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Observing campaign on KIC 02856960

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Matthew Templeton
Observing campaign on KIC 02856960

Alert Notice #525 was just issued, detailing a request for time-series observations of an enigmatic multi-component eclipsing binary star.  Observations are needed beginning immediately, with most urgent coverage during the window of 2015 August 8.0 to August 11.0.  Global coverage is urgently desired due to the complex nature of this event; observers in the eastern hemisphere particularly in central and eastern Asia are especially encouraged to participate.

Clear skies, & good observing,

Matthew

WGR
WGR's picture
What comp star(s) to use?

Hello Matt

This sounds like an interesting campaign.  I do have one question,  In Alert #524, it says:

"The AAVSO Sequence Team has assigned a subset of Dr. Marsh's suggested near-field comparison stars for this target that provide a reasonable match to the variable's (g-r) color.  Observers should use these comparisons if at all possible; please clearly identify any and all comparisons used in your report."

Are these the comps that come up in VSP for an (f) X15179I or (g) X15179K charts?  From looking at the ....deneb..... web page, I would say not.  Can you clearify?  The (f) chart has a 131, 137, 136 and 128, 139 that are potentials.  Is the subset of Dr. Marsh's suggested nearfield comp stars available as a "Standard Field".  Where do I find it?

What would be really cool, is if a standard sequence could be set up in VPhot for all of us to use with lots of comps located to use.  Is that what the Sequence Team did?  How do I load that Sequence into Vphot for my use?  

If we really want this PT to line up, I would suggest that we all use the same comps.  This could be defined so that our results are consistant.  Since the AAVSO Comps are located away from the target, one has to offset the frame to get both target and comps.  The choice of comps is required before imaging. 

 

Thanks for your help

 

Gary

Matthew Templeton
Comp stars

Hello Gary,

I'm not entirely sure I understand your question.  The comparisons added to VSP by the Chart Team are drawn from the list of 98 stars suggested by the Marsh team.  The latter, larger list was not fully vetted and includes some stars with close doubles and other issues making them less useful choices.  The subset the Chart Team came up with was more fully vetted, and was also limited simply because 98 comparison stars aren't really needed in VSP for one target.

My understanding is that Marsh's team are interested in time-series.  While they would like to minimize any photometric issues with regards to extinction, I do not think absolute photometry is critical.  Time series from multiple observers are typically looked at individually; since they said clear filter observations are acceptable, they aren't necessarily expecting fully transformed data.

WGR
WGR's picture
Hello Matt So are you

Hello Matt

So are you confirming that the 131, 137, 136 and 128, 139 from pt chart X15179D are appropriate comp stars for this campaign?

Gary

Matthew Templeton
Chart ID not working?

Hi Gary,

I'm sorry, but I'm getting an error when I enter your ChartID.  I don't know why.

I was able to plot a chart using the name "KIC 02856960", and at F-scale, I got the comps you mentioned, along with a 143, 146, and a 152.  The ChartID I got back was 15180DT, which seems to work for me.  These all appear to be the sequence stars that were entered this morning by the Sequence team specifically for this project.  I don't think there was anything else within an F-scale chart for this prior to this morning.

Matt

WGR
WGR's picture
Comps for campaign #525

Hello Matt

I was giving you a Photomotery Table id:  X15179D--not a chart id.    That's what's printed on my PT table.  

The 143 is too far from some brighter options.  The 146 and 152 do not have Ic values.

 

One more question relating to the 600 second net exposure time.  What is the definition of Net Exposure time?  Does that mean a 600 second cadence including the exposure and the readout time?  Confusing?  To me it means 600 second exposures and x seconds of readout etc.  So the cadence would be 600 + X approximately.Is that what is wanted?

Also if doing V and Ic, assuming negligible readout time, is the desire to have a V and Ic every 600 seconds or every 1200 seconds?

THanks

Gary

WGR
WGR's picture
PT Chart ID Bug

Hello Matt

I tried to pull up that PT Chart.  It says it does not exist.  I am using VSP Beta.  This was a bug also in the VSP Days.  You could pull up a Chart with its ID, you could get a PT Table with a slightly different ID, but if you went back and tried to duplicate the PT Table with that ID, it would not work.  Looks like its the same in VSP Beta.

I also tried to get a finder chart using that same id (15180DT) and  got the same error message.  I think if you sign off, or sign in from another account, there is a problem.

