David's Astronomy Pages Images - Session 1367 (2025-09-26)

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Objects	Session Notes
C/2023 A3 (Tsuchinshan-ATLAS) - Comet     AT 2023ctv - Type ulens? Transient AT 2025hwl - CV Type Transient  (non-detection)         Variable Stars (photometric monitoring) - T CrB, U And     Nearby Stars (astrometric monitoring) - None	- Evening session (1.5 hr), but ended early due to cloud. - 12" LX200 + ST-10XME for imaging - TS 80mm APO + ZWO ASI178MC for guiding & imaging - Ambient Temperature: 13°C (min). - CCD Temperature:  -10°C - Notes from 2025-09-26 >>           -

Observing Result

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C/2023 A3 (Tsuchinshan-ATLAS) - Comet

C/2023 A3 (Tsuchinshan-ATLAS) - 2025-09-26 (passing through Hercules) Sun Distance 5.25 AU (receeding) Earth Distance 5.23 AU (781.7 million km)		C/2023 A3 (Tsuchinshan-ATLAS) - 2025-09-26 Autoguided on offset star using PHD2 with Lock Shift set at the comet's rate of motion (Ra 1.69 arcsec/hr, Dec -19.39 arcsec/hr Position of comet (very faint) is indicated by white cross-hairs
Annotated CCD Image (50% size, square root scale) 3 x 30s exposure (average combine), 3x3 binning, Clear Filter 2025-09-26 21:04 UT (#1367028-31) 12" LX200R (at f/10.4) + ST-10XME Auto-guided using TS 80mm APO, ZWO ASI178MC & PHD2		Annotated CCD Image (125% size, square root scale, cropped) 9 x 30s exposure (average combine), 3x3 binning, Clear Filter 2025-09-26 21:04 UT (#1367028-37) 12" LX200R (at f/10.4) + ST-10XME Auto-guided using TS 80mm APO, ZWO ASI178MC & PHD2
Images of C/2023 A3 Tsuchinshan-ATLAS on Comets 2024 Page >>
Images of C/2023 A3 Tsuchinshan-ATLAS on Comets 2025 Page >>

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AT 2023ctv - Type ulens? Transient

AT 2023ctv (Ophiuchus) AT 2023ctv (Type: ulens?) discovered 2023-03-04.717 UT by Gaia using Gaia Spacecraft Telescope Alias: Gaia23azj Alerting Magnitude 16.08 (G-Gaia Filter) vs Historic Magnitude 16.38 + 0.07 SD Red gal.plane source candidate microlensing event rises by 0.3 mag  ( TNS 2023ctv | Gaia23azj )

AT 2023ctv - 2025-09-26 (T+937.2d) Image below (2025-09-26.900) was taken 937.2 days after discovery of 2023ctv Position of earlier transient (probably back at normal brightness) is shown by white cross-hairs Measured magnitude +16.00 (Clear Filter)

Annotated CCD Image (100% size, linear scale, cropped) 4 x 180s exposure (average combine), 3x3 binning, Clear Filter 2025-09-26 21:43 UT (#1367047-50) 12" LX200R (at f/10.4) + ST-10XME Auto-guided using TS 80mm APO, ZWO ASI178MC & PHD2

Images of AT 2023ctv on Transients 2023 Page >>

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AT 2025hwl - CV Type Transient (non-detection)

AT 2025hwl (Ophiuchus) AT 2025hwl (Type: CV) discovered 2025-04-20.847 UT by XOSS Alias: KATS25H002, TCP J18225593+1020013 Discovery Magnitude 15.03 (Clear Filter) CV candidate classified by XOSS The spectrum shows a blue continuum with Balmer absorption lines, except for Hα (6562.8 Å), which appears filled-up due to emission from the accretion disk. A likely progenitor is identified in ZTF data with a mean r-band magnitude of 18, implying a brightness increase of approximately 3 magnitudes (Δmag ≈ 3). These features are characteristic of a cataclysmic variable (CV  ( TNS 2025hwl )

AT 2025hwl - 2025-09-26 (T+159.0d) Image below (2025-09-26.885) was taken 159.0 days after discovery of 2025hwl Position of earlier transient (faded & no longer visible) is shown by white cross-hairs Non-Detection Limiting Magnitude +19.4 (Clear Filter)

Annotated CCD Image (100% size, linear scale, cropped) 4 x 180s exposure (average combine), 3x3 binning, Clear Filter 2025-09-26 21:43 UT (#1367047-50) 12" LX200R (at f/10.4) + ST-10XME Auto-guided using TS 80mm APO, ZWO ASI178MC & PHD2

Images of AT 2025hwl on Transients 2025 Page >>

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