Processing astronomy pictures has always stressed computer systems. (Newer DSLR cameras, like my Nikon D610 with 24.3 megapixel images or my D810 with 36 MP (and now D850 with 45.7 megapixels), also create large files that are difficult for even fast computers to handle in bulk.) New image processing techniques, such as drizzle and deconvolution algorithms, are extremely computer-intensive. (More on the equipment used to capture the images is here.)

Software for Image Processing

It turns out I've acquired and use quite a number of astronomy and image processing titles. The following work OK with Windows 7, 64bit:

• PixInsight

• MaximDL 5 - Controls the SBIG ST-8300M camera and filter wheel, also does batch image process which I use for image reduction (i.e., flats, darks, etc.)

• Nebulosity - Control the QHY8 CCD camera, capture .fit files...

• Photoshop - Check image quality while imaging, and final processing; it is the last tool I use to process images for publication (CS2 and CS5)

• Registar - Combine images, my primary 'stacking' tool

• ImagesPlus - Process DSLR images

• Neat Image - Noise reduction

• Noel Carboni's Astronomy Tools - Photoshop actions to do things like select stars and tighten them up

• GradientXterminator - Photoshop plugin to remove unwanted gradients

• Deep Sky Stacker - Drizzle combinations and some stacking

• The Sky (I have 5, 6, and X)

Not in use:

Welcome to astronomy.tools. A collection of useful, free astronomy tools. FOV Calculator Star Chart Cloud Forecast Lookup Coordinates Cookie Policy.

• Carboni's Astronomy Tools by Noel Carboni's Astro Tools for PhotoShop Some images (view more) M101 - The Pinwheel Galaxy.
• Noel Carboni's Astronomy Tools - Photoshop actions to do things like select stars and tighten them up. GradientXterminator - Photoshop plugin to remove unwanted gradients. Deep Sky Stacker - Drizzle combinations and some stacking. The Sky (I have 5, 6, and X) Not in use.
• Dec 25, 2019 SHA fr, in Agriculture, is the handle of a tool or implement, such as a spade, fork. And Noel Carboni's Astronomy Tools plugin for only $20. LRGB images, but for this tutorial, I'll process a set of DSLR images. The goal isn't to fill the entire range, but just to widen your peaks.
• Noel Carboni's Astronomy Tools is a great set to start with. It includes a couple of noise reduction actions that would eliminate the need for something else. His AstroFlat Pro works well for removing gradients if you have that issue. I've used it and GradientXterminator.

• GoldFocus - Software that works in conjunction with a bahtinov mask to analyze and announce focus corrections - did not work well for me

• CCDSoft - This came with my SBIG ST-8300 camera. Prerelease v206 controls the new filter wheel. This software performs many of the functions of the separate programs below. I find it also has many annoying behaviors, especially when focusing with the focus windows being tiny and partially hidden.

• AIP4WIN - deconvolution - seems to have stopped working after an upgrade somewhere but I haven't pursued it

Hardware for Image Processing

New Desktop July 2019 System:

• Processor: Intel Core i9-9900K Desktop Processor 8 Cores up to 5.0 GHz Turbo unlocked LGA1151 300 Series 95W

• CPU Cooler: (Going with an air-cooled solution for now) Noctua NH-D15, Premium CPU Cooler with 2x NF-A15 PWM 140mm Fans

• 64GB Memory: CORSAIR DOMINATOR PLATINUM 64GB (4x16GB) DDR4 3200MHz C16 Desktop Memory - CMD64GX4M4C3200C16

• Motherboard: ASRock Z390 Taichi Ultimate (link) - This is one of the few Mobos that supports 8 SATA channels, which I really needed due to the large # of disk drives I run to hold all my pics

• Graphics Card (2070): EVGA GeForce RTX 2070 XC Ultra Gaming, 8GB GDDR6, Dual HDB Fans & RGB LED Graphics Card 08G-P4-2173-KR

• Case: Phanteks Enthoo Series Primo Aluminum ATX Ultimate Full Tower Computer Case PH-ES813P_BL (link)

• OS/Boot Drive: Samsung 970 EVO Plus Series - 1TB PCIe NVMe - M.2 Internal SSD (MZ-V7S1T0B/AM)

