 I have used a wide variety of equipment during my 15 years of Electronically Assisted Astronomy (EAA). This includes refractors, SCTs and even a Newtonian along with all sorts of analog video cameras and CMOS digital cameras. I have also tried many different live stacking software packages including ASI Live, TSX Live Stack and, mostly, Sharpcap. In every case, like so many others doing EAA, I had to pull together all of the necessary components including mount, OTA, camera, laptop and mini-pc, USB and power hubs, cables and SW and integrate all of these to make sure that everything worked seamlessly, which was often not the case. So, I watched with interest over the past 4-5 years as all-in-one Smart Telescopes began to hit the market. With a price point of $499 ($450 on sale) I finally decided to give one a try and purchased the ZWO Seestar S50 Smart Telescope. I have used it extensively in my light polluted back yard over many nights and even tried it out at our club's local dark site to see what it can do. In this Blog I will provide the basic run down of the Seestar's equipment, explain what you need to know to get it working, share some of my images and list what I think are its Pros and Cons.  Seestar's Design The Seestar S50 uses a 50mm f/5, 250mm focal length triplet objective with one element of ED (extra low dispersion) glass. The combination of 3 elements in the objective enables it to focus the red, green and blue light at the same focal plane. Therefore it does not show any hint of chromatic aberration, a purple color fringe around any bright object, which is typical with an objective using only one or two glass elements. In addition, because all three colors focus at the same focal plane the resulting images are sharp with good detail limited by the local seeing conditions. Light from the objective is directed off a pair of mirrors to an internal CMOS camera using the Sony IMX462 color sensor. This sensor has just over 2MPixels arranged in an 1080 x 1920 array of 2.9microns size pixels. As such the overall sensor is is very small with a diameter of just 6.46mm, quite similar the the IMX224 color sensor which first came out around 2014. The small size of the sensor combined with the 250mm focal length of the optics produces a small field of view of 76.5 x 43 arc minutes. While this is large enough to fit the entire image of the sun or moon, it is too small to fit the entirety of large deeps sky objects (DSOs) like the Andromeda galaxy. I normally do not recommend a small sensor like this as it also can make it difficult to find dim DSOs because of the small field of view. However, the Seestar has solved both of these problems for us. First, it has the option to capture images as mosaics up to 2X in width and height of the imaging sensor. With a 2X mosaic the Seestar can now fit the entirety of the Andromeda galaxy and many other large DSOs into one image. Second, the Seestar using Plate Solving to find and locate objects in the night sky. This means that when it goes to a point in the sky where it thinks the object you want is located, it takes an image, calculates the relative positions of the stars in the image, compares the result to a data base, determines accurately where it is actually pointing and commands the mount to move to the right location to center the desired object. So with both of these clever features you are not overly limited by the small size of its imaging sensor.  Focusing is accomplished with an internal focus motor which moves the sensor in and out to achieve focus automatically by measuring and minimizing the size of the stars measured in pixels. There is an option to perform focus manually but in my experience the Seestar's automatic focus routine does a very good job of achieving sharp focus. The Seestar has 3 filters and a shutter. The shutter blocks all incoming light so that the Seestar can take dark frames. It automatically creates a master dark frame from 5 individual dark sub-frames which are subtracted from each light frame to minimize the impact of sensor fixed pattern noise such as hot and warm pixels, as well as, sensor dark current. The first filter is an internal UV-IR cut filter which is designed to eliminate star bloat so that images have sharp stars. Seestar automatically deploys this filter on all objects other than emission nebulae. The second internal filter is a Dual Band filter designed to block all light except for that around a 30nm band at the wavelength of OIII and a 20nm band at the wavelength of Ha. This filter will block a large amount of ambient light pollution should be used for emission nebula, not reflection nebula, which have lots of light at these two wavelengths. Th Seestar will automatically place the correct filter in front of the sensor depending upon the object type. The Seestar comes with an external white light filter which must always be placed in front of the lens when there is a chance that sunlight might be directed into the Seestar. If sunlight reaches the imaging sensor without this filter it is highly possible that the sensor will be irreparably damaged. The Seestar is an Alt-Az mount which means that it has two rotation axes, one in the plane of the horizon and one perpendicular in altitude. Alt-Az mounts are commonly used for EAA and do not track the earth's rotation like an Equatorial mount does. While an Alt-Az mount will keep a point object like a star centered in the field of view, stars away from the center and any portion of a deep sky object like a galaxy or nebula not in the center of the field of view will slowly rotate about the center as the earth rotates on its axis. For this reason, the basic rule of thumb is to limit exposures to no more than 30sec to avoid having the stars appear to rotate about the center at longer exposures, looking elongated or trailed instead of point like. For this reason, the Seestar has a maximum exposure of 30sec.  