Back in our October 2017 newsletter, I announced that we’d be carrying the iOptron line of products. Well, with spring firmly established now in 2019, the weather is improving and it’s the perfect time of year to get out at night and do some night sky shooting! I am going to publish most of that original article here as a refresher, along with some updates, and also show some examples of tracked night shots that I have done over the years with my own iOptron SkyTracker. I personally have the older model and have had very good success with it, but these new ones (SkyTracker Pro and SkyGuider Pro) are much improved over mine in many ways. So here is a slightly revised version of that original newsletter article…
iOptron has long been known for an affordable range of amateur astronomy products, ones that generally perform better than you might expect given their modest price point. I myself have been using one of iOptron’s star-tracking mounts for a few years now, the SkyTracker. You may have noticed a mention in last month’s newsletter where I used it to help photograph the solar eclipse while in Oregon. The SkyTracker is a motorized mount that you put in between your tripod and head, and it acts to counter the rotation of the earth, allowing you to take much longer exposures of the night sky and still get pinpoint stars, instead of the stars leaving trails in your shot. My mount is powered by four AA cells and is generally really easy to use. The only challenging part is polar-alignment…
In order for the SkyTracker mount to counter the Earth’s rotation, its axis of rotation has to be lined up very precisely with Earth’s axis of rotation. Thankfully, here in the northern hemisphere, we have a star called Polaris that is almost exactly at the required spot, only off by a little bit. However, even though it is close, it is not perfect and back in the day, prior to smartphones with built-in GPS modules, it was actually a real pain to get things aligned perfectly. However nowadays, you can simply download an app for your iPhone or Android smartphone and it will take all the guesswork out. Here is a screenshot of the app from my iPhone…
Basically, the app knows exactly where on earth you are from your phone’s GPS, and it also has the date and precise, accurate time info from cellphone towers, so it can automatically calculate precisely where Polaris should be in relation to the exact point of earth’s axis of rotation at any given time. The SkyTracker mount has a small, red illuminated alignment telescope that is lined up with its own axis of rotation, and in the eyepiece, you’ll see the red chart as shown in the app. In the app, you’ll see a small green cross and that is exactly where you need to aim, positioning Polaris in the SkyTracker’s alignment scope at that spot. Having said that, this in itself can be a bit of a challenge since even though the SkyTracker mount has geared altitude (vertical) and azimuth (horizontal) controls, when you set the locking clamps, there can be a bit of shift. So it becomes a little game, offsetting Polaris from the spot shown by the green cross, then watching it drift into place as you tighten the clamps! The newer versions of iOptron’s star- tracking mounts have been redesigned with improved alignment assemblies and clamps, and are much easier to use.
Here is a shot of my own, older model SkyTracker while down in Oregon shooting the 2017 total solar eclipse. It was mounted between my Manfrotto 055 CF legs and Manfrotto ballhead. Frankly, the SkyTracker was a little bit overloaded with my Fujifilm X-Pro2 and big Fujinon XF 100-400mm zoom. It would have benefitted from the optional counterweight assembly in that case, which I did not have…
(click on image for larger view)
Here is a shot of the eclipsed sun I got with that rig: it allowed me to track the sun steadily for the duration of the eclipse and not have to reframe it every few seconds! I did have to tweak the framing a few times, since the old SkyTracker I have does not have a “solar” tracking rate. In addition to pure sidereal tracking (the stars), the new models have both solar and lunar tracking rates as well, since both the sun and moon move relative to the background stars, requiring slightly different speeds for tracking them accurately. So, these trackers are useful for more than just tracking stars. This photo was taken just after totality, showing the start of the classic “diamond ring” effect, as well as showing lots of detail in the sun’s corona…
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Here is a photo of the fully eclipsed sun, a shorter exposure to capture the red erupting prominences (loops of gas/plasma usually associated with sunspot groups) coming up off the sun’s surface. With a fairly “quiet” sun that year, the prominences were not all that dramatic…
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Once you’ve got Polaris accurately placed, that’s it. The mount just keeps running and turns the opposite direction of the Earth – easy! If you are in the southern hemisphere, alignment is a bit more challenging since the star used for finding Earth’s south polar axis point is much fainter and harder to identify. There is a switch on the SkyTracker that you set to ’N’ for those here in the northern hemisphere and ’S’ for those using it down under, in the southern hemisphere. Polaris is actually easy to find: just follow a line through two stars making up the bowl of the Big Dipper, the ones opposite the handle and pointing up out of the bowl, and they’ll make an almost perfect line to Polaris. A quick Google search came up with images of many finder charts. Here is one example…
Without a star-tracking mount, you can only manage exposures of a few seconds if you want to capture pinpoint stars and even with a really wide lens, like a 20mm, you would need to keep exposures down to 15 seconds or so. However with a basic tracking mount, you can easily get up into the minutes, even when using longer lenses, and still maintain tack sharp stars… as long as you make an effort to polar align it as accurately as possible. The following photo is a 15 minute exposure with my X-Pro2 and Fujifilm’s wide-angle 16mm f/1.4 lens (24mm full-frame equivalent) at ISO 400 and f/2.2, and this one not tracked of course! Taken in the Alabama Hills, southern California, it was a clear moonless night, so the illumination on the mountains is mostly from starlight…
Time-Exposure – not tracked (click image for larger view)
This next, totally different shot, is of the Andromeda Galaxy (M31) was taken with the iOptron SkyTracker, using my X-Pro2 with Fujifilm’s telephoto 100-400mm zoom at 190mm (285mm equivalent), a 4 minute exposure at ISO 1600, lens at f/5. With such a long focal length, had I not used a tracking mount, the stars would literally have trailed much of the way through the frame with a four minute exposure! As it was, it took several attempts to get a sharp photo with pinpoint stars at this relatively long focal length, since a gusty wind was blowing. For this shot, I ended up standing beside the rig and holding up my camp chair, keeping the wind off the camera and tracking mount during the entire exposure. The shot was taken in central Oregon, near the John Day Fossil Beds National Monument, Painted Hills Unit…
Time-Exposure – Tracked! (click image for larger view)
There are other factors that can cause issues with longer exposures, things such as vibration from wind (as mentioned above), lenses dewing up (fogging up), heavier lenses that cause the tracking mount to “lag” (run slower), where you would then require a counterweight set to balance things out, and so on. Using one of these mounts effectively in more adverse conditions, or with longer lenses, does require a bit of practice.