Gary 

pastorgalactico
pastorgalactico's picture
Hello; I've been looking at

Hello;
I've been looking at these coordinates with my 12 "
RA: 19 29 31.52, dec: 38 04 35.9 J2000.0 and so far there is nothing close to that point there 3UC257-155253 star with 15.85 Mg according guide9.0

There will have to keep watching what happens.

Cheers;

J.Tapioles

WGR
WGR's picture
Coordinates

Hello J. Tapioles

I am using those coordinates and it is in a 14 x 14 arc minute field centered there.  Suggest printing out an (f) chart from VSP and using that to match your images.  You may wish to sync on a nearby bright star just to make sure.

Gary

PVEA
PVEA's picture
Improved sequences

As is written in the photometric table, all magnitudes of the comparison stars have come from APASS DR9 (No. 29 from Source Reference Table). It is funny why in the sequences are not included SLOAN filters data. I tried to find the data myself but the APASS DR9 access form do not return any data - even UBVRcIc (I tried several of the comp. stars)  – probably the sequence team have different access to the APASS DR9 data.

The life will be funnier if the sequence team include SLOAN magnitudes to the comparison stars when it is possible - it is not requires so much efford since either way, they have got all the data from APASS.

Velimir

jji
APASS DR9

The comparison stars did not come from APASS DR9.  They came from an earlier version and were taken directly from the UCAC4 catalog on Vizier.  You can get whatever SLOAN photometry is available from Vizier.

This sequence is made up entirely of single night APASS photometry.  The sequence team almost never uses single night APASS photometry and then only after Arne assures us that the night in question was photometric.  The data is taken from UCAC4 and is a very labor intensive process. 

In this case the process was complicated by the fact that the comparison stars had to be in the list of 96, in UCAC4 and have usuable APASS photometry. 

If you serve on the sequence team, you will quickly find that the universe is not a perfect place nor is it designed for the convienience of photometrists.

 

 

pbenni
Ic filter results

I tried Ic to compensate for the full moon brightening the sky and got the following magniture (error) estimation with 4 minute images over a few hours using reference star #137 and check star #143:  

14.65-14.70 (0.026-0.033)

Not sure how correct this is as no Ic magnitudes were given for KIC 02856960 or if this tolerance is acceptable.  The star field is crowded so it can be challenging selecting the right star.

Equipment 11" SCT with ST8XME.

Paul

MZK
MZK's picture
Rethinking KID 02856960 Time Series - Revised

Ran a practice run last night (8/1/15) for a duration of about 0.25 JD. Used a 12.5" f/8 reflector with STL6303, each image was 180 sec using a clear filter. Got an average SNR of about 50.

Noise is about 0.05 mag. Saw distinct decline, compared to noise, of 0.1 mag for two images. Only saw one decline (eclipse) which is consistent with period of 0.26 d. Not sure I believe this in terms of reported flux change or duration but there is no similar decline in check. Some slight oscillation possible within noise but not confident? It would be nice for someone to confirm on another night.

Revision - Another all night time series on 8/2 does not show short duration decline shown below. So it is apparently just noise. Run last night was binned x2 (180sx2). Hints at smaller broader declines (0.02 mag) at about the reported period were noted but within the noise. 

Bottom line: for 12.5" f/8 scope need longer than binned 180s (~360s) exposures and good skies to see the faster eclipse with 0.02 mag decline, with a clear filter. Not unexpected! However, some greater likelihood that the expected 0.07 mag eclipse may be seen? Probably will be just outside error band? End Revision.

Ken

WGR
WGR's picture
Trial Run

Hello All

I tried a trial run last night.  Very clear skies--full moon.  10:30 pm to 12:30 pm EST.  24 inch scope--sea level.  Best result was Clr filter, 600 sec exposure, .029 error.  Same filter 300 seconds, .029 to .045 error.  Suspect the sky brightness is starting to dominate, as the errors for this size scope should be lower.  I have never done PT on full moon before.  

What I am going to do, is take 590second exposures (My readout is negligible) with Clear Filter.  Use the 146 as my comp, and 139 as the check--unless I hear otherwise.  Going to be interesting to see how the moon affects the results.  I will use the V values in the sequence. 

Also tried V and Ic.  Results somewhat poorer than the Clr, .052 and .037 respectively at 600 sec exp.

Still not getting .01-.02 mag as requested.  Perhaps on top of a mountain.

