Messier 96 with trio of galaxies [Explored #74]

Messier 96 is a spiral galaxy with a bright inner ring, a fainter outer ring and a dark dust lane linking the 2. Top right is a trio of galaxies. Messier 105 is the more round of the 2 elliptical galaxies. NGC 3384 is the more elliptical and the small blue spiral galaxy is NGC 3389.

 

Technical Card

900/120mm f/7 Skywatcher Esprit 120 pro triplet refractor.

Skywatcher 1.0 x FF with 2 inch IDAS P3 LPS filter

ZWO ASI2600MC; 55 x 240 second subs, Gain 100, Offset 25, Temp = -15c.

 

EQ6 pro mount with Rowan belt drives. EQMOD control. Pegasus Astro FocusCube electronic focuser.

 

Session control; SharpCap 4.0 on laptop with WiFi link to IPad.

Automated plate solving GOTO (via ASTAP).

Automated FWHM multistar focusing +/- 200 steps at 5s and 600 gain.

 

 

40 dark frames

50 flat frames (electroluminescent panel, 2800ms exposure @ 0 gain).

 

Post processed in PixInsight 1.8.9.

 

Light Pollution and Weather:

SQM (L) 20.28 at 0030hrs.

Session clear throughout.

Temp -1.8c, Dewpoint -1.5c, Saturation 98%

 

Polar Alignment:

Error measured by PHD2= 0.1 arc minute.

RA drift + 2.16 arcsec/min

Dec drift + 0.03 arcsec/min

 

Guiding:

PHD2 guiding with ZWO ASI290mm mini /Primalucelab 240/60mm guider. Every 7th sub dithered.

RA RMS error 0.84 arcsec

Dec RMS error 0.73 arcsec

 

Astrometry:

Resolution: 0.900 arcsec/px

Rotation: 104.929 deg

Observation start time: 2023-03-14 21:19:04 UTC

Observation end time: 2023-03-15 01:18:39 UTC

Focal distance: 861.44 mm

Pixel size: 3.76 um

Field of view: 1d 15' 23.1" x 44' 57.3"

Image center: RA: 10 47 34.157 Dec: +12 13 44.96

 

Issues

Quite a lot of mechanical backlash on the focuser made me hesitant about using autofocusing frequently through the night. Im not certain that I got tight focussing. Probably needs more benchwork. UPDATE: Mechanical focuser replaced.

 

Stars are hexagonal and bright stars show pinched optics. This phenomenon is known with the Esprit 120 and is worse in cold weather, The 6 sets of 3 screws holding the lens element can be accessed by removing the dew shield and a layer of anti-reflective felt tape overlying the lenses.

UPDATE: I have backed off each of the 6 x 3 screws by 1/8 turn. It may be worthwhile experimenting with dew heating strip placement if that doesn’t work. Temp was -2c last night.

Done