Category: Deep Sky

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Deep Sky Galaxy Nebula

Abell 70

After my visit to the Institute of Astronomy at Cambridge the sky stayed clear and I paid a visit to the observatory to try and assess the tracking problems we’d experienced last weekend. Somewhat strangely, there was no repeat of the alt drift when pointing south although there is still a large periodic error in Az. Frame rotation is also problematic when pointing south so the maximum exposure I could use and still keep a reasonable number of the exposures was 15 seconds.

Abell 70 is faint so I didn’t hold much hope of actually being able to image it with this short exposure and my QHY9 single shot colour camera. To compensate, I took about 60 images. The nebula did not show up at all on any of the individual sub-frames.

Once mis-tracked frames were rejected I was left with 38 images which were bias subtracted and stacked with an SD Mask function. Field flattening was performed with GradientXterminator followed by a lot of noise reduction.

The nebula shows quite nicely along with the background galaxy. The nebula is about 45″ across and magnitude 14.5. The galaxy is magnitude 16 and the central star, 18.6.

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Deep Sky Nebula

Kelling – Pt 2

The second target for Saturday night was Mu Cepheus and IC1396 again. I’ve looked at this one recently but with the 10 minute sub-frames I was getting I wanted to see if there was any more detail possible. Nine 10 minute frames were stacked and then processed in Photoshop. The biggest problem area is around the Garnet star itself and there’s a dark ring I haven’t managed to eliminate yet. The problem is caused by the high difference in brightness between the star and nebula and I need to research some techniques for reducing this artifact.

Comparing this image with the previous one, there’s more subtle detail in the dark nebulae.

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Deep Sky Nebula

Kelling Heath

Another year is slipping by and the Autumn star party at Kelling is over. After missing friday due to illness we arrived on Saturday in time to catch the trade stands before they closed. From Altair Astro a new dew strap for one of my Canon lenses, dew heater for the red dot finder and a 2″ extension tube for the club’s 20″.

Of course, friday night was one of the best nights of the year. Various superlatives were being used to describe it and I missed it all. Saturday night was supposed to cloud over after midnight but, by the time we emerged from the bar at 9pm the sky was clear and that’s the way it stayed for the entire night until I packed up at 3.30am and retired to the tent.

With the chance of the sky clouding over I rushed the polar alignment and focus. Despite this, the polar alignment worked surprising well and I was able to take 10 minute exposures with the 75-300mm zoom set at 135mm. The focus was less good and I wasted some time before I realised and refocussed. First target was NGC 7000, The North American Nebula. After rejecting the out of focus images a couple had slight trailing leaving me with five 10 minute frames.

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Deep Sky Galaxy

20″ – First imaging test

Last night was the first opportunity I’ve had to test some of the improvement work that’s been happening on the 20″. I had some early problems with icing in the Atik and a dead ethernet connection (someone had plugged a cable into the wrong port). Once these were resolved I started with NGC 7814, an edge on spiral galaxy in Pegasus.

Exposures were 10x 2 minutes, binned 1×1 with 5 second guiding exposures. I had to reject 2 images due to star deformation.The icing problems with the camera trashed my sky flats and I didn’t have any suitable dark frames so the images were hot pixel filtered before combining.

NGC 7814 is about 40 million light years away and is sometimes known as ‘The Little Sombrero’. Apparent size is 5.5′ x 2.3′.

The second image was less successful. The target was NGC 7479, also in Pegasus. This time I attempted an LRGB sequence but many of the images showed jumps in the altitude direction. It may be that the altitude drive is slipping at certain positions. This will require further investigation. Here’s the 15x 2 minute luminance frames.

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Deep Sky Nebula

Sadr and the Crescent nebula

With a full moon in the sky last night was a test session for my new IR block filter and the Geoptik Canon lens adapter. Back focus is at a premium with this system with only 7-8mm to squeeze a filter into. The new filter appears to be slightly too thick but was within a whisker of achieving focus so there may be hope yet. Swapping the filter out I refocussed on Sadr and took 10 3 minute exposures at 135mm. A heavy crop of the field removed the worst of the background gradient introduced by the moon but some artifacts of this remain after processing.

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Deep Sky Nebula

Veil Nebula

The Veil nebula is something I’ve been meaning to take an image of since I got my QHY9 camera and last night was the first opportunity I’ve had. The skies are getting dark again after the summer twilight, there was no moon and conditions were pretty much as perfect as they’re going to get in the UK.

