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Astro-Imaging: Climbing the Learning Curve


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Astro-Imaging: Climbing the Learning Curve
Astro-Imaging: Climbing the Learning Curve .
by Paul Rix 02/12/2007

The purpose of this article is to illustrate the climb up the learning curve that everyone has to face when they start out in this immensely satisfying, challenging, enjoyable and yet, often rather frustrating pursuit. I have been imaging now for two years and would rate myself as being at the intermediate level, using average equipment under rather light polluted skies. Over the course of this two part article I will look back at how my images and technique have progressed from the first over exposed shots up to where I am at now (still learning but at the point where I am not embarrassed to put my best work in a frame and hung on the wall).

The First Year.

First Steps

I feel extremely fortunate in that Erika and I started out in Amateur Astronomy together. It has been a wonderful shared interest that has turned into a passion for both of us even though our specific areas of interest are different. Through Astronomy we have come to know a lot of very interesting, helpful people and made some great friends.

It started for us in 2004. We had casually talked about getting a telescope to try our hand at Astronomy as it was a subject that interested us both. In November 2004 Meade sold off some factory refurbished ETX70AT refractors for the bargain price of $130. It seemed like a deal not to be missed, and so we bought one as a Christmas present to ourselves. It was at this time that we joined the Cloudy Night's forums (and what a great decision that was).

We spent a lot of time looking at the Moon, Saturn and Jupiter (which required getting up very early) . It was an exciting time. I wanted to see more detail though. One of my early goals was to see Jupiter's Great Red Spot, but even with a 3X Barlow Lens I couldn't make it out (although I could easily see the cloud belts).

The Mighty 'Webcam'

Having seen what could be done with webcam imagers by CN members and in the mainstream astronomy magazines, I decided to give it a try myself. Celestron had just released their $100 NexImage Solar System imager onto the market. It seemed to be the perfect way to start out as it required no modification and came with all the required software. The NexImage uses the same CCD sensor as the popular ToUcam Pro webcam that many were having great success with. Of course, when the NexImage was delivered the clouds rolled in for several days which was rather frustrating. It did give me some time to learn some basic techniques and get a feel for the operation of the camera. I took some test video AVI's to practice with and became familiar with the Registax software and how to use it for stacking individual frames. My first image taken with the ETX70 and the NexImage was of a car parked about 3ž4 of a mile away.



I almost fell off my chair when I saw the difference between the raw frames and the final stacked version. This was exciting stuff and it is fair to say I was hooked even before I took my first Astro-Image.


On the 2nd of January 2005, our dogs woke me up at something like 6am wanting to be let out. I stepped outside and the sky was crystal clear. The Moon was up to the South West, and there, to the South was Jupiter shining brightly. Once the Dogs were back inside I hurried out with the telescope, Laptop PC and NexImage camera for my first Astro-Imaging session. I shot AVI's of both the Moon and Jupiter. Within half an hour I was back inside working on the video files. They were over exposed but I was proverbially 'Over the Moon'. The resulting images showed Lunar craters and Jupiter with it's four Galilean Moons:




As with many things, initial progress can be made quickly. By the middle of January I started to get a handle on the exposure settings which allowed me to image the Rings of Saturn, and the equatorial cloud belts on Jupiter.


Saturn 10th January 2005 Jupiter 15th January 2005

Saturn January 28th 2005


I was really encouraged by the results. Each new image seemed to take me a step forward. By March I was getting quite ambitious. I discovered that it was quite possible to stack Barlow lenses (ie use more than one at the same time). We had 2X and 3X Barlows by this time. Focusing was quite a challenge at this magnification. I found that the best method was to increase the frame rate of the NexImage to about 20 frames per second which smoothed out the live preview a lot. Once in focus I went back to 10 frames per second to record the AVI file.

In early March I was able to image Saturn and capture the Cassini Division in the rings.




I finally achieved my goal of capturing the Great Red Spot on March 18th 2005 using the stacked barlows.


It was certainly not the prettiest image, but the GRS was clearly visible! I was ecstatic.


