TS-Optics 50 mm Angled Finder and Guide Scope with 90° View - 1.25" and T2 Connection

TS Optics 50 mm angled finder with upright and non-mirrored image

TSFRE50T2 is more than just a finder. The good 2-element objective with 50 mm diameter already shows many hundreds of deep-sky objects in combination with the illuminable reticle eyepiece TSIR20.

The conversion into a guide scope for astrophotography is done in a few easy steps

When the prism is removed from the tube, you will find an M28 female thread. This adapter can be removed by loosening the three radial screws. Now the T2 female thread is visible, from which further adaptations can be made. From the internal thread you have a very generous working distance of 90 mm to the focus. So all common cameras and even correctors can be integrated. We particularly recommend the following adaptation:

TSHeli1 Helical focuser with male T2 connection thread on the telescope side, the focuser fits directly into the female T2 thread. The working distance from the T2 and 1.25" connection is from 33 mm to 43 mm.

You can shorten the working distance with the matching T2 extension tubes. The extension comes simply between the finder and the helical focuser.

The advantages and product features of TSFRE50T2:

High quality metal design for best possible stability

Good 2-element lens with multicoating

Focusing by rotating the 1.25" helical focuser on the eyepiece side for observation

Female T2 thread available for conversion into a compact guide scope

Solid clamping by compression ring

Upright and non-mirrored imaging through the 90° Amici prism

The viewing position can be rotated in the desired direction

The adjustable tube rings have metal screws with a plastic tip to avoid scratches on the telescope

The finder fits into standard finder mounts such as those provided by Skywatcher, Celestron, GSO, ...

Fitting eyepieces and autoguiders for TSFRE50T2:

The focus of the finder is about 5 mm above the 1.25" receptacle of the Amici prism. This is sufficient for many eyepieces, such as Plössl eyepieces. A very nice eyepiece for centering is the illuminable reticle eyepiece TSIR20, which is linked in the accessory recommendations.

Even without the T2 connection the finder is suitable for autoguiding. However, the autoguider must have a 1.25" housing, otherwise you will not get into focus. The T2 connection, on the other hand, will bring you into focus with all cameras.

Testimonial from a customer

Our customer Thomas Fritz bought this finder scope and made a few experiences, which he would like to share:

"Hello Teleskop-Service,

I bought this finder (TSFRE50T2), because it should allow the conversion to a guiding scope, among other things. You write: ´With only a few steps the conversion into a guiding scope for astrophotography succeeds´. I wanted to use the finder with the Baader Polaris 25 mm eyepiece.

The finder provides good quality optically, still adequate at the edges. However, I cannot focus the Polaris on the Amici prism, it would have to be a few mm closer to the prism. With a shorter 25 mm eyepiece it works.

No problem, I thought, the objective can be converted.

´The prism can be removed, then a T2 (M42x0.75) internal thread is available for further adaptations´.

However, removing the prism does not reveal the expected T2 female thread, but an M28x1 thread to which the Amici prism is screwed. This small opening may explain the vignetting. In the description I found no hint how to get to the T2 female thread. There are three grub screws on the part, which also has a silver clamping screw to align the prism. If you loosen these, the retaining ring comes off and exposes the T2 female thread. If you now screw in a T2a-T2a adapter with a continuous male T2 thread, you get the situation shown in the third picture. The picture says: ´Anwendungsbeispiel´.

Since the Amici prism is connected via the M28 thread and the helical focuser is also attached to the prism with such a thread, it cannot be used for T2. For focusing you need a helical focuser with male T2 connection thread at the telescope side, e.g.: TSHeli1 for currently 59,90?, as described in the text."

We thank the customer for this informative report and have added to the store presentation.

Question:
How can I best adapt my autoguiding camera with T2 connection to this guide scope?

Answer from Teleskop-Service:
It is very simple and a pure calculation example. The distance from the T2 internal thread on the finder to the focal plane is 90 mm. Exactly in this distance the camera sensor must be brought.

Calculation example using the ASI290MM - distance from the T2 internal thread of the camera to the sensor is 12.5 mm:

90 mm minus 12.5 mm is 77.5 mm - this distance must be bridged. A good way is for example (from finder to camera):

T2a-T2a ... T2 thread reversal, turns the T2 inner thread into a T2 outer thread

2x TST2V26... T2 extension with 26 mm length ... makes 52 mm

TST2Vvar ... variable T2 extension tube from 20.5 mm to 30 mm

Then just connect the camera and the exact focusing is made simply with the variable tube. You only need to do this once.


Question:
How do I get to the T2 internal thread of the viewfinder?

Answer from Teleskop-Service:
It is actually a little more complicated to get to the T2 thread.On the tube, where the knurled screw is, with which you can rotate the prism, there are 3 more recesses with grub screws. Please loosen the knurled screw and unscrew the 3 grub screws further. Then you can remove the attachment with the external thread for the prism and you will come to the T2 internal thread on the tube for individual adaptations. The 3 screws fix the position of the rotation adapter.