A collection of 100,000 stars, packed together 100 times more densely than the stars in our Sun’s stellar neighbourhood.
Askar 130PHQ: July 2023
After my epic 100-hour Pinwheel Galaxy project, I was keen for something a bit more manageable! M13 was well-positioned in the sky, and being a globular cluster its lack of faint nebulosity means it holds up well with shorter integration times. I collected about 11 hours, and then used PixInsight‘s SubframeSelector tool to whittle this down to the best eight.
Integration was fairly speedy, taking my PC just four hours and 20 minutes. The processing was fairly straight-forward too, especially compared to the tricky faint targets I usually go for. BlurXTerminator was useful, and I set it to increase the star halos to 0.4, making the individual stars glow, which I think is a nice effect.
Mid-to-long focal length telescopes with decent aperture are really useful for resolving the individual stars in globulars. Below is a comparison of a previous attempt I made at imaging M13 using my Askar FRA400, compared to this latest version made with my Askar 130PHQ. It’s not really a fair test, as the FRA400 is an extreme crop, and also I processed it before I had NoiseXTerminator and BlurXTerminator, but I still think it’s interesting to compare the two side-by-side. Note that the FRA400 has 16 hours of data compared to the 130PHQ’s eight, which I think makes the latest version all the more impressive.
Imaging details
* 22 June to 8 July 2023 to (2 weeks)
* Bristol, UK (Bortle 8)
* Telescope: Askar 130PHQ Flatfield Astrograph
* Camera: ZWO ASI 2600MC-PRO
* Mount: Sky-Watcher EQ6-R PRO
* Guide: William Optics 50mm Guidescope with 1.25″ RotoLock; ZWO ASI 120MM Mini
* Control: ASIAIR Plus
* Software: PixInsight, Lightroom
– PixInsight Pre-processing guide
* Filters:
– No filter 240 x 120 seconds (8 hours)
Total exposure time: 8 hours
By Lee Pullen
Processing walkthrough
I’ve made a PixInsight processing walkthrough for this image. Click here to see it.
Example source data
Askar FRA400: April 2022
Much like the Whirlpool Galaxy image that I took before this, the Hercules Globular Cluster (often simply called “M13”) is a tough target for me because it’s so small. My wide-field refractor telescope is much better suited to targets that appear larger in the sky. Still, beggars can’t be choosers, and Spring time doesn’t exactly offer many options!
All things considered though, I think this turned out ok. I quite like seeing the globular cluster itself with a bit of “empty” space around it, helping to frame the target and provide some context too. Oh, and the stars are well resolved considering my telescope only has an aperture of 72mm.
Post-processing was fairly simple and mostly in PixInsight. I used an excellent plug-in called Generalised Hyperbloic Stretch (GHS) for stretching, and it worked brilliantly. A bit better than EZ Stretch I’d say, as GHS does a particularly good job of keeping stars well controlled, which was really needed with this target. I boosted the saturation a bit in Lightroom, where I also gave a light dusting of noise reduction. No Topaz DeNoise AI this time; I tried it, but the results just smothered all the details.
It’s almost exactly a year since I imaged my previous globular cluster, M3. I think that this new picture is appreciably better, mostly as a result of me getting better at image processing.
Imaging details
* March to April 2022
* Bristol, UK (Bortle 8)
* Telescope: Askar FRA400 f/5.6 Quintuplet APO Astrograph
* Camera: ZWO ASI 2600MC-PRO
* Filter: none
* Mount: Orion Sirius EQ-G
* Guide: William Optics 32mm; ZWO ASI 120MM Mini
* Control: ASIAIR Plus, ZWO EAF
* Software: PixInsight, Lightroom
* 480 x 120 seconds
Total integration time: 16 hours
By Lee Pullen
Example source data
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