This is a very abbreviated version of Scott Rosens LLRGB workflow found on his website, AstronomersDoItInTheDark.com. Its the workflow I'm currently using for almost all of my image processing.
Tuesday, December 10, 2013
Sunday, December 8, 2013
Alnitak Strikes Again
Many astrophotographers have had a tough time imaging the Horsehead and Flame nebulae around the bright star Alnitak. It is famous for causing reflections and usually reeks havoc on imaging systems. My recent attempt proves I am not immune to this phenomenon.
I actually got hit with a double whammy because I recently installed a dew heater on the secondary mirror of my RC and accidentally left a wire sticking out behind the mirror. This caused some odd artifacts that are mostly noticeable on the brighter stars.
As for Alnitak, it caused some reflections in the upper left and right parts of my image. It appears that the upper left is reflections from my tube baffles. Above and right of the Horsehead is a reflection that is most likely from my Astro Physics CCDT67 Telecompressor. You can clearly see them in this greyscale image.
With a rather large crop of the image I was at least able to salvage something from it.
I hope to be able to revisit this target soon and will move Alnitak outside of the field of view when using the RC. I could probably use my wide field apo and not have this problem but I'd like to get the added detail that isn't possible with the short focal length scope.
I think the problems caused from the dew heater have been fixed so hopefully I'll get some clear nights to do some more testing soon.
I actually got hit with a double whammy because I recently installed a dew heater on the secondary mirror of my RC and accidentally left a wire sticking out behind the mirror. This caused some odd artifacts that are mostly noticeable on the brighter stars.
As for Alnitak, it caused some reflections in the upper left and right parts of my image. It appears that the upper left is reflections from my tube baffles. Above and right of the Horsehead is a reflection that is most likely from my Astro Physics CCDT67 Telecompressor. You can clearly see them in this greyscale image.
With a rather large crop of the image I was at least able to salvage something from it.
I hope to be able to revisit this target soon and will move Alnitak outside of the field of view when using the RC. I could probably use my wide field apo and not have this problem but I'd like to get the added detail that isn't possible with the short focal length scope.
I think the problems caused from the dew heater have been fixed so hopefully I'll get some clear nights to do some more testing soon.
Monday, November 4, 2013
A review of the Levenhuk 80mm triplet
I already owned a very good scope for widefield imaging but was looking for something that would be a little more versatile. While I want this to be a review of the Levenhuk 80mm triplet and not a comparison with the Astro Tech AT65EDQ, I need to relate my thinking as to why I thought I needed the new scope.
The Astro Tech scope is a 65mm quadruplet with a built-in field flattener. It provided extremely flat fields all the way to each corner of my images every time I used it. However, there were times I wished it were a faster scope. There were times I wished I had a little wider field of view. And there were times that I wished I could use my 2" diagonal and 2" eyepieces to take in some widefield views. The AT65EDQ would not reach focus with my 2" diagonal in the focuser, and the built-in field flattener prohibited using a reducer/flattener, so I was stuck with its f/6.5 optics that provided a focal length of 420mm. However, it is marketed as an astrograph, and for the last year, it has served me extremely well as just such an instrument.
Enter the Levenhuk 80mm triplet.....
Upon receiving the scope, the first thing that caught my eye was the paint job. In good lighting this thing is beautiful. It looks to be a pearl white with some metal flakes. I tried to get a close up of the paint but could not get a shot that I felt does it justice.
The next thing I noticed that I really liked was the threaded metal dust cap. This cap will never fall off and you can take darks in broad daylight and never need to remove the camera from the scope.
The 2" crayford focuser seems to be relatively smooth, but since buying a Moonlite for my newtonian, I can only say that it is adequate. There is a lock for rotating the focuser which is nice for framing a target if you have not already taken flat frames. However, it does not have a screw to lock focus, only a tension screw.
Besides not having a lock screw on the focuser, there were only a couple of things I did not like about the scope. First, it does not come with a mounting bracket for a finder scope. It also does not come with mounting rings. It comes with only the L-bracket that is bolted to the Losmandy style D-plate in the photo. I have since purchased a set of 90mm ID William Optics rings and made a plate to go on top of the rings to mount the finder scope bracket to hold my 50mm Orion mini guidescope. The configuration seems to be very solid.
We all know that getting new astronomy equipment also brings with it lots of clouds, sometimes for days on end. I did manage first light a few days later for a bit of observing with the new telescope. I used my Meade 2" diagonal with the Explore Scientific 24mm 82 degree apparent fov eyepiece for some outstanding widefield views. This provided a field of view of more than 4 degrees with a magnification factor of 20X. The views were extremely crisp and I decided to up the magnification and check collimation with a star test. For this, I installed my Astro Tech 2X barlow in the diagonal coupled with my Explore Scientific ES82 8.8mm eyepiece and slewed to Vega. The diffraction rings showed a perfectly concentric pattern, and when bringing the bright star into focus, I could not see even a hint of chromatic aberration. The premium FPL-53 optics perform flawlessly.