Using the Canon 75-300mm lens at a focal length of 100mm I took 20 5 minute exposures followed by 30 2 second flat fields. This lens is badly afflicted by vignetting and the flats compensate nicely. With Cygnus high in the sky and little moisture to reflect the ever present light pollution gradients weren’t a problem for this wide field.

The nebula doesn’t stand out particularly well against the backdrop of Milky Way stars in this image. To improve visibility, I’ve cropped the image fairly tight to the nebula as otherwise it’s rather lost amongst the stars.

Edit: Image replaced with reprocessed one.

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Deep Sky

Mu Cepheus

The run of good weather has continued and last night stayed clear so I stopped up late enough to grab some pictures of the Mu Cepheus area of the Milky Way. The trouble with being at 52 degrees latitude is the endless twilight at this time of year. While it’s getting better by the day it’s going to be next month before we start to see skies that can be classified as dark.

So, with the sky still pretty light I took 10 5 minute exposures with my QHY9C behind a Canon 75-300mm zoom set wide open at 135mm. Flats had to wait until tonight as the fuse blew in the cable to my EL panel.

This is a re-processed image as I was unhappy with the first one. I cut the first two frames from the sequence as these were worst affected by the light sky, especially in the lower left corner. The colours are rather more muted in the nebula but have been preserved better in the stars.

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Deep Sky Galaxy

Remote imaging

Long time readers of this blog will know that from time to time I’ve used remote telescopes for imaging. On occasion, it may be the only way to photograph a particular target e.g. southern hemisphere, or it may provide access to equipment that is out of reach financially or just wouldn’t be practicable to implement at home. I know that this causes problems for some amateur astronomers who may feel that you can’t take ownership of an image if you can’t claim every stage of the process as your own, including actual possession of the equipment used. I take a wider view in that, provided you have identified the sources used, no one is being misled as to the provenance of the images. The individual astronomer still has an input in the collation and presentation of the data.

While attending a meeting of the Webb Society at the Cambridge Institute of Astronomy my eye was caught by one of the pictures on display, an image of a gravitational lens. Such objects were predicted by Albert Einstein and are formed when light from a distant object is bent (or lensed) by gravity around a massive foreground object. In this case the foreground object is a Luminous Red Galaxy (LRG 3-757) and the source is a star forming galaxy. The ring has a diameter of 10″, the LRG has a redshift of 0.44 (or 4.5 billion light years) and the source galaxy has a redshift of 2.379 (10.8 billion light years). Both components are approximately magnitude 20. For anyone interested in the detail the Astrophysical Journal paper is available here. Once home, I did some initial research on this object and went looking for images.

Some time ago I’d become aware of the Hubble Legacy Archive but not had the time to take a detailed look at it. A recent Sky & Telescope article by Robert Gendler rekindled my interest and having found the RA and DEC coordinates for LRG 3-757 I entered them into the search engine on the site (http://hla.stsci.edu). This returned a list of images in the archive for this object and three looked suitable for a colour image; 475nm, 606nm & 814nm corresponding to blue, green and red wavelengths.

Downloading this dataset took some time (each image was 300MB) and each was stretched in FITS Liberator before colour combining using Maxim DL. Once the colour balance looked roughly right I exported the tiff file into Photoshop for fine tuning and noise reduction.

The result is here:

Is this the ultimate in remote imaging? Well, I’ve finally got access to a telescope that’s unaffected by clouds and atmosphere & cost billions of dollars to build, commission and service. It seems a waste not to make full use of it.

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Deep Sky Galaxy

NGC 4517

I found this galaxy in Sue French’s wonderful Deep Sky Wonders book while looking for a suitable target for the 20″. With the summer twilight we didn’t get started on it until after midnight and got 15 1 minute exposures. Of these, 6 were rejected due either to car headlights or star trailing so the result could use a lot more exposure.

What atracted my attention was that it’s an edge on spiral (as opposed to the Virgo cluster’s usual ellipticals}, it’s fairly bright and it’s also large at 11′ long.

The sharp eyed will notice that the picture’s identification is NGC 4437. This galaxy appears to have two designations.

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Deep Sky Galaxy

The Sombrero revisited

I finally figured what I was doing wrong with the colour and here’s the final result. In a nutshell, auto-background equalisation coupled with too much contribution from the red channel was resulting in some pretty strange effects.

The Sombrero is never well placed from the UK and only gets to about 25 degreees elevation at the Breckland observatory.