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The Learning Curve
I have been CCD imaging for around three years and must admit to being completely addicted. The bar is raised ever higher by as techniques and cameras advance ensuring there is always a drive to stay up late, even on 'school nights' and take better images of more challenging objects. The sky really is the limit.
I've learned a great deal in the past years and still have far more to learn but I though it might be a good time to capture my learning curve in the hope that it would be of use to new comers to the hobby. The information available on the various YAHOO groups has been invaluable to me and I notice and ever increasing level of traffic and newcomers which has to be a good thing.
The key points I've picked up are as follows:
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Start with wide field to master image capture and manipulation without the hassle of accurate tacking
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Be patient and take long exposures concentrating on one object per night. Each subject should take 2 to 3 hours
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Match your equipment, if the mount's poor, work wide field
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A good mount is essential to success, spend the money there first
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Small aperture good optics are better than moderate or poor quality and larger aperture
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Long exposures will overcome light pollution and my experience is that a mono camera gives more flexibility in light polluted areas
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Try and resist the temptation to continuously upgrade. My experience to date is that it has always been me and not the gear that is missing the mark. Cameras and mounts are complex things and it takes time to learn the quirks and extract the best.
The images below show how my experiences with M81 changed over a three year period.
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MX7C Meade LX10 STAR 2000 180 Minutes |
APM Mak Newt MX716 L:R:G:B 120:20:20:20 STAR 200, Tak EM10 |
M81 APM Mak Newt MX716 120:20:20:20 Red blended 75% with 20 minutes of Ha, guided with ST4 |
First Steps: Frustration and Disappointment
Once I had mastered manual guiding of a film image with my LX10 I decided I'd learnt enough about the astrophotography to take the plunge and buy a CCD camera. The drive for me was to take photo quality images from my own back yard without having to spend hours away from the family. After reading a few books I went outside with my MX7C hooked it up to the LX10 and took a few 20s exposures of M51, M13 and M57. I spent the next day at work fretting about which edition of S&T to submit my images to and the next week trying in vain to turn the data into something that even resembled a DSO. I then realised that I needed longer exposures and after a week or two my first recognizable images started to appear.
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I was having a lot of difficulty manually guiding at f6.3 with the LX10 so I switched to a 135 mm camera lens to try and learn the image capture/processing basics. Working at f2.8 and with a wide field of view I started to capture better data and most importantly more of it. To overcome the limitations of my $20 lens I used an Ha filter for the luminance frames to sharpen the stars. The two images below were the first I'd taken which made me think I was getting somewhere (they look much better thumbnail than they actually are).
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So by the end of my second month or so I had started to understand colour processing (thanks to Bob Holzer's and Paul Lefevre's MX7C web pages) and realised that even for bright objects at least an hour of exposure would be required to get decent results. The next thing I noted was that as fun as the 125 mm lens was the optical quality was just not up to scratch. So I went back to the LX10 manually guided at f6.3 and produced my first real prime focus images. The exposures were still to short (5 minutes manually guided) 30 to 45 minutes per image but I felt progress was being made.
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Step 2: Autoguiding and Longer Exposures
When I first started out I was adamant that I would not just go out and buy an LX200 (the limit of my knowledge as far as telescopes went) and I was determined to prove that my LX10 could do the job. The guys at SX were very helpful and made me a special relay box which allowed STAR200 to work via the LX10. I was now able to autoguide and the world of longer exposures opened up. I also got hold of a Meade 0.33 reducer and combining that with the autoguiding and 1 hour plus of exposure per image I started to get more credible results. Still not good enough but definite progress.
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I took a lot of images and pushed my exposures beyond 3 hours of 600s sub exposures but I still could not get the results I wanted. I convinced myself that light pollution was the problem. The reality was I knew nothing about true colour balance and how important good focus and guiding was.
Step 3: Dark Skies and Mr Wodaski To The Rescue
In May and June 2002 I took trips to dark sky locations and combined with The New CCD Astronomer I suddenly found that I could take reasonable images. The key seemed to be a fast focal ratio and wide field of view. Combining these overcame the limitations of the LX10 mount and the signal requirements of the MX7C. I also borrowed a Nikon 300 mm f2.8 lens from a friend and piggy backed it on the LX10.
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I found Al Kelly's web site and was converted to his true colour philosophy. In particular the importance of maintaining star colour in images. Finally I adopted luminance layering in PS to make the best of my colour data. Within a few months I had reached what I believed was the limit of my equipment. The two images below are probably the best I've made with the single shot colour. The M27 is a 90 minute image 9 by 10 minutes with and LX10 at f6.3. The veil was a true labour of love 9 frames each of 45 (9by5) minutes all aligned in as a mosaic with the MX7C and a 300 mm lens.
