Welcome to a journey into our Universe with Dr Dave, amateur astronomer and astrophotographer for over 40 years. Astro-imaging, image processing, space science, solar astronomy and public outreach are some of the stops in this journey!
There are over a thousand open star clusters within our own Milky Way galaxy. Each contains up to a few thousand stars which all have formed from the same molecular gas cloud and all have roughly the same age.
In the southern part of the “winter” milky way lies an often overlooked treasure trove of open star clusters. Just to the east of Sirius, the brightest star visible from the Northern Hemisphere, and it’s constellation Canis Major, lies the constellation Puppis. Centuries ago the entire region was occupied by the huge constellation “Argo Navis”, the ancient ship of Jason and the Argonauts. The Argonauts were sailors in Greek mythology who accompanied Jason on his trip to find the ‘Golden Fleece’. In the mid 18th century Argo Navis was divided into three separate constellations: Puppis, Carina and Vela. Puppis is the northern most of the three. Besides being a constellation containing open clusters, Puppis also harbors several extrasolar planets discovered over the past 15-20 years.
In the images above, four open star clusters are seen. This field is virtually identical to the one I see through my 16 x 70 binoculars from the dark skies of Mayhill NM! To the lower left is Messier 46 or M46, 5000 light years away. M46 has about 500 stars estimated to be about 250+ million years old. The planetary nebula NGC 2438 lies on the northeast edge of M46 (about the 11 o’clock position in the image) but is most likely not part of the cluster.
Just one degree west-northwest of M46 (to the right in the image) lies another open star cluster Messier 47 or M47. M47 is much younger in age, about 78 million years old and is 1600 light years distant. There are also about 500 stars, mostly high temperature giant blue stars, reflecting the cluster’s young age, as well as some red giants. Between M46 and M47 is the small and dim cluster NGC 2425.
NGC 2423 is the open cluster just above M47 in the image and is much closer to us. It contains several red giant stars, at least one of which has an orbiting planet discovered in 2007. The distance to that system is about 2500 light years.
M101, the “Pinwheel Galaxy” lies 21 million light years distant in the constellation Ursa Major. It spans 170,000 light years across (By comparison our Milky Way is 100,000). It is occasionally referred to as the “Northern Pinwheel” to distinguish it from the other galaxy M33 with the same moniker but in the constellation Triangulum. M101 has an apparent size of 30’ x 27’ which is about the same as the full moon! It is a Hubble Type Sc galaxy, with loosely wound spiral arms, clearly resolved into individual stellar clusters and nebulae; a smaller, fainter galaxy core.
This galaxy interestingly contains 11 nebulae bright enough to have their own NGC numbers. I have uploaded a separate annotated image (below) which shows most of these. Most likely the reason for this is that M101 has undergone tidal interactions with dwarf galaxies in its group. The galaxy NGC 5477 which is to the far right in the image is the leading suspect. The tidal interactions trigger collapse of numerous molecular clouds within M101 into active star-forming regions that produce massive blue type O and B stars. The blue giants emit ultraviolet radiation that ionizes the hydrogen gas within the clouds which produces bright emission nebulae known as HII regions. These are the brighter red-pink areas in the spiral arms. Many are large and bright enough to be visible through backyard telescopes!
M101 expanded annotated version. The major NGC designated HII regions in the spiral arms of the galaxy are labeled: NGC 5471 is a massive HII region actively forming very high temperature blue stars which explains its bluish appearance in the image. It is approximately 200 times the size of the Orion Nebula! From top left to right in the galaxy arms the remaining brightest of the HII areas revealed by their reddish-pink glow are NGC 5447, 5450, 5455, 5461 and 5462. A few others can be seen scattered within. The dwarf galaxy 5477 is seen on the far right. This galaxy is felt to be causing tidal gravitational interaction with M101 giving rise to the HII regions.
I am sure those of you who have been astronomy enthusiasts like I have for a period of time have been asked at least once or twice by friends or relatives the “big” question: “What telescope should I buy?” Because there are so many options now it’s not that easy to answer. Reflector or refractor, cost, size, new or used, what mounts, what eyepieces etc etc all come into consideration. Let’s start with the most important variable and that is cost.
Recently I was asked what to buy and was given an initial budget of $1-200. That’s not a lot. I generally discourage folks from bargain basement deals at our well-known ginormous retailers where optical quality will be likely in the basement as well. You could easily buy a very decent used refractor in that budget but it’s not likely to come with a mount and especially if you are just starting out that isn’t going to help much. You could get lucky and find a used package deal but then figuring out how to use it since it is not likely coming with instructions will be a problem, and what if something is wrong with it? You are then stuck with basically dead metal unless you are experienced enough to figure out a work around.
