Celestial hemisphere:  Northern  ·  Constellation: Camelopardalis (Cam)  ·  Contains:  HD23476  ·  HD23594  ·  HD23603  ·  HD237185  ·  HD237188  ·  HD237191  ·  HD237196  ·  HD237201  ·  HD237204  ·  HD24141  ·  HD24298  ·  HD24395  ·  HD24410  ·  HD24430  ·  HD24717  ·  HD24758  ·  HD24853  ·  HD25226  ·  LBN 689  ·  LDN 1388  ·  Sh2-204
Sh2 204 (Discussion of Exposure Length of RGB filters), Jerry Yesavage
Powered byPixInsight

Sh2 204 (Discussion of Exposure Length of RGB filters)

Sh2 204 (Discussion of Exposure Length of RGB filters), Jerry Yesavage
Powered byPixInsight

Sh2 204 (Discussion of Exposure Length of RGB filters)

Equipment

Loading...

Acquisition details

Loading...

Description

Another Sharpless2 object that is seen in the context of the surrounding H-alpha clouds thanks to the CMOS chip and stretching optimized with GHS. 

GHS Forum Discussion

Followed GHS Dave's suggestion to represent Hb as 20% of Ha as Blue in the coloring of this image.  I think it looks better, but hard to tell?  
(C is without the Blue). 
Nice discussion on Cloudy Nights.

Discussion of Exposure Length of RGB filters

One more little thing I have noticed on stars is that the transmission levels (of photons) may vary very slightly even with "balanced' filters.  There is a nice discussion on Cloudy nights: 

https://www.cloudynights.com/topic/817210-lrgb-exposure-ratios-snr-balance-and-color-balance-for-qhy-600m/

"The relative signal in each passband for L, R, G, B is

RelativeSignalQHY   = {3.13, 1.00, 1.14, 1.05}   QHY QE curve"

This may not look like much, but this is 14% more G than R.  I was wondering why green was showing up in both R and B stars... maybe this is why.... of course I have different equipment, but I think the principles hold.

This resulted in my changing the exposures of my RGB to 22 19 and 21 seconds respectively.  These numbers were calculated to be optimal at 22 (sounds very low but higher blows out the centers of the stars in the ZWO) .  Anyway, in PixInsight there is now less G in these stars.... seen by holding the cursor over the star and left button clicking.

Prior Version:


Sh2 204 H-alpha RGB



From GalaxyMap:

Avedisova says that Sh 2-204 is likely ionised by four O-class stars that are part of the Cam OB3 association. These are BD +56 864 (O6 V), HD 24372 (O9.5 Ib), Hiltner 52 (O7.5 V) and BD +56 866 (O9 V).

The reference to HD 24372 appears to be an error because SIMBAD lists this as a F5V star in a completely different direction. Presumably Avedisova meant HD 237211 as this is a O9.5Iab star in the direction of Cam OB3. SIMBAD gives a cooler B0.5IV class for Hiltner 52.

The distance estimates from Avedisova and Russeil both place this nebula beyond the Perseus arm and possibly associate it with the Norma/Outer arm.
However, a 2005 study connects Sh 2-204 to the much closer Cam OB1 association.

GENERAL NOTE ON SHARPLESS2 OBJECTS>>>>>>>>>>>>>

There are 313 Sh2 objects.  All now imaged.

This is my collection:

Sharpless2

Wide-Angle Hydrogen Alpha Nikon Image Sh2 79-171

Please note there is also a Sharpless2 Group with now more than 2700 examples.

Sharpless2 Group

Other useful links include:

Gary Imm's Collection

GalaxyMap's Collection

The Sharpless Catalog

The MDW H-alpha Sky Survey

Reiner Vogel's detailed observing catalog

Hope you enjoy these obscure but interesting objects...

Comments

Revisions

  • Final
    Sh2 204 (Discussion of Exposure Length of RGB filters), Jerry Yesavage
    Original
  • Sh2 204 (Discussion of Exposure Length of RGB filters), Jerry Yesavage
    B

B

Title: NB Destarred

Uploaded: ...

Sky plot

Sky plot

Histogram

Sh2 204 (Discussion of Exposure Length of RGB filters), Jerry Yesavage

In these collections

Sharpless2 Objects