OK, here's the third and final couple of pics, the target was M27 (aka The Dumbbell Nebula, NGC6853), a planetary nebula in the constellation of Vulpecula. Again, you get one version with the diffraction spikes and another without. Click 'em for more bigness:
M27 (NGC6853) as processed.
Subs: 22 light @ 120s, 22 dark @ 120s and 20 flat @ 2s, all ISO200.
D50 and MPCC on the C8N, guided with PHD.
As previous but with added spikes.
That's yer lot.
OK, here's the second couple of pics, the target was M29 (aka NGC6913), an open cluster in the constellation of Cygnus. You get one version with the diffraction spikes and another without. Click 'em for more bigness:
M29 (NGC6913) as processed.
Subs: 41 light @ 60s, 41 dark @ 60s and 20 flat @ 2s, all ISO200.
D50 and MPCC on the C8N, guided with PHD.
As previous but with added spikes.
There's even more...
I managed to escape from the house last night and took refuge in my obsy. The skies weren't particularly clear, mainly due to the pending moon-rise, and the seeing was only middling, but I managed to get some dSLR pics of some Messier objects. For the first time I took some flat-frames as well as the customary lights and darks, it wasn't the hassle that I thought it would be, mainly due to me thinking laterally and adapting the "white tee-shirt method" by using a white microfibre cloth over the end of the scope.
The results are worth the extra effort, I reckon - there's less hassle trying to get Photoshop to correct the vignetting inherent in images of this kind. I'll probably knock-together some sort of white-screen contraption for the end of the scope now that I've got a better idea of what works.
Here's the first couple of pics, the target was M13 (aka The Hercules Globular Cluster, NGC6205) and it looks like I've managed to catch the faint smudge of NGC6207 near the top edge of the uncropped version:
M13 (The Hercules Globular Cluster, NGC2605) in the centre, NGC6207 to the upper-left(ish).
Subs: 50 light @ 60s, 50 dark @ 60s and 20 flat @ 2s, all ISO200.
D50 and MPCC on the C8N, guided with PHD.
Cropped version
There's more...
At last - a more-or-less cloudless night. It was a chance to have a look through the new frac and to try out a few new tactics.
The first thing to do was to get the frac lined up with the Newt so that they were both looking at the same thing. Using Starry Night Pro and the ASCOM/EQMOD setup to control the mount meant that finding a suitable target was a doddle. I settled for Betelgeuse, the bright Red Giant forming the left shoulder of Orion. After a minor tweak to get it in the centre of the Newt's FOV, I adjusted the other scope and the two finders so that it was central to all.
Next up was my first attempt at web-cam autoguiding. The software of choice for this was PHD, as it was recommended by several folk that I've quizzed about the subject. The webcam was another Philips SPC900NC, famed for its ability to get good images in near-darkness due to the high-quality Sony CCD. Although the process was new to me, it was simple enough... slap webcam into frac, find and focus on a suitable star, press the "Start" button and that was it - it's self-calibrating and sends pulse-guiding signals via the ASCOM/EQMOD setup so that there's no data conflict. Beyond all expectations, it worked first time, so I was pleased about that.
Then it was time to find a suitable target for a test image. I didn't want to go for a complex victim like a nebula or galaxy, as I wanted to be able to examine the star-images to check for trailing and guiding errors. After scanning through lists and across the sky, I chose M35, an open cluster in Gemini, as it was high in the sky and would allow a decent period of time for the exercise.
So then it was time to go for it. I slewed the Newt to centre on the few visible stars of M35 and then adjusted the frac to find a guidestar, hit the buttons and let it go. Using the D50/MPCC combi in the Newt, I set the laptop to take a series of light and dark exposures of varying duration, went inside to make a brew and then sat outside skywatching in the strengthening wind. Aside from a couple of bright and unexpected meteors speeding over from the East, there wasn't much activity visible to the naked eye, but the binoculars revealed much more. Time was well-spent gazing at Orion's nebulae, The Pleiades, Andromeda and a few other familiar objects.
After the camera had finished with M35 it was time for a change. Mars was now within sight low in the East, so I slewed to that and had a good look around. The gibbous phase was obvious, but other than that it was hard to see anything as the wind had become so strong that it was deflecting the scope so much that the image wasn't stable. I did set up to catch Mars on the original webcam via the Newt, but didn't get any data because the target was moving off-chip due to the blowy conditions. After a few minutes of frustration the sky clouded over and that was it for the rest of the session.
In all it was a good exercise. Guiding sussed, first-light for the frac and some frames of M35. The following day I chugged through the images to cull all of the longer exposures, as they were blurred due to wind-shear. After that, the laptop was busy processing the remaining data, and eventually it spat out this:
M35 (NGC2168) in the centre, NGC2158 to the lower-right.
45 light and 45 dark frames restricted to 60 second exposure times due to wind-shear.
55 light and 55 dark frames with exposure times up to five minutes were considered unusable.
Despite the dumping of most of the frames it seems reasonably good to me, seeing as it was done for process-checking rather than as a pic for the mantelpiece. There's a bit of star-elongation due to wind-shear, but there are hardly any errors visible due to guiding, which is what I needed to know. Next time out I might try for some decent pics of this pairing, as there's something quite appealing about the arrangement, with the combination of newer blue and older red stars.
If you've a mind to go out looking for this target, here's a rough guide:
Finding M35
I'd not planned to go out observing, but there was an hour or so of cloudless sky yesterday evening and I had a little time to spare. This was an opportunity to sky-test the Nikon AF-S DX NIKKOR 35mm f/1.8G lens to assess how well it is suited to taking widefield pics of the night sky.
