AAVSO Alert Notice 791 announces an observing campaign on the eclipsing triple-system b Per. Please see the notice for details and observing instructions.
There are threads for this campaign under the following forums:
Please subscribe to these threads if you are participating in the campaign so you can be updated. Join in the discussion or ask questions there!
Many thanks, and Good observing,
Elizabeth O. Waagen, AAVSO HQ
I now have an Atik 314L to replace my Canon 60d. But I don't have a V filter yet. Will I need to buy one? They are pretty hard to find.
BTW, I started imaging B Per last week in anticipation of this, but it doesn't rise above my trees til around 1:30 😞
Yes, we want the photometry results in V. I bought my filters from SBIG when I bought my SBIG camera. Yes, they're expensive.
Yes, the hours of visibility are terrible this year. I'm able to sleep most of the night while my computer chugs away.
Thanks for joining!
I don't mind spending the money, but everywhere I look they are on backorder :)
I suppose I could switch back to my Canon and extract the green channel, if I can't get a filter in time.
Following is an abstract from Notice 791
“It is recommended to use the star labeled '55' (AUID 000-BLL-386 = HIP 20156 = SAO 39457 = HR 1330 = HD 270840) in the AAVSO finder chart at 5.456 V for the comparison star. For a check star HIP 20370 (J2000 RA, Dec = 04 21 45.47 +50 02 06.64) may be used if the observer's field of view is about one degree. This star is not in the AAVSO sequence
A mag of 5.456 V for the comparison star HIP 20156 is provided, it would be nice if we could also have the V mag for the check star HIP 20370
I have 3 different nights of 90-ish images of Per B, however I hesitate to submit them because my results show much different magnitude than the recent observations show. Over the three nights 5.6 being the brightest down to 6.0.
I am using 55 and 111 as comparison stars and 101 as the check star. I am using VPhot.
Perhaps I am doing nothing wrong in VPhot but have my exposure too long (15 seconds) for such a bright star?
Is there a way to post a picture here? if so, I could screen shot to show how things look.
You can readily check for over exposure.
You can see the ADC counts in VPHOT. Click on the star of interest while in Regular mode . When the window pops up, click on details at lower left. Alternately, look at it in Pixel/ADU mode (top of main window). If you have not measured the linearity of your camera, limit exposures so that no star in the image has any pixels with more than about 60% of the maximum number of A/D bit for your camera.
That is 60% of 4096 for a 12 bit digitizer. My particular ST8XME is linear to 1% up to 47500 A/D counts for a 16 bit digitizer on a CCD. I can do 72% of maximum A/D counts, 65535 ADUs only because it has been measured. I think the CMOS cameras may be more linear, but never measured one.
Thanks so much for your help. Yes, over exposure it is. The target star and the comp star 55 are both max'd out at 65535.
I'll shorten my exposure from 15 to 10 seconds and try again.