First narrowband image - North America Nebula H-alpha with DSLR

[Altais]

This week I was finally able to do some actual astrophotography. The few sessions I've had since March has been all about getting guiding to work (which it kind of does now), so this image is my first guided image. It is also the first astro photo I've taken with my DSLR after I modded it, and my first narrowband image.    Oh, and also my first time using a coma corrector, but I bought the wrong T-ring so the spacing isn't quite right (hence the slight coma in the edges).

The image shows the southern part of the North America Nebula, with the dark interstellar dust that constitutes the "Gulf of Mexico".

Here are some specifics:

29 x 8 min subs at ISO 1600, calibrated with dark, flat and bias frames, captured through a Baader 2" 7 nm H-alpha filter with a modified Canon EOS 1100D. Scope, mount etc. as per my signature.

I spent two consecutive nights capturing the subs. The nights are getting quite short here in Norway, so I only had a 2.5 hour time window for imaging each night, from about 0 to 2:30 AM. And even then the sky didn't get very dark, as the sun only was 10 degrees below the horizon at the most. Still, the H-alpha filter enabled me to expose for 8 minutes and get the histogram peak about one third of the way to the right when the background sky was at its brightest.

Before doing any pre-processing, I extracted only the red pixels from the Bayer CFA of each frame (both lights and calibration frames). I proceeded with calibration as usual, before stacking the lights with 2x drizzle, giving me back the original resolution. This and all further processing was done in PixInsight.

The full-resolution version can be found on my Astrobin page (see signature). Feedback and advice on improvement would be appreciated.

Hope you like it!

[michael.h.f.wilkinson]

Lovely image

[gorann]

I like it!!

And it partly answers the question I just posted in this forum: Is it worth while to use narrow-band filters on a colour camera, considering that you only use 1/2 or 1/4 of the pixels.

Will you also try OIII and SII to make Hubble palette pictures?

[Altais]

I like it!!

And it partly answers the question I just posted in this forum: Is it worth while to use narrow-band filters on a colour camera, considering that you only use 1/2 or 1/4 of the pixels.

Will you also try OIII and SII to make Hubble palette pictures?

Thank you Gorann. 

From my very limited experience I'd say it's worth while. Sure, the Bayer CFA causes a significant loss of resolution in narrowband images. But DSLR sensors often have more than enough resolution anyway. Color CCDs with small sensors will probably suffer more from this. In any case, the drizzle method, developed for restoring information in undersampled Hubble images, can do a very good job of reducing the effect of this resolution loss (provided that the subs are dithered).

I would like to try OIII imaging when I can afford a filter, but I'm more skeptic about whether SII is really worth it with an uncooled DSLR, as it's often very faint. Still, I might give it a go some time in the future, since I'll probably end up with a mono CCD that can use the filters anyway.

[johnrt]

It can certainly be done in Ha, as proven above, and some limited targets will work in OIII too. The main issue you're going to face is the fact the most targets OIII & SII signal is so diffuse and faint that you will struggle to detect it with a DSLR.

[toxic]

very nice indeed