Aperture Fever Strikes

By this time both Erika and I had developed a strong case of 'Aperture Fever'. We started looking around for a larger telescope and I bought a used Meade Deep Sky Imager so that I could try my hand at DSO's. Within a week or two of the DSI arriving, we found a great deal on a used Meade 10in LX200 'Classic'. I drove to North East of Cleveland in a bad snowstorm to pick it up (quite an adventure, but that is another story).




The LX200 and ETX70AT (and one very happy novice imager).
The LX200 was a huge upgrade for us. It allowed Erika to advance with her visual observing and sketching while opening up a whole new area of imaging for me. The improvement was immediately apparent when I took images of Jupiter and Saturn through the new telescope:





Imaging planets with the LX200 was not all that different from using the ETX70. The operation of the telescope was similar (they are both Meade products after all), so all that I had learned up to this point was directly transferable.

Looking Deeper

The extra aperture provided by the new telescope meant that Deep Space Objects would be within my grasp using the DSI camera. I learned very quickly that DSO Imaging was an entirely different ball game. I had to learn about dark frames, field rotation (I was using the LX200 in Alt/Az mode), histogram stretching, colour saturation and balance. It was mind boggling to say the least. Even so, the idea of taking a picture of a distant Galaxy or Nebula from my light polluted back yard seemed like an interesting and exciting challenge.


The first Galaxy I attempted was M64 (the Black Eye Galaxy). It was the first time I had tried to image an object that didn't show up on my preview screen so I had to trust the Telescope's GoTo ability.




As you can see, the alignment was good enough to get the target on the sensor chip but not centered.

I was using 15 second exposures as a starting point. It was amazing to see the shape of the Galaxy start to show as the individual exposures were automatically stacked in real time. Looking at the image now I almost cringe, but at the time I was extremely pleased with it.

I found that imaging DSO's was far more time consuming than using the NexImage for planets. Even so, at this point I was knocking out images of several targets each time I went out.

The following were taken in April and May of 2005.




M88 which for some reason showed more detail in the blue channel, so I set the colour balance to lean that way. At the time I was more interested in seeing the spiral arms than what the picture looked like aesthetically.

M104. Rather soft in focus but I was pleased to capture the dustlane.

 NeatImage.com


M51 which was too large to fit completely in the frame.

You can see that there was significant field rotation and tracking error showing up. It took me a while to learn that Meade's AutoStar Image Processing software (supplied with the DSI) could align the individual frames using two stars as reference points. This dealt with field rotation quite effectively as long as the exposure times are short enough that the rotation did not show in the individual frames. Tracking errors were another matter though. I found the longest exposure length I could use was 30 seconds and even then, I would end up discarding about half of my frames before stacking the good ones. Mostly I stuck with 15 seconds which was much more consistent.

The International Space Station

In early May I diverted my efforts to another interesting challenge. I had seen a number of images taken by amateurs of the International Space Station (most notably Wes Higgins stunning images and also one featured in the Meade Catalog). I wondered if I could do something like that with the equipment I had at my disposal. I asked the question in the Cloudy Night's Solar System imaging forum and the replies were encouraging. There were a couple of favorable ISS passes predicted within a few days so I gave it a try. My NexImage was the best camera for the task. I used Jupiter as a focusing and exposure aid (because it has detail and similar brightness to the ISS). After achieving focus and my best guess at a suitable exposure setting, I powered off the LX200 and loosened the locks. The ISS appeared on schedule
(www.heavens-above.com is a great resource) . I tracked it manually, letting the ISS pass through the center of the inner ring on the Telrad Reflex Finder before repositioning my aim to let the Station fly through the Telrad again, and again, until it disappeared from sight. The first attempt was a success although a little over exposed. My second try turned out better, showing the gold coloured solar array and main structure of the Station.


First Attempt Second Attempt


I have tried a number of times since then and until very recently I ended up with very disappointing results. I think beginner's luck must have played a part.

