Research Committee Reports & Observations 

Webcam Imaging

Clif Ashcraft‘s Mars Images

Date: Feb 2, 2008 12:04 PM

New Mars image by Clif Ashcraft - Click on image for description.

Email excerpt from Clif Ashcraft

Date: Jan 29, 2008 7:29 PM

Here‘s my latest effort imaging Mars. It may be the best I can do this opposition. On the eveningof January 27 the wind was calm and the seeing average (about as good as it gets here, particularly in the winter). I used a 3x Barlow to couple the camera to my 7.25" f/14 Schupmann medial refractor. Three minute videos were taken at 30 fps and 1/30th second exposure and processed in Registax4 and photoshop. A fair amount of detail was visible in the vicinity of Syrtis Major. I annotated one of the images to identify visible features. Note the tiny feature Moeris Lacus on the east side of Syrtis Major.

Clif

Email excerpt from Clif Ashcraft

Date: Jan 26, 2008 11:28 AM

Last night a light breeze made the scope very jittery, so I could only take 30 sec videos, but the underlying seeing was not too bad. Here's the result of stacking the images from three of these short videos taken within a three minute period. S/N not so good, but lots of detail visible. Nice little water vapor cloud over Ellysium over on the limb at 2 oclock, and the wispy shading into the lighter region on the east edge of Syrtis Major show up well. Mars was only 12 sec across! I was shooting at f/54 and the image below was resized 2x in Photoshop to facilitate stacking.

Clif

Email excerpt from Clif Ashcraft

Date: Jan 24, 2008 6:51 PM

I hooked up the camera and did some more Mars imaging. Seeing wasn‘t too bad, so I got some detail in the Sinus Sabaeus region.

Clif

Email excerpt from Clif Ashcraft

Date: Jan 18, 2008 8:22 PM

I had "decent for NJ" seeing on the night of the 16th (it was 4-5/10), and got the image shown below. My effective focal ratio was f/52. There are lots of identifiable albedo features present in the image, none as well resolved as they were in the images I got at the much closer 2003 and 2005 oppositions. Most of the problem is just lousy seeing in the cold winter air.

This particular webcam (the DFK21 from The Imaging Source) does not have a 320x240 "fat pixel" mode like the ToUcam (even though it uses the same chip), so all my imaging is at 640x480, but this is through a Bayer filter matrix where the red and blue pixels are actualy 320x240 and there are twice as many green pixels. The net result of all that is you really need a different focal ratio for Nyquist critical sampling for each of the color layers: f/56 for blue, f/40 for green and f/33 for red. So, at f/52 I am oversampling (that‘s ok) in green and red but undersampling a bit for blue. It was interesting to look at the red, green and blue layers of the color image in Photoshop. When I did I got the result shown in the second picture. Note that no alias artifacts are visible in either the red or blue layers but something funny is going on in the blue layer (note the fringes). I am not sure whether this is truly aliasing resulting from undersampling or something related to overprocessed image noise.

Clif

Email excerpt from Clif Ashcraft

Date: Jan 15, 2008 12:18 PM

Here is an image I got on the evening of January 9 at 10:48pm using my DFK21 camera coupled to the 7.25" Schupmann with a 3x Barlow giving about f/48 which I think is optimum focal ratio for this one- shot color camera using the same chip as the old ToUcam. The chip has a Bayer filter matrix and 5.6 micron pixels. Mars was near the meridian at the time I took a 3 minute video at 30 fps and about 1/100th second exposure. I was able to bring out more of the surface albedo features using Gaussian wavelets in Registax4 and trapping most of the noise in wavelet 1 which I then disabled. The image is a stack of the best 1950 frames from the video.

I have indicated the old style names of the features I have identified. Strangely, Nix Olympia was not prominent in this image and I am not sure I can identify it. The region around Solis Lacus has been considerably rearranged by the dust storms since the last opposition.

Seeing has been very poor and I have not been able to resolve nearly as much detail this opposition. Not helped much by a 14 arc-sec diameter Mars at this not very favorable opposition.

Clif

Email excerpt from Clif Ashcraft

Date: Jan 9, 2008 2:18 PM

Attached is a montage of 8 images of Mars obtained last night (Jan 8, 2008) under very windy, poor to average seeing conditions using DFK21 one-shot color camera coupled to 7.25" Schupmann Medial refractor using a 3x Barlow lens. Effective focal ratio was f/48. Still not up to the quality of images obtained in 2005, but better than I have done this opposition so far. At least Solis Lacus is recognizable.