 

Gary

 

PVEA
PVEA's picture
APASS DR9

Hi James,

Thank you for the reminder that the universe was not created for the convenience of photometrists what I had begun to forget.

As I am imaging mainly in SLOAN filters I am quite experienced to find the necessary data among the suitable catalogs as SDSS, APASS or even UCAC4 as I usually do. I highly appreciate the entirely volunteer work of the people involved to create sequences and as I know this is not an easy task to be fulfill - my reverence to all of them.

My post was just a reminder that in nowadays a lot of photometrists work with SLOAN type filters. As I have mentioned it is not the case to make the universe more convenient but to make the photometrists life funnier when the SLOAN data exist and they are available in a few mouse clicks. It may not be possible in the case of KIC 02856960 due to lack of data, but it is certainly possible at many other sites.

Velimir

HQA
HQA's picture
APASS/Sloan

Hi Velimir,

I don't think Jim was complaining about your requests.  The sequence team does the best it can with the resources available to it, which, in fact are substantially better than they were only a few years ago.  I consider complaints a compliment, as it means people are using the results from the sequence team and want even more!  The version of APASS that the sequence team uses has B, V, Rc, Ic (the latter two transformed from Sloan r', i').  When APASS DR10 is released, the intent is to back-populate the comparison star database, filling in the Sloan magnitudes as well as 2MASS JHK.  The beta VSP already has the option of printing Sloan magnitudes in the photometry table; the database itself just doesn't have those values yet.

I know that it is a tedious process right now to extract Sloan magnitudes from APASS and other sources for the comparison stars that you want to use.  Hopefully you won't have to wait much longer!

Arne

PVEA
PVEA's picture
APASS/SLOAN

Hi Arne,

Thank you for the comment. You are absolutely right and I really know what tedious work can be to create sequences from different sources. My compliments to all volunteers that make the things happen.  

Actually I am not complaining because the targets that I am imaging have not any sequences in AAVSO database. Most of them do not even have AUID so I have always extracted the necessary data from the different sources by myself. For the targets with temporarily finished photometry I am asking for an AUID to be able to publish the data via WebObs.

The purpose of my reminder is to encourage the observers who wish to use SLOAN type filters but have difficulties to create sequences by themselves. The great step ahead will be when the data from APASS DR10 become fully available through VizieR. The combination with the data from APASS for the targets brighter than 14m and SDSS for the targets lower than 14m will be great improvement for the observers with SLOAN type filters.

Velimir  

 

pastorgalactico
pastorgalactico's picture
Hello; The object in question

Hello;

The object in question which is to look at guide 9 because that name does not appear at all.
I could give its coordinates.

Sincerely;

J.Tapioles

pastorgalactico
pastorgalactico's picture
Hello; Now I have the

Hello;

Now I have the coordinates of KIC 02856960
RA: 19 29 31.52, Dec: 38 04 35.9

Cheers;

J.Tapioles

wluding
wluding's picture
Net Exposure

I would like to reiterate Gary's question about the "net exposure."  Could someone define this so I can try to comply with the request?

My test exposures from last night indicate I can reach a S/N of over 100 with exposures of 600 seconds in my Ic filter and my V filter. IF that is what "net exposure" means then I'm fine.  However, I suspect they really want a cadence that results in data points that are separated by 600 seconds or less. I still might be able to reach this if I only use one filter and reduce the exposure time some without lowering the S/N too much.

Whit

MZK
MZK's picture
Faster the 600 sec

I'm confused why everyone is hung up about the 600 sec reference. Is everyone ignoring the real desire?

"Exposures of 60 seconds are ideal, however, *please note the following*: if you would otherwise combine multiple exposures to create a stacked image with the requisite S/N within 600 seconds, the researchers have asked that you submit measurements from the individual frames instead.  This will give the researchers additional flexibility in averaging your observations together, even though your S/N per measure might be lower than ideal."

The fine structure of the eclipse would be very interesting to observe. However, the depth of the eclipse is small so excellent precision is necessary (i.e., ~ 0.01 mag; SNR>100 or better). A clear filter will allow this more easily but it does not provide the astrophysical info derived from a standard filter (I or V).

Thoughts?

Ken

PS: I assume "net" exposure means image duration and upload time and any other overhead. So repeat images faster than every 600 sec max.

