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.

My Telecope - Celestron C8 Schmidt-Cassegrain Telescope (SCT)

There are 3 main groups of optical telescopes - refractors (the oldest type, as used by Sir Isaac Newton), reflectors, and catadioptrics.  (For more detail see this excellent wikipedia page). The SCT is one of the latter types, and I chose this because of the size and aperture.  Basically, the greater the aperture (light gathering ability), the greater the number of objects that can be seen. I went for an 8 inch based on a simple price to performance equation:  this is how much I wanted to pay, and this is the performance I got.  For the same aperture, refractors are vastly more expensive.  The big downsides to getting a larger scope (apart from cost obviously) are portability, size, and attachments - the bigger your scope, the bigger the other attachments (eyepieces, filters, etc.) seem to need to be (at least to compliment the scope, or to not become the limiting factor in its use), and consequently the greater the cost. The 8 inch version was a happy medium for me - 6 inches seemed too small - I felt like I could have picked it up and run with it, and worried I would regret not getting something bigger, but the 9.25 and 12 inch versions induced mumblings of, "what a beast" "where will I hide that from the wife - I couldn't even get it in the garden shed".  So the 203mm C8 was a compromise of reasonable aperture, performance, portability, and cost.  It still feels like a good price to me, and is probably why Celestron have sold so many of these pieces of kit.  They are really popular, and I can see why.

Would I buy it again?  Maybe.  I'm still relatively new to this, and the only other scope I've really looked through is a cheap 80mm refractor (pictured above attached to my C8, which I'm using as a guide scope), so I haven't got much to compare, or got the best out of it yet, but so far it's been money well spent, and the optical tube is certainly fantastic; the detail I saw on the moon in the first week was gobsmacking.  Yes, I literally spent a week looking at the moon awestruck.

Seeing Saturn and rings with your own eyes for the first time is also a memorable experience. More distant, smaller or fainter objects ("faint fuzzies") take more skill, such as good polar alignment and averted vision, to get the best out of the scope, and you own eyes, but the C8 delivers in spades if you give it time to learn it's nuances.

The mount (CG-5) I have my doubts about - more on that later, but suffice it to say that for Goto functionality (slewing to objects in the database) it's great, but for long exposure astrophotography, you will be battling the mount, as much as all the other things that have to be just right.

I read a huge amount before shelling out my hard-earned on the scope, and one of the best sources of information I came across was this site by Ted Kurkowski.  Some of the content (for example on models, software and technology) is quite dated, but the guys knowledge and experience shines through. One of the great tips I picked up was to cut a disk with a hole over it and place it over the focuser, to enable finer control of focussing - always a tricky thing, especially with the standard focus knobs supplied on most scopes, and especially the C8. I cut a hole in an old plastic credit card sized rectangle (it was in fact a National Trust Membership card) and slotted it over the focussing knob.  Not only was fine control much better, but it also reduced vibrations induced by touching the scope.

The first few accessories I bought were a moon filter (good for viewing when the moon is near full) and a Neodyniun "light pollition" filter (don't bother).

Next was adapting an old webcam I had lying around to enable me to take stills and video of the moon.  Then USB cables to connect the mount to my laptop, so I could control it whilst sitting at my kitchen table, and not have to be out in the cold.  When it was minus 6 degrees every night, this became a neccessty...

After about 6 weeks of being a telescope owner, I went a bit mad and spent the same amount as I had on the scope and mount, on a focal reducer, guide scope, guide camera, and CCD camera.  Yes, I had really caught the bug, and my bank statements are the proof.  But if I wanted to take long exposure shots, I need a camera that could do this, and the focal reducer to increase the speed (and reduce the f number from f/10 to f/6.3, and reduce the focal length (from approximately 2000mm to  1400mm), thereby reducing the required exposure time by a factor of 3.  For long exposures I also needed a guide scope and camera to keep the telescope tracking my target objects.

Looks neat doesn't it?



Note the above picture includes the Celestron C8, with 80mm Skywatcher piggybacked on top as a guide scope (without eyepiece or camera attached).  The red cap on the end of the C8 covers the focal reducer and extender - it is here the CCD camera goes.  Just the other side of the focal reducer is the focusser (it was a standard focussing knob, but I replaced it with a feathertouch focuser and stepper motor).  The above picture also does not conain cameras or the plethora of cables requires to power and operate the mount, focussing and cameras.