• Working Photographs Drive: Samsung 970 EVO Plus Series - 2TB PCIe NVMe - M.2 Internal SSD (MZ-V7S2T0B/AM)

• Optical Drive: LG Electronics 14x SATA Blu-ray Internal Rewriter without Software, Black (WH14NS40)

• Power Supply: EVGA Supernova 850 G3, 80 Plus Gold 850W, Fully Modular, Eco Mode with New HDB Fan, 10 Year Warranty, Includes Power ON Self Tester, Compact 150mm Size, Power Supply 220-G3-0850-X1

2019 Laptop:

• Dell XPS 15 7590

• 9th Generation Intel(R) Core(T M) i9-9980HK (16MB Cache, up t o 5.0 GHz, 8 cores)

• NVIDIA(R) GeForce(R) GTX 1650 4GB GDDR5

• 15.6' 4K UHD (3840 x 2160) InfinityEdge Anti-Reflective Touch IPS 100% AdobeRGB 500-Nits d isplay

• 32GB DDR4-2666MHz, 2x16G

• 2TB PCIe Solid State Drive6-Cell 97WHr Integrated

• 130W Power Adapter

Old Laptop: I acquired a new laptop for field processing 4/2014: ASUS ROG G750JZ-DS71 17.3-inch Gaming Laptop, GeForce GTX 880M Graphics

• Intel Core i7-4700HQ 2.4Ghz (Turbo 3.4 GHz)

• 24 GB DDR3 (twice my desktop's memory!)

• 1TB 7200 rpm HD, 128GB x 2 (256 GB Total) Solid-State Drive

• 17.3-Inch matte screen, 1920x1080 pixels ('full HD'), contrast 950:1, color gamut 95% of sRGB and 74% of Adobe RGB

• Blu-ray BD-ROM

• Windows 8.1 - Quite a learning curve here. The only thing I've found a problem with after a couple days is 'Scrabble Online' which won't install... Now on Windows 10 so I can use the whole 32GB memory.

This laptop replaces my old Dell Dell Inspiron N7010, which was not able to process my all-night DSLR time-lapse images effectively... Working with those files in Bridge or Nikon ViewNX 2 was an exercise in frustration.

Desktop: My old desktop system vintage mid 2011: At that time I was toying with the idea of upgrading my computer system, then Fry's sealed the deal by putting the motherboard and processor I wanted on sale! I'm using the fastest Intel Sandy Bridge processor chip. These new chips bring top of the line processing power to a cool running and affordable CPU, reducing the cost for Intel's top performance by many hundreds of dollars, and reducing the power use (and heat generated) by your computer. It also has a very decent display processor as part of the chip, which performs much better than the dedicated graphics card in my previous (which was a 4 year old) system. This means a cooler, quieter case because I (didn't use to) need a graphics card... But that changed when I went to a Dell U3011 30' monitor with 2560x1600 pixels, and I acquired an AMD Radeon HD 5700 Series display adapter. That card caused all sorts of wierd problems resolved by the GTX960 upgrade. Here are the specs for the major components of the new system:

• ASUS P8Z68V Pro Motherboard, Intel® Socket 1155 for 2^nd Generation Core™ i7/Core™ i5/Core™ i3 Processors

• Corsair 115GB SSD (Solid State Drive) - Force CSSD-F115GB2-BRKT-A 2.5' 115GB SATA II MLC Internal Solid State Drive (SSD) (Since upgraded to a Samsung 500 GB SSD)

• Intel® Core™ i7-2600K Processor (8M Cache, 3.40 GHz), LGA 1155 (I am overclocking this to 4.43 GHz for about a 30% speed increase.)

• Corsair XMS3 3x4GB DDR3 2000MHZ memory (looking for a 4th module) Since replaced and upgraded to 32GB, and with Photoshop and Registar I actually use more than 24GB!

• 2 x Hitachi 3TB Coolspin 32MB Cache SATA3 (5400 rpm model) (Since upgraded to two 10TB and two 8TB drivers plus an 2 SSDs)

• CPU cooled with a Noctua NH-C14

• Seasonic X Series 850W power supply (replaced Corsair 600W GS 600 PSU)

• ASUS GEFORCE GTX960 video card - the fans don't spin during normal operation!