Matthew Templeton
Filters and cadence

Hi Ken & everyone,

I can't speak for the project PIs beyond what's on their website, but my understanding is that they're most interested in time-series in a single filter, rather than multi-filter coverage, especially if it's hard to get the required signal to noise in a single filter within the 600 seconds.  If you are finding it difficult to reach the requested signal to noise in either of V or I individually, I would strongly recommend trying a clear filter instead.  If you can do the photometry in Ic but not V, then do Ic alone without V, and do not worry about getting multiple filters.  I really don't think multifilter photometry is wanted, especially if doing so is sacrificing temporal resolution.  Filters are good because they can constrain the spectrum of the source(s) during the eclipses, but they are less critical than being able to measure the event itself.

My reading of their request is that the maximum time difference between photometric measures in a single filter (or clear filter) should be 600 seconds.  That includes both exposure and readout, so adjust your exposure time downward to account for any readout time.  Again, they're trying to track light curve features that occur on fairly short timescales -- around 1.5 hours.  The shorter the cadence the better.

Matthew

WGR
WGR's picture
Cadence and Clr Cal

Hello Matt and Ken

Thanks for the info.  What I am looking for is some clarity among the options.  

For me, who English is a second language, the Alert lists a 600 second net exposure, V filters, Ic Filters, Clr, SNR 100 ie error of <.01.  The question is what is the priority, which is not spelled out in the Alert.

What I have surmised is the following.  For KIC 02856960 start with an exposure approaching 600 seconds (drive be willing) generate data on less than a 600 second cadence.  Start with the clear filter and see if you get SNR >100.  If you do, try the same in the Ic filter.  If the SNR is > 100, then try the V filter.  If you get this far, then try a V and Ic cadence of less that aproxomately 300 for each, and see if the SNR is > 100.  

Stop when your SNR is no longer > 100, ie poisson errors of .01 to .02 Mags.  This is the best that one can do for this Campaign.  If not able to do this, then submit your images/data for stacking.

 

How do you suggest that we calibrate a clear filter in V?  I would like to know how Ken is doing it, so that my data will line up with his.  Which comp stars?  Method VStar?  Maxim?  Never did a Clear/calibrated in V observation before and just want to be consistent.  No Transformation, Extinction handled by the differential photometry measurement only?

 

Gary

 

 

MZK
MZK's picture
Cadence and SNR

Gary:

My intent is to use a clear filter because with my 12.5", it's the only way I can get a reasonable SNR. I would like to get an SNR >> 100 since the eclipse depth is only 0.07. I tried 180s first and could not see the 0.26 d eclipse with a depth of 0.02 mag. By binning 180s x 2, I just saw a hint of it but not convincing. So I tried 240 sec last night. Haven't looked at data yet. Binning x 2 would yield 480 sec; getting closer to 600 sec.

You may use the 24" on Nantucket so you could go faster than 600 sec perhaps even with a filter!

Yes, it would be nice to use same comp(s) and check. It would help the PI but since he hasn't said anything himself on this forum, he'll get what he gets!  Yea, I guess I could be nicer.  I'll post my comps and check soon. Running CV is easy although not a good as a standard filter but fine for temporal analysis.

I'm just hoping we get a clear night(s)?  AND, hoping that a few more observers (longitude) join the campaign or it will fail since the eclipse is too long for a couple of people.

Ken

PS:  I'm shocked you did not assume I'm using VPhot (VStar??).  I do have bias, darks and flats for my clear filter.

 

WGR
WGR's picture
Be Careful what you wish for

Hello Ken

You wrote:  You may use the 24" on Nantucket so you could go faster than 600 sec perhaps even with a filter!

Well, not exactly.  While I have the 24 inch, I also have very sea level skies here.  FWHM are typically 3 arc seconds.  My trial run for Clear filter showed .029 to .030 errors for 600 secs.  V was .05 mags and Ic was .037 for the same 600 seconds.  So I am scraping for everything I can get.  Coatings are good (<3 years, look shiny).  The Lum images are running 2.7-3.0 FWHM, just a little  better than normal.  Nearly Full Moon was out.  

An open night tonight, clearing trend, hope for better results tonight.  I may just let it run all night.  I get to start at 10:30 EDT.

