Sunday, September 17, 2017

NGC 7822

NGC 7822 is a young, star-forming region in Cepheus - some of it's regions are no more then a few million years old. It is 40 light years across and lies 3000 light years away above our galaxy. Inside the region is a supernova remnant - which indicates that a massive star in it has already exploded. Also, it contains one of the hottest stars discovered near our sun - it has a surface temperature of 45000 Kelvin (the surface temperature of our sun is 5778 Kelvin). It's luminosity is about 100,000(!!!) times that of the sun.

(click for full resolution)
I took the LRGB data (4.5 hours) at OSP and Ha and OIII (13 hours) in our backyard in San Jose. I used the Ha to enhance Red and Luminance and OIII to enhance Green and Blue.

When processing this image, I ran into something that I haven't experienced before. After stacking, color correction, background extraction and enhancing the images with my narrowband data) I ended up with the following RGB and Luminance image (stretched):
But when I combined them (using LRGBCombination in Pixinsight), I got this:

Zooming in reveals that applying the Luminance image indeed increased the detail, but it took out almost all color!

I tried this several times, finally asked around. And it turns out that LRGBCombination only works on stretched images! I have no idea why I didn't encounter this before - I am sure I had done this before. But once I did this, everything else went smoothly!!!

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

Friday, July 28, 2017

Weird APCC failure

Wanted to take more data for Sharpless-86, but ran into weird issues:
  1. Polar Alignment worked
  2. Started SGPro Sequence
When SGPro tried to center the object, APCC complained that the correction to be made is too large. Tried again. Same result. Then I tried to do just a "Solve and Sync", first I noticed that SGPro failed over to Blind Solve and then I got the same error again.

I then tried to do an Image Link in TSX. And ran into the same issue. Only a All-Sky link worked ...

Restarted the scope, restarted the computer - same result.

At some point I noticed that when a slew command was issued, the scope started slewing but the position in TSX did not update (it just sat at the Park 3 position). I tried a couple of things.

When I disabled APCC (i.e. connected the Astro-Physics ASCOM driver directly to the serial port of the mount) everything worked!!!

I have absolutely no idea what happened.

First, I didn't think too much about it and that I could just use the mount without APCC.

... but then I remembered that I wanted to use Horizons for the solar eclipse to make sure that the sun stays centered... and for that I'll need APCC. So, I still have to figure that one out...


After I posted to the ap-gto mailing list, Ray Gralak replied and a) asked what versions of APCC and the ASCOM driver I'm using, and b) recommended to update both to the latest versions.

I realized that I updated APCC recently but not the ASCOM driver. After doing that, everything seems to work. Yei!!

Monday, July 24, 2017

How to solar charge Li-Ion batteries

So, I bought two Li-Ion batteries for the field. They are definitively smaller and much lighter. I used them last night for my scopes. Everything worked great. Then I charged them with me 100W solar panels during the (very sunny) day. In the evening I tried to use them again, but both gave up very quickly.

Did some research and found out that they need special charge controllers as their charge profile is different. After lots of research I bought new charge controller from Morningstar. In about a week will I find out if and how much of a difference that makes...