M13, The Great Cluster in Hercules

I took 50 flat frames, and used the 6 darks taken last night, as well as 50 bias frames, and calibrated and stacked 16 images (each 60 second exposures), and combined them in MaximDL to get this image. No other processing.  The colour could be improved, as the data is there, but requires increasing the saturation.  This would bring out the blues and reds in the stars better.

Setting Up for Flats

C8 with cameras and cables (I always tidy the cables if I am going to image,  but with the clouds, it wasn't necessary)

The clouds have returned, as forecast, but I set up anyway as I needed to take some flats to enable calibration of the images I took yesterday of M13.  I took care not to change focus, or to turn the camera, or make any other changes to the telescope.  I have found the skyflats plugin for MaximDL written by John Winfield to be an excellent little tool for getting flats at dusk.  The plug-in automatically adjusts exposure length to compensate for the declining brightness of the sky so the average ADU of the flats are within the range required (approximately 25,000 ADU for my QHY8L).

 I also find sky flats better than the light box I built; probably something to do with the LED light source I used not having the right spectrum of light.

After the flats were taken, the sun lit up the clouds over south east London:

C8 at Sunset

I've left the telescope set up as there is a possibility that the clouds will clear at 11pm, and behind the strom front could be a window of opportunity... Until then I will process the shots of M13 I took last night.

Typical Night Imaging

As many people publish finished (calibrated, stacked and processed) images, I thought it would be more educational to show a screenshot of what I see when actually imaging (this is what I would like to have seen before I got into this time-consuming hobby).  This is the part of astronomy that I enjoy the most, except perhaps that eureka moment when processing a series of images and teasing out the detail of an image that seemed invisible, but there have been very few of those so far...

PHD Guiding (above) and MaximDL Image Capture

The 2 monitors above show the guiding software (PHD) tracking a star while the imaging software below (MaximDL) controls the camera.  The image in the bottom left is a raw CCD image of a 50 second exposure of M13 (The Great Cluster in Hercules), a globular cluster in the constellation of, you've guessed it, Hercules.

It's actually pretty pointless doing this imaging, as the "seeing" (the quality of the atmosphere) is so appalling that the resultant stacked image will be blurry and without definition or colour, but as I have just reattached my mount to the pier, I am checking to see how well it tracks or guides.  As you can see from the red line on the graph the telescope is drifting away from the target.  This tells me my polar alignment is not very good, but probably adequate for such short exposures, especially when I'm going to delete all of the images.

I was going to image M101 tonight, but this happened:

Satellite Track Ruins Image

No, not the satellite track across the image.  Look closer, follow the arrow before the satellite track, and the bright spot is the core of M101, a spiral galaxy (that is usually readily visible after a 120 second exposure, which is what this is):

Closer look shows M101 hidden behind mist, cloud and poor seeing

It's barely visible, which tells me the "seeing" is rubbish.  It's hazy, misty, and the pollution (dust and particulates rather than light pollution) reduces the amount of light getting to the telescope from the object.  So it's simply not worth trying to image anything faint.  Hence I turned to M13 (which happens a lot).  The other globular clusters, which I have become all too familiar with, are M3, M5,  M92.... see for yourself - this is how I find them (there are many, many, more than this, and Charles Messier only catalogued the most visible ones):

Globular Clusters on Chart

Here is a zoomed raw image of M13 hot off the CCD chip (or rather cold off the CCD chip, as it's presently running at -20 degrees celsius):

Close up of (cloud covered) raw image of M13

Not too good? A few moments later, this:

Same close up, but less cloud

Same exposure, only about 5 minutes later.  Maybe the clouds are passing... This is more like what I would expect - much better definition of individual stars near the core of the cluster.

In case you're wondering about my guiding graph, yes, the drift continues:

Red line (declination axis) continues to drift

However, the clouds have improved, and definition in the images is improving...  So out comes the adjustable spanner, half a turn on the declination axis to flatten the red line.... and:

Whoops, wrong way (graph goes down even steeper (far right of red line)):

User error - excessive use of spanner in wrong direction...

To cut a long story short (and one which will be told in future) I messed up my guiding big time, just by turning that bolt half a turn.  Another 20 minutes later, the graph looks like like this:

What you guiding graph should not look like

By which time it is time the clouds have returned. I eat, do a few chores, get ready to pack up, and loh, there is a gap in the clouds. I try to guide again, but it's so late, the telescope has slewed over the meridian... Time to call it a night.