EAA Observing Session: 7, April09/04/2025
Astronomy

Session Data

  • Date:  07/04/2025
  • Time:  02:47 – 05:09 UT
  • Seeing: I. Excellent
  • Transparency: III. Clear with slight haze
  • Temp: 6 C,
  • Air Pressure: 1023mb
  • Humidity: 87%
  • Dew Point: 4 C
  • Wind Speed: 10mph
  • Average SQM:  magn/arcsec^2

Scope: TMB 80 f/6  Camera: ZWO ASI 183MM. Darks but no Flats

All images are displayed North up and East to the left.

HT69, NGC4725

Located 5 degrees Southwest of Beta Com in Coma Berencies.

NGC4725 is a SABa barred spiral galaxy oriented NE/SW. The inner core is soft and diffuse. At each end of the bar are two spirals looking like they rotate in a clockwise direction. NGC shows it as having a diameter of 11 arc mins, but in the 315 stack I’m only seeing at to be under 10 arc min. The spiral each end of the bar seems brighter and more dense and it looks like the arm to the Northwest is longer as it heads towards the northeast.

This peculiar galaxy is thought to have only one spiral arm. This is not obvious from this observation, but go with a much deeper integration as this structure becomes visible.

12 arc min to the West of is of it is NGC4712, a little 13.5 mag SBc type galaxy. 24 arc min to the Northeast is another edge on SBcd type galaxy NGC4747 at 17.3 mag. The spiral arms of NGC 4725 appear warped due to its gravitational interaction with the nearby distorted spiral galaxy NGC 4747, located about 370,000 light-years away.

The the Northwest I’m just making out PGC86434 at 15.7 mag and to the Southeast at the very limit of this exposure I can just make out PGC1728765 at 16.7 mag and only because it is so small.

16 arc min to the east is the LX Com, a 9.0 mag K1Ve type variable. There are a number of orange /red stars in the FOV, and it would be pretty to see them here. The one downside of using mono.

Total Integration Time:  315 sec

HT63, NGC4490

Located just over 39 arc min Northwest of 8CVn Chara in Canes Venatici.

This is a weird one. There is a core, but it’s not circular or compact and is orientated in the same direction as the arms i.e Southeast/Northwest. The arms form a flat S shape laying on its side. Just to the North of the core is a small crescent shape. This must be part of the spiral arms, but it floats there detached. The whole shape looks like an irregular galaxy.

Just to the North is NGC4485. Both are interacting and moving away from each other and while I cannot see it in its entirety in this observation, there is a tidal stream of material connecting the two. Because of the interacting nature of these two systems, NGC4490 is undergoing rapid star formation of hot blue new stars.

Surrounding NGC4485 are 4 much smaller PCG galaxies, but I can only make out three of them, PGC2185640, PGC3550406 and PGC3550419.

Total Integration Time:  225 sec

C/2025 F2 SWAN

Comet C/2025 F2 (SWAN) is a long-period comet discovered in late March 2025 by the SWAN instrument aboard the Solar and Heliospheric Observatory (SOHO) spacecraft. It travelled from the distant Oort Cloud into the inner solar system. 

Astroplanner didn’t do a particularly good job at placing the target on the chart, but as usual Skytools 4 was only off by just over 2 arc mins. As best as I can estimate it from the image, I measure the tail extending about 37 arc min to the Northwest.

There is a little smearing of the core in this image stacking 11 x 15 sec subs and aligning on the stars.

Total Integration Time:  165 sec