<p>Comments on <a href="https://astronomy.stackexchange.com/q/34482/7982">Why do these photometric observations of Betelgeuse look “quantized” in 0.1 magnitude steps?</a> suggest that these are visual estimates, mostly (but not all) to 0.1 magnitude resolution.</p>

<p>Are there any designs for simple photodiode-based amateur photometers for stellar brightness measurements? </p>

<p>Just as an illustration of the kind of thing I'm asking about, I'm imagining a pair of binoculars with a 1 mm photodiode suspended by its wires the focal plane of one eyepiece, and a Raspberry Pi recording the photocurrent (with a small amplifier) and audio simultaneously ("I'm now measuring xxx... mark!") The data would be jumpy but presumably would reach a plateau whenever the star fell on the active area of the diode.</p>

<p>Or is this too impractical and not backwards-compatible with existing data?</p>

CC BY-SA 4.0
2019-12-26T23:38:31.737Z
It might be easier and more accurate to take photos of the variable star and its surroundings.  Then, you could also compare the brightness of non-varying stars to calibrate your reading, so that a night of poor visibility doesn't skew your results.
Ghedipunk
CC BY-SA 4.0
2019-12-26T23:42:04.177Z
@Ghedipunk sure, if it works well that would be a great example and answer. I guess you have to spread the light out over enough pixels so that the missing light in the gaps between them averages out, perhaps a small defocus... The pinhole + photodiode (or just pinhole-sized photodiode) wouldn't suffer that particular problem, but then there's the problem of nearby objects that imaging might handle better.
uhoh
CC BY-SA 4.0
2019-12-26T23:43:56.493Z
Or, (assuming you're not observing Polaris) use a non-tracking tripod and a long exposure.  The Earth will take care of spreading the light out across a few pixels.
Ghedipunk
CC BY-SA 4.0
2019-12-26T23:47:45.020Z
@Ghedipunk bingo, that works! [slightly related](https://space.stackexchange.com/a/38797/12102)
uhoh
<amateur-observing><photometry>
Are there home-brew photometers for amateur observing of variable stars and are they widely used?
uhoh
# Are there home-brew photometers for amateur observing of variable stars and are they widely used?

(Asked by: username_0 on 2019-12-26)

Comments on [Why do these photometric observations of Betelgeuse look “quantized” in 0.1 magnitude steps?](https://astronomy.stackexchange.com/q/34482/7982) suggest that these are visual estimates, mostly (but not all) to 0.1 magnitude resolution.

Are there any designs for simple photodiode-based amateur photometers for stellar brightness measurements?

Just as an illustration of the kind of thing I'm asking about, I'm imagining a pair of binoculars with a 1 mm photodiode suspended by its wires the focal plane of one eyepiece, and a Raspberry Pi recording the photocurrent (with a small amplifier) and audio simultaneously ("I'm now measuring xxx... mark!") The data would be jumpy but presumably would reach a plateau whenever the star fell on the active area of the diode.

Or is this too impractical and not backwards-compatible with existing data?

**Tags:** amateur-observing, photometry

> **Comments:**
> **username_1**: It might be easier and more accurate to take photos of the variable star and its surroundings.  Then, you could also compare the brightness of non-varying stars to calibrate your reading, so that a night of poor visibility doesn't skew your results.  
> **username_0**: @username_1 sure, if it works well that would be a great example and answer. I guess you have to spread the light out over enough pixels so that the missing light in the gaps between them averages out, perhaps a small defocus... The pinhole + photodiode (or just pinhole-sized photodiode) wouldn't suffer that particular problem, but then there's the problem of nearby objects that imaging might handle better.  
> **username_1**: Or, (assuming you're not observing Polaris) use a non-tracking tripod and a long exposure.  The Earth will take care of spreading the light out across a few pixels.  
> **username_0**: @username_1 bingo, that works! [slightly related](https://space.stackexchange.com/a/38797/12102)  

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## 0 answers

