I had borrowed my friend’s William Optics Megrez 72mm Apochromatic refractor for astrophotography, although not had a chance to use it. This telescope is paired with the Astrotrac TT-320-TX AG to correct for the earth’s rotation while imaging. This setup is mounted on my Manfrotto 075 tripod. This 72mm F6 telescope has a focal length of 430mm (or 860mm effective focal length on the Micro 4/3rds system). As I had used the Skywatcher ED80 for solar and moon imaging, I decided to see if there was any benefit from using this apochromatic refractor.
For solar imaging, I normally use the Baader solar film 5.0 and the Baader Solar continuum filter to improve details of sunspots. The first shot below however was shot (accidentally) using the Astronomik CLS-CCD filter, which is used for astrophotography at night to reduce skyglow from surrounding street lights; I simply took the wrong filter by mistake. I’ve included this image as well, to show that with apochromatic refractors you do not necessarily require the Baader Solar continuum filter to get good detail of the sun spots.
These images were taken on 7/9/14 Sunday, the day before mid-autumn festival (full moon), and you can see a tiny sliver of darkness along the left edge of the moon. I shot the moon using only the refractor, and then paired with a Celestron 2x Barlow, to see the effect of magnifying the moon by 2x; the moon barely fit into the image sensor at (860×2 =) 1720mm effective focal length.
The William Optics performs well for both solar and moon imaging, with good capture of detail despite having a shorter focal length than the Skywatcher ED80. It however does not let much UV through unlike the Skywatcher, and hence would not be as suitable for UV-imaging of stars and planets – the image of the moon shot with the Baader U filter was not very clear at all, which is why it has not been included in this post.
I would like to state that these were all single images taken and post-processed. I would expect that stacking images would improve the details captured, but this is an area I will need to look into. I would also expect that using the Baader Herschel prism would further enhance the images captured, but that will require a significant investment (perhaps something for the future).
From the images I have taken on different days, you can see that the sunspots visible are different every day. Hence it is like a new adventure each day, as you do not know what to expect when you look into that telescope.