Category Lessons Learned

Off Axis Guiding with the Hutech OAG5

Hutech OAG5 - 2

Since the first light of my Celestron C9.25 telescope, it became apparent that I would have to take the plunge and learn how to guide using an Off Axis Guider (OAG).  I also do most of my imagine in Narrowband so I needed an OAG so that I could guide in front of my filters.  My mentor, Michael Caligiuri, told me that learning how to guide with an Off Axis Guider was a must with a larger focal length telescope but would not be easy so I set out on a quest to learn how to use this critical piece of equipment.

Step 1: Sourcing an OAG

There are many OAG’s out on the market and depending on your needs, there are a few that would be right for you.  Selecting the right OAG depends on how much distance your focal train can take.  With the OAG 5, the light path was 36mm, which is a fair amount of distance to take up in a focal train but I did some research and found that this OAG was used quite a bit with my camera combination (the SBIG ST-10XME).  Knowing which OAG I needed, I starting searching Astromart daily to see if anyone was getting rid of theirs and it did not take too long before I found one at a killer price.

Step 2: Putting the pieces together 

Admittedly, this step took much longer than I anticipated.  Since the CCD and the OAG are connected to the same light path, the most important aspect to figure out is that the imaging chip and the guider chip need to be the same distance from the pick off mirror that sits inside the OAG...

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The Evolution of the Andromeda Galaxy

Evolution of Andomeda

While the Andromeda Galaxy (M31) has been evolving for the last 9 Billion years, my tenure as an Astrophotographer has only been evolving for the last 1.5 years.  I got the Astrophotography bug when I first snapped a photo of the Moon back on April 7, 2012.  Fast forward to August 2012 where I took my first deep sky image of the Andromeda Galaxy with my Nikon D7000 DSLR through a Takahahshi Sky90 telescope.  I remember being blown away by being able to “see” light from galaxies millions of light years away.  Ever since then, I possessed the desire to learn everything I can about astro imaging.  After shooting deep sky objects (DSO’s) with a digital camera for a few months, I wanted to learn how to shoot with a CCD (Charge-Couple Device), which is a specialized camera for Astrophotography.  I purchased a used SBIG ST-2000XM CCD with a 5 position filter wheel that had Luminance, Red, Green, Blue, and a Hydrogen Alpha filter in it so I could teach myself techniques to get even more detail out of the DSO’s I was shooting.  After I got over a steep learning curve, I was able to work on one very important principle, which was quality over quantity.  With Astrophotography, you need to invest a great deal of time taking multiple exposures to bring out the detail in the amazing objects that are out in space.  This principle is evident in the 4 images of the Andromeda Galaxy that span 1.25 years of learning how to image objects I can’t see with my own eyes...

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Using AstroTortilla to Plate Solve Objects


I recently downloaded a plate solving program called AstroTortilla, which is a program that corrects GoTo alignment and centers objects you are trying to shoot.  Before using this program, my GoTo alignment would vary from night to night and if I am shooting the same object, I would have to crop out a portion of the object since the mount did not slew exactly to the position I had the night before.  After I successfully installed and set up the program, thanks to this amazing tutorial, I tried it out on the Pelican Nebula (IC 5070).  After plate solving the nebula, it was a clear night so I decided to image for a couple hours until the clouds rolled in.  Under the full moon, I can only image through the Hydrogen Alpha (Ha) filter so I went out the next night and collected more data on the Pelican Nebula.  The AstroTortilla program performed flawlessly each night.  As you can see in the image below, the only cropping will have to do to this image is due to drift, which is an insignificant amount of image loss.

The black border around the image represents the amount of cropping that is needed due to drift

The black border on the right of the image represents the amount of cropping needed due to drift

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Narrowband Imaging, Processing Tools and Techniques

ElephantTRunkNebulaSliderSince getting an SBIG ST-10XME and a CFW10 with Narrowband (Ha, SII, and OIII) filters, I could not wait to image an emission nebula.  I received the new goodies on August 9th, and of course, the conditions were not right to image until August 20th.  I had first light with the ST-10XME under a bright full moon so I could only shoot through Hydrogen Alpha filter.  Ten days later on August 30th, I was able to shoot with all 3 filters so I chose the Elephant’s Trunk Nebula (IC 1396) as my target.