Clif

Email excerpt from Clif Ashcraft

Date: Dec 31, 2007 11:34 PM

Just came in from an imaging session with my DFK21 webcam coupled to my 7.25" Schupmann with a 2x Barlow. Seeing was around 3-4 on a scale of 10. Focal ratio about f/33. I was able to shoot at 30fps and 1/218sec exposure. Took three videos of 3 minutes duration giving 5400 frames each. Processed in Registax 4. Each image is the stack of the 1000 best frames. North is up.

There‘s an interesting light area extending from Elysium to the northeast which may be a dust cloud. Color is similar to surrounding plains, just lighter, so is unlikely to be a water vapor cloud. The dark band in the southern hemisphere is Mare Cimmerium in the west extending to Mare Sirenum in the east.

Clif

Email excerpt from Clif Ashcraft

Date: Dec 30, 2007 12:08 PM

I finally got a reasonably clear night for imaging Mars last night. The seeing was pretty bad, so I used it as an opportunity to try out my Baader IR-pass filter. Seeing is less damaging to high resolution imaging in the infrared than it is in the visible. My plan was to use my normal NIR blocking filter to take a one-shot color video of Mars with my DFK21AF04 camera (uses the same Sony chip as the ToUcam but is better on high speed uncompressed video imaging over firewire) and use that image for the chrominance part of an LRGB and to use my Baader NIR bandpass filter to take an image to use for the luminosity part. At 8:12pm I took a two minute video through the NIR blocker, at 8:16 and 8:18pm I took 2 two minute videos through the NIR bandpass, and at 8:21pm I took another two minute video through the NIR blocking filter. The DFK21AF04 camera saves a raw un-debayerized video, and Registax4 has its own debayerizing routine (actually better than the hardware one in the camera). I processed all four videos in Registax4 and saved them as bitmaps. After I had done the processing I noticed that the seeing was a bit better, so I took a three minute video through the NIR blocking filter at 9:19pm and processed it the same way I did the other four. I loaded the first four bitmaps into Photoshop and combined the first two as one LRGB image and the second two as the other. This gave me two LRGB images, one having a luminosity layer taken at 8:16pm and the other at 8:18pm. All four bitmaps and the two LRGB images that resulted from them are shown below in a montage of all the imaging I did last night along with Starry Night simulations. The lower row is from the one-shot color image taken from the 9:19pm video. None of the images are much to brag about, however I believe it does show the improvement obtained using the NIR image as the luminosity for LRGB imaging during poor seeing conditions. If the seeing ever gets better, the image taken in shorter wavelength visible light only (smaller Airy disk) should be better than the one taken with the infrared image as the luminosity. North is up in all of the Mars images and the simulations. I also attach the spectral response of my camera with the response of the Baader filter and the combined response superimposed. The small, unannotated image of Mars is the one from the NIR video taken at 8:18 before changing it to a greyscale image. Note the pinkish color from the broader response of the red pixels in the camera to NIR passed by the filter. This is an infrared false color image where the red represents wavelengths from about 650 to 1100 nm but predominantly around 700 nm, and the blue represents an average longer wavelength band from about 800 to 1100 nm peaking at 850 nm. The green represents a broad band of wavelengths from 650 to 1100 nm but peaking at about 850 nm. The predominance of the NIR going through the red filter on the chip give the pinkish color.

Clif

Email excerpt from Clif Ashcraft

Date: Nov 17, 2007 1:46 PM

Last night when I got home after the meeting I had partly clear skies and Mars was up and in the clear. I took several videos with the new camera on the Schumpmann at f/48. Seeing was average for NJ with a lot of large scale image motion and distortion but with some fine detail visible looking through the seeing. Registax processing was able to recover the detail and give a nice symmetrical image in spite of the seeing distortions. Attached is the annotated result. Hellas is quite prominent this year. Probably has a layer of light dust covering the bottom as a result of the dust storms that threatened the rovers