In particular I was looking to see:
The challenges would be to see if I could find a reasonable exposure time, get a small number of images for stacking, and then process-out the vignetting, star-trailing and any light-pollution.
Jupiter was in the southern sky so I pointed the camera at it to get the autofocus set. I then turned off the autofocus and fixed the position of the lens focus ring by the judicious application of duct-tape.
Next, I pointed the camera at the Cassiopeia / M31 Andromeda area and took a few test-frames of various durations. Eventually I settled on an exposure duration of 30 seconds and took 12 pics.
These were stacked in DSS and hurriedly processed in PSCS3, and here's the result:
Mouse-over the pic for details, click it for a bigger pic.
I have to say that I'm quite impressed with the raw images that this lens produced. Shooting with the aperture wide open captured a lot of light, and for a change I had to tone down the details rather than go through the usual routine of having to drag the details out of the murk. I'm damned if I can find any coma in the raw frames, which means that there'll be no need to crop off any bad areas. The expected vignetting was dealt with in PSCS3, the compensation isn't perfect but to be fair I've only done a quick fix, no doubt I could get it better if necessary. The amount of star-trailing was acceptable, and I'm confident that I could get it processed out if necessary and if I had enough time.
And the framing? I'm happy with it for targets the size of Cassiopeia, but the capture-area might be a tad small for meteor-work. Time will tell - between now and the end of the year there will be plenty of opportunities for snapping a few meteor trails (more on that in another post very soon (but don't hold your breath)).
The recent change in the weather's been bad for some, but good for others. Last night it provided an opportunity that I wasn't going to miss - the two previous evenings had started dark and clear, but were affected by fast-moving patches of cloud by the time I was free to observe. This time I figured that it would be better - the forecast sub-zero temperatures would only be achieved without the insulating layer of cloud, and so it proved to be - nice and clear except for an intermittent haloing of the brightest stars due to high-altitude conditions, probably ice-crystal formation.
I managed to give the scope only one hour or so to cool down before pressing it into service, but I wasn't going to be doing any high-mag work so it didn't matter that much. I took more time than usual getting a good polar-alignment, so by the time I'd got properly set up, it was quite late.
As usual, there's always something new to try, this time I was trying out the camera-control features of MaxIm DL, another nice bit of software that I want to get to grips with. This software will happily run a USB connection between the laptop and my Nikon D50, allowing me to set up a complete series of exposures (darks, lights etc) and then let the lappy do the rest, including downloading and saving direct from the camera instead of writing to the SD card. The only restriction that affected me was the 30-second maximum exposure time allowed by the kit that I have - the Nikon D50 needs IR shutter-control for exposures longer than that, USB will only work up to that limit. Never mind, what I've got will suffice until I acquire said USB-IR controller.
Anyway, back to the sky...
The prime target was M45, The Pleiades, the Seven Sisters, call it what you will. It's a distinctive pattern in Taurus, and one that I've observed visually many times. After locating it visually with the scope, I checked that the mount was tracking it OK then exchanged the eyepiece for the dSLR body. After taking a few shots to verify the focus was good, I set the software to take 100 x 30s dark frames then 100 x 30s light frames (all ISO 200 NEFs), set it running and retired to the kitchen to warm up with a strong cuppa (the temperature outside was down to +1C by then).
After donning my Alpkit down jacket, I went back outside with the binoculars to have a look around while waiting for the lappy and camera to finish their business. The Hyades (Melotte 25, or Collinder 50, or Caldwell 41) were an impressive sight in Taurus, and I spent more than a few minutes looking at the Orion Nebula (M42, NGC 1976). I spotted a few other "fuzzies" which I noted for future observing sessions.
By the time the M45 frames were finished, the temperature had dropped below freezing, and the outside of the scope tube was iced up. Fearing that this meant the end of the session, I checked the mirrors and the camera, and was pleasantly surprised to see that they were unaffected. Looking at the watch I realised that I didn't have enough time for another objective that would require a 200-frame batch, but I wasn't about to pack up in such good conditions, so I picked a secondary target that wouldn't need as many exposures.
M36 (NGC 1960), a neat open cluster in Auriga, seemed to fit the bill, so I programmed-in a 50 dark / 50 light sequence and let the software do the rest while I sat watching through the binos.
As usual, the packing away afterwards was a moist affair, with the iced-up kit forming puddles on the kitchen floor and the other seemingly-clear gear (such as the lappy) acquiring an alarming layer of condensation as soon as it was taken into the warm.
Anyway, here are the fruits of my labours, after giving the raw frames a right good seeing-to with DSS, Photoshop, Noel's Actions and a few cups of Assam-flavoured caffeine, and with the help of my two trusty manservants, Benson and Hedges:
M45 - The Pleiades
(Nikon D50 at prime-focus on C8-N, ISO 200, no filters, 100 x 30s light frames + 100 x 30s dark frame stacked with DSS, processed in PS CS3 with Noel's Actions)
M36 - an open cluster in Auriga
(Nikon D50 at prime-focus on C8-N, ISO 200, no filters, 50 x 30s light frames + 50 x 30s dark frame stacked with DSS, processed in PS CS3 with Noel's Actions)
I might re-stack them in MaxIm DL later, to see if they come out any better. If they do, I'll post the results.
Why "Scooby" in the title? You work it out.