• LG 12x Blu-Ray writer

• And went to an ASUS RT-N56U Dual Band router which (2014 note) has been a complete PITA and has been replaced as noted next:

• Sadly my computer room isn't hard-wired with Ethernet so I'm using a D-Link AC 1200 as a Range Extender (HW Ver. A2 F/W 1.02) & it works well. My main router is now a TP-Link Wireless Router Archer C9. I'm connected with a Asus PCE-N15 11n Wireless LAN PCI-E Card.

Here are some overclocking references on the setup as I sort everything out. It looks like people are hitting 5.0 GHz with some frequency and 4.5 GHz range just about always with a setup like mine. As noted above, as of 7/15/11 I'm running at 4.43 Ghz: As of 9/14, this processor is still near the top of it's class in speed as compared with other intel processors.

HardOCP, hardforum, Toms, HardwareCanucks, Overclock.net,

Scroll down for for pictures of the desktop. The massive Noctua CPU cooler assembly was the last major component to go in, and after that it was time to hide the wires..

Dick's Summer 2011 Computer Project

The front fan doors are open in this shot. There are 7 large (120mm) fans that come with the DF85 frame (2 on top you can't see). Plus the CPU has two monster (140mm) fans. The big fans move a lot of air. I run the case fans on low, and the CPU fans on the medium setting, making for a surprisingly quiet package providing enough cooling for 4.4 GHZ overclocking stress tests. As for the case style, it does look like something an 18 year old might choose, and I'm not sure an interior decorator would put this color combination together. The case was the best Fry's had in the store the day I was putting the system together, so fate pretty much determined it. I'm more of a function over form guy, but I may decide to get an LED side case fan to maybe balance everything out ;-)

Cooling Transplant Coming Up! Note the relative size of the currently installed Intel 'stock' cooler. The Intel guy did not like first stress test I threw it (board temp exceeded 85 deg C), so I knew I had to step up the cooling. The new cooler keeps the temps under 70 under the worst conditions, at least so far.

Astronomy Tools Calculator

Hitachi 5400 RPM drives (bottom, 2x 3GB) provide the pure space part of the storage system, while a 115GB SSD drive (out of sight at the bottom of the case) holds Windows 7 and the applications for a super-responsive system. The case provides plug-in disk drive ports for simple disk swaps. There are 4xSATA 3 (6GBit/s) 4xSATA 2 (3Gbit/s) ports, plus an E-SATA port providing support for up to 9 SATA storage devices.

The right side panel will cover the wires. Believe it or not, I tried to be very careful where I placed the wires on the computer, since the case I ended up with has a clear side door. The case provides a number of convenient routing paths that make this a bit easier. The disk drive wires were tough (yellow and red) to run to the bottom as a pass through area didn't quite line up with the board connectors.

Laptop Upgrade Discussion from 2011:

Multiple Core Computers are critical for image processing! I found my 2004 model single-core laptop just wasn't cutting it when processing images in the field, and I've been watching laptop prices and features carefully since the new Intel 'Core I-' processors came out. Best Buy had a good deal and 11/2010 I acquired a Dell Inspiron N7010 laptop with these features: 17.3' LED screen, Blu-ray optical drive, 640GB hard drive, 6GB memory, Windows 7 64-bit OS, and a Intel Core I5-460M processor. (There has been a worldwide shortage of blu-ray drives for notebook computers, and laptops with blu-ray are hard to find and command a premium price.) Complete specs for the true geeks are further below.

Compatibility: I recently cautioned people regarding 64-bit Windows for astronomy applications due to possible compatibility issues. The advantage of 64-bit operating systems and software is that they can address (use) more than 4GB of memory, which is helpful in processing large amounts of image data. My QHY8 CCD Camera now has 64-bit compatible drivers, which opened up the 64-bit door for me.

Astronomy software compatibility problems with Windows 7:

• As of early 2011 just about everything is working with Windows 7. However, William-Bell's Megastar will not install. I have not received a response to my emailed request for information about work-arounds or future support for 64 bit windows. However, you can manually copy files to your computer and get Megastar to run.

• Happily haven't had any other problems!