The Seestar has an internal computer with 64GB of internal storage which automatically controls all of the hardware and software functions necessary for imaging. It can be accessed through its own WiFi via the Seestar App on your phone or tablet. The Seestar can be connected to a PC with the include Type C USB cable to download images stored in the Seestar's internal memory and recharge the internal battery. However, the Seestar cannot be controlled by a pc. All of the Seestar's function must be accessed through a smart phone or tablet using the Seestar app. The Seestar also has BT which is required for initial setup. The Seestar has an internal 6Ah internal battery which can be re-charged through a USB-C port on the side of the Seestar. You can also connect an external 12V power supply through this USB-C port to power the Seestar longer than the internal battery alone can do. All of these components are sealed inside a 5.5lb (2.5kg) plastic enclosure measuring 5.6" x 5.1" x 10.1" making it a truly light weight and compact Smart Telescope. The Seestar comes with a short but very sturdy tripod with a minimum height of 10.8" and a maximum height of 14.3" which screws onto the bottom of the Seestar with a 3/8" screw. Everything fits neatly inside a sturdy foam carrying case making this truly an all-in-one astronomy solution. As such, the Seestar is by far the most compact and travel friendly of any of the EAA setups I have ever used. It certainly would be very easy to bring as a carry on when traveling by airplane.  Initial Setup Connecting to the Seestar for the first time requires a few steps than are needed one time only and the process is well documented in the included instruction sheet. The basic steps include downloading the Seestar App to your phone or tablet, turning on the Seestar's power button (push once, wait, push a second time until you hear the beep) and connecting to it with the Seestar's WiFi. The first time also requires access to the internet but that is not needed for subsequent connections. For all future startups just turn on the Seestar (hold down the power button until you hear the beep), open the App and click on the red Connect button and follow the prompts to complete the connection. When connected you will see the screen below which is the main Seestar App screen, or Home Page, from which you can Open the Seestar arm, enter one of 3 observing modes, view images stored on you phone/tablet or the Seestar's internal drive, view a wealth of video tutorials to get you going, view local weather information and more. You can also see the serial number for you Seestar unit and the current battery state of charge at the top. I encourage you to start by viewing each of the well done tutorials so that you thoroughly understand what how everything works.   Compass & Level Calibration The next step with a new Seestar is to calibrate the internal compass and the level sensor. The Compass Calibration and Level Sensor Calibration procedures will ensure that the Seestar will be able to easily and accurately find and center targets in its field of view. In fact, the Compass Calibration is essential for finding the Sun or the moon during the day as the Seestar will not be able to use its Plate Solve procedure to find either without any visible stars. If you have ever used a Celestron Nexstar or Skywatcher Alt-Az mount you know that the initial setup calls for leveling the optical tube and pointing it north. This is called "Level North" and allows the mount to make a good estimate of the location of objects in the sky using that information along with the local time, latitude and longitude. With this the mount can put the first alignment star close to, if not in, the field of view. Similarly the Seestar compass calibration enables the Seestar to determine the direction for north and the level sensor calibration will allow it to provide feedback to the user when performing the Level Sensor procedure each time the Seestar is set up for an observing session. Hence, Seestar will be able to GoTo the first object and place it in or very near the field of view as well. The difference between the calibration procedures and Level North is that the former only needs to be done once while the later must be done any time the telescope is moved to a new location. To do the calibration and leveling tap the image of the Seestar in the upper left corner of the Home Page to get the next page. Here you have more information about your Seestar along with options to adjust the Sound, the ability to manually adjust the focus, On/Off switches for the dew heater and a Watermark which writes the name of the object imaged along with the exposure time and your location at the bottom of the jpeg images produced after stacking. At