending your time on this. As with many things, knowing what question to ask is the key to getting the right answer...now I'll try to understand your answer

[michaelmorris]

I concur that 'washed out' low contrast image and linear artefacts looks very much like the Gamma setting was way too high. Personally, I hardly never touch the gamma setting and leave it at zero.

[WayBig]

I have some more data here from last night, the first image looks OK and has these settings

[Philips SPC 900NC PC Camera]

Frame Divisor=1

Resolution=640x480

Frame Rate (fps)=10.00

Colour Space / Compression=YUY2

Exposure=-8

Brightness=69

Contrast=37

Saturation=0

Gamma=0

ColorEnable=255

BacklightCompensation=0

Gain=63

The second image is corduroy, and had the following settings

[Philips SPC 900NC PC Camera]

Frame Divisor=1

Resolution=640x480

Frame Rate (fps)=10.00

Colour Space / Compression=YUY2

Exposure=-7

Brightness=69

Contrast=63

Saturation=100

Gamma=6

ColorEnable=255

BacklightCompensation=0

Gain=63

The differences being

- exposure one point difference, trying to get a brighter image, such a small difference I wouldnt expect it to result in codruroy

- contrast increased from 37 up to 63

- saturation, big change from 0 up to 100, not sure why I did this or what the preferred setting is, but could this be responsible for the corduroy

- gamma, increased from 0 to 6, again not sure why, I think I was trying to get some colour and brightness into the image.

So....opinions required on what is causing my stripes...is it the saturation?

Supplementary question, the brightness of the image during capture went from looking too dim, up to looking too bright with just one point change in the exposure. What should I be tweaking to fine tune the brightness of the image?

Thanks again

[JamesF]

I forget which way the numbers for exposure, but I start with it fully to the right, then have saturation, brightness and contrast roughly in the middle, and turn the gain right down as far as I dare. When I'm capturing images of Mars I can only just make out the ice cap some of the time.

It's better to have a longer exposure and lower gain than the other way around.

James

[blusky]

A surprisingly good seeing of Mars tonight, even through a thin hint of cloud.

The first attached image has been though a very light wavelet processing, but shows plenty of detail. Any idea what features we see tonght? Can't match them back to the map of Mars.

Compare to an earlier second image with a bit more heavy processing.

PS Visually the scope was a touch out collimation, but I like the contrast on the 1st image better!

PPS My gratitude to the (owners? lessors? of the) tall construction crane in the distance, a bright spot light of which I use to fine-align the cross-hair of the viewfinder. This allows me to always place the planet in the FOV of the webcam, with a 3x or even (attempted twice) stacked 6x Barlow.

[todd8137]

looks like to many barlows

[JimStan]

Cloudwatcher, did you use "directional blur" to eliminate the corduroy effect ? I have found that that tool, and applying one or two pixels of blur 90degrees away from the direction of the lines will all all but eliminate the lines without affecting the definition of the data visually in the least bit ! Might be worth trying. Your results , btw, are fantastic !

Jim S.

[WayBig]

looks like to many barlows

Yeah probably, I'm hoping to work out a way to cope with that many barlows

[WayBig]

Wow - thanks for all the advice guys...tonight is very good seeing here and I've managed to get a few avis with my new camera settings...SO MUCH BETTER.

This is a quick process of an avi taken with a x3 AND x2 barlow. About 1700 frames stacked, no resizing. I'll do a better process tomorrow to try to get rid of some of the lines near the edges, but the detail in here is so much better than I have been getting, and NO corduroy. Thank you, thank you, thank you.