Posts Tagged ‘Astrophotography Tutorials’

DSLR Astrophotography Tutorial

Monday, 16 February, 2009 20:06 Written by Ray Shore 6 Comments

Introduction

This DSLR astrophotography tutorial provides my method for obtaining the deep space images found in my deep space image gallery. I hope it will be useful for beginners in astrophotography with a digital camera; specifically a digital SLR (DSLR). Below are a few of my favorite astrophotos that I have taken using my telescope and Canon Digital Rebel. Click on thumbnails to view full size photo.

Beautiful images can be produced with today’s digital SLR cameras and software. I hope to demonstrate how this is done on a basic level in my DSLR astrophotography instructions below. First though, I will start with the setup I use for astrophotography of deep space objects.

One note before I get started, most of my imaging time is spent in the comfort of my control room inside the house. Thus, my tutorial provides a lot of insight to imaging remotely! :-)

Special Recognition- I would like to thank my good friend, mentor, and exceptional astro-imager Ed Henry of Hay Creek Observatory for all the guidance and inspiration he has provided to make this a most interesting and exciting pastime!

Note added 12/19/2010: I posted another DSLR astrophotography tutorial yesterday which covers my newer equipment and different software for processing. Check it out here!

My Astrophotography Equipment

Telescope

The telescope I use is an 80mm Orion ED80 APO refractor piggybacked to a 12″ Meade LX200. Here’s the details:

  • Orion ED80 Aperture: 80mm
  • Orion ED80 Focal Ratio: f/7.5
  • Orion ED80 Focal Length: 600mm
  • LX200 Mount: Heavy Fork
  • Accessories include a Telrad viewfinder

Telescope Used For DSLR Astrophotography

Camera

The digital SLR I use for deep space astrophotography is a Canon Digital Rebel.

Digital SLR Used for Astrophotography- Canon 300D

Canon Digital Rebel Details

  • Digital SLR (DSLR)
  • Sensor: CMOS
  • 6.5 megapixels
  • JPEG and RAW file format
  • ISO range: 100, 200, 400, 800, and 1,600
  • Shutter speeds: 30 to 1/4,000 seconds, plus Bulb
  • 3072 x 2048 pixel 24-bit JPEG and 36-bit RAW file formats.
  • Exposure modes: Shutter Priority, Aperture Priority, Depth-of-Field AE, Programmed AE with modes for Landscape, Macro, Night Scene, Portrait, and Sports, and full Manual

ImagesPlus Software

I control the Canon Digital Rebel with ImagesPlus software. This software provides a number of essential tools such as focusing, custom shutter control, image calibration, alignment & stacking, digital processing etc. ImagesPlus software is available here. Much more detail will be provided later in my DSLR astrophotography tutorial.

First Things First- Drift Align

A good Polar alignment is very critical for taking long exposures. My simple drift align method can be found here. Note that this is based on my Meade LX200, but the concept is the same for any equatorial mounted telescope.

Drift Align for Astrophotgraphy

Click for Simple Drift Align Method

Custom Shutter Cable and USB Cable

I operate my Canon Digital Rebel remotely through the ImagesPlus software using a custom shutter cable and USB cable. Although I built my own custom shutter cable, pre-made cables can be purchased from Hap Griffin Astro Cables. Basically, the custom shutter cable combined with ImagesPlus software allows me to override the Canon’s 30 second exposure limitation. Here is a brief description of both types of cables. Note that they are specific to my setup with the Canon Digital Rebel (300D).Custom Shutter Cable2.5 mm, 3-Conductor Connector.

Custom Shutter Cable

The camera end of the cable has a 2.5 mm, 3-conductor connector. It plugs into the remote control terminal on the side of the Canon Digital Rebel. This is normally where the Remote Switch RS-60E3 plugs in (not used in this application though). ImagesPlus software operates the custom shutter control through this cable.

2.5 mm, 3-Conductor Connector

2.5 mm, 3-Conductor Connector

The other end of the custom shutter cable is a parallel port connector with a special pinout for operating the shutter control. Hap Griffin can provide custom shutter cables with parallel port connectors, serial port connectors, USB, etc. for various computer ports and DSLR’s.

