Where Eagles Dare...

[Paul81]

Second clear night running so time for another observing session. Over the last two nights I have decided to get into the habit of typing out some notes as I observe so most of what is in this (and yesterdays) post is those notes.

For this session I attached the Astronomik UHC filter to the focal reducer. The reducer itself is actually a 1.25" filter, so the UHC just screws on to it. All observations were made using 30s exposures and I had collected 10 darks before starting. Scope was the AA6RC @ F4.5.

First target was M16 The Eagle Nebula. This was quite low, and was only just clear the wall of one of the neighbours houses at the start. I used median stacking for a total of 10 minutes (all frames stacked). The longer the object was observed the more intricate detail appeared in the fainter wisps of nebulosity. It was like cracks were appearing and getting deeper. The central pillars remained quite prominent from the start of observing but become less noisy as time went on.

 

Tweeking the black and white levels revealed more of the structure in the surrounding nebulosity, being quiet prominent when a low white level is used (but the background and stars become quite washed out and the image was naturally not aesthetically pleasing). More definition of the central pillar was gained by using a higher black level at the expense of losing background nebulosity.

 

As time went on the lighter pillar behind the central dark pillar became more visible. I am quite pleased with the end result:

Next was M20 - an object that caught my imagination as a kid and was one of the reasons I got into astronomy. By the time I started observing, M20 was very low in the sky and just above the tree line. This also meant that the light from one of my neighbours conservatory was drifting into the field of view (the washed out patch on the right). This was getting drastically worse, to the point I could only observe for about 2 minutes!

 

The HII nebulosity was quite distinguishable, with the dark dust lanes easily visible in this region. There is no hint of the reflection part of the nebula (the blue bit), I think is probably due to the light interference, low altitude and I am pretty sure if my memory serves the Astronomik UHC filter cuts that part of the spectrum out - will double check that one.

Definitely something to return to - maybe my neighbour will be out (or watching TV in the dark) next clear sky?

Time to re-visit an object from the previous night - NGC6888 The Crescent Nebula. I was keen to see what difference the UHC filter made. There was patches of high cloud (again!) but I don't think these had much of an effect. With the UHC in place, even on the first (noisy) exposure, more detail was visible in the inner nebulosity. The outer part of the nebula had more definition with the filter. The inner nebulosity became more visible by lowering the white level to un-aesthetically pleasing levels, but it's still pretty faint. Definitely a better result from the previous night. Next time I think I will try 60 or 90s exposures and see what that does (will see how alt-az goes - might need to switch to EQ mode..).

I then intended to observe NGC7026 The Cheeseburger Nebula. This is a planetary nebula in Cygnus. Sadly I could not find it, so I am going to read up and see if maybe its emissions are not suitable for a UHC or get a better clue where it is located so I can more successfully star-hop to it. Failing that, not to be beaten, I am going to upload images to astrometry.net, get the actual scope position and by hook and crook get my way to it. I also need to check the size - it might be so small it appears too stellar at 680mm FL.

Fun times! 

[Martin Meredith]

That is one stunning M16 Paul! The RC is really delivering some good star images too. In my M16 I get a lot more star bloat which wipes out all but the main pillar.

For M20 I've just about caught the blue part from what is probably a darker site than yours (also having the colour Lodestar helps in distinguishing it from the background).

For some time I've been using the Notes application to write down a list of targets, and then add some comments during the observation itself. Not having to worry about dark adaptation makes the whole note-taking experience so much easier. I've made more notes in the last 4 months than during several years of pure visual observing!

Martin