Sun, 05/18/2014 - 20:12
There is a nice EE Cep campaign website for the August 2014 eclipse now up!
https://sites.google.com/site/eecep2014campaign/
Right now there is not much photometric coverage from the western hemisphere. And near infrared observations before, during and after eclipse would be really valued. Absorption lines from shell material could be detected months before eclipse (and that's right now!).
Not mentioned on the web site is the prediction (by Galan
et al. 2012's) that the 2014 eclipse should be a deep one compared to the last two. Two groups will be trying to see if it is possible to detect molecules in absorption during eclipse.
AAVSO Alert Notice 502 has been posted, requesting observations of the Be star EE Cep beginning now in order to observe its upcoming eclipse. Please see the Alert Notice for details.
Good observing,
Elizabeth Waagen, AAVSO HQ
I would be happy to contribute to the observations of EE Cep throughout the eclipse, but am not experienced at doing transformations. I am using a scope on iTelescope.net, please let me know if untransformed observations are still of value, or if not, I would love to speak with someone about what I need to do to calculate transformation coefficients for the scope and location that I am using.
Thanks -- Brian
Brian,
If you look at the observations, the majority are going to be untransformed. So you can submit untransformed observations. But this would be a good time to obtain transformation coefficients. Fortunately, the AAVSO is working on two programs now that will make it easier to obtain your transformation coefficients and apply them to your observations. The two programs are called Photometry Transformation Generation Program and Transform Applier. The Photometry Transformation Generation Program requires you to image standard stars in M67 or NGC 7790. Unfortunately at this time of year M67 is not available but NGC 7790 is available. It requires obtaining the instrumental magnitudes of some stars from one of those clusters and the program will generate your color transformation coefficients. You then place those coefficients into the Transform Applier program then open a file of observations that you obtained from EE Cep for example. The Transform Applier program will then generate a report of the transformed magnitudes of your observations. You can get started and download the programs by going to this page:
http://www.aavso.org/transforms-everything-you-need-transform-your-ccd-…
Barbara
Hi Brian
You can find a list of the transformation coeff. on the pages of some telescopes, such as iT11 and iT21. But I'm nor sure, how to use them in VPhot. Maybe it's very simple ....?
Raymond
You might inquire if the iTelescope system you are using already has transform coefficients available. These characterize the scope and I would think a commercial scope would have them available along with extinction coeffcients for the site. Worth asking.
With coeffcients in hand then all you need is your observations worked up for submission to WebObs. The TransformApplier takes these to things as input to create a new file ready to submit to WebObs with the transformed data.
George
Thanks all for the responses, and Raymond I am using T21, didn't realize they posted coefficients on the telescope page...excellent!
The eclipse of EE Cep appears to be gradually getting underway.
Also, if you use COUSINS R and I filters, be sure to use COUSINS R and I magnitudes to reduce your data!! Do not use the Johnson R and I magnitudes given by Galin et al. The Cousins values are in the AAVSO Photometry table for EE Cep.
If you have already submitted R and I data, please check your files to be sure you used matching filters and comparison magnitudes. If you did not, please delete your observations, re-reduce them correctly, and resubmit them. If you need help with this, please contact us.
Please see AAVSO Special Notice #387.
Many thanks, and good observing!
Elizabeth Waagen, AAVSO HQ
Hello
According to Samolyk and Poklar, JAAVSO 37, 2009; the TOM of EE Cep occurs on JD 2456890.83 or thereabouts. Its about 2 weeks away. Good time to start, if you have not already. The irregularity on the decending light curve may show up in about 8 days, if it occurs at the same point at 2009. Keep those observations coming.
WGR
Till now, I mainly used V-filters. I thought, that the EE Cep campaign would be a good opportunity to learn using different filters. But now, I have some data but am quite confused on how to process them correctly.
I made my observations with telescopes from itelescope. I try do make a V-observation every second or third day ; and from time to time an observation using B, V and R filters. The filters used at T7 are Johnson-filters.
