New generic Venus Filter

[JMC]

Found myself looking at filters recently, and came across a post which had some data from the Astrodon UV filter - https://lco.global/observatory/instruments/filters/astrodon-uv/

 

This looks to be measured data, and not from the manufacturer and goes out to 1200nm unlike a lot of the graphs.

 

I guess this is the previous version of the filter, has anyone tried the Generation 2 one?

[Andy Perrin]

The infrared part of that graph seems suspicious, with that huge jump in the lower graph. At 800nm should we trust the data on the left or the right? Because probably one of those is incorrect.

[JMC]

Two spectrometers maybe Andy, one below 800nm and one above. Granted, not ideal, but would account for it.

[Andy Perrin]

For sure, but which one is giving the correct values for the blocking? Or maybe neither? It's not just off by a little, it's off by a factor of 10 or 20.

[Stefano]

I'm guessing the 800 nm+ one is the most correct as it is the least noisy. But the other one has noise in the entire UV-VIS-IR range, and that jump is strange.

[dabateman]

I would follow that 10-4 curve down to 700nm. That also looks reasonable based on Enrico's images for similar filter.

 

Clearly different light sources were used and different instruments.

[ulf]

I'm guessing the 800 nm+ one is the most correct as it is the least noisy. But the other one has noise in the entire UV-VIS-IR range, and that jump is strange.

I would say the opposite. I think this is a composite graph from two spectrometers or measurement settings.

For an array spectrometer like the one I have it would be very difficult to get that spectrum range from 200nm to 1200nm.

 

The noise Stefano is disturbed about is likely from the detection of the instrument. It is at OD6, where it is quite OK to see some noise.

Possibly some more integration and intelligently chosen averaging might smooth out and lower that noise level even further.

 

The least trustworthy part of the graph is between 800nm and 1000nm.

The part above 800nm is clearly measured to show the worse OD at the upper wavelengths only.

It might be that the instrument used for this part cannot measure such deep OD as used for the first part.