Review - Smartphone 8X Telephoto Kit with Solar Filter
Posted: 5 May 2017
The planning for the Total Solar Eclipse on 21 August 2017 is well underway by myself and many others. I think I'm prepared for photographing the partial and total phases using my Nikon D7200 DSLR with a Tamron 150-600mm lens and the iOptron SkyTracker Pro. But other than wide-angle sky photography of the shadow approaching and receding, I had not considered using the iPhone for the partial phases. That is, I hadn't until I visited the Spectrum Telescope web site and became intrigued by their Universal Mobile Phone Telescope Kit with Solar Filter. I contacted Spectrum Telescope and they provided a Kit for this review.
As seen at the right, the Kit is a complete set of accessories for your mobile phone:
8X telephoto lens
Smartphone mount for lens and tripod
Removable glass solar filter
The 8X telephoto lens can, of course, be used without the solar filter. Here you can see the lens Kit attached to my iPhone 6s Plus which is mounted on the included tripod:
(The Apple earbuds shown in the photos above are not included with the Kit, but they should be used as a "remote shutter release" whenever you have the iPhone on a tripod.)
The lens holder expands to grip your phone securely. It fit my iPhone 6s Plus fine and there was no concern that the phone might fall out. Depending on the placement of your phone's side buttons and camera lens location, you may need to rotate the phone one way or the other when inserting it into the holder. The 8X lens mounting arm position is adjustable so you should be able to align the phone camera lens with the telephoto lens with most phones.
As is the case with many table-top tripods, the Kit tripod becomes unbalanced when you aim the camera well above the horizontal (more than about 30°). You will need to use a larger camera tripod or hand hold the phone when shooting the Moon or Sun high in the sky. The Kit smartphone holder does use a standard 1/4" camera mounting hole.
You can use the 8X telephoto lens to photograph the Moon. Here are two handheld photos of the Moon taken with the iPhone 6s Plus using the iOS app "NightCap Camera". The top one was taken using the included 8X telephoto lens. The bottom one was taken using a cheap ($15) 8X clip-on telephoto lens I had previously purchased. A slight difference in magnification is visible, with the Kit lens having more magnification.
Kit 8X telephoto lens
Cheap 8X telephoto lens
The Moon photos above do not really show the image quality, but these handheld terrestrial photos using the Kit 8X telephoto lens do:
Cassiopeia Observatory with Kitt Peak Observatory in the distance (right of center, 65 miles away)
Vignetting and some lens distortions are evident. If you place the Moon or Sun at the center of the your image the vignetting and distortion will not be a problem.
To photograph the Sun using the solar filter I highly recommend mounting the phone on a camera tripod and use a remote shutter release (or a self-timer), as seen here:
When using the solar filter on the 8X telephoto lens, slide the filter housing fully onto the lens and tighten the setscrew. You can then rotate the filter which will rotate the lens focusing ring to focus the image. You can do this focusing with the lens off the phone mount and safely look through the lens + filter at the Sun.
Taking a photograph of the Sun is of course the main purpose of the Spectrum Mobile Phone Telescope Kit with Solar Filter. Not unique to smartphone imaging of the Sun will be two challenges: seeing the sun on the screen in the bright daylight, and getting a proper exposure. You can shield the phone screen with your hand (or black cloth). Depending on the camera apps you have on your phone you may or may not be able to get a good exposure since the app will "see" all the black area and try to expose for that, resulting in an overexposed image of the Sun. The iOS Camera app will slightly overexpose the Sun even after manually decreasing the exposure value all the way:
Using an app with full manual exposure control, as I did with this NightCap Camera photograph, you can get a much better image of the Sun:
In both images above you can see a "light leak" around the lens holder. Light seems to be not only reflected from the rear lens of the telephoto, but there also seems to be a secondary reflection from light going backwards into the lens and bouncing off the silver surface of the filter. In addition there is scenery being captured at the right (i.e., blue sky and a tree) directly by the phone's normal lens with the 8X lens optically aligned over the camera lens. This side light leak may not happen with all phones, depending the camera lens location. And you can certainly crop your photos to show only the Sun. Using a black cloth as a light shield would prevent any leaks; it would also make seeing the image on the phone screen way easier.
You will probably crop your images after you take them. Something like these of the Moon and Sun:
I also tested the solar filter with my cheap clip-on 8X telephoto lens, seen here with the Spectrum lens still attached to the phone:
The clip-on lens did not shift its position over the camera lens, but clips for other lens models might not be as securely held due to the extra weight (as little as it is) of the solar filter. An interesting "Tatooine" Two Suns effect was captured using NightCap with the cheap lens:
The extra "sun" is a reflection from the optical surfaces and may happen with any lens.
You can handhold the solar filter over the phone's camera to take a normal 1X magnification photo of the Sun. But that has another set of challenges. As I didn't want the camera lens aimed at the Sun for extended periods of time as would be the case if the phone was on the tripod, I handheld both the phone and filter. Aiming at the sky, holding the filter in place over the camera lens, trying to adjust the exposure, and then taking the photo all combined to make imaging the Sun for a normal photo nearly impossible. It is doable but not really worth the effort:
(No, that's not an octopus on the camera lens. The filter was not centered over the camera lens when I tripped the shutter button.)
You should plan to use the Spectrum Mobile Phone Telescope Kit with Solar Filter for its intended purpose: take magnified photographs of the Sun's disk.
As seen in the Sun photographs above you can get good images of the Sun's disk using the Spectrum Telescope Universal Mobile Phone Telescope Kit with Solar Filter. This means that you will be able to capture images of solar eclipse partial phases using your smartphone. The telephoto lens in the Kit is not optically high quality, but it is good enough for imaging the Sun and Moon at 8X. Just realize that the 8X magnification is not really sufficient to get good photos of sunspots or lunar craters, even when applying some digital zoom or image cropping. For the total solar eclipse phase the field-of-view of the 8X lens (without the solar filter attached) will be wide enough to capture images of the solar corona with your smartphone.
Spectrum Telescope also sells screw-on solar filters for camera lenses. They come in various lens filter diameters from 37mm to 82mm. Here is the 37mm filter I was provided:
If you are looking for a solar filter for your camera and your lens accepts screw-on filters, check out Spectrum Telescope.
And they sell a pretty complete line of solar filters for binoculars and telescopes. Here are two styles they sent me, glass on the left and thin film on the right.
All of the supplied Spectrum Telescope solar filters were of high quality, both optically and physically. If you don't want to make your own filter from proper solar filter materials (or even if you do), check out Spectrum Telescope. I hope to review some of their other products in the future.
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