The question then becomes, what is the least expensive option for decent quality from a reputable source that a beginning observer could really enjoy? I have recommended binoculars a lot and those are great for people who live under dark skies, but the challenge is, even then, it’s hard to find objects let alone know what it is you are looking at.
Since it had been a couple of years or more since I was last asked about what telescope one should buy, I did some searching into what was available in the beginner market. I came across a recently introduced product line from our good friends at Celestron. Kudos to them as they just celebrated their 60th anniversary! No other company that I know has done a better job of staying relevant in amateur astronomy with products appropriate for everyone from beginner to advanced imager. Hard to believe they are still going strong from the days of the C8 orange tube SCT, the iconic telescope I remember from the early 70’s (image above)! Anyway that is most definitely a solid telescope company that produces good quality stuff. But is it affordable at the beginner level?
Celestron’s Starsense Explorer line of telescopes comes in four different configurations, two refractor and two reflector. I recommended the refractor as the reflectors which come in 4+ and 5 inch might present the added variable of collimation which a beginner certainly does not want. The 80mm refractor sells for $180 and the 102mm refractor is about $400. So what is included? Obviously the telescope but also an altazimuth mount and the StarSense feature. What is that? It appears that Celestron has incorporated smartphone technology into basic beginning telescope pointing and object finding! Genius! This was a way to provide a beginner with an experience where you could actually learn what was up in the sky and you had the means to locate it. Fantastic!
The StarSense system had been out for awhile and was very well received from what I could see, so I felt it was a good recommendation. I felt the smartphone feature was really a plus for those not familiar with star gazing. For an adult beginner I lean toward the 102mm vs the 80 which I think they would quickly grow out of. The 4” refractor is a classic size for observing and is extremely versatile in that you can enjoy great views of deep sky objects and with a bit of magnification nice views of Jupiter and Saturn. Our friends did decide to buy the Celestron StarSense AZ 102 refractor. A couple of weeks later I got a call asking if I could help with setting up and basic use of the telescope. Great! I finally get a chance to do a real equipment test report! I was excited to see how the StarSense system worked and if it really did work as well as reported.
TEST REPORT: The Celestron StarSense Explorer AZ102
The Celestron StarSense AZ 102 refractor is a 4” achromatic refractor, meaning there is no extra low dispersion or ED glass to correct the chromatic aberration. This is expected in a beginner level scope certainly, but to be fair even for an advanced observer it’s not a show stopper at all, for good quality achromats can provide excellent views. Celestron provides their well-known XLT coatings on the optics and this telescope comes “fully coated” meaning all surfaces are coated. Optical coatings reduce internal light loss and glare and ensure even light transmission, resulting in greater image sharpness and contrast.
The focal length of the AZ102 is 660mm or f/6.5, so a decent compromise between long and short focal lengths. The mount is an aluminum manual alt-az mount with a slip clutch and slow motion hand controls. The telescope tube mounts on a side-positioned Vixen style or CG-5 dovetail. The tripod legs can be extended up to just over 4 feet high. The entire assembled platform weighs under 15 pounds.
When I picked up the telescope it was already completely assembled. The instructions are well written and easy to follow, apparently easy enough for someone with no prior telescope experience to put together! Examining the equipment outside I found the telescope tube to be a sturdy aluminum and the side mounting dovetail interface very secure with no toggle. Most of the weight is taken up by the mount head which is what you would hope. The mount is quite solid. However the entire assembly is light enough to lift up and reposition with one arm. Moving the telescope is very smooth but not too easy and it stays exactly where you place it. There are two flexible hand control knobs which move the scope in altitude and azimuth in small increments. It works very much like a Vixen Portamount if you’ve ever owned one of those, but if not you have to be somewhat firm with your turns of the knobs. The mechanism is very stable and secure and there is certainly no backlash of any kind. The tripod legs are a lightweight aluminum and there are 2 segments in each leg. With the legs fully extended it is plenty stable for the lightweight telescope OTA.
The scope comes with a red dot finder scope powered by a small battery. There is a knob on the side to turn the battery on and off and two adjustment knobs to tweak the finder position relative to the object you are pointing at.
The focuser is a standard rack and pinion and very stable. You do not have to lock it in position. The telescope comes with a diagonal to facilitate viewing and two eyepieces, a 25mm and a 10mm. The 25mm is your wider angle eyepiece and the one that will be used mostly. The 10mm would be for higher magnification.
