Bresser Smartphone Adapter
Explore Scientific
$46

I have been doing smartphone astrophotography since December 2007 when I received the original Apple iPhone. Back then there were no smartphone adapters to attach the phone to an eyepiece, so I eventually made my own. Today, there are many different types of smartphone adapters for doing astrophotography and terrestrial photography through telescopes, spotting scopes, and binoculars. Most smartphone adapters work with 1.25" eyepieces, but only a few adapters will fit 2" diameter eyepieces or even some 1.25" eyepieces with large outside tube diameters. The Bresser Smartphone Adapter available from Explore Scientific ($45.95 USD) is an adapter that will fit many 2" eyepieces and will also work well with some large 1.25" eyepieces. It will also work with many different smartphone sizes and camera placements. The Adapter will fit eyepiece widths up to 68mm (2.68 inches) and smartphone widths 50-88mm (1.97-3.46 inches). [Note: Explore Scientific provided the Adapter for this review that first published in Astronomy Technology Today magazine.]

The Bresser Smartphone Adapter comes with a small instruction manual in German, English, French, Dutch, Italian, and Spanish languages, as seen in the image on the right.

The Adapter is plastic and very lightweight, but it is sturdy enough to hold the eyepiece and the phone. The grips for the eyepiece and the phone are padded to prevent surface marring and slippage. More on slippage later. The manual says the phone sliding retaining bracket is marked with an arrow. Mine did not have any marking, but only one bracket moves so there is no problem attaching the phone to the Adapter.

This is my iPhone 11 Pro Max mounted on my ETX-125 Observer telescope.

You align the phone to the eyepiece by adjusting the phone in the sliding bracket and rotating the phone on the Adapter. With small diameter 1.25" eyepieces the bracket may cover the volume control buttons on some phone models (see next photo). This may or may not be an issue with some phones when taking a photo. With larger diameter eyepieces this will be less a problem as the camera will be positioned further away from the bracket.

As with many smartphone adapters, the Bresser Smartphone Adapter, even with its large opening, might not fit on the main body of some large diameter eyepieces, but it might fit on the rubber eyecup section of the eyepiece. Attaching the Adapter to the eyecup will reduce the field-of-view seen by the phone camera as it places the camera further from the eyepiece. Here is the Bresser Adapter attached to the eyecup on the Explore Scientific 2" 14mm 100° eyepiece on my LX600 telescope.

The Bresser Adapter fit better on the Explore Scientific 2" 5.5mm 100° eyepiece where it can be properly attached to the main eyepiece body.

Using the Bresser Smartphone Adapter I mounted the iPhone on an Explore Scientific 2" 5.5mm 100° eyepiece and did some smartphone astrophotography for this image of the crescent Venus (a stack of 2485 video frames).

This photo shows the lunar craters Theophilus, Cyrillus, and Catharina using the 5.5mm eyepiece.

The Adapter worked perfectly on a 2" 30mm eyepiece for a nice iPhone image of the Moon.

The Bresser Adapter fit a 1.25" 15mm eyepiece with no phone volume buttons interference (top photo below). The following images are M13 (Great Globular Cluster in Hercules) and M104 (Sombrero Galaxy) using the iPhone with 15mm eyepiece. (Yes, you can do Deep Sky Astrophotography with a smartphone.)

To use the Bresser Smartphone Adapter I recommend the following:

1. Focus the object to your eye (wear glasses if needed for clear distance vision). [Do this for any smartphone imaging, with or without an adapter.]
2. Remove the eyepiece from the telescope, attach the Adapter to the eyepiece, attach the phone to the Adapter, align the camera over the eyepiece using a bright light source (sky, flashlight, etc.).
3. Mount the eyepiece with the Adapter and phone back on the telescope.
4. Center the object in a smartphone camera app field-of-view.
5. Carefully adjust the field-of-view as needed by slewing the telescope and/or adjusting the phone on the Adapter.
6. Lock the smartphone camera focus to Infinity (if possible). Avoid using auto-focus.
7. Take the photo. Take many photos using different exposure settings.

A word of caution when using the Bresser Smartphone Adapter. The spring-loaded bracket that holds the smartphone is very strong (good), but is so strong that with some smartphones it may actually squeeze the phone out of the bracket, as seen below. This can result in the phone falling to the ground (not good).

Some smartphone adapters include a ¼-inch tripod mounting hole, but most do not. The Bresser Smartphone Adapter does not have a tripod mounting hole.

Summary

If you need a smartphone adapter that supports some large diameter 1.25" and 2" eyepieces, the Bresser Smartphone Adapter available from Explore Scientific is a good choice. The Adapter should also work on some spotting scopes and binoculars models, although they typically have small eyepiece sizes so the bracket interference with smartphone side buttons might be a concern. The Adapter will securely clamp to the eyepiece and as long as you watch for the smartphone slippage in the bracket your smartphone will be held safely in place. The Bresser Smartphone Adapter is so lightweight that it should not create a significant balance issue with even the flimsiest of telescope mounts. As with all smartphone adapters, before purchasing check the dimensions of your smartphone to ensure it will fit the Adapter and your eyepiece dimensions to ensure size compatibility.

This review appeared in Astronomy Technology Today magazine, Volume 14, Issue 7.

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