I had been wanting to try imaging 46P with the 200mm telephoto lens I have. I thought I could bust through the LP with the addition of the Lumicon 72mm Deep Sky filter that fits that lens. Oh, well… not enough pass-through for the comet wavelengths and blocking of the LP. It helped, but not enough in the white zone I was shooting from. It works for H-Alpha nebulae, but not much for other stuff.
After a long spate of cloudy and wet weather, it finally cleared enough for imaging on the night of Jan 4th/5th, 2019. My last imaging session was just before Christmas, so it had been a while.
The imaging went reasonably well, just getting home was a little difficult due to car trouble, but I made it. Then, I locked myself out the vehicle before I could unload my stuff. Doh! Oh, well… $60 bucks later I was busy working on this image (without getting any sleep, either. ) 🙂
After doing the above images, i did another take on the star-freeze version with this cropped and more gaudy version below. I think it catches more of the extent of the whole comet like the star-streaks version does:
Speaking of the star-streak version, the one I did below is almost pristine. I barely did anything to it. It shows the ion tail much better than the first star-freeze versions, too:
Terrible conditions (and location) for this imaging session. I tried several things before settling on one minute sub-images as my best bet for the conditions. (Bortle 7/Orange zone, high-altitude jet stream clouds with bad seeing and temps near 60 degrees, which while nice and cool for us, is a bit warm for a Canon sensor inside a camera body. )
What can I say? At least there was some photogenic aspect with Capella in the image. Processing was difficult with lots of residual noise from all the LP, clouds and warm temps. But, it was an opportunity to image. Late December usually doesn’t offer much in the way of clear night time skies.
After these 1 minute subs, I took a chance and shot 20 x 300 sec images at ISO 100 while tracking the comet with the guider. I was able to add those in to the above image and I came out with this as a result:
The first shots of the night of Dec 10, 2018 were some 30 second ISO 6400 sub-images of Comet 46P/Wirtanen and the last 4 shots were 5 minute subs at ISO 3200 of the same, but guided on the comet instead of the stars. I mixed in some 60 sec ISO 6400 and ISO 3200 subs in the middle. The first image above is a combination of three sets – the 300 sec ISO 3200 subs and all of the ISO 6400 ones. The second image is just the 30 second ISO 6400 subs alone in a star streaks rendition.
Before I could even start shooting, I had to take the mount apart in the field and unstick a stuck motor that was giving me lots of trouble. I almost thought I would scratch and not get any shots of this naked eye comet. Luckily, I had tools and was able to rectify the situation.
I had trouble seeing the comet naked eye at first, but as soon as it rose high enough out of the muck, I was able to spot it without optical aid. I was at my Bortle 4/Green zone site and it was probably the clearest night so far this season. So, conditions were exceptional and it was cold enough (down to 37 degrees F) to use ISO 6400 without too much noise.
I still have one other set of 1 minute, ISO 3200 subs left to process. I’ll probably be updating this post later after I do them.
Yep, I was able to get these 40×60 sec ISO 3200 sub-images calibrated and stacked. Here’s the result of them by themselves:
Not too bad for 1 minute exposures. Color could have been better. Oh, well….
For an encore, I have this animated GIF showing the movement of the comet for just under an hour of time:
While the comet is moving and will blur if you expose too long while tracking the stars, you can also track it and expose for much longer. I tried 5 minute ISO 3200 sub-images and managed to get 4 like that before I tore down the rig. Here are two of them together for a total of 10 minutes of exposure:
Finally, here is the set of 40 x 1 minute ISO 6400 sub-images with a little bit of the above data and labels describing the image:
I was surprised at how well ISO 6400 worked out. Usually, it is too warm to shoot at this setting. It was 37 F when I got back to my place and shot the darks. I just left the scope outside and did them while I napped. It was probably a little warmer when I took these subs, but close enough to calibrate the extra noise out of them.
Here is 64P/Swift-Gehrels, a comet that was near M33 recently. I missed it then, but I finally caught up with it Saturday night, Dec 1, 2018.
I used 4 minute subs and I could have gone even longer at this location, but my guiding was iffy with bad seeing. Out of 20 minutes of subs, I lost one, so this is only 16 minutes of exposure.
Since it was so few, I just stacked the subs once while aligned on the stars and then used one sub of the central core to hide the streak caused by the comet’s movement in the sky. A quick and dirty star-freeze job. lol 🙂