The smartphone dock attaches to the inside of the mount head and there is a simple spring-loaded bracket that holds the phone in the dock. Two knobs underneath the dock allow you to move the phone’s camera lens over a mirror which points up at the sky. This is the interesting part. Apparently the camera via the mirror pointing up to the sky is able to record starlight to enough of a degree that the telescope’s position can be determined! If you go on the Celestron site they insist this is not GPS mediated but some algorithm called LISA (Lost in Space Algorithm) which they say is “utilized by satellites that get lost in space”. Ok great. Whatever. As long as it works.
First item of business was to align the finder with the tube optics. During the day I pointed to a structure on a mountain about 3 miles away using the red dot which is very bright. It was a little way off of the target as viewed in the telescope so I adjusted the finder position, fairly easy to do, until the red dot pointed to the object that was centered in the telescope field. I only used the 25mm eyepiece which I found to have a small aperture for the focal length. Next I downloaded the StarSense app. There is a key code that you enter to enable full functionality of the app. Now I tend to over-analyze things and I tried reading the app directions online before actually using the app. This was a mistake because in the online directions it mentioned aligning the targeted image with the camera’s bullseye which my iPhone does not have, but the app does once it takes control of the camera functions. Best approach was to open the app and follow the directions! It completely walks you through the set up.
The key step, once the finder is aligned with the telescope optically is to align your phone with the telescope. Almost all smartphones are compatible. There is a list of them on the Celestron site. However the cameras are all going to be slightly different so as long as you adjust the camera position to get the largest field width you can you should be good. Once you have the telescope pointed to a definite target and the app is open it will ask you to align the target to the central dot in the camera window. Once this is complete you are ready to observe. I thought it was an odd recommendation to leave your phone in the dock until it gets dark once it was aligned. Later I realized you could do the alignment at night just fine. It is not necessary to do it during the day.
The actual StarSense app contains a wealth of information about the objects you’re looking at. There is enough there to keep anyone interested in a single object for most of the night! The graphics are great and all of the key bright most visible objects are right there on the screen. Everything you need to do to get it to work is pretty much spelled out in the app. Once you open it, it will ask if you need to align the phone to the telescope or not and once it is aligned it will start by locating the telescope position. I was observing under a fairly bright gibbous moon and right out of the gate it was able to locate the telescope position! Amazing!. Click on the star icon at the bottom and up pops a list of currently visible objects. Let’s go to the Orion Nebula. When you select it, the app produces a ray of bright arrows pointing to the object and this tells you where to move the telescope. I used the slow motion hand knobs to manually slew the telescope to the target. As you get close to the target a large circle bullseye appears, first red, then yellow as you get closer and finally green when you’re there. Cool! So I look in the eyepiece and ………. No nebula! Darn! However I can see that the faint glow of the nebula is just visible along the edge of the field.
Ok so it looked like perhaps the phone alignment was slightly off. I re-aligned the phone using the same steps as before but since it was at night I could align to the moon which was easy. However after that the StarSense app was unable to locate the telescope position regardless of where I pointed it. No matter what I did it the app would not seem to work. I uninstalled the app and then re-installed it and it did work once but not after that. The same thing happened when I used a different phone.
With the StarSense app functionality obviously not being consistent at all, I had to contact tech support. On the Celestron site, unfortunately like just about every website, support is very difficult to find. It’s buried amidst FAQ sections and other product info. I did come across an FAQ section for StarSense which was helpful but didn’t answer my specific questions. Finally I found a support page where you could at least “submit a ticket” so someone could address my specific problem. Two days later I received a reply. Over the next several days I worked on troubleshooting the problems with the app in communication with tech support. They suggested I first try a darker site, despite the fact they claim the app is fully functional even in light polluted areas. I brought the telescope up to my remote observatory where it is certainly dark enough and unfortunately it didn’t seem to make a difference.
Bottom line is I finally solved the app problems on my own and I will be creating a separate page for that (it’s done!- see link below) so StarSense users can hopefully find it and make use of it! This post is already super long so I won’t include it here. I thoroughly enjoyed my test experience here and also the problem solving was very satisfying.
What we liked about the StarSense AZ 102:
Excellent equipment quality for the price. Both the telescope OTA and mount are solid. Zero issues there with the telescope optics or mount mechanics. I forgot to mention the actual views of stars and nebulae were very crisp. The only time I knew it was an achromat was when looking at the moon there was some blue color fringing on one limb but not much at all. If you don’t know anything about optics you wouldn’t even notice enough to question what’s happening. The StarSense app content is great. A wealth of information, excellent graphics and when it does work it’s a great user experience. Price: I think overall for the package it is very good value. Even if someone has trouble with the app, the telescope itself is completely functional. Red dot finder: a great feature and works very well.
