Skip to main content

Should we mention our magnitude estimate of a star on the forum?

9 posts / 0 new
Last post
SET's picture
Should we mention our magnitude estimate of a star on the forum?


I've noticed for the past few years on the former Discussion Digest and more recently in a few of the forums (not necessarily ours) that people will report their magnitude estimate on a star from their most recent estimate, possibly evens hours old. It used to be that if we mentioned our estimate that we would be gently rebuked NOT to give our estimate because it will bias other observers.

What are your thoughts on this? Is this a change in thinking throughout AAVSO, or should we be careful not to give any tips on the estimate of the star?

For example, let's just says I put a post on the forum tonight that SS Cyg is 9.1 magnitude. Now let's say an observer, especially not as an experienced observer read that. They go out to look at SS Cyg, and say "Oh Ya, I estimate it to at 9.1 or 9.2". John Bortle may look and get it at 8.6, or he may even find I screwed up and SS Cyg is still at minimum, around 12.2. I just caused some observers to send in erronious data into Web Obs.

See what I mean? I'd like to hear your comments on this. Perhaps we could give safer comments like "SS Cyg seems to be brightening". That will stimulate observers to go out and look, yet not automatically think that Stephan is an experienced observer so his estimate must be pretty accurate.

We never want bias in science.

The reason I brought this up is because I saw this exact thing on another forum post today. Is it acceptable now? I want to make sure us visual people do not get biased. Let me hear from you. Thanks.


Chris Stephan

Robert Clyde Observatory

Sebring, Florida  USA

paw's picture
mags on forum

I think it goes to need. If ETA Car were to be mag 2.0, I'd post it! But there is not usually any need to mention mags on a forum.


PKV's picture
Magnitudes on Forums

I assume that all reported magnitudes made by others are "wrong" and I independently try to make the best estimate of what I "see."  Hence, I have no issue with quoted magnitudes.  I may be "wrong" also, but reporting what you "see" is the most important thing.  Its hard to believe that individuals would be influenced by the estimates of others, given the scatter and uncertainty that exists in most visual light curves...  Kevin - PKV

SXN's picture
Reporting magnitudes and biasing observations

As a general rule, I agree with Chris that it is better to be descriptive but not quantitative when discussing recent visual observations with other visual observers. You do run the risk of influencing others who don't have the confidence to report what they see, not what they think they should be seeing.

I've seen it happen with R CrB, where some observers kept reporting it at maximum even though it had obviously begun to fade. If you think its going to be 6.1 tonight, you are likely to see that regardless of what you actually see in the eyepiece.

That said, and giving a nod to the old conventional wisdom, I don't think this is necessarily the best policy all the time nowadays. The fact is, if I or anyone else wants to know what the most recent observations of a particulr star are they can easily access that information via quick look, the light curve generator, or the WebObs search feature. I can call up all the SET observations going back 90 days at any time from the AAVSO website. I for one am not willing to give up access to up to the minute information in hopes of not influencing lesser confident observers. The fact is, we exist in an era where digital detector observers are quite willing to discuss their most recent results to 0.01 magnitudes in real time. Holding back information to avoid visual bias makes visual observers look lame and unreliable in contrast. I know that is not true.

I can think of some specific instances where I have reported the estimate I made for good reason. #1 would be if I had some question about what I saw and had compared it to others and found a discrepancy. Maybe the sequence has a gap in it and I'm wondering if this has affaected anyone else. Sometimes we are involved in revising a visual sequence because of color issues, but there are no terrific alterntives. All the potential comp stars suffer from being too red or having questionable photometry. I have a select few observers who compare results to determine if we are actually making an improvement in the sequence or if there was a real issue in the first case.

V426 Oph is a current example of this. It seems no matter what we do we are gonna make someone unhappy because all our choices are red to some extent, which is a bummer when trying to observe blue stars. Happily, our recent visual results match with the CCD data to within 0.05, so we are on the right track.

