Product Review: Takahashi Epsilon-130D
The quest for fast astrographs seems never-ending in astrophotography. Finding a fast astrograph with well-corrected optics and a large imaging circle that doesn’t break the bank is becoming increasingly difficult. Enter the Takahashi Epsilon. Well-priced, well-built, and blazingly fast, this little scope is an astrophotographer’s dream.
Reasons to love the E-130D:
- Wicked-fast optics with a large image circle
- Mechanically well-built with quality focuser and rotator
- Ships collimated and holds collimation EXTREMELY well
- Modestly priced, especially given its f/ratio and image circle
- Corrective optics included in the price
Considerations with the E-130D:
- Focuser block will likely require an upgrade to attach a focuser motor
- Like any newtonian, tube orientation relative to the sky must be considered in order to keep the diffraction spikes in the same orientation from night to night
As with any Takahashi telescope, the Epsilon is packaged very well. The scope was triple boxed and secured with purpose-built foam to protect it during transport. The first thing you notice about the Epsilon coming out of the box is the mechanical quality of the scope. It is collimated prior to leaving Takahashi America and the secondary collimation screws are locked down tight. My scope arrived in perfect collimation and has continued to hold that collimation over the last year of use. That bears repeating I think - I haven't touched the collimation of the Epsilon in over a year and it is still perfectly collimated. Anyone who has used a Newtonian can attest to how impressive that is. In addition to the rigidity of the collimation mechanics, the focuser mechanism is very robust, allowing for easy manual focusing of the telescope. The rotator on the focuser is solid, preserving collimation when rotating. I purchased the Takahashi rings for the E-130D as well, which provide nice large knobs that are easy to tighten and loosen to secure the scope. All in all, the telescope simply “feels good,” with no sign of mechanical weak points.
Boxes Inside Boxes
With Rings and a Plate
Collimation is a little different than one might be typically used to on a Newtonian. With its oversized and offset secondary mirror, the view through the Takahashi collimating eyepiece is a little strange. Fortunately, Takahashi’s E-130D instruction manual explains the collimation process in great detail, and, after a little studying (and a phone call to Takahashi America to confirm), verifying collimation was simple.
The E-130D, which Takahashi refers to as a "Hyperboloid Flat-Field Astrograph," operates at a blazing fast f/3.3 (and, thanks to an oversized 166mm hyperbolic primary, the system is a "true" f/3.3 - no consideration for secondary obstruction is necessary). Using an offset and oversized secondary, the telescope produces a flat field on a full-frame (43mm diagonal) sensor. With a full-frame chip, the telescope produces a huge 4.77 x 3.18 degree field of view, enough to encompass the entirety of M42 and Barnard 33 in a single frame (see image at the end of this review). The E-130D is 1.2 – 2.1 stops faster than a similarly sized f/5 or f/7 refractor, while being more compact and lighter weight, making it a perfect travel companion. While it may not seem like much, those couple of stops can make a huge difference when imaging. For example, the wide-field of view and speed allows for users to take large mosaics in a relatively short amount of time, such as this 15-panel mosaic of the Sadr region (too large to load in full resolution here, but you can see the full image here). This image took me just over 90 hours to complete. Had I used an f/6 refractor of a similar focal length, to achieve a similar per pixel SNR would have required over 300 hours of integration time!
90-hour, 15-panel mosaic in Cygnus. By Matt Dahl.
As with all my scopes, I wanted to install an autofocuser. First things first, I upgraded the stock focuser to the Takahashi MEF3, allowing for fine focus control. I then installed a focuser motor. I originally chose the Posidrive by Starlight Instruments, which is an excellent focus motor (more on that in another review), but the Posidrive (or so I thought) put too much torque on the focuser, causing the motor to slip on the pinion, making it perform unreliably. I tried using a smaller motor, ordering the FocusLynx QuickSync, but had the same result. It turned out the issue was in the plate that holds the MEF focuser assembly to the focuser pinion retention block; It isn’t quite sturdy enough to hold up to the torque of a focuser motor. As such, I wound up upgrading the focuser to the Starlight Instruments Takahashi Micro Pinion Assembly block (see image below), which allowed me to attach the HSM20 from Starlight Instruments (the motor I went with ultimately, though the QuickSync would have worked too) and the AF has worked flawlessly ever since.
Starlight Instruments Retrofit Block Installed
Starlight Instruments Retrofit Block and HSM Motor Installed
Being mostly a refractor user, imaging with a Newtonian presented some interesting challenges and learning opportunities. For one, mount/telescope balance can be significantly more challenging than a refractor, given the potential weight asymmetries that can exist. For another, dew prevention (especially here in the dewey Pacific Northwest) proved challenging. Keeping dew off the primary AND secondary was difficult and ultimately required me using two dew straps: one down near the primary and a second behind the focuser mechanism to provide some heat to the secondary (a secondary dew heater may make more sense in the long term, but the scope does not come equipped with one). Perhaps the most challenging and subtle of issues was that of telescope tube orientation. While I'm used to adjusting camera rotation for framing of targets, I've never considered the orientation of the telescope tube relative to the sky before. With a refractor, this is a non-issue. However, with a newtonian that has spider vanes, it's a different story. The diffraction spikes generated by the spider vanes in the system are directly related to the orientation of those vanes relative to the sky. If the telescope tube rotates between data capture (say, if you take the telescope out of the rings and then put it back in without it being EXACTLY in the same spot), then the diffraction spikes will not line up in the final image. As such, I highly recommend choosing one orientation of the tube in the rings and leaving it that way, otherwise older data cannot be added to in the future without diffraction spike issues.
Another interesting challenge I had to work through involved the mirror on my Canon 6D. Due to the steep light cone of the f/3.3 system, the shadow of the reflex mirror on the 6D was visible in my frames (both light and flat frames). I fully expected the shadow to calibrate out in processing, but it did not. I haven't yet tracked down the reason for that yet, but I did wind up cropping some of the frame on my image. For sensors without a reflex mirror (i.e. mirrorless or dedicated astro-cameras), I wouldn't expect any issues, but if you are considering the E-130D for use with a DSLR (particularly a full-frame DSLR), it is something to be aware of.
In the field the Epsilon performs extraordinarily well. The focuser easily and reliably achieves critical focus (post focuser block upgrade). The lightweight scope is easily handled by my Astro-Physics 900 mount, but could be used on a much lighter mount system, such as the EM-200. Takahashi also makes clever use of internal threads on their Wide-T mount, allowing for easy use of filters (such as the IDAS V4) when using a DSLR. The rotation mechanism on the 130D is smooth and the telescope retains collimation through rotation. The mechanics and simplicity of the scope make it a joy to image with.
Photographing with the E-130D is definitely much easier than I ever expected a fast Newtonian to be - in fact, it is no more difficult than the refractors I'm used to using. Overall, I’m extremely impressed with the performance, quality, and workmanship of the Epsilon-130D. For those photographers looking for a fast scope with a large image circle that doesn’t require a second mortgage, I highly recommend this scope. It’s a hassle-free astrograph that delivers quality at a modest price.
M42/NGC2024/Barnard 33 Complex - Epsilon 130D and Hutech Modified Canon 6D with IDAS V4 filter by Matt Dahl - Image Details Here
North America Nebula - Epsilon 130D and QSI683 WSG-8 with Astrodon narrowband filters by Matt Dahl - Image Details Here