M13 – The Great Globular Cluster in Hercules

Friday night finally brought clear skies to me, but it also brought a bright moon at around 82% luminosity. Because of this and also because I do not have any clear view points on any bright nebula, I decided to do something different. We are currently in what is called “Galaxy Season” in the Northern Hemisphere – a time when a lot of popular nebula are below our horizon or rising really late / early in the morning. For reference, I can now begin shooting the Cygnus regions around 2:30am. Since I had a bright moon and because of my current focal lengths (380mm / 480mm depending on my flattener) I decided to do something other then galaxies – globular clusters.

I had never shot a globular cluster before, and with my focal length coupled with the bright moon and my bortle 8 skies, it presented a challenge. I have been using the L-Pro filter by Optolong for my broadband targets, but I have had issues with achieving good focus consistently as well as light transmission. I am under a firm belief now that my best bet in shooting targets like this, and even galaxies, should be done with no filter at all.

I began the night shooting M3, a globular cluster in Canes Venatici, and then moved to M13 once it had risen above the tree line. On both targets I was able to get right at a hour and a half of integration time. My initial processing of M13 had me blowing out the core really bad so I went back and made some adjustments, mainly in how I did the curves in Photoshop. I posted the images on Instagram but I was still not totally happy with my result. I went back and started from scratch to get my current result. With my focal length, bright moon and light pollution, I am happy with the results.

60 x 90s
20 darks; 50 flats, dark flats and biases
400 ISO – Bortle 8 – Lunar Luminosity 82%

Meade Series 6000 80mm Triplet APO
Canon EOS Ra
Ho-Tech Field Flattener
No Filter


We were blessed to be able to go on a quick two week trip down south from New England to see some of my wife’s family and some of mine. Unfortunately, even though I brought my entire astrophotography rig down, I did not very many clear nights. The one good night I did get, I was not in a good place to setup my entire rig (could not see Polaris to polar align, a lot of trees, etc). However, I still was able to get out and do some experimenting by taking one second exposures with the Canon EOS Ra attached to the TPO 180 Ultrawide Astrophotography Lens. One of the targets I choose to hit up was Betelgeuse. Late last year I promised a friend that if I ever had a chance to set my camera to Betelgeuse i would and I hate to admit that I simply never took the time to do so, until now.

Above is Betelgeuse with some surrounding sky with no annotation, annotated and in negative. I really had a good time experimenting while getting this shot. This data was collected in Griffin, GA.

100 x 1s (1600 ISO)
50 x 1s (3200 ISO)
20 / 20 darks, flats, dark flats and biases
Bortle 6
TPO Ultrawide 180 Astrophotography Lens
Canon EOS Ra
Tripod with Orion Panhead

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