 

Gary

 

 

Matthew Templeton
Filters and cadence

Good morning Gary,

I'm sorry the Alert isn't clear.  In the body of the alert, third paragraph, there is a line that says

"Only one filter is needed, and observers may take clear or unfiltered data if needed to reach the required S/N in sufficient time"

Taking data in only one filter is ok.  It also says "with the Ic and V filters preferred in that order."  In hindsight, I should have said "Ic filter, V filter, OR clear filter preferred in that order."  That is the understanding I have of the PIs needs.  I wrote the Alert, so I take responsibility for its content.

Regarding calibration, for "CV" (clear, V-magnitude) data, measure the variable and comparison's clear magnitudes, and then calculate the magnitude of the variable using the V-band magnitude of the comp; just make sure you report the magnitude as "CV" rather than "V".  No transformation required; my assumption is that the PIs will be using all observers' out-of-eclipse photometry before and after the main event to establish a zero point for each observer.  Given that unfiltered observations will be used, they will *have* to do that.

I do think it is reasonable to coordinate which comparison star specifically is used to deal with potential differential extinction, so it's ok if people post the stars they use.  We wanted to give several different comparisons since the PIs themselves selected a large number of potential comps with colors that were suitable for their needs.  I don't think there's a huge variation in Sloan (g-r) color among the comps, which is the criterion they used.  We tried to pick the best of theirs, but did what we could to get a good magnitude range close to the variable.

Matthew

MZK
MZK's picture
Comps / Check

Gary et al:

I normally run an ensemble for my comps, but knowing that others do not I have attached a VPhot details page below showing how different the target magnitude is for each of the comps in my FOV. The reddish colors show how far off the target magnitude is for each. The comp which gives the closest magnitude to the average reported target magnitude is the 131  comp. (137 is really close too; I really wanted to use both in an ensemble?) It is also close to the target spatially and has no interfering companions. I used 152 as the check because it is close spatially and also close to the target magnitude.

Any comments on using this comp and check? Note that with 240s and a clear filter I get an SNR of 77.

Ken

FJQ
FJQ's picture
Observing campaign on KIC 02856960

Nice analysis Ken!  Thanks for the clariffication Matthew.

I will start monitoring this star on Tuesday after making sure I got a good standard set on NGC 7790 from my other C-11 set-up;  alas, I only have one set of photometric filters among three telescopes I use (C-11, Classical Cassegrain 13", CDK17"); I'm sure I wont be the only one covering this longitude of 118 degrees on the W. coast.

I think I'll try for 180 seconds, 2x2 bin with an Astrodon Ic filter on the 17inch.  If my SNR is 80 or greater,  I'll keep this or try a clear filter for 100 seconds or less.  I may try to concurrently shot it with the C-11 with a clear filter.

James

 

WGR
WGR's picture
Request for additional Comps

Hello

After a couple of nights of obseving this object, I believe that the best results would be had if the comps "KIC 1 and KIC 2" were used.  They are particularly close to the object which reduces residual flatfielding.  They are also particulaly faint, allowing one to expose the object for the maximum SNR.  While there is a 152 comp in the field, its a long way from the target.  I am using a 24 inch and 400 second exposures, and at that point the 146 starts to saturate, yet the target is at SNR 20-30.  Using the KIC1 and KIC2 would allow deeper images and better results.

Using a trasfer technique from the 146, I have generated 15.005 and 14.825 with errors of .0042 and .0052 respectively for KIC1 and KIC2, on a stack of 10 images from a single night.  I would like to get official numbers to use.  Could the sequence Team extend to these two?  CHET form also submitted with same request and info.

 

Thanks

Gary

MZK
MZK's picture
Comp Color/Mag

After looking at my SNRs above, I concur with Gary. If B-V color could also be near 1.2, it would help when using clear filter. Note divergence in table above for comps with much different colors.

Ken

WGR
WGR's picture
New Comps

Hello Ken

Thanks for supporting KIC#1 and KIC#2 as the comps for this campaign.  I did not do any B images, but did go back to my first night where I had V and I. I was able to compute V-I for KIC#1 as 1.16 and KIC#2 as 1.05.  So their B-V's are probably close to your request to keep under 1.2.  Did you do any B images?  Perhaps you have already calculated that for them.  

BTW:  I get 1.42 for the V-I of KIC 02856960.

Gary

WGR

MZK
MZK's picture
FOV / Comps / Colors

Gary:

Your FOV is clearly smaller than mine and most others. Issue is need fainter comps so do not saturate them while getting reasonable SNR for fainter target. That affects all of us. Therefore, it would be nice for chart team to select any comps fainter and closer to target. I haven't looked at the PIs list of comps again. I also have not checked color for other comps. Your V-I values for  KIC1 and KIC2 compared to target may indicate these two are not too close in color? But, beggars can't be choosers??

