We are having a spectacular run of clear stable air which has allowed observing almost every night for past 4 days. And a few more days in the forecast. I had not planned on doing anything this night, but after walking the dog decided to take the binoculars out to the front porch at 10pm and just scan around to see what i could find. I was using the 10×50 Celestron’s which are quite good quality.
I was surprised how well the objects stand out against the background light. Previously i had done this the first quarter moon rising. With no moon in the sky there was a lot more to find.
- M22 – Sagittarius Cluster: A mag 6.5 dense globular cluster. Stood out well and a compact round shape.
- M28; Mag 8.5 globular cluster. Just visible as a brighter fuzzy spot but compact circle.
- M8 – Lagoon Nebula: Mag 5 Emission Nebula and Open cluster. easily seen in binoculars but not visible naked eye. The 4 brightest stars of the open cluster form jagged horizontal line through the nebula and were easily resolved.
- M20 – Trifid Nebula: Mag 5 Emission Nebula: I could not see it! There is a dense star field at 11 o’clock which might be M21 (open cluster) but i don’t think so.
- M16 – Eagle Nebula: Mag 6.5 Emission Nebula. This should up as a faint but large bright area in the binocular FoV. Note that the Hubble’s “Pillars of Creation” are here.
- M17 – Omega Nebula: Mag 7 cluster with nebulosity. Just should and a little east of M16 it appeared as another faint fuzzy patch. M18 is also in the area, but i didn’t take any note of it.
- M11 – Wild Duck Cluster: Mag 7 open cluster. Showed up well as a dense bright oval. No stars resolved in the binoculars.
- M10 and M12 – Gumball Nebula: M10 is mag 7.5 and 25′ diam; M12 is Mag 8, 16′ diam. While M12 is fainter, its more compact to more of the light is concentrated in the centre and making it easier to see. M12 was easy to find while M10 appeared noticeable fainter.
- M57 – Ring Nebula: Mag 9.5 Planetary Nebula. I was pleased that i could find it. Although it was just at the limit of being detectable and appeared as a slightly brighter fuzzy spot with viewed with averted vision.
- M31 – Andromeda Galaxy: Mag 4.5 and 2.1deg long. I could not see it visually as it was still rising out of the glow of the neighboring city. Through binoculars it was easy to find with the elongated shape obvious.
I put the HD11 on the CGE Pro and realigned it. My main purpose was to setup an imaging run of the Milky Way using the Canon T2i (with astro filter mod) and 28mm wide angle lens. This time using the motorized tracking of the CGE Pro. I didn’t need the HD11 for that of course, but i also wanted to check out M11 and the Iris Nebula with the larger scope.
M11 is called the “Wild Duck Cluster” because the bright triangle of three stars represents a flying flock of ducks. I think that’s a bit of stretch of the imagination. As well, i thought it’s only geese that fly in formation. According to Wikipedia, M11 one of the densest and richest open clusters with approximately 2900 stars. Its listed as magnitude 6.3 with a diameter of 14′.
Previously with the 106mm refractor M11 looked like a dense fuzzy oval – ie like a globular cluster. With the HD11’s 280mm aperture it was a spectacular sight with many individual stars resolved. The Hyp 24mm i was using yields 116x magnification and a real FoV of 35′. So M11 at 14′ filled half the eyepiece. It still looks more like a spare globular cluster though.
I also checked out the Iris Nebula (NGC 7023) to see if more of the nebula was visible with the larger aperture. Surprisingly it wasn’t a lot better! I didn’t have to use averted vision to see the nebula, but there wasn’t much structure evident. I was hoping to at least see the triangular “hole” near the bright central star, but i could not make it out.
The rest of the time was spent taking two image sets of the Milky Way. One near Sagittarius on the horizon. And the other high overhead near Cygnus.
The images for those runs are still being processed.
With the moon out of the way until about 11:20 it was a good night for some visual observing. The recent tree trimming cleared a lot of the lower sky as well as a good section due south so more of the Milky Way was visible from the observatory.
I setup the 106mm f/6.5 refactor on the CGE Pro in the observatory and used the Hyperion 24mm eyepiece. This provides a 2.4deg real FoV and 29x magnification. I was observing from about 9:00pm edt to 10:15pm.
On the list was:
- M20 and M8: Still below the tree line
- M11 Wild Duck Cluster: Its classified as an open cluster but looks more like a globular at 29x. Its now on the list for the next photography run.
- IC 4665: sparse open cluster that more of less filled the 2.4deg FoV.
- NGC 6818 Little Gem: could not find it. Presumably because of the sky glow to the south.
- NGC 6822 Bardard’s Galaxy: could not find it.
- M27 Dumbbell Nebula: Obvious, bright and relatively large. No colour or structure discernible.
- NGC 7023 Iris Nebula: Central star visible in the 80mm finder. The nebula is visible with averted vision. Although after awhile i could convince myself that i could see the nebula while looking directly at it.
I look a few frames of the Milky Way with the unmodified Canon T4i and a Sigma 28mm f/1.8 lens. This was tripod mounted (no motor). I used ISO 1600 with 8sec subs. The processed result (with calibration frames is below.
The second imaging run for the Iris Nebula – NGC 7023.
Things went a little better. I realized that i had forgotten the field flattener on the AT106 for the first imaging run on Sept 5th. So i added that to the image train and made moderate effort to align the camera to the same orientation. The field flattener is not a reducer, so i was counting on being able to combine the subs from both sessions. The corners would be a bit soft but better than without.
The imaging run went ok with a little more time than expected to centre to object in the FoV. The scope does not point well to the north. Perhaps a better PA would help that.
