FAQs

Yes. Go to iPhone or iPad Settings > App Store. Turn App Updates on or off.

Yes. When you restart the capture, the Seestar will give you options to start over or continue the capture. (You can't pause a mosaic session and resume it several hours later because, of course, the sky will have moved a bunch.(Actually, Earth will have moved, but you know what I mean.) You can, however, start an entire new mosaic later or even days/weeks/years later because the stuff up there doesn't move much with respect to each other.

It seems the Seestar was designed for a tablet. Originally, some of the menus were hidden off the screen on a phone, and the “joystick” was smack in the middle covering what you're trying to center. On a tablet you could see the full menu and the joystick was offset. Now all that has been fixed and they both work well, although the iPad, of course, will give you a much bigger picture. ¹⁾

Seestar stacks subs to increase the signal to noise ratio (SNR). When the scope combines two subs the signal is doubled but the noise increases only 1.4 times. Put 100 subs together you've improved the SNR 10x.

What's the big deal with SNR? A single frame will look very noisy, like an older mobile phone photograph taken at night. But if you increase the SNR the noise begins to disappear and that allows you to boost the brightness of the images (it's called 'stretching the histogram.')

The Seestar will automatically stack frames as long as you let it run. When you stop the process it will save a single image, the result of the stacking process, to your mobile devices picture app. If you have “save subs' turned on in Settings you'll find each image that was added to the stack in My Works.

You can look through those saved subs (even if there are hundreds) using inspection tools, and throw out any that made it through Seestar's picky rejection algorithm. Don't throw out any with satellite trails, post processing software such a Siril AstroEdit will remove the streak and let you keep all the hard won pixels in the rest of the image.

Seestar's rejection algorithm is very picky. If you're taking 10 second subs you'd expect to capture six a minute. But experience has shown that we typical will get four, or even three, because the scope is so picky. If it's windy or high thin clouds roll in, that you night not even be able to see, Seestar will throw them out. If you're imaging too close to the zenith (straight up), field rotation will cause streaks so Seestar throws them out too. Put the scope on a rickety table, a bouncy wooden deck, or the roof of your car, and you'll see lots of rejects.

Depends on the target. Emission nebulae require the use of the so-called LP filter, which is really a dual narrowband filter that mostly passes light emitted by hydrogen alpha and oxygen three isotopes when they're energized by a nearby star (kinda like neon lights). That filter blocks a bunch of moonlight and other light pollution so you can basically work anytime, especially if your target isn't close to the moon. But that's not true for broadband targets such as galaxies and reflection nebula unless they're almost opposite the moon.

Yes, you can combine them, but poor relatively poor images will drag down excellent images when stacking software normalizes the images by matching the mean background of all the input images. But one option with Siril is to use scaled normalization which matches the dispersion by weighting input images so the good ones contribute more to the result, this improving the signal to noise ratio.

No, your targets are so far away and move so slowly (if at all) that images taken even years apart can be combined. There is some parallax if images are captured six months apart, as Earth crosses to the other side of its orbit, which can be used to measure the distance to stars. However, minimizing measurement error is the big challenge which is an indication of how little things up there change when viewed from down here.

Select the one you want from a list and swipe left. You see a red heart. Tap it and you're done.

If you're a bit of a geek, a Python application named seestar_alp will help you set up a session, capture multiple targets (even build mosaics), and shut down…among other things.

Stacking software uses an algorithm known as Sigma Rejection which (over simplified) looks at each pixel and checks to see if it is very bright (could be a star) and then checks to see if it has a very bright neighbor (could be a trail) and then looks to see if there are a string of such pixels (must be a trail).

The algorithm then looks at the neighbors of each bright pixel and takes the average brightness of each neighbor and replaces the bright one with the average so they all look the same.

By so doing, all the valuable data representing the remaining good pixels out of the total 2.1Mb is not lost when just a few hundred or thousand bad pixels can be rejected instead of the whole frame.

Perhaps the first description of the process is found in a paper back in the very early days of digital imaging. It provides a more accurate description of the process, which starts with, “Astronomers never seem to want to do anything easy.,” see https://articles.adsabs.harvard.edu/pdf/1987PASP...99..191S

In one sense, it's simply because many deep sky objects are huge and planets actually are relatively tiny. The apparently size of the Andromeda Galaxy (M31) is about 4x larger than the moon, for example, while Jupiter appears about 1/60th the size of the moon. But there's more to it than that.