Ken

 

WGR
WGR's picture
FOV

Hello Ken

I am working with the standard (f) chart.  It 18 arc minutes.  My FOV is 14 arc minutes.  Chosen for PT.  I like to use close comps--close in loacation, close in magnitude--close in color.  I guess we could call them          (Close Comps)^3  in enginerring notation.  My office is 86 degrees--I think the heat got to me

 

Gary

jji
KIC 1 and KIC2

KIC 1 and KIC2 have been added to the sequence for KIC 02856960.

Enjoy

Jim jones

 

WGR
WGR's picture
Thx for comps added

Jim Jones

 

And the sequence team.  Thank you very much for adding those on short notice.  

I will buy you a beer at the next meeting.

 

Gary

wluding
wluding's picture
Comp and Check stars

If I'm following your discussion correctly, the newly added stars to the sequence (148 and 151) are being considered for use as the comp and check stars. Since they don't have Ic magn does that mean we would need to use V filters?

I was thinking of using an Ic filter, star 137 as comp, and star 139 as check. Both have B-V of 1.2.  Star 137 is closer to the variable, so it makes the better comp star. Star 139 is farther away, so maybe 131 would be a better check.  Any thoughts on this?

Whit

 
 

WGR
WGR's picture
New Comps

Hello Whit

Good question.  However, unless you have a very big scope, or a super sight, my guess is you are going to be unable to get SNR of 100 in anything but Clr.  I am still getting .04 to .05 errors, 400 seconds, 24 inch scope in Clear, sea level sight. So this request was to get a couple of comp stars close to KIC 028 that would not saturate in 600 seconds, since that was the only way I was going to get close the the requested .01 to .02 errors.

Clouded out tonight

 

Gary

wluding
wluding's picture
SNR in Ic

Hi Gary,

I am able to reach SNR of 100 or better in the Ic filter for this variable in my out-of-eclipse test images. This was with 480 second exposures, so I think I can meet the temporal requirements, even with the overhead of guiding. I'm using a C14 scope and ST-8XME camera with Astrodon filters. The scope is located in the middle of Texas with clear skies this time of year. My main problem is the heat - I can only cool down to 0 C.

I would paste a clip from VPHOT so you can asses my SNR, but I can't make this editor do it. My SNR is 165. The Ic magn using all the comps is 14.592 with an err of 0.024.

Whit

 

WGR
WGR's picture
Sky Envy

Hello Whit

I envy your Texas Skies

Gary

MZK
MZK's picture
MZK Results (150808)

I ran the target all night. I used 148 as the comp and 151 as the check. Target SNR about 96 with 270 sec clear filter images.  12.5" f/8 cassegrain/STL-6303e.

Target was stable throughout the night with very small variations (noise?). VPhot time series image shown below.  No hint of eclipse. Check was more stable.  

Ken (MZK)

WGR
WGR's picture
MZK Result

Hello Ken

Wow!  Now we are getting there.  This is a very nice run.  The OP should be happy with that.  I hope to do something like this tonight.  Forecast is so so.  

It also shows that V or I at a cadence of 600 seconds for 12 inch scope is probably not possible with errors matching this run.  That's a good point for all.

 

Gary

wluding
wluding's picture
Results are odd

Hi Gary and Ken,

My data from last night is puzzling to me, could you help me understand what might be at issue. I've run the data through VPHOT with Time Series, then downloaded the results to my spreadsheet. The results are attached showing the variable and the check star; I used star 131 as the comp star and 143 as the check star.

I don't feel good about submitting these data without some pointers from someone who's more experienced with this than myself (I took the VPHOT class at the beginning of 2015). First of all, the gap between the first 9 points and the 10th point coincides with the pier flip of the GEM. It seems that there was a shift in the magn at the same time. What could that be a result of?

The "Std" reported my VPHOT was 0.057 for the variable and 0.018 for the check star. I assume this is the standard deviation for the data points.  I don't think this isn't very useful for a variable star, but provides a good number for the check star. So, that's what I added as the error bars in the graphs for both stars. Am I correct in doing it this way? BTW, the average SNR was 163 for the variable and 314 for the check star.