Narrowband Imaging

Learning how to image through Narrowband filters was not as difficult as I imagined.  Here are some things I learned along the way:

  • Since these types of filters only let in certain wavelengths of light, one of the main differences was the exposure time.  I typically take 5 minute subs but I had to increase the time to 10 minutes to get a decent looking sub with lots of detail.  Your experience may vary and will depend on the focal length of your telescope and imaging equipment
  • I still focus my telescope manually so focusing follows the same routine of looking at the stars Full Half Width Maximum (FHWM) to see if you are in focus.  I focus with the Ha filter in a 3×3 bin, with a 1 second continuous exposure
  • I have collected data a couple of different ways.  When the moon is in the sky, I will collect Ha data.  If the Moon is not present, I will collect all 3 types of data (Ha, SII, and OIII)
  • With Narrowband imaging, it is all about data data data...
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M51 Processing Comparison using MaximDL, Photoshop CS6, and Noel Carboni’s Astronomy Tools

M51 Whirlpool GalaxyWhile on vacation, I guess I have nothing better to do at night as I am without my imaging gear so I decided to reprocess some of my older images for fun. To my surprise and delight, one of images came out much better than I had originally processed the first time around. Then, I remembered that the first time I processed M51, I tested out color combining and stacking just using Photoshop. This time, I color combined the image and aligned it using MaximDL and then further refined it using Noel Carboni’s Atronomy Tools actions for Photoshop.

When I took the RGB images, there were a few things that I was not doing.  First, I did not discover that I could cool the camera, which introduced the a lot of noise to the images.  The color subs only had 3, 5 minute exposures each, which is not very much.  I had also had not calibrated these images using flat frames so I had a few things working against me as went to process this image.

As I set out to reprocess this image, I first opened up the RGB TIFF image and ran the HLVG (Hasta Lavista Green) filter, which removed a nasty green hue to the image.  Then, I ran the image through some of Noel Carboni’s Astronomy Tools and used the following:

1.  Deep Space Noise Reduction

2.  Increase Star Color x 2

3.  Soft Color Gradient Removal (the image had a rainbow cast to it before

4.  Color Blotch Reduction (I had blue and red pixels all over the image)

Given that I had many things working against me to process anything out of my M51 ...

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Sometimes Taking a Fresh Set of Dark Frames is Needed

Taking astro photos is a very noisy business so one technique to reduce the noise in your images is to take Dark Frames.  There are countless websites and blogs detailing the need and how to take dark frames but I am just going to focus on a visual example using the Eastern Veil Nebula (NGC 6992). I recently took 2 hours worth of data across 24 sub exposures in Hydrogen Alpha and I was so excited to begin processing it.  I was confused when my image, calibrated with Dark Frames and Flat Frames, came out very noisy!  I then began reprocessing to figure out what was going on.  It took me a while but then it hit me.  I was using an old master set of dark frames that I had only taken 15 dark frames with.  I then took a fresh set of 24 Dark Frames and that solved the issue, as you can see in the example below:

The image on the left was calibrated using 24 Dark Frames.  The image on the right was calibrated using only 15 Dark Frames

The image on the left calibrated with 24 Dark Frames. The image on the right calibrated with only 15 Dark Frames. The results are markedly different.

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M13: What a Difference 10 Months Makes

About 10 months ago, I started getting into Astrophotography, which has been an amazing and positive experience for me so far.  I started taking photos of Deep Sky Objects (DSO’s) with my Nikon D7000 DSLR and I was quickly enthralled with the beauty of what existed out in deep space.  One of the first DSO I imaged with my DSLR was M13, the Great Globlar Cluster in Hercules.  I remember being in awe that the pitch black patch of sky I pointed my telescopic contained so much beauty.  After learning how to do some rudimentary unguided imaging with my DSLR, I wanted to see if I could get more detailed photos so I looked into purchasing a CCD camera, which is a specialized imaging system for Astrophotography.  I received a ton of helpful advice from Michael Caligiuri who has been a tremendous source of inspiration and knowledge.  I also did some research and subsequently purchased a monochrome SBIG ST-2000XM and a filter wheel from Astromart so I could now image DSO’s across the Luminance, Red, Green, and Blue channels.  Flash forward to present day and here is a comparison of M13 taken 10 months and one I recently took back on June 4th:

