Hacking the EduSnap 53ED

The EduSnap 53ED telescope uniquely combines feedback from the camera to the mount for tracking, under control of the EduSnap app. This is a quite ingenious product! But it also tends to create a closed system in the sense that the app, the camera,  the objective lens, and the mount are cdependent for function, and useless separately.

But that's not quite the case for the telescope tube! The eyepiece tube is a standard 1.25" opening that lets you attach other cameras, bypassing the dedicated camera. And one of its threaded joints has a 54mm thread that is a standard for telescope accessories. And actually, the form and function of this front half of the scope corresponds nicely with the more expensive RedCat 51 refractor scope for astrophotography. Let's look at what we can do with these open interfaces.

Via the eyepiece tube

The mirror box design of the 53ED system essentially bypasses the built-in camera when you place the bronze lever into the eyepiece position. The image will be inverted, but this can be flipped in your photo editor. Secure a 1.25" astro camera into the eyepiece holder and approximately adjust the camera's parfocal collar while observing in your usual recording tool (like SharpCap or AmCap), then adjust the focusing collar to optimize the image before use. If you use a guide camera for imaging, this configuration works on a tracking mount with both ST4 and pulse guidance in the PHD2 tracking program.

Via a 54mm adapter

After loosening one 2.5mm setscrew on each mounting ring, the telescope tube assembly can be unscrewed into three sections: the camera/mirror box component, the focusing ring section, and the main tube extension. Conceptually, there is not much point in separating the two front sections because those are the exact function of other astrographic refractors like the afore-mentioned RedCat 51. Just set aside the camera/mirror box, and instead work with the M54 thread interface in the focusing unit. 


I like comparing to this much more expensive scope because they are similar in form, function, aperture and image scale, while being very different in terms of price and precision. But the EduSnap 53ED can be used exactly the same way as long as you appropriately set your expectations.

From the back surface of the focusing collar to the image plane, there is a back focal length of about 80mm to work with. 


I found two useful adapters for this interface. 

First, an Amazon shop offers this adapter for the M42-based (T2 mount) accessories:

 M54x0.75 Female Thread to M42x0.75 Male Thread


This adapter does not quite snug up to the focusing ring. You may need to creatively cut some shim washers to build out the shoulder by about 2mm for the focusing ring to thrust against.

Secondly, Amazon also sources an adapter that presents the M48 standard thread.

M48 Male Thread to M54 Female Thread Interface Mount 


The M54 end of the M48 adapter is also a bit shallow and could ideally use an additional 2.5mm deep washer or shim stack to take up slack when adjusting the focusing ring.


With the M42 adapter, I was able to pick through a set of varied lengths of T2 extension tubes to make up a length that could connect my Sony NEX camera via a short T2 adapter to the Sony eMount.

Using the M48 adapter, I was able to attach a filter tray and a rotator with room for one more inline accessory. The sky is the limit.

Actually, optical quality is the limit. An achromatic lens may trade field flatness for chromatic correction. I can't wait for clear skies to try out an APS-C image with a two-band star filter using my iEXOS-100 mount, using PHD2 to provide the tracking. More later...

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