Astrophotography with a bright moon

Every month astrophotographers cringe at two words "full moon" as the great glowing orb in the sky makes it very difficult to image. Narrowband or photographing the moon are the two main options if you want to take advantage, as I do, of the few clear nights I get (even if it falls on a full or near-full moon). A few days past the full moon this month I noticed the moon rising with a beautiful orange color. I realized that it would pass right by the tree in my front yard where the cherry blossoms are currently blooming so I popped out with my camera to catch it.

This is a combination of two photos, taken at the same exposure but different focuses then merged so both the moon and the cherry blossoms would be in focus in the final product. The tree was lit up by an off camera flash, hand-held the lower left of the camera and set to fire at the last moment of exposure.

First Bicolor Narrowband Image

I have imaged various objects in just Ha before, but just got to use my OIII filter for the first time and am attempting my first bi-color processing. I am hoping to get more hours of both Ha and OIII in the coming days or weeks (whatever the weather will allow).

This is 3 hrs of Ha and an hour of OIII (yes I need more, I have trees which are preventing me from imaging this target for too long in any one night).

I think I have a method (albeit convoluted) that gets a result I like. Basically I have combined portions of all the various bicolor processing techniques I found. A little of Cannistra's, a little of JPM's tone-mapping, a little of my own mixture and PS actions and alot of layers and masks. For only 6 hrs of data (3hrs each of Ha and OIII) I think I have pulled out a good bit of detail and data, at least enough to make make me happy. I also found a balance of colors that I like (although I know with NB this is basically personal preference).

Here is also a crop of one edge of the nebula, I am happy with how this is coming along and am hoping with more data I will really get this region especially to "pop": 

Image Details: 
Imaging Camera: Atik 314L+
Imaging Scope: Orion EON80ED
Tracking & guiding scope: Celestron CPC800XLT
Guide Camera: Starlight XPress Lodestar
Filters: Astronomik Ha 12nm, Astronomik OIII 12nm
Location: fairly dark in the middle of nowhere Suffolk, England
Set temp on camera: -5C
Preprocessed & Stacked in Nebulosity
All post processing done in Photoshop CS2

Color to M51

Finally got another clear night and was able to grab 100 minutes each of RGB.

Here is the final (for now) LRGB version:
















You can see it larger on My Flickr

First image in England and of 2011

Despite a lot of rain and clouds I have gotten a couple (literally, only 2 since we moved here in December) of clear nights to image. Using my new autoguider (Starlight XPress Lodestar) I am now able to get much longer exposures. I kept these at 10 min subs although I could have gone longer, but didn't want to push it too much my first time autoguiding. I still need a few more nights to get color data, but I am happy with how the Luminance has turned out so wanted to go ahead and post it.

This is 4 hrs of Luminance data, spread over two nights (total of 24 x 600s). Unfortunately I didn't orient the camera exactly the same for one hour the 2nd night (oops!!! At least I noticed then and was able to fix it for the rest of the session) so the edges don't have quite as much detail and depth, though the main portion is all 4 hrs.


Details:
Scope: Orion EON80ED piggybacked on Celestron CPC800
Cameras: Imaging - Atik 314L+, Guide - Starlight Xpress Lodestar
Filters: Astronomik Luminance
Location: Suffolk, England
Sub details: 24 x 600s, preprocessed with flats and darks
Software: Nebulosity (preprocessing and stacking), Photoshop CS2 (post-processing)

Full frame:

Crop of central area: 

The argument about Bias Frames

Until now I have not really used bias frames in my preprocessing (I attempted on the first few imaging attempts ever since I was told I should but quickly stopped using them). I decided to shoot some with my last imaging session and have been trying to compare whether or not they helped at all in the image. 

I did the exact same processing from stack to finish on all three variations except how the bias frames were applied. The first comparison set is just a center crop of M51 from my full frame.

-The first one has no bias at all
-The 2nd had bias frames preprocessed on both the flat and dark frames themselves as well as the preprocessing for the light subs 
-The 3rd had bias frames preprocessed on just the flat and light subs

So the 1st and 3rd appear identical (even when blinking between the two on a super-zoomed level) The 2nd seems the worst, which is what I suspected as I had been told if you add the bias to both the light and dark in Nebulosity it will basically add it back in. 

From this comparison (and the 200% crop) it really almost doesn't seem worth it.


However, since I posted this observation on various astronomy forums I frequent I have all but gotten "shot at dawn" as one guy so eloquently put it. I have been told that flats WILL NOT work if you don't apply bias frames to them (interesting since I have not used bias frames since I started imaging and my flats have been working perfectly well) ... I have also been told that I really only need them if I am going to use scaled darks, which makes much more sense to me than the "nothing will work right if you don't use them" argument. 


Seeing as they take almost no time to shoot and add into my pre-processing steps I might as well use them to avoid further ridicule but seriously - see if you can really tell a difference in these 100% and 200% crops of the M51 image I am currently imaging. 

Also, according to Ron Wodaski's "The New CCD Astronomy", pg 244: 
"The sole purpose of a bias frame is to allow you to use dark frames whose exposure time does not match the light frame exposure time. If you always take dark frames with the same exposure as your light frames, you do not need to take bias frames" .... 


Since I don't use scaled darks this explains my results and I am officially ignoring all the contradictory and argumentative (& some downright rude) comments I have been getting to this question on my astronomy forums.