On the night following the encounter between M108, Comet 41P and the Owl Nebula, the comet was still in the field of view of my setup, so I went back for seconds. I just couldn’t pass up the opportunity to shoot a comet conjunction again!
I went with 3 minutes sub-images at ISO 200, since the 1 minute ISO 800 subs were too cooked by the LP for my taste. Unfortunately, the sky was not as transparent as the previous night and that half-stop of underexposure was needed to get around that. The trade-off was I didn’t get as much of the comet’s coma. Oh, well.
Also, at that exposure length, the comet’s pseudo-nucleus trailed a bit, since it is moving with respect to the Earth and stars and slowly picking up speed as time goes on, to boot. It was not enough to notice if I carefully over-exposed it a bit in processing to make it fatter, luckily. Check the star streaks version, which I did not overexpose, and you can see how far the comet moved in 3 minutes:
A Televue TV-85 w/0.8x focal reducer/field flattener, a Canon T3, my laptop running EQMOD, driving my Atlas EQ-G mount and PHD2 Guiding with an Orion StarShoot guider/Orion Ultra-Mini guidescope was some of the equipment used.
It is not uncommon for comets to pass near famous Messier objects or NGC catalog objects and put on a good show. This comet encounter is special in that there are two famous objects that the comet is having a conjunction with. One is a relatively bright galaxy called M108. The other is the Owl Nebula, one of the better planetary nebulae in the skies.
I shot this with the Canon T3 and Televue TV-85 combo. I used one minute sub-images at ISO 800 and that was about max for the skies I was under. I’m sure people with darker skies got better results. However, I think being able to pull anything out of the skies at this location is great. LP was bad and I had terrible gradients to deal with in post-processing, but I managed. 🙂
I also did a quick star-streaks version that seems to show a longer tail. Not sure, since there were some dust doughnuts left over from an apparently bad batch of flats I used and I had to clone them out. These aberrations were in the tail area, so it could be some remnant of that.
It was Friday, March 3, 2017 and the weather was iffy for imaging at my dark sky location. So, I decided to stay in town and try some short-exposure imaging with the Toupcam color planetary/guider cam I have.
I also wanted to try out an adapter I purchased for the Orion Star Shoot so that it can work with the Orion Ultra-Mini, 130mm, F/4.3 guider scope I’ve been using. This worked better with PHD2 than I thought it would. It seemed more accurate than the Toupcam with less dropped frames. In fact, I’ll probably leave this as the permanent guider setup.
For the Toupcam, I used a two inch extension on the TV-85 at F/7, but I still had to let the cam and extension hang halfway out the focuser to even reach focus. But, it was stable enough to try some simple targets like the Orion Nebula.
I used a software program called SharpCap for acquisition, dark subtraction and stacking. It worked well enough for M42, but it had trouble with stacking dimmer objects like M46, an open cluster with plenty of stars in it. I used IRIS to stack the individual frames manually for that one.
The last two images were tests of a relatively dim galaxies, like NGC 4565 and M64. I only got 16 frames for NGC 4565, so it is not too special. But, it shows the galaxy well enough to recognize what it is. Like the previous image, it was also stacked manually in IRIS.
For my M64 dim galaxy test, I accumulated 38 frames @ 8 sec each. It was also a test of using a video file format called .SER that was designed for astronomical imaging. It is like a video file. After I downloaded a SER viewer/player, which also let me export the frames out as TIF format, I was able to bring the data into IRIS and stack.
Here is another one of those experiments I do. LoL. This time it was with a software program called SharpCap. It can capture images from planetary/guider cameras like the Touptek, ASI or ZWO cameras. Sharpcap’s claim to fame is the ability to stack the images you take on the fly so that you can almost get a “live-view” like experience. I thought it was neat and easy to use.
This is only 7.5 minutes worth of exposure, so it is not really that deep. But, it is interesting to be able to get this much with an under $200 camera and a small finder scope.
I also captured 7 x 15 sec exposures of M13 in a live stack. Not quite enough data in the stack for good star colors with just 1.75 minutes of exposure , unfortunately. But, it shows the globular well enough. Check it out:
I needed to test guiding with exposures of 3 minutes or longer, so I used NGC 2903 since it was in a convenient location. This size object needs more image scale to show it better, of course. But, I kind of like the wide view that shows the galaxy and star field in context.
Btw, in this image, north is to the left. Also, if you noticed, another small galaxy, NGC 2916, is also visible in this image. It is below and slightly left of NGC 2903 in this view.
Images of Comets, Nebulae, Galaxies and Star Clusters