Once upon a time the sky use to be clear

Why I Moan (A little bit of Science)

I’ve been moaning quite a lot about how few clear nights we’ve had this year, or at least nights where it’s been worth setting up the telescope and taking some snaps. So I thought I’d be scientific and work out exactly how this year compares to previous years (for me at least). I’m a bit of a data hoarder and I keep all my data (even the bad stuff) in date ordered directories so it wasn’t that hard to knock up a graph.

The yellow line is this year and the bars are the last three years of data. So, yellow line lower that bars is bad :-s

If you tot up the numbers for each year (I only used March to October since this is where I have data for all years) the past three years I’d expect somewhere between 40 to 50 nights on sky. This year I got 26 nights.

Now to be fair there were a few nights in April and May I probably missed due to moving house but I don’t remember 24 nights of clear skies I missed :-s

A Little Experiment

As previously stated I’m a bit of a pack-rat when it comes to saving my data. I have about 1.2TB of data and growing. Given that it’s been a bit cloudy recently (again as previously stated) I thought it would be interesting to go back a apply what I’ve learnt in terms of pixinsight processing on some old data.

So first up is this data that I took on Christmas Eve 2019 of the Horsehead Nebula.

Taken with my ES ED80 with a Hypercam 183C. No CLS and not guided. There’s quite a lot of light pollution in the raw data so I picked out the worst frames with a gradient before I stack it with Deep Sky Stacker. So there’s just over 1 hour’s worth of 120s exposures here.

All I can say about this is that it looks like what it’s suppose to. The light gradient in the bottom right hand corner makes me cringe. There’s also a load of noise and little detail.

So Time to Try again

So I re-stacked the data using Astro Pixel Procesor. I also included the data I’d discarded since APP is fairly good a smoothing things out. This gave me over 2 hours of light to play with (I also did a x2 drizzle but don’t know if this added much since I wasn’t guiding). I then used APP light pollution removal tool since I prefer it to the PI background extraction tools.

Then into PI and used MultiscaleLinearTransform for noise reduction. Stretched the data with HistogramTransform and removed the stars with StarNet. The back to MultiscaleLinearTransform to bring out some detail and finally HDRMultiscaleTransform to adjust the contrast. I did some touching up with clone tool at this point to get rid of a few bits and bobs. Then added back in the stars.

Since I don’t have a field flattener there’s some edge distortion on the stars getting towards the edge so I transferred to GIMP at this point and used the Lens Distortion filter to get rid of this and crop the data down.

Then back to PI to resample the data. Not completely sure if PI does a better job of this but thought I’d play safe. I figured that the resampling may have introduced some noise because of the quantization so I did try another MultiscaleLinearTransform for noise reduction again at this point but it didn’t seem to get a lot.

B33 – 24/12/2019

So I’m a lot happier with this. Will have to try some more and see what I can get out of them.

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