The Eagle and Dumbell

Over the next couple of months I imaged several of the well known Deep Space Objects on my 'hit list'. I was particularly interested in capturing an image of the giant gas and dust columns in M16. The image I took at the time was pretty rough around the edges, but it did show the famous 'Pillars of Creation'. Planetary Nebulae are also fascinating and dramatic objects. M27 gave great results even with short exposures. I was surprised at it's size and brightness.


M16 M27


Even though I obviously I still had a lot to learn, I was managing to capture images that were at least recognizable.

The Red Planet.
The showpiece for Amateur Astronomers in 2005 has to be the Mars Opposition. I spent most of my imaging sessions during the last half of the year concentrating on the Red Planet. The more I read about Mars, the more excited I was about imaging it. To start with I thought I would be satisfied if I could capture the Southern Polar Ice Cap which proved to be easier than I thought. I got my first Mars Image at the Sky Tour 2005 star party held at Bellevue, Ohio on the 5th of June.



My first image of Mars showing the Southern Polar Ice Cap.

Seeing as I had managed to get the Ice Cap, the next challenge I set myself was to take an image where the giant volcano Olympus Mons could be identified. That was tougher and would have to wait until Mars was much closer. Each time I went out over the next few months, Mars was getting closer and larger.



By September Mars was close enough for me to achieve my goal of capturing Olympus Mons. Far from Damien Peach quality, but the volcano was there if you look closely.




On October 2nd I captured my best Mars image of the season by stacking the 2X and 3X barlows. It must have been a night of very good seeing.















Back into Deep Space

With Mars rapidly becoming more distant, it was time to focus once again on deep space imaging.

One of the Deep Space Objects that I wanted to capture was the Horsehead Nebula. It is a fascinating dark nebula in a stunning region of the night sky. I didn't think it would be an easy target though, and I was right. I was just hoping to get something recognizable to show for my efforts. It was just as well that I did not have high expectations as my first image was not up to much. Still, the basic shape was there, so it was a good start.

My first image of Horsehead Nebula



This pretty much brought to an end my first year of imaging. I still had a lot to learn but real progress had been made in a number of areas. My planetary images were of higher quality than their deep space counterparts, but that is to be expected. My setup was more suited to long focal length, short exposure imaging which is great for the bright planets. Deep space imaging required much better tracking than I was able to achieve consistently in Alt/Az mode (if I wanted to use anything greater than 15 seconds of exposure). One thing was for sure though, I was 12 months in and completely hooked.

The Second Year
Up to this point all my images were taken in Alt/Azimuth 'mode', but it was becoming increasingly clear to me that I would need to get the telescope polar aligned if I wanted to extend exposure times and achieve better tracking (as I had been told many times on CN). In January 2006 I was browsing Meade's 'Factory Outlet' web page. They were selling off a version of their Standard Wedge that used to be shipped with an earlier


model 10inch SCT. I had been unable to justify spending several hundred dollars for a 'Super Wedge' at that time, but here was one that would at least get me started for under $100. The internet is a wonderful thing but it does make spending seem all too easy. About a week later I had the new wedge installed on the LX200 tripod. I was so excited I even set it up in the basement to see what it looked like all assembled.


I was a little concerned about attaching the heavy scope on the wedge when alone (I was worried about the scope being held in place by just one bolt during the time it took me to get the other two bolts in place), so I made sure Erika was there to help in case I got into trouble. It proved to no real problem though and now I am perfectly happy setting it up unassisted.

Polar & Drift Alignment
I now had a whole new skill to learn ? Polar Alignment. It was a little intimidating at first as there were several new concepts to get my head around. Right Ascension, Declination, Meridian, Reticle Eyepieces, Drift Alignment! I did a lot of reading before heading out for the first time. Getting the telescope polar aligned well enough for visual observing was not all that hard. Accurate Drift Alignment for imaging purposes proved to be rather frustrating though. It took me a long time each session to get the alignment right. A lot of experienced imagers can get a good drift alignment completed within 20 minutes to half an hour. It was taking me an hour and a half to two hours, by which time I was cold and frustrated (it was January after all).

