Tangsinuo U-Venus filter

[aphalo]

Last month I noticed "UV Pass Filter for Venus Photography" listed in the Tamgsinuo pages at AliExpress. I ordered one in 30.5 mm size for 59€. It arrived last week. It is an interference filter with a different coating on each surface, the reflections looks rather different to the BaaderU. I did a preliminary measurement with the old spectrophotometer in the lab at work, but the very old PC refused to let me download the data (dirty head in the diskette drive, most likely). So I only have the spectra photographed with the phone. To me UV transmittance looks very good, but it does leak IR at around 750 nm, and a bit at near 900 nm. The drop at the right end of the curve starting at around 1000 nm is not an IR leak but the limitation of the spectrophotometer as it looks exactly the same with different filters, the OD 4 roof is also a limitation of the old Agilent 8453 diode array spectrophotometer.

 

Once I get the diskette drive cleaned (cleaning diskette ordered yesterday) I will post proper plots.

 

Plot at the top is spectral transmittance (%) and plot at the bottom  is absorbance (= OD) from the same data.

 

 

[Stefano]

Used alone, this filter will leak. OD 3 at 750 nm is not enough blocking. You could either stack two of them or stack it with some ZWB1-type glass. 

[Stefano]

About filters in general, they might make UVB and UVC bandpass filers on request, just like they made the 8 mm thick ZWB1 filter. Maybe they could make a UVC bandpass filter centered at 254 nm with good IR blocking, which could work alone or stacked for UVC photography. Lukas has interest in this.

[aphalo]

Stefano. Yes, I agree. However, I do not want to rear-mount a thick filter stack. I will try this Tangsinuo Venus filter together with a ZWB1 on the flash head (and good eye protection).

[Stefano]

I think you could get contamination if you photograph strongly fluorescent objects such as paper or highlighters, otherwise that combination should be OK.

[dabateman]

I order one of these years ago when he first made it. Mine leaks more IR than this. Not usable on its own. 

The 470 narrow band pass I ordered at thesame time was better. But its obviously not used for UV photography.  I used it to isolate the 488nm band for fluorescence.