Rosette Nebula (L-eNhance filter, 95% Full Moon) [Explored #73]

I’ve always avoided doing DSOs in Moonlight but a while back, I bought an Optolong L-eNhance Triband filter which can be helpful in reducing light pollution and stray Moonlight – it predominantly passes 3 narrow band widths centred on:

Hydrogen Alpha: Red, 656.4 nm
Oxygen III: Green, 500.7nm
Hydrogen Beta: Green-Blue, 486 nm

The filter is certainly more opaque than my standard IDAS P3 light pollution suppression filter. Usually my flats are exposed at 1600ms but for this filter it was 6500ms at 0 gain. Autofocus and plate solving exposures were 2s at 578 gain.

The raw image was lacking in contrast – not surprising given the Moonlight but I’ve used curves enhancement and local contrast enhancement in PixInsight to improve that. I haven’t altered the colour palette as this was a first test for this filter.

Technical Card
480/80mm f/6 Altair Starwave triplet refractor.
Altair Planostar 1.0 x FF with 2 inch L-eNhance filter
ZWO ASI2600MC; 39 x 360 second subs, Gain 100, Offset 25, Temp = -15c.

EQ6 pro mount with Rowan belt drives. EQMOD control. Primalucelab Sesto Senso electronic focuser.

Session control; SharpCap 4.0 on laptop with WiFi link to IPad.
Automated plate solving GOTO.
Automated FWHM multistar focusing every 16 frames. +/- 500 steps at 2s and 578 gain.

20 dark frames
50 flat frames (electroluminescent panel, 6500ms exposure @ 0 gain).

Post processed in PixInsight 1.8.9.

Light Pollution and Weather:
SQM (L) not recorded – 95% Moon
Session ended by cloud, target was also very near roof level.

Polar Alignment:
Resumed from previous Park.
Error measured by PHD2= 0 arc minute.
RA drift + 2.44 arcsec/min
Dec drift – 0 arcsec/min

Guiding:
PHD2 guiding with ZWO ASI290mm/Altair Starwave 206/50mm guider. Every 4th sub dithered.
RA RMS error 1.1 arcsec
Dec RMS error 0.82 arcsec

Astrometry:
Resolution: 1.612 arcsec/px
Rotation: -87.819 deg
Observation start time: 2023-02-07 20:41:29 UTC
Observation end time: 2023-02-08 01:09:49 UTC
Focal distance: 481.13 mm
Pixel size: 3.76 um
Field of view: 2d 9′ 37.7" x 1d 41′ 33.2"
Image centre: RA: 6 32 17.164 Dec: +4 58 40.33

Posted by john.purvis on 2023-02-08 17:03:39

Tagged: , Astrophotography , L-eNhance , Rosette nebula , NGC 2244 , Caldwell 49 , Caldwell 50