USB Cable

This is the standard USB cable that comes with the DSLR camera for uploading photos. However, since I’m imaging remotely (i.e., from my garage), I have extended it with Cat. 5 UTP and a USB Extender. Before this, I just hooked together a couple of 16 foot USB booster cables (like this one: Iogear GUE216 USB 2.0 Booster Extension Cable) and strung them across the yard from my garage. One end plugged into the computer USB port and the other end attached to the standard camera USB cable. Then the standard cable plugged into the USB port on the DSLR camera. Everything runs underground now though.

Connection of the two types of cables to the digital SLR shown below. These connections are necessary to operate the ImagesPlus software as explained later in my tutorial.

Connections to the Canon DSLR

Connection to Telescope

Attaching the DSLR to the telescope requires a t-ring and t-adapter as shown below.

Step 1

T-adapter and T-ring are separate components. Note that the t-ring must be specific to the type of digital SLR used.

Step 1- T-adapter and T-ring are separate components. Note that the t-ring must be specific to the type of digital SLR used.

Step 2

The t-adapter and t-ring are threaded. The two components are combined.

T-Adapter and T-Ring Combined for DSLR Attachement

Step 3

Attach to digital SLR.

Attach to Digital SLR

Step 4

Attach digital SLR to telescope. The DSLR with t-adapter/t-ring assembly is inserted into the telescope eyepiece holder directly (i.e., no eyepieces, Barlows, etc are utilized). Important tips: tighten the telescope thumbscrew to the t-adapter securely. Also, be sure to attach the DSLR strap to the telescope in case the camera falls. I have actually had this happen a few times in the past, but my camera was spared since I strapped it to the telescope! See DSLR strapped here.

DSLR Mounted to Telescope

Telescopes.com T-Rings and T-Adapters

T-Ring – Canon EOS

T-Ring for Canon EOS

T-Adapter Universal 1 1/4 Inch

T-Adapter for Canon DSLR

More T-Rings and T-Adapters

Digital SLR Settings

Here are the DSLR settings:

1. The mode dial is set to manual as shown below:

Digital SLR Setting
2. The shutter speed is set to bulb as shown below:

DSLR Bulb Setting

3. Camera menu settings:

Image recording quality is set to “RAW”.
Review is turned off (the display won’t be necessary).
Auto Power Off is set to “off” so the camera stays on while imaging. I use an AC adapter instead of the battery so I can image continuously without losing power.
All other settings are made through the ImagesPlus software as described later in my tutorial.

Digital SLR Focus Through Telescope

Center a bright star in the DSLR field of view. Manually adjust the telescope focus as close as possible through the camera viewfinder. Then use the ImagesPlus focusing routine. Reference screenshot below. Here is the procedure:

1. Click on the Focus tab in ImagesPlus.
2. Click the Release button. A short exposure will be taken by the digital SLR camera. Note that a prompt may appear indicating that the camera needs to be changed from bulb and RAW format for the focus routine. If so, click ok. Another prompt will appear later to change back to bulb and RAW format.
3. Draw a small frame around the bright star.
4. Select the star by clicking on the center of it when prompted.
5. Click the Release button to obtain the initial focus reading.
6. Make a small adjustment to the focus. Be sure to note the direction that the focus knob is turned.
7. Click the Release button again. If the focus was improved, then the “Current Frame” will have a lower pixel value than the “Current Best”. But if the focus did not improve, then the “Current Frame” will have a higher pixel value than the “Current Best”.
8. This procedure is continued until the “Current Best” pixel value cannot be improved upon. It is helpful to check the graph after every adjustment to see which way the green line (which represents the Current Frame) slopes. If it slopes upward after the last adjustment, then the focus got worse. And of course, if the line slopes downward, the focus improved. Tip: an electric micro-focuser would be very nice to have here! It would save time going back and forth to the telescope and it would provide very fine adjustments to the focus.

Focus Digital SLR

Finding Object & Centering in Field of View

Manual Method

Before obtaining goto capability, this is how I located and centered an object in the camera field of view. It’s very similar to finding an object through the telescope viewfinder, except the DSLR viewfinder is used.