Here is an example of my results using T7 (Spain) (from 14.07.2014)
As there are used Johnson-filters at T7, I created the sequence manually using the Johnson magnitudes for the stars 104 (a), 112 (b) and 113 (c) (a and c used as comp. stars – b as check star).
First, I determined the magnitudes (VPhot) without using any transformation. The results for EE Cep are as follow:
V: 10.817 +/- 0.006
B: 11.159 +/- 0.006
R: 10.436 +/- 0.010
Using the Transform (Two-Color Photometry)-Tool from VPhot, I got the following results (transformation coeff. known for telescope):
a) for color index B-V:
V*: 10.801 +/- 0.002
B*: 11.160 +/- 0.007
b) for color index V-R:
V*: 10.792 +/- 0.002
R*: 10.407 +/- 0.004
a) I was surprised to get different values for the V-magnitude (thought, that there were not affected by transformation). What magnitude should be reported for the V-filter, as I get three different values (or are the errors strongly underestimated?).
b) I get a rather bright R*-magnitude (10.41). Most of the recent reported magnitudes are less brighter (about 10.56). So I have some doubts, that my procedure is not quite correct.
I did the evaluation also using the magnitudes from the AAVSO-comp. stars (although they are not Johnson-magnitudes). V- and B-magnitudes are slightly dimmer (0.02 mag); with a larger difference for the R-magnitude. Results are in the attached file.
Thanks a lot for any assistance
Raymond
Hello Raymond
Your corrections to go from Standard Magnitudes to Transformed magnitudes should be small, but not zero. You should get a small difference in V, as well as B, R and I.
I suspect that your R magnitudes are Johnson R and the ones you see on the LCG are Cousins R. There is small difference.
Gary
I notice quite a wide spread in the recent visual estimates using LCG. From 10.5 - 11.5 roughly. This is very poor, and I would encourage the visual estimators to take exceptional care and try to improve their accuracy. Defocussing may be helpful.
Also, the sequence is somewhat wide for accurate visual, right now 104 or 106 to 112 is bracketing the variable, but that is a bit too broad to really allow careful measuurements to 0.05 magnitude.
Mike LMK
Hello Michael
I too was surprised at the Visual scatter on this object. I also thought it would be better.
Perhaps some of the problem is that 112 and 113 are suspected variables? Their range was supposed to be small, but perhaps not. For the CCD observations we settled on all using the 104 as the Reference and the 119 as the Check. If the 112 and 113 is eliminated, that makes the 119 the next option, and its a long way from the 104 in position and in magnitude.
This may account for some of the difficulties. Other suggestions?
Gary
Hello
I looked at the Vis Estimates to see if I could see anything systematic that would be causing the larger spread. I have attached a plot that shows all the data with the large diamonds and the edited data, which overlays the edited data in small solid diamonds for comparison. There were 71 Vis observations and Editing consisted of the following:
1. 8 observations had only one comp star listed, so they were edited.
2. 4 observations with a 109 comp star, that I could not find on any chart, C, D, or E, so were edited.
3. 6 observations using chart "K", so were edited
4. 2 observations using 107 comp from the "DPV" chart, so were edited
Since these were non standard, or unusual, it was hoped that they would be the outliers. From the chart, it did not seem to help much. I will post a chart on the NSV842 and NSV843 later.
WGR
Hello Gary,
I now have more than 20 DSLR observations of EE Cep, since July 14 and I don't see any specific scatter of 112 and 113 mag. I have made a search in Simbad / Vizier and don't see any NSV reference for those stars or in a 10' radius around EE Cep. Are we sure 112 113 are in NSV ?
What are NSV 842 and 843 ? In Vizier they are far from our field and have very different mag than 112, 113.
Clear Skies !
Roger (PROC)
The 112 and 113 were listed in VSX as potential variables. We steered clear of them for the CCD campaign.
I have 4 nights of time series on them, and one night showed .05 mag variation, but the other 3 nights were much less than that. I will post the plots when I get back to the observatory computer in a few days. I did not see anything that should account for the scatter in the Vis Observations.
