Object

M101 (NGC 5457) The Pinwheel Galaxy

Object Information

Image information

Object Type

Galaxy (Spiral) Type Sc

Instrument

LX200GPS 14” OTA @ F5 effective FL≈1778mm

Constellation

Ursa Major

Guiding

SXV / SkyWatcher 80mm achro @ F/6

Magnitude

+7.9

Focal Reducer

Optec NextGen 0.5x

Coordinates

RA 14:03.2 Dec +54:21

Mount

Paramount ME

Size

22 arc min

Location

Stoney Hills, S.E England

Distance

25 Million Light Years

Acquisition Date

17 - 19th April 2007

Notes

M101 is one of the the most prominent ‘Grand Design’ spiral galaxies visible. At first sight doesn’t look unusual but closer examination shows the central core to be significantly off centre. Halton Arp therefore listed it in his catalogue of peculiar galaxies.

At over 170000 light years across M101 is one of the largest galaxies known.

M101 was discovered by Pierre Méchain on March 27th 1781.

Capture Device

Starlight-Xpress SXV-H9 Sony ICX285AL Exview HAD Cooled CCD Array 1392 x 1040 @ 6.45uM / Pixel 

Filter Type

Astronomik Type IIc RGB

Colour Technique

LRGB

FOV

≈16.38 x 12.24 arc mins (0.706 arcsec/pixel)

Exposure

473 m (7.9 hours)Total

Integration

L (40 x 250 sec bin 1x1)

R (24 x 254 sec bin 2x2)

G (27 x 200 sec bin 2x2)

B (24 x 286 sec bin 2x2)

Notes

Luminence exposures above 3 pixels FWHM rejected in CCDInspector. Sub exposures stacked and sigma combined in Maxim - bias and flat calibrations applied. Post processing in PSCS2

From the previous imaging run of M63 polar alignment of the the mount was improved giving better but still not great tracking. Arc second excursions still occasionally happened. During this run I started to have some success in applying Periodic Corrections to the Paramount ME robotic mount to reduce its 2 arc second P-P natural periodic error. These adjustments are giving sharper details with more contrast and rounder stars on each successive imaging run.