I am very interested to shoot a star trail photo. Can I shoot a star trail using Canon t2i? Do do I need to use MagicLantern framework to get bulb mode support?
Thanks in advance.
You don't need Magic Lantern at all. All you need to do is shoot in Manual Mode and have some way to trigger the shutter continually.
When I shot this photo, I simply set my camera on a tripod and locked it off, set my camera to M mode, set my camera to ISO 100 (I think), f/4, and 30 seconds. Set the shutter mode to continuous, and plugged in my cable release which I then clicked on and locked off (so it stays pressed). The result is that the camera takes the photo (30 seconds) and as soon as it finishes, it starts the next one.
I left it like this for approximately one hour. Then took the first resulting image in Lightroom, applied NR and a few other settings (I think maybe clarity or sharpness, lens correction, etc...I can't quite remember), copy & pasted the settings to all the other photos, then exported them to JPG.
Finally, I used the free software Starstax to combine all the individual images into one single photo...
So, to sum up... Nothing complicated required at time of shooting. Your T2i is more than capable. Just get yourself a cable release that locks off :-)
You don't have to use Magic Lantern (ML) to use bulb mode with your Canon EOS Rebel T2i. There is an advantage to using ML which allows you to take bracketed shots without cycling the mirror between each shot. It may also allow you to take multiple images in burst mode (all at the same exposure level) without cycling the mirror.
To get into Bulb mode with the T2i, set the camera to Manual (M) mode and adjust the shutter speed (Tv) to Bulb. It is one click past 30 sec. (See page 83-84 of your T2i Instruction Manual)
If you are going to take multiple exposures and stack them as many do when creating star trails, you want to turn Long Exposure Noise Reduction (LENR) off. It is set under Custom Function menu II: Image. C.Fn-4 needs to be set to "0" (off). If LENR is set to "on" or "Auto", there will be a gap between each exposure while a dark frame is taken with the shutter closed. This is a very useful feature for single exposures when doing astronomical photography, but gets in the way when needing to do continuous multiple exposures. (See page 193 of your T2i Instruction Manual)