M101 (The Pinwheel Galaxy)

    M101 (NGC 5457), Magnitude 7.90 Sc Spiral Galaxy, Size 22'x22', Constellation: Ursa Major.

Image Details:

• Scope: Celestron Ultima 8 OTA.
• Mount: Celestron AS-GT.
• Camera: Meade DSI.
• Configuration: f/3.3 focal reducer, both spacers.
• Effective Focal Length: 609mm, f/3.
• Exposure:  20 images @30 seconds.
• Acquisition software: Meade Envisage.
• Guiding: None.
• Location: Georgia Sky View, Indian Springs State Park, Jackson, Georgia.
• Date: 22 April 2006.
• Post Processing: Meade IP, Adobe Photoshop.
• Procedures: unsharp masking, Levels, JPG conversion.

Comments: This legendary "grand design" spiral presents a high challenge for visual observers, and is considered to be one of the hardest--if not THE hardest--of the Messiers. While its visual magnitude doesn't sound forbidding, its large face-on Sc nature brings its "real" magnitude far below the quoted 7.9. Try 14 or dimmer on for size. Nevertheless, it is doable even from fairly heavy light pollution with a C11 if you wait till it's at culmination on a nice, dry night. Don't expect to see much more than the smallish nuclear regions, however. From a dark site, this object can be impressive even with smaller apertures. I once had a splendid view of this giant from the dark, DRY skies of French Camp, Mississippi and the Mid South Star Gaze. The C8 easily revealed spiral structure and, with the aid of an OIII filter, numerous of the big bird's HII regions. This observing session was brought to an abrupt end by an incoming line of tornados (French Camp is on the southern border of the Tornado Alley), but I'd proved to myself that the Pinwheel can be approached visually with a C8.

M101, whose spiral structure was first noted by Lord Rosse, is part of a small group that lies approximately 24 million light years from our little ball of mud. 

Like most galaxies, this one didn't prove to be much of a challenge for the DSI-C. I probably need more exposure/subframes to cut back on the noise, but intimate details like the huge dust lanes near the nucleus popped right out.

Return to Uncle Rod's DSI/CCD Page