Step 4: Sell The Family Silver
Although I loved the MX7C I was convinced that from my heavily light polluted garden I needed to switch to a mono camera to make best use of the available signal. I also realised that the LX10 mount with a PE of +/- 20 arc seconds was never going to do the job beyond 300 to 500 mm focal length. I contacted SX and they sold me a chip to convert the 7C to a 716 and I bought myself a Takahashi EM10 mount (portability was key to me). My first shots with the 716 were via the 300 mm Nikon lens piggy back on the LX10 and then with an APM 160 mm f5.5 MakNewt on the EM10 the improvement was almost instantaneous. Both of the images below are 90 minutes of luminance with 20 minutes each of RGB. The camera was in self guide mode so the effective exposures are half of these times.
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Step 4: Where We Are Now
For bright objects all seemed to be well but fainter stuff was still a big problem so I went for the last step of shifting from self guide to using a dedicated guide camera. I got hold an ST4 and started using the MX716 in progressive mode with the ST4. I began to see and instant improvement and found that 120 minutes of luminance coupled with 2x2 RGB at 20 minutes each would capture most objects even from my light polluted back yard. I also worked on using Ha frames to enhance the colour by blending 20 minutes of red 75% with 20 minutes of Ha for the red frames (see M81/82/51 in MX716 Page). I've also downloaded Spanish Chris' AA Flat field plug in and this has improved all my images no end. In heavy light pollution its very hard to use standard flats to take away all the gradients so the plug in is essential.
The last step has been to go for the SXV H9 and I have to admit I'm delighted with the camera.
Step 5: The Future
It's always difficult to resist the new gear impulses but right now I don't think there is much to be gained from any more purchases. I have a BORG 76ED 500 mm focal length ED refractor, a Borg 45ED 300 mm guide scope (wide field scope) and the APM. I've just bought a 1.6 barlow for the APM (~1500mm focal length) well over sampled for my location with the SXV) so we'll see where we go.
Step 6: Slight Change of Plans (Definitely Won't be Buying any more new gear for a while)
Well as you can see from the ST2000/SXV review I ran into some problems with my set up. I basically got tired of the frustration associated with an increasing complexity of kit, especially cables, associated with trying to eek the most out of my mount scope combination. At the end of the day the 160 mm MakNewt, guide scope, SXV and ST4 was just too much for the EM10. No surprises there but these things take a while to figure out when you are in the thick of it. So step one was to swap the guide scope, ST4 and SXV for the ST2000 which was easy enough. I'm delighted with the new camera as a complete system with the CFW8 its a dream . Then by chance I came across one of the last 2004 E160s and jumped at the chance to buy it. The combination of this scope and the ST2000 looked like the ideal light pollution busters to me. Then of course the EM10 could not handle the E160 so I finally took the plunge and went for an EM200 Temma II Jr. All in all the set up is fantastic. There is a step change between the EM200 and the EM10. The thing about the E160 is that its so fast you acquire so much signal that you can almost beat the light pollution, combining that with the ABG ST2000XM seems the ideal solution to me.
Step 7: Well not much more equipment
In fact the total amount of equipment has stayed the same but the names have changed. For lots of good reasons I've just moved home, continent and job so I took the opportunity to change my setup around. I've sold all my Borg equipment and the APM MAkNewt and invested the money in a C9.25 and a couple of good focusers. I've also taken a step back in my image processing and tried to start again having reviewed the various web resources available. I found Rob Gendler's site of enormous use especially the Ha RGB tutorial and also a couple of tips on Dean Jacobson's site especially the one for star softening. I'm pleased with the results so far and looking forward to a dark sky trip to test out the 9.25.
I've also bought a Brady Johnson adapter for Pentax which allows me to use the ST2K with my Sigma APO lens. This works well at up to 200 mm fl beyond that the lens produces some wired and wonderful star shapes, still its a lot cheaper than an STL110
Step 8: Arm Chair Astronomy combined with Hit the Road
After a long while trying to better my imaging techniques from home I've finally decided that the real key to success is a truly dark site as such I've been lucky enough to meet up with some fellow astronomers who regularly use a dark sky site in rural Ohio. The impact on my images has been enormous background counts drop from 40K to 4K which makes a massive difference to image processing. In the summer the nights are too short to head out to the site so worried about missing my Sagitarian favorites I thought I try out Arnie Rosner's rent a scope. Well I'm hooked I could not believe how easy it was to use and the images from New Mexico are truly amazing. I've also attended a course run by Adam Block on Making Every Pixel Count and which has helped enormously to focus and structure my image processing, still a ways to go but things still seem to be improving. My wife is almost at the stage where she will let me hang one of my pictures on the wall
