On 9th May 2016, Mercury transited the sun as viewed from Earth for the first time since November 2006. The transit was well timed for observation from The UK and Europe, starting at 11:12UT and ending at 18:42UT. I attempted to view and to photograph the transit using both my WO FLT110 with a Herschel Wedge from Lacerta, as well as visual work through the Takahashi FC60.
To image the eclipse, I used a combination of the WO FLT110 working at native f7 using the Herschel Wedge, with ND3.0, IR/UV blocking and Wratten #57 filters. Situated behind this combination was the ASI120MM camera – the plan being to take video captures of the event, processing into images later with Auostakkert/Registax.
However, British weather being itself, I only had a very short window of clear sky at the beginning of the transit during which I could grab one decent shot showing Mercury (bottom left), AR12542 (top) and AR12543 (lower), and with AR12544 developing at the top left. This image made it onto the Meridian (West) news at 6pm that evening, and is on Simon Parkin’s Mercury Transit blog post as well.
After this 10 minute spell of clear(ish) sky, I had very little opportunity to see the transit again – there was a short period here and there where I was able to visually observe Mercury and the sunspots on the disc, but by 3pm I was completely clouded out, with rain following later in the evening….
Planetary work is not really my strongest skill in astrophotography, but with Jupiter near it’s highest in this and the past few years, it is well placed for photography from the UK.
Additionally, this is one of the first chances I have had to get images with the large 14″ reflector using my ZWO ASI-120MM. I chose to use the Astronomik 742nm Near-IR filter to try to improve the results: on both occasions it has resulted in much better resolution than with unfiltered white light. In addition I used a Meade Series 4000 2x Barlow lens. With regard to conditions, I think I’m a little limited by my observing location where I have to observe over the top of our row of houses – the thermal currents (including from boilers, open fires, etc) are likely to do little to help the seeing here..!
First image is from the 17th March during Callisto’s shadow transit (taken at 23:08UT) – Callisto itself is also visible at about 7 o’clock (and clearly resolved into a disc – at 1.5″ the seeing was clearly not so bad..!).
Second image was taken on 22nd March 2016 – the results weren’t quite as sharp as those from the 17th. Unsure if this is a focus/collimation issue, or if the seeing just wasn’t as good. The processing is a little heavier to try and bring out the cloud contrast where possible too. Collimation of an f4.5 scope is fairly critical, and any slight shift can reduce image quality quickly. Equally, at f9, focusing is tricky with a fairly dim extended object – this is something I need to work on in the future – a Bahtinov mask is on the list of makes for when I have successfully rebuilt this scope.
All images were 2 min videos, recorded using FireCapture, processed in AutoStakkert, Registax 6 and Photoshop CS4.
We’ve had some poor weather this winter so far for astronomy, but we’ve had some clearer nights in the last week, but with the moon at a fairly full phase. So I’ve been working with the 14″ SPX350 in honing my high resolution lunar work a bit.
I had two fairly average sessions working with the ZWO camera in unfiltered mode, but suffered a lot from poor seeing (potentially due to thermals from houses I image over) especially with stacks coming out with “ghost craters”. However, for this run of images, I used an Astronomik ProPlanet 742 filter I have just purchased (this is a near IR filter passing wavelengths longer than 742nm).
This has given a very good set of results – with three images surpassing the resolution I’d previously been able to get – and working at a focal length around 3200mm too by using a Meade series 4000 barlow lens in front of the camera and filter (giving a resolution of about 0.24″/pixel). Previously, I’ve only got good results at prime focus. From a first time using it, it certainly appears that this filter does help with larger apertures where seeing is not perfect. Images, while not totally unaffected by seeing, seemed a lot more stable in terms of high speed jitter or double vision on craters.
Images were taken around 98% illumination so all the images are from areas around the eastern limb of the moon – with limited targets available and with cloud rapidly rolling in, the session was somewhat curtailed!
Grimaldi, Hevelius, Cavalerius:
Phocylides, Nasmyth, Wargentin and Schickard:
Field centered at: RA: 14h 03m 12.6s, Dec: +54° 21′ 16.7″
Up: 178 E of N.
(plate solve from nova.astrometry.net)
The Pinwheel Galaxy, M101 is located in Ursa Major, and I found this a surprisingly tricky object to image – it has low surface brightness, with a lot of faint outlying regions. I also appeared to have some small issues with the flat fielding process here – there are a couple of very large dust bunnies in the raw data that haven’t quite been subtracted away and there’s a touch of clipping to deal with this.
Add to this some faint colour gradients (attempted to sort out gradients!) and a couple of bright stars in the field and it became something very tricky to try and get right (and I’m still not 100% convinced that it’s truly there yet…).
The fainter galaxy to the right (east) of M101 is NGC5477, which is a dwarf galaxy at about the same distance (~20MLy). There are lots of fainter objects in the image as well: the brighter galaxy to the upper left of M101 for example is MCG+09-23-25, and there are also loads of other faint galaxies, galaxy groups and QSOs lurking in there. Using a solved fits file in Aladin is very instructive here!
I used fairly long exposure lengths (I was using the FLT110 at f7 here, a shorter focal length would be a major bonus in truth – at f4-5 this would be a much deeper image!). Exposure details are as follows:
WO FLT110 @ f7 on Losmandy Titan, ST2000XM cooled to -20C (images on 18 & 19-Apr-2015)
L: 4.5hrs (1×1)
R: 70min (2×2 binned)
G: 48min (2×2 binned)
B: 48min (2×2 binned)
The Luminance for the image was processed using a Lucy-Richardson deconvolution (3 iterations) using CCDSharp.