What we didn’t like:
Eyepieces are low end and kind of difficult for new users to adjust to with the small aperture and low eye relief. I think 25mm is a tough ask for this kind of pointing technology to be consistent. In fact I found that replacing the 25mm with a 32mm that was in “my collection” made a huge difference in pointing accuracy. A 40mm would be even better. StarSense app inconsistent functionality: This was perhaps the most disappointing. While I was able to finally figure out how to get it to work consistently, I would be concerned for a complete beginner to sort through it if problems such as what I had occur. Hopefully my troubleshooting page will be of help! Tech support. I was disappointed to find that Celestron tech support was kind of average in terms of accessibility. Now to be fair they were helpful once they did answer my query, but it did take a couple of days for them to respond.
Final score for the Celestron StarSense Explorer AZ 102 refractor is 4/5 stars. Would I recommend it again? Yes I would. I believe that I resolved the app issues and I would say that especially if the buyer of the telescope has a friend or relative who is knowledgeable in the field, then definitely go ahead with the purchase. If not they can read this blog 😊
For those of you who found this post and would like to see more on troubleshooting the StarSense app, go here.
The StarSense app option really does add a whole new dimension to star gazing!
In 2003, Tom Cave, renowned American amateur astronomer, telescope maker and planetary observer, passed away. I never met him or knew him personally, but he did have a very important influence on my astronomy life as his coveted product at the time, the Cave Astrola newtonian, was the only telescope I ever owned until about 8 years ago! The story of the Cave Astrola line of telescopes is really the story of what I consider the golden age of amateur astronomy. From about 1950 until the mid to late -70’s, the Cave Optical Company manufactured telescopes for amateur astronomers and universities throughout the country. The optical quality was second to none. All the optics were hand made and the primary mirrors were signed by Tom Cave himself.
For myself as a youngster, astronomy was really an obsession. I went to the local planetarium, read all the magazines and at night I would set up my parents’ table-top spotting scope to look at the Moon through a foyer window, when it was visible. Back in those days of course it was years before any internet or even a personal computer. The space program was in its’ hey day. Amateur astronomy was thriving. Light pollution was not nearly the obstacle it is today. If you were growing up in those days in this part of the world and were an astronomy enthusiast you remember the ads like the one pictured above. There was also Unitron and Questar, Edmund Scientific and Dynastar. Amateur telescope making was very mainstream back then and at the time the cost for supplies was quite nominal. Even as a youngster my allowance was almost enough, with a bunch of odd jobs mixed in 🙂
And so that’s what I did. I read the telescope making books and set out to grind an 8″ mirror in our basement at the age of ( I think it was) 11. I actually got reasonably far into the project but once the primary glass was a smooth spherical surface I then had to convert that to a paraboloid surface using what to me seemed like very complex testing devices and methods. I just didn’t have the math skills yet. I realized it just wasn’t going to happen and I was getting impatient. Meanwhile I kept seeing that Cave Astrola ad and understanding I didn’t have the resources for something like that at the time, I decided to do some work until I did! Three years of car washing, lawn mowing and other odd jobs I could find got me about 70% of the way there. My grandfather, bless his soul, took notice of my efforts and decided to cover the rest of the cost for a 10″ Cave Astrola Deluxe newtonian. Wow!
I believe it was 4 months later that the telescope arrived. It was Christmas in July! It was really hard to believe that the telescope crate was sitting right there in our garage. Assembly was thankfully very straightforward. The telescope tube was not too heavy for one person. There were not too many parts to it. Tripod legs with the wheels had to be bolted onto the pier. The telescope cradle was easy to put on the mount and the tube rings just bolted onto the cradle. It was a very interesting tube design as the telescope tube could be rotated which made it easier to reach an eyepiece. In the newtonian optical design the eyepiece sits at the top of the tube. The “deluxe” portion of the package was the synchronous motor in the mount that enabled the telescope to track the stars. A toggle switch with an amber light came on confirming it was “on”. Of course there was no clicking on an object in a planetarium program and having the telescope slew right to it! We had what were called setting circles which were graduated metal circles with degrees etched into them for the declination axis and hours and minutes on the right ascension axis. You had to learn how to find objects by moving the telescope a specified number of hours and minutes of right ascension and a certain number of degrees of declination, or you could use the popular “star hopping” method many amateurs did by first locating a bright star near the object and then moving the telescope to the target. There was of course a small finder scope on the tube that was a great help. I had no problem with it as I had been reading for a few years prior to actually using a telescope and was very well prepared!
