[Aavso-photometry] Epsilon Aurigae PEP observing

[Bob Crumrine]

Hi Jeff,

Looks interesting and I have a few questions. 

I've never used the blue filter on my SSP3.  How do I calculate my blue 
filter transformation coefficient?  I've calculated my epsilon-V  for 
the V filter many times and am about to re-do it using the Red/Blue pair 
27/28 LMi the next clear night I'm up late.  Looking at the Henden / 
Kaitchuck book p.54, I've used equation 2.48 to calculate the eps-v; do 
I just use 2.49 to calculate mu?  If so, what's the sequence I need at 
the telescope?  I'm thinking red star (v filter), red star (b filter), 
blue star (v filter), blue star (b filter), etc.  Is that correct?  
(I'll need to remember to keep track of the filters!)

What do I do with the air-mass calculation?  I'm familiar with 
calculating it for CCD reporting but haven't actually used it in a 
calculation.  Also, it'll take about 30 minutes to get the data for both 
lambda and epsilon using both filters; what time do I use for the 
airmass calculation?  Do I generate an airmass for each measurement?

Also, I see you've written several interesting papers on Epsilon Aur.  
How do observations submitted with this campaign get distributed to the 
wider community?  Will they show up in the light-curve generator? 

Thanks,
Bob

Jeff Hopkins wrote:
> Hi Bob.
>
> Check http://www.hposoft.com/EAur09/Starinfo.html
>
> Currently my PMT Photon Counting BV values for epsilon Aurigae are B= 
> 3.6041 SD = 0.0016 and V= 3.0499 SD = 0.0021
> No check star is needed.
>
> For procedure:
> I suggest taking 3-lambda ten second reading in B then V followed by 
> one sky reading in each filter. If the sky reading are high relative 
> to the star + sky, take three sky readings in each filter for the sky. 
> Repeat for epsilon, lambda, epsilon, lambda, epsilon and lambda. 
> Reduce the data and take the difference then normalize to lambda's 
> published values. You should then have three magnitudes for B and 
> three for V. Average each filter's magnitude and take a standard 
> deviation. Those data are then what should be used. Do this as quickly 
> as you can and the data should be good. When reducing the data you 
> should take into account extinction. You can use lambda to calculate 
> the extinction. If you observe close to the meridian the difference in 
> extinction between lambda and epsilon will be minimal. The further 
> from the meridian the more important the extinction correction is.
>
> Let me know if you have any questions.
>
> Glad to have you involved. You should visit the web site and check how 
> to become a campaign member and send me the data and I will add you.
>
> Good luck.
>
> Jeff
>
> At 19:54 -0700 01/26/2008, Bob Crumrine wrote:
> Jeff and others,
>
> I'd like to begin doing single channel photometry of Eps Aur while 
> it's still high in the sky, using my SSP3 and 8" LX-200.  What are 
> good Comp and Check stars and what are the accepted V and B-V for them?
>
> Thanks,
> Bob Crumrine (CRR)
> near Rochester, NY
>
> Jeff Hopkins wrote:
>
> Hi Steve,
>
> Epsilon Aurigae is a 3rd magnitude (V) star and pretty easy to find,
> right next to Capella and at the vertex of the triangle known as the
> kids. Lambda Aurigae is the normal comparison star. While there are
> other stars closer, they are too faint for CCD work in that if you
> stay linear with epsilon the comparison stars will be in the noise.
> For CCD photometry there are two major problems, the brightness and
> wide separation of program and comparison stars.
>
> Bob Buchheim wrote an article for the SAS Vol. 5 Number 3 Newsletter
> titled "Getting Ready for Epsilon Aurigae." He indicated the problem
> with CCD photometry and the brightness of epsilon Aurigae. He
> suggested stopping down the telescope, but that does not solve the
> separation (around 5 degrees) of the program and comparison star.
>
> At HPO we have investigate using a 50mm F/2.0 camera lens on a DSI
> Pro. Preliminary results are very encouraging. Both epsilon and
> lambda Aurigae fit in the image and by defocusing the image a bit
> under sampling is solved. Several nights have produce BVRI data where
> 3 sets were 0.01 magnitude or between data spread. I'm in the process
> of writing up the procedure. While this is CCD filter photometry, it
> is very different from CCD photometry of fainter stars.
>
> Of course the star system works best with single channel photometry.
> For more information check
> <http://www.hposoft.com/Campaign09.html>http://www.hposoft.com/Campaign09.html 
>
>
> Jeff
>
> At 18:26 -0700 01/21/2008, Steven Orlando wrote:
>
>
> Hello All!
>
> On the homepage, there was a call for data for EPS AUR. However,
> when I go to  plot a chart I get no photometric start for my FOV.
>
> Anyone have a link to a star chart for this star?
>
> Steve
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