1. Target the astrophotography subject using the telescope viewfinder first. I highly recommend a Telrad viewfinder since it provides a large, unmagnified view of the sky.
2. If the object is bright (e.g., The Orion Nebula), it may be possible to see it through the DSLR viewfinder. If so, center the object within the field of view through the camera’s viewfinder.
3. If the object is not bright enough to detect in the DSLR viewfinder, then position the object in the FOV by identifying a nearby star. A good star chart will be helpful here.
4. Some tweaking to the telescope’s aim may be necessary. This will be determined when trial exposures are taken later.

Goto Method

This method utilizes TheSky software program (version 5) with the telescope’s goto. It has made my job a LOT easier!

thesky6

TheSky6 Serious Astronomer Edition

1. Center a familiar bright star (like the one used in the focus stage above) in the DSLR camera viewfinder field of view.
2. Establish a telescope link in TheSky program (this step assumes that the telescope has been set up in the software program).
3. Now find the star in TheSky map and click on it.
4. Click the Synchronize button.
5. Now find the astrophotography target in TheSky’s map and click on it.
6. Click the telescope slew button.
7. If everything has been set up correctly, then the object should be fairly well centered. This will be determined when trial exposures are taken later.

Setting up Custom Shutter Control in ImagesPlus

1. With the DSLR off, open “ImagesPlus Camera Control” program.
2. Go to camera menu and select Canon DSLR then select camera control for 300D/Rebel.
3. Select the Bulb Capture tab in the Canon DSLR Control window.

DSLR Bulb Capture

4. Control Type is 0×378 x Parallel Port, Shutter=DO=P2AF=D1=P3.
5. Click the Reset button. The default Shutter Sequence Parameters should appear as depicted in the screenshot below:

DSLR Shutter Sequence Parameters

6. With cables attached, turn on the camera. Be sure that the DSLR is set according to Section 7 above (Digital SLR Settings)
7. A Windows pop-up will appear because the camera is connected (prompting you to choose a photo upload program). Cancel this feature. The photos will be uploaded through ImagesPlus.

Connect DSLR

8. Select the Connect tab in the Canon DSLR Control window.
9. Click the Connect button. The EOS Kiss REBEL 300D will show up as the available camera.

Canon Digital SLR Available

10. Click on the Transfer tab in the Canon DSLR Control window. Click the Select button at the bottom of the Canon DSLR Control window. Select a directory on computer hard drive to store the images.

Transfer Tab- DSLR Astrophotography Tutorial

11. Click the Bulb Capture tab in the Canon DSLR Control window.
12. Click the Edit button to change the default Shutter Sequence Parameters
13. In this example, I set the Interval to 10, Exposure time (seconds) to 300, Total Exposures to 5, ISO to 100, and added the prefix “M42″ which will show up in the file name.

Edit Shutter Values- DSLR

14. Click the Save button.
15. At this point, another shutter sequence could be added if other settings (e.g., ISO, exposure time, more frames, etc.) are desired. For this tutorial, I’m keeping it simple with just one set of frames.
16. Everything is set to start taking the light frames. With the digital SLR still connected, move on to the next section.

Taking the Light Frames

1. Click the Release button and the camera will follow through with the custom shutter settings. Note the exposure duration (i.e., time elapsed) and the number of released exposures.

Tip: Before taking a lot of exposures, experiment with trial settings first. I always take a single short exposure (e.g., 60 seconds) first to make sure my subject is centered in the field of view.

I also vary the ISO settings and exposure lengths on single exposures to see what works best. Once I’m satisfied, then I proceed to taking a large set of frames.

A note about the ISO setting- the higher the ISO setting, the brighter your image, but the more noise that is introduced. I rarely image at the maximum ISO setting of 1600. The images are just too grainy. I chose ISO 100 for my M42 example because I did not want to burn out the center of the nebula. Ideally I would probably take several frames at ISO 100 and several frames at a higher level like ISO 400 and combined them. But for my tutorial, I’m keeping it simple!

Shutter Routine- DSLR Astrophotography

2. Wait for the shutter routine to complete. The images will be uploaded automatically to the previously selected directory on the computer (“Image Transfer Progress” pop-up will appear when the images are being uploaded to computer).
3. Leave DSLR connected and move to the next section to take the dark frames.

