Astroimaging Lesson 1 - Setup and Autoguiding

This blog has a twofold purpose.  It is to showcase to the public the many wonderful things that can be seen in the sky no matter your experience level.  The other purpose is to act as a journal/notebook of things that I have learned so I can review them at a later time.

This post is to log the information I received last night that I can use to refer to for next time.

I had the great fortune of having a very experienced astroimager come over to help me with my equipment and teach me autoguiding.

Imaging

Autoguiding is basically a process whereby you attach a secondary telescope (guide scope) to the primary telescope.  A small camera is placed in the secondary telescope and hooked up to a computer.  A computer program looks at the stars in that view and locks onto one.  If there are tracking errors associated with the mount due to wind, heavy traffic, people walking it will compensate by ensuring that star stays within a very small pixel range.  This allows the astroimager to take a long exposure photograph through the primary telescope without having to worry about star trails created by mount tracking errors.

In the past I did not use an autoguider and I noticed most of my exposures longer than one minute had star trails.

Mount Setup Procedure

The evening started out with lessons while the Sun was still up.  I hauled out my large tripod and mount to a grassy region in my backyard.  The three key things to ensure are absolutely correct are:

1. Level the mount.  This can be done my looking at the level bubbles on the tripod to ensure the bubbles are in the middle of the circle.  If they are not, adjust the position and height of the legs to ensure this is correct.
2. Balance the telescope.   When the telescope and imaging equipment has been installed on the mount it must be balanced in declination and right ascension.  This can be done by opening the declination clutch and see if the telescope is stable (not moving) at different positions.  This process is repeated for right ascension.  If the balance needs to be adjusted in declination, the telescope needs to move forward or backward on the mount.  However, if the balance needs to be adjusted in right ascension, the counterweight needs to be moved up or down the bar.
3. Accurate Polar Alignment.  This is critical to ensure there is no star rotation with the images taken.  Autoguiding can only take you so far.  The polar axis of the mount should be pointed as close to North (Polaris) as possible.  The next thing to do is to use the polar scope and line up the constellations shown on it as good as possible.  The final step is to place Polaris in the bubble indicated through the polar scope by course and fine adjustments of the mount.  There are other more advanced techniques to polar align that I have yet to learn.

Imaging Equipment Setup

The telescope was installed correctly on the mount and then required several items of imaging equipment.

1. Autoguiding Scope.  I was using my 540mm refractor so I opted to use the 50mm guidescope.  It was piggybacked on top of the primary scope using a simple bracket.
2. Autoguider.  I used the Orion StarShoot AutoGuider and installed it into the back of the 50mm guidescope with the words facing upwards to ensure a consistent chip position from night to night.  I plugged it into the computer via a USB cable and also plugged the guider into the guide port on the mount.
3. Camera.  I used a Canon 6D camera and used a T-Ring to install it onto the back of the telescope.  When I tested the focus on Venus I noticed I needed more space in the imaging train so I added a 1" spacer and ensured it focused approximately in the middle of the extent of the focuser.  I used the maximum zoom on the live view of the camera and the fine focus knob to ensure the focus was as perfect as possible.  I plugged a automatic shutter release cable into the port of the camera.  In the future I will use a USB connection and take my images using BackyardEOS on my computer.

Basic Alignment

When it has become sufficiently dark the stars will start to come out.  The mount should be turned on and the hand control panel will ask several questions regarding the date and time.  I use an app to ensure the time is accurate as possible.

The hand control will then ask which type of alignment that would like to be done.  I choose two-star alignment.  It will then indicate to put the telescope to the 'starting position' aligned with the arrows on the mount.  After that is done a star will need to be chosen from the panel.  You will need to know your stars and their basic location.  When you choose a star from the hand control the telescope will slew to that region of the sky.  The next step is to use the live view on the camera to ensure the star is in the middle of the view.  There is a course adjustment and a fine adjustment to get the star to the center of the view (use a high zoom on the live view).  When the telescope is aligned to this star it will ask for another.  It is good to get stars at different parts of the sky but typically not overhead.  After the two star alignment you may add additional calibration stars until the telescope slews to the stars without much adjustment.

Autoguiding

I used the program PHD Guiding 2.0 to do all of the autoguiding throughout the evening.

I opened the program and clicked on the 'Connect to Equipment' button located in the bottom left.  It asked me which type of autoguiding camera I was using and fortunately mine was in the system so all the information could be imported without any advanced adjustment which I did not have to learn yet.

Connect to Equipment Button

While it was still light out I created a dark library to ensure I would hopefully not guide on a hot pixel from the autoguider.  To do this I clicked on the 'Darks' menu on the toolbar at the top and navigated to 'Dark Library'.  I ensured the lens cap was on the guidescope and then created a library of dark images.  This process took no more than a few minutes.

When it got dark I slewed the telescope to a known object in the sky I wanted to image.  When the telescope had stopped moving I clicked on the 'Begin Looping' button that sat next to the 'Connect to Equipment' Button.

Begin Looping Button

When I clicked on this button an image of the stars in the region the guide scope was pointed to appeared.  I had to adjust the distance the autoguiding camera was in the guidescope to focus the stars as cleanly as possible.  This was finicky but it was done within a couple minutes.

I used the 'Tools' menu on the toolbar and navigated to 'Auto-select Star'.  The program selected a star that it would use to autoguide.  The program had been run a calibration and it spent about 5 minutes calibrating the setup.  This typically has to be done once per evening unless you are moving the equipment around the yard which is not recommended.

After the calibration was complete I was ready to autoguide!  I clicked on the 'Begin Guiding' button located at the bottom of the window and it began to work.

Begin Guiding

I noticed in the Star Profile sub-window a plot of the target star.  The plot should look quite spiky without a flat top to ensure proper guiding.  The History sub-window showed a graph of the right ascension and declination corrections.  It seemed to be tracking very well with only minor corrections required.

After I had finished photographing the area found within the field of view of the primary telescope I stopped the autoguiding.  I then moved to a new target and auto-selected a new star and began guiding again.

Basic Imaging

I set my DSLR camera to bulb and used a remote shutter as to minimize the vibrations to the mount.  I took several images at a 30 second exposure and several at a 2 minute exposure.  I hope to learn how to process these images some time in the near future.

Using the remote shutter became a hassle as I had to keep monitoring it to close the shutter.  There is an intervalometer setting on it but I wanted to spend more time imaging than fiddling with a remote.  The program BackyardEOS will allow me to control the camera from my laptop thus removing the necessity of learning the intervalometer.

Takedown

Taking down the equipment is always difficult.  It is usually late at night and you are usually cold.  There are many wires and pieces of equipment that need to be placed in the right spot so you can find them the next evening.  I still have to organize the stuff I dumped on the couch last night!  I hope to have a good takedown system for when I image in the future.

Going Forward

I hope to try setting up again this week to practice the many things that I learned.  I also am looking forward to using the new camera control software to ease some of the astroimaging burden.

Now that I have data (photons collected from space onto the camera chip) I need to learn how to process it using a post-processing program such as Photoshop.  I look forward to the opportunity to learn from some experts who are colleagues in the Royal Astronomical Society.

Perhaps in the further future (Fall 2018?) I would certainly like to try this setup with my 2800mm focal length C11 telescope.  I was taught that it is not as forgiving compared to using the wide field 540mm focal length refractor.

I am very grateful for all the help I received from very kind members of RASC and for the equipment I purchased from All-Star Telescope which is linked below.  If you ever are interested in getting into astronomy give them a call today and avoid the department store products.

https://www.all-startelescope.com/