New Quad Core, widescreen laptop (left), old workhorse dell on right

The Sky X on the newer Dell, The Sky 6 on the right

Copyright © by Dick Locke. All Rights Reserved.
Contact and Image Use Information

Late 2016 I acquired a Synology DiskStation DS916+ 4-Bay NAS Enclosure and 4 WD 8TB Red 5400 rpm SATA III 3.5' Internal NAS HDD drives.

Reference speeds:

Megabyte (MB) or Megabyte per second (MBps, MB/s) — a unit used for file sizes and often in the end user software, including NetWorx, and
Megabit (Mb) or Megabit per second (Mbps, Mb/s) — a unit used for download speeds advertised by ISPs and reported by on-line tools.

10 MB/s (Bytes)= 80 Mb/s (bits)

Current Astrophotography Capture Equipment
Advanced blending in Photoshop is discussed on my page here

Nikon D810A Capture and Image Processing Workflow

I have struggled a bit in finding a suitable image processing workflow with the Nikon D810A. Here's what I do right now, followed by a discussion of what did not work.

1. I shoot 5-minute RAW sub-exposures at ISO 400 using Backyard Nikon or the camera's built-in intervalometer. I take as many dark frames as I can at similar temperatures and the same ISO. I take flat frames (at least 12) using an EL panel at ISO 200, with the same aperture for the lights if using a camera lens. ImagesPlus and DigiCamControl also can control the Nikon D810A. I believe you may need to purchase a special module with IP.

2. I focus with a Bahtinov mask, usually just using live view image on the back of the camera (super convenient!)

3. I usually capture flats with an EL panel but I used sky flats on my Andromeda image from 2016 and they worked pretty well.

4. I use Deep Sky Stacker for 'reduction.' E.g., DSS manages the application of the flats and darks to produce a calibrated image. DSS now supports D810A .NEF files natively, which I didn't realize until recently. I was needlessly converting the .NEFs to .dngs.

5. Image stacking is with DSS (for sequential images of the same target if I'm feeling lazy) or with Registar. Registar handles mosaics much better than DSS, and is generally awesome.

6. DSS is the only software I have found that can properly apply flat frames, at least with the way I'm doing things. Flats were better with the telescope at f5.4 than with faster and wider-angle camera lenses.

7. I then process in Photoshop as discussed later on this page.

What did not work for the D810A?

1. ImagesPlus does not do a good job with flat-fielding for me. DSS does a good job with exactly the same images. The IP support people took a look at this problem and their best suggestion was that my flat frames are not similar enough in luminance for IP.

2. This page has a discussion of the flat-fielding problems with IP.

3. In fairness to IP, I tried flat-fielding with Nebulosity also with poor results.

4. In 2016 I processed some of my Andromeda Galaxy frames with IP and it was OK. So there's still a bit of mystery here.

Do you have a workflow for the D810A that produces good results? Please post to the D810A Yahoo Group!

My Image Capture and Processing Workflow with the SBIG ST-8300 Monochrome Camera with the FW8-8300 Filter Wheel & Astrodon 5nm 36mm filters

• I shoot 5 minute images (sub-frames), and lots of dark frames (16-50) if possible. I also a shoot flat frames (8-32) with an EL panel, with each filter if time permits, but it looks like flat frames can be somewhat interchanged. The panel is shown on my 'other astro equipment' page. I make darks and flats on the same night as I shoot if clouds permit, but I avoid wasting time shooting darks and flats under clear skies.

• I focus with each filter when using the fast focal ratio FSQ-85 scope. My Astrodon 36mm filters are supposed to be parfocal to f/4, however: a) my FSQ-85 is f3.86, and b) I wasted many hours of images by not focusing with different RGB filters; proving they are not reliably parfocal on my equipment. Having said that, there is almost always a temperature shift after an hour or so, meaning you should refocus frequently in any case for best results.

• Focusing is accomplished manually with use of Bhatinov masks using the focus routines in MaximDL. The Bhatinov mask approach is simple, accurate, and highly recommended.

• I switched to Maxim DL for image focus/capture and image reduction (flats fielding, dark frame subtraction) on the SBIG. Previously I used CCDSoft. CCDSoft is not being regularly updated in my opinion, and I had to go to a beta/daily build version of the software to use my filter wheel. Maxim's business is largely Maxim DL and they are much better at staying current with equipment. Software Bisque is focusing on a new package integrated into 'The Sky.'