Gary
Hello
NSV 25842 (aka 112) and NSV 25843 (aka 113) both show up in AAVSO charts D, E, F, and G for EE Cep. That was where I first learned of them. If things stay as they have been, should not be a problem. Hopefully they will not go into activity before the end of this campaign.
Gary, WGR
Hi Gary, Roger,
Both NSV 25843 and NSV 25842 are listed as CST (constant) in VSX. Looking at the light curves (actually two widely separated clumps) and considering the uncertainty in the measurements I don't see a problem using them.
By the end of this campaign we'll probably have a pretty good idea if there is any variation in these stars over the course of the eclipse. For observers using VPhot I'd expect the "VS Search" tool to give a good indication of variation in these stars without any extra analysis.
Of course if it turns out either of them varies during the eclipse the measurements for EE Cep could be re-calculated later to exclude the offending star.
Phil, spp
Hello Phil;
Looked on VSX again, and you are right, they are listed as CST. The definition is given as "CST Non-variable stars (constant), formerly suspected to be variable and hastily designated. Further observations have not confirmed their variability.
So I am guessing before the campaign, they were listed as suspected variables, and have been "Hastily Re-Designated.
The orginal question Posted by LMK was why the scatter in the Visual Observations was higher than expected in EE Cep. It was suggested that the 112 and 113 might be the cause. I looked at 4 time series, about 230 data points, over 4 nights, and saw no variation larger than 0.05 mags in NSV 25842 or NSV 25843 relative to the 104 Reference Star. This should not affect the Visual Observations. There must be some other cause.
Gary
[quote=WGR]
The orginal question Posted by LMK was why the scatter in the Visual Observations was higher than expected in EE Cep. It was suggested that the 112 and 113 might be the cause. I looked at 4 time series, about 230 data points, over 4 nights, and saw no variation larger than 0.05 mags in NSV 25842 or NSV 25843 relative to the 104 Reference Star. This should not affect the Visual Observations. There must be some other cause.
[/quote]
The variation between observers in visual is still around 0.2 mag or more. But, it seems to be a little improved lately, since my prior post. The small number of visual observations is the real problem. The "law of large numbers" is not helping us at all!
Mike LMK
Hello Michael
I agree that things look better since your post. In addition, when I dug into the issue after your post, I did notice one thing. While I am not a visual observer, I don't think that I saw many of the "regulars" posting data other than yourself. Most seemed to be names I was not familiar with--which is good--as it may mean that we are getting some new observers.
Gary
[quote=WGR]
While I am not a visual observer, I don't think that I saw many of the "regulars" posting data other than yourself. Most seemed to be names I was not familiar with--which is good--as it may mean that we are getting some new observers.
[/quote]
Gary, I agree, its great we seem to be getting more "new" observers joining in this campaign. However, where are the seasoned visual observers? This would be a great opportunity for the good, experienced visual guys (and gals) to show what visual can really do, if sufficient numbers of accurate observers can contribute!
Mike LMK
Observed EE Cep last night, still fading. Looks like the decending bump was observed by AAVSO observers, and clearly shows in the light curve. The predicted TOM min is Wednesday, upcoming week. (JD 6890) Mark your calendars.
Gary
I have measured EE Cep on 24 nights since July 10 UT, using 104 as comp and 113 as check. I have seen no variation in 113, but do not get perfect agreement with the 113 numbers in the photometry table. For the V mag, I get a mean of 11.252 for the 24 measurements, very close to the listed value of 11.251. But for the B mag, I get a mean of 11.502, a bit dimmer than the listed 11.491. And for the I mag, I have 10.890, which is 0.017 mags brighter than the listed 10.907. Are these differences to be expected, or do they mean my transformation or extinction coefficients are not correct? My std devs for the 24 measurements of star 113 are 0.0052, 0.0047, and 0.0038 for the V, B, and I mags respectively.
John Centala, CQJ
Since the error associated with APASS magnitudes is about 0.03, your data is excellent!
Ken (MZK)