Whit

MZK
MZK's picture
Pier Flip Mag Shift

Whit:

I suspect the mag gap is due to flat issues. This occurs occasionally after pier flip. Try to use the 148 and 151 comps mentioned above. They are right next to the target and so close that a flat problem is less likely.

With respect to the error band issue, yes, the error for the target represents the small random noise for a constant series plus the overall mag range of the target during the run. Sort of!

HTH, Ken

PS: To attach an image file you may have saved with shift printscreen, directly into your forum post, conduct three steps, which are a bit counter intuitive. First, attach the printscreen image file to your post with the file attachment link below. Second, highlight and copy the name of the image file displayed just below the attached file name box. Third, open the image icon in the tool bar above and paste the file name into the url box. Click ok. Voila!

 

WGR
WGR's picture
Errors

Hello John

I echo what Ken said in his post.  I was not able to open the attachment for two reasons.  Ken mentined one and two, I am an old Excel guy, and cannot open the new docx formats.  They changed the commands around so badly that I cannot even make a graph anymore, so I refuse to use it.  I have too many years invested in the old one, and the new one was changed for no good reason, other than to change the look and feel of it all.  Can you save it in old excel also for me? Thanks.

Your jump at the pier flip is probably caused by "Scattered Light issues".  A google search should bring up some papers on the issue.  Baffling and flocking is the usual solution, along with examining the image train near the camera.  Black Anodize works just like a polished mirror in the IR--its very reflective.  You may be getting the residuals from non sympetrical reflections.  Also a good flat black optical paint can be used here.  I use the flocking from Prostar.  

As for your .057 std deviation, and SNR of 163 for the target, I am not surprised.  While we use SNR of 100 and errors of .01 mag as interchangeable, this is just the Photon Noise.  The .057 includes the effects of bias, dark, sky noise, flat flieding, aperture size, software rounding, etc etc etc.  I find that a rule of thumb that my errors on a time series are roughly 3x what I would expect from just the SNR, and your results are consistant with that.  

I have spent the last 8 years chasing scattered light issues to improve PT with my scopes.  Its subtle, but it works.  Its never ending, and I consider it a continuous process.  I look forward to seeing your light curve.  Don't feel bashful, we all started where you are and learned by making the same mistakes.  This is a sharing group and will be glad to help.

Gary

PVEA
PVEA's picture
KIC 02856960

The first and may be not so successful session on KIC 02856960.

  • V filter
  • exp. 300 sec
  • 151 – check star
  • 148 – comp star
  • SNR – between 74 – 98 – may be not so stable sky conditions (manually chosen the lowest limit of SNR=70 in VPHOT)
  • the obvious outliers are removed manually
  • a high level of scatter is obvious

Velimir

wluding
wluding's picture
Results with new Flats

I've used the same data as before (night of Aug. 7-8) and calibrated them using new Flats I took this morning. The results are much better. I feel these data are worth submitting.

Whit

pbenni
Transits captured

I think I captured the transits that were predicted with the 0.07 mag dips.  Equipment 11" SCT, ST8XME, with Yellow 495 nm high-pass filter (Astrodon Exoplanet).  Previous nights data with same setup showed a stable baseline.

-Paul

 

MZK
MZK's picture
Transit

Paul:

Looks quite convincing!  I ran all night but haven't looked at the data yet. I'm hopeful now! Great job.

BTW, what comp did you use? When I used the 148 as opposed to 131, the mags were quite different in my clear filter.

Ken

pbenni
Transits captured

I used Ref star #137 and Check star #143.  Being primarily an exoplanet transit researcher, this star's shallow transit characteristics called for the CV exoplanet filter setup.

Hope everyone can verify the transits!

-Paul

BPAD

MZK
MZK's picture
MZK Results 150810

I ran all last night as Paul did. We live within a few miles of each other, so the temporal structure should be the same. I used the same comp/check (148/151) I had used on 150808 mentioned above, but different than Paul so the magnitudes differ by 0.2 mag in our different clear filters.

I have attached both time series results below for your observation. Definitely something going on last night 150810!

Ken

Matthew Templeton
Wow!

That's really cool -- you (Ken) and Paul Benni are right on top of each other.  I think you definitely caught a piece of the eclipse.  Awesome!  Another few days of observations would be great, to catch any remaining events and to establish zero-points for everyone.

Really great work, everyone -- many thanks to everyone who has participated so far!

Matt

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