Affiliation
American Association of Variable Star Observers (AAVSO)
Wed, 11/14/2012 - 18:43
Attached is a LGC plot of Mira variable U CAP, which was in "need of more observations" over a year ago. My observations have been highlighted with a "cross." By just taking one image every 7 to 10 days, the minimum and and maximum have been easily identified. I also observe R AND, X AND, X AQL, U CAS, S CET, Z LYR and other Miras in a similiar fashion. Consider taking CCD images of select Miras on occassion to help in monitoring their long term behavior. Kevin Paxson - PKV
Here is the attachment.
that's a
Hello Kevin,
that's a very nice lightcurve. Can you give some details about your workflow? I presume that you use a V-filter. Did you always take only one image?
cheers, Hubert
This light curve and others I have mentioned were derived from images taken with the Sierra Stars 24" in CA. All images used for U CAP were a single 30 second Johnson V exposure. SNR and error are respectable down to below magnitude 15. Reduction utilized a consistent ensemble in VPHOT. A 10 second Johnson V exposure can go as bright as the high 8th magnitude before saturation. A single 30 second exposure costs $0.75, but it is an easy way for amateurs in poor locations or no equipment to contribute to variable star science. Remote imaging also has the advantage of catching stars coming out of solar conjunction without having to be an early riser. Many AAVSO members use Sierra Stars, iTelescopes and other Internet based telescopes. Kevin Paxson - PKV
Hi Kevin, I have a C11 and
Hi Kevin, I have a C11 and Johnson V-filter. I concentrate on HADS but I will give this a try. I don't know how faint I can go with my equipment and V-filter but it seems worth to try it out. Thanks for the information.
clear skies, Hubert
Hi Hubert,
I use a 10" (25cm) Meade LX-200. Everything of course depends on your signal to noise ratio. I can get an SNR of 100 with a well tracked 120 second exposure on V = 14.0 magnitude stars through a V filter at low airmasses (near the zenith). Longer exposures will get you fainter of course and if you really want to go faint, you can stack multiple images.
Between "real life" and the weather, I can rearly observe more than once per week so I do a lot of Miras and other slow moving variables. You should have no problem with your scope and V filter doing a good job on those Miras.
....Tim (HTY)
Thanks Tim for this info. I think I will give it a try.
The AAVSO Bulletin will give you the number of observations received for each star in the prior year so you can find the underobserved ones for the previous year at least.
The Basic Observation Planner will also give you the total number of observations in the AAVSO database for each star it produces for a given search criteria so you can kind of get an idea from that what is underobserved too but for Miras I'd use the Bulletin first.
Unfortunately many stars were removed from the Bulletin in the last couple of years for a reason that I don't recall but I still try to keep the faith on some of those old friends that were dropped that pass near my zenith.
....Tim (HTY)
There was another post like yours Kevin about this topic 5-6 months ago regarding neglected CCD observation of Mira type variables. I volunteered to monitor khi Cyg and TU And. I had to shoot these stars for only 15-sec.'s at 1x1 bin through a V-filter to avoid saturation. Here are AASVO graphs of my first runs (NOTE: the filenames were for my convinence...the date range may be off a couple of days at the beginning or end of the runs) FJQ-James Foster, Los Angeles, CA
Hello James, why these
Hello James, why these stars? They have enough visual covering in my opinion.
Very nice lightcurves! I see you have a lot of good weather conditions.
To: Hubert,
RE:"Hello James, why these stars? They have enough visual covering in my opinion."
I got these two (khi Cyg & TU And) assigned from Robert Fidrich's post of underobserved LPVs from this forum: http://www.aavso.org/under-observered-variables (see 3rd and 4th post there). Here is the google-spreadsheet that is tracking the LPVs that we're monitoring: https://docs.google.com/spreadsheet/ccc?key=0AjhP4-rjy5DGdC1xMlo0UF9hMGtTREwwRTdObkhUVmc#gid=0
RE:"Very nice lightcurves! I see you have a lot of good weather conditions." Yea we're lucky to be blessed with many nights of clear skies in Los Angeles. I typically have my scope record CCD observations autonomously on about 15 targets a night with Cousins V & B filters. Since my 33cm apeture scope is fairly fast at F/7.4, the system makes guided exposures of 200 seconds for B and 120 seconds for V, 2x2 bin; this is for variables dimmer than 11th magnitude with good seperation btw it and the comp stars. If the variable is brighter than 11th magnitude V, I do 15-sec exposures with 1x1 bin. For the bright LPVs, I use these short, unbinned 15-sec exposures through the V-filter.
I can only shoot near meridian as my 2-story house blocks polaris and surrounding trees block about 60% of the sky; luckily, I have a good south, and south-western view (down to -20 dec), but I cant observe any variables north of +66 degrees.....James
Hi James, I find it strange that Chi Cyg and TU And included in this underobserved LPV program. They both have good visual coverage especially Chi Cyg. Chi Cyg has 873 visual observations last year. Not really a underobserved star
There are a lot of other mirastars that are really underobserved and need more attention.
BTW, thanks for your workflow.