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I hope you'll indulge me in a longish story of how I became a comet cowboy, or “How to tell you're a geek...”
...One way of telling you're a geek is when you spend most of the off hours of the week planning for the public observation session of your astronomy club on Saturday night. With a small 90mm telescope, my options are limited. It's great for planetary observing, but everyone goes for planets. I can do clusters, too, but others go for clusters and I can't compete against the beautiful gear others bring which costed multiples of my own setup. I'm glad it's not a competition, but still - can I find something that others aren't doing that night?
I found a hunt. There are sites out there to help, like http://www.aerith.net/comet/weekly/current.html which report on current comets. Here's a cometary target I could go after: C/2014 Q2 (Lovejoy.) It was magnitude 3.7 back in January, this is very bright and could be seen with the naked eye if you knew where to look and were in the right hemisphere. (Thanks Heaven's Above.com for the below!)
It's fading now. Magnitude 10 and decreasing per the references. Dim. But crossing high up at 9:00 PM between constellations Draco and Corona Borealis, between stars Tau Herculis and Nekkar in Bootes. (Thank you http://cometchasing.skyhound.com/ for the great finder charts using a program I'll have to get! The arc in the center of the star chart above is the path of the comet in August.)
One little spot of trouble.... my telescope has an upper limit somewhere around 10th - 11th magnitude on good nights. I really doubted my ability to see the comet through the scope... and I was really uncertain of photography through the telescope on a blind target.
But Oceanside Photo & Telescope finally got in my backorder of a 100mm set of scope rings. After a trip to Lowe's for a longer screw I was able to get the ring around my 104mm tube. Which meant I could attach my digital SLR camera with its' own 300mm lens piggyback on the scope mount, thus giving much wider area shots of wherever the telescope was pointing. (Plus added weight on the scope end, which I've desperately needed. My telescope is really way too light for the mount it is on.)
So the week went by with my studying the object track from SkyTools 3 courtesy of the Skyhound website and my Sky & Telescope's Pocket Star Atlas chart. (Wishlist note... the larger laminated Sky Atlas 2000... but at around $100 I'll save up for it. Geek, see?) There are enough magnitude 5-7 stars in the neighborhood to get me by for tracking into it, I think, which means I can use my telescope's wider angle finderscope too.
Saturday comes... and the clouds roll in during late morning. It is overcast. Grr.... I agonize all day long about whether I'm going to go through the effort of loading up only to discover no joy, or take the risk of wasted time packing and unpacking. Finally I decide based on the forecast saying the clouds will go away in 2-3 hours to pack up.
Even though my telescope is tiny, it's still a lot of gear: Motorized mount head box, counterweight/scope/finder box, 35 Ah battery, tripod base (each of these about 20 pounds,) eyepiece and gear kit, tool kit, camera bag, go kit (including paper references and Tootsie Pops), two laptops, red shields, external keyboard and trackball (really need a computer stuff box...) But I always take too much stuff along, wherever... according to others.
I really left a little too late at 7 PM, I should have been on site at 7. Twenty five minutes for the ride and I've got an hour before the presentation begins (which I like sitting in on.) And as I'm unpacking and setting up I've got people chatting with me, slowing me down a little more. But it is fun... Oh well. Maybe the skies are lightening up a little, but it's a small patch of blue in the overcast.
I get just about where I need to be, mount set up, scope mounted, mount powered, field desk out, camera mounted to scope. It is still light enough that I can focus on the observatory dome and adjust the camera focus pretty well. And then I find the primary laptop battery is discharged. Argh! I need a laptop to control the camera's exposure and give me the laptop screen to look at my results instantly on the big screen. Well, so glad I've got a cigarette lighter plug charger and a spare socket attached to my battery. Fire up laptop and throw the red plexiglass shield on. And now it is 8:35, getting darker, and the presentation is beginning.
Around 9:00 I come out (before the presentation ends) and look up and see mostly clear skies. Yes! Now I feel wholly justified in bringing the gear. Time to begin scope alignment procedure. I wanted to be careful with this - good scope alignment means life or death in finding what you're looking for. But I didn't do what's called a “drift align,” which is using the camera to test that the tracking is dead on. (Actually, I've never done a drift alignment - keep meaning to try that.)