M13 2012 and 2013 Comparison

M13 2012 and 2013 Comparison

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Flat Frame Calibration Astrophotography Example with M13

Flat Frame Calibration

Flat Frame Calibration

A couple weeks ago I built a flat frame light box for my telescope so I can take these really important images so that imperfection (dust, etc.) in my telescope and CCD camera are subtracted from the frame.  At the most basic level, flat frames are used to correct the vignetting and uneven field illumination created by dust and imperfections in the optical train.  In the example above, the photo on the left is not flat frame calibrated and you can see dark circles in many places on the image.  These imperfections are dust motes.  The photo on the right has been calibrated with flat frames, serving two very important purposes:

1.  Removing dust motes

2.  Evening out the field around the corners of the image

Here is the final LRGB image of M13 that is both dark and flat frame calibrated:

M13 Globular Cluster in Hercules

M13 Globular Cluster in Hercules

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Astrophotography Flat Frame Light Box using Electroluminescent Panel

Flat Frame Light Box Made from Electroluminescent Panel

Flat Frame Light Box Made from Electroluminescent Panel

Before I start, I wanted to say that almost 100 flat frames were sacrificed in the making of this light box.  Last weekend, I built myself a Flat Frame Light Box using 5mm Foam Core and an A5 Electroluminescent (EL) Panel.  I image with a Takahashi Sky 90II and an SBIG ST-2000XM and there are dust particles on the telescope as well as the CCD.  I am not going to describe the need for flat frames or how to take them as it is covered in many other articles around the web.  This blog aptly called DasFlatFrame does a good job at describing the need for flats.  I am going to describe how I constructed the light box

Materials Used:

  • A5 Electroluminescent Panel
  • 12 volt inverter (if you want a dimmer panel you can use a 9 volt inverter)
  • 5mm White Foam Core
  • White Printer Paper
  • Vellum Paper
  • White Duct Tape
  • Scotch Tape
  • Cardboard (used to hold the box on the telescope)


  • Protractor
  • Ruler
  • Exacto Knife

Light Box Construction

Figure out your measurements based on the size of your telescope.  This light box was made for a Takahashi Sky 90 so I figured a 10 in. x 10 in. x 10 in. box would suffice.  For the outside of the light box, I cut 6, 10 in. x 10 in. x 10 in. Foam Core panels.  I cut an additional 10 in. x 10 in. x 10 in. panel for the Diffuser Panel.  The Diffuser Panel and the Rear Panel of the box have rectangular cut outs so that paper and the EL Panel can be affixed on to them...

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Imaging Processing Fun with M51 Whirlpool Galaxy


What happens when you spend 3 hours imaging an object only to find that you have only a handful of salvageable images from the session?  That happened to me back on May 3rd when I imaged the Whirlpool Galaxy.  During the night, at some point, I lost guiding and did not catch it so when I went to process the photos I was surprised to see that 2/3 of them were unusable.  Having only 13 images to work with, I processed the images 4 times over to see if I could get a decent image to come out.  Along the way, I learned a ton (as usual).  Here are some of the things I tried and the outcome of each method:

1.  RGB Misaligned – MaximDL RGB Color Combine (Average Method) + LRGB Combining in Photoshop CS6

M51 RGB Misaligned

M51 RGB Misaligned

The image above is a result of the RGB images being misaligned when processing.  Sometimes I get a little impatient and don’t take my time getting everything perfect during the post processing aspect of Astrophotography and this can result in very sloppy images.  When the RGB channels don’t line up, you get a mess of colors scattered throughout the image.  The RGB and the L images were first combined (using the Average method) in MaximDL and then combined in Photoshop CS6.  As you can see, even Photoshop can’t save this image.

2.  LRGB Combination in Photoshop CS6

M51 LRGB Combination in Photoshop CS6

M51 LRGB Combination in Photoshop CS6

The photo above represents an image that was combine using Photoshop CS6...

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