Comet 45P/Honda-Mrkos-Pajdusakova

It wasn’t easy but on Friday the weather cooperated and I was able to capture a glimpse of comet 45P/Honda-Mrkos-Pajdusakova.  That’s if you consider -10°C outside temperature to set-up a telescope and operate a laptop cooperation from Mother Nature.

In my previous post I gave myself a 2-day challenge to capture this comet as it was essentially the last few days at a decent magnitude 7 brightness before becoming non-observable as it swings around the sun over the coming weeks.  And when it returns to the northern latitude sky in mid-to-late February it will be dimer at magnitude 10.  In the image below, I labeled some of the brighter stars with their visual magnitude as reported by the Tycho-2 catalog.

Comet 45P/Honda-Mrkos-Pajdusakova

Comet 45P/Honda-Mrkos-Pajdusakova – around magnitude 7 on January 6th, 2017

I had a very small window of about 30 minutes to make any observation and photograph it.  The challenge started with setting up without polar alignment; the sky was still too bright to locate Polaris,  and instead relied on the position of Venus to align the mount.  As it was still twilight, I was limited to short exposures to keep the histogram on the left half on the camera and to make out a star from the background sky.  I actually started at ISO 400 with only 1 second exposure while adjusting the focus around Theta Cap (magnitude 4).  And as the minutes ticked by I was able to slowly increase my exposure as the twilight darkness permitted.  With neighboring trees, and rooftops coming into view I had to grab as many frames as possible. In the end I got 14 images with 6 seconds exposure at ISO 800 before calling it quits.

With such short exposures no chance of capturing any comet tail, but the green halo is unmistakable comet.

I hope to capture a few more comets this year.

Skywatcher 80ED
Canon XTi (450D)
14 x 6sec (ISO 800)
Registered and stacked with DeepSkyStacker.  Post-processing with GIMP.

December 25th – No Sunspots

The sun has been without sunspots for two days, but that is expected as we are heading to a minimum in the 11-year cycle.

Cycle 24 Sunspot Number

Cycle 24 Sunspot Number (NASA)

Nevertheless as it was a nice afternoon grabbed the scope and did some observation of the sun.  A little of a challenge to focus when there is no contrasting details to base yourself on.

December 25th 2016 - No Sunspots

December 25th 2016 – No Sunspots

Skywatcher 80ED
Canon XTi (450D) ISO 100 – 1/800sec
Thousand Oaks R-G Solar Film

DeepSkyStacker – Faster and Better Results (updated)

Tried DeepSkyStacker and I think I’ve found a better and faster way of processing my images.

I had been using IRIS for the better part of the last 6 years, and I remember how impress I was at the results compared to the early versions of Registax for deep sky images.  While  IRIS is quite manual and command-line based, it nevertheless got the job done and allowed me to experiment with different methods.  But now, I decided it was time to move on to something a little modern.  I looked at what others were using, and came across DeepSkyStacker.

DeepSkyStacker

While IRIS offers a complete package, from image acquisition, pre/post-processing, and analysis tools; DeepSkyStacker only performs the registration and stacking.  But it does so in a faster and more efficient way.  DeepSkyStacker can fully utilise RAM and multi-core processing; hence what took 30 minutes in IRIS is now down to 5 minutes in DeepSkyStacker.

It also automates many steps, and you can even save the process and create batches.  So it’s down to load all your files, and then one click to register and stack.

DeepSkyStacker - Processing Files

DeepSkyStacker – Processing Files

I tried the with some wide field of views I had taken back in September.  And the resulting image appeared to be better.  Now I still have to use IRIS as I like how it can remove the sky background gradient and adjust the colors.  And GIMP is still required for the final adjustments.  So here are the main steps that gave me good results:

  1. Load the light, dark, offsets and flat frames (I had no flats or bias/offsets in my trial run, but that didn’t appear to cause an issue)
  2. Ensure that all pictures are checked and select to Register the checked pictures
  3. For the stacking, I found that selecting RGB Channels Background Calibration provided good color, and used the Kappa-Sigma clipping to remove noise.
  4. After stacking DSS will create an Autosave.tif (32-bit TIFF file).  I need to convert this into another format, but without loose the dynamic range.  My current solution is to use Microsoft Photo Gallery to open and save another copy as JPEG.  Finally did a quick stretching of the RGB levels to ensure better dynamic range when saving to 16-bit TIFF.  16-bit TIFF appears to be the only one that will open correctly in IRIS.
  5. Once in the image loaded in IRIS to remove the background sky gradient.  And then save it in BMP format for import into GIMP.  Yes I know I another file format, so far it’s what I find works best.  GIMP converts FITS and TIFF to 8-bit, causing incorrect color depth.
  6. Final adjustments with levels, light curves, saturation, noise filtering, etc.. is done in GIMP.

