M36 with Marginal Collimation, a Misbehaving Mount, and Poor Seeing

Image January 6, 2022

And if that title wasn’t enough to pull you in…

The seeing in Brooklyn is always bad. I’m on a flight path to LaGuardian. So 3-arcsec is typical. And did I mention I’m in Brooklyn, NY? So the light pollution is always bad. Which make star clusters reasonable targets.

ObjectM36, Open Cluster
CameraASI1600MM-Pro, LRGB
Lens/ScopeAstroTech RC6
Exposure121 x 15 sec Red
135 x 15 sec Blue
130 x 15 sec Green
270 x 5 sec Luminance
LocationBay Ridge, Brooklyn, NY
ProcessingPixInsight: more steps than I care to remember
For more information include labels, see https://www.astrobin.com/h2j53k/

I was still trying to get the collimation right for my AstroTech RC6 after having dropped it the previous year. I’m pretty sure that mechanically, it was never really aligned well, but at least at the time this image was taken, I had improved things enough that I was again getting diffraction spikes. I think I did another round of collimation after this was done and have managed to get the image better balanced in the corners, but that’s for a future image.

This was sitting on my (since sold) Celestron CGX-L mount which was not playing nice that night. For some reason, it would occasionally decide to stop tracking. It might have been the laptop trying to conserve heat :-). Since I’ve sold the mount since them, I’m not going to find out. In any event, that meant that I had to toss a few hundred frames. These are all 5-15 second frame, depending on the filter. Throw in a bit of wind, a few planes passing through the field, and even with the frames that were tracking, I lost about 30-40% after using PixInsight’s subframe-selector to toss out those with low star counts, excessive FWHM, or low eccentricity. To the extent I can automatic this, I don’t care too much.

Exposures probably should have been higher for the color data, and even the luminosity data has a pretty noisy background. I was trying to avoid saturating on the brightest stars, but maybe I need to reconsider that.

I used an LRGB combination, following some tips from Adam Block studios (I recently subscribed to his site and tutorials and am currently suffering from brain overload having watched hours and hours of guides). That let me rescue some fairly poor quality data into a mediocre image. Oh well, it’s the time of year that I can go try this again soon.

Local Weather