Review - 1.25" Twist Lock Adapter for ETX Telescopes
Posted: 4 May 2020
Twist Lock Adapter for ETX
ScopeStuff sent me their new 1.25" Twist Lock Adapter for ETX, one of a new line of rear port Twist Lock Adapters for several telescope models. It is a high quality machined accessory with a graphite-nylon compression ring to securely hold an eyepiece or star diagonal without marring the tube.
I initially used the Twist Lock Adapter on my ETX-90 without and with a star diagonal. As seen in the four photos below, when the telescope is mounted in the Altitude/Azimuth position there will be interference from the ETX base when pointing upward due to the short fork arms on the ETX telescopes. Depending on the user's Latitude, mounting in Polar Mode will reduce and potentially eliminate the interference, but you will be limited in how low you can go in Declination. Using the rear port is ideal when using the ETX as a spotting scope.
I was able to focus the ETX with the standard 26mm eyepiece in all four configurations.
The twist ring and compression ring can be removed to attach a removable lens camera using a standard T-ring adapter.
I mounted a DSLR in both configurations. Again, interference with the base can occur in Alt/Az mounting when pointing upward.
I was able to focus the camera in both configurations with the ETX-90. Use caution when mounting a camera at the ETX rear port, especially heavy ones, as there will be a severe out-of-balance condition. If you want to image with a camera at the rear port you should consider attaching a counterweight system (see the Helpful Information: Astrophotography page on "Weasner's Mighty ETX Site" for several counterweight tips). I recommend that most imaging be done using a camera mounted at the eyepiece hole on top of the telescope tube. You can still mount an eyepiece at the rear port using the ScopeStuff Twist Lock Adapter.
If you have de-forked your ETX and mounted the telescope tube on a German Equatorial Mount (GEM) or other mount, the interference between the ETX base and accessories attached at the rear port is eliminated. Several years ago I mounted my ETX-105 telescope on a Meade LXD55 GEM. The ScopeStuff Twist Lock Adapter for the ETX makes an ideal add-on, as seen here with a Shutan Wide-Field Diagonal and a DSLR. (The ETX-105 is mounted on the GEM using the ScopeStuff Low Profile Dovetail Bar for ETX Models.) Focusing with the eyepiece and camera was possible.
I also tested the Twist Lock Adapter with an ETX-125 Observer telescope. Focus could be achieved using the standard 26mm eyepiece at the rear port with and without a diagonal. Focusing was also possible with a DSLR at the rear port with and without a diagonal. However, it should be noted that the camera orientation may not be as expected with some ETX models. I also tested the Twist Lock Adapter with my ETX-70. I could focus the eyepiece when not using a star diagonal. Focus could not be reached with an eyepiece on the diagonal or with the DSLR in either configuration. The refractor ETX model did not have enough focus travel to allow focusing.
Using the ScopeStuff Twist Lock Adapter on my ETX-90 I did some observing and imaging of the Moon. I mounted a DSLR at the top eyepiece port and the 26mm eyepiece at the rear port using the Twist Lock Adapter and a star diagonal. As seen here the ETX was mounted in Polar Mode. This configuration allowed the large camera to be mounted where it would not hit the base. And with the eyepiece and diagonal at the rear port in Polar Mode there would be no base interference while viewing the Moon high in the sky.
This is the DSLR photo (full frame) of the Moon in the ETX-90.
If you have another telescope with standard SCT rear port threads you can remove the ETX rear port threaded insert from the ScopeStuff adapter and attach the adapter to your SCT. I tested this with my 12" LX600. I mounted a 1.25" eyepiece, with and without a diagonal. There was no problem with focus.
Depending on what equipment you have, you may experience a problem attaching a camera at prime focus. The ScopeStuff Primary Lock rod prevented attaching my DSLR.
Using a SCT port extension tube and/or a 1.25" nosepiece I was able to securely attach the DSLR. Using the nosepiece allowed the camera to be rotated to clear any equipment obstructions or to properly frame the camera field-of-view. I had no problems focusing in any of these positions.
This DSLR photo shows the gibbous Moon at prime focus using the SCT port extension tube, Twist Lock Adapter, and 1.25" nosepiece.
Since 1998 I have used a Shutan Camera & Video "visual back" accessory (discontinued many years ago) with my ETX telescopes. The accessory lets you use 1.25" eyepieces and a star diagonal at the ETX rear port. Using two eyepieces of different focal lengths on the telescope allows you to change magnifications by switching the flip mirror position. With a camera mounted at one port on the ETX you can use an eyepiece in the other port to visually align on an object. In both cases there will be a focus change when flipping the mirror.
This new high quality Twist Lock Adapter from ScopeStuff fills an accessory void for ETX users. Users of other telescope models should check out the other Twist Lock Adapters that are available from ScopeStuff.
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