First I use my polar scope (a tiny scope located in the mount itself) to line up to the North Star. Then it's time to tell the scope what time and date it is and let the scope give me alignment targets: time to fine tune and calibrate the stars Arcturus, Vega, Caph, and Dubhe through finder and scope. Done but it takes a bit. I tell the mount to go find Edasich (Iota Draconis.)
Often the alignment is a bit off. So I use the finders to try and verify - hey, a bright star! And on Draco, that looks right. Now which star is it....? Oh, it was actually Edasich - apparently I have an excellent calibration because I'm close to dead on.
Now, the hunt! It is 9:40 PM. I take a 30 second photo through my 300mm lens and look at it on the laptop. Hmm... a little streaking - a drift align would have fixed that, but it's good enough. And there's both Iota Draconis and a couple of stars I've learned. OK, move a bit Westerly.... and here's a a bent L shape. Another move and shot, and Yes! It is a sharp triangle of 5th Magnitude stars that I know very well from the planning - I know right where the camera is pointing!
Another drift, and I'm a little uncertain of where I am... Could I have drifted a little too much towards the horizon? Well, if I did then I have to come back up higher and still further westerly... Hey, could those three stars be in my target region? Not sure - it's a square projection I'm looking at and the sky is a hemisphere.... Maybe just a little nudge.
In the meantime, I've been steadily talking with people since the presentation ended at about 9:45, describing what I'm doing, letting people look at my photos on the laptop screen and compare them to my finder.... While actually trying to work on something I've never tried before.
Hey, that little nudge just gave me not only the triangle of stars in the breadbasket but also a parallelogram of stars. I have very little doubt I'm in the right place.
It is 10:05 PM, and it is time for a camera run! I set a string of 20 photos of 25 seconds exposure each, 10 second pause between shots to cool the sensors and dampen shutter vibration. At 10:18 PM the run finishes. Now, the tricky part: Put the lens cap on the camera without touching the focus. Why? Because every camera has “hot pixels” - isolated red/blue/green pixels that are either always on or uniformly prematurely activate due to heat. And when stacking multiple photos, those pixels will show as a line of dots. So, we take dark shots with the lens cap on, at the same exposure time and settings and focus. But the lack of light will make nothing but those hot pixels show up and we can thus remove those pixels later from our photos. I take a series of five.
I see nothing of a comet in the photos. (The photo above was the first of that run.) Oh well. I know I'm in the right spot, I'm as sure as I can be... I guess.
OK, a small reposition. Let's see what happens if I fire a 120-second exposure. Ack, no! More stars but way too streaky - my alignment doesn't hold up to that long.
OK, try another run of 25 second shots! As the camera fires up, for me it is break time and I can wander around a little to see what others are up to. The dipper from a Dobsonian, M22 from Tim's refractor, wander around a little.
My computer goes ping! The run finishes at 10:42. Another string of darks. A little time for water and rechecks that I'm in the right neighborhood. Then another run, but 35 seconds. The public has pretty much left and others are packing up. I realize after starting it that the streaks are too much at 35 seconds. It's now 11:30 PM. I'm thinking about one more grand run, at least 30 minutes of 25 second exposures.... When the club historian comes up and mentions that some of us are going to Denny's now.
Well, I can't turn down a chance to jaw at Denny's! I think I've got enough photos. No obvious comet in the photos but that's OK - I still think I got the spot. It takes me about twenty minutes to crudely break down my gear and get it back in the car, but everyone else (except one other person who's staying) is gone.
Denny's was fun! (Ah, the nostalgia of going to Denny's at midnight during roleplaying game days during undergrad or after finishing a term paper during grad school. But now with new astronomy friends. See, Geek!)
A few hours sleep after some good conversation and it is time to review the sixty or so photos taken. (And a chance to go through every box and repack properly from the crudeness of the night before.) I use a program meant specifically for group stacking deep sky photos... and I find the streaks are too big - the program doesn't recognize the stars as stars.
OK, manual processing time! Which I've only tried a couple of times. But I reread the tutorial, fire up GIMP 2.0, and combine some images. Brighter, but I'm not sure... So let's do a raw fast run of twelve or so... And hey! There's something there amidst the noise. Definitely worth going after further, tomorrow.
