Proposal #683

Comments

(3663) Dirk Terrell — March 31, 2026, 3:27 p.m.

The TAC approves this project for the three brighter targets to see hows things go before committing to a large allocation of resources. The requesting team indicates that they would like continuous photometry during a night, so we're not sure how that squares with this request for snapshot photometry.

Targets to be observed for now are YZ CMi, V1216 Sgr and G99-49. Note that these are high proper motion stars, so take care in identifying the targets.

(44938) Sauro Gaudenzi — March 31, 2026, 5:36 p.m.

Ok thanks a lot, however if you need to take more shots to do a continuous photometry during the night go ahead with a continuous photometry, you decide, for me there are no problems

(4726) Kenneth Menzies — April 2, 2026, 6:05 p.m.

Sauro: Sorry no! You need to understand what is required/desired for this campaign rather than for us to make decisions on what cadence to use. I don't think you are describing continuous time series during a full night for each target? That obviously cannot be done for all your targets, even 3, with AAVSONet resources. Please describe more carefully what you want to do? This is your proposal. Ken

(44938) Sauro Gaudenzi — April 2, 2026, 8:08 p.m.

Ok thanks so much for the clarification Mr. Ken, we are observing YZ CMi, V1216 Sgr and G99-49. I ask that 5 B-filter photographs of 30 seconds be taken with 40 second intervals between each frame and 5 V-filter photographs of 30 seconds with 40 second intervals between each frame. I ask that at least 2 observations be made per week starting immediately until December 3, 2026.

(4726) Kenneth Menzies — April 3, 2026, 4:35 p.m.

1. Why do you want/need 5 images in each filter and why do you want a 40 second delay between images? That is just a waste of available imaging time!
2. What are you going to do with the 5 V or B images on each night?
3. How did you decide what exposure to use (i.e., 30 sec)? The exposure should normally depend on the magnitude of the target and the size of the telescope used. I usually select an optimum exposure for each target based on the scope I commit it to. You just seem to request this process in all your proposals. Why?

(44938) Sauro Gaudenzi — April 3, 2026, 5:56 p.m.

Thank you very much for this observation. In fact, from the information I've seen online, the first two are stars with high proper motion. I never requested observations for all nights of these subjects. I had only requested two observations per week with B and V filters. Now I'm changing my request to 10 60-second exposures with a B filter and 10 60-second exposures with a V filter for all three subjects. I'm also requesting two observations per week for each subject. I'm requesting this type of exposure because the subjects are a bit faint. Once uploaded to Vphot, I perform the photometry, naturally trying to center the subjects well. I then upload everything to the AAVSO database. I'm doing this because I intend to collaborate on this type of research, observations, and photometry. I take this opportunity to wish everyone a Happy Easter.

(44938) Sauro Gaudenzi — April 3, 2026, 6:27 p.m.

Mr. Ken, I'm writing to wish you and your family a Happy Easter. I also want to thank you for your comments, which I find very constructive. Thank you again, very much. Best Sauro

(4726) Kenneth Menzies — April 8, 2026, 12:32 a.m.

Sauro:
1. Please describe the difference between time series photometry and snapshot photometry.
2. Which are you trying to do to support this campaign?
Ken

(44938) Sauro Gaudenzi — April 8, 2026, 1:30 a.m.

Time-series photometry refers to the analysis of data that follows a regular temporal order. Time-series analysis is a statistical technique that measures a variable at intervals of time, allowing us to observe and analyze the evolution of the data over time. Instantaneous photometry is a technology that allows us to obtain a ready image in a few seconds, without the need for external laboratories or a darkroom. This is what I know of. I rechecked these three objects and found that they are faint and, as far as I understand, not variable stars, which is why I changed my request. To support this campaign, I am trying to make photometric observations.

(4726) Kenneth Menzies — April 8, 2026, 7:01 p.m.

You stated/copied above: "The aim is to measure the amplitude of rotation-induced flux variation for each of these stars in multiple bandpasses using time-series photometry. Many of the targets have rotation periods < 1 day and could be observed for much or all of their phase within a single night.

In other words, it is suspected that the magnitude of these targets varies as a result of the rotation of the star, which contains large star spots that block the light from the star in specific locations. Many of the targets are suspected to rotate completely in less than 1 day! Think of SUNSPOTS BUT much larger and at a much FASTER rotation rate.

Therefore, IF you imaged the star 'continuously' during one night, you would obtain a light curve exhibiting this variation over perhaps 1/2 the entire period. "Time Series Photometry" simply means taking images continuously over a significant portion of the period of the star (i.e., many hours/the entire night). In this case, for a magnitude 12 star, you might use a V exposure of 60 seconds each with a 12 inch telescope, You would collect a few hundred images (i.e., 60 per hour) over a several hour 'time series'. Thus, in one night, you might see a good portion/percentage of the period of the star spot depicted in your light curve? Make sense?

IF you imaged the star for just a few images over a total of just a few minutes (<10 min), would you see much variation? Probably not! In fact, the magnitude would probably NOT vary at all over these few minutes compared to the period of 12-24 hours. Do you agree? IF the period of the target were 24 hours (i.e., 1440 minutes), what percentage of the variation would be observed in 1 minute? At about what total imaging duration might you detect the 'real' variation' as opposed to random image noise?

In cases where it is not suspected that you would see much, if any, variation in magnitude over the duration of your imaging (e.g.,<10 minutes), one normally conducts what is called snap-shot photometry. This appears to be what you proposed. Do you agree? In this case, you would normally take just a few images (e.g., 3) and 'average' their individual magnitudes to yield/report one single precise magnitude measurement each night.

IF you propose to collect snap-shot images/magnitude during one night (this is what you asked for) how many nights would you need to image this target to define the complete light curve period? By the way, this is an option for these targets, as you proposed!

(44938) Sauro Gaudenzi — April 9, 2026, 12:12 a.m.

Thank you so much for the explanation, kindly you can choose the best option, whatever it is is fine with me

(44938) Sauro Gaudenzi — April 9, 2026, 12:15 a.m.

Thank you so much for the explanation, kindly you can choose the best option, whatever it is is fine with me

(4726) Kenneth Menzies — April 10, 2026, 12:31 a.m.

Committed to BSM_NM. Daily. B and V filter snap shot. Over several months you will develop a light curve of the 3 targets. Look at the initial images and see if exposures are unsaturated. The exposures will automatically be reduced if needed.

Comments on this proposal are closed.