Two basic parameters define a telescope optics: aperture (size of lens or mirror) and focal length (the distance to the point where light is brought into focus). Focal ratio is the relationship between the two two values. The Seestar has an aperture of 50mm and focal length of 250, so its focal ratio is 250/5 or 5, generally written as f/5 or ƒ/5. This is the 'speed' of our telescope's optics. ²⁾

Fast f/4 to f/5 focal ratios are generally best for lower power wide field observing and deep space photography. Slow f/11 to f/15 focal ratios are better suited to planetary astrophotography.

An f/5 system can photograph a nebula or other faint extended deep space object in one-fourth the time of an f/10 system, but the image will be only one-half as large. Point sources, such as stars, can be captured based on the aperture, however, rather than the focal ratio - so that the larger the aperture, the fainter the star you can capture, no matter what the focal ratio.

A related parameter is an astrophotography telescope's field of view (FOV) which is defined by the focal length and camera pixel size. The Seestar’s FOV is 1.28 degrees (76.8 arcminutes high³⁾) and 0.73 degrees wide (43.8 arcminutes). The Moon and Sun, for comparison, appear to be roughly 0.5 degrees (30 arcminutes) in diameter. So at 1x the moon fits in the Seestar frame, but at 2x it’s a bit too wide, at 4x the field of view is much smaller than our star and moon⁴⁾.

The palm trees in the camera's far view were were sized to match what your eyes see. The other image is as it appears on the mobile screen produced by the Seestar

Not directly. The camera is set to take advantage of something Sony calls High Gain Control (HGC) that reduces noise and increases dynamic range when the gain is set to 80.⁵⁾. But there is a complicated set of Python scripts that let you control just about everything about the Seestar including gain. See seestar_alp

The Seestar's Alt-Az mount tracks in two axes - in altitude (height above horizon), and in azimuth (direction around a circle). Because of something called field rotation shooting above about 70 degrees creates streaks. In fact, the Seestar won't shoot above 85 degrees. Why?

Imagine that we track an object that starts due east and as the object rises the altitude goes from 0º (horizontal) to 90º when it reaches our zenith⁶⁾ (vertical). Depending on your latitude, the azimuth will change some, too. ⁷⁾

As the object we're tracking reaches the zenith it will start going down in altitude on the other side of the zenith. So the altitude of the object goes from 0º to 90º and then from 90º down to 0º. When we started the scope's azimuth was toward the east, but as the object starts to descend it needs to be facing west–a difference of 180 degrees, so the Seestar has to stop shooting while the mount does an “azimuth flip” and then the scope can start shooting again.⁸⁾

The level sensor is notoriously quirky, ignore it. It doesn't matter (except for solar and lunar work) if your Seestar isn't level because it runs a Horizontal Calibration routine (assuming you haven't turned it off) before it starts Stargazing capturing DSOs, and it will adapt to even severe deviations from level.

How does it do that? By using the position of three stars it identified using plate solving during that mis-named “Identify current location” step when you start imaging.

Seestar's quality algorithm rejects some exposures because the scope jiggled, clouds passed over, stars have trails, etc. The timer in the top right corner of the Stargazing DSO page records the total of exposure time not clock time.

Bad news is Consumer Reports says most Extended Warranties aren't worth it, but YMMV.

Good news is most credit cards offer extended warranties. Buy with a card that does and keep a copy of the manufacturer's warranty.

According to ZWO, “Seestar's warranty starts from the date when the product is activated and lasts 2 years. The battery's warranty period is 1 year.”

Bad news, Chase VISA says the Extended Warranty Protection, “Extends the time period of the U.S. manufacturer’s warranty by one additional year, on eligible warranties of 3 years or less when item is purchased with an eligible Chase card or with rewards earned on an eligible Chase card.”

So you would get three years of warranty coverage for free if ZWO becomes an American manufacturer, as some people claim. Most extended warranties are for four years, so you'd be paying for just one year (year four).

Be very careful removing the finger prints and dust, the lens coating is very thin so rough wipes and chemicals can permanently damage it.

Start by blowing the dust off with am air bulb (not compressed air which is oily or your breath which has acidy moisture in it). Then use special purpose lens tissue (not facial tissue) and one drop of lens cleaner liquid for one very gentle wipe only.

Be careful not to touch the part of the tissue that will rub the lens because you finders are oily. Don't use the same tissue to go over the same area because it may rub in what ever you just wiped off. Get a new tissue and drop of liquid and repeat.