Taking the Dark Frames

At this point, it’s time to take some dark frames. These frames will be used later during the calibration stage in ImagesPlus. Basically, the dark frames will be subtracted from the light frames to remove much of the hot pixels and other artifacts. It helps to polish up the final photo a bit!

The procedure is simple, just put the lens cap on the telescope and take at least 3 frames with the same settings as the light frames. I like to create a directory for the dark frames to keep them separate from the others. More on dark frames and calibration coming up in my tutorial.

Converting RAW Images to TIFF

Now that the subframes have been captured, it’s time to convert them from a RAW image format to a 16-bit TIFF file. This task is easily performed in ImagesPlus. Here are the steps:

1. On the file menu, select Canon Raw File Development and Conversion.
2. Find the folder with the light frames. Note that all of the light frame files should have the extension “.CRW”. This extension indicates that the file is in a RAW format. Example file: m42300SecISO100_000012.CRW. A nice feature of ImagesPlus is that the seconds and ISO setting is automatically built into the file name!
3. Select the light frame files to be converted. To select several at once, just click on the first file in the series, hold down the shift key, then select the last file in the series. The entire series should be highlighted.
4. Click Open.
5. Now the Canon Raw File Conversion box should be open. Leave the Conversion Parameters set to Canon White Balance Color.
6. Select “16-Bit TIFF” for the Output File Type. Note that the prefix defaults to “CVT_”. This means that the output file (i.e., converted file) will have the extension”.cvt”.

Canon RAW File Conversion-DSLR

7. Select an output directory for the converted image. I usually leave it at the default which is where the RAW files reside.
8. Click the Convert button. The conversion process may take awhile depending on the number of light frames, speed of computer, file size, etc. 9. This is a good time to get a cup of coffee!
9. Click the Done button when the conversion is complete.
10. Repeat the conversion process above for the dark frames as well.

Calibrating Frames

Automatic processing is utilized to calibrate the light frames. Click File then Automatic Image Set Processing.

1. Under the Process tab, select Color (probably the default selection).
2. Under the Light Frames tab, click the “Select Light Frames” button. Now select all of the converted Tiff files. Example file name: CVT_m42300SecISO100_000012.tif.
3. Under the Dark Frames tab, click the “Select Dark Frames” button. Now select all of the converted dark frames. Example file name: CVT_m42dards300SecISO100_000017.tif
4. This tutorial does not cover Flat Frames or Bias Frames so these tabs are skipped. If these frames were obtained however, this is where they would be loaded for calibration.
5. Go back to the Process tab and click the “Process” button.
6. Do not click Done yet. Move on to the next section for a Translate, Scale, and Rotate of the calibrated frames.

Aligning Frames

1. The Automatic Image Set Processing box should still be open. Click on the Align TSR button.
2. The following box should open:

Align Frames in Registax

3. Select Centroid as the Alignment Method.
4. Under Alignment Type, select Translate + Rotate.
5. Under Alignment Selection, select Common COR Point, Reference Image, and Auto Advance After Select.
6. Now minimize the Align TSR box and the Automatic Image Set Processing box.
7. The first frame of the calibrated Tiff’s should be displayed. Holding the shift key, click on a reference star in the image. The frame will automatically advance to the next frame. Click on the same star in the second frame. This process is continued until a reference star has been selected for each frame. Eventually the starting frame will be reached. This is indicated by the red box around the reference point as shown below:

Select a Common Point

8. Now maximize the Align TSR box again. In the Alignment Selection area, select Common Angle Defining Point or Star.
9. Repeat step 7 above on a different star. When all of the frames have been marked and the starting frame appears, a blue box will surround the second reference point (Common Angle Defining Point or Star) as shown below:

DSLR Astrophotography Tutorial- Common Angle

10. Now maximize the Align TSR box again and click the File Set Control tab. Select a folder where the calibrated & aligned image will be saved.
11. Click the Align Methods tab again and click Align. This process may take awhile depending on the number of frames, speed of computer, file size, etc.
12. After the alignment is complete, click on the File Set Control tab in the Align TSR box. Now click the Aligned button under Combine. Choose Average under Combination Methods.
13. Now click the File Set Control tab. Select an output directory and check Auto Display.
14. Click the Standard Methods tab again and click the Combine button. Again, this process may take awhile to complete.
15. When the files have been combined, click the Done button. The calibrated, aligned, and combined file will be displayed. The file name should be CombinedFilesAvg.

