Proposal #715

Proposer	(19434) Santanu Basu (sbasu4783@gmail.com) obscode: BSAB
Assigned To	(3663) Dirk Terrell
Date Submitted	July 18, 2026
Status	Allocated
Priority	Normal
Proposal	Target Name: M4 and M70 (Globular Clusters) Scientific Objective: To observe RR Lyrae and Delta Scuti variable stars in the globular clusters M4 and M70 using Sloan u, g, and r filters. The primary objective is to investigate the metallicity distribution of variable stars located in the central regions compared with those in the outer regions of the clusters. Multi-band photometry will be used to derive stellar colors, construct color–magnitude diagrams (CMDs), and examine the positions of the variable stars relative to the cluster stellar populations. These observations will also help characterize the photometric properties of the variables and explore possible correlations between metallicity, stellar location, and pulsation characteristics. Filters Requested: Sloan u, g, r Number of Nights Requested: 5 full nights Observing Duration: Full-night observations on each of the five nights. Justification: The Sloan u, g, and r filters provide color indices that are sensitive to stellar temperature and, particularly in the case of the u band, to metallicity effects. Deep multi-band observations will enable accurate photometry of RR Lyrae and Delta Scuti stars across the clusters, allowing the construction of high-quality CMDs and the comparison of variable stars in the cluster cores with those in the outer regions. Five full nights are requested to obtain sufficient photometric depth, time coverage, and signal-to-noise ratio for reliable measurements in all three filters, especially the relatively faint u band observations.

Targets

Target Name	RA (H.HH)	Dec (D.DD)	Magnitude	Observation Frequency	Expiration Date	Proprietary Term
Messier 70	18.720000	32.29194	7.9–9.1	1	Aug. 31, 2026	No
Messier 70	16.393056	26.52556	5.4–5.9	1	Aug. 31, 2026	No

Plans currently in place

dso35/AAVSO_P715_BSAB_AUTO.csv

# $Id: AAVSO_P715_BSAB_AUTO.csv 5922 2026-07-30 21:52:23Z MZK $
#PROPOSAL=715
#REQUESTER=BSAB,,vphot
#target,hh,mm,ss.ss,dd,mm,ss.s,desc,priority,monitor,maxX,nrepeat,bin,[filter,exposure,nexp],[filter,exposure,nexp]
Messier_71,19,53,46.49,18,46,45.1,Messier_71,50,1,2,1,1,SG,30,10,SR,30,10,EarliestTime=2026-07-18T00:00:00,LatestTime=2026-08-31T00:00:00
Messier_71__1,19,53,46.49,18,46,45.1,Messier_71,50,1,2,1,1,SG,180,2,SR,180,2,EarliestTime=2026-07-18T00:00:00,LatestTime=2026-08-31T00:00:00

Comments

(19434) Santanu Basu — July 20, 2026, 8:40 p.m.

Proposal Correction

I would like to make a correction to my original proposal. My intended target for this observing program is M71 only, rather than M4 and M70 as stated in the original submission. Accordingly, I have updated the scientific objective and observing plan to focus exclusively on M71. I am submitting this comment to clarify the intended target and to ensure that the proposal accurately reflects the scope of the proposed observations.

Target Name: M71 (Globular Cluster)

Right Ascension 19h 53m 46s and Declination +18° 46' 45"

Maximum Magnitude ~11th magnitude
Minimum Magnitude ~16th to 18th magnitude

Scientific Objective:
To observe RR Lyrae and Delta Scuti variable stars in the globular cluster M71 using the Sloan u, g, and r filters. The primary objective is to investigate the metallicity-sensitive color indices of these variable stars through multi-band photometry and compare their photometric properties. The observations will be used to derive stellar colors, construct color–magnitude diagrams (CMDs), and examine the relationship between stellar colors, pulsation properties, and metallicity-sensitive photometric indices.

Filters Requested:
Sloan u, g, r

Number of Nights Requested:
5 full nights

Observing Duration:
Full-night observations on each of the five nights.

Justification:
I am requesting AAVSOnet telescope time to carry out this observing project. The Sloan u, g, and r filters provide color indices that are sensitive to stellar temperature and, particularly in the u band, to metallicity effects. Multi-band observations of RR Lyrae and Delta Scuti stars in M71 will enable accurate photometric measurements, the construction of high-quality color–magnitude diagrams (CMDs), and the investigation of metallicity-sensitive color indices. Five full nights of observations are requested to obtain sufficient photometric depth, complete time coverage of the variable stars, and a high signal-to-noise ratio in all three filters, together with the corresponding FITS images required for detailed scientific analysis.

(3663) Dirk Terrell — July 28, 2026, 4:09 p.m.

The TAC is concerned that this will be very difficult with our equipment and sites. Blending is likely to be significant and reduction to unbiased photometry is doubtful. We would be willing to do a few test images and have you show us that you can get the kind of data you need. Then we can decide if a bigger investment of time will be worthwhile.

(3663) Dirk Terrell — July 30, 2026, 3:06 p.m.

Ken, note the change in target and the provisional nature of the approval in my previous comment.

(4726) Kenneth Menzies — July 30, 2026, 9:56 p.m.

Allocated to dso35 with SG and SR filters. Short (30s) and long (180s) exposures taken. Determine what you can resolve and get good photometry. Report when you get a few images for tests.

Comments on this proposal are closed.