Clif

Email excerpt from Clif Ashcraft

Date: Nov 13, 2007 5:59 PM

In the wee hours of this Sunday morning I had a nice clear sky, no wind and I had gotten my drive problems worked out for the new Schupmann the day before. I had just gotten a new webcam, The Imaging Source DFK21AF04. This is a color webcam using the same CCD chip as the ToUcam, but with better electronics to minimize noise and high speed firewire connection to the computer capable of up to 60 fps, uncompressed video. I coupled the webcam to the f/14 Schupmann using a 3x Barlow. This gives an f/48 focus because the CCD is a bit behind where an eyepiece focal plane would be. Seeing was poor to average, but I had not had any decent opportunities since I had the new scope mounted in the observatory, so I got busy taking video. I got about 15 videos of 2 minutes duration, 7200 frames each. The camera setting said the exposure was 1/60th of a second, but it must have been shorter since 120sec/7200 is 1/60, and there must be some time between exposures. I could see some details on the computer monitor, in particular I could see the North Polar Cap and Hood with a bit of Mare Acidalium poking through and some dark markings south of the equator. Attached is an annotated image I obtained from one of the videos using Registax4 processing. I have resized the image 2x to facilitate labeling it.
Hope to do better soon if I can get some decent seeing. I will be observing Mars throughout this opposition season using the Schupmann, which is an ideal planetary telescope. I will evaluate the effects of oversampling using my 5x Powermate instead of the 3x Barlow. That will give me around f/80 but may require a longer exposure.

Clif

Email excerpt from Clif Ashcraft

Date: Sun, 27 Nov 2005 02:38:18 +0000

Tonight I took three 4min/30frame/sec videos using a 5" aperture stop on my 12.5" reflector and the 5x powermate. The focal ratio (stopped down) is f/74 and the efl is 372 inches. I also did one determination of r sub zero. It came out 3.14 inches for the 4 minute .avi saved at 8:06pm. I think I better make a 3" stop. Note that all the pictures show the North Polar Hood at the bottom. Syrtis Major is just at the eastern limb, and the prominent feature in the center is Sinus Sabaeus. The lack of the polar hood on the Starry night simulation is because they don‘t do weather... Shortly after the 8:12 video was taken, clouds covered Mars and I quit for the night.

Clif

Email excerpt from Clif Ashcraft

Date: Sun, 6 Nov 2005 17:53:13 +0000

That is about as small as I have ever seen the South Polar Cap. Big storm at the North Pole too. I bet it is snowing dry ice there. Looks like the sand has been blown away in the south half of Hellas.

Clif

Email excerpt from Clif Ashcraft

Date: Thu, 3 Nov 2005 14:43:31 +0000

Did some Mars imaging last night. Seeing was poor to fair. I tried a 5" off axis stop. Images were quite good for the seeing, considerably sharper than images made at full aperture. I am beginning to get some idea of how the seeing (as measured by the Fried Parameter, the largest diameter optic that would be diffraction limited under the conditions) influences the best configuration for webcam imaging. See plot  [above] for variation of rsubzero over time at one observatory site. Note that the average value is around 15 cm (about 6 inches) at this site. It is probably worse here. This suggests that one should setup your f/ratio so that sampling is correct for full aperture, and use subdiameter stops to adjust for the seeing conditions at the moment and only open up to full aperture if the seeing has at least instants of excellent seeing. My system has a focal length of 75" without amplification, so it is f/15 with the 5" stop. Putting on my 5x Powermate, this goes way up to f/75 although it would be f/30 without the stop. I‘ll send you some images later for your judgement.

Clif

Email excerpt from Clif Ashcraft

Date: Mon, 31 Oct 2005 18:22:17 +0000

How did the Mars webcam imaging go at Sperry sunday evening? I stayed home and observed with my 12.5" reflector. I have a set of pictures taken before midnight of the Syrtis Major/Hellas hemisphere. Seeing was poor to fair but major features were well resolved. I had another observing session around 4:30 this morning and got images of the Sinus Meridiane area. Wow! The whole place is obscured by a big dust storm. I don't recognize anything from the second session. The first image below was taken before midnight, the second one this morning around 5am. For reference, the appearance of Mars at these times as illustrated in Starry Night is shown in the third attachment.

Clif

Email excerpt from Clif Ashcraft

Date: Wed, 5 Oct 2005 23:47:12 +0000

I believe I have my first evidence of surface relief topography in a Mars Image, ie , not just an albedo feature. If you look carefully at the image at the indicated location of Olympus Mons, the big volcano appears not just as a lighter spot pasted onto the darker desert background: it has a three dimensional aspect. The right side of the feature, in full sunlight, is lighter than the left side which is on the slope away from the sun, and darker. I am going to try to get several pictures in a sequence as Olympus Mons approaches the terminator and see if the left side darkens into complete shadow and extends as a real mountain‘s shadow should as the sun sets for that locality. If I had stayed on the job until 2:30am or so, I might have captured it last night. Darn...