Monday night and I take the first run of twenty. Set the zoom at 400%. It becomes a routine: Open the photo. Open the best dark frame of hot pixels. Issue the command to subtract away the hot pixels from the good photo. Combine the two. Export the result as a fresh JPEG. Twenty times. Geek requires dedication.
Then open all twenty photos together. Had I mentioned that because the alignment wasn't perfect all twenty photos are offset from each other? All the stars shift a little right in the camera frame each shot. So each nice clean photo has to be aligned with all the others. Twenty times over: Set program to display two photos and subtract where pixels are identical, unlock the second photo so only it moves, move the second image over the first until the reference star is completely blacked out, lock the pixels, release first photo and view next photo in stack, change settings and repeat the overlay process nineteen more times. (There's a reason we like computer programs to do this stuff for us when possible!)
Now, moment of truth: Set each image to add brightnesses - allow each subsequent photo to brighten the lit pixels of the next. Make it brighter than you've ever done with any image before. Keep combining until noise from the camera is painfully obvious and this is no astrophoto that should be shared. And I got this, zooming in and cropping:
That stacking sure does make it brighter - can you see the same triangle? It's almost the same field of view as the earlier photo. Look at how all the dimmer stars came out! But maybe you didn't see what I did, though. I'm concerned with the dead center here (or the spot just right of the bright white star in the triangle.) Let's zoom and crop a bit further:
One little grayish blobby bit that washes out on zoom. A blob. Not a pretty cometary body, but it's bigger than just a star at that brightness - you can see points of light about as bright to the upper right and upper left of it that are stars. Could be a real faint galaxy, seems too small and faint to be a nebula, but if I'm in the right spot my star atlas shows no galaxy here. It does seem to be circular-ish... Can I prove what that little blob is... hmmm...
Well, until now I've been dealing with a track of the comet, a line showing where it is every night of August and I think I'm close but it is a line and I want a point... To check I go to a website called TheSky Live! It lets me set up where comet C/2014 Q2 (Lovejoy) was at specifically 02:30 Universal Time on 16 August (which was 9:30 PM.) Not only does it show me a map of the location, but more importantly it gives me exact coordinates of where the comet should have been there and then. Now over to my planetarium program, Stellarium (a free download, BTW!) Zoom in a bit and swivel it around until I'm look at what is at 15 hours 27 minutes Right Ascension and 50 degrees 47 minutes Declination:
I've brightened the triangle and parallelogram stars so you can see them here and added a red dot at the target... That's the same triangle and the red dot is where the comet should be. That little smudge in my photo is Comet C/2014 Q2 (Lovejoy.) SUCCESS!!!
The smudge is dimmer than other magnitude 10 stars in my photo. But the comet keeps moving - not all that fast (even for a comet.) It moves at a faster rate than the background stars do, so lining up all the stars tends to smear out the comet image. Without knowing the exact direction of comet drift I'm not sure how to get it better. The pixels don't show in the individual photos - only when I stack does it appear. I spent more time over the next couple of days double checking, though, as I did expect it to be brighter than I had in my photo.
I don't know - I'm just the most junior comet rustler still trying to recognize that I just had a personal best in astronomical discovery. Every check I make though suggests that yes, this is in fact the comet.
On Tuesday night I process the other two image runs and they're consistent. Finally, I stack the three photos of the three runs together. The noise of overexposure gets commensurately greater. And on Wednesday I do reprocessing through my imaging programs GIMP and Faststone to try to get some noise control. That gave me the following four images:
And now it is Thursday night.
Want to really know how you're a geek.... You're not sure if anybody will read your long screed that really only matters to you. Probably 6-7 hours prep time, 6 hours on site time of steady work, and 12-15 hours imaging work and writing. And, oh yes, it is worth it and the time just flies by as the work goes on.
It's not like I just discovered Pluto, or even discovered Comet C/2014 Q2 (Lovejoy.) But it was oh so fun stretching my horizons as an amateur astronomer. Maybe you already spend nights with your scope, or maybe I can convince you just how fun it is to try your hand at it.
Now.... what's the next target? Geek. See!