The brief first night of viewing the stars between breaks in the clouds satisfied me for a little while, but I was anxious to see what it would do with my Canon DSLR installed in the focuser. It would be a few nights before the Moon would allow me to do any imaging, so I called Astronomics and ordered their Astro Tech 0.8X reducer/field flattener. This reduced the focal ratio of the scope from f/6 down to f/4.8 and dropped the focal length almost 100mm from 480mm down to 384mm. The Moon allowed only a very short first night of imaging, but this is what I was able to produce in one hour using five minute subs (12X300sec) at ISO 800.
I want to add some more data to the M33 before posting a full resolution image to Astrobin. Fortunately, I was able to get in some serious imaging a few nights later. This image of Andromeda galaxy is a combination of 53 subs of 300 seconds (4.4 hrs) at ISO 800.
The Pleiades (M45) was done over 2 nights and is a total of 100 subs of 300sec (8.3 hrs) at ISO 800.
The Astro Tech scope is a 65mm quadruplet with a built-in field flattener. It provided extremely flat fields all the way to each corner of my images every time I used it. However, there were times I wished it were a faster scope. There were times I wished I had a little wider field of view. And there were times that I wished I could use my 2" diagonal and 2" eyepieces to take in some widefield views. The AT65EDQ would not reach focus with my 2" diagonal in the focuser, and the built-in field flattener prohibited using a reducer/flattener, so I was stuck with its f/6.5 optics that provided a focal length of 420mm. However, it is marketed as an astrograph, and for the last year, it has served me extremely well as just such an instrument.
Enter the Levenhuk 80mm triplet.....
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| This is the scopes L-shaped mounting bracket bolted to my supplied Losmandy style dovetail. |
Upon receiving the scope, the first thing that caught my eye was the paint job. In good lighting this thing is beautiful. It looks to be a pearl white with some metal flakes. I tried to get a close up of the paint but could not get a shot that I felt does it justice.
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| Comes in a nice little case. The dew shield is extra long compared to other refractors I have used. |
The next thing I noticed that I really liked was the threaded metal dust cap. This cap will never fall off and you can take darks in broad daylight and never need to remove the camera from the scope.
The 2" crayford focuser seems to be relatively smooth, but since buying a Moonlite for my newtonian, I can only say that it is adequate. There is a lock for rotating the focuser which is nice for framing a target if you have not already taken flat frames. However, it does not have a screw to lock focus, only a tension screw.
Besides not having a lock screw on the focuser, there were only a couple of things I did not like about the scope. First, it does not come with a mounting bracket for a finder scope. It also does not come with mounting rings. It comes with only the L-bracket that is bolted to the Losmandy style D-plate in the photo. I have since purchased a set of 90mm ID William Optics rings and made a plate to go on top of the rings to mount the finder scope bracket to hold my 50mm Orion mini guidescope. The configuration seems to be very solid.
We all know that getting new astronomy equipment also brings with it lots of clouds, sometimes for days on end. I did manage first light a few days later for a bit of observing with the new telescope. I used my Meade 2" diagonal with the Explore Scientific 24mm 82 degree apparent fov eyepiece for some outstanding widefield views. This provided a field of view of more than 4 degrees with a magnification factor of 20X. The views were extremely crisp and I decided to up the magnification and check collimation with a star test. For this, I installed my Astro Tech 2X barlow in the diagonal coupled with my Explore Scientific ES82 8.8mm eyepiece and slewed to Vega. The diffraction rings showed a perfectly concentric pattern, and when bringing the bright star into focus, I could not see even a hint of chromatic aberration. The premium FPL-53 optics perform flawlessly.
The brief first night of viewing the stars between breaks in the clouds satisfied me for a little while, but I was anxious to see what it would do with my Canon DSLR installed in the focuser. It would be a few nights before the Moon would allow me to do any imaging, so I called Astronomics and ordered their Astro Tech 0.8X reducer/field flattener. This reduced the focal ratio of the scope from f/6 down to f/4.8 and dropped the focal length almost 100mm from 480mm down to 384mm. The Moon allowed only a very short first night of imaging, but this is what I was able to produce in one hour using five minute subs (12X300sec) at ISO 800.