the very bottom is a slider to turn off the Seestar power. Just above this is the "Advanced Feature" bar. Tap this to get to the Advanced Feature page where the calibration options can be found. Clicking on the Compass Calibration will display a short video which will guide you through the process. The procedure involves rotating the Seestar about its vertical axis while watching feedback of a white circular ring which slowly turns to green as the calibration is complete. Next, watch the Level Sensor Calibration video which you can find on the App's main page and then then press and perform the level calibration. This involves placing the Seestar on a level surface with a small bubble level on the base of the Seestar, then using thin sheets of paper or similar underneath the edges of the Seestar until the bubble is centered indicating it is level. Once leveled press Calibrate in the App to confirm calibration. This tells the Seestar internal level sensor what true level is so that it can provide feedback to the user when performing the Adjust Level procedure before each session. Again, this sensor calibration procedure only needs to be done once and is not to be confused with the Adjust Level procedure which should be done every time you set up the Seestar. If, at some point while imaging you are having great difficulty getting the Seestar to find and center objects, or it is dropping too many images instead of stacking them you may want to go back and repeat these two calibrations as any degradation in either can impact performance.   On this same page of the App as the Compass and Level Calibration procedures you will find several other important features. At the top you can set the exposure to one of the three possible times. Below that you can tell Seestar to save all of the individual frames as FITS files along with the stacked JPEG image which you may want if you plan to do your own post processing to enhance the final image. The Initialization button takes you to another page where you can turn off the Horizontal Calibration and/or the Auto Focus routine. I suggest you leave these turned on. The Horizontal Calibration routine is on by default and is designed to improve the pointing and guiding accuracy of the Seestar. When the Seestar goes to the first object it will take a short exposure image and perform a Plate Solve operation to use the star positions to get an accurate measurement of the RA and Dec at the center of the current field of view. It will then slew 15 deg in Azimuth to the east and repeat the Plate Solve operation and slew 15 degrees in Azimuth to the west to repeat the process. With 3 Plate Solve solutions the Seestar will update its pointing model and then center the desired object. With the Horizontal Calibration routine turned off, the Seestar has to rely on its compass and level only to find the desired object. With Auto Focus turned on (default setting), the Seestar will automatically perform a focus routine when it goes to the first object after being turned on. The focus routine works very well and I have not found the need to do a manual focus. But, if you want to you can enter the manual focus routine on the previous page and set the focus position manually to try and improve the focus. It should also be noted that it is a good idea to force the Seestar to do an auto focus as the temperature cools down during the night. Some people like to focus for each new deep sky object. To do that use the focus button on the right of the screen during a Live View (see later). Take note of the Adjust Level button on this page as we will need to use this each time we set up the Seestar for a viewing session. Nightly Setup Procedure A typical viewing session begins by placing the Seestar outside on its tripod on a relatively level surface free from vibrations and wind, both of which can be a cause for poor star images resulting in failures in the stacking process. Keep the Seestar as low to the ground as possible for better stability, but if you must elevate it to see over obstacles use a sturdy tripod. The tripod from a telescope you already own is a very good option, although it will not be as light weight and compact as a camera tripod you can purchase on Amazon. An extremely helpful optional accessory is a 3 point tripod leveling base which fits between the Seestar and the tripod. It is much easier to level the Seestar using the three leveling knobs on this than trying to adjust the height of the three tripod legs. But either method will work. Next, power on the Seestar, open the App and Open the Seestar arm. Go to the page shown below to perform the Adjust Level operation which can be reached from the Advanced Feature page by clicking on the Calibrate button. The Adjust Level operation should be performed each time the Seestar is moved to ensure that it set up in a level position which helps improve the accuracy of the initial GoTo procedure. Pressing on the Adjust Level button brings up the following screen which provides feedback to help achieve the optimum level. As you adjust the level two Green Circles will either overlap more or less depending upon whether you are improving the level or not. Adjust the leveling knobs until you have the best overlap you can get, typically a number less than or equal to 0.3 should not be difficult to get and should provide satisfactory results. Once leveled you can set the exposure time and indicate whether you want to save each individual frame as a FITS file for subsequent post process or not and then go back to the Apps main page to select your target for live stacking. Be aware that longer sub-exposure times will likely result in more dropped frames due to star trailing, especially when pointed at Altitudes greater than or equal to 75 degrees, as well as, to Azimuth angles close to 0 and 180 degrees as these are the locations where field rotation is maximum.   