Thursday, August 31, 2017

LBN 468

This nebula is 1,600 light years away from earth. One of the most interesting parts of the nebula is the bright part in the middle right. This nebula is called Gyulbudaghian's Nebula. It is a bipolar reflection nebula that is illuminated by a proto star.

(click on image for full resolution)
This is unfortunately only one half of the whole nebula. I wanted to take a mosaic of this but the last night at OSP didn't have good skies and I couldn't take enough data of the other half.

Eclipse Corona Image

Here is my main image from the solar eclipse:
(click on image for full resolution)

This was my biggest challeng: to process the 3 bracketed image sets that captured the corona of the sun. The corona has a very high dynamic range. My first tries to use any HRD algorithms (in Lightroom, Nik HDR Efex...) did not go very far.

I found a couple of useful tutorials on the web:
They all employ a similar workflow:
  1. Align all images precisely
  2. Create a composite image of the sum of all individual images
  3. Run a radial blur filter or a Larsen-Sekanina filter of the composite. This will create an image with all the detail but low contrast (mostly grey or black)
  4. Multiply the sum image with the detailed, low-contrast image
  5. Make final adjustments (stretch, curves...)
Fitswork has an interesting approach: pick two images, overlay by subtracting one from the other, this will make it easy to align them. It does work. ... but I found it too cumbersome. I was looking around for another solution and found the FFTRegistration (Fast-Fourier-Transformation) script in Pixinsight. This is often used to align comet images.

Enter a reference image, add all the images, I wanted to store the registered images, so I checked this and click "OK". ... takes a while and this was the result:

I took this image into FitsWorks and selected the Larsen-Sekanina Filter:

There are only two settings:

Rotation and Radius. The tutorial recommended to start with Radius=2.0 and Rotation=1.31. I chose those settings and got this result:

It has a lot of detail - and almost not other information (low contrast, wrong colors...)

But multiplying both images gives this result:

Doing a simple stretch:

And some curves, saturation and color adjustments:

And then some final tweeks in Lightroom (devignetting, cropping...)

Sunday, August 27, 2017

No Temperature reading from secondary FLI focuser port (flifoc1)

Last night, I took narrowband images of Cederblad 214 to augment my LRGB images that I took at OSP. This morning I was surprised that most of them were badly out of focus. On further inspection, I noticed, that SGPro never refocused. The only time it did was when it changed from the Ha filter to the OIII filter.

.. I checked the autofocus settings and was surprised that the temperature-based option was greyed out ...

... then I realized that the focuser did not report any temperature reading at all ...

... then I remembered that the camera disconnected last night and I had to reconnect through the secondary FLI port.

And, yes, that was the reason: when using the focuser through the secondary FLI port (flifoc1), there is no temperature reading - only on the primary one (flifoc0).

Learnt something - and I have to throw away most of the Ha images (the OIII images were taken after 3:40am when the temperature was much more stable).

Monday, August 21, 2017

Solar Eclipse - quick and unprocessed

I have to do some processing and will write up more about the amazing experience that was this solar eclipse. But here are some of my favorite photos:
Our camp at OSP during totality

The Diamond Ring

The corona during totality

Baily's Beads