DSO imaging out the bedroom window - part 2

[PortableAstronomer]

Since there was quite some interest in the previous thread

http://stargazerslounge.com/imaging-deep-sky/125003-dso-image-through-bedroom-window.html

...I thought I would take a closer look as to what artefacts come into the pictures from imaging through double-glazing, particularly when the scope is looking at more of an angle through the window.

The most obvious concern for me was the internal reflections of brighter stars between the layers of glass and you will see these in the images after they have been stretched.

And further down some conclusions

First up was a quick test at the old favourite for January, M42.

Images are as follows

- Quick shot from inside the bedroom looking outside, to give you an idea of my environment.

- A stack of 20x1min exposures, Equinox 80, WO Field flattener III, IDAS P2 filter, QHY8 CCD.

- The stack after processing in Pixinsight. Dynamic background extraction, histogram, some wavelet processing.

As you can see, despite the dust-donuts being eliminated using flat fields, there are some speckles appearing on the image as if water droplets were on the CCD window (but they weren't, no misting, no fogging).

These speckles could have been formed by reflected starlight, maybe something else. I'm not quite sure about this one.

As you can see, most people produce much better results by imaging outside! So not a very effective imaging session, but it was comfortable to be in the house.

The original "through the window M42" was much better (in the first thread)

Next I'll try some other targets.

[PortableAstronomer]

Next I had a go at the Flame Nebula & Horsehead region. Since the emissions were weaker from these sources, I feared they would get completely lost in the light pollution.

I didn't want to use up too much time as this was just an experiment, so I took a single 10 min exposure.

Images below are as follows:

- A *single* 10 min exposure, QHY8 CCD, no darks, Equinox 80, WO Field flattener III, IDAS LP2

- The same single exposure processed in Pixinsight to remove the LP. You can see the graininess from using a single exposure rather than having a nice stack of frames. But nevertheless I was pleased to see these targets considering the brighness of the sky from my location.

Obviously nothing to write home about, there are people on here creating stunning images with unmodded DSLRs and modest mounts, but I would hope they have better skies than this!

[PortableAstronomer]

Before I retired for the night, I pointed the scope upwards towards the Rosette nebula. This was at the uppermost limit (to see through the window); any higher and the scope would be looking at the ceiling.

Again as it was just an experiment, I took a single 10 min exposure of the region

Images below:

- A single 10 min exposure, QHY8 CCD, no darks, Equinox 80, WO Field flattener III, IDAS LP2, then processed in Pixinsight to remove the LP.

The graininess is obviously appaling, but it was a single exposure, just in case it was a flop I didn´t want to waste any more time imaging through the window if there was no point.

[PortableAstronomer]

My conclusions are no big surprises really:

- that the angle through the window makes a big difference, particularly if there´s double-glazing and internal reflections going on.

- however, do have a go yourself if you like, just start with a couple of expsoures, and compare with the same from outside. You never know, if your windows are Pilkington´s best then you might be surprised.

Clear skies everyone.

Regards, Chris

[xboxdevil]

It shows you that there is mileage in the "through the window technique", the only thing I've tried to look at through the window was the moon and that wasn't great to be honest, but as you're very well aware there is still something satisfying about being in the warmth :-)

[alaskacam]

Cool shots. I'm suprised at how clear these came out. Good job....