Messier 97 and 108 with Equinox 120ED scope [Explored]

This image from Ursa Major shows two Messier objects in the same field. They are 48 arcminutes apart. Many of the small background "stars" here are actually distant galaxies.

 

The Owl planetary nebula is about 3.7 arcminutes across in our sky but is actually 0.91 light years in diameter. It lies about 2600 light years distant. The central star has shed its outer layers which glow either red (hydrogen) or green-blue (oxygen) lit by the light of the remnant white dwarf star. Eventually, the star will cool and the gas will expand until the nebula fades away.

 

Barred spiral galaxy M108 is about 45 million light years away and is almost edge on from our perspective. It’s 8.7 x 2.2 arcminutes diameter in our sky. It lacks a prominent core or bulge but has numerous dust lanes. A Type II supernovae was observed here in 1969. It’s possible to see brownish dust lanes, pink hydrogen alpha zones and two bright blue stellar “associations” of young stars at this magnification.

 

900/120mm f/7.5 Equinox ED doublet refractor.

Skywatcher x 0.85 FR with 2 inch IDAS LPS D2 filter

MoonLite electronic focuser

Astro-modified Canon 80D at ISO400; 24 x 10 minute subs

 

NEQ6 pro mount with Rowan belt drives -2 star align.

Camera control with Backyard EOS

 

60 Flats EL panel: 1/40s @ ISO400

81 Darks @ 5-10c

Master Bias from Library, 04/2020

 

Camera sensor temperature (external battery): 5-6c

 

Post processed in PixInsight 1.8.8 and Photoshop CC 2021.

 

Local parameters:

Temp: 3.0 - 4.2c

Humidity: 65.4%

Pressure: 1017 hPa

 

Light Pollution and Weather:

 

SQM (L) at end of session (0132 hrs UT) =20.10 mag/arcsec2.

Clear, all subs good.

 

Polar Alignment:

QHY Polemaster alignment -

Error measured by PHD2= 1.2 arc minute.

RA drift + 0.68 arcsec/min

Dec drift + 0.85 arcsec/min

 

Guiding:

PHD2 guiding with ZWO ASI290mm/PrimaLuce Lab 240/60mm guide scope. Every 3rd shot dithered.

RA RMS error 0.67 arcsec, peak error -2.33 arcsec

Dec RMS error 0.46 arcsec, peak error -1.93 arcsec

 

Astrometry:

Center (RA): 11h 13m 12.488s

Center (Dec): +55° 17' 53.98"

Size: 1d 20m 11.6s x 54m 56.0s

Image scale: 0.977 arcsec/pixel

Focal distance: 781.48mm

Pixel Size 3.7 microm

 

 

Had some problems with this - although guiding parameters were excellent, I've got some trailing which might be due to differential flexure - my guide scope is comprised of a main tube, coarse focuser and helical focuser and there was a bit of loose play at each junction. Have tightened the grub screws up and will make sure scope is tightly aligned with main scope.

 

Secondly, Ive got red haloes around the bright stars - not the blue/violet you would expect with a doublet scope - the last time I had this problem, it was due to a IDAS LPS D2 clip in filter. I usually use the D1 version without issues. Funny that it has resurfaced with the 2 inch D2 filter currently fitted in my field flattener - think it will have to go!

 

 

Can fix these with a little bench work I hope.

Done