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| M33, Triangulum galaxy |
I want to add some more data to the M33 before posting a full resolution image to Astrobin. Fortunately, I was able to get in some serious imaging a few nights later. This image of Andromeda galaxy is a combination of 53 subs of 300 seconds (4.4 hrs) at ISO 800.
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| M31, Andromeda galaxy. I was quite pleased with how this one turned out. |
The Pleiades (M45) was done over 2 nights and is a total of 100 subs of 300sec (8.3 hrs) at ISO 800.
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| This image of M45 is my personal record for integration time. I really wanted to pick up the faint dust in this area. |
Then I decided to try the Heart nebula, IC 1805. This target is best shot in h-alpha, but I thought I would
give it a try in RGB with my DSLR. It is 48 subs of 300 seconds (4 hrs) at ISO 800. I probably should have gone with longer subs, but left it at 300 seconds, because I have a good library of dark frames at 300 seconds. Someday I hope to own a nice CCD camera and some narrowband filters. I think it will help greatly on targets such as this one.
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| IC 1805, the Heart nebula |
Full resolution images can be found here in my Astrobin gallery: http://www.astrobin.com/users/rflinn68/ The corner stars look very good on the M45 image, but not so good on the Heart. The camera was never removed, so I suspect this is due to my focusing technique. I probably will need to start focusing on a star somewhere between the center and one of the corners. Everything considered, I am very happy with the new scope.
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| Here is the scope set up for imaging with the William Optics rings and dew heaters. I made a plate to go on top of the rings for mounting the finder bracket to hold the Orion 50mm mini guidescope. |
I ended up selling my AT65EDQ and keeping the Levenhuk 80mm triplet. It is simply a much more versatile telescope and better fits my needs. For starters, it has 15mm more aperture, which is always good. It is a faster scope at its native f/6 and much faster with the reducer at f/4.8 and will give me a couple of focal lengths (384mm and 480mm) to choose from once I purchase a regular field flattener. It is also an excellent grab and go telescope for observing that I can use with my 2" accessories and eyepieces.
The key word I keep coming back to in regard to this scope is "versatile." I am very pleased with the scope and expect to enjoy it for years to come for both observing and imaging. Great job, Levenhuk, and thank you for such a wonderful instrument!
Saturday, November 2, 2013
The Seven Sisters
I was able to get in another test image with the Levenhuk 80mm triplet. I'm really starting to like this scope and Astro Tech focal reducer/field flattener combo. Not missing the AT65EDQ quite so much now. This image of M45, also known as The Pleiades and The Seven Sisters, was shot over two nights. I was able to stack 100 five minutes subs with this one for a total integration time of 8.3 hours. This is the most data I have put into an image to date. I was really hoping to get the faint dust surrounding the cluster to show up so I spent a good amount of time on it.
The Seven Sisters and the Andromeda galaxy were the first two images Cara and I stacked almost a year ago now. A lot has been learned in the last year and its nice to look back and see improvement made in our imaging and processing techniques.
The Seven Sisters and the Andromeda galaxy were the first two images Cara and I stacked almost a year ago now. A lot has been learned in the last year and its nice to look back and see improvement made in our imaging and processing techniques.
Sunday, October 27, 2013
Andromeda Galaxy
Here's one of the first test images with the Levenhuk 80mm triplet. It is 53 X 300 second (4.4 hrs) subs at ISO 800 with the Canon T3. Using the Astro Tech 0.8X reducer/field flattener the field of view is 3.2 degrees wide X 2.13 degrees high with the image cropped to 98% of the original.
Full resolution image can be viewed here: http://www.astrobin.com/full/61650/?mod=none
At an apparent magnitude of 3.4, the Andromeda galaxy (M31) is one of the brighter Messier objects, making it visible to the naked eye on moonless nights even when viewed from areas with moderate light pollution. In this photograph M31 appears more than 6 times as wide as the full moon. Only the brighter central region is visible to the naked eye or when viewed with binoculars or small telescopes.
Full resolution image can be viewed here: http://www.astrobin.com/full/61650/?mod=none
At an apparent magnitude of 3.4, the Andromeda galaxy (M31) is one of the brighter Messier objects, making it visible to the naked eye on moonless nights even when viewed from areas with moderate light pollution. In this photograph M31 appears more than 6 times as wide as the full moon. Only the brighter central region is visible to the naked eye or when viewed with binoculars or small telescopes.
Thursday, October 24, 2013
Levenhuk 8" carbon fiber RC astrograph
The weather here in Arkansas isn't always cooperative with my astrophotography hobby. Even when it's clear the Summer months have not been conducive for imaging, especially for my un-cooled DSLR. However, I have owned this scope a couple months now and have had several opportunities to try it out. I would like to share my opinion of it here.