Routine Operation Once the setup procedure has been completed it is time to pick a target. For best results, try to stick with objects which will be between 30 and 70 degrees altitude for the duration of imaging. Objects higher than 70 degrees will begin to exhibit greater field rotation which will result in more rejected frames. Objects below 30 degrees are viewed through a great deal of atmosphere which can make for more distortions and also rejected frames. All-in-all the Seestar requires overhead to analyze each sub-frame and decide to accept or reject it, stack the image and dither the mount discussed later) which amounts to as much as 25% of the total imaging time. So, expect to be able to stack no more than 15 min of exposures in 20 min if the Seestar tracks perfectly, the skies are perfectly clear and steady, there is not wind, etc. More often than not we do not have these ideal conditions so expect stacking efficiencies as low as 40% with 75% as a maximum when measured as total stack time divided by actual time elapsed. The Stargazing and Solar System pages provide lots of helpful information to guide you in selecting deep sky or solar system targets, respectively. If you tap on Stargazing it will bring you to another page which displays some of Tonight's Best deep sky and solar system objects which are visible that night. You will also find Tabs for specific Deep Sky Objects such as Galaxies, Nebulae, Star Clusters, etc along with a Solar System tab. Selecting one of Tonight's Best or one of the Solar System objects opens another page which gives detailed background astronomical information about the object. Selecting Galaxy, Nebula, etc under Deep Sky takes you to a list of those objects. If you click on the "GoTo" icon to the right the Seestar will immediately go to that object. If, instead you click on the name of one of the objects you will go to a page with details about that particular object, including a plot of its Altitude over time which is helpful for deciding when it is best to view the object. At the bottom of this page is the red Go Gazing button which will direct Seestar to GoTo the object. If you do not see the object you want you can type the name or astronomical designation in the search at the top of the page. Or, tap the red Skip bar at the bottom of the page to go directly to the imaging page. The Seestar App also has a nice Sky Atlas which can be entered by pressing on the "SkyAtlas" icon on the bottom of the Home Page. This works like a typical Sky Atlas program with buttons on the right column to find "Objects", turn on the "Compass" to allow the view of the sky to rotate as you phone/tablet does, a "Grid" button to turn On/Off the sky grid, a "Ground" button to show where the horizon is, and a "Framing" button to set up the Mosaic feature which we will discuss later.  Now here is where the Seestar takes makes EAA really easy. Once you tell Seestar to go the object you selected, it slews to the point in the sky it thinks the object should be located. It is able to get close to the object because the compass calibration lets it know where true north is positioned and because it has been leveled. Most likely it will not have the object centered in the field of view, but in most cases it should be visible unless the object is very dim. Now, the Seestar will automatically go through its Horizontal Calibration process where it takes an image at the GoTo location, rotates the mount 15 degrees in one Azimuth direction to take another image and 15 degrees in the other Azimuth direction to take another image. Seestar then plate solves all three images refining its model of the sky so that it can next move the mount to the correct location to center the desired object in the field of view. In my experience, Seestar does an outstanding job in this regards. If you have trouble with this operation, check your level. If you still have trouble you many want to redo your compass calibration and your level training. After it centers the object it will perform the "image enhancement" which means that it takes 5 ten second dark frames and combines them into a single Dark Master which it will seamlessly subtract from all individual light frames to remove the fixed pattern background noise. Next the Seestar performs an automatic focus and then it begins the image capture and stacking. The Horizontal Calibration and Focus routines are only performed on the first object viewed. You can force a focus any time you want by using the focus button on the right column of the live view screen. Prior to beginning the image sequence, Seestar will place either the internal Dual Narrow Band or UV-IR filter in front of the sensor depending whether the object is an emission nebula or not. The former is only useful for emission nebula, while the later is useful to minimize star bloat. The user has the option to tap the filter Icon in the upper right side of the screen to move the Dual NB filter in or out. If it moves the NB filter out the UV-IR filter will replace it.  