Clif

Email excerpt from Clif Ashcraft

Date: Sun, 2 Oct 2005 16:06:34 +0000

This morning I had slightly better seeing in Perrineville than yesterday, I would estimate it to be " fair to good" , still a lot of image motion, with the " good" confined to instants of clarity. During these instants, even before processing I could see the division between Mare Cimmerium and Mare Tyrrhenium on the computer monitor while taking the videos. I believe the South Polar Cap must now be nothing but the permanent water ice part, with the CO2 part evaporated. Note the offset location of the North Polar Hood. I believe this is the circular cloud with a hole in the center recently photographed by the Mars Orbiters. This cloud looks like a tropical cyclone, but is evidently just a static cloud formation which forms in this offset location each winter in the northern hemisphere. Mars is noticeably brighter and bigger than when I started regularly observing Mars last month. I have been able to use 1/100th of a second exposures consistently with only a moderate gain setting (about 60% of maximum). Phase is approaching " full" condition which it will reach by the end of the month.

Clif

Email excerpt from Clif Ashcraft

Date: Sat, 1 Oct 2005 18:43:23 +0000

Seeing was only fair this morning, but a bit better than yesterday. I used between 200 and 300 frames in each stack. I have been routinely taking advantage of the RGB shift compensator in Registax to "tune out" atmospheric dispersion. Dispersion shows up as a red border on one side of the unshifted image and a blue one on the other. Registax allows you to shift the red and the blue components of the image up/down/left/right relative to the green component. You do it on the same step where you adjust the wavelet contributions. While this shifter gadget that Cor Berrevoits gave us in Registax is not nearly as good as one can do using the wedge prisms designed for the purpose or what Schupmann users can do by slightly detuning their systems, it is one whole hell of a lot better than not being able to do it at all. Mare Cimmerium is prominent stripe across the image just above the center. The small dark vertical features that look like they are dangling from the edge of Mare Cimmerium are sometimes called the "Fangs of Cimmerium", I guess because they look like a couple of teeth. They show up best in the picture taken at 2:27 am. Hellas is the bright patch right on the western limb at about 45 degrees south latitude. South polar cap continues to shrink. Syrtis Major is just visible on the western limb on the last picture taken at 3:20 am. The bright circular region near the bottom is Elysium and the dark spot below ant to the right of it is Aetheria. The dark area just below the south polar cap is Mare Chronium. The bluish white area just at the bottom of the image is the North Polar Hood. I am surprised how much detail shows up on these images given the fact that the seeing has never been really in the good to excellent range all the time I have been observing Mars. Hopefully, if we ever do get a night where the seeing is a 9 or 10 on the Pickering scale I‘ll be watching.

Clif

Email excerpt from Clif Ashcraft

Date: Sat, 1 Oct 2005 18:43:23 +0000

Here‘s my set of four images of Mars I got this morning from about 3:48 to 4:30. Seeing conditions were not particularly good. I would say poor to fair, but I could resolve some details by using only the 200 best of 2700 frames from each video. In general, the better the seeing, the more frames you can stack and the better is your signal to noise ratio. Syrtis Major is just coming around the west limb and Mare Cimmerium and Mare Tyrrhenium are prominent near the centers of the images. Nodus Alcyonius and Phlegra are the two small smudges just south of the north polar hood at the bottom of the images. South Polar Cap at the top is very small. Hellas is prominent near the west limb above Syrtis Major. 

Clif 

ps: from JPL‘s solar system simulator I estimate that Olympus Mons will be near the terminator tonight at 11pm. It would be neat to see if I can capture its shadow...

Email excerpt from Clif Ashcraft

Date: Wed, 28 Sep 2005 19:12:05 +0000

Seeing was fairly good last night (for NJ) and I got some good images, including some made from the 160x120 and the 640x480 video modes. All images were taken with the 6x microscope objective in place, so the telescope was working at f/36. The attached image gives a comparison of the modes, and a great deal of surface detail. The images were scaled to the same size to facilitate comparison. File sizes were in the ratio 1:4:16. The color speckle noise and the 4x as big file size are big drawbacks to using the 640x480 mode. I was doing approximately 2x oversampling in this mode, and undersampling in the 160x120 mode. To properly match the optics to the lower resolution mode, I should have been using about f/60. The lack of obvious alias effects (moire fringes) in the image suggests that atmospheric seeing was acting as a low pass filter blurring out the high spatial frequency details. There might actually be an advantage of using the lower resolution mode at f/60 if the telescope drive is smooth enough and if a high powered finder is available. Mars would fit the frame, but without a lot of room to spare, and pointing the telescope would be really difficult without a high powered finder lined up perfectly with the main scope. The small file size (1/4th the size of 320x240 mode files) would be a huge advantage. 

