Caveman Astrophotography

A few evenings became available so I dusted off the wobbly little manual EQ1 to have my first go at hand guiding since New Year. Hmmm, targets. Obviously have to think wide. Go deeper too. Rosette and that portion of the Milky Way appealed, but I had to get it early because of trees in that direction. Problemo – stuff up with slow motion knob hitting counterweight on one side or OTA on the other. Tried a few shots but gave up. Similar on other side of sky with Eta Carinae nebula and that area….

Ahhh, comets! Yes, give it a really good go, find out the limits of my primitive set-up (see last blog entry for details - Chapter 2). Try something relatively easy first – 8P Tuttle at something like mag 9.3. Using NexImage to guide with, you need fairly bright guide stars and there were none close to it. Ended up guiding off Beta Reticuli, a mag 3.8 star. Shot at 55mm in Sigma 55-200mm lens, to see if Tuttle was in the field. Took a single 190 sec test exposure, and there it was, just in the frame!

This is the full frame, LMC at top left, Tuttle is the tiny green dot halfway down right edge

Hmm, that wasn’t so hard. What about McNaught C/2007 T1, not far away but a whole lot fainter at supposedly mag 12.9? Yeah, go for it! This time I could guide off Eta Columbae, a mag 3.9 star only about a degree away from the comet. This time I took 7 200 sec subs, stacked them, and lo and behold a little green patch appeared – success, just!

Feeling like Superman, I was now confident of imaging any number of dim comets around the sky. McNaught C/2006 Q1 in Vela was next in line, a little brighter even at mag 11.75, so a sure thing! Took nine exposures of about 180-190 sec each, stacked them….. and…… NOTHING!!! What’s going on?

Next night I picked another very dim comet, Boattini C/2007 W1, at mag 13.0. Went longer, 3 x 240 sec and 1 x 306 sec, the longest exposure I’ve done. Stacked them… and nothing again! But I looked at the 306 sec exposure, and there was something there! Faint, but there. Through SCP Chat, I hooked up with Astroman, our resident Comet Imaging King, and he did better exposures of the area and picked it up in exactly the same spot. Thanks Andrew! But my image was, well, pretty fugly. No nice green comet there, just the faintest of blurred spots. Hmmm.

Next night, to round it off, I went for McNaught C/2006 Q1 again. No muckin’ around, camera wide open, a 310-sec guided exposure at 55mm. And? Yes, got a faint spot in the predicted position, but the shot was so bad it made my Boattini shot look almost acceptable (ah, nah!).

One more to try, even though my confidence had been pretty much shattered. This time, comet Skiff C/2007 B2 at mag 13.3. One 308 sec exposure, wide open. And nothing!! But it did faintly show mag 13.7 and mag 13.75 stars right slap-bang next to the predicted position for that time.

So what did I learn from my venture into dim comet photography? Well, first that magnitudes in the low 10s are being reported for T1, not the 12.9 I thought it was. Secondly, that I should leave dim comet photography to the experts with good gear, LOL! Stick to mag 10 or brighter, where I can keep exposures shorter (5 mins is too hard – hand starts to shake after manually guiding for 3 mins!). Maybe mag 10.5 as a nominal maximum.

Man, this stuff is great fun!!!!