As I’ve helped with the SPP section over the years I’ve always come back to the question of what targets can I suggest to observers. I’m never sure if a target is good for different observers equipment. SPP is made up of a wide range of objects:
White dwarf - very faint and pulsate in seconds.
delta Scuti - wide range of magnitudes, periods of hours, lots of potential targets. High, low and medium amplitude (medium are the strangest).
beta Cephei - periods like delta Scuti but B spectral type
gamma Doradus - longer periods than delta Scuti and also be hybrids with both types of pulsation.
RR Lyr - not a lot of bright targets, a little longer periods
Cepheids (all types) - days to month period, range of magnitudes
A few other related objects.
Likely white dwarf are not great targets for any observer, but I would like to get a feel for what people believe they can observe of the other variables on the list above. That could be brightness range and potential cadence.
I’ve been wanting to provide lists of potential targets for all seasons and in both hemispheres. Especially for delta Scuti and Cepheids (the two types I’m currently working on). I need to get to know my audience better for those in the SPP section. This could include spectroscopic observations. Any feedback would be great.
Seems like all the easy fields having nice 7th mag comps and 7th magnitude variables are well documented already. Every new field I tackle is challenging. With a 12" SCT I can go from about 6 to 18 mag with a 24’ FOV. The smaller FOV allows me to avoid bright stars that limit what I can do with long exposures or stacking 20 images.
A lot depends on the magnitude range of available comps and extraneous stars in the image. If there is an unavoidable 7th magnitude bright star that limits exposure, 16 mag data is noisy. If comps are a lot dimmer than than a 7th magnitude variable, the data is noisy.
I am currently working on suggested Guzik DCEP and Otero binary lists.
I like your approach to this problem. Here at HQ, we’ve struggled with similar questions for years. In the end, it is a question of SNR and data processing techniques.
I like a challenge, so lets use white dwarfs as an example. Here’s what I’d do:
Search VSX for typical objects in a given class. ZZ (for ZZ Ceti) is one type of WD variable star with 17 known object. The brightest object is GSC 00281-00197 at V~12 with a period of 15.8 minutes and an amplitude of 40 mmags. Based upon the work our exoplanet group is doing, this should be easily observable. The faintest object is V0430 UMa which is V~19.16 with a 6.9 minute period with a depth of 80 mmags. That is going to be a challenge.
Look at the references in VSX to see what prior measurements look like. The reference for GSC points to a graph showing some nice stable pulsations that come and go. So this could be really fun, dynamic object to observe. It could even be a fun object to show at a public star party!
If there are no references, look at the sky survey data found in the “External Links” section of VSX.
Use an SNR calculator to determine what an typical consumer-grade telescope could do if it sampled the system at 1/10 of the period. In the case of the GSC, Dr. Richmond’s SNR calculator calculator claims my 8" setup can get a SNR of 10,000 in a 60 second exposure. So that’s probably doable.
Check for seasonable observability.
Let people observe and see what happens.
I hope this helps.
Brian
Edit: Sebastian noted that one can do a search for “%ZZ%” and get 295 results as ZZA, ZZB, ZZO, ZZ/GWLIB sub-types will also be included in the query results.
I appreciate the answers so far. It is giving me a better feeling for what to suggest as some new observing options. But I will always take more input so I can provide the best service to the observers of the SPP group.
The SPP has emphasized RR Lyrae, Cepheids, and Delta Scuti variables more than, for example, white dwarf variables. In part, that reflects the early history of the section. In the 1960s, AAVSO observers began to visually follow RR Lyraes and Cepheids, requiring targets with amplitudes of about a magnitude. Modern digital methods of course permit targeting variables with much smaller amplitudes. The SPP newsletters highlight one or two variables each season – a high-amplitude multimode delta Scuti star in the latest newsletter – which are generally observable with modest equipment.