• I use Registar to stack each reduced FITS image of the same type object and framing. Where complex blending is needed, or when I'm going to turn a set of narrowband monochrome images into color, I align the different versions in Regisar, then use the Crop/Pad Image feature to make the images the same pixel dimensions.

• I then copy and paste the monochrome images into my RBG color channel of choice to create a rough color image.

• I will usually paste the H-Alpha image into the Luminosity channel in Lab mode, then then back that off to taste. I used the H-alpha version at about 50% in the red channel of my recent (2014) M8 & M20 area RGB H-alpha image here.

• It's Photoshop CS6 from there as described below.

'Natural Color' Technique from Narrowband Images (RGB optional)

Here's a detailed description of how I processed my Lagoon Nebula natural color image (located here).

1. First I get each image aligned and processed so it's reasonably 'bright.' I used Registar to align each image, and padded each image to exactly the same size so I can do the remaining work in Photoshop.

2. I blended the narrowband images using the formula below. (I paste the narrowband data into the desired color channel with Photoshop, then fade the previous result based on the blending formula.)

3. I worked on the image with curves so it had a neutral background and nicely showed some color.

4. I added the RGB filtered data using Photosohop same as before, (fading the true color data to roughly set it to be the proper contribution based on the exposure time and judgment).

5. Once again, work on the image with curves looking for a neutral background and nice colors.

6. Towards the end, to deal with low-level noise, I blended in a modified version of the bright and smooth Ha data for luminance (e.g., paste Ha, sent blend mode to luminance, then fade that to maybe 25-33%).

7. I kept interim versions of everything to deal with blown-out highlights that resulted from enhancing the dim areas so they could be easily seen. Towards the end I went back, modified interim images to nicely show the highlights, and blended just the highlights in with layer masks.

8. Finally, I selectively blended in an interim image that helped enhance the contrast of the dark areas.

For Reference: I start with something similar to below, but then freelance... An approximation of natural colors may be achieved by the following narrowband blending:
Red = H-alpha + Sulfur II (approx 75% / 25%)
Green = Oxygen III
Blue = Oxygen III + H-alpha (approx 85% / 15%)

Another formula found on a PixInsight page says:
Red = 0.5*S2 + 0.5*Ha
Green = 0.15*Ha + 0.85*O3
Blue = O3

This is a popular color combination as well; I will create both Hubble Palette and Natural Color images from narrowband sub-frames in most cases.

• Red - Sulfur

• Green = Hydrogen Alpha

• Blue = Oxygen

My Image Processing Workflow with the QHY8 'One Shot Color' Camera

I am using the recommended workflow in Nebulosity and then use Registar and Photoshop as outlined below:

• Capture in Raw (using 5 minute sub exposures) in Nebulosity

• As of late 2010 I need to fix Bad Columns and I'm using Sander Pool's fixfits utility. Update, 2011, by getting good bias and dark frames at very close to imaging temperatures my bad column issues are greatly reduced. In 2013 I am no longer using bias frames.

• I previously used Nebulosity's Bad Pixel Map feature, but due to the bad column issue I'm using darks more often in 2013. I had two cloudy nights on a fall 2013 trip and took 150 darks for the trip, where all the nights had similar temperatures. The results combining the darks with a 1.75 sigma combine appear to be quite good.

• Apply a Flat (which is done in the same step as using the dark)

• Demosaic each image

• Covert to Tiff format (I do this because Registar can't seem to handle the FITS files that Nebulosity puts out)

• Stack using Registar

• Process in Photoshop as noted below.

• When using a H-alpha filter, I use the channel mixer to turn the image to monochrome using only the red channel. (See more info on narrowband filtering with this camera at the bottom of my Narrowband Imaging page.)

• May, 2010: I sometimes use Deep Sky Stacker, Drizzle Image Processing, and AIP4Win's deconvolution filter to enhance the detail in dust lane areas.

DSLR Workflow

1. I still shoot (as of late 2012) astronomy images with a Digital Single Lens Reflex (D-SLR) camera, namely the Canon EOS 20Da. This camera has a modified design especially for astrophotography. I always shoot RAW format images.

2. I shoot 4 minute exposures at ISO 1600, now with a 15 second delay between exposures (instead of 45 seconds which I used before) to let the camera cool down a bit. Through 2007 I shot at ISO 800, but 1600 is best! Make sure your darks are at a matching ISO!

