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Monday, February 6, 2017

A new photo, Sharpless 188 (Sh2-188) in Cassiopeia

Kind of difficult target due to dim outer parts at left in my photo. I collected lights for this object couple of nights between. and 21. January 2017. This photo is also a good sample of my new imaging method VARES (Variable Resolution imaging). More info in technical details bellow.

Sharpless 188, a Planetary Nebula in Cassiopeia
Please, click for a large image

Image is in mapped colours, from the emission of ionized elements, R=Sulphur, G=Hydrogen and B=Oxygen.

Sh2-188 in visual colors
Please, click for a large image

Image is in Natural colour palette from the emission of ionized elements, 
R=Hydrogen + Sulphur, G=Oxygen and B=Oxygen + ~10% Hydrogen.

Sh2-188, H-alpha emission alone
Please, click for a large image


Sh2-188 (Sharpless2 188) a planetary nebula that is moving through the Inter Stellar Medium. The nebula is considered to be one of the most extreme examples of planetary nebula and ISM interaction. The bright parts of the filamentary rim is the shock front with a faint tail of material stretching away at opposite direction. (Source,

Technical details

A new immaging technique of mine was used for this photo. I call it VARES (Variable Resolution imaging). The data is collected by using different binning levels from 1x1 down to 6x6. High signal/noise elements, like brighter stars and more luminous parts of the nebula, are from less binned exposures. Low signal/noise elements, like very dim and featureless outer parts, are from more binned exposures, this time all the way down to bin 6x6. (Apogee Alta U16 has a 4096 x 4096 pixels CCD. At bin 6 x 6, the output image has still 682 x 682 pixels in it)

Total exposure time for H-alpha is  12h but if the effects of binning is calculated in, the signal is practically the same as from 140 hours of exposures, if all are binned 1x1!
With this method, I can have high resolution details and good S/N for dimmer, less detailed, parts of the nebula with minimal exposure time.

In near future, I will write a tutorial about the VARES method. It might take some time though.

Processing work flow

Image acquisition, MaxiDL v5.07.
Stacked and calibrated in CCDStack2.
Deconvolution with a CCDStack2 Positive Constraint, 33 iterations, added at 50% weight
Color combine in PS CS3
Levels and curves in PS CS3.

Imaging optics
Celestron Edge HD 1100 @ f10 with 0,7 focal reducer for Edge HD 1100 telescope

10-micron 1000

Cameras and filters
Imaging camera Apogee Alta U16 and Apogee seven slot filter wheel
Guider camera, Lodestar x 2 and SXV-AOL

Astrodon filter, 5nm H-alpha
Astrodon filter, 3nm O-III
Astrodon filter, 3nm S-II

Exposure times
H-alpha, 6x 1200s, binned 1x1 = 2h
H-alpha, 21x 1200s, binned 2x2 = 7h
H-alpha, 9x 1200s, binned 6x6 = 3h
O-III, 3 x 1200s binned 6x6 = 1h 
S-II,  3 x 1200s binned 6x6 = 1h 
Total 14h

A single uncropped, calibrated and stretched 20 min. H-alpha frame as it comes from the camera

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