<p>In <a href="https://astronomy.stackexchange.com/q/43435/7982">Time domain astronomy and fastest eclipsing binary ZTF J1539+5027 (+20 mag, 6.91 minutes) How to measure it&#39;s minimum brightness?</a> I've written</p>
<blockquote>
<p>A logarithmic magnitude scale might tend to show <em>just how deep</em> but noting that the minimum is dimmer than -21.5 mag and probably lasts only a tiny fraction of the orbital period (i.e. a few seconds) makes a good measurement of the minimum quite a challenge.</p>
<p>It seems to me like this might be a situation where a photomultiplier tube and photon counting might be competitive with photometry based on CCD imaging and clever readout schemes.</p>
</blockquote>
<p>This has lead me to wonder more broadly:</p>
<p><strong>Question:</strong> Are astronomers still using photomultiplier tubes for optical photometry?</p>
<p>These include position-sensitive PMTs but excludes other electron multiplication devices like channel plates and image intensifiers. I'm asking about vacuum tubes with one photocathode, a series of dynodes, and an anode where the multiplied photocurrent can be read out either as a DC average level for higher fluxes (possibly using lock-in techniques) or shaped pulse counting for low flux rates.</p>

CC BY-SA 4.0
2021-04-16T23:07:09.540Z
companion question: [Time domain astronomy and fastest eclipsing binary ZTF J1539+5027 (+20 mag, 6.91 minutes) How to measure it's minimum brightness?](https://astronomy.stackexchange.com/q/43435/7982)
uhoh
CC BY-SA 4.0
2021-04-17T14:13:28.717Z
I suspect the answer is something like "Yes, in cases where they're using a small telescope with an old instrument that's never been upgraded but is still working".
Peter Erwin
CC BY-SA 4.0
2021-04-17T14:20:07.987Z
For example, [this recent paper](https://arxiv.org/abs/2103.03972) mentions data taken with the [Tennessee State University 0.4m T3 Automated Photometric Telescope](http://schwab.tsuniv.edu/t3.html), which uses a PMT, from 1997-2019.
Peter Erwin
CC BY-SA 4.0
2021-04-17T14:21:50.463Z
@PeterErwin for [time-structure of optical signals from pulsars](https://arxiv.org/abs/0709.2580) it seems that avalanche photodiodes are now preferred? I guess that's not really photometry though.
uhoh
CC BY-SA 4.0
2021-04-17T14:23:55.497Z
@PeterErwin yes I see what you mean (re. T3)
uhoh
CC BY-SA 4.0
2021-04-17T14:28:42.130Z
How is that not photometry?
Peter Erwin
CC BY-SA 4.0
2021-04-17T14:31:49.390Z
Here's a more recent paper (["Development of an optical photon-counting imager with a monolithic Geiger APD array"](https://arxiv.org/abs/2010.11907)) suggesting that avalanche photodiodes are indeed preferred.
Peter Erwin
CC BY-SA 4.0
2021-04-17T14:50:40.613Z
@PeterErwin re "How is that not photometry?" oh those are actual light curves, so it is. When I used to use PMTs to make time histograms they were just event-counting (think time of flight of nuclear particles). Old habits die hard.
uhoh
CC BY-SA 4.0
2021-04-17T18:53:19.507Z
PMTs and avalanche photodiodes are often used for the exposure meters of high precision spectrographs used for planet finding via radial velocity see e.g. [this paper](https://www2.keck.hawaii.edu/inst/hires/exposure_meter.pdf) comparing 3 systems and [ESO's HARPS](https://www.eso.org/sci/facilities/lasilla/instruments/harps/inst/gallery.html#misc) (search the gallery for 'exposure meter')
astrosnapper
CC BY-SA 4.0
2021-04-21T20:52:34.690Z
@astrosnapper without an answer or an upvote this question will eventually disappear via the [roomba](https://meta.stackexchange.com/q/359901/303080) and even a bounty can't offer more than temporary protection. Would you consider adding a short answer based on your comment? *Thanks!*
uhoh
CC BY-SA 4.0
2023-11-21T20:08:19.307Z
@astrosnapper oh I was wrong, no roomba-ing :-)
uhoh
<observational-astronomy><photometry><instruments><time-domain-astronomy><eclipsing-star-systems>
Are astronomers still using photomultiplier tubes for optical photometry?
uhoh
# Are astronomers still using photomultiplier tubes for optical photometry?