Now for a little more playing around, and trying it on some on my older pictures.

UPDATE:
DeepSkyStacker saves files in 32-bit TIFF by default.  After stacking many images the dynamic range is quite large, and this is not data we want to loose.  But the problem was finding a program that was able to correctly handle the 32-bit file format.  The next release of GIMP (version 2.10) will handle 32-bit files, but GIMP 2.8 was limited to 16-bit and even there it would convert the image to 8-bit for manipulation (GIMP 2.9.2 and up might work, but needs to be compiles on your computer – development package).  Not good…  Before downloading yet another photo imaging software I tried some of my current programs and found that the  Microsoft Photo Gallery software for Windows 10 does a great job of handling the 32-bit TIFF files.  Once the image opened, under File – Make a Copy I save a version in JPEG.  Yes I know not ideal, but I avoid a lot of the quantization conversion error and I’m able to continue my processing in IRIS and GIMP.

 

Novembre 14th SuperMoon

Status

Lots of talk in the last week about the upcoming SuperMoon on November 14th.  While it will be the closest and largest Full Moon since 1948, the differences won’t be that significant.  It’ll look just like any other Full Moon, one that happens every month.  Nothing special will happen to the solar system or the Earth.

However it’s a good opportunity to experiment with your camera and composition as the Moon is rising over the Horizon.  Play around with different settings and different lens.  You can even spend the day before scouting a good spot with view to the East.

Don’t need dark skies.  Don’t need a special mount or stand. This is astro-photography accessible to all.

How Many Stars?

Image

Looking at the sky at night from your backyard you’ll probably be able to see about 50 stars, more if you are away from the city.  So how many do you think is in the frame below?

Portion of the Milky Way near Vulpecula.

Portion of the Milky Way near Vulpecula.

Taking a 200 x 200 pixel sample in the middle I counted 155 stars.  Hence extrapolated to the entire picture comes to 38,000 stars for this 18 x 10 degree portion of the sky.  OK I cheated in taking a picture of a portion of the Milky Way… Nevertheless that is a rather small fraction of the 300 billion stars estimated within our own Milky Way.

Bonus if you can spot the meteor!  Showed up in a single 30sec frame, which I added separately in post processing, else it would have been eliminated from the final image as it’s a random event and I always use a sigma distribution for my stacking.   Hint: it’s located just above open cluster CR399, also known as Brocchi’s Cluster.

Stitching Together the Milky Way

Image

To get a nice view of the Milky Way I would need to get far away from the city lights and a short focal, wide-angle lens.   Also most new DSLR are quite impressive in low light conditions to suppress noise at ISO settings above 1600.  My old Canon XTi (450D) is best kept at 400… but when stacking many frames I can go up to 800 as the noise gets reduced in the process.  Hence when planning of astro-photo session, you need to balance the level of noise and the number of frames you’ll stack.  Also ensure that the light pollution or background brightness level never exceeds 3/4 of your intensity level else you are clipping and loosing information.

The image below is two processed images taken with a 50mm lens on two different days (30 seconds exposure at ISO 800) stitched together the old fashion way: manually in a photo editor.

Milky Way around constellation Vulpecula

Milky Way around constellation Vulpecula – Benoit Guertin

Click on the above image for a a larger version and try to find the planetary nebula Messier 27.  Hint: it’s blue.

Apollo 11 and 17 Landing Sites

Image

What is the smallest detail of the lunar surface can I get with a 80mm telescope (600mm focal length) and Canon 10.1Mpixel camera?  Matching some of the smaller craters in a Moon atlas gives me roughly 6-8km/pixel.  But with image processing anything below 10km doesn’t really show or will blur in the noise.

I tagged a few geological features and dimensioned two craters for reference.  At the same time identified the approximate Apollo 11 and 17 landing sites.  The Apollo Lunar module is only 9.4m wide, hence it is impossible for any Earth bound telescope can possibly pick them up (even Hubble).  However the Lunar Reconnaissance Orbiter (LRO) did manage to pull it off by lowering its orbit as low as 50km above the lunar surface.

Apollo 11 and 17 landing sites and other features

Apollo 11 and 17 landing sites and other features. Moon (October 6th, 2016) – Benoit Guertin

My original photo of the Moon.