Digital Development

1. With the CombinedFilesAvg file still open, go to the Color menu, Brightness Levels and Curves, and select Digital Development. Reference screenshot below.
2. Enable Sliders.
3. Pull the Break-Point slider to the left until the desired amount of detail obtained.
4. Bump the Backgd Wt. slider slightly to the right to darken the background a bit.
5. Click the Done button when finished.
6. Save the file as either an 8-bit or 16-bit Uncompressed TIFF depending on the program to be used for further processing (next section). Alternatively, I could finish processing through ImagesPlus which has a number of tools for the job.

DSLR Astrophotography Tutorial- Digital Development

Further Processing- Adobe Photoshop

I won’t spend too much time on this part. Basically, the following tools in Adobe Photoshop are used to clean up the photo for the final version:

  • Crop (to center image)
  • Rotate canvas (for proper orientation)
  • Levels (tonal range and color balance)
  • Contrast
  • Brightness
  • Despeckle (cleans up some of the noise)
  • Unsharp Mask (sharpens image but introduces noise!)
  • Color Balance
  • Hue & Saturation

Final Image!

Digital SLR Astrophotography Tutorial- Final Image!

Final note: the image above could have been improved by taking more light frames and combining them. I only captured 5 exposures for this example, but 10 or 20 would be better. Also, exposure length is important for gathering as much light as possible from those faint deep space objects. The longer the exposure, the more light gathered. Just keep in mind that longer exposures can introduce noise, star drift, etc. With experience, you will figure out the optimal exposure time for your setup.

Closing Notes

I hope you enjoyed my Digital SLR Astrophotography Tutorial and find it useful. If you have any suggestions, questions, or comments, please feel free to contact me at ray@shoregalaxy.com. I look forward to your feedback! Thanks, Ray Shore

This DSLR astrophotography tutorial was:

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Further Reading

Enhance your understanding of DSLR astrophotography with related books by the experts.

Digital AstrophotographyA Guide to Astrophotography with Digital SLR CamerasDigital SLR Astrophotography

Photoshop Astrophotography Tutorial

Saturday, 07 February, 2009 18:08 Written by AstroPhotography Tonight 0 Comments

Here is a good quick start guide to using Adobe Photoshop 7.0 for enhancing a planetary image. For this example, a recently processed image from Registax 4 was used. See Registax 4 tutorial here.

In this photoshop tutorial, we will introduce some basic tools for cleaning up and enhancing an astro-photo including:

Read more ...

Registax 4 Tutorial

Sunday, 01 February, 2009 18:31 Written by AstroPhotography Tonight 2 Comments
 
This tutorial covers the basic steps of processing planetary videos using Registax 4. The Registax program is a free download compliments of Cor Berrevoets! To get started, you will need to download the program to your computer and run the setup program. Registax 4 download here.

Be sure to watch the Registax 4 video tutorial below. It is part of the Astroadventure Weekly series provided by Rod Miller of MDM Productions who developed the instructional DVD Webcam Astrophotography to aid the beginner in getting started in webcam imaging.

Registax 4 Tutorial

Click the “play” button to start the video.  

Basic Tutorial

Below is a quick start guide to using Registax 4. Refer to the video above for more detail.

1. Click the select button at the top left. 2. Find your video file on your computer and open it. 3. You may see a box prompting you to select whether to process in color. Click yes.

Registax Color Option

4. Use the slider at the bottom of the Registax 4 window to move through each frame in the series until you find the best one in terms of sharpness, clarity, focus, etc. You want to find the best looking frame to use as a reference for further processing.

Registax Slider

5. Next, it is time to choose an alignment box. You have a choice of 32, 64, 128, 256, and 512. Some astro-imagers will use a small box to frame a particular detail on the planet while others will use a larger size frame the entire planet. It is entirely up to the user. You will likely develop a preference through trial and error. With the reference frame visible in the window, click on the box you want to use and frame the planet (or and area of detail on the planet if you are using a small box).