First of all, the carbon fiber tube simply looks outstanding. Aside from its good looks, the carbon fiber tube also serves a very important function. I can image with it over multiple nights and not have to adjust focus. This is something I simply cannot do with my steel tube newtonian and refractor astrographs. The focuser itself is very smooth and seems to be more than adequate using my Canon 1100D. I dont know how it would do with the added weight of a CCD camera, filter wheel, etc., but it has done its job so far. I am now perhaps spoiled after installing a Moonlite on my newtonian and will probably upgrade the focuser sometime but its not something that is needed at the moment.
The second thing I would like to mention is that I am very happy with how the stars appear in my images. Most of you that have imaged with newtonians and refractors know that a coma corrector or field flattener is needed. The stars in the corners of my images look very good. They are not perfect but I would say they are better than what my f/4 newt with Baader Mark III MPCC combo produces. This is also with a full size DSLR sensor. If you are using a camera with a smaller sensor then you probably will not see anything wrong with your images. Also worth noting is that the scope was slightly out of collimation when I received it. I have only adjusted the secondary screws to get a nice looking diffraction pattern on an out of focus star. Further tweeking with the primary adjustment screws could make my corner stars look even better.
Imaging at f/8 with a DSLR was pretty tough for me after being use to the fast optics in my f/4 newtonian. For this I purchased the Astro Physics CCDT67 Telecompressor. The reducer screwed into a 23mm long Baader 2"/T2 nosepiece has dropped the focal ratio from f/8 down to f/5.68 and has proven to be a very good combo. I also own the AT8IN and AT65EDQ astrograph offerings from Astro Tech. I like both of these scopes a lot but the Levenhuk Ra 200RC is an excellent telescope and is my weapon of choice for long focal length astrophotography. I also own an 8" and 10" Schmidt Cassegrain scope and this RC is many times over the better imaging scope. I would recommend this telescope to anyone looking for a long focal length astrograph.
I have managed a few test images using my Baader UV/IR modified (by Gary Honis) Canon camera. The image of the Wizard nebula is the only one I have spent a good amount of time on (4.5 hrs). The Elephants Trunk is just 21 subs and the Swan is just 14. All subs were five minutes and ISO 1600 was used. The Swan was shot at f/8 and the other two were done using the Telecompressor. The full resolution images and any future improvements to them may been found here: http://www.astrobin.com/users/rflinn68/
There will be more work from this scope in the future so be sure to check back with Little Piney Observatory for updates. I have received a new scope from Levenhuk. They have sent me a nice 80mm triplet for a test and review. After a few nights of using this scope I decided that I would be keeping it and have sold my AT65EDQ. The Astro Tech was a very fine scope but the Levenhuk 80mm will be a more versatile telescope to have in my arsenal. Test results and a thorough review coming soon!
First of all, the carbon fiber tube simply looks outstanding. Aside from its good looks, the carbon fiber tube also serves a very important function. I can image with it over multiple nights and not have to adjust focus. This is something I simply cannot do with my steel tube newtonian and refractor astrographs. The focuser itself is very smooth and seems to be more than adequate using my Canon 1100D. I dont know how it would do with the added weight of a CCD camera, filter wheel, etc., but it has done its job so far. I am now perhaps spoiled after installing a Moonlite on my newtonian and will probably upgrade the focuser sometime but its not something that is needed at the moment.
The second thing I would like to mention is that I am very happy with how the stars appear in my images. Most of you that have imaged with newtonians and refractors know that a coma corrector or field flattener is needed. The stars in the corners of my images look very good. They are not perfect but I would say they are better than what my f/4 newt with Baader Mark III MPCC combo produces. This is also with a full size DSLR sensor. If you are using a camera with a smaller sensor then you probably will not see anything wrong with your images. Also worth noting is that the scope was slightly out of collimation when I received it. I have only adjusted the secondary screws to get a nice looking diffraction pattern on an out of focus star. Further tweeking with the primary adjustment screws could make my corner stars look even better.
Imaging at f/8 with a DSLR was pretty tough for me after being use to the fast optics in my f/4 newtonian. For this I purchased the Astro Physics CCDT67 Telecompressor. The reducer screwed into a 23mm long Baader 2"/T2 nosepiece has dropped the focal ratio from f/8 down to f/5.68 and has proven to be a very good combo. I also own the AT8IN and AT65EDQ astrograph offerings from Astro Tech. I like both of these scopes a lot but the Levenhuk Ra 200RC is an excellent telescope and is my weapon of choice for long focal length astrophotography. I also own an 8" and 10" Schmidt Cassegrain scope and this RC is many times over the better imaging scope. I would recommend this telescope to anyone looking for a long focal length astrograph.
