A Camera Comparison

Which cameras, you ask? Thank you for asking. In this case, it is a DSLR and a dedicated astronomical camera. You may be familiar with a DSLR, the digital version of a single lens reflex camera. I am using the camera used for the last installment of this blog, a Canon Xsi. It's really a uppercase X, uppercase S, lowercase I, but auto correct won't allow that. Moving on. The astronomical camera is a QSI 683, which is a cooled (as in temperature) camera used only for connecting to a telescope to take images of the night sky. The size of the sensor (ie, the chip) in the QSI is slightly smaller, but they are almost the same size. That difference is reflected in the size of the field each one images. For the comparison, I imaged the area of M81 and M82.

M81 and M82, Canon DSLR

This is the DSLR image showing both M81 and M82. Both are galaxies; M82 edge on, M81 more or less face on. M81 is in the upper right corner, M82 the small fuzzy spot in the lower left.

M82 identified

This is the same image, just showing M82 so it's definitely identified.

M82 with QSI

This is the QSI image showing M82. Obvious difference, huh? So what was the same in these two images? The images were taken on consecutive nights (I couldn't get both on the same night), the exposure time was 2 minutes for both, same telescope. Only difference was the camera. (Integration time was actually longer with the DSLR, which should have made for a better image.) I kinda like this image of M82.

M42 Redo, and a nearly full moon, too

Well, the holidays have passed, the kids and grandkids are back home. You would think it would be time for some astronomy. The clouds “think” differently. However, the night of January 12^th finally saw the parting of the clouds long enough to allow for a few images to be taken. It also allowed me to try a new toy that I got for Christmas: a T ring. What is a T ring? Thank you for asking. It is basically an adapter that allows a DSLR to connect directly to the telescope by replacing the lens. In effect,the telescope now becomes the camera lens. So, what did this test session produce? Let's see.

Really, you don't know what this is?

You don't need to have a degree in astronomy to guess what this is. The DLSR allows a fairly large field of view and importantly, a short exposure time. It's the short exposure time that allows this image of the moon.

A few minutes after the full moon image, I moved over to M42, the Great Orion Nebula. This area is, as noted before, a star forming region in the constellation of Orion. Noted before? When? Well, that would be September 24, 2016. However, the image taken then wasn't published. So, what did that look like? See below!

M42 taken with ZWO, the planetary camera

This image was taken with the camera I usually use for imaging the moon and planets. It's a “one shot color” camera that works like a webcam. It actually takes videos. Then the individual frames of the video are “stacked” to make a single image. With this arrangement, I can't guide the scope, meaning correcting for tracking errors, so the stars are slightly elongated.

M42 taken with Canon 450D, 10 Sec exposure

M42 taken with Canon 450D, 60 Sec exposure

Both images are were taken with the DSLR, but for different lengths of time. The first, or top, one is a 10 second exposure. The second, or bottom one is a one minute exposure. The top one shows the stars of the Trapezium better (that would be the four stars that looks like a little like a rectangle). The bottom one shows the surrounding nebula better at the expense of overexposing the Trapezium. These images are also unguided, but don't look too bad. All in all, I am pleased with the results of this experiment.