Category Archives: Comets

Comet Johnson, May 15, 2017, 02:00 UT

Comet Johnson, May 15, 2017, 02:00 UT. 28×180 sec @ ISO 3200, Canon T3, Televue TV-85 at F/5.6. Star-Freeze version.
Comet Johnson, May 15, 2017, 02:00 UT. 28×180 sec @ ISO 3200, Canon T3, Televue TV-85 at F/5.6. Star-Streaks version.

I made it out to my dark sky site again on Mother’s Day, 2017.  Mom’s house was on the way there, so I managed to visit with her before my imaging session, which worked out pretty well.

Comet Johnson was my only target on this evening.   I used my Canon T3 with no LP filter at ISO 3200 with 3 minute sub-images.   That was about max for this particular night in that area of the sky.   A few high clouds interrupted me after about 8 shots, but I was able to continue shooting after they moved on.

I was hoping to catch a glimpse of the ion tail with a single exposure, but no luck in that department.   The LP dome to my northeast that the comet was embedded in was the limiting factor here.   Maybe the LP filter would have let me use longer exposures and I might have been able to detect the ion tail like that.

The 3 minute subs let me track the stars with only minimal pseudo-nucleus smearing, but anything longer and I would have had to track the comet.   That makes it harder to do star-freeze processing if the stars are trailed, however.   I either have to fix the trailing in post-processing or shoot a set of star-tracked sub-images.

Comet Johnson, May 15, 2017, 02:00 UT. 28×180 sec @ ISO 3200, Canon T3, Televue TV-85 at F/5.6. Close-Cropped Star-Streaks version.

Comet Johnson on May 14, 2017, 02:05 UT

Comet Johnson, May 14, 2017, 02:05 UT. 58×180 sec @ ISO 400, IDAS-LPS, mod Canon XS, TV-85 at F/5.6.

Here is another go at Comet Johnson from the city with my older Canon XS camera.  The light pollution was at a minimum with above average transparency and low humidity levels this night.   Still, being limited by the LP in exposure time made getting the ultra-dim ion tail and the full extent of the dust tail almost impossible.


Comet Johnson, May 14, 2017, 02:05 UT. 58×180 sec @ ISO 400, IDAS-LPS, mod Canon XS, TV-85 at F/5.6. Star-Freeze version.

I wanted to go to my dark sky location and shoot this, but the conditions were so iffy that I stayed in town.    Clouds plagued the area all afternoon and it was just before twilight ended that the skies became clear enough to image.   So, I probably could have done good away from the city, but the risk of it not clearing and wasting my time waiting for the clouds to leave was just too high.

Comet Johnson on May 13, 2017, 01:52 UT

Comet Johnson, May 13, 2017, 01:52 UT. 11×300 sec @ ISO 200, IDAS-LPS, Canon XS (modified,) TV-85 at F/5.6.

Here is another Comet Johnson image from my Bortle red zone location.   I used my older, modified Canon XS camera and ISO 200.  I had read somewhere that ISO 200 on the XS series was close to unity gain and I wanted to see for myself how sensitive it was shooting in the red zone LP at this setting.

I went with 5 minute subs with tracking on the comet enabled and got 11 before moonrise.  I probably could have gone 8 minutes in these conditions with ISO 200 to hit mid-histogram, but I stuck with 5 minutes since the histogram hump was still well away from the left hand side.   Plus, it was about 70 degrees this night and the camera showed lots of hot pixels even using ISO 200.   It would have just gotten worse with longer subs.

The comet was at a low altitude starting out, so the LP and atmospheric extinction hindered me getting the really dim ion tail and the more subtle parts of the dust tail.   With moonrise coming so soon, I couldn’t wait until it got any higher, unfortunately.

It is not a great image but not too bad, either.   At least I tested the XS and verified what it can do.   It is more suited for shooting nebula, since it is a modified camera, but I haven’t used it in so long that I forgot how it performed on comets.

Comet 41P on April 22, 2017, 05:28 UT

Comet 41P on Apr 22, 2017, 05:28 UT. 23×300 sec @ ISO 1600, IDAS-LPS, Canon T3, TV-85 at F/5.6.

Comet 41P was the main target I was after for my imaging session on the night of Friday/Saturday, April 21/22, 2017.    It has gotten further away from Earth and is therefore smaller, but it is still relatively bright.   I wanted to get it before it gets any smaller and dimmer.

It is still in the northern skies and circumpolar and thus visible all night.  I still had to wait for it to get high enough and out of the combined LP domes of Abbeville and Lafayette, LA to the northeast.    Transparency was only so-so this night and the LP was really noticeable.  Very humid, too.   Temps were in the lower 70’s/high 60’s during the night, so the camera was on the warm side.  The seeing was pretty good this night, however.

I shot 2 dozen images (about 2hrs worth) and only had to throw away one.  My mount got stuck again while tracking and I had to shake it loose.  The image that was finished right afterwards was no good due to that.  I think the overhaul of my mount is long overdue.    Another project that I really need to get done.   lol

Comet 41P on Apr 22, 2017, 05:28 UT. 23×300 sec @ ISO 1600, IDAS-LPS, Canon T3, TV-85 at F/5.6. Star-Streaks version.

Comet Johnson on April 22, 2017, 04:00 UT

Comet Johnson on Apr 22, 2017, 04:00 UT. 13×300 sec @ ISO 1600, IDAS-LPS, Canon T3, TV-85 at F/5.6.

Here is Comet Johnson again from a relatively dark site.   I did not devote much time to it since it was not my primary target this night.   It is only a little over an hour of integration.   Perhaps it was a little too warm to use 5 minutes/ISO 1600 for exposures, at least with this low number of sub-images.  But, I didn’t want to have to shoot two sets of darks, so I stuck with one exposure length all night long.

Comet Johnson on Apr 22, 2017, 04:00 UT. 13×300 sec @ ISO 1600, IDAS-LPS, Canon T3, TV-85 at F/5.6.