I have managed a few test images using my Baader UV/IR modified (by Gary Honis) Canon camera. The image of the Wizard nebula is the only one I have spent a good amount of time on (4.5 hrs). The Elephants Trunk is just 21 subs and the Swan is just 14. All subs were five minutes and ISO 1600 was used. The Swan was shot at f/8 and the other two were done using the Telecompressor. The full resolution images and any future improvements to them may been found here: http://www.astrobin.com/users/rflinn68/
There will be more work from this scope in the future so be sure to check back with Little Piney Observatory for updates. I have received a new scope from Levenhuk. They have sent me a nice 80mm triplet for a test and review. After a few nights of using this scope I decided that I would be keeping it and have sold my AT65EDQ. The Astro Tech was a very fine scope but the Levenhuk 80mm will be a more versatile telescope to have in my arsenal. Test results and a thorough review coming soon!
Wednesday, October 9, 2013
Comet ISON
I managed to find comet ISON yesterday morning and put together an image that shows some galaxies in the background. Before the Sun rose I got 17X180 second subs and stacked these then layered a single sub to bring the comets core back to focus. Full size image can be view here: http://www.astrobin.com/full/59447/?mod=none
Last week this comet passed by the planet Mars on its first journey around the Sun. The comet will circle the Sun November 21-30. If it survives it could be a spectacular naked eye comet.
Last week this comet passed by the planet Mars on its first journey around the Sun. The comet will circle the Sun November 21-30. If it survives it could be a spectacular naked eye comet.
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| Comet ISON on the morning of October 8, 2013, in the constellation Leo. |
Monday, October 7, 2013
The observatory and equipment
The first thing we bought a few years ago to start observing the stars was a 10" dobsonian. It has since undergone a few modifications and continues to be a nice scope when the visual observing bug hits. There was one other scope that I owned years ago but it isn't really worth mentioning here. My wife Cara wrote a rather entertaining story of that telescope on her blog and can be found here.
The 10" dob really does put up some fantastic views since replacing the secondary mirror with a premium 2.60" 1/20 wave (peak to valley) unit from Antares Optics. I also replaced the stock straight 4 vane spider holding the secondary mirror with a curved 3 vane spider from Destiny and installed Protostar flockboard to the interior of the telescope tube. That greatly improved the contrast. While this is still a pretty nice scope for observing, the human eye just cannot see what a camera sensor can capture with a short exposure of just a couple minutes. Enter astrophotography....
After buying a Canon T3 DSLR and trying it on our dobsonian telescope we quickly realized that just wasn't going to work for anything other than some shots of the Moon. I did some research and decided to get a Celestron CGEM DX german equatorial mount and the Astro Tech AT8IN 8" imaging newtonian to get us started. The fast (f/4) optics of the telescope worked great to reveal excellent detail in objects that we just simply could not come close to seeing through an eyepiece. We were not serious into astrophotography then and just used single 2 minute exposures to explore the night skies. It was quite a treat to explore the universe from our backyard. This scope has continued to serve me well after upgrading the weak focuser with a very nice unit from Moonlite. These focusers are extremely nice and I would like to someday have one on all my telescopes.
The 800mm focal length of the AT8IN worked fine for most objects but there are several things in the night sky that are much too big to fit even on a sensor as big as the one in our DSLR. I started looking into a wide field scope and settled on the Astro Tech AT65EDQ. These little astrographs come with a built-in field flattener and are excellent for wide field astrophotography. I cannot say enough about this little scope and use it exclusively for all my wide field work. With a focal length of 420mm it provides roughly twice the field of view that I get with my imaging newtonian. With the Canon T3 it will show a field of 3 degrees wide X 2 degrees high. When you consider the full Moon takes up roughly 1/2 degree of sky you can see that this scope will show you a pretty big area.
Around this same time I was able to get a couple of nice used Schmidt Cassegrain telescopes for some long focal length observing and I thought eventually I could use them for astrophotography. The local university here had a 10" Meade LX50 and an 8" Celestron Celestar and the price was such that I couldn't refuse. These are both f/10 telescopes with focal lengths of 2500mm and 2000mm. I picked up a Celestron focal reducer/field flattener that reduces the focal ratio of both these scopes to f/6.3 which is much more conducive to astrophotography. The focal lengths then become 1575mm and 1260mm along with better looking stars in the corners of the field. I de-forked the Meade and purchased a dovetail to use it on my CGEM DX mount and eventually did the same with the C8.
