Monday, November 20, 2017



Corona During Total Solar Eclipse
August 21, 2017, Farewell Bend State Recreation Area, Oregon
by Stephen D. Blazier
I wanted to see how much of the sun’s corona I captured on that beautiful day, so I combined my deepest exposures during totality. My longest exposures are 1/13 second at ISO 1600 and f/13, using my Nikon D700 with an AF Nikkor ED 180mm f/2.8D IF lens coupled to a Kenko Teleplus PRO 300 DGX 2x AF Teleconverter, for an equivalent focal length of 360mm.  

I took 37 of these RAW images. I chose ViewNX 2 to color balance and convert to 16-bit TIFF for further processing.  To get the most out of these I needed to take advantage of both the 14-bit pixel depth and the signal to noise improvement from combining multiple frames.  I converted the TIFF images to floating point, aligned them using a Fast Fourier Transform algorithm, and then normalized them by offset and scale.  I used a sigma rejection to get rid of outlier pixels, and averaged the rest together.  I could have summed them, but since I was working in floating point, the result is equivalent.


Those of us used to teasing faint objects out of the noise have experience mapping from a higher dynamic range to the limited display devices available, but in this case, I wanted both bright and faint detail in the result.  I chose to learn about High Dynamic Range (HDR) processing.  
It was not easy.  I find most HDR documentation is either recipe based (e.g., specifying to click certain buttons in a program without explaining what they do, then experiment with a set of parameters), or analyze technical research papers.  

I chose a Debevec creation model, a triangular weighting function, and gamma response curve to produce the HDR image.  Other creation models produced somewhat similar results, but like most things with HDR, deserve further exploration.  To visualize this HDR image on standard devices, I applied Rafal Mantiuk’s operator, as described in “A Perceptual Framework for Contrast Processing of High Dynamic Range Images”, ACM Transactions on Applied Perception 3, 3 (2006), pp. 286-308.  

The result is interesting in several respects, but does not match our actual visual experience of the eclipse.  We saw an inner solar corona of pure white light.  I don’t believe any output device today can match the brilliance of that inner corona.  In my processed image, the corona spans across the field of view, but it faded into the twilight-like sky before that from our vantage in Oregon.  Moreover, we saw no hint of the Maria on the moon when we were watching.

Thanks for sharing your experiences viewing and recording the moments of totality with us. You went into another realm with complex post processing it seems. Well done. So far I haven't seen any real life amateur imaging that includes the Earth shine, except in a magazine. 
I think Stephen explained in a separate email that the bright spot to the lower left was Regulus.
Keith
















Sunday, November 12, 2017

A Bright Blue-Green Taurid Bolide Was Seen At Our November 10th Star Party


On Friday night November 10, 2017, I was helping out at Wayne Petko's "Canal Walk" Star Party at the Griggstown State Park.
There were four members with scopes and it seemed like more than 50 people came out to the "boonies"(if there is such a thing in the suburbia of metropolitan New York and Philadelphia) to brave the c-c-c-cold and slight breeze. We were at a fairly large, wide-open space near the old D&R Canal and although the night sky seemed a little bright from the ambient light pollution, there were more than enough cosmic objects to view. We were able to keep the public's interest ~ even in the sub-freezing temperature! My car reported that it was 22°F (-5.5°C).

People seemed to enjoy themselves and most stayed long enough to look through each scope and study what they were seeing. During one of my chats with about 6 or 7 people I mentioned that the Taurid Meteor Shower was peaking in a couple days, during the early morning of 13 November, and that we may be able to  see some even while we stood looking up at the sky.
As I was pointing out Taurus I mentioned the relationship with comet Encke and as we faced west, I motioned with my arm the directions a meteor may take from that constellation. Shortly, a huge bright blue-green bolide fell in the west, the same direction that we were looking. WOW!!
It was beautiful.... beside the awesome color of the meteor, it's reddish-orange trail and debis arced about 20° in the sky.

That was probably only the fourth or fifth huge bolide that I've ever seen since I started looking up when I was a young kid. Now that I'm retired, I guess my free time has it's benefits.
It was an awesome night even if I couldn't feel my toes and my face wanted to leave me there and go home!
Keith

Saturday, November 11, 2017

Diamond Ring
Before second contact, August 21, 2017, Farewell Bend State Recreation Area, Oregon
by Stephen D. Blazier

Exposure of 1/25 second at ISO 1600 and f/13, using Nikon D700 with AF Nikkor ED 180mm f/2.8D IF lens coupled to a Kenko Teleplus PRO 300 DGX 2x AF Teleconverter.  

Following the rays back to their source leads to a few different points on the limb, indicating where Baily’s Beads will soon appear.  The star in the lower left, almost speared by one of the rays, is Regulus.

(Stephen did a great job capturing the ray details.... well done!  ~Keith) 




Saturday, September 30, 2017

The Total Eclipse was fantastic!!!

About two years ago I called my childhood friend of 60+ years to tell him to put August 21, 2017 on their calendar. I was going to stay at his place for three or four days. Then because he was also into astronomy while we were growing up, I told him why ~ the best total eclipse of our lives was going to be centered about twenty miles from his house south of St Louis! As kids we saw the sun with a huge chunk missing during the June 20, 1963 eclipse as it passed near the Montreal part of Canada.... since then viewing a total eclipse was on my bucket list. This was a gimme!