The image above shows the imaging page which appears after selecting GoTo for any target. A preview of the image will appear in the center. On the right are buttons to turn On/Off the Filter, Adjust screen brightness, Mark, force an Auto Focus and go to the Sky Chart. The red button at the bottom turns On/Off the exposure. Pressing it will begin an exposure and the live stacking process. Tapping the small white circle in the center of the screen will bring up the Joy Stick button shown in the image above which provides the ability to move the mount left/right or up/down to change the position of the object in the field of view. The Sky Chart button takes you to the a celestial chart which shows the field of view overlaid on the chart along with identification of key objects on the chart. You can use the Sky Chart to move the mount around to different locations in the sky as an alternative way to move to different objects in the sky or to fine tune the image in the field of view. Live Stacking
Once the live stacking process has begun, the Seestar will take successive exposures according to the time set (10s, 20s, 30s) and continue to stack them until you hit the red imaging button at the bottom of the screen. Once you tap that button Seestar will save a jpeg file to you phone or tablet of the stacked image and save a Fits image of the same to the Seestar memory. If you tap the red imaging button again you can continue to build up the image or stop and start of new image of the same target or go back in the App and find a new target. A countdown timer appears at the bottom of the screen during the imaging process counting down the individual exposure time. As successive images are added to the stack the timer in the upper right will add to the total stacked time. When an image is deemed not acceptable to stack by the internal software either because of star trailing or other poor quality the stack timer will not be advanced for that frame. Typical stacking acceptance rates vary from roughly 40% on up and are impacted by the object's altitude, azimuth, the seeing conditions, high thin clouds, wind or any other sources of vibration. The higher the altitude the more likely to loose frames due to the effect of field rotation so most users stay between 30 and 75 degrees in altitude to get the best stacking efficiency. The Seestar also has an automatic feature called dithering which is used to minimize the impact of fixed pattern noise. After every 5th frame the Seestar will move so that the image is shifted by ~30 pixels in the frame to shift the fixed pattern noise around so that it is averaged out in the final stacked image. This dithering takes time along with the internal stacking of the frames so that there is an overhead of ~20 to 25% of the total time. Hence, even if you were to achieve 100% stacking success, you will still only get 45min of stacked image in a total time of 1 hour. Seestar Pros and Cons Based upon my experience with the Seestar and many other scopes over the years, I would call the Seestar the simplest scope to begin obtaining dramatic images of deep sky objects in your first night with it with no prior experience required. It is truly as simple as setting down, leveling, connecting the App and telling the Seestar to go to whatever object you want to image. It is light weight and compact making it amazingly portable and quote practical to take on an air plane. And the cost, at $499, is at least 1/3 of what it would cost to put a similar setup together on your own. The other nice thing about the Seestar is that ZWO continues to update the software to add new features and improve upon the existing ones. Recently they introduced the Plan Mode which allows us to set up an imaging plan ahead of time and then allow Seestar to start the plan on its own at the preset time and finish own its own. You can set it up and go to bed and look at the captured images the next morning. They are also planning to add an Equatorial Mode in another month or two which will add much more capability at the cost of having to do a Polar Alignment. As far as the Cons with the Seestar, it would be nice if it had a better imaging chip which could provide sub 2 arc-sec per pixel resolution and a larger field of view. But of course, this would add cost so it is only a relative Con. All-in-all I can highly recommend the Seestar S50 to anyone wanting an almost fool proof tool to capture dramatic images of what the universe has to offer. You can watch my Seestar Tutorial video with step by step instructions on how to set up the Seestar and begin taking images you first note. You will find it here www.youtube.com/watch?v=x3TXn5GT8SQ If you are interested in a Seestar, either the S50 or the smaller S30 please consider using my affiliate links below for your purchase. It will not cost you anything and will provide a small commission which helps to support my web site. High Point Scientific Seestar S50 bit.ly/3YL9aoY Seestar S30 bit.ly/3WR9sJg Agena Astro Seestar S50 bit.ly/4fISCUP Seestar S30 bit.ly/4gB2xLn
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