Crescent Nebula

[ricksastro]

Here's an approaching full moon Ha image I was able to grab last night.   Gotta love narrowband imaging!

http://www.ricksastro.com/DSOs/NGC6888_TEC.shtml

Regards,

Rick Krejci

[dsnay]

Hi Rick,

That's just amazing!
You've inspired me again.
I'm outside imaging right now, trying to figure out how to get something out of my 400mm lens and my DSI Pro. It looks like I need a new way to mount it on my LX90 since it's apparently impossible to align the two the way I have it now and the DSI's FOV is pretty small.

So anyway, the inspiration is to go after some more Ha data on M27 right now!

ttfn,
Dave

[Jake]

Gotta love narrowband imaging!

You can say that again!  Amazing to think you can capture such detail during a full moon on
such a faint object!  I wasn't able to get half that detail during a new moon in dark sky country.

Superb work as always, Rick.  Your processing brings out tons of subtle shading, and looks very
natural to my eyes.  This is really a wonderful photo!

-Jake

[dsnay]

Hi Rick,

So anyway, the inspiration is to go after some more Ha data on M27 right now!

ttfn,
Dave

Well, that didn't work.
I guess my 13nm Ha filter just isn't narrow enough for full moon work.

Dave

[Ron]

Rick,

Great work as always

Is the area you are in pretty much light pollution free?

I get inspired too but when I step outside the inspiration level drops rather dramatically    Clouds, high humidity, mosquitoes, light pollution, and etc

Can't wait for summer vacation so I can get to a dark cool site?? 

Ron

[twilbur]

Beautiful Rick! The hi-res version really has some intricate detail! The image also shows off the surrounding nebulosity quite nicely as well. I can't believe how nice your stars are even without a field flattener, great new scope!  I guess I'm not up on the latest terms and techniques, pseudo dark subtracted? SD mask combined?

[sc02492]

Nice one, Rick.  I like the processing of the internal, feathery details.

Steve

[ricksastro]

Thanks, guys...I was very happy with this one...

I guess my 13nm Ha filter just isn't narrow enough for full moon work.

That's exactly the filter I used for this one.  And I didn't use any gradient correction or flatfielding.  I still don't buy that the 13nm pass filter is less than ideal for moonlit conditions.  I've never seen a Moon gradient on any of my images.
With the DSI Pro, you've just got to get a long enough exposure to overcome the read noise, particularly with narrowband. 

Is the area you are in pretty much light pollution free?

I've got a bit of light pollution...
http://cleardarksky.com/lp/JCVnOBMIlp.html
I'm just to the left of the central crosshair, on the border between the Red and Orange.  I'm about 3 mi from an international airport.  Due to this (as well as my severe tree situation), I can only image in the East.  It's a limitation, but one I can plan for.  I can only get to about 30-40 degrees of the horizon, so things like the lagoon, eagle...are out.   It's forcing me to think a little differently, and I'm orienting myself more towards higher resolution imaging, where the target selection is more varied.  Luckily, I was able to do a lot of widefield and southern stuff in Arizona.

pseudo dark subtracted? SD mask combined?

SD Mask is essentially Ray Gralak's Sigma combine that's built into MaximDL.

I just made up the pseudo dark subtraction thing.  THe ST2000 with the 2020 chip has very little thermal noise, similar but not quite as good as the SXV-H9.  I can get rid of the bright spots with hot pixel removal like  with the SXV, but there is still some lower level noise that I like to call "thermal rumble".  I find that I get best results by doing the hot pixel removal on both the light frame and the dark frame and then do the dark subtract.  With normal dark subtract, I'd tend to get darker "pits" in the image.  Being lazy, I didn't want to do a load of 8 minute darks, to I just used some very smooth 2 minute darks I had around.  It didn't get rid of all the "rumble", I'm sure, but it likely helped.   

This kind of stuff drives those who do everything by the books crazy.  That coupled with the fact I've never done a formal G2 color calibration draws a lot of "why not"s from many, and I can't argue with them because it's just laziness.  But it's laziness chosen to minimize time and effort with minimum expense of image quality.


Rick

[dsnay]

Thanks, guys...I was very happy with this one...

I guess my 13nm Ha filter just isn't narrow enough for full moon work.

That's exactly the filter I used for this one.  And I didn't use any gradient correction or flatfielding.  I still don't buy that the 13nm pass filter is less than ideal for moonlit conditions.  I've never seen a Moon gradient on any of my images.
With the DSI Pro, you've just got to get a long enough exposure to overcome the read noise, particularly with narrowband. 

Well it's nice to know that. Now I just have to figure out how long to go with the exposure. I was shooting 42" exposures unguided through my 400mm lens. I'm not sure I can go any longer or if that's not already too long. I don't think tracking is an issue, but the LX90 on a wedge isn't all that steady....

Dave

[lindendave]

Rick,

Been there and I'm familar with what you're talking about.

I've got a bit of light pollution...
http://cleardarksky.com/lp/JCVnOBMIlp.html
I'm just to the left of the central crosshair, on the border between the Red and Orange.  I'm about 3 mi from an international airport.  Due to this (as well as my severe tree situation), I can only image in the East.

The Clear Sky page for the area I'm in now down here I would disagree with. My map, http://cleardarksky.com/lp/BrmgAsOblp.html according to the description is more like '3' because when the Moon isn't out that is what it's like here. Regardless 'knowing' what your area and conditions are like I am totally amazed and impressed with your talent. I may not say it too much but there is a lot af very impressive talent here on ARKSKY!