The CGEM DX mount is extremely heavy and takes several trips to get set up. I decided to get a lightweight mount that would work well for observing with the bigger scopes and would serve as a nice imaging platform for the lightweight AT65EDQ. I bought the Celestron CG5 mount that has a capacity of 30 lbs compared to the 50 lb weight limit of the CGEM DX. It works great and is so light that I can just pick it up completely assembled and carry it out in one trip (minus the counterweight and battery).
Wanting then to get more serious into astrophotography I also purchased an autoguider system from Orion Telescopes and Binoculars. This allowed for much longer exposure times and nice round stars instead of egg shaped stars. Since buying the autoguider the hobby of astro imaging has really taken off. Here is a picture of the CG5 mount with the AT65EDQ and the Orion ST80 80mm f/5 guidescope mounted piggyback. I have since replaced the ST80 with a much smaller and lighter 50mm finder/guider that has been working great on all my imaging scopes.
The small apo was great for learning astrophotography. The short 420mm focal length is much more forgiving to guiding errors and really helped us get started with long exposures. Many people will get frustrated and give it up when they start out with a scope with more focal length than this so I think it is ideal for any beginner.
Once we thought we had perfected the shorter focal length I put the AT8IN on and started getting some long exposures at 800mm. The higher resolution showed us even more detail and I was anxious to try a scope with even more focal length to see the fine details on the smaller targets in the night sky. I put the Celestron reducer/flattener on the C8 to give it a try. Some people out there have good success imaging with the Schmidt Cassegrain telescope but I quickly decided this was not for me. The design of these scopes incorporate a primary mirror that slides on a baffle tube toward and away from the secondary mirror to reach focus. This causes focus shift which makes it tough to center your target. You get mirror flop when the scopes slews from one side of meridian to the other. These scopes are completely enclosed with a corrector plate on the front and take hours to reach thermal equilibrium. They also have terrible field curvature even when using the field flattener. For imaging at least, these scope are not for me and have been relegated to visual use only.
Still needing a telescope for long focal length work I began eyeing the Ritchey-Chretien (RC) astrographs. I had a few questions about them and began exchanging emails with Levenhuk Telescopes about their 8" RC with the carbon fiber tube. The saleswoman responded quickly to my questions and offered the scope to me for $160 off the website price. I told her I wasnt really ready to buy one yet and was just looking and had a couple questions. It wasnt but a few minutes later when she responded by saying she could let me have one for $300 off. Well, I'm a sucker for a good deal and I am now the proud owner of a Levenhuk 8" RC with a beautiful carbon fiber tube.
Buyers remorse sometimes sets in after purchasing something you were only looking at but I have no regrets at all. With this scope I have imaged over multiple nights and not even had to touch the focuser. The carbon fiber tube is not just for good looks. Carbon fiber is the super-hero of the materials world. It is one of the strongest and most lightweight materials on the market today. It is five times stronger than steel and one-third its weight. Carbon fiber will expand or contract much less in hot or cold conditions than materials like steel and aluminum. This makes it an excellent choice for a telescope that will be used and stored in a wide range of temperatures.
The optics of the RC have a focal ratio of f/8 which was much different than what I was used to. I discovered to get the same amount of light to the camera sensor that I was getting in 5 minutes with the f/4 scope, that I would have to start using 20 minute exposures at f/8. The challenge of twice the focal length combined with four times the exposure time was not something I was ready for just yet. To remedy this I found a used Astro Physics CCDT67 Telecompressor. The spacing between the reducer and the camera sensor determines the amount of reduction. With the 2"/T2 adapter I have the reduction comes out to be .71X and brings the focal ratio from f/8 down to a more manageable f/5.68 and drops the focal length from 1600mm to 1136mm. This is still quite a bit more than the 800mm focal length of the AT8IN and this combo has been working out great for me. They are together the second best thing to date that I have bought for my astrophotography hobby.
The best thing would be, without a doubt, the roll-off roof observatory. How many of us have spoken some not-so-kind words of our local weatherperson? Born and raised here in Arkansas I have often heard said to visitors, "If you don't like the weather, stick around a day or two. It will change." Other than the Summer months, I'd have to agree. The CGEM DX mount weighs over 100 lbs and its just not something I wanted to get set up and aligned unless the weather was sure to be good. There's been several nights since I've been into amateur astronomy that the weatherman had forecast clouds only to peek outside to find it clear. There's been several nights I couldnt sleep that I would look out to see a sky full of beautiful stars. Besides the trouble of setting things up (and then tearing it all back down!), there's this thing called tube currents. Most of my scopes take at least an hour to acclimate to the outdoor temperature.
