Astrophotography – deep sky

M27

Just thought I’d put this in before I loose M27 behind the wall!

This is a big crop of the image because I am only using 2 sets of data, Ha and L. The L was taken in September and the Ha last week. Between the two sets,

Lee has realigned the two scopes so there is a 45 degree rotation between them. Hope to get out tonight to get RGB and maybe some new L.

There is 1hr 25mins of L and 45mins Ha. To get the colour I’ve used the Ha as red and the L as both G and B. Seems to have worked reasonably well.

Geoff

Using Starnet++

I’d read a few bits and pieces online about Starnet++ – a software module that uses a neural network to identify and remove stars from astronomical images in order to enhance nebulosity and process it separately to stars.
The software is free and you can find it at the link below. It was originally published as a Pixinsight module, but can now be downloaded and run standalone on Windows: https://sourceforge.net/projects/starnet/

I’ve found it’s pretty good- I’ve been playing with it today on an image of the Western Veil I took a few weeks back. This is my original processing of the image:

To use the technique I started again with the stacked file and used Pixinsight to remove the background light pollution gradients, calibrate the colours and do an initial stretch. I then put the image through the Starnet routine and it returned me the image below:

I then used the Clone Stamp tool to clean it all up (possibly more time needed on this!) and tweaked the curves to give it some contrast and got this:

I really like this, but I felt it would be better with some stars blended back in, so I went back to the image I submitted and processed purely to get the brightest stars at a prominence that I liked. I then blended the two images using Pixelmath (in the way I used it here, it’s identical to blending layers in Photoshop or GIMP with lighten):

Pleiades & Eastern Veil Nebula 8/11/2019 Lichfield

With a bright Moon, photography was limited last night – cloud over some of sky limited choices of target. However, having just demonstrated that Polemaster works on my scope, I opted to have a go at taking a photo of these two objects.

QHY10, Sky Watcher Equinox Pro 80mm, EQ6.

Sky very bright and Eastern Veil was difficult to observe with the 30 x 60 sec subs I took last night ==> I have needed to rather over-process the image below to demonstrate the nebula.

Andy

Pleiades:

Eastern Veil Nebula:

SH2-222

Took this last night after Lee had adjusted the alignment of the two scopes last week, so that they actually look at the same thing!

Forecast last night was for a clearance at 2200hrs. So at 2015 I looked outside to see clear skies. Rushed out and set up. After 2 restarts and guiding aligned 3 times I was ready to start at 2200hrs. Guess what? Total cloud cover! So I decided to wait a while and 40 minutes later the skies cleared. However my target was to have been the dumbbell but it was now dropping in the West below the obsy wall. After a quick search on SkyMap Pro I found this at a nice angle with 1hr 50mins to the Meridian. Also noticed that it is small at 6 minutes so just right for the new scope FOV at 16×22 minutes. This is taken in Ha with 19x 4minute subs. There seems to be a bit of a controversy about whether the object is an Ha one or if it is a reflection one that is shining through the dust layers. Anyway, this is the full FOV image with the 6inch RC.

Geoff

 

Forgot to mention this object is called “The Northern Trifid” because it resembles the famous trifid nebula in the celestial south

 

 

My First Mosaic – and how I did it.

Inspired by Geoff’s results I tried using the automerge in photoshop on my pictures of the Heart and Soul Nebulas. Oddly it only matched them if I selected the Soul first! Unfortunately it doesn’t rotate the images and my two sessions were at quite different angles for some reason.

I have combined images in photoshop before, but only on top of each other, never as a mosaic, but i decided to follow a similar path:

First I doubled the canvas size for the Soul image an imported the Heart as a layer on top.

I set opacity (opposite of transparency) of the heart image to 50%, and guided by stellarium to find the rough alignment it was easy to find a small asterism on both images. Zoomed in, I overlapped one of the stars in the asterism as accurately as I could. Circles of smeared stars around this point gave an idea of how much rotation would be needed.

using the select tool I then moved the centre marker of the Heart image over the centre of the aligned star and went to the edit menu to select ‘free transform’. This opens boxes where you can alter things like horizontal and vertical size and skew the image – not needed for images at the same scale. Instead I just used the ‘rotate’ box – this lest you enter angles in increments of +/- 0.05 degrees. This may sound a quite big step, but actually I’ve found it is small enough to align stars across a whole image. It’s easiest to step in whole degrees, then tenths of a degree and finish by using 0.05 degree to get the best possible result. It’s very obvious when you are aligned as the overlapping area suddenly looks much sharper.

I then changed to the magnifying glass tool – this brings up a box asking you if you want to apply the transformation – click yes if you are happy!

I then restored the Heart image to 100% opacity. It was clear it was less contrasty and a bit paler background. I used the ‘levels’ dialogue to alter gamma and black point until it looked a closer match to the Soul – you could also do this with curves. the whole thing might have been better if I had originally process the two images the same way.

Once they matched there was still an area of overlap with poor quality in the corner of the Heart image. I used the lasso tool with a feathered edge to remove most of this corner. A small patch still appeared too pale, so I lassoed it and changed its levels to match better.

This is the result, not perfect but not bad either:

Heart and Soul
Heart and Soul Nebulas

Soul and Elephant’s Trunk with L-Enhance filter

Got both of these last night. The L-enhance gives more stars than a Ha filter, but seems to require a lot less stretching to get results. Not a lot of SII/Hb in these, especially the soul.

I think these might work well as luminance layers over an RGB image. Looking forwards to using them on the Rosette and M45.

Elephant Trunk Nebula
Elephant Trunk Nebula with L-Enhance filter

 

Soul Nebula
Soul Nebula with L-Enhance Nebula

 

My first (worth shouting about!) astrophotograph – Pleiades

So, a year since starting this hobby I can finally show something that I’m happy to post.   Hopefully it’s recognisable!

It’s a bit basic for all you battle-hardened astrophotographers, but it’s my baby, and I’m a proud father 😀
(Disclaimer: It’s only a 3.5Mb export from GIMP, so the quality here isn’t optimum; I tried uploading a slightly larger file, but got errors)

Whilst building up my kit I’ve aimed for a light(ish), portable, standalone setup, so I’ve gone through the educational tribulations of setting up and getting to grips with StellarMate on a Raspberry Pi simply because it appeared to be a one-stop-shop rather than a pick-and-mix of various applications and tools.  And us geeks like to tinker 🙂

In the past I’ve had problems with using its Polar Alignment tool, but it transpires that muddling by with the wrong cable, thereby under-amping the Pi, meant that for the price of a nail the battle was lost.  A 2 quid Amazon Basics cable meant that last night was my most successful ever.  The Polar Alignment tool worked a treat, and it was only at breakdown did I realise that the I’d left the Dec clutch locked all through the session, so the fact that I’ve not got any (overly noticable) star-trailing can only be down to the polar alignment (someone please correct me if I’m wrong).

Onwards and upwards.  Orion Nebula and Andromeda are – clouds notwithstanding – in my sights!

81 Lights & 15 Darks – 30secs @ 1600iso
Unguided
DeepSkyStacker & GIMP

Skywatcher 80ED+Red/Corr
Canon 450D – Modded (IR)
Skywatcher EQ3-2
Raspberry Pi 4b running StellarMate 1.4.4 (beta)