giving magnitude estimates on forums

Tue, 12/03/2013 - 13:00

Dear Folks,

I have a question. I have noticed a fair amount lately that observers have been giving their magnitude estimates of a variable, like a nova. I was taught for 30 years or so that we should never share our estimate with another observer so it doesn't bias them. In other words, let's use an example: You go out and observe a supernova at 10.9 magnitude. You immediately post it on a forum, and then others very soon after go out to observe that supernova. Let's say they see it at what they think is 11.6, but they know that you observed it in the past few hours at 10.9. Not everyone, but several people are going to think that that observer, who has been doing variable star observing for a long time, must be more accurate than me. So, instead of 11.6, they stare at the variable for a longer time, and second guess their first estimate, and change their observation to 11.1. That's bias coming into play.

I'm just curious to think of what people's thoughts on this. I NEVER look at other very recent observations. I want my own unbiased observation, even though it may not be as accurate. However, there's the chance that mine may be more accurate than the ones a person or 2 or 3 have posted. What's your thoughts on this matter?


PS: I've been going through quite a change in life this past year, so if you haven't heard from me, it's not because I've disappeared. I'm in a place where I cannot even use my telescopes (NOT prison, so don't worry:). I'm hoping to move to a nicer location so I can use my telescopes. Be patient, I'll be back up and running as soon as possible.


Chris Stephan  SET

Burton, OH

American Association of Variable Star Observers (AAVSO)
Bias issues

Hi Chris,

You bring up a discussion which happened before on the old mailing list, I believe. Yes, bias is a possibility with visual observing. I always avoid checking on precise magnitudes of objects before I observe them. However, a rough range of where an object might be, is perfectly ok, I think. Its probably impossible to prevent estimates from appearing on this or other websites, even the official announcements and campaigns contain magnitude estimates.

So, all I can suggest, is to avoid checking on precise magnitudes before visually observing anything, and do your best to just estimate the objects as you would normally do.

Mike LMK

PS. Hope you can get out of your terrible observing situation ASAP...Good luck.

Magyar Csillagaszati Egyesulet, Valtozocsillag Szakcsoport (Hungary) (MCSE)
In Hungary on the [mira] list

In Hungary on the [mira] list of HAA/VSS we usually give only a 0.5-1 mag range writing about our own estimations: eg. "Nova Del 2013  between 11.0-12.0 magnitudes"

Clear skies,