Registax Alignment

6. Click on the automatic processing button then click the align button. 7. Registax 4 will automatically work through alignment, optimize, and stacking. It will stop on the wavelet processing area. This part is done manually. 8. Adjust each slider until the desired amount of detail is brought out of the stacked image. This is another matter of trial and error to see what works best. Be sure not to over-sharpen the image by pushing the sliders too far though. Your final result will be an image that looks “over-processed”.

Registax Wavelets

9. Click the Contrast/Brightness button to tweak the image if it is too bright or dim. 10. When you are happy with the result, click the “Do All” button at the top left to complete the process. 11. Click the save image button to save the image to your computer. Note the various file types available such as BMP, JPEG, PNG, etc. Note that if you want to save the file for processing further in Registax, click the “Save As” button in the project section. 12. For more details on each stage, refer to the attached video above. You will find more discussion related to alignment adjustments, quality graphs, quality settings, alignment optimization, resampling, drizzle, percentage improvement, wavelet settings, and contrast.

Webcam Astrophography Instructional DVD

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Get a good start on imaging with Webcam Astrophotography by Rod Miller.  In this Video you will learn:

  • The best webcams to use.
  • How to attach a webcam to your telescope.
  • How to focus your webcam.
  • What software to use.
  • How to stack and process your images.
  • And more!
 

Webcam Astrophotography Tutorial for Planets

Thursday, 29 January, 2009 20:33 Written by Ray Shore 9 Comments

Introduction

This webcam astrophotography tutorial is intended to explain my method for obtaining the planetary images found in my solar system image gallery. I hope it will be useful to those who are just starting out in astrophotography with a webcam. Below are a few of my favorite astrophotos that I have taken using my telescope and webcam. Click on thumbnails to view full size photo.

Incredible detail can be obtained with today’s imaging techniques and software. I hope to demonstrate how this is done on a basic level in my webcam astrophotography instructions below. First though, I will start with the setup I use for astrophotography of planets.

My Astrophotography Equipment

a) Telescope

Astrophotography TelescopeThe telescope I use is an 8″ Celestron Schmidt Cassegrain Telescope (SCT). Here’s the details:

Mount: CG5 Aperture: 8″ (200 mm) Focal Ratio: f/10 Focal Length: 2000 mm Highest Useful Magnification: 450X Resolution: .57 arc/sec Home-built pier Accessories include a Telrad viewfinder, JMI zero image-shift microfocuser, Celestron 6X30 viewfinder, RA and DEC motor drives, and dew shield.

.

b) Camera

Philips ToUcam Pro 740K- Astrophotography CameraThe camera I use for planetary astrophotography is a Philips ToUcam Pro 740K. It’s basically an upper-end computer webcam. Here’s the details: Philips ToUcam Pro 740K Max resolution: 640 x 480 pixels (1280 x 960 for stills) Max frame rate: 60 fps Sensor: CCD This one is a very popular camera for astrophotography. However, Celestron and Meade have their own version as well. They are designed specifically for Astrophotography. See the “Further resources” section to the right.

.

Attaching the Webcam to the Telescope (Added June 2nd, 2008):

Due to a number of requests, I added instructions for attaching the ToUcam to the telescope. Click on each photo below to view instructions.

Registax Software

The method for obtaining high resolution images of the planets actually starts with a video taken with the webcam. The video is then processed in a freeware program called Registax (by Cor Berrevoets) and results in a “stacked” image of several hundred frames. This will all be explained in detail later in this article. Registax download here.

Finding the Planet Through the Webcam (webcam astrophotography method starts here)

The first step can be the most tricky part of it all! It is necessary to precisely center the planet in a relatively high power eyepiece. This must be done before switching to the webcam. Here are the steps involved:

  1. Insert 2X Barlow lens. Webcam is not inserted yet.
  2. Insert 32mm eyepiece for a low power, wide field of view. Adjust RA and DEC until the planet is as close to center as possible.
  3. Carefully switch to the higher power eyepiece. I use a 10mm Plossl for this. This gives me about 400X magnification which is close to my highest “useful” magnification.
  4. Center the planet and make sure it holds its position. A good polar alignment helps a lot here!
  5. Very carefully, switch to the webcam (i.e.., remove the eyepiece and insert webcam).
  6. Open the webcam software program. In my case, I use Spotlife which came with my Philips ToUcam Pro 740K. If the planet is not visible on the screen, it is usually due to 1 of 3 things: gain setting is too low, the planet is not centered (normally the case), or the telescope is WAY out of focus. Gain Setting

One time I got frustrated because I could not get Saturn to show up on the screen. I was certain that it was centered well enough in the eyepiece. After quite a few minutes I decided to turn up the gain. Saturn was right there the whole time! So the best thing to try first is to turn up the gain. This is done in the webcam settings. I usually turn the gain up to about 75% to make the image bright enough to detect.

Center in Eyepiece Again

This is normally the case. If the planet is still not visible, then follow the steps above again to center the planet. Normally it’s just a matter of getting the planet centered in the webcam field of view. This was difficult when I first started using a webcam for astrophotography, but became MUCH easier with practice!

Focus

When all else fails, check the focus. It’s possible (although unusual) for the image to be so far out of focus that it’s too dim to detect. When the planet is in focus through my 10mm eyepiece, then it is usually visible (although not focused) through the webcam. I can easily make the adjustments once the planet is centered on the screen. Here is a screenshot of what it looks like:

Astrophotography Tutorial- Center the Planet then Focus

Webcam Adjustments

Once the planet is centered on the screen, then it is time to make some adjustments to the webcam. First, I adjust the shutter speed and gain. To obtain the best quality, I normally select a shutter speed of 1/25 seconds or 1/33 seconds (or even 1/100 seconds in the case of Mars). I normally set the gain below 50%. It is important to keep the gain as low as possible but still see the detail. Otherwise, the finer details will be over-exposed. See screenshot below for typical settings:

Astrophotography Webcam Properties

Frame Rate

Another important setting is the frame rate. The frame rate is directly related to image quality. Normally, I use a frame rate of 5 fps (frames per second) or 10 fps. Basically, 5 fps yields a higher resolution frame than 10 fps. However, by using 10 fps, I can obtain more frames (to stack) in a given time period. 5 fps works well when the seeing is very steady. Otherwise, I use 10 fps (which is most of the time!) Here’s what the setting looks like:

Webcam Frame Rate Settings

Capturing the Video

I normally take a 3-4 minute video (AVI) of the planets. This will yield hundreds of frames from which to stack (stacking process will be discussed later in the article). For example, if I take a 3 minute video at 10 fps, I will end up with 1800 frames (3 minutes x 60 seconds x10 fps). To a certain extent, the more frames available for stacking, the better the detail possible. It is important to note that there is a point where the detail will become blurred due to planet rotation. This is especially the case with Jupiter and its 10 hour rotation period. Thus, I limit my videos to about a 4 minute maximum recording time. As explained later, not all of the 1800 frames can be used during the stacking process. Once I have started the video, I watch the planet to make sure that it does not drift off the screen. If it starts to get close to the edge, I make a fine adjustment to RA or DEC on the motor drive hand controller. The better I polar align my scope to start with though, the less I have to worry about drifting!

Registax Processing

Next comes the fun part of processing the video. The program of choice for stacking frames is Registax. Since Registax 3 is the latest version of software as of this writing, I’ll use it as an example. However, the basic principles are the same with any version of Registax. 2/3/09 Update: Registax 4 tutorial here. Registax download here. Thanks to Cor Berrevoets (creator of Registax), it is available as freeware. His program is WELL appreciated! Here is the basic procedure for converting an AVI video into a single stacked imaged.

1. Change screen area to 1024 by 768 pixels. In Registax 3, the entire screen is not visible with 800 by 600 resolution.

2. Open Registax and click on the select button at the top left of screen. Choose the video taken with webcam.

3. Scan the individual frames in the avi to find the best looking one. Frames will vary in quality from each other mostly due to the fluctuations in the atmosphere. It is important to select a frame that provides the sharpest detail in the group since all others will be sorted according to this frame. Frames can be previewed by using the slider bar or the framelist. See screenshot below. Click to open in separate window (for easy reference).

Find Reference Frame in Registax

4. Once the best frame is found, then an alignment box must be drawn around the image or particular feature within the image. I usually draw a box around the entire image though. There are several sizes of alignment boxes to choose from. These include 32, 64, 128, and 256. I select a size that is just large enough to completely surround the image of the planet.

5. Be sure to check the box “Use Colour”.

6. In the Quality Estimate section, I select the Classic method and a Lowest Quality setting of 90%. This means that only those frames that are at least 90% as good as the reference frame will processed.

7. Click the Align button and the alignment process will begin.

8. At the end of the alignment process, note (at the bottom of screen) the stack size vs. the original number of frames. The lower quality frames (as compared to the reference frame) were screened out. Clicking the Limit button will eliminate the lower quality frames. Note the fewer number of frames for processing.

9. Now click on the Stack tab. Further refinement will be performed here. If the Stackgraph is not already displayed, click on the tab. Note the 2 sliders. The vertical slider is for difference cutoff. This is adjusted downward to eliminate those frames that are significantly different from the others. Here I cut off any large spikes. The horizontal slider controls the quality of the frames. The graph slopes downward from left to right. The left side being the highest quality frames (again, as compared to the originally selected reference frame) and the right side being the least quality frames. Better frames are selected as the slider is moved to the left. As this adjustment is made, the number of frames shown at the bottom of the screen will change.

10. When the best frames are selected, it is time to stack them together. Registax combines all the selected frames (that were at least 90% as good as the reference frame plus the additional manual adjustments) into a final composite image. I like to have a stack of at least 300 frames. The more frames that are stacked, the better the signal to noise ratio (more signal, less noise). Since each frame varies a bit in the amount of detail that was captured, the final stack will be a nice composite with lots of detail!

11. Now click the Wavelet tab. This is where the magic begins! Click the contrast tab and move the slider slightly to the left for both contrast and brightness. Note the wavelet sliders in the screenshot below.

Registax Wavelett Processing

12. Now it is time to adjust the wavelet sliders to bring out the detail in the composite image. I normally only adjust the sliders for layers 2-5. A lot of trial and error takes place at this stage. As the sliders are moved to the right, detail is brought out of the image. A nice balance must be struck between under-processing and over-processing the photo. If the wavelets aren’t adjusted enough, then not all of the available detail will be brought out in the image. Over adjusting however will only make the photo grainy (noise). Here is a screenshot of the image above after some adjustment of the layers: As you can see, the detail really stands out! Now it is time to polish up the image for final version.

Webcam Astrophotography- Registax Processing

13. Click on the Final tab. Click on the Save Image button or copy it to the clipboard. Note that final processing can be performed here. However, I prefer to finish it up in a photo editing program (Adobe Photoshop normally).

Further Processing- Adobe Photoshop

I won’t spend too much time on this part. Please refer to the Photoshop Astrophotography Tutorial here for more information. Basically, the following tools in Photoshop are used to clean up the photo for the final version:

  • Crop (to center image)
  • Rotate canvas (for proper orientation)
  • Levels (tonal range and color balance)
  • Contrast Brightness Despeckle (cleans up some of the noise)
  • Unsharp Mask (sharpens image but introduces noise!)
  • Color Balance Hue & Saturation

Final Image!

Astrophotography Tutorial- Final Composite Image!

Tips for Enhanced Planetary Imaging! Added June 2nd, 2008

Be sure that you have precise collimation of your telescope. This is especially critical for high power planetary imaging. Image during very good seeing conditions. You’ll want to image when there is a stable air mass above you. Check the sky clock if there is one available for your area at: http://www.cleardarksky.com. Set your scope up outside at least 1 hour before imaging. If it hasn’t had time to reach thermal equilibrium with the outdoor temperature, then the image can become distorted due to tube currents. Tweak the focus until you get the sharpest image possible “overall”. The planet will appear to go in and out of focus constantly. This is due to an unstable atmosphere that you are imaging through. Spend a lot of time getting the best possible focus you can.

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Further Reading

Enhance your understanding of webcam astrophotography with related books by the experts.

 

Webcam AstrophotographyLunar and Planetary Webcam User's GuideIntroduction to Webcam Astrophotography

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