The Trifid nebula, whose name means “divided in 3 lobes” is an amateur favorite. An island of HII region which is the red portion (HII regions are emission nebulae created when young, massive stars ionise nearby hydrogen gas clouds with high-energy UV radiation causing the gas to emit red light) , a blue “reflection “portion which occurs when light of the nearby massive blue stars reflects off of the dust, and a “dark nebula” portion which divides the nebula into its 3 lobes. There is also an open cluster of stars in the field. The Trifid is 5000 light years away toward the center of out galaxy, hence the very dense surrounding star fields and dust.
I completed my test of the Tak FS120 imaging capability and you can see the result below. I was pretty happy with it, especially considering the very modest set up I am using (see last entry) . For the full resolution image you can click on the thumbnail on the right side of the blog under “my astroimages”. I am looking forward to more projects with it!
Until next time. Thanks for reading!
M20, the Trifid. Single raw image 5 minutes.
This is the fully processed result! 33 x 5 minutes or close to 3 hours of data. I tried not to overprocess it but to preserve the natural nebula colors and bring out the background dust behind the dense star fields.
Can’t remember the last time I was actually “at the telescope”. Not with automation, executive programs, remote operations etc. However as luck or bad luck would have it I encountered another hardware failure on the now 9 month old Paramount. This time it was the PCB on the MKS 5000 control unit. So with my main imaging platform down I went back to basics. Back to the reason I came here in the first place. The dark sky! It’s still there. I happen to have a Tak FS102 refractor. This is a wonderful instrument. Let’s look at this for a minute. The FS-102 is one of the long discontinued Takahashi refractors. The FS series are some of the finest small refractors ever made yet supposedly for visual use only. Why is that? Did some “Dark Lord of Imaging” declare you can’t use it for that? Without going into a long treatise on refractive optics, let’s just say that the FS scope being a doublet lens design was replaced by the triplet lens designs (Tak TOA and TSA) which “supposedly” give better chromatic aberration correction which “supposedly” is better for imaging. Each wavelength of light coming through a lens “bends” or refracts at a different angle so without correction the red light comes to focus at a different point than blue, etc. Contemporary refractive optics (known as apochromatic using ‘ED’ or ‘extra low dispersion’ glass) were designed to correct for this and prevent what is known as chromatic aberration which appears visually as weird color fringes around objects. Apochromatic optics can consist of doublet lens or triplet lens designs.
But wait a minute. The FS is a fluorite doublet. Fluorite is not a glass. It’s a crystalline mineral and it has superior optical properties to glass , including very high transmission of light and low scatter. ‘FS’ stands for “Front Surface” meaning the fluorite element is on the front. It is true I obtained this scope mainly for visual use and the views are amazing here; strikingly better in my opinion than in my triplet William Optics refractor of similar size hands down. Outstanding crispness and color! I think it’s the best I’ve seen in a scope of this size. In my opinion if the scope gives you excellent optical performance visually, then why would that not translate to imaging performance? I decided to give it a try.
So under the incredible dark moonless night sky here at Orion’s Belt Remote Observatory in the Sacramento Mountains, with the Summer Milky Way coming in to full bloom over the horizon at about 10 pm, I set up the FS for an imaging session targeting an age old favorite: M20, the Trifid Nebula, in the constellation Sagittarius. The Trifid has everything in one package. It has an open star cluster, an emission nebula (the red portion), a reflection nebula (blue portion) and a dark nebula in the middle creating the trifurcated appearance. I have a small Tak guidescope mounted on the FS, just for occasions like this. I hooked up my Canon 60Da and connected the Lodestar X2 guide camera to the guidescope. I plugged the Lodestar into the guide port on my Celestron AVX mount and took about 3 hours of images! The steps were as follows:
1) Polar align the mount. I used Polaris and sighted it with a laser pointer. Pretty rough but adequate
2) Calibrate the mount. Most of the go to Celestrons do it the same way. Use the hand pad and punch in 4 stars, 2 on either side of the meridian. I put the Canon in “live view shoot” mode which is very handy because you don’t have to keep taking exposures to find the star you’re calibrating on. It is basically a video mode but very high sensitivity. It just works! I use the brightest stars out there.
3) Refocus. Once the calibration is complete I will focus on the last star. I use the live view mode and use the magnification function to blow up the star, then carefully focus until the star image is as small as possible. The FS focuser is very solid but it is not a dual Crayford style so you have to go slow.
4) Slew to M20. Take a 15 sec image and make sure the framing is what you want. In this case I had to use the hand pad to make small adjustments.
5) Finally you start the guiding process. I used PHD2 guiding software which is freeware and works with a number of guide cameras. Outstanding program! Very simple to use. I really was not sure what kind of guide performance this simple AVX mount would have but I was pleasantly surprised that it responds quite well to guide commands . It just works! All I did was plug the Lodestar into the port called “autoguide” and configure the PHD2 software. You pick a guide star on the screen and click on the guide button! Folks, it does NOT get any easier.