iOptron has many different products, including telescopes, tube assemblies and much larger, higher end tracking mounts used for high magnification astrophotography, as well as lots of other items, but for now, we are only stocking their camera tracking mounts. The new mounts are convenient for the built-in rechargeable battery pack that can be charged via USB, unlike the older model I use which ran of four AA cells. With these new ones, you could use a USB power-bank to charge while in the field too.
For a basic tracking mount that would work well for mirrorless cameras, or DSLRs with smaller lenses, there is the SkyTracker Pro, which is basically a new, improved version of the one I use. It now has solar and lunar tracking rates, an internal USB rechargeable battery and an improved mount for easier polar alignment. It’s shown in the photo at the top of this blog posting and is priced at $389 CDN. To get a better sense of how compact this device is, check out the next photo…
Then there is the SkyGuider Pro, and we generally stock the complete kit with counterweight, suitable for using larger lenses and/or heavier cameras. This unit is $559. Like its little brother, it also has solar and lunar tracking rates as well as ports for an optional hand-controller and camera trigger. The tripod, and the camera and lens of course, are not included, but the photo below shows the setup that you could use for a heavier camera system with the SkyGuider Pro…
Here are all the components that you actually get with the full SkyGuider Pro kit…
For smaller cameras, you don’t have to use the counterweight assembly – see photo below for that configuration. The ball-head, camera and tripod in this photo are, once again, not included. You can use pretty much any tripod head you might already own, as well as your own tripod, presuming it is sturdy enough!
Have a browse on iOptron’s website – http://www.ioptron.com and check out the wide range of products they offer. If there is a telescope or other item that you’d like, give us a call and we can get you a price and special order it for you as well.
Following are a few more tracked photos I have done in the last few years. This next shot is interesting, a photo of the galaxy M101, which forms an equilateral triangle with two of the handle stars of the Big Dipper. You can just make it out on the full frame below, the fuzzy spot near the middle, just above dead centre…
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That photo was a tracked shot, also while was under dark skies in Oregon, a 2 minute exposure at ISO 400 with my X-Pro2 and XF 90mm f/2, shot wide open at f/2. Much to my surprise, when I zoomed in to 100%, I noticed that I could identify a ton of other faint galaxies in the neighborhood of M101. See the 100% crop below, where I labeled the galaxies in Photoshop that I was able to identify. That Fujinon 90mm lens sure is sharp wide open, and the SkyTracker mount did a good job at tracking, even examining the shot fully zoomed in…
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Below is a shot of the southern Milky Way, the Sagittarius region, which shows the Lagoon Nebula (M8), the larger pink blob, and the Trifid Nebula (M20), the smaller blue and pink blob to the upper right of M8. The blue colour (reflection nebulosity) is caused by the light of a bright blue star reflecting off the dust it is embedded in, and the pink glow (emission nebulosity) is caused by the energy of a star causing gas clouds to actually fluoresce, similar to a neon light. The other, somewhat brownish looking blotchy areas, are actually dense star clouds in our galaxy (The Milky Way) which are not resolved in this photo, and the darker areas are dust clouds and dust lanes in our galaxy blocking the light from the stars behind them. This shot was also taken with my 90mm f/2, wide open at f/2, at ISO 400 with a 2 minute tracked exposure, also while I was down in Oregon under dark skies…
(click image for a larger view)
Lastly, here is the shot of a nice (and unexpected) auroral display at Pitt Lake, here in BC. Due to the tracking mount keeping pace with the stars, the mountains are slightly blurred. Shot with my Fujifilm X-E2 and Fujinon XF 23mm f/1.4 at f/2.8, ISO 200 and 125 seconds…
(click image for a larger view)
