CCD Images - Taken with SBIG ST-7E CameraThese images represent early work where I am still coming up the learning curve. Been at it now since Feb 2002 and its now almost August 2002 as I post these. All these shots except M16 and M20 were taken from my light-polluted back yard probably Magnitude 4 conditions with sky glow from the city.
I have been amazed at what is possible under light polluted conditions! For example, the shot of M51 is far superior to my film shot that appears on my Astrophotography page. I am inclined to abandon film at this point... Down below there are some more notes that some might find interesting.
(Click on the thumbnail images below to view a larger image)
From the back yard:
From a Dark Site (Newman Park near Flagstaff - 9 and 11 Aug 2002)
From a Dark Site (Newman Park near Flagstaff - 13, 14, 15 Sep 2002)
The Ring Nebula
The Dumbell Nebula
The Eagle Nebula
(Click on the thumbnail images below to view a larger image or to view the video)
I have eliminated the flip-mirror from the system when doing deep-sky imaging. There is not enough mirror travel in the 10" LX-200 to allow use of the flip-mirror AND the f/3.3 focal reducer. I have attached the CFW-8 filter wheel directly to the ST-7E. I am now able to use the Meade f/6.3 and the Meade f/ 3.3 focal reducers. Mirror travel is OK to accomodate them. Centering objects is not a problem if your finder scope cross-hair is adjusted properly. I do a very careful polar alignment then locate a star such as Arcturus in the finder scope, center it carefully then take a .11 second exposure (minimum exposure time possible for ST-7E) and see if its in the frame. I usually do that with 3x3 binning to reduce the image upload time If the star cannot be seen, and you can't find it, then you have to remove the camera, put an eyepiece in and get the finder scope cross-hairs aligned properly. Then replace the camera and try again. I have had very little difficulty getting a bright star centered. One then "syncs" the LX-200 scope. If you have well-aligned telescope axes so that pointing accuracy is very good, the rest of the night is pretty easy. My LX-200 telescope control software lets me do everything remotely that needs to be done. (Except for setting the backlash value of the DEC axis. Don't think Meade published that command? Or I missed it somehow?)
I still use a flip mirror for planetary and lunar imaging. Actually increases the f-ratio a little which is not all bad for lunar and planetary imaging. Since the objects are bright, the flip-mirror can be of assistance in centering the object initially.
Collimation of the scope matters more than for film photography. The chip is small but it is very high resolution. Things that don't show up on film do show up on the CCD frame. Look, for example, at the resolution of the Eagle Nebula and compare it with my best film shot of the Eagle Nebula. The resolution with the CCD is amazing.
The ST7-E has a built-in guide chip. Using it as an auto-guider is necessary for deep-sky work to keep the telescope pointed properly. Has its own set of puzzles though. The filter wheel will change from clear to red to green to blue if you are taking a color shot. If the guide star does not show up brightly enough in one of the filters, you will lose it and ruin the shot. One of my early mistakes was to lose the guide star in this manner.
Finding a guide star is a problem. Problem has just been solved for me by Megastar 5. It now allows you to put an "overlay" on the star map that shows the fields for the imaging chip and for the guide chip. It also allows rotation about the center of the imaging chip so that you can see where good guide stars are and rotate the camera accordingly. I can hardly wait for the clouds to go away to begin using it. I was able to use it one night to calibrate the frame sizes against the star charts so I'm ready to go.
The other part of the learning curve involves image processing. "The Handbook of Astronomical Image Processing" is essential. Helps if you are a mathematician like me but even if you are not, I believe anyone intelligent enough to understand RA and DEC enough to find objects at night probably has the brain-power to make very good use of this excellent book. I spent about 4 days of a recent vacation in intense study of the principles involved in image processing. The ST-7E produces black and white 16-bit images. Your computer only displays 8-bit images. That means there is a lot more "information" in your image than you can display on the screen. Those 16 bit pixels have to be "mapped" to 8-bit pixels. You have a lot of control over that but you have to understand histograms to see how to find the optimum 8-bits worth of image data within your 16-bit image. All covered excellently in the Handbook.
Initially when I first started taking frames, I did not know exactly what I was trying to achieve. Now I know that I need to get as excellent a black and white shot of an object as I can get. That image is called the "Luminance" image. Then get reasonably good Red, Green, and Blue filtered images of the object. You essentially use the RGB images to "colorize" the luminance image. This is the LRGB system.
