Ad Astra Observatory

Well, it happened again. The dawn of a new era in Hilltop Observatory.

Today, the new imaging camera showed up in the mail. I bought it from Renaud Venne Landry, one of the best in the modded DSLR business. When I ordered a modded T3i from him, he picked up a used body, and modded it for me. Very friendly, nice guy, great communication.

The camera arrived in beautiful condition; I cannot find a scratch on it.

I decided to try a treatment of the same targets I’d so recently (and to some effect) captured with the 350D. This sort of side-by-side comparison thing helps me to grok the new gear, comparative magnifications, etc. Also because, test drive! woot!

I think it works pretty well. Here is M27 again, 2 min subframes this time; 5min were overexposed(!):

Here is a full-zoom center crop:

(compare this to the M27 full-zoom crop from the 350D from last week, copied again here):

So far, this seems like a strong addition to the stable, and I look forward to getting to know the sky through this pair.

For those interested in the more nitty-gritty technical details, the new camera is a Canon T3i (600D), 18 megapixels, producing 5202 x 3465 RAW images. It still has a APS size sensor, approximately 23.7mm x 15.6mm, so the images are more magnified than a full-frame camera would produce. The tiny, tiny pixels might end up being a challenge to fully utilize under suburban skies, and will certainly require the best possible effort from the mount and guider. Although the sensor is the same physical size as the 350D, all the extra pixels also produce extra magnification to the tune of 0.577 arcseconds-per-pixel when shooting through Trixie. It is axiomatic that 2″/px is an easy throw for amateur equipment, but anything 1″/px or below can be quite a challenge. Time to bring my “A” game.

Most Canon cameras have similar focal plane distance, so when I swapped out the 350D and popped the T3i in place, the new camera was already very close to being in focus, enough that Vega still had diffraction spikes. Eight of them. 🙂 (the eight converge to four when in focus)

After a little Focusing and a little Plate-solving, Vega was centered in the frame, so I shot a series of 5min unguided frames. I intended to post them, to show the difference in FOV from the new camera, but when I looked at them side-by-side, I wasn’t really seeing a huge enough difference for it to be worth it. Seeing identical crops of M27 is evidence enough of the extra magnification.

The 350D had a good, if somewhat brief, run. When I upgraded from the 300D to the 350D, I was amazed at how fast the images downloaded (USB 1.1 vs USB 2.0). The T3i is back to being noticeably sluggish in getting all 18 million of those pixels sent across the wire — I haven’t timed the downloads, but they are loooong.

The imaging software I use writes some fairly bloated files, I’m not sure why; the 350D photos were 27mb each. The T3i (which has 2.25x as many pixels) produces 100 megabyte files 😮 I have had to really think about my stacking workflow, because it’s pretty easy to fill up 4 gig of RAM with such big subframes.

One nice thing about the T3i upgrade is that it can do full Bulb exposures using only its USB port, which both saves a wire going up to the focuser (from the bulb shutter cable), and also removes a big USB module from the wiring stack (same bulb shutter cable). The mount still has a severe case of cable-itis, but every little bit helps.

Now that the 350D is being sent “to the showers”, I’m not sure what I’m going to do with it… perhaps I will take up IR bird photography…

Welcome aboard, T3i. The king is dead; long live the king!