I started the imaging run at about 11pm EDT and setup the imaging run for 6hrs which would take me to astronomical twilight. At 5am i went out to shut things down and found that after 130min (13subs) i lost guiding. Perhaps it clouded over, but i am suspicious that the previous run also had the same error at 130min. That being that FlexRx reported two large a flex rate.
So again i got 2hrs of data when i was expecting 5-6hrs.
I did a quick stack and processing and found that there was a large dust blob that the flats could not remove. Probably on the field flattener. Mental note – check and clean the optics and sensor before an imaging run.
I combined the two image runs together and then repaired the “hole” caused by the dust blob by copying that piece from just the run 1 data. It was a bit tedious to create a mask and blend the offending area so that it was not too noticeable.
The image after calibrating and stacking with the custom tools and processing more carefully is here:
It was clear last night so i scrambled to setup the scope. The pier adaptor still needs some adjustments, but i decided it was good enough to use. That meant completely assemble the scope from the pier up.
I was using the AT106 for which i had mounting brackets and a plate for the CGE Pro (Losmandy style) already assembled. However, i had not used this with a piggyback guide scope. So i had to reconfigure the mounting brackets to allow for the guide scope.
The pier adaptor went on fine and the mount is nice and solid. I had previously done a rough polar alignment (PA) in situ with the top part of the pier plate only fastened at the centre. This allowed PA to be done by rotating the pier top plate rather than using the azimuth screws which have limited travel. Then it was dismantled again and the top part securely anchored to the bottom plate. So i was pretty sure the scope would be close to aligned. It was in fact almost perfectly polar aligned and on first try only required a little tweaking using the all-sky method.
Getting the wires and gadgets organized proved to be more time consuming than planned. I had not used the scope for 3 months and with it completely dismantled had to recreate the wiring from scratch. It took 4 trips to the basement to retrieve the forgotten components.
I started at 8pm and was up and running by 10pm – including alignment and the PA. Imaging run started around 11pm. I figured i had 4 or 5hrs of imaging time so set the image acquisition program for that amount of time. At 4:30am i went out and shut things down and started taking dark frames.
Unfortunately i forget the dew heater on the guide scope! There was a heavy due that night so i lost the guide star due to condensation on the guide scope after only 2hrs of the planned 5. Oh Well! Hoping for more time in a few days.
Here is the rough processing of the first iteration which includes all the calibration frames. The colour balance is on the green side due to the generic stacking process. (I have a custom set of tools that provides a better colour balance step. But its a time consuming process to run. The standard tools are 100% automated and therefore simple to execute.) This version is resampled to about 1/3 the full scale to account for the high noise. More subs will mean less noise.
The fall Equinox occurs on September 22nd at exactly 20:44 UT (4:44pm edt). On this date and time the Sun crosses the equator making the day and night of equal length. After that, the daylight hours will get shorter and the nights longer – which is of course good if you’re an astronomer. At the start of the month, nautical twilight begins at 8:47pm – the time when the brighter stars can be seen (those used for navigation). By the end of the month, nautical twilight will be at 7:48pm – almost an hour earlier. Astronomical twilight – the start of the darkest part of the night – begins at about 9:26pm on Sept 1st. By Sept 30th, Astronomical twilight begins at 8:23pm.
By mid September at 9pm, the constellations Lyra (the Harp) and Cygnus (the Swan) are directly over head. Hercules is a little to the west but still in a good position to see. The large constellation Pegasus (the Winged Horse) is rising in the east. The tail of Pegasus is actually the constellation Andromeda (daughter of Cassiopeia) and home to the Andromeda Galaxy which will be featured next month. The Milky Way is still prominent in the south with Sagittarius (the galactic centre) a little west of the meridian.
The Summer Triangle – an asterism formed by the three bright stars Vega (Lyra), Deneb (Cygnus) and Altair (Aquila) is due south and stretches from the celestial equator to almost the zenith. These stars are in the top 20 list of the brightest stars and are the brightest stars in that area of the sky. So the “summer triangle” is easy to spot.
A fun binocular object is Brocchi’s Cluster (Collinder 399) but better known as the Coathanger. In 7×50 binoculars it looks like a perfectly formed coat hanger in the centre third of the FoV – albeit upside down. The Coathanger is in the lower third of the Summer Triangle along the Altair-Vega line. To find it, locate Altair with binoculars and then scan a third of the way towards Vega. The Coathanger should be easy to spot. (While Cr399 fits nicely between Sagitta and Vulpecula, these constellations don’t stand out well.)
Another great binocular target is Ptolomy’s Cluster (M7). It’s a large open cluster that will occupy about a quarter of the FoV of 7×50 binoculars. It’s only 6° above the horizon though so requires an obstructed view.
M13 – the Hercules cluster and M92 are still the best bets for binocular globular clusters of the season. M27 and M57 are nice Planetary nebulae for moderate scopes either as visual or photography objects. The diffuse nebula of M8 and M20 are best seen in photographs due the red colour. Although the brighter reflection component of M8 is visible in small scopes and the open cluster M21 near M8 is also visible.
The photography project for this month is the Iris Nebula (NGC 7023, Caldwell 4) – a bright reflection nebula in the constellation Cepheus to the north. NGC 7023 refers to the open cluster while the nebula is LBN 487. The grouping is listed as mag 6.6 and 18′ in diameter. Although the region of interest is more like a degree wide. Images of it in real colour show it to be rather blue-purple with significant brownish dust lanes. The scope of choice is the AT106 with the Canon T2i which yields of FoV of 1.8×1.2°. 6-8hrs of imaging should be enough for a decent result which usually takes two clear nights to acquire.