ZWO ASI178MM-cooled – UV imaging (part 2)

Having tested the ZWO ASI178MM-cooled for UV imaging, and found that it is very capable for such invisible band imaging, I decided to take it to the next level of testing to see what are the limits to its capabilities. My subject is the more well known Dandelion flower which I had picked from my back garden. This flower has been imaged many times in UV, so it is sort of a reference flower for UV imaging.

First photo was taken with my Olympus E-M5, Coastal Optics 60mm F4 @ F11 using the Quantum X4D as light source, to show the dandelion in false UV colours.

Shot with Olympus E-M5, Coastal Optics 60mm F4 @ f11, Baader U & Quantum X4D
Shot with Olympus E-M5, Coastal Optics 60mm F4 @ f11, Baader U & Quantum X4D

I previously did not manage to get a good shot of the ZWO ASI178MM-cooled from the back. Because of the crop factor of the imager, I do have to move the camera fairly far from the flower (near the edge of the worktop furthest from the flower).

Setup to image Dandelion
Setup to image the Dandelion

Below I have included the questions I was asking and show you the answer in the photos that I took as a result.

Q1. With the weak UV from the fluorescent tubes of my indoor studio, can I do UV-imaging with this camera?

Answer: Yes. With the gain of 100 and 5 seconds exposure it is possible to image in UV using the weak fluorescent lighting from my indoor studio.

5s exposure @ Gain 100, using Baader U and fluorescent indoor studio light @ F4
5s exposure @ Gain 100, using Baader U and fluorescent indoor studio light @ F4

Q2. What exposure will be required to image in UV using 365nm UV torch?

Answer: With 2 Nichia-chip 365nm UV torches (one on each side) and gain 0 & F5.6 aperture, I managed to capture the image below using 0.08s exposure. Using Gain 100 would result in a much faster exposure time.

Shot 0.08s @ Gain 0, lit by 2x 365nm UV torch
Shot 0.08s @ Gain 0, lit by 2x 365nm UV torch

Q3. Can this imager capture into deeper UV i.e. 320-330nm?

Answer: Yes it can.

I used 330AF20 and 325BP10 filters stacked together to get the images below; the reason to stack is that there are some areas where the dichroic coatings have come off from the 325BP10 filter. I used Gain 100 and the Quantum X4D as light source.

325BP10 stacked onto 330AF20 filter
325BP10 stacked onto 330AF20 filter
Imaged with 325BP10 stacked onto 330AF20 (between 320-330nm)
Imaged with 325BP10 stacked onto 330AF20 (between 320-330nm)

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