Photometric V filter sources?
Posted 19 June 2012 - 10:41 AM
Posted 19 June 2012 - 02:12 PM
The older Schuler filters were closer to $100 but it would appear that Astrodon is the only viable option if you want one now. SBIG sources their UBVRI filters from Custom Scientific. I checked the OPT website and they do have a selection of Custom research filters on sale ($150) but the V-band ones are back-ordered. FWIW be prepared to wait since it took 4 months for Custom to deliver a 1.25 photometric clear filter for my CFW9.
Posted 19 June 2012 - 02:36 PM
Thanks for confirming my thoughts on a V filter source. Guess I will have to put up the $$$ to get one if I want to start this summer. Though, I will give OPT a call and see if they have a lead time for CS V filter.
One other thought I had was going into the Sloan filters. Is there many amateurs using them? Of course that will cost me more. But if that is the direction photometry is going, I might as well go with it now instead of down the road. Does that make sense?
Posted 19 June 2012 - 05:28 PM
1) Getting the process down pat, and, gathering data
2) Submitting data to various database(s).
For the first part, you dont need a V filter, use what you have, get some practise in taking shots, then reducing them for photometry. For some programs, clear or 'no filter' are desireable. For some, the specific filter in use, is not really important, as long as it's the SAME filter through the series.
A good example, you can do exoplanet transit measurements, and submit into the ETD using any filter you like, choose what works best for your gear / location. Consistent measurements, with accurate timing are the important keys for a transit series.
The V filter really only becomes necessary if you want to submit data to a database which is trying to 'level' the observations from various sources, and the BVR filter set is the traditional 'leveller'.
FYI, over a period of a few months, I was able to pick up one V, and one BVR set from amart, for substantially less than the going rate for brand new filters. I wasn't in a rush tho, because we got the first BVRI set on a blowout, for a good price, then waited patiently to find the right filters for the other telescopes, when they showed up for a good price. We still have the L, but have replaced the RGB with BVR on both of our kits now.
Posted 19 June 2012 - 06:43 PM
I use SLOAN filters for my photometry, based on the recommendations of experts. Mainly for calibrations and star field measurements and occasionally light curves of specific targets when someone asks...
BUT my main filter is a CBB (broad band blue block filter) which I would use for general photometry, about 90% of the time.
Posted 19 June 2012 - 08:53 PM
I would not recommend spending money on a Sloan photometry set until you have given photometry a try for a while. As others have said, get the basics down first. Minor planet light curves are usually captured with a clear filter so they are a good first target to get your feet wet.
Posted 20 June 2012 - 08:01 AM
What program is recommended for that? I do have MaximDL, which seems to be the only one that does photometry. But is there any other software worth considering?
It is looking to be clear tonight also, so I will be looking for another practice target. Man is this fun and exciting!
Posted 20 June 2012 - 10:38 AM
If you have Maxim, and know how to use it, that sounds like A Good Plan .
I do have MaximDL, which seems to be the only one that does photometry. But is there any other software worth considering?
I've used the photometry functions in AIP4WIN v2 ... I have a copy, it works and I understand what I'm doing with it.
Posted 20 June 2012 - 01:38 PM
Thanks everyone for the advice. It was clear last night so I did a practice run with TV Bootis
I have used gsc 3074-0114 a number of times for testing out various configurations. It is listed as mag 13.8 in the gsc catalog, but gives roughly a 0.8 mag swing over a period of a couple hours. It's fairly well situated at this time of year, and generates a very nice plot.
If you are looking for a starter target, that gives nice 'instant gratification' when you generate a plot from the data, this one does the job nicely.
Posted 20 June 2012 - 03:42 PM
Posted 20 June 2012 - 07:11 PM
Posted 20 June 2012 - 07:14 PM
Posted 20 June 2012 - 08:51 PM
The AAVSO will accept data taken through a green photographic filter-- select "tri-color green" for the filter used when you submit your data.
Posted 22 June 2012 - 09:45 PM
That's a pretty good start! Good luck with the rest of the curve. What software are you planning to use to phase all of the light curve data when you are finished? I've found MPO Canopus to be very useful for converting images to catalog-based magnitudes and period solving. Just a minor nitpick...by convention the y-axis in your figure should be reversed with the brightest values on top.
Posted 23 June 2012 - 08:03 AM
Posted 23 June 2012 - 04:48 PM
Many programs do great data reduction. Since I am an AAVSO member, I take advantage of VPHOT which is on-line and very slick for many photometric reduction tasks. I assume you have downloaded the latest AAVSO CCD manual.
Good measures, Ed
Posted 24 June 2012 - 08:38 AM
I do have the latest AAVSO CCD manual and have been through it once. I was just starting to go through it again to refresh my memory on things. Also, I think joining the AAVSO is going to be well worth it.
Posted 24 June 2012 - 07:23 PM
Good measures, Ed
Posted 24 June 2012 - 08:08 PM
Mine is the cheaper AAVSO version which does suffer from this, but it cleans off easily.
Posted 25 June 2012 - 07:45 PM
Posted 25 June 2012 - 11:17 PM
Posted 27 June 2012 - 07:17 PM
Posted 04 July 2012 - 03:17 PM
Incidentally, the B filter suffers from this problem too. The type of glass used in the B and V Schuler filters reacts with moisture in the air to form a coating which is easily washed or polished off.
Posted 08 July 2012 - 08:56 PM