If I manage to get through my programme stars, I have taken to imaging with B and V filters, bright high declination galaxies (mostly Messier objects). I wondered if there was any scientific value in this, as I suspect the field is probably sewn up with automated and professional surveys. If not I’d look to some other area.
Any advice please.
With the right sort of set-up I think this can be valuable. So far as I know, there is no survey coverage map, such as has been available for the big asteroid surveys, showing sky coverage on a nightly basis. That might be something the AAVSO could work out, though arranging it would be a challenge. If you can cover significant portions of sky north of (say) +50 Dec, especially if you can reach the pole, or even go under the pole with an alt-az mount, then you end up getting coverage of regions not usually hit by the big surveys. Going close to the Sun (less than about 60deg solar elongation, including under the north pole near the summer solstice) is also useful.
You might try to cobble together a list of galaxies with redshift velocities less than 3000 km/sec, target those, then add as much of the northern Milky Way as you can get on any given night.
At the other end of the process, you really need to have an astrometry and photometry pipeline in place so that reductions can be done efficiently.
\Brian
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Thanks Brian,
I don’t have large scope and can only get useful photometry down to about mag 13/14V. It’s a pretty informal programme on the odd nights when I have completed everythng else. I thought it might be useful to have some filtered photometry but then there is the problem of letting people know it exists as it’s not like reporting variable stars. If it’s useful I’ll continue.
Just means we need a bunch of folks doing similar observing…
One of the issues is being able to keep up with what observing is actually going on. A very recent example is a bright SNIa in the bright galaxy NGC 7331, discovered a week ago by a survey, and also picked up visually by folks using the Mount Wilson 60-inch:
https://www.astronomerstelegram.org/?read=17294
https://www.astronomerstelegram.org/?read=17296
The second note has links to the survey discovery and a spectrum.
Should you not bother observing the galaxies, variable stars — or anything else? Dunno.
\Brian
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Greetings,
Sad to see a discovery “retraction”, ATEL #17296. Not good PA for amateurs. The “professionals” have moved so far ahead and few if any amateurs have moved up in ability along with them. Much of it is purposeful by the professionals and it isn’t funny anymore. Funding by deep pocket funding sources drives it all… volunteer amateurs don’t stand much of a chance in today’s astronomy. The quick communication paths between amateurs and professionals has been severed as well.
In the old days a telegram to the Central Bureau for Astronomical Telegrams (CBAT) was used to communicate a comet, nova, or supernova “discovery”. CBAT would often do the follow up to confirm if additional confirmation was required and write and publish the announcement. That quick communication model is long gone.
An amateur search network for SN could be useful as described by Brian in the regions of sky he mentioned. Hard work, very low probability of success, and other problems. Is it worth it to observe for thousands of hours or more of integration time to discover a single SN? Perhaps… Visual comet discovery was like that–in the old days–and many spent the time and found them. Motivation: you got your namesake to blaze in the sky with your name for a few weeks or months!
It is hard for me to imagine that observers can’t find other variables to add to an observing program. It is all a moot point for me–what is up with this eastcoast weather? 
VSX now has tens of thousands of new variables added by Sebastian to follow. Yes, the surveys cover much of them, but those same special regions with little or no coverage await.
Best quality photometry using standard photometric filters and transformed is the only way to go. We all need to focus on doing this.
This was not written by any AI 
, a real human used its brain and typed this. 
Jim (DEY)
I decided years ago that the best use of time for photometry where I live (Brisbane, central east coast of Australia, weather not good for astronomy much of the year) is time series photometry through the night. Sure, I still occasionally obtain individual obs on stars such as the two recent novae in Lupus and Vela, but time series is really what I do, mostly now southern eclipsing binaries for Variable Stars South.
Of course surveys will probably include all of these stars, but not every night (or, in the case of TESS, not every year), and not with a high cadence (e.g., one image every minute) to capture accurate mid eclipse timings.
Jim mentioned transformed photometry with scientific filters as the way to go. I guess that works if you use VPhot or, I think, Phoranso, but I want to process on my own computer (therefore not VPhot) and with an image capture app I’m used to (has some incompatibilities with Phoranso, but I’ll get around to addressing this at some stage), so I take non-transformed data in V at high cadence and process in AstroimageJ and spreadsheet templates (one for each target) to diminish reduction drudgery.
The attached light curve is an example from my 8" SCT on an equatorial wedge and ZWO ASI294MM camera (14 bit). I’m sure lots of AAVSO observers are doing this sort of thing, but it is very satisfying, and with a number of observers targeting the same stars over years useful O-C diagrams are obtained. Note the difference from catalogue (0.008 mag) for the check star, which is the sort of thing anyone can do with the right targets and non-transformed V if the B-V difference between target or check and comp is small and Tv_bv is small (in my case about 0.054).
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Sure, there are programs that don’t need transformed data, but if you are taking multi-filter observations you should learn to transform. Either use the AAVSO tools or roll your own. I have done the later and it is an extra step and takes more effort and time but is worth it.
Many stars such as cepheids, some eclipsers, etc. have different shaped light curves depending on the filter used. So in those cases it would be useful to transform the magnitudes.
Jim (DEY)
I know how to transform and have TCs for my ASI294MM camera with V and B filters, and for my DSLR camera. I use MS Excel to calculate the TCs, and also spreadsheet templates to calculate transformed magnitudes, particular for DSLR data where TCs are way different from unity (b-v/B-V) or zero (V-v/B-V).
Calculating transformed magnitudes with a OSC camera is not at all difficult (green and blue channel exposures obviously taken at the same time), but the problem is with a filter wheel taking V and B images in time series of short period variables where the magnitude varies from image to image, and (particularly for pulsating variables) the B-V also varies continuously. As noted previously VPhot and Phoranso can take care of this situation, but if you’re doing your own calculations it’s a more complicated business.
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