Category Tutorials

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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Giving CCD Blooms the One-Two Punch with MaximDL and the NewAstro DeBloomer Plugin

When imaging with a CCD camera with a high quantum efficiency (QE), such as the SBIG ST-10XME with the KAF 3200ME chip, you sometimes have to deal with some very nasty blooms.  Due to the ST-10XME lack of antiblooming gate, light from bright stars overwhelm the full well capacity (electron holding capacity) of the pixels on which they are being collected, resulting in excess electrons spilling over into adjacent pixels.  In other words, the light-gathering pixel exceeds its capacity to hold captured photons which yields stars that have irregular diffraction spikes, as seen in the image below.

Blooming Example Pelican Nebula

Sometimes, the blooming can get so bad that you must take special care to preserve the stars and the detail.  During bloom removal, sometimes the excess electrons can spill over onto other stars and destroy them, ruining your star field.  I use MaximDL’s bloom removal tool but sometimes that tool removes more than just the blooms.  There is also an DeBloomer Plugin for MaximDL created by Ron Wodaski, which contains both automatic and manual tools that remove blooms.  The nice aspect of the DeBloomer plugin is that it performs a batch process on all your images.  I recently learned, while processing subs from M31, that the MaximDL bloom removal tool was not sufficient enough to preserve the stars when the blooms from an adjacent star spilled over onto it.  Here is an example:

Here is a two step process for dealing with these types of blooms while preserving adjacent stars using ...

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LED Flat Frame Astrophotography Light Box on the Cheap

LED Flat Frame Light Box

LED Flat Frame Light Box

Call it an impulse purchase but as I checking out at Walmart, I saw this small pack of Christmas Wreath lights as I was putting my items on the counter.  As I looked closer, I saw that it was a single string of 18 small LED lights.  It was only $3.99 and it came with its own power supply, requiring 3 AA batteries.  I thought to myself that this would make a very inexpensive way to power a flat frame astrophotography light frame box.  I had orginally specked out purchasing LED’s and buidling the powering mechanisms from scratch but this system was already complete and I did not even have to solder any of wires.  Having extra foam core from when I created my first light box using an Electroluminescent Panel, I broke out the Exacto Knife and began cutting panels.  As I cut my first panel, I envisioned how this LED light string could be used.  Here is how I created a Flat Frame box using this simple 18 LED string of lights.  Here is what I did:

1.  I cut a piece of foam core to the size I would need for my 90mm Refractor and then I used a hole punch to create a pass through where I could feed the wires and the LED lights through the back of the panel.  I left some slack and some extra cord hanging out of the back of the panel so that I could attach the power supply to the light box using Velcro.



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