The observatory has been the answer to all these problems. I can now go out anytime I feel like it and roll the roof open and immediately start imaging or observing. I would encourage anyone that is seriously into this hobby to build something similar. When I was researching observatories I found many that were MUCH nicer than the one we built. I also found a few that were not much more than an outhouse on wheels that just kept the scope covered and out of the weather when not in use. There's certainly nothing wrong with those and I considered that, but I wanted something that would keep a few other things stored. The style I saw more than any other was the Arrow (or similar) storage shed converted to a roll-off roof. I bought the Arrow 10 ft X 10 ft storage shed for only $300. Its not completely finished yet but for less than $1000 total I was using it on an almost nightly basis. On just about about any clear evening now you will find me out in my humble observatory with my Canon DSLR camera soaking up some photons.
So there it is. This is the equipment I am working with. If you have read this far then you are either really interested in astronomy/astrophotography, or you are kin to me. Either way, check back here at LPO from time to time to see whats happening. :)
The 10" dob really does put up some fantastic views since replacing the secondary mirror with a premium 2.60" 1/20 wave (peak to valley) unit from Antares Optics. I also replaced the stock straight 4 vane spider holding the secondary mirror with a curved 3 vane spider from Destiny and installed Protostar flockboard to the interior of the telescope tube. That greatly improved the contrast. While this is still a pretty nice scope for observing, the human eye just cannot see what a camera sensor can capture with a short exposure of just a couple minutes. Enter astrophotography....
After buying a Canon T3 DSLR and trying it on our dobsonian telescope we quickly realized that just wasn't going to work for anything other than some shots of the Moon. I did some research and decided to get a Celestron CGEM DX german equatorial mount and the Astro Tech AT8IN 8" imaging newtonian to get us started. The fast (f/4) optics of the telescope worked great to reveal excellent detail in objects that we just simply could not come close to seeing through an eyepiece. We were not serious into astrophotography then and just used single 2 minute exposures to explore the night skies. It was quite a treat to explore the universe from our backyard. This scope has continued to serve me well after upgrading the weak focuser with a very nice unit from Moonlite. These focusers are extremely nice and I would like to someday have one on all my telescopes.
The 800mm focal length of the AT8IN worked fine for most objects but there are several things in the night sky that are much too big to fit even on a sensor as big as the one in our DSLR. I started looking into a wide field scope and settled on the Astro Tech AT65EDQ. These little astrographs come with a built-in field flattener and are excellent for wide field astrophotography. I cannot say enough about this little scope and use it exclusively for all my wide field work. With a focal length of 420mm it provides roughly twice the field of view that I get with my imaging newtonian. With the Canon T3 it will show a field of 3 degrees wide X 2 degrees high. When you consider the full Moon takes up roughly 1/2 degree of sky you can see that this scope will show you a pretty big area.
Around this same time I was able to get a couple of nice used Schmidt Cassegrain telescopes for some long focal length observing and I thought eventually I could use them for astrophotography. The local university here had a 10" Meade LX50 and an 8" Celestron Celestar and the price was such that I couldn't refuse. These are both f/10 telescopes with focal lengths of 2500mm and 2000mm. I picked up a Celestron focal reducer/field flattener that reduces the focal ratio of both these scopes to f/6.3 which is much more conducive to astrophotography. The focal lengths then become 1575mm and 1260mm along with better looking stars in the corners of the field. I de-forked the Meade and purchased a dovetail to use it on my CGEM DX mount and eventually did the same with the C8.
The CGEM DX mount is extremely heavy and takes several trips to get set up. I decided to get a lightweight mount that would work well for observing with the bigger scopes and would serve as a nice imaging platform for the lightweight AT65EDQ. I bought the Celestron CG5 mount that has a capacity of 30 lbs compared to the 50 lb weight limit of the CGEM DX. It works great and is so light that I can just pick it up completely assembled and carry it out in one trip (minus the counterweight and battery).
Wanting then to get more serious into astrophotography I also purchased an autoguider system from Orion Telescopes and Binoculars. This allowed for much longer exposure times and nice round stars instead of egg shaped stars. Since buying the autoguider the hobby of astro imaging has really taken off. Here is a picture of the CG5 mount with the AT65EDQ and the Orion ST80 80mm f/5 guidescope mounted piggyback. I have since replaced the ST80 with a much smaller and lighter 50mm finder/guider that has been working great on all my imaging scopes.
The small apo was great for learning astrophotography. The short 420mm focal length is much more forgiving to guiding errors and really helped us get started with long exposures. Many people will get frustrated and give it up when they start out with a scope with more focal length than this so I think it is ideal for any beginner.