Don't let the edges of the lens get wet because the liquid can seep down inside and loosen the adhesive that holds the lens in.

Fact is, the dust won't affect you images unless it's very dusty. You're usually better off if you can't blow it off to just to leave it alone

If you want to stack and process the images the Seestar has combined (stacked) to create that one photo in Stargazing DSO Mode, you have to enable the "save each frame in enhancing" feature in Settings. Then, each image (called sub-frames or subs) will be saved in the Seestar. Then uou can download them to your mobile device or computer for later processing.

If you turn on the setting that tells the Seestar to save subframes you could have hundreds even thousands of image files saved on the telescope. Copy them off to your mobile device every couple of sessions and delete them from the Seestar.

The Seestar is sealed and the camera can't be removed, so you can't insert an add-on filter. That's a requirement because a special, very sensitive, hydrogen alpha (Ha) filter called an etalon is necessary. They can be tuned to half the width of a hydrogen atom, and are either built into a dedicated solar scope or into an add-on device. Both are very expensive. A Daystar Quark add-on is US$1,295. A dedicated solar scope such as the Lunt 40 is US$795 (plus camera ~$450 and mount ~ $550).

An exception to this is during a total solar eclipse. During these relatively rare events, the Moon covers the solar disk and allows just the prominences to peek out beyond the Moon's edge.

You will find excellent hi-res images of the Sun and some 48hr videos at the Solar Dynamics Laboratory website.

Visit https://iss.vierwandfrei.de, enter your lat and long, a date range, and how far you're willing to travel to catch it. The website will show you if an opportunity exists and send to you an email when it does. Be patient, the alignment will happen unless you live very far north or south.

If you can see a transit, check the place, time and cloud cover a few hours before the event. Small changes occur as the orbit is refined. When the time approaches (use the clock on the right side of the page at this link, start recording about a minute before the transit is to occur and continue until about a minute after. It is very punctual, but your timing may not be as accurate.

When your review the video the tiny, fast moving station will be hard to see, but it will be there if you have your time and place correct. Use a program such as PIPP to save, say, every 10th frame and stack them to get a timelapse view of the ISS.

Considering the ISS is moving at 17,500 mph and is 250-800 miles away, and is in front of the Sun or Moon for less than two seconds, it's amazing that we can catch it with the Seestar–and great fun when we succeed.

Emission nebula (the red ones) emit light from stimulated hydrogen alpha isotopes, kinda like fluorescent lights. The filter has a narrow bandpass that only lets through Ha and oxygen three (OIII) light, so the Ha is emphasized in the resulting image. Look for the green circle in the SkyAtlas preview image. Note that you are cutting out a lot of light so filtered images require more sub exposures to produce a good image. Reflection nebula such as the Wizard Nebula and Pleiades reflect broadband light from nearby stars so the LP (narrowband) filter should not be used. The Seestar defaults all the time to a UV / IR cut filter (unless the LP filters is selected) to avoid bloated stars with can be created because the Seestar camera is very sensitive to near-infrared light. Near-infrared light focuses at a different point than other visual spectra, which is what makes stars appear bigger than they should.

You have to tell the app to save every sub-frame in Advanced Features Settings. They'll be stored on the Seestar and can be downloaded, stacked, and processed later.

Only if you want to share your images with other Seestar users

The Baader AstroSolar Safety Film OD 3.8 unique properties come from the base material which produces a sharp pale blue image. The film is made from a specialized polymer originally developed for applications in nuclear and particle physics. This material has a highly uniform molecular structure, resulting in exceptional optical clarity and transmission.

The film is subjected to a proprietary process that creates a reflective metallic layer on both sides. This dual-sided coating ensures consistent density and minimizes the risk of pinholes that could allow harmful solar radiation to pass through.

Note: if you create your own filter from a sheet AstroSolar Safety Film, it must not be stretched taught because out changes the properties of the coating. Wrinkles are the sign of properly installed filter material and do not adversely affect the image.

The Thousand Oaks SolarLite polymer filter's protective properties are also embedded throughout the substrate which also reduces the risk of pinholes or scratches. Thousand Oaks says their flat polymer filter has the optical quality of glass, providing sharp, clearer views of the Sun. The most significant difference from the Baader filter is SolarLite produces a yellow-orange solar image.

For a more detailed discussion see Dr Steve Wainwright's blog post titled Understanding the use of Baader solar filters with a Seestar S50.

