TS Optics 71SDQ review

71SDQ first look

TS Optics 71SDQ quadruplet refractor is somehow new product targeted mainly for portable astroimaging. It seems to be successor of well known quadruplet 65Q, and since their basic parameters are very similar, it may be also considered as a direct replacement for 65Q.

Parameter	TS 71SDQ	TS 65Q
Aperture [mm]	71	65
Focal ratio	1/6.3	1/6.5
Focal length [mm]	450	420
Instrument length [mm]	370	340
Instrument weight (with rings) [kg]	2.5	2.8

According to manufacturer this instrument is equipped with air spaced front aperture lens made with FPL-53 glass. Front lens does not have collimation screws, but for quadruplet with integrated flattener it is understandable – there is not much the end user can do here to adjust optics collimation. The distance between optical elements (second one is inside tube near to focuser) and its relative positioning must be set with good accuracy.

Refractor is pretty compact, when dewcap is retracted it is only 37cm long. It is also quite lightweight, but due to its small size it seems to be little bit weighty. Lens hood can be pulled out, but not much, about 5-6cm only. CNC made tube rings are of good quality, and there is also short Vixen style dovetail included.

Focuser

Focuser in 71SDQ quadruplet is standard TS Optics rack&pinion model with 2.5 inches diameter. It is pretty good quality and should be perfectly enough for imaging with DSLR camera or small and medium sized dedicated astrocameras. Focuser tube travel is about 55mm. There is 360 degrees rotator at the end of the focuser tube. It is pretty stiff and there is no visible play in this element. Rotator from the camera side is ended with standard M61x1 thread that holds reduction to 2″ and to 1.25″ holders, so you can basically attach any standard accessories you have. One thing worth to mention is that bottom side of focuser shaft cover is not flat, but fancy shaped, so standard adapters to focusing motors will probably not fit that.

Focuser maximum travel is 55mm and this is too short for example to catch focus with DSLR using only 2″ or T2 adapter ring put into 2″ clamping ring. You may order special adapter attached directly to M63x1 thread, or use at least 15mm extender.

Quadruplet 71 SDQ under the sky

TS Optics 71SDQ quadruplet refractor on AZ4 mount — Refractor put onto AZ4 mount looks quite tiny

I have caught two hours of clear skies, although the Moon was shining pretty high then. At start I put 24mm ES 68 degrees eyepiece (19x power) into 2″ dielectric diagonal. The views offered by this instrument were very pleasant. Stars were pinpoint, star clusters were well defined, and star colors were easily distinguishable. Trapezium in M42 at this low power was separated to four components. After changing eyepiece to BCO 10mm (45x power) the view of M42 was much better, because background has been darkened and amount of detail increased. At this power Castor double star (separation 5″) was already seen as double star. With BCO 6mm eyepiece (75x power) Castor was completely split to two components. Slightly defocused stars presented clear diffraction rings, and when defocused more, the stars images were uniform discs of light. See below – defocused images of 25um artificial star.