So that was it. Now you can be the judge! (see below) Honestly I think it did pretty well for a single 5 minute raw image! I will update you on the final result after processing etc. Couple of points. One is that you do need a flattener for this as you do for most refractors. I borrowed the one I was using for the William Optics which is identical diameter and close to the same focal length. The FS is an F8 where the WO is about F7. It seems to do the job as the stars are perfectly round to the corners of the image. Second point is you need to spend time focusing. There is no automation of this. This is just old fashioned adjust until it’s right.
Didn’t think this post was going to be this long but the night “back at the telescope’ was the most fun I’ve had in quite some time. So far I have not been the victim of any spells cast by the “Dark Lord of Imaging” !
Thanks for reading!
Back to basics imaging set up! Tak FS 102, Canon 60Da with flattener, Lodestar guider, Tak GT40 guidescope, Celestron AVX mount
Ok so I’m not in the warm room! or in the astronomers quarters at the base of the hill watching it happen remotely. I am “at the telescope” under the glorious Milky Way while the images are being captured. I dropped the south wall down and did some binocular viewing during the session. This is astronomy folks!
M20, the Trifid. 5 minute raw image with the set up shown above. A jewel in the stellar sea of the galactic center! You can see the edge of the Lagoon nebula in the lower right peeking through. Ok so I know it’s not a full res image. BUT at full resolution the stars are still round and not bloated. Can’t wait for the final result! Fluorite optics folks! That’s where it’s at …for refractors anyway 🙂
At last first light for the Astrotech 12″ RC Truss! Finally after collimating, establishing a new pointing model with the new payload and working out some glitches with the new image scale in the various control programs a successful 2 hour test run was accomplished. For our test I chose a globular cluster. This is an excellent way to assess the general alignment and collimation of your optics. Stars are unforgiving especially at the full resolution of your set up. How many times have you seen images posted of nebulae etc which look great at fractions of the full image scale only to show the egg-shaped stars when the true full resolution version is revealed! Don’t be like those guys!
Stars are either round or they are not. A star cluster especially a globular has lots of stars so they make an excellent test for your system. Now there is a quantitative way to determine “roundness”. It’s called aspect ratio. This is the ratio of the width to the height of the star image in the case of stars. The program CCD Inspector (CCDWare.com) is able to determine that for us. The values in the program are read as percentages. For example if there is a 5% difference between width and height the aspect ratio is 5. In this calculation therefore lower numbers are better. My own experience tells me that when you go much above 15 you start to see the stars becoming egg-shaped. So as a matter of convention I tend to throw out any subs with aspect ratios over 15 or so. CCD Inspector is very handy in that you can simply place your cursor over the star and it automatically reads the aspect ratio and full width at half maximum. Last night the seeing was excellent so most of the subs registered in the low 2’s for FWHM
Now about our target! M15 is well positioned right now in Pegasus almost directly above us so this is great for our test object. It is one of the most densely packed globulars in the Milky Way with an enormous number of stars in the center. It has a number of variable stars and pulsars in it as well, AND the first planetary nebula discovered inside a globular!
I think overall I am satisfied with the test results and we can now move forward with our imaging projects!
This is a raw 6 minute luminance image of M15. Yes there are significant star blooms (vertical streaks) however this is the trade off with a highly sensitive CCD and these can be processed out
At full resolution the central stars are most definitely round! At the periphery (not shown) there is a subtle decrease in roundness due to the field curvature from the optics but this is expected
This is the CCD Inspector Viewer pane which shows the very nice feature where you can display the object parameters by just moving your cursor over it. Shown is a core star with aspect ratio and Full Width at Half Maximum values. I think this is a keeper!
Messier 81 or Bode’s Galaxy is a spiral galaxy 12 million light years away in Ursa Major. It is a favorite target for both professional astronomers who study its active galactic nucleus harboring a 70 million solar mass super massive black hole, and amateur astronomers who take advantage of the large size and brightness for both visual observing and astroimaging.
Back in 2007 I took my first image of M81. I was just thrilled to be able to take an exposure longer than 1 minute and capture any detail with round stars! In under 10 years with improvement in equipment and processing techniques, much more information about the structure of this galaxy is now appreciated. In my recently completed image of M81 (full res version can be found on the flickr site- see link to astroimaging) you can see not only Arps’s loop, Holmberg IX galaxy but also some very interesting nuclear structure! This is not processing artifact folks. I have not seen this on any published image thus far and wonder what physical properties give rise to them! We have come to assume that galactic nuclei in visible light are just bright blobs of gas, but clearly this is incorrect!
Image taken in 2007 with a 10″ newtonian and SBIG ST8XE camera
M81 just completed. 10″RC and SBIG STXL6303E. Larger arrows point to the now appreciated “Arp’s loop”. This is a loop of gas emanating from the galactic disc but recently at least some of this is believed to exist in our galaxy as “galactic cirrus”. Halton Arp was an astronomer who catalogued interacting galaxies and galaxies with unusual structure and features. The smaller hatched arrow points to Holmberg IX, a dwarf irregular satellite galaxy of M81 formed only 200 million years ago, the youngest nearby galaxy!
Arrows point to peculiar nuclear structure! The arrow closer to the center points to a strange vertical projection of dust toward the center of the nucleus with a round knob-like top! What is it and what causes it? Who says imaging is not science!