8" f5 Newtonian reflector

 ST-8XME, self-guided, binned 1x1, temp -20c, camera control MaxIm DL 4.56

Lumicon Red filter, 660 minutes (66 x 10 minute subs), 02/8/9/10/2011; seeing 2.8-3.9 FWHM per CCDStack

CCDStack 2.17.3996.27523, Photoshop 7.0

 Rolling Roof Observatory, Thousand Oaks, CA 91360 (+34d 13m 29s -118h 52m 20s)

Contemporary Visual Observation(s) for NGC 2403

NGC 2403 = UGC 03918 = MCG +11-10-007 = CGCG 309-040 = CGCG 310-003 = PGC 21396
07 36 54.5 +65 35 58
V = 08.5;  Size 21.9x12.3;  SB = 14.4;  PA = 127d

18" (3/19/04): at 160x, this chaotic spiral displayed a tremendous wealth of 
detail with two broad, diffuse spiral arms, dark lanes, mottling and a few 
obvious giant HII regions.  A number of stars are superimposed including two mag 
11 stars.  I focused on observing the HII regions were best viewed at 323x:

The brightest is the HII complex N2404 on the east side of the core 1.5' from 
center and 1.5' N of a mag 11 star to the SW of the core.  This knot is fairly 
bright at 323x, perhaps 15" diameter and irregularly round.

On the NW side of the halo is a collinear string, consisting of two stars along 
with a fuzzy knot, oriented from SW to NE.  This HII knot (IRAS 07315+6543) 
forms the SW end of the string and is clearly nonstellar at 323x, ~15' diameter.  
It can also be pinpointed 2.4' NW of the mag 11 star west of the core (middle of 
3 in a E-W string).

At the NNW edge of the core is a mag 13.5 "star" which does not focus and 
appears to be another HII knot.  Close following is a fainter, but definite 
nonstellar knot ~10" diameter.

Finally, returning to the E-W line of three stars on the west side of the 
galaxy, the eastern star in this trio is just on the SW edge of the core and 
close south is a fainter mag 14 "star" which has a weak nebulous glow attached.

17.5" (2/27/87): very bright, very large, bright core, elongated 5:2 NW-SE, 
15'x6'.  Impressive galaxy with spiral structure clearly visible.  Two spiral 
arms are attached at opposite ends of the main body and both wind almost 180?.  
The tip of the northern arm ends at the emission nebula N2404.  Several stars 
are superimposed including two mag 11 stars.

17.5" (2/27/87): two spiral arms are visible on attached at the opposite sides 
of the galaxy and winding a half of revolution.  The northern arm ends at the 
HII knot N2404.  The galaxy has a mottled appearance.

13" (1/11/86): spiral arm definite on the west side of the galaxy with a dark 
gap between this arm and the main body (core).  This feature is very faint but 
definite with averted.

13" (12/24/84): spiral arm highly suspected attached at the west side winding 
along the north side to the faint knot = N2404.

13" (1/28/84): very bright, large bright core.  N2404 is clearly visible as a 
faint, very small nebulous knot along the east side of the galaxy.  Spiral 
structure (arms) is just suspected.  On 3/24/84 the knot was difficult to view 
at 144, but on 1/11/86 was fairly easy.

8" (1/1/84): bright, large, bright core, faint star superimposed, mottled?

- by Steve Gottlieb

NGC 2404 is the brightest superassociation in NGC 2403.  The NGC position, 
however, is wrong, as is the position in Bigourdan's first Comptes Rendus 
paper.  The correct position appears twice in his lists of new nebulae in his
massive "Observations ...," and the offsets he gives also reduce to the 
correct position.

My earlier incorrect identification of this as a star is based on the NGC
position. - Dr. Harold G. Corwin, Jr.

NGC 2403.  See NGC 2253 and NGC 2404. - Dr. Harold G. Corwin, Jr.

NGC 2404
07 37 07.1 +65 36 39

18" (3/19/04): brightest of 3 or 4 HII regions visible in N2403.  Fairly bright 
at 160x, small, round.  Located just east of the core, 1.5' from center, and 
1.5' N of a prominent mag 11 star to the SW of the core.

17.5" (2/22/87): this is a prominent knot (superassociation) located at the end 
of the northern spiral arm of N2403.  Appears fairly faint, small, round, 
clearly nonstellar.

13": extremely small emission "knot" at the E end of N2403.

Superassociation/HII region in N2403 discovered by Bigourdan.  The NGC position 
is in error but later measured accurately by Bigourdan. Listed as nonexistent 
(T7) in the RNGC although type 35 would be more appropriate.  See RNGC 
Corrections #2.

- by Steve Gottlieb

NGC 2404 is the brightest superassociation in NGC 2403.  The NGC position, 
however, is wrong, as is the position in Bigourdan's first Comptes Rendus 
paper.  The correct position appears twice in his lists of new nebulae in his
massive "Observations ...," and the offsets he gives also reduce to the 
correct position.

My earlier incorrect identification of this as a star is based on the NGC
position. - Dr. Harold G. Corwin, Jr.