M56 Calibration Frames

Capturing calibration frames as planned.  Wow, did it get bright early!  At 3.50am the sky was blue in the east, which was too bright to continue imaging, so covered the scope and took dark frames.

Unfortunately I didn't buy the 250 quid Pink Floyd tickets I was offered....

Normal Guiding Service Resumed

A little less drift, but again, seeing conditions not ideal, so I am just happy to be imaging M13 again...

I've just noticed PHD was set to not guide on declination, so recalibrating with it set to north.

After getting enough data on M13, although it's late, M57 (the Rin Nebula in Lyra) came up into view, above the dirty grey zone of the horizon.  This is one of the joys of imaging where an image seemingly so bland as a grey smudge, will turn into a beautiful nebula once enough data is captured.  Yes, the grey smudge in the middle is what I am so excited about...

When I zoom in, this is what the camera is capturing, a planetary nebula 2,300 years from earth:

Once the image is processed, although it won't be nearly as good as the colour image below (from Stellarium), it's one of the personal rewards of astrophotography.

Below is one 120 second image converted to colour.  No other processing...

I wish I had more time to get more data, but as is often the case, M57 will have to wait for another day until I and my equipment can do it justice.

Apart from the odd blip, as below, (probably caused by "stiction" (static friction in the gears) - the CG-5 mount is reknowned for it), guiding has been good tonight, just a pity I have to close up shop...  The clouds are due to descend for a few days however, so at least I have plenty of data to process.

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.

First Astrophoto



M3 Globular Cluster - 20 x 60s exposures taken with a C8 SCT. Darks and bias frames, but no flats


It's took me 6 weeks from getting my telescope in late January 2011, and a few weeks later a new QHY8L camera, to produce a reasonable astrophotograph.

During this time, I did a lot of reading about polar alignment, light pollution, exposures, guiding, set up, and all the other skills required for astronomy and astrophotography. I learnt it all from practically zero knowledge beforehand, and it has been a difficult but very rewarding experience.

It was only on Monday 7th March that the skies were clear enough in London for me to take 20 or so images of this globular cluster (M3), which I then processed and stacked in MaximDL.

Even 3 months ago I never would of thought I'd be taking images of globular clusters in the freezing cold March weather. It's an addicitive pastime that has grown on me very quickly.

More about my telescope and setup in the next post, but briefly:
Celestron 8 inch telescope - C8 SCT XLT on CG-5 Mount
f/6.3 reducer / Astronomik CLS-CCD filter / QHY8L camera
20 x 60s stacked in Maxim, curves and levels in Photoshop
Guided on PHD (although possibly not required on such short exposures if my polar alignment was any good!)

The main lesson I have learned, apart from the huge amount of patience required, is that you have to choose your target carefully, and then set up everything for the evening with this in mind.  For the first few nights out I often took few images of very many different objects, and for astrophotography this is absolutely no good, as a lot of data (images) are required to get the desired end result.  Images are processed and stacked to reduce noise and increase signal.