3. I am using ImagesPlus v. 2.82 to convert the Raw images from the 20Da, and for calibrating my images with a 'dark frame' and a 'flat frame.' I shoot darks while I'm changing targets, just getting them in here and there through the imaging session, and as I'm packing up. I then median combine the darks from the night and use them in my processing. I shoot flats during twilight, shooting about 16-20 and median combining them. (Update 11/2006, I am not currently using bias frames!) (Update 2013, I am gravitating towards a library of many darks from similar temperatures, rather than trying to get darks during the shooting night. I find that a very large # of combined darks works quite well. One thing to note is that the camera changes temperature as it starts shooting, seeming to stabilize after 30 minutes or so all else being equal. So, it's important to get darks capture during the same type of lengthy shooting scenario.)

4. In general, the dark frame is subtracted from each image frame, and the flat frame is calculated in to reduce vignetting. I'm using the IP workflow per the tutorial, but...

5. I often use Registar to combine images. Registar is easier to use than IP for images with different camera locations, and can handle radically different frames of the sky easily. Registar has a means to calibrate the levels of the combined frames that can work well for mosaics.

6. Then to Photoshop as noted below.

1. Photoshop rules for my final image processing.

2. I use Curves to manipulate the image.

3. I've started using the 'Standard Curve' in Photoshop as described in 'The New Astro Zone System for Astro Imaging' by Ron Wodaski and Russ Crowman. I saved one of these as an action I can run. After each run you need to set the black point in each color channel.

4. (Pre-2014) I have build an action that makes a series of small curve adjustments on the dark end of the image. The adjustments boost the low end but leave the stars end of things largely unchanged. I will run what amounts to around 10 small curve adjustments very rapidly to 'pull the image out of the muck' and get the image in a good, workable range.

5. NR: Aside from 'pulling the image out of the muck,' additional noise reduction techniques must be applied to most images image due to the extreme 'stretching' of typical astronomy images.

6. Noise reduction approaches: There several approaches/tools that can be used for noise reduction. Great results and ease of use are my top priorities. While some free tools may be available, I'm willing to pay for tools that meet my needs in this area. I use a couple of plug-ins. Neat Image is my favorite, and it is easiest to use when there is a fairly blank area of sky (no stars, galaxy, nebula, etc.) to select. I also use Grain Surgery in cases where I can't easily use Neat Image.

7. Aside: The best noise reduction in Photoshop alone (i.e., if you just using what comes with Photoshop) is based on strategic selection of areas to blur, with application the Gaussian blur. You can select a color range, or use the wand tool with a small # tolerance like 4. You can do this differently in each color channel.

8. Some images have issues with gradients, and I use and recommend the GradientXterminator plugin.

9. A few more (basic) details regarding what I do in Photoshop is at this link: Basic Image Processing in Photoshop.

10. Also, see the LAB curves technique I'm using, described below. This helps bring out the colors.

11. Star Shrinking: In 2012 or so I investing in Noel Carboni's 'Astronomy Tools' for Photoshop which was $22 very well-spent. Previously, in late 2008 I began to include star size management using a technique similar to the one on the top of this page.

12. The HDR toning feature in Photoshop CS5 & CS6 is useful for final color enhancements.

Noel Carboni`s Astronomy Tools And Supplies

Star Selection

1. There are many ways to select stars and Noel Carboni's tools have an action that works well. The trick is to properly expand & feather the selection.

2. Tight stars? Expand about 3-4 pixels and feather about 50% of that.

3. Bloated stars? Expand up to 7 pixels and again feather around 50% of the expansion.

Photoshop Tip: LAB Curves can help add color to flat images

Noel Carboni 60s Astronomy Tools Catalog

There are lots of ways to 'add color' to a flat DSLR astronomy image. A classic: apply an 'S' curve to the image. (Image->Adjustments->Curves, pull up the right/bright part of the curve, and pull down the left/dark part of the curve.) You can use Image->Adjust->Hue/Saturations, but purists shudder at this.

However, using this LAB technique has advantages as enumerated in Dan Margulis' books including 'Photoshop Lab Color' and 'Professional Photoshop.' It's pretty simple.