I am one of those people who believes that technology can solve most problems like this. I started looking for a better solution. I found it in a program called WCS which was very reasonably priced. I use it every time I go out now. The program allows me to be accurately aligned in about 15 minutes, sometimes less. It uses a webcam to track a star and analyzes the drift over a given period of time. When you click on the 'Correction' button you are given all the information you need to quickly adjust the mount. It takes all the guesswork away. If you are interested in finding out more about this program you can run a search on the Cloudy Nights imaging forums or head over to http://wcs.ruthner.at/index-en.htm . There are several other programs out there that can help with drift alignment such as K3CCDTools, but I have stuck with WCS mainly because I am now familiar with it.






Once I was able to get a good drift alignment I immediately saw better results. I was able to take 30 second exposures with acceptable tracking. This really helped to add detail to my images. I should also point out that I was now using an F3.3 focal reducer, which made a big difference too. I revisited the Horsehead Nebula and also tried for M1 The Crab Nebula for the first time.



I think you will agree that this version of the Horsehead Nebula was a significant step forward from the previous attempt taken in Alt/Azimuth mode. The Crab Nebula image was very encouraging too, but required some work in Photoshop to remove some star trailing.

I decided that to push the exposure time out further I would need to work on guiding. I have seen some amazing images on Cloudy Nights that were manually guided by the photographer while looking through a reticule eyepiece. That takes a lot of patience and skill. Once again, I turned to technology as an answer in the form of Auto-guiding. At about this time I bought Erika a Coronado PST for her birthday and we needed a mount for it. Meade were selling off some cheap 70mm refractors that came with Alt/Az mounts. We bought one so that Erika could attach the PST to the mount and I had the 70mm scope for guiding. Initially I used the Neximage as the guide camera but it was rather hit or miss finding a suitable star to guide on. It was rather frustrating at times as I had thought this would be an easy step forward (compared to moving up to the wedge). Even so, I did manage to get an image of M51 that was, up to that point, my best image of a galaxy. I was very pleased with this one.




I also added a new galaxy to my tally in the form of NCG2903




This proved to be the last image I took using the Meade DSI camera.

Another step forward.
In early March 2006 I took the plunge and bought a used Meade DSI Pro monochrome CCD camera. I chose the DSI Pro for two main reasons. Firstly the cost. It was expensive for me at the time but I found a good deal on a lightly used one. For the price I don't think there was a better camera out there. The second reason being that I was already familiar with the basic operation of the DSI camera. The new challenge would mainly be with image processing after the 'data' after the imaging session at the scope.

To test the new camera I decided to shoot NGC2903 once again to see what kind of improvement I would have over the older Colour DSI. The weather was not fully co-operating that night and so I was only able to get the Luminance set of data (imaged through an IR-cut filter).


I was pleased to see that the image seemed much sharper than the Colour DSI version. A few nights later I was able to go back and get the red, green and blue data needed for the final colour image. That was a new concept for me too. The thought of taking the colour elements of an image on different nights seemed pretty strange at first, but I now find it is something I have to do quite often if, for example, the clouds roll in or the object is only in a favorable position to image for a short time.


The image that really showed me that I was moving in the right direction with the new camera, polar alignment and autoguiding (now using the old DSI as the

guide camera) was of M16 . It was taken on April 27th 2006.


I think that the first four months of 2006 was the period where my images improved the most rapidly. I can't put my finger on one particular change that made the biggest difference, mainly because I changed both the method of mounting the telescope and the change from using a one shot colour camera to using filters and a monochrome CCD. I can say though that moving up to a polar aligned mount, and learning how to get it accurately set up, was the biggest challenge. It was all worth the effort though.

During the next few months I gained experience using the new camera and also image processing. I revisited M51 and M27 using the new techniques I had learned.






Red Junior and Discovery
I also took a few images of Jupiter towards the end of May. I wanted to capture 'Red Junior' which was discovered by Chris Go (who is a well known CN member). The NexImage was still hanging in there and I managed to take this shot with it.