So, to answer the question, I think it is better to say W Her is near minimum and not report an actual estimate, but if I or someone else does say, " I saw it at 13.2", I don't trust them anyway, even if they are a CCD observer. I want to see it or measure it for myself. I assume everyone else is wrong and I am right. It's part of my 'Simonsen's Rules For Visual Observers' which I wrote for Citizen Sky some years ago.

Credit must be given to my mentor, Gene Hanson, for much of the content, attitude and overall outline of this post.

lmk's picture
  I suppose this thread


I suppose this thread began because Chris noticed the post about RU Peg brightening on the recent forum topics. While I am generally in agreement with SXN about this isssue, its a complex one and there are clearly two sides to this story.

But, I think this is a special case because RU Peg is a current active campaign star which needs to be caught right at the beginning of its outburst. I think that tends to weigh in favor of posting any relevant observations immediately to catch people's attention!

However, it may not have been necessary to put the 12.4 magnitude in the title and have it pop up at the top of the front page?! But, even that is debatable...

I generally believe that actual magnitudes shouldn't be actively posted. They are in the AID, and anyone can see them via QL, LCG, etc., so maybe not in the title. But there are always reasons why it might be ok, such as this case of RU Peg, where the star is rising very very near to the trigger value of 12.3!

Mike LMK

BRJ's picture
Should We Mention Magnitude Estimates...

Another interesting topic and again one steeped in history.

The question of whether, or not, magnitude estimates should be posted/published in near real-time goes back a long way in AAVSO. Director Margaret Mayall had always been concerned with the influence publishing magnitude data might have on observers and was, at least initially, highly concerned about the instituting of the AAVSO Circular even with its 30-day lag-time in information.

Now I'll be the first to admit that posted data can influence individuals, and even from a darker motivation involve perhaps a handful of odd folks to actually copy and submit such data as their own. This was something I witness a few times over the course of 30 years as Circular editor.

Director Mattei was a bit troubled when AAVSO and associated variable star observational data made its entrance into the Internet and she and I had several discussions concerning it. But nowadays, with observations appearing on multiple forums and sites virtually in real-time, the potential for influence and fakery has yet again dramatically increased.

However, the reality was that the cat has been out of the bag by then and today, even just considering things from our own in-house sources (CVNET, QL, LCG, etc. plus so many others outside) information regarding what stars are doing night-to-night is visible at a glance 24-7.

The concept of the today's observers making absolutely independent magnitude estimates every time, whether visually or even via CCD, it highly questionable in my mind from what I've witnessed. For that reason, I would doubt that occasionally posting a magitude here, particularly when it is employed to illustrate an unusual event occurring, probably isn't overly harmful to the majority of folks.


SET's picture
Great comments


This has been a great discussion so far. Some of your thoughts, frankly, have never occured to me, and they are great thoughts. This is why I like the forum, I am 56 years old and still learning. Keep those comments coming in.


Chris Stephan


MDAV's picture
A little late to this thread.

A little late to this thread. I would give a couple of conclusions. 

1. As a general rule don't use the forum as an ersatz webobs. 

2. Common sense rule- post the magnitude if there is a reason to.   There isn't much point in telling us SS Cyg is in outburst at 10.2 or  R CrB is at 12.1 but letting us know GK Per has gone into outburst (does so every three years or so and due anytime) at 11.9 or Z Cam has come out of a standstill at 10.5 (it hasn't) has some value-bearing in mind that the important point for forum purposes is the change of state and not the precise magnitude.

I promise not to get too out of sorts though if someone does. Of course I'll cut a FNG more slack than I would those of us who know better. 

TYS's picture
I have no problem with people

I have no problem with people mentioning mag estimates. If I know I'm going to observe a certin variable I will not look up or read anything about until I made my own mag estimate. I won't check a variable till I sent in my observation.

Log in to post comments
AAVSO 49 Bay State Rd. Cambridge, MA 02138 617-354-0484