An inferior Lagoon

cloud_cover · Post by **cloud_cover** » Thu May 19, 2011 7:59 pm

Attempted to shoot the Lagoon last night despite the full moon within 15deg of the target. Unfortunately the autoguider refused to work so 2/3 of my exposures were unusable. This is a poorly processed take of M8, nowhere near the pro-ness of remus's shot

Orion 110ED, f/7, Nikon D700, Astronomik UHC on Sphinx SXD, unguided
20x 1min exposure @ ISO3200

Would appreciate your advice and critique

Post by **rcj** » Thu May 19, 2011 9:05 pm

that's really not too bad, but why ISO3200? May stick to 800-1600... also need to balance up the blues and greens...it is a tad red... tonight is clear again, try gathering even more data!

cloud_cover · Post by **cloud_cover** » Thu May 19, 2011 9:20 pm

Originally wanted to stick to 1600 but couldn't expose long enough due to lack of guider! (Nexguide kept rebooting, wouldn't start up proper. Oh dear, and I haven't even used it once yet)
Reds are the result of a dirty trick: To try to pull out the nebulosity, I boosted the red component which seems to be the predominant color for the nebula. Yeah, but need to balance the blues a bit more.
Tonight...... too tired already!

Post by **Airconvent** » Thu May 19, 2011 10:44 pm

Yup..the high ISO made the image very grainy. You may want to apply more noise reduction through. Good attempt at the Lagoon.
Regards

cataclysm · Post by **cataclysm** » Thu May 19, 2011 10:47 pm

Hey, its pretty good!

orly_andico · Post by **orly_andico** » Fri May 20, 2011 3:59 am

I see your new goodie has come in

The image is cropped right? can you post a full image? I'm curious as to how the corners look since you're on FX and there's no flattener.

Also.. I hear that even the CG-5 can manage 1-2 minutes unguided, so the SXD should do much better. Maybe your polar alignment was off?

wucheeyiun · Post by **wucheeyiun** » Fri May 20, 2011 10:18 am

Hi kelvin...its is actually quite good, nice round stars ...Remus is right... Just try ISO 1600, the graininess will go away... and reprocess. I think 1 min is fine. Or get a larger APO like remus toa130, ap 130 or flt 132, as SXD is a capable mount.

timatworksg · Post by **timatworksg** » Fri May 20, 2011 1:22 pm

Hey it's a great attempt and great results with the set up!
Managed to grab the whole lot! Pity the guiding was screwy, but with the Lagoon you can take 1min subs. Layer several with different ISO settings. Higher ISO's for grabbing the Nebulosity and the lower ISO's for reducing the noise and darkening the areas....layer mask in PS. Need more...just duplicate the RAW files and layer on more if needed. However don't flatten and add as your losing pixels the more you flatten/adjust levels/etc etc. Adjust on separate layers and mask on the rest. Takes practice but works wonders!
How else you think all those models have perfectly smooth skin and wrinkle free...HAHA! Been there done that.

shirox · Post by **shirox** » Fri May 20, 2011 2:17 pm

wow nice!

cloud_cover · Post by **cloud_cover** » Fri May 20, 2011 3:55 pm

WCY--> TOA 130 expensive leh....... you have one to sell at a cheap price? *grin*
Normally, I'll use many more frames if I'm boosting beyond 1600: My shot of M31 in the August 2010 Punggai trip pics was using 86 frames at ISO 6400. Was actually tempted to stick to 1600 last night but quite glad I didn't: the few 1600 frames I did didn't show up nearly as much nebulosity.
I'm going to try deconvoluting the remaining 40 frames then try for another processing run. Downside to deconvoluting is introducing noise and blurring some details, which may work against me after all.....
Tim --> Eh, actually 2 mins exposed the sensor to half-histogram peak at ISO 1600. There's a UHC filter in front

As a comparison, when I removed the UHC to capture some flats and to help calibrate the "base" sky color, a similar 1 sec exposure resulted in a complete whiteout... that's how bright the sky was that night.
Yeah, this was done with layers, all using the same processed base: 2 for core and 1 for nebulosity.
How do you do darker backgrounds? My problem is that this is mainly a nebula shot so layering (even with feathering or blurring the edges) in only the nebula area will result in essentially a two-tone background.
One thing about the UHC filter though: despite being within 15deg of the full moon, there was no attempt to quell the sky color nor inverse masking to reduce light pollution: this pic was processed only with the result of DSS stacking using default parameters, then stretched on curves and histogram. The UHC filter is EFFECTIVE! However, cropped from a corner (full frame) is a rather ugly green gradient: this is extremely close to the moon.
Orly --> I'll find a FX frame and send you the corners. I did an in camera crop to DX to reduce CCD heating and since I didn't need the full FOV anyway. If I recall well, FX was rather nasty at the edges. I guess I still "need" that 110 EDQ ;) My SXD can't be polar aligned at the moment, remember? Broken altitude bolt....... *grin*