Sub-note. I am not happy with the "colorizing" or "color-image combine" process in the commercial packages I have. They tend to wash out the image, i.e., saturate the brighter areas. My opinion is that the Luminance image should define maximum brightness of each pixel. I have written software to do it properly. Here is an example of what I mean where the same shot was processed two ways:
Note that "theirs" washes out in the white areas and obscures the detail. The luminance frame that both were derived from looks like the image on the right rather than the image on the left, i.e., it has more gradations of brightness... The image on the left is washed out.
Making the excellent Luminance image look REALLY excellent involves a lot of work and judgement. Experience counts. The more you do it, the better you will become presumably. You need to know why you are doing things though. You are trying to bring out contrast and definition and you are trying to increase sharpness of the image. Sharpness involves using Lucy-Richardson deconvolution. This is an art to some extent but can be learned through experience presumably. (I still have a ways to go at this point but I believe I now have a handle on it.)
When applying the color images, if they are sharper than the luminance image, i.e., if their star images are smaller than the star images of the luminance frame, your stars will contain funny colored rings. This happened to me initially and I was greatly puzzled. And somewhat disgusted... What you do is fuzz out the color images using a Gaussian distribution. Places where the luminance frame is black will continue to be black even if that area of the red frame contains red from the fuzzed out star. That is, it will be if the colorization algorithm is "correct". Again, I am a bit skeptical about the color combine operations I see in the software packages I have that were not written by me...
Here is how significant this effect is for the two filters I was (inadvertently) experimenting with:
The image on the left was taken through the clear filter that came with the CFW-8 and is in focus. The image on the right resulted from merely switching to the Lumicon filter without making any focus adjustments. Since focusing is usually a major effort, refocussing simply to compensate for filters of different thickness is a major inconvenience. I do not have a micrometer (and it might damage the filters to use one) so my measurements so far are "eyeball" measurements. I removed all of my filters from their holders and discovered that the Lumicon H-beta filter that I have appears to be 1.5 times thicker than the Lumicon Deep Sky filter which in turn appears to be 1.5 times thicker than the Meade 80A filter, which in turn appears to be1.5 times thicker than the SBIG filters that came with the CFW8. So the Lumicon Deep Sky filter appears to be 1.5*1.5 or 2.25 times thicker than the SBIG provided filters and results in the defocussing effect shown in the images above when the filters are used with a 100" focal length, f/10 scope and an f/3.3 focal reducer. Note that it WAS possible to focus while using the Deep Sky Filter but then the filters provided by SBIG were then out of focus by the same amount shown above.
The upshot of this is that to minimize focussing effort, you need to use filters that are the same thickness and the same refractive index if possible. There does not appear to be any standard for filter thickness. SBIG appears to be aware of this and their filters appear to be matched. Note that this is another reason for them to provide a clear filter along with the red, green and blue filters. If you were to use red, green, blue, and "empty", the filters would extend the focus but the "empty" slot would not so it would have a different focal plane and would require extra focussing effort.
So enough for now... More later perhaps...
I used RedShift to locate the events and its video generator to capture them.
The first video shows all the Saturn/Titan transits for 2009 visible from Phoenix I THINK...
The transit events are shown by frames 20 minutes apart. The dates and approximate times for the first frame of each event (not the start of transit) are:
02/24/2009 0311 Hrs Local Phoenix time
03/12/2009 0251 Hrs Local Phoenix time
03/28/2009 0051 Hrs Local Phoenix time
04/12/2009 2331 Hrs Local Phoenix time
04/28/2009 2231 Hrs Local Phoenix time
05/14/2009 2111 Hrs Local Phoenix time
05/30/2009 2051 Hrs Local Phoenix time
06/15/2009 2031 Hrs Local Phoenix time
07/01/2009 2011 Hrs Local Phoenix time
07/17/2009 2011 Hrs Local Phoenix time
08/02/2009 1951 Hrs Local Phoenix time
NOTE that RedShift can see through the earth! Each frame contains Date/Time, Azimuth and Altitude in the upper left-hand corner in orange. NOTE that negative Altitude means Saturn is below the horizon! So look at the Altitude readings! The sky color is "true sky color" so when it turns blue, it means the sun is coming up...
The second video shows Saturn's close approach to Galaxy UGC6185 which is a mag 14.1 galaxy. Capturing this event would be a SUPER challenge due to the differences in the brightness of the galaxy and Saturn.
This galaxy event occurs on 05/03/2009 through 05/04/2009 with closest approach perhaps at 0031 Local Phoenix time on 05/04/2009.