(Asked by: username_0 on 2021-04-16)

In [Time domain astronomy and fastest eclipsing binary ZTF J1539+5027 (+20 mag, 6.91 minutes) How to measure it's minimum brightness?](https://astronomy.stackexchange.com/q/43435/7982) I've written

> A logarithmic magnitude scale might tend to show *just how deep* but noting that the minimum is dimmer than -21.5 mag and probably lasts only a tiny fraction of the orbital period (i.e. a few seconds) makes a good measurement of the minimum quite a challenge.
>
> It seems to me like this might be a situation where a photomultiplier tube and photon counting might be competitive with photometry based on CCD imaging and clever readout schemes.

This has lead me to wonder more broadly:

**Question:** Are astronomers still using photomultiplier tubes for optical photometry?

These include position-sensitive PMTs but excludes other electron multiplication devices like channel plates and image intensifiers. I'm asking about vacuum tubes with one photocathode, a series of dynodes, and an anode where the multiplied photocurrent can be read out either as a DC average level for higher fluxes (possibly using lock-in techniques) or shaped pulse counting for low flux rates.

**Tags:** observational-astronomy, photometry, instruments, time-domain-astronomy, eclipsing-star-systems

> **Comments:**
> **username_0**: companion question: [Time domain astronomy and fastest eclipsing binary ZTF J1539+5027 (+20 mag, 6.91 minutes) How to measure it's minimum brightness?](https://astronomy.stackexchange.com/q/43435/7982)  
> **username_1**: I suspect the answer is something like "Yes, in cases where they're using a small telescope with an old instrument that's never been upgraded but is still working".  
> **username_1**: For example, [this recent paper](https://arxiv.org/abs/2103.03972) mentions data taken with the [Tennessee State University 0.4m T3 Automated Photometric Telescope](http://schwab.tsuniv.edu/t3.html), which uses a PMT, from 1997-2019.  
> **username_0**: @username_1 for [time-structure of optical signals from pulsars](https://arxiv.org/abs/0709.2580) it seems that avalanche photodiodes are now preferred? I guess that's not really photometry though.  
> **username_0**: @username_1 yes I see what you mean (re. T3)  
> **username_1**: How is that not photometry?  
> **username_1**: Here's a more recent paper (["Development of an optical photon-counting imager with a monolithic Geiger APD array"](https://arxiv.org/abs/2010.11907)) suggesting that avalanche photodiodes are indeed preferred.  
> **username_0**: @username_1 re "How is that not photometry?" oh those are actual light curves, so it is. When I used to use PMTs to make time histograms they were just event-counting (think time of flight of nuclear particles). Old habits die hard.  
> **username_2**: PMTs and avalanche photodiodes are often used for the exposure meters of high precision spectrographs used for planet finding via radial velocity see e.g. [this paper](https://www2.keck.hawaii.edu/inst/hires/exposure_meter.pdf) comparing 3 systems and [ESO's HARPS](https://www.eso.org/sci/facilities/lasilla/instruments/harps/inst/gallery.html#misc) (search the gallery for 'exposure meter')  
> **username_0**: @username_2 without an answer or an upvote this question will eventually disappear via the [roomba](https://meta.stackexchange.com/q/359901/303080) and even a bounty can't offer more than temporary protection. Would you consider adding a short answer based on your comment? *Thanks!*  
> **username_0**: @username_2 oh I was wrong, no roomba-ing :-)  

---

## 0 answers