Once we thought we had perfected the shorter focal length I put the AT8IN on and started getting some long exposures at 800mm. The higher resolution showed us even more detail and I was anxious to try a scope with even more focal length to see the fine details on the smaller targets in the night sky. I put the Celestron reducer/flattener on the C8 to give it a try. Some people out there have good success imaging with the Schmidt Cassegrain telescope but I quickly decided this was not for me. The design of these scopes incorporate a primary mirror that slides on a baffle tube toward and away from the secondary mirror to reach focus. This causes focus shift which makes it tough to center your target. You get mirror flop when the scopes slews from one side of meridian to the other. These scopes are completely enclosed with a corrector plate on the front and take hours to reach thermal equilibrium. They also have terrible field curvature even when using the field flattener. For imaging at least, these scope are not for me and have been relegated to visual use only.
Still needing a telescope for long focal length work I began eyeing the Ritchey-Chretien (RC) astrographs. I had a few questions about them and began exchanging emails with Levenhuk Telescopes about their 8" RC with the carbon fiber tube. The saleswoman responded quickly to my questions and offered the scope to me for $160 off the website price. I told her I wasnt really ready to buy one yet and was just looking and had a couple questions. It wasnt but a few minutes later when she responded by saying she could let me have one for $300 off. Well, I'm a sucker for a good deal and I am now the proud owner of a Levenhuk 8" RC with a beautiful carbon fiber tube.
Buyers remorse sometimes sets in after purchasing something you were only looking at but I have no regrets at all. With this scope I have imaged over multiple nights and not even had to touch the focuser. The carbon fiber tube is not just for good looks. Carbon fiber is the super-hero of the materials world. It is one of the strongest and most lightweight materials on the market today. It is five times stronger than steel and one-third its weight. Carbon fiber will expand or contract much less in hot or cold conditions than materials like steel and aluminum. This makes it an excellent choice for a telescope that will be used and stored in a wide range of temperatures.
The optics of the RC have a focal ratio of f/8 which was much different than what I was used to. I discovered to get the same amount of light to the camera sensor that I was getting in 5 minutes with the f/4 scope, that I would have to start using 20 minute exposures at f/8. The challenge of twice the focal length combined with four times the exposure time was not something I was ready for just yet. To remedy this I found a used Astro Physics CCDT67 Telecompressor. The spacing between the reducer and the camera sensor determines the amount of reduction. With the 2"/T2 adapter I have the reduction comes out to be .71X and brings the focal ratio from f/8 down to a more manageable f/5.68 and drops the focal length from 1600mm to 1136mm. This is still quite a bit more than the 800mm focal length of the AT8IN and this combo has been working out great for me. They are together the second best thing to date that I have bought for my astrophotography hobby.
The best thing would be, without a doubt, the roll-off roof observatory. How many of us have spoken some not-so-kind words of our local weatherperson? Born and raised here in Arkansas I have often heard said to visitors, "If you don't like the weather, stick around a day or two. It will change." Other than the Summer months, I'd have to agree. The CGEM DX mount weighs over 100 lbs and its just not something I wanted to get set up and aligned unless the weather was sure to be good. There's been several nights since I've been into amateur astronomy that the weatherman had forecast clouds only to peek outside to find it clear. There's been several nights I couldnt sleep that I would look out to see a sky full of beautiful stars. Besides the trouble of setting things up (and then tearing it all back down!), there's this thing called tube currents. Most of my scopes take at least an hour to acclimate to the outdoor temperature.
The observatory has been the answer to all these problems. I can now go out anytime I feel like it and roll the roof open and immediately start imaging or observing. I would encourage anyone that is seriously into this hobby to build something similar. When I was researching observatories I found many that were MUCH nicer than the one we built. I also found a few that were not much more than an outhouse on wheels that just kept the scope covered and out of the weather when not in use. There's certainly nothing wrong with those and I considered that, but I wanted something that would keep a few other things stored. The style I saw more than any other was the Arrow (or similar) storage shed converted to a roll-off roof. I bought the Arrow 10 ft X 10 ft storage shed for only $300. Its not completely finished yet but for less than $1000 total I was using it on an almost nightly basis. On just about about any clear evening now you will find me out in my humble observatory with my Canon DSLR camera soaking up some photons.
So there it is. This is the equipment I am working with. If you have read this far then you are either really interested in astronomy/astrophotography, or you are kin to me. Either way, check back here at LPO from time to time to see whats happening. :)
Saturday, October 5, 2013
Welcome to the blog for the Little Piney Observatory
Little Piney Observatory is a Roll-Off-Roof observatory located in Johnson County, Arkansas. The observatory opened for operation in August, 2013, and while there is still work to be done on the building, it has already earned the distinction of being one of the best astrophotography investments we've made!
I'll be posting updates here as the mood strikes me, so you're invited to check back every now and then to see what's happening.
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