In July there was a lot of excitement due to the 'Return to Flight' Space Shuttle mission. I was eager to get an image of the Shuttle to compliment my ISS image taken in May 2005. I was lucky to have a good pass a day or two before Discovery was due to land. Unfortunately the NexImage was on it's last legs and performed badly with lots of 'bleeding' around bright objects. The image below is the best I managed. I was rather disappointed with this shot as I think it would have come out quite well if the camera had behaved. Of course, only a bad workman blames his tools, but in this case it was a legitimate problem.




The camera problem was not all bad though, because it prompted me to find a replacement. I settled with the Philips SPC900NC webcam which has proved to be very capable.

New Toys

In September 2006 I added some significant upgrades to my imaging arsenal. These came in the form of a DSI Pro II camera and an Orion ED80 refractor.




The DSI Pro II is now my main imaging camera while the DSI Pro has been relegated to guide camera duty. The new camera has a bigger CCD sensor with a greater pixel count. It has greater sensitivity while providing a cleaner image than it's predecessor. Another neat feature is that the CCD has a temperature sensor attached which allows the Meade Envisage software to automatically select a matched Dark frame. This negates the need to take dark frames each imaging session ( long as you have a suitable dark frame already in your 'darks library'). That saves a lot of time and results in very clean 'subs'.

The ED80 was picked up second hand in immaculate condition as a birthday present from Erika. I wanted this telescope because it would open up a whole new set of targets to me that the SCT was not suited for. These included M31 The Andromeda Galaxy and the Veil Network Nebula. With the use of a 0.5X focal reducer the ED80 lets me image a fairly wide area. The refractor gives me pin sharp images too. The shorter focal length also has the added benefit of being much more tolerant of guiding and tracking errors. I use the ED80 'piggybacked' on top of the LX200 but I have a set of rings that allow it to be attached to our LXD75 mount when Erika wants to use it for visual observing (it is a very nice telescope for visual work too). I have been extremely pleased with both the new DSI Pro II and the ED80.

Below are some of the images I have taken so far with the ED80 and DSI Pro II.


The Horsehead and Flame Nebulae. The very bright star is Alnitak (the left star in Orion's Belt). As you can see, Alnitak has produced a large halo effect. I am hoping that as I progress further I can learn how to eliminate that. One of the most enjoyable things about this hobby is that there is always something else to learn about.
The Eastern Veil Nebula (NGC-6992).





M33 The Triangulum Galaxy.

Discovery and the ISS
The last image I took in 2006 was of the ISS and the Space Shuttle Discovery (STS-116) as it passed high overhead on the 19th of December. It was a very lucky shot as a lot of things came together that were not under my control. The video file contained about 3900 frames. The ISS and Discovery were on quite a few of those, but for the most part they were blurred and unrecognizable. Just a few came out well, and of those the image below was definitely the best. At the time I took this, ISS and Discovery were approximately 220 miles above my head traveling at roughly 17000 miles per hour. As I said, it was a lucky shot but it more than made up for the poor results I had back in July.




Looking Ahead.

That brings us up to where I stand presently. Looking to the future, there are a number of things I would like to add to my equipment list that would help advance my climb further up the learning curve. Number one on that list has to be a 'roll off roof' observatory. This would allow me to spend more time imaging rather than setting up and tearing down. Hopefully in the next year that will come to be a reality. As for goals, I would like to get a handle on imaging the Sun in Ha. I have tried to do this a few times now but found it to be frustratingly difficult and my results were rather poor. I know it can be done though, as the stunning images in the CN forums prove time and again.

Conclusion.
I hope that this overview of my imaging experience so far has illustrated that, although the learning curve may seem impossibly steep at the beginning, good progress can be made over a fairly short space of time if you keep at it and take things one step at a time. For me it has been a very enjoyable and rewarding journey so far. The great thing is that I still have so much to learn and there are many unique and awe inspiring objects left up there that I have yet to image (a lifetime's worth I am sure)..

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