Astrophotography: Whirlpool Galaxy

I have several astrophotography posts on slowly getting the equipment to be able to take pictures of more than just the moon.  I had everything to attempt a photograph of  a Deep Space Object and my first try in 2014 was the Whirlpool Galaxy or Messier 51 by its formal name.   M51 is a spiral galaxy and besides being a beautiful galaxy it is really close to a second smaller galaxy called NGC 5195.  

Google Search info for M51

My setup for the photo was:

Telescope:  SV90T (90 mm refractor)
Mount  Celestron AVX

The basic premise of astrophotography of deep space objects (DSOs) is to take a bunch of exposures of the target and then you will stack them together.  The longer the exposure, then the stronger your signal.   I unfortunately was not yet ready to go guiding which helps keep your mount locked on the target for a longer exposure.  I will go over guiding in a future post. For now I had was just using the Celestron AVX mount to track the target.  We talked about the GEM mounts in a previous post and how they move with the Earth's rotation so you might think this should be enough to keep your target nice a centered.  The answer is it does a good job for awhile, but it is not quite good enough to hold the target perfect for the really long exposures.  For those you need a combination of the mount and a second telescope and camera to lock onto a star near the target and give the mount small corrections to stay perfect.  Since I did not have a guiding setup my mount is good for about 30-45 second expsoures before I start to see slight star trailing.

I got the mount calibrated and polar aligned (perfectly pointing to the North Star) so it will rotate with the sky correctly and then slewed to M51.  I took around 75 pictures at a 45 second exposure.  My final picture had about an hour of exposure.  The more total exposure you get, usually the better the picture detail you can capture.  this is a fairly easy target since you can pick up so detail of this galaxy in binoculars.   Therefore I could get a decent picture even with only an hour of light gathering.

Once you have the photos you need to stack them.  That process is another post and after you get one stacked image you need to process the image.  Processing is another topic I will eventually have several posts on.  Processing is its own science and you can spend hours on this step.  there are also many different software package options which are used in slightly different ways.  The very first attempt I made at processing the M51 photo I had is below in the first picture.

First processing attempt of M51

I was actually a little disappointed.   I wanted a colorful picture.  I was using a software package called Startools.   I talked to the owner of the software on the softwares forum site and he helped me come up with a much better image as shown below.  This just shows how important processing is.  Your stacked picture has all kinds of data including gradients, viginetting, color, etc.  Some of the data you don't even want in there like light gradients from light pollution and some you need to bring out like colors .  In my first picture you can even see a diagonal streak I had from some reflection I was getting.  The moon was out and I am gussing it was bouncing off something to cause my scope to pick up a reflection and put a defect in the image.

Processing with Startools Software

I tried the same picture with a second software call PixInsight and got a similar pciture

Processing with Pixinsight software

This post opens up a lot of questions:

How to Guide and get longer exposures

How to stack images (I did not even mention bias, flats, and dark photos)

How to process images

Hopefully these re things to talk about in future posts.  In the end I am still learning, but my first real picture of something other than the moon was breathtakingly beautiful and amazing to me.