This is NGC 4725 and cohorts. It looks NGC 4725 had a tangle with 4747 and neither came off well.
This is NGC 4725, to the top left is NGC 4747 which has been disrupted by NGC4725.
Imaged from the 22nd to 25th March, total integration time was 9 hours and 15 minutes, (2h20 Blue, 2hr53 Green, 2hr05 Red, 1h56 Ha). Imaged with my ASI1600mm pro, ZWO filters and trusty Orion Optics UK 250mm Newt on my CEM70G.Ā Captured with N.I.N.A, processed in PixInsight and tweaked in Paint Shop pro.
There are more galaxies here than you first realise.
That was a remarkable few days of good weather with DEC guiding often running as low as 0.23 rms and even RA sub 0.4 for much of the time. I’d like to think much of that performance was down to my re-jigging the balance and fine tuning the meshing of the worm gears – I had had trouble getting below 1 arc-seconds rms for the last 2 years. I know others also reported good guiding in many parts of the UK on the same days so its probably just freaky weather. Time will tell.
IC410 is a dusty star forming region about 12,000 light years away.
I’ve finally grabbed enough O3 to attempt an HOO combination. This time of year, the nebula stays above the neighbours’ trees for about 2 hrs after dark. I doubt I’ll be collecting more on this one until next year.
This image is the result of 9hrs Ha, 7hrs O3 and 45 mins RGB for the stars. By far the best stars were the Ha ones – that data was collected earlier in the year when the target was higher. I used Ha stars as a mask which tightened them a lot.
The initial HOO mix was Ha, O3, O3*.85+Ha*.15. I had to apply TGV noise reduction on chrominance because the O3 was still pretty noisy. I’m quite happy with the overall results for the amount of data.
The Tadpole Nebula IC410 in HOO with RGB stars
The mono-colour Ha image reveals a lot of structure too and is overall a bit sharper.
On one of three clear nights in February, I managed to capture this amazing image:
Messier 106 27/02/22
Just three hours of RGB data has captured a host of bright and many faint galaxies. Some of the faintest detected are very red indicating a huge distance away from us. PGC2299122 and PGC2299019 are estimated to be 3.8 Billion light years away!
Making the most of my improved guiding I have been using the big 250mm Newt to image some classic galaxies:
Messier 81 – Bode’s Galaxy 23/1/22
This is a combination of several partial sessions that I had to stop for one reason or another. 10hrs split as 4hrs of Red, 2 hrs of Green and Ha, and only 1hr of Blue! I’ve no idea how many frames were rejected – I left that to the WBB scripts.
I’d like to make the Holmberg IX dwarf galaxy a bit more prominent if I can (I have some Ha there but it’s very faint).
RBG 30s sub @ 0 Gain
Messier 82 – The Cigar Galaxy 25/2/22
For once my guiding was sub 0.5 arc-sec and conditions were great all night (even with gusts of wind) so I was able to capture all the data in one sessionš„³. This is 3hrs or RGB and 4hrs of Ha. On this occasion I used unity gain for RGB and 200 for Ha, I’ve decided that with so few good nights it makes sense and the noise isn’t excessive. I combined the Red channel as 80%Ha+20% Red to emphasize the disruption.Ā This is probably my best galaxy to date. Only my processing skills limit what my kit can produce.
In comparison here is a wide field image I took last year using my 150mm newt. There’s a lot wrong with the image but it shows the progress I am making.
Broadband imaging is already tricky in the suburbs but I perhaps didn’t help myself by trying to image this lovely galaxy with an almost full moon chasing it across the sky and haze. But still, for 4 hrs of data this RGBHa image is okay. The star field is aggressively clipped to remove the psychedelic rainbow mottling which I think is