Perhaps like Edmund Halley in 1677, I “rediscovered” the largest globular cluster in our galaxy, totally randomly! It’s about 4:30 am. A frequent ritual up here in Mayhill NM, at the astronomer’s living quarters, base of Mintaka Hill, I go outdoors before sunrise to do some binocular viewing from the deck with my 16 x 70’s. Take advantage of the dark skies! So I’m sweeping around the sky and moving along the horizon to the south…Boom! What the heck is that? Looks like M13 on steroids! M13 known as the largest globular cluster seen from the Northern Hemisphere contains some 300,000 stars. Omega Centauri has 10,000,000!! I see that I am looking in Centaurus and I’m about 10 degrees above the horizon. Yep. That’s definitely the legendary Omega Centauri! Spotted for the first time in my life! A bunch of people in our neighborhood here have told me you can see it but it’s not easy. For most folks in the northern hemisphere it’s not visible due to sky glow in most areas and the fact it is skirting the horizon. Really a southern hemisphere target. I assumed you had to be higher up on the mountain here to catch it. I look with the naked eye to the South and definitely it’s blaring right at you at only magnitude 3 and change! A much easier target than I could have imagined. I am sure from the observatory it can be imaged especially since I am facing due South and have the drop down wall. Fortuitous planning on my part! But, before I image it I’m going to look through the refractor tomorrow. Can’t wait!
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!
Probably everyone who visits a dark sky site with any regularity has the urge to take “that shot” of the southern Milky Way. With spectacular weather up here for the 4th that’s exactly what I did at about 1 AM when the Milky Way was just past meridian. So while I don’t have the observatory up and running yet, we have a large deck where I can set up a camera and tripod, and with the aid of the Polarie Star Tracker (Vixen Optics) I took 24 frames each 3 minutes long. The Polarie device is basically a small synchronous motor, battery powered with 2 AA batteries, that you can screw your camera onto and it will allow time exposures of the sky. There is a small site hole in the body of it to site on Polaris. The tracking is decent. I used a Canon 60D modified with a 10-18mm zoom set at 10.
“Practice staring at the Milky Way if you want to gain some understanding of its structure”, J Robert Oppenheimer. (Astronomy Magazine July 2016 p.51 Richard Wilds author)
Sound advice from the first director of the Los Alamos National Laboratory! The same advice he gave to Russian born astrophysicist Sergei Gaposchkin, who spent his free time drawing the entire Milky Way in ink from his viewing site at Mount Stromlo Observatory in Australia in the late 50’s! So I decided, now that I had a dark sky viewing site I would do the same, armed with a reproduced representation of the Milky Way, that was created by Dr Gaposchkin, published by Astronomy Magazine showing the details of the Southern Milky Way with all the dark nebulosity sweeps and curves. I encourage everyone to read this excellent article by Richard Wilds in the July issue of Astronomy. Anyway from my dark sky viewing site in Mayhill NM at Mintaka Hill, I can see the Milky way all the way to the horizon. We’re a Bortle 2 sky on a scale of 1 to 9. It’s very dark. Not too many areas like this certainly in the continental US. It’s a spectacle you cannot get tired of. Even without a telescope or anything other than my eye, every time I have a chance to get outside up here I make a point of doing so. Last night at around 1:30 the Milky Way was directly overhead. We are obviously still in the Northern Hemisphere so we can see down to just below Sagittarius into the constellation Lupus. I had always known that Sagittarius was the direction of the “center of the galaxy” and I have been able to see fairly dense star clouds in the area at other sites such as my home 2 hours from here in Las Cruces, NM but nothing that really looked like an actual galaxy center structurally, until now. After about 15 minutes of dark adaptation I began to notice a distinct nebulosity extending from Sagittarius and seeming to wrap around the head of Scorpius. The width of this “bulge” was about twice that of the main Milky Way band. Inside of the bulge was an area consisting of smaller streaks and waves of dark patches, obviously dust. AHA! The Central Bulge of the Milky Way is discovered! Honestly it is like being transported in a space ship right into the heart of any edge on galaxy you may have observed, right next to the galaxy’s core! So check it out the next time you have a chance to observe in a dark site..and take Astronomy July issue page 51 with you. Thanks for reading!