Clif 

ps: note the detail in the southern part of Hellas. I don't believe I have seen those dark markings before. Usually Hellas is uniformly dark. Wonder if the CO2 wind from the nearly evaporated polar cap has blown some light dust off a dark floor? Black ice frozen lake maybe? It would be neat to get a zoom view if the Mars orbiters have a look.

Email excerpt from Clif Ashcraft

Date: Tue, 27 Sep 2005 16:34:42 +0000

After I got home from Ray‘s last night the skies had cleared so Noah and I headed out for the observatory and set up for webcamming. I am now using a 6x, 0.17 NA microscope objective to give me f/36 with my 12.5" scope. I got 5 three minute videos and have just finished processing them in Registax. Lots of detail visible in all of them, however the last (taken at 2:59am) was the best here is an annotated version of this picture. Some subtleties were lost in converting from 16bit tiff file to 8bit jpeg, but most of the detail is there.

Clif

Email excerpt from Clif Ashcraft

Date: Mon, 19 Sep 2005 16:40:20 +0000

I did an experiment this morning to see if more magnification would help the visibility of faint features on Mars. The Nyquist-Shannon criterion specifies the minimum digital sampling rate to recover the highest spatial frequencies present in an analog image. This requires that we have a minimum of 2.8 pixels across the diameter of the Airy disk. It doesn‘t say anything about how much higher than that the sampling rate should actually be. I have been assuming that 2.8-3 pixels per Airy disk was enough, however, it is possible that the contrast of faint details can be improved by oversampling. To check this out, this morning I stacked my 2x Orion three element Barlow on top of the 5x Powermate I have been using on my 12.5" f/6 reflector giving f/60 and an effective focal length over 60 feet. The immediate effect as seen on the computer monitor was amazing. Much higher contrast. I had no trouble seeing the bright gulf between Sinus Sabaeus and Mare Meridinale. Mars looked like a big fat orange with a dark equatorial stripe. It almost filled the ToUcam field. I took several videos. It required a bit more effort to keep Mars centered in the frame (necessary so that Registax doesn‘t get lost during processing) but was a real trip, seeing details I had never been able to see before. See attached jpeg for two of my images.

Clif

Email excerpt from Clif Ashcraft

Date: Sun, 18 Sep 2005 17:08:08 +0000

Here‘s a set of images I got in the wee hours this morning. Similar aspect of Mars visible as the last set of images. Seeing was a bit better and I was able to include more frames in the sum to reduce s/n a bit.

Clif

Email excerpt from Clif Ashcraft

Date: Thu, 15 Sep 2005 19:20:12 +0000

Last night I didn‘t set the alarm, figuring that the remnants of Ophelia would preclude observations. However, my loyal observatory guard dog Noah decided that what we had done 10 nights in a row had become SOP and it was time for the lazy astronomer to get up (around 1:30 am). So, not wanting to argue with him, I got up and looked outside. Sure enough there was Mars, sitting in the middle of a big sucker hole in the clouds. I hurredly dressed and Noah and I went out to the observatory and got set up. By the time the sucker hole closed up, I was able to get 7 videos. The seeing was fair to middling, but I could actually see some details, including Sinus Sabaeus and the bright region between it and Mare Meridianal. Went back to bed and woke up around 11 am to torrential rainfall and a puppy dog with his hind legs crossed wanting to go for a walk. Here‘s one of the pictures I got.

Clif

Email excerpt from Clif Ashcraft

Date: Mon, 12 Sep 2005 00:45:26 +0000

Mars Webcamming with my 12.5" at f/30

This is probably my best set of images so far. Seeing was fair to good, and I could even see some of the detail on the computer screen as I was taking the videos. I was working at f/30 using the 5x Powermate to amplify my f/6 prime focus to properly match the sampling capability of the ToUcam which was working in the 320x240 pixel mode at 15 frames per second. Exposure time was 1/50th sec and I took 3 minute long videos of 2700 frames each. Processed in Registax. Images are stacks of the best 500 frames.

Clif