I had many years of enjoyment using the Cave 10″. Every clear night I would wheel it out of our garage and spend hours observing. The views of star clusters, planets and some nebulae were really spectacular. I dabbled in some film photography of the Moon and planets. As the years went by and I was off first to college, then medical school and beyond, I had to pack up the Cave. The Cave Optical Company sadly went out of business in the early 1980’s. It could not compete with the new companies like Celestron that offered compact reflecting telescopes with the same size mirrors.
My Cave newtonian suffered numerous journeys from one garage or basement to another and kind of fell into a bit of neglect and disrepair unfortunately as I just did not have any spare time for astronomy or anything else for that matter outside of my medical training and eventual practice.
Almost 20 years later we settled in an area of Western Massuchusetts where we lived for about 10 years. It was at that time I decided to resurrect the Cave newtonian. We were finally in one place long enough where it was feasible to do a project like this. I felt like I had been frozen in time and finally waking up to a totally new astronomical world! There was so much that had happened since those days of wheeling the telescope onto our driveway. There were computers and these devices called “webcams” that could take digital pictures of deep space objects. There were “ccd cameras” and all sorts of new technology I had never seen or heard of before! It was wild!
The first item on the project list was to get the mirrors recoated. Thankfully the internet had arrived and it was easy to locate many amateurs who had restored the Cave telescopes to like-new condition. I cleaned up the telescope tube, replaced the screws on the rotating rings, repainted the inside of the tube and got the rust off and repainted the affected parts of the mount.
I decided I would need a shelter for the telescope since there was weather in our area for sure and winters could be harsh. A fiberglass dome is what I settled on and placed it on a wooden deck. With the advent of the “Go To” telescope technology I realized that telescopes could now be directed by a computer to point to any object you wanted! We were a long way from setting circles. I therefore had to figure out how to replace the gears with ones that could be connected to a computer. Once again the internet was key and I found a place that sold equipment for exactly this kind of “stepper motor conversion”. It worked very well for telescope pointing for visual observations. I saw countless objects I had never been able to find before! But there was one problem. I was learning about the “new ccd astronomy” and just as the 50’s through the 70’s was the golden age of amateur astronomy, I realized I was in the midst of the beginning of the golden age of astroimaging! I was seeing all of these fantastic images and thinking to myself I had to get into this. I started with a simple webcam that was modified to take longer exposures and this is what really blew me away. I saw how after just 10 seconds of exposure time you could see spiral arms of a galaxy! That is really what I think got me hooked for good.
As I moved further up the learning curve I began to realize that I was going to be limited with the telescope I had and the mount I had taking really deep quality images. The long telescope tube and eccentric load was not going to cut it unless I had a heavy duty mount to carry it. I was too attached to the Cave and kept thinking while no one I knew or saw was taking deep space images with it, why would it not produce spectacular images given the right conditions?
I contacted a machinist actually in New Mexico interestingly who was very well known in astronomy circles and was unanimously “the guy” who could do any modifications needed for just about any telescope-mount configuration. He was able to manufacture a pair of subplates so I could mount the Cave in it’s original tube configuration to a Paramount ME robotic telescope mount, the most capable heavy duty mount you could have at the time. I had a cement pier installed with bolts to attach to a steel pier extension which the Paramount was in turn bolted to. I replaced the original rack and pinion focuser on the telescope with a motorized focuser to which I could attach a ccd camera. Despite all the 21st century modifications, the mirrors were still original Cave. With this classic newtonian minted in the height of late 20th century amateur astronomy I was finally able to produce quality 21st century images! I continued to do that for about 6 years and then it was time to move again. That was the move to the great Southwest US where we are now.
With technology continuing to evolve I decided that after accomplishing my goal of making my old Cave newtonian relevant in the new century, it was time to move on from it. Despite the successes and even one magazine publication from it there were factors that were going to be problematic going forward. The ccd camera I was using, an SBIG ST8XE was a nice camera but already old technology. It was only a 1-2 megapixel camera and my field width had to be very limited to avoid having to use corrective lenses for the well known coma problems seen in newtonian optics. The secondary mirror was undersized for astroimaging and the mirror cell was ancient, using wing nuts and springs to collimate the optics. The technology trend was for faster lighter weight newtonians with wider fields made possible by newer and more effective corrector lenses. Bottom line was that with our move to the Southwest I was going to go in a different direction. I donated the mirrors to a local astronomy club but I have kept the original telescope tube as an important piece of my astronomy life! I think both Tom Cave and my grandfather would have been very pleased to see what I was able to do with a classic amateur telescope! I am indebted to them both.
And finally just a few of my favorite images taken with the Cave:
And that’s about it for amateur astronomy memory lane!
Tomorrow just before sunrise, March 5 that is, we will be able to see yet another planetary conjunction! This time the orbital planes of both Mercury and Jupiter coincide so they can appear to be very close to each other if their respective orbital positions in the sky relative to Earth are nearly the same. They appear to literally bump into each other! On the morning of the 5th they will be a couple of tenths of a degree apart. Mercury rarely travels far enough away from the Sun to actually be able to see it. It is so small that near the Sun’s brightness it is extremely difficult to locate. However now we have a perfect “light-post” to guide us to the smallest planet. Just look for the largest planet! That would be Jupiter. It will be easy to spot before dawn because it will be the brightest object in the East. Look for it about 45 minutes to an hour before sunrise. You should be able to resolve a tiny pin dot of light on the left side of Jupiter if you have a sharp eye, without binoculars, but with a pair of binoculars it might be easier to see. Above and to the right of Jupiter will be Saturn.
Believe it or not the only time I have ever seen the smallest planet was back in 2016 when it passed in front of the Sun between the Sun and Earth, an event called a “transit”. As you can see Mercury is quite small! So perhaps tomorrow I might get to see it away from the Sun as a tiny pin dot of light. We will see. But don’t worry if you don’t see this post until a few days from now, you can still see the largest and the smallest planet in our solar system side by side. A very odd couple indeed!
The M81 galaxy group in the constellations Ursa Major and Camelopardalis contains Messier 81 (M81), the large spiral galaxy visible just to the left of center, Messier 82 (M82), the irregular galaxy to the right of M81, with the red glowing gas, also known as the “Cigar” galaxy for its shape, and many other galaxies, some of which are also visible here. NGC 3077 is the small but bright elliptical galaxy to the upper left. M82 is a prototypical “starburst” galaxy where an exceptionally high rate of star formation is taking place, and is thought to be triggered in this case by the gravitational interaction with M81.
This whole galaxy menagerie, about 12 million light years distant, is seen amidst a faint vast and complex network of interstellar gas and dust known as the Integrated Flux Nebula (IFN), a portion of which can be seen in the background of this image. Other significant visible features in this busy intergalactic field include the well known Arp’s loop (described by astronomer Halton Arp) which is an arcing faint loop of gas arising from the right side of M81 in this image, the top portion of which forms almost a heart shape. This structure is thought to be the result of gravitational interaction between M81 and M82. Finally there is the dwarf galaxy satellite of M81 called Holmberg IX, an irregular galaxy which is the small bluish patch of gas and small stars visible right above M81.
The full resolution version can be seen by clicking on the thumbnail under “My Astroimages” lower right on this page.
M81 and M82 are more closely connected with the constellation Ursa Major, The “Great Bear”, as you can see by the cartoon overlay in the image above. Note the Big Dipper (white circle), which is very near and dear to us northerners, is only a small part of Ursa Major. The bright Big Dipper stars make up just a portion of the Bear’s hindquarters. The galaxies M81 and M82 are bright enough to be detected in binoculars in the same field! A small telescope such as a 4″ refractor will definitely reveal their shapes. You can see here their location just to the left of the bright pointer stars in the front edge of Big Dipper’s pot (Merak and Dubhe). If you extend the line between those two stars and draw it straight like an arrow further to the left you will eventually arrive at Polaris, the North Star. This is why the two stars are referred to as the “pointer stars” because they “point” to Polaris. For Northern Hemisphere observers this is a good time of year going into the Spring to observe the galaxy pair. Now the Moon is basically full so it’s not a good time but go out in another week a couple of hours after sunset and look toward the north- northeast to find first the bright big dipper stars in the orientation above, then sweep over slightly to the left and up to find the galaxies.
Yesterday Perseverance, the latest in a long and successful line of NASA robotic solar system explorers, successfully landed on Mars! As a space and astronomy enthusiast it was necessary to take this time to acknowledge another extraordinary collaborative engineering feat. It cannot be overstated. The ability to engineer, launch and deploy a sophisticated robotic package 100+ million miles to another world is unfathomable! I remember the Viking mission of the mid 70’s. That probe I believe was about as large as a microwave and came to rest after bouncing around on air bags but after that it took amazing panoramic images especially for those days. They were the first images from another world beyond the Moon. The latest Mars explorer is light years ahead of that and also much more advanced than the last rover, Curiosity. Perseverance will have an autopilot to avoid obstacles and an autonomous navigation system to facilitate driving in hazardous terrain. On board, spectrometers and other instruments can analyze elemental composition of the surface. Perhaps the most interesting is the Mars Oxygen In-Situ Resource Utilization Experiment (MOXIE), a technology demonstration that will produce oxygen from Martian atmospheric carbon dioxide. If successful, MOXIE’s technology could be used by future astronauts on Mars to burn rocket fuel for returning to Earth! Two other technological points need mention. One is the presence of a drone helicopter on the rover. It will be possible to test for the first time ever, flight on another world! Finally Perseverance will have the capability of packaging rock and other samples and delivering them to a site on the planet where they will be later retrieved by another spacecraft for delivery back to Earth.
At any rate the details of the project mission are everywhere online and are easy to find. The main purpose of the mission is to explore the region surrounding the crater “Jezero” by the landing site and search for signs of ancient life. After all that’s the ultimate question we are all asking and want to know: Are we alone?
My wife and I watched the live NASA broadcast of the Mars landing. Despite the fact there was not the crowded mission control center as in the old Apollo days, the atmosphere at the Jet Propulsion Lab in Pasadena, California was just as intense and exciting. You could feel the intense anxiety of the mission scientists during the so-called “7 minutes of terror” beginning right after parachute deployment, when contact was interrupted, until landing. Then, when the signal from Perseverance came through, applause, cheering and uninhibited expression of triumph. Shortly after that, the first image of the surface of Mars appeared! It reminded me of astronaut re-entry into Earth’s atmosphere when many minutes of tension in the Mission Control room were relieved when the opening parachutes were spotted over the Pacific Ocean, bringing the crew safely back home! I remember back when I was young, going outdoors at night to observe the night sky and my dad would ask me what I was doing. After I told him he would say “Well son, if you see anyone waving back definitely let me know”. Perhaps now we will find evidence that maybe there was someone waving back from Mars long ago! We will see.
We discussed last time the maintenance routine on the Pier 1 mount, a Paramount MEII with on axis encoders. The final step was recollimation, pointing model creation and at last image testing! Recollimation I have covered in detail with an earlier post. Thankfully the Officina Stellare RiDK 400mm telescope is probably the easiest reflector in the world to collimate. No joke. A few tweaks on the 3 primary mirror screws is all it takes along with some software assistance as also discussed in the same referenced post. I was finally able to arrive at 1.5 arc sec collimation in average seeing, which I was very happy with! Accurate telescope pointing can be accomplished with several software applications and I won’t spend time on that now, just to mention that with the encoders the resulting pointing model is routinely single digit arc second accuracy, in this case 7. Before resuming any projects we need to retest telescope tracking without guiding just to be sure there is nothing wrong with the right ascension worm gear. To do this we use the main imaging camera to track a star for 10 minutes and make sure there are no abnormally large deflections occurring at exact regular intervals.
These logs remind me of EKGs since I am in the medical field. Of course if this were an actual EKG that would certainly indicate a life threatening situation! However for a telescope mount it is actually a good sign to see random deflections within an acceptable degree of error with no large spikes especially occurring at regular time intervals. If it did look more like a normal EKG then the mount would certainly have some major issues! The total error for 10 minutes was only 0.55 arc seconds which for very average seeing conditions I would say is quite good for an optical system of 2800mm focal length and no guiding.
Finally we test the unguided tracking on an actual star field and examine those results after 5 minutes. If the star quality is good i.e round stars with no trailing or egg shapes after 5 minutes then for sure we can guide effectively. The image at the very top of this page illustrates the visual result. I thought for an unguided image it was frankly beautiful! There was nothing special about this field other than there was a suitable star that could be used for tracking. It was very interesting though to check and see if there was anything in there of note.
Last step before resuming actual projects was to measure the stellar parameters in the test image and not just accept a biased visual appraisal 🙂
The key star image parameter “eccentricity” is shown for the test image as a value of just under 0.48. This is excellent especially for unguided operation! Eccentricity is a measure of the “roundness” of the star. Really anything 0.48 or less is outstanding. I have found it difficult to visually detect oblong stars until the eccentricity approaches 0.55. The other parameter FWHM or “full width at half maximum” is a reflection of the local atmospheric seeing conditions which in this case being average at best yields an expected result.
And now my friends it’s time to return to the universe again with the 400mm scope! I’ve started on 2 projects, both galaxies, which is really what this telescope is made for.
We’re going really into deep space with this one. The spiral galaxy NGC 1961, located in the constellation Camelopardis (The Giraffe), is 200 million light years from us but still shows some details in the distorted spiral structure. Thus far no companion galaxy or other evidence for a galactic merger has been confirmed. Xrays do show a large envelope of gas around the galaxy. It measures over 220,000 light years across so it is more than twice the size of our Milky Way Galaxy!
For the second imaging project we return to an old friend! In comparison to NGC 1961, M51, the Whirlpool Galaxy, is right next door at “only” 35 million light years distant. It is actually a pair of interacting galaxies NGC 5194 and 5195. Located in the constellation Canes Venatici (The Hunting Dogs) M51 is very close to the “handle” of the Big Dipper. It is by far the most photogenic of all the galaxies we can observe here in the Northern Hemisphere and it never gets old!
This image of M51 above was the very first tri-color guided image I ever took and it was back around this time in 2006. The fact that it was taken with M51 in almost exactly the same orientation as the current project is pure coincidence! This will make it easier to compare the two images when the current project is done.
In order to obtain the 2006 image I had modified my old classic 10″ f/7 newtonian reflector with a motorized focuser and custom mounting plate I had machined to fit on a Paramount ME (which I am still using today for the spectroscopy projects at the Talavera Space Hut). The camera back then was an SBIG ST8XME. The sensor was tiny by contemporary measures, less than 2 megapixels. The old newtonian which I had restored from the mid-1970s did a better than expected job in the new ccd era, but eventually with advances in technology I had to move on from it. This is a small hint regarding the topic of an upcoming post!
Well we did sign up for this! Building everything from the ground up, installation, calibration, collimation etc etc will also include regular maintenance and this time of year usually means one of the two mounts is due. This time it’s the Paramount MEII equatorial mount on Pier 1 at Orion’s Belt Remote Observatory, Mayhill NM. Step 1 involves reapplying fresh motor assembly grease to the gears on both the right ascension and declination axes. To do that you have to remove the worm blocks to access the gears, and in this particular mount, to remove the worm blocks you first have to detach the encoder cables from the control board! The on axis encoder cables are an additional feature for this mount. They make it possible to register the exact position of the gear angles when power is applied, eliminate the need for a separate homing sensor, eliminate periodic error in the mount and improve pointing and guiding. This is huge for a large optical system with a long focal length! The trade off of course is that you have to go through this kind of stressful routine every year and a half where the tiny cable terminals have to be removed from the control board and snaked through the cable jungle contained inside the mount and hope the 28 gauge wires don’t get damaged resulting in a very expensive mishap. My fingers are not exactly small and I really need to find a tool that can help maybe for next time. Great news is I did survive yet again for the third time!
Once the mount gears have been re-greased, the worm blocks are re-installed, then, of course, the tricky part is feeding the encoder cables back to the circuit board. To do that I first apply tape around the cable terminals and then tape a zip tie on top of that, feeding the zip tie back through the mount to the board. If you have to do anything like this I recommend what’s called Gaffers tape which is NOT electrical tape. The electrical tape is way too sticky and could easily damage the terminal wires when trying to pull it off. This tape sticks enough but is easily pulled off with no residue behind. The very top image shows the zip tie taped to the terminal and we have fed it back through the mount.
Step 2 in the routine maintenance, once everything on the mount is reassembled and we have briefly powered on to make sure the encoders are still working, is to rebalance the mount axes. I was slightly out of balance on the dec axis with the scope just a tad heavier on the camera side, but every small detail is important especially with a scope this size. I did not intend to try and push the whole telescope forward hopefully just enough to balance it since it weighs over a hundred pounds. I thought the best way would be to add a small amount of weight forward, possibly a light ankle weight or similar, but I really wanted to get it handled at the time so I could move forward and get the platform back to imaging again. I then thought of this:
I just happened to have a dovetail mount adaptor I was using for a portable refractor that I could slide onto the front of the top mounting plate on the telescope! All I needed to do was adjust the position until perfect balance was achieved and then tighten the knobs.
Ok we’re ready to clean everything up and continue on! Next up is collimation, setting up a pointing model, testing tracking and resuming our imaging projects. To be continued next time.
The latest from Orion’s Belt Remote Observatory, Mayhill NM for February 2021. As we discussed in an earlier post entitled “New Year’s Makeover”, the equipment on Pier 2 was changed.
This platform is ideally set up for wide field imaging. Our first target, one which I actually have never done despite it being an all time amateur favorite for Northern Hemisphere targets in winter is….
NGC 2244, the Rosette Nebula! The nebula is part of a giant molecular cloud in the constellation Monoceros, east of Orion. It’s a region of ionized atomic hydrogen which emits the brightest signal. The open cluster NGC 2244 lies at the center and those stars have formed within the nebula’s substance. Distance from Earth is about 5000 light years and diameter is 130 light years. This is another narrow band imaging project which is currently underway.
Of course with narrow band projects we are talking in addition to hydrogen, oxygen and sulfur which are also present in the nebula:
Stay tuned for the final S-H-O (Sulfur-Hydrogen-Oxygen) narrow band image of the Rosette nebula!
Observatory news for Pier 1 at Orion’s Belt will be covered next post.