This is an old controversy (at least since the mid-90s when digital cameras became available to backyard astronomers). A lot of lore comes from the noisy CCD days when longer was always better and before we started using sigma clipping ⁹⁾ to remove outliers such as satellite trails.

The last two videos on the Useful Links page will answer the question about exposure length. They're about an hour long, but I've watched both several times and learned something new each time.

Until ZWO relaxes the rejection algorithm¹⁰⁾, and they give the choice to save rejected sub-frames, five seconds is my preference. That may change when the rumored EQ mode is introduced.

There's an algorithm that looks at each frame and decides if it's good enough to add to the stack. If it isn't, the Seestar will say 'stacking failed' for just that frame. Let it keep going and it will keep accumulating frames as long as you let it go and the computer says the frames are acceptable. Ten second subframes produce the fewest rejects, with 20 second frames you will see more, and stacking 30 second subframes will produce quite a few, mostly because the Seestar is finicky about star streaks caused by field rotation. Rejects will also occur if the Seestar wiggles because of wind or if you touch it. Even almost invisible clouds can cause rejects, too.

ZWO, unfortunately, labeled the filter a light pollution filter. and it's true, it will block a lot of light pollution, even moonlight when it contributes to the noise. But it also helps isolate the signal from some nebulae.

The filter is actually a narrowband filter that allows only two frequencies of light through: photons emitted by hydrogen alpha and oxygen three isotopes, and Ha and OIII are the predominate emissions from many nebulae. The North America Nebula (NGC 7000), the Orion Nebula (M420, and the Veil Nebula (NGC 6960/6992) are three bright emission nebula that make great Seestar targets.

Reflection nebulae, on the other hand, reflect broadband light from nearby stars so a narrowband filter isn't appropriate. When the narrowband (light pollution) filter is off, the UV / IR Cut filter takes its place and that's what you need for, say, the Witch Head (IC2118) or the Pleiades (M45).

In the advanced settings page use 10s (20s and 30s produce a lot of rejects).

Leave Skip Horizontal calibration off (you want it to use what you set as level and refine it to a gnats ass—fact is, your version of level can be way off and it compensates in Stargazing (sic) DSO Stacking mode. That's not true for Solar and Lunar modes.

Turn on Save each frame in enhancing (sic) stacking mode,

The teardown seems to indicate there are no clutches in either alt or az, although I find that unlikely. Anyhow, you can move the tripod just as easily. Remember, you don't have to worry about polar alignment, so moving the tripod is not going to confuse the Seestar.

And no clutches means you want to be sure to remove any add-on filters or dewshields before you shut down so they don't get pinched and force the OTA to a halt. The orange solar filter is thin enough it won't get in the way.

You definitely don't want to get tape sticky stuff on the objective lens. But if you want to tape a filter to the case, there isn't any reason why not (unless you're clumsy).

A special very precise* and expensive hydrogen alpha filter is required. Usually a dedicated telescope is used to mount the filter, although there are a couple of 'add-on' devices. But the add-ons can't be attached to the Seestar because the optics are enclosed. See Lunt and Daystar Quark for more details. *A special device called an etalon is used to tune the filter to a precision equal to half the size of a hydrogen atom!

Component telescope systems, in most cases, allow you to add a so-called reducer that will increase the field of view. But the Seestar's optics are sealed inside, so we can't add anything to the light path.

You can collect data of the same target even years apart. Stuff up there doesn't move much.

Think of the telescope as a funnel and the camera as a bucket. The camera sensor converts photons caught in the bucket into electrons, the computer counts the electrons to determine brightness and color and converts that into data for each pixel. The data is saved in a format that represents the pattern of photons that fell on the sensor. That pattern of data is used to create digital images.

As a rule of thumb, the answer is, “the longer the better.” But note that most of the improvement happens early and there is a matter of diminishing returns. As you add exposures together (it's called stacking) you're not making the image brighter, you're increasing the signal to noise ratio (SNR) which allows you to stretch the image more without noise making it look bad. Both signal and noise go up as you add subframes, but noise increase more slowly as this graph indicates (it's a square root function). Essentially, what that means is you have to quadruple (4x) the total exposure time to double (2X) the improvement in SNR. So if you have collected 180 frames (30 minutes), to double the SNR you'd need to collect another hour and half of data to have 720 (two hours) total. If you have fours of data you'd need to collect 16 hours total to double the SNR.