During that time we planned everything possible, including scouting and confirming four or five sites within about 200 miles west of his place should the weather get bad for the eclipse.  Many local schools on the center path would not let us on their property to set up photography equipment and telescopes during the eclipse ~ it was on a school day.  I even told Principals that I would offer my experience as a member of  NJAA and a trained volunteer for Project Astro... respectfully they declined my offer. I think I was just asking too early.
Undeterred, I set out plotting places like state and local parks. Some wanted entry money and all warned me that I could expect huge crowds there.... ugh!!! But we had a plan, even if I had to park next to a gas station!.

Time went by fast and about a month  before the big day I got a call from my buddy. He asked me if I was married to the places we came up with so far. I got an uneasy feeling in my gut... was he going to tell me something came up and I couldn't stay there?

Instead he told me his daughter had a girl friend that lives on a farm and we could go there and view from within it's open spaces. He gave me the address and as soon as I could I looked it up on Google Maps ~ Wow! ~  We were going to be almost on top of the eclipse path dead-center as it wizzed through DeSoto, Missouri!

That made the rest of my month exciting. My only real concern was the history of the weather near St Louis in August. All data showed about 50-70% chance of rain was likely. Ok, so we still had our back up plan. The night before the eclipse the TV said there were 70% chance that it would rain so we packed up his truck and decided to take the chance with the farm in the morning.
When I woke up, I immediately got my Radar App going on my phone. Oddly enough all the clouds were gone and the radar showed nothing in the sky where we were going. Now we had to deal with the traffic... it's always something!
We headed out early for the half hour drive expecting it to become hours. Instead, we were lucky as there was only moderate traffic out of St Louis, so we got to the farm early.

After the introductions, I was told that about 15 other people were expected to come there as well... totaling about 25, including the kids and two dogs. Soon after I set up my new iOptron SkyTraker Pro and camera I relaxed. Having heard all the professional advice warning every "newbie" to take time to enjoy the changes in the environment and not bury their head in a camera, I decided that I would minimize my shooting to sense the moment as our spot had about 2 minutes and 40 seconds of totality and I was going to use it all!

I did take a few shots of the partial but I wasn't happy with the results as I couldn't seem to get a sharp focus on my Nikon's live-view screen. What I did want to get was the Corona and the "Diamond Ring". Then just before totality I noticed the security lights were on, the roosters were crowing, the temperature dropped, the bull was uneasy, and a cricket or two decided to join the fun as the dark shadow swallowed us up. The kids and adults were cheering and clapping as well as murmuring during the awe of the moment. 

I have checked it off of my bucket list and here is what I took.


Keith

Monday, May 8, 2017

Astro Imaging and Processing the Sun

This tutorial is taken from SkyatNight Magazine and written by Pete Lawrence.
I think this tutorial can be very helpful for our members that enjoy the Sun as much as the stars. 

STEP-BY-STEP GUIDE:

STEP ONE
Before pointing your setup at the Sun, check and fit your white light filter and remove or cap any finderscopes. Locate the Sun using your camera and focus on a sunspot or the limb (I recommend getting and using a dedicated solar finder or you can use scope's shadow... much easier ~ km). Center on the middle of the solar disk and check for overexposure – there should be no white visible. The levels meter should read just less than maximum.

STEP TWO    

Move the telescope (slightly) in RA. Orientate the camera so that features on the Sun move parallel to the bottom of the image frame. Push the front of the scope up, note the direction – the leading edge of the sun is the northern limb. Apply pressure to the front of the scope to push it to the West; the leading edge of the sun is the western limb.

STEP THREE   

if your software allows, reduce the gamma on the image to make the Sun's surface easier to see. A green or solar continuum filter over a monochrome camera can enhance solar granulation. Record 500 – 800 frames or each section of the Sun: make sure that captures overlap. Process each using a registration and stacking program.

STEP FOUR   

Load the first processed frame into a layer–based graphics editor and cropped off any white borders. Increase the canvas size with a black background to accommodate the final image size. Open and adjoining frame and draw a selection box around the image that cuts off the border. Paste this into the base frame as a new layer.

STEP FIVE     

Align the upper layer using surface detail. If there are no sunspots, try using solar granulation –  it's tricky, but possible! Move the upper layer roughly into position then toggle its visibility on and off to align. Once done, use the Curves tool to match tones approximately. Remove any share overlaps using an Eraser tool set to 10%.

STEP SIX   
Repeat for all mosaic frames then flatten the image. Taking a sequence of white light mosaics over several days allows you to reveal the Sun's motion: load each mosaic into your graphics editor, in order, as separate layers. Align them and set the blend mode of all upper layers to darken to show the spots on the layers below.

This all sounds good to me and should be easy to do in Photoshop, however I have not tried to use this tutorial. Above all be very careful imaging the Sun.
Keith

Monday, April 10, 2017

The Full Moon rising out of the clouds and mist

I noticed the full moon and Jupiter rising up through the trees and just out of the haze and clouds.
I managed to run to the camera without hurting myself or anyone else and propped myself against the garage door to get this shot. I took multiple shots to expose for the moon and Jupiter as well as for the clouds and then layered them together in the same location as the originals.
I decided to post the color and b/w because I haven't chosen which I like best.


Tuesday, March 21, 2017