1. Convert Image into Lab. Alt-I-M-L gets you there (Image->Mode->Lab).

2. View the 'a' channel. Ctrl-2 gets you there. It will look very strange.

3. Here's a trick: Hit the ` key to the left of the # 1. This displays the image in color, but with a channel selected for any manipulations.

4. Bring up the curves function. Now, make the curve steeper, but keep the center point the same. The curve is a straight line. Do the same with the b Channel. See example below.

5. How far to go is a judgment call. If you'd like the subtly change the overall color balance, you can vary the line so it doesn't exactly cross the center point. Don't go too far with this!

6. Blur a/b channels? Other things you may wish to do in lab include blurring the a and b channels a bit, or maybe a lot, to help get rid of noise. This can help keep star colors under control (see caveats.)

7. Adjust the Luminosity channel. Be aware, thought, that pulling up the luminosity curve to better show the dim parts of your image will tend to flatten colors/reduce color saturation. (You can go back to step 4 again, if you want.)

8. Ctrl-' gets you back to all channels selected

9. Convert back to RGB. Alt-I-M-R gets you there.

10. Example: check my M31 page, including the images at the grid at the bottom of the page, showing where I started color-wise, and where I ended up.

11. Caveats: There are many, but the main caveat is that this best with images that are not already highly colorful. This technique also tends to exaggerate chromatic aberrations around stars, so this may need to be mitigated. (I should note that blurring the a/b channels in lab helps with this as described in step 6.)

12. Recent Update: The HDR toning feature in Photoshop CS5 & CS6 is a good alternative for adding color, especially for adding the finishing touches on a good image that could stand additional saturation.

Above: Adjusting the b channel by equal amounts. By making the curve steeper, you increase the visible differences between colors, increasing the color range of flat images.

Below Left: notice how flat this DSLR image seems; little color.

Below Right: Some color is starting to show after using the lab technique described here.

Current Astrophotography Capture Equipment
Advanced blending in Photoshop is discussed on my page here.

Copyright © by Dick Locke. All Rights Reserved. Last update: October 2013
Contact and Image Use Information
hits.

Noel Carboni`s Astronomy Tools And Equipment

As of 2012 I tend to use Noel Carboni's Photoshop actions to select and shrink stars.

For Reference: Wei-Ho's star subtraction technique

Old Astronomy Tools

Instead of (de)selecting stars, what I do is to subtract stars, enhance
everything else, and then add the stars back. Stars can be subtracted
using a high-pass filter. The basic steps are like this:
1. duplicate the image
2. high-pass filter the dup, with a radius about 4-10 times the size of
the faintest stars.
3. level the high-passed image. Change the lower input level from 0
to 128, and the higher output level from 255 to 128.
4. subtract this high-passed, leveled dup from the original.
5. enhance the star-subtracted nebula image
6. add back the high-passed, leveled dup.
There are several variations. For example, you can very easily
select the non-stellar components in the product of step 3, set
the background to black, then push the 'delete' key. This will
prevent nebula components being subtracted in step 4. You can
also do more than two times of star subtractions with increasing
radii in the high-pass filtering. This will get rid of stars more cleanly.

Astronomy Tools Fov

Color Processing DSLR & CCD Astrophoto Images- different than film? (Yes...)

Noel Carboni 60s Astronomy Tools Youtube

I've often thought that DSLR and CCD images seem relatively flat and monochromatic when compared with the film images from back in the old days This is true especially in the reds, where DSLRs generally have a relatively weak deep red channel. Popular astrophotography films have had a strong red response, including Kodak's PJ400, LE 400, and Supra 400 (all out of production), as well as Kodak E200 and Fuji's SHQ 200. A reason red is so important: Hydrogen Alpha nebulae glow at a wavelength of about 656 nanometers. Any sensor, be it film or a CCD/CMOS chip, that has poor response in this area will be omitting a critical component of the image of the sky where H Alpha is present. My previous DSLR, a Nikon D100, had a weak H-alpha response, along with relatively high noise. The Canon EOS 20Da was dramatic improvement in both these area. That camera had a modified design especially for astrophotography, but still shoots perfectly good daylight images without any special filters. (Good info on H alpha here.) In early 2008 I had my 20Da modified to further improve its H Alpha response.