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!
IC 1318, The Sadr Region, is the diffuse emission nebula surrounding Sadr (γ Cygni) at the center of Cygnus’s cross (left of center in this image). It contains many dark nebulae in addition to the emission diffuse nebulae. The brighter emission feature in the center with associated dark region is often referred to as the “Butterfly Nebula”. The intricate patterns in the bright gas and dark dust are caused by complex interactions between interstellar winds, radiation pressures, magnetic fields, and gravity.
The image was taken through the three narrow band filters Hydrogen alpha, Sulfur II and Oxygen III. Readers can refer to a detailed explanation of narrow band imaging I covered beginning in this post, the first of a 3-part series on the subject. Really the main issue with narrowband images is that the individual channels have to be “mapped” to the broadband channels Red, Green and Blue to yield a color image. In other words it is false color. It is usually described though as “mapped color” or “tone mapping” . That sounds like a really complex process but it’s really the wild west when it comes to this because you can make the colors anything you wish. Typically we amateurs use the “Hubble palette” which is derived from how the Hubble Space Telescope handles its’ images. The sulfur is mapped to red, hydrogen to green and oxygen to blue. The challenge arises with the hydrogen mapped to green because it is by far the strongest of the three in terms of signal. Therefore at first you have a bright green nebula which looks awful, but you can easily manipulate it to taste. After processing a few of these, this color palette kind of grows on you and you can begin to see how these colors can be manipulated and blended to yield a nice result.
Full resolution image can be viewed, as always, via the link on the right under “My astro-images”
IC 1318 is visible now in the northern hemisphere right as it gets dark. If you are in a dark enough sky to see the Milky Way, just trace the star cloud north to the “Northern Cross” which is the the central part of the constellation Cygnus the Swan. The brightest star there is Deneb, but the second brightest star which is quite bright at just over 2nd magnitude is gamma Cygni. This is the star at the right lower corner of that blue square in the image above. That is the location of the nebula! The nebulosity should be visible in small telescopes under a reasonably dark sky.
Just north of the Gila National Forest along the western edge of New Mexico lies the town called Pie Town. Its’ name comes from a bakery that specialized in dried apple pies back in the 1920’s. Today, continuing that “pie” tradition, it is still known for the popular Pie Town Annual Pie Festival held the second Saturday each September. While I certainly wouldn’t turn down a great homemade apple or cherry pie once in a while, my interest in the region is of course not about that, but about the fact that 15 years ago a couple of guys established the SkyPi Observatory and that gradually became one of the several telescope hosting sites in New Mexico. You could probably imagine that with a whopping census of under 200 people and sitting at an altitude of close to 8000 feet it might have potential for an observing site! Not to mention the famous Very Large Array radio telescope complex is very close by. That is a great sign if an outfit like the National Radio Astronomy Observatory found the area to be suitable for their observing needs!
I decided to pay a visit to Pie Town to see what their set-up was about. As I mentioned in previous posts, the seeing at my observatory is a challenge for my large telescope platform and after researching the various hosting sites, it appeared that the seeing at SkyPi, in particular, was consistently almost a full arc second better.
The drive from my home is not bad at all. If you live out here, driving 3-4 hours is nothing. Interestingly Pie Town is about the same distance from my house as it is from my remote observatory in Mayhill (image above).
It was a fantastic crystal-clear day with just some high thin clouds when I made the trip. I drove north on I-25 and got off at the Socorro exit after about 2 hours. Heading west on highway 60 I went through the town of Magdalena and right after entered the Plains of San Agustin. This is a flat stretch of desert far away from everything! The plains are ringed by mountains which kind of looked like a natural fortress of rock. It was really a majestic view while driving through there.
After another 20 minutes or so I looked toward the south and suddenly the iconic Y configuration of VLA’s telescopes came into view! It was much bigger than I imagined. Of course, I stopped at the lookout point to take these images. Unfortunately, the visitor center is still closed due to COVID 19. The Very Large Array is a collection of 28 radio telescopes, each about 25 meters in diameter, arranged in a Y shape along rails. That allows for 3 long arms of 9 telescopes each with one at center. Their position can be adjusted as needed. The VLA is one of the most active radio astronomy observatories in the world!
From there it was not far to my ultimate destination. After about an hour I drove into Pie Town, but there was not much of a town. A welcome center and general store was all I could see. The SkyPi facility was only about a mile from there, take a right onto a dirt road up a series of hills and I had arrived!
SkyPi is a very modest sized facility. It is run basically by two guys, the owner and the “technical expert” with the help of the owner’s daughter. The owner was off site so I had scheduled a meeting with Michael who was the one in charge of keeping the roll-off observatories running smoothly. They host about 10 telescopes currently, so not many, but plenty for the staffing that they have. Unfortunately for me they had just rented out their last available pier, but they are planning to expand once they have the necessary help. Michael told me that he and the owner John are “just getting too old for this sort of thing”. I could understand that. There is quite a bit that goes into running these types of facilities. I have enough to deal with just two telescopes let alone 10 or more!
I got the grand tour of the facility, the roll-offs and the equipment they were hosting as well as a couple of visual observing decks used for Dobsonian telescopes. There was also a privately owned 40” Dobsonian housed in a large roll-off at the bottom of the hill, and an observing site that was used for star parties where they had a few cement piers with power for anyone doing portable imaging.
After the tour we sat out on the deck of the main house which is where the two of them stay. There is a guest room for anyone needing to spend the night setting up equipment, etc. I had a great afternoon there with Michael. I had come there with a huge list of questions regarding setting up, operating logistics and other technical matters, but I could see that my host was a little weary probably from the previous night and since they didn’t have any available piers anyway, I decided to let the conversation just flow naturally. We talked about the community and the astronomers who lived there. It turns out they are going to host the Magdalena Astronomy Club’s annual Enchanted Skies star party which is in October.
It can get pretty cold up there in Pie Town. He called it “Canadian cold”. I certainly know what that is! The conversation then moved into music and electric guitars. They had a couple of instruments in the main house. It turns out John, the owner, is a bassist and Michael plays guitar. I told Michael next time I came out I could bring my own Fender Stratocaster which I play periodically. The afternoon wrapped up with a discussion of UFOs! All in all, a most enjoyable afternoon! The VLA, SkyPI Observatory and some very stimulating conversation all in one day. Perhaps the window for equipment moving has closed at least for now, but I have a place I can go for jam sessions and spectacular dark sky observing!
Located in Tucson, AZ in the US, the International Dark Sky Association (IDA) was incorporated in 1988 for the purpose of “preserving and protecting the night time environment and our heritage of dark skies through quality outdoor lighting.” It does this via many education and public outreach strategies as well as partnering with local businesses and municipalities. Despite the fact that the scourge of light pollution does not seem to be going away any time soon, the good news is the IDA remains the recognized authority on worldwide light pollution and the leading organization combating it. It has an International Dark Sky Places program that aims “to encourage communities, parks and protected areas around the world to preserve and protect dark sites through responsible lighting policies and public education”.
There are currently five types of designation (see below) for International Dark Sky Places which the IDA “awards” to those regions which have accomplished the goal of developing, preserving and protecting the night sky. While I am well familiar with the IDA (since I am only four hours away from their main headquarters!), I was not familiar with the specific categories of Dark Sky Places, and in fact did not know there were more than one!
The following information is courtesy of darksky.org, the IDA’s website:
International Dark Sky Sanctuaries- These are the most remote (and often darkest) places in the world whose conservation state is most fragile. A sanctuary differs from a Dark Sky Park or Reserve in that it is typically situated in a very remote location with few (if any) nearby threats to the quality of its dark night skies and it does not otherwise meet the requirements for designation as a park or reserve. The typical geographic isolation of Dark Sky Sanctuaries significantly limits opportunities for public outreach, so a sanctuary designation is specifically designed to increase awareness of these fragile sites and promote their long-term conservation. I am happy to point out that there is one Dark Sky Sanctuary located right here in New Mexico that is only about a three hour drive from here! It’s appropriately named the “cosmic campground” and is located in the Gila National Forest which is in the western part of the state.
International Dark Sky Reserves- Reserves consist of a dark “core” zone surrounded by a populated periphery where policy controls are enacted to protect the darkness of the core.
International Dark Sky Parks- Parks are publicly- or privately-owned spaces protected for natural conservation that implement good outdoor lighting and provide dark sky programs for visitors.
International Dark Sky Communities- Communities are legally organized cities and towns that adopt quality outdoor lighting ordinances and undertake efforts to educate residents about the importance of dark skies.
Urban Night Sky Places (seems like on oxymoron to me, but it is a legitimate designation!)- UNSPs are sites near or surrounded by large urban environs whose planning and design actively promote an authentic nighttime experience in the midst of significant artificial light at night, and that otherwise do not qualify for designation within any other International Dark Sky Places category.
And now the envelope please for the Dark Sky Designation recent winners!
The latest from Orion’s Belt Remote Observatory in Mayhill, NM includes this narrowband project just completed on IC 1318. This is a fairly large and rich emission and dark nebula region surrounding the bright 2nd magnitude star Gamma Cygni at the center of the “Northern Cross” (brightest star in the image). The region is often referred to as the “Sadr Region” referring to the proper name of the star gamma Cygni . IC 1318 is also known as the “Butterfly Nebula”. It is a fascinating region of the Milky Way and I look forward to the fully processed result which I hope to have within the next couple weeks.
IC 1318 was taken with this platform shown above including an FSQ106N, SBIG STXL 16200 camera and Paramount MX+ mount. No sooner had I completed the OIII channel when the filter wheel sensor failed and had to be sent off for repairs. Luckily I am not missing anything soon because the weather has turned for the worse and we are anticipating our “Monsoon Season” to start up in July. Typically during that time there are frequent thunderstorms but generally off and on so you might get a window of good viewing here and there!
Pier 1 has been very quiet unfortunately. The combination of bad weather and bad seeing has rendered this platform barely usable to be honest. I have been at this location for 3 1/2 years and the seeing just isn’t consistently good enough to support this platform. The 16″ scope has a focal length of 2800mm. The local seeing here is average. It’s plenty dark enough yes, but for long focal length optics that’s not going to be enough. I have looked at these seeing monitors here in this astronomy community forever and I’m going to say it’s about 2.5 arc sec average over the year. That’s a tough ask for anything with over perhaps 1500 to 2000mm FL. In contrast my equipment on Pier 2 is only 5-600mm and it doesn’t care what the seeing is. My solution will be to move this scope to a telescope hosting site about 3+ hours from here where the average seeing is close to a full arc sec better. That would be a town called Pie Town, New Mexico located in the far western part of the state and also further north (more on Pie Town in a future post). I will then install most likely an imaging newtonian on Pier 1 with a focal length of only about 1300mm. That should be compatible I would think with the local conditions here. Hopefully all of this happens in the next year or two. In the meantime I will try to finish a couple more projects here on the 16″, weather permitting.
That’s about it for now from Orion’s Belt Remote Observatory.
Deconvolution is one of the most confusing and poorly understood algorithms in all of image processing. Most of the time I think people get frustrated with the bad results in terms of image artifacts that they just forget about it altogether. While it is true for sure that it doesn’t always help and for lower resolution wide field images it probably isn’t applicable, I think it is a mistake to avoid it entirely. You may have a great data set for it and that is really the time in the workflow to address distortion issues.
Before getting into this further just a word about image “enhancement” in general. I am certainly no expert but have been doing this long enough to realize that when it comes to image processing I am a firm believer in a “less is more” approach. I see so many folks trying desperately to create a great image from bad data and that just isn’t possible. All you get from that is overprocessed bad data. However I have sadly also seen overprocessing of good, even superb data. This is the worst combination of all. When you have excellent data you really do not have to do much at all. Just let the data “breathe” and preserve the natural beauty of the object. Don’t crush the life out of it with all kinds of sharpening tools, artificial intelligence apps etc.
The above image is a full resolution sample from a superb data set of Omega Centauri, that from an amateur hosting facility in Chile. You can see especially when you click on the image the stars are peppered with a myriad of processing artifacts, in essence destroyed by overzealous application of sharpening and other enhancement tools.
What is deconvolution? This is a class of algorithms that attempts to correct for atmospheric distortion. It’s kind of a focusing algorithm. It technically is not “sharpening” but the effect is essentially similar. It cannot create resolution in an image that isn’t there, meaning if you examine a raw image at full resolution and your galaxy dust lane is lacking detail, it’s not going to add detail in there but it can certainly decrease the distortion of the detail that is present. To accomplish this the average point spread function or PSF of the stars in your image is determined so that the overall degradation of the entire image can be measured. This can only be applied to an image that has not been stretched yet and is still in the “linear” stage. When an image is linear the brightness value of every pixel is proportional to the photons received at the sensor’s corresponding pixel. Any “sharpening”, focusing etc you can do at this stage will be far better than after the image is stretched which is why when deconvolution works it is a great tool.
This is the case of the “Needle Galaxy” I recently processed where deconvolution was applied with great success which is why I decided to post this. Now I am using the program Pixinsight for this which is very popular but certainly not the only option out there. That’s ok because I still think you can see the approach and basic ideas which will be similar for other applications.
The basic plan let’s say for a galaxy is to enhance the galaxy’s features and perhaps tighten the stars without creating star or background artifacts. So we have to protect the stars and background from “collateral damage”. The workflow in Pixinsight is: 1) Create a star mask to protect stars 2) Create a mask to protect the background, in this case what is called a luminance mask 3) Create a point spread function or PSF so the entire image can be modeled 4) Apply the deconvolution process, adjusting a couple of variables to create the desired result
In Pixinsight you can apply “star mask” to your linear image to produce good star protection of the brighter stars during deconvolution. Just use the default settings for this purpose. You don’t have to change any parameters.
You then want to make the star protection more efficient by brightening the stars, increasing the contrast. I use the “auto clip highlights” button in the histogram transformation process to do this. This mask is not going to be applied directly to the image but will be used as a reference image for the process.
Next step is to create a mask to protect the background by first making a copy (steps shown above), then applying a permanent stretch to the copy to make it non-linear
The PSFImage script is able to create the PSF for image modeling as shown above
Open the PSF script, click on “evaluate”, wait until it’s done, and then click the “create” button to the right of it to produce the PSF which is basically a star image.
The PSF is shown above. The deconvolution process will use this file to model the whole image.
When you open the deconvolution process you’re going to click on “external PSF” at the top and select the PSF file in the drop down when it pops up.
The steps above show how to configure deconvolution to minimize artifacts. The star “support” mask is not directly applied to the image but the software refers to it internally to get the info it needs to carry out the “masking”. The other settings are left as default, so under “algorithm” you should see Regularized Richardson-Lucy selected. The other option is Van Crittert which we typically do not use for deep space images but is better suited for planetary images. Deconvolution is a wavelet based algorithm so “wavelet regularization” should be checked. I have not found adding additional layers beyond the default of 2 to be of any additional benefit. Also note the default iteration value of 10. This is a good starting test point. Typically I might do 15-25 for the finished product but not more.
Last thing to do before actually starting is to protect the background. This is a mask directly applied to the image so we take our stretched copy that we made earlier and apply it as shown above to mask the background. Remember this is a stretched non-linear copy applied to the linear original image. A linear mask will not be effective. I have not typically made any adjustments to this with histogram transformation etc. Just apply as is.
Now we are ready to begin deconvolution, but first we notice that the temporary screen stretch applied to the original image is a little overstretched as you can see in the right side image. We want to be able to clearly see the effects of what we are doing. You can dial it down a tad in the screen transfer function shown at the top (white circle) until you get a level that you are comfortable with just by moving the midtone and black point sliders and arrive at the result on the left. Remember this is NOT a permanent change and the image is still linear. This is just a way to see what you need to see.
Next step is to finally run deconvolution! At this point it is really about experimentation. Always select a small preview of an area of interest (Alt-N keys in Pixinsight). This will make the process much faster when you are testing your settings. The only setting you are going to change is “Global dark” at first. I start around 0.01. If you get the so-called “racoon eyes” around stars your setting is too low. If you get ugly bright artifacts in multiple areas your setting is too high. Once you have a result you are happy with you can increase iterations until you see problems. Remember it is very tempting to overdo it . If you get a nice result with lets say 15 iterations, doing 30 or more is likely to create a problem that you may not necessarily detect until much further in the processing flow when it will be much harder to correct. Quit while you’re ahead!
And the final result is shown above! Before deconvolution is on the left and after is on the right. I think the key is producing a good star support mask and background protection with the stretched luminance copy, dialing in the correct global dark setting and not going too crazy. Remember less is more!
And finally it’s nice to be able to quantitate what improvements we made and these are shown above. Deconvolution reduced the average FWHM by close to 1.5 arc sec which is the most I have ever seen doing this! Typically it’s around maybe 0.5 to not more than 1.
Anyway quite a bit to unpack here in this post! I hope at the very least you can get a sense of how deconvolution can work when it does work.
Sh2-155 or Sharpless 155 is a diffuse nebula in the constellation Cepheus, within a larger nebula complex containing emission, reflection, and dark nebulosity. It is widely known as the Cave Nebula, presumably derived from photographic images showing a curved arc of emission nebulosity corresponding to a cave mouth (roughly center of the image). Sh2-155 is an ionized H II region with ongoing star formation activity, at an estimated distance of 725 parsecs (2400 light-years) from Earth. (Courtesy Wikipedia)
The original “Sharpless” catalog was created by Stewart Sharpless in 1953 when he was on the observatory staff at the US Naval Observatory in Flagstaff, Arizona. He surveyed HII regions in the Milky Way which are regions of ionized hydrogen gas. A second catalog edition appeared in 1959 which contains some southern hemisphere objects but most are above around -30 declination.
Sh2-155 lies at the edge of the Cepheus B cloud (part of the Cepheus molecular cloud), and is ionized by young stars in the region. The energy from these stars is absorbed by electrons within the hydrogen gas and when these electrons release this energy, the result is emission of discrete wavelengths of light.
Hydrogen gas emits predominantly red light in the visible spectrum but there is also a component of blue and ultraviolet. Hydrogen alpha emission is what we are all used to seeing in deep space nebula images, namely the deep red corresponding to 6563 angstroms. However emission also occurs at shorter wavelengths, particularly H beta which is around 4860 angstroms. This is an aqua color which is actually fairly close to the emission line of doubly ionized oxygen or OIII, and also fairly weak compared to the H alpha line .
This is why we don’t apply hydrogen beta filters to our imaging because there is very little signal to be gained. However what we can do, since we are using a narrow band hydrogen alpha filter and that signal is quite strong, is to borrow some of it and apply it to the blue channel we obtain through the broad band blue filter, thus “simulating” H beta in the image. In this image I applied maybe 7% to blue. The net result is a slight pinkish hue in certain areas. Mind you there is no scientific basis to this per centage! It is simply “dialed in to taste”, meaning personal taste 😊. If you like more purple in the image or none, just increase or decrease the per centage accordingly. No law against that!
The full resolution image can be seen as usual by clicking on the thumbnail at lower right under “My astroimages”
The “real” Space Needle in my opinion is not the iconic observation tower in Seattle Washington shown below but is the galaxy NGC 4565 pictured above!
NGC 4565 , the “Needle” Galaxy is an edge on spiral galaxy 40 million light years away in the constellation Coma Berenices. The narrow profile, less than two arc minutes in width gives the galaxy its’ needle-like appearance. Other galaxies appear in the field as well, the brightest being the barred spiral NGC 4562 in the upper right.
For the full resolution version see the thumbnail link on the lower right panel of this page
NGC 4565 is one of the brightest members of the Coma I Group located about 47+ million light years away in the constellation Coma Berenices. The brightest member of the group is NGC 4725. The Coma I Group is rich in spiral galaxies while containing few elliptical and lenticular galaxies. Coma Berenices means “Berenice’s Hair” in Latin and refers to Queen Berenice II of Egypt, who sacrificed her long hair as a religious offering.
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!