Canon Digital Rebel XSi (450D) Modification

by Gary Honis

(best viewed in 1280 by 800 pixel display resolution)

Page 12 - Astro Images with unmodified 450D

Removal of IR Cut Filter for Astrophotography

Unmodified Test Images:

The first night out with the unmodified camera was on a fairly clear night but when I would not normally image, with the Moon at 75% phase. Because of the Moonlight I kept exposures to a maximum of 60 seconds at both ISO 800 and ISO 1600 for these test images. All of the images below were unguided. using an Orion Atlas Mount with EQMOD. A photo of my deck observatory setup with remote control can be seen here. My purpose of testing the new camera was to learn its features and verify that it was operating correctly before taking the camera apart for the IR filter replacement.


Normally, I would use a barlow for imaging the Moon with my Orion ED80 refractor. I already had the Televue .80X focal reducer on the ED80 but imaged the Moon with it since it was already set up and I was anxious to try some deep sky imaging using the reducer. The resolution of the 12.2 Megapixel Canon 450D imaging chip is 4272 by 2848 pixels. ISO setting was 100 and a 1/250 second exposure was used to help freeze the poor seeing conditions. Here is the Full Frame image taken:

One advantage of the 450D over the 300D is its higher resolution, so crops of the original hold up very well. Here is a CROP the above image around the Moon which has been reduced to 1200X1200 pixel size:

Galaxies M81 and M82 - Full Frame:

I would not normally image deep sky objects with the Moon at 75% phase, so keep that in mind for the following imaging results. ISO 1600 was used and 57 one-minute exposures were median stacked. The dark band at the top is due to reframing of the object during the exposures.

Here is a CROP the above image that has also been reduced to 1200X1200 pixel size:

M13 Hurcules Globular Cluster - Full Frame:

ISO 800 was used and 7 one-minute exposures were median stacked:

Here is a CROP the above image that has also been reduced to 1200X1200 pixel size:

M44 Beehive Cluster - Full Frame:

This open star cluster was near the Moon so I kept the exposures short at 35 seconds. ISO 1600 was used and 12 frames were median stacked:

Initial Test Comments:

Having imaged in the past with the Canon 10D and modified Canon 300D, I was pleased with the operation and first-light images of the 450D under a Moon-lit sky. The camera tested well and I was later successful in taking it apart to remove the IR cut filter; see modification procedure here beginning on PAGE 1.

Some notes on my initial thoughts after the first night of imaging with the new camera:

Auto Clean: Using the 450D's menu system, I disabled the "Auto Clean" feature so that it does not do a cleaning every time the camera is turned off. This was done to avoid any problems taking flats.

USB Connection: What a welcome feature to have all camera functions available via the USB 2.0 connection! Only one wired connection is now needed between the 450D and the computer and it is the USB cable supplied with the camera. No longer are special cables needed such as the one I built HERE for triggering the 10D bulb exposures that also required a USB to RS232 adapter for my notebook computer without a serial port.

Battery: The 450D has a different battery than the 300D and on the first night it lasted about 5 hours, even when using the camera's live view feature. With all-night imaging, especially if by remote control, an AC power adapter is preferred. The part number for the AC adapter is ACKE5 and can be ordered online from many sources.

Control Software: I no longer need to use DSLR focus or Images Plus to change the camera's settings, for focusing and taking bulb exposures, including interval exposures, since these basic functions are now available in the software that comes with the camera, "Canon EOS Utility". See next page for details.

Viewfinder: After my first all-night imaging session with the 450D, I was amazed at dawn when I realized that I had not once looked through the camera's viewfinder. I will most likely block it off with a cover for astro imaging to avoid stray light entry. I never used the viewfinder because of the camera's "live view" feature.

Live View: I used the 450D's "live view" feature to center stars for the alignment procedure for my Atlas Mount using EQMOD and also to help center objects to be imaged in the imaging frame. On brighter objects this involves seeing the object on the live view display and moving the mount to center it. For dimmer deep sky objects this involves taking an exposure, noticing its position relative to the center of the imaging frame and then using "live view" in zoom mode to move the star field appropriately.

Weight: I own the Canon 10D, 300D and 450D. The weight of these bodies alone are 2.5, 1.5 and 1.25 pounds respectively. The 450D body is the lightest of the three and is just slightly smaller in size than the 300D. The lesser weight of the 450D is an advantage for keeping the weight loading down on telescope focusers.

14-bit A/D processor: The 450D analog to digital (A/D) conversion process is now increased to 14-Bit from 12-Bit allowing the camera to record up to 16K colors per channel for smoother tonal transitions and more accurate color gradations.

Image Transfer Speed: The 450D has a USB 2.0 connection, as opposed to USB 1.1 on the 300D. The download of images from the camera to notebook after capture was nearly a minute for the 300D but only about three seconds for the 450D, and that is for a much larger (15.32 MB) file.

Image Processing: The RAW (CR2) file size of the 450D (15.32 MB) presents an increased burden on image processing. I use both a 2.8 GHz Pentium 4 notebook and a Core Duo T2400 processor notebook and image processing was noticeably slower. The TIF files converted from the Canon CR2 Raw files are each 72.3 MB in size! My older version of Images Plus is not able to convert the RAW files. The freeware Deep Sky Stacker does work with the 450D Raw files. Also, the software provided by Canon with the camera, Digital Photo Professional can be used to open and convert the Raw files.

Looks like I will be shopping for another hard drive and maybe a faster computer:)

CONTINUED NEXT PAGE - Page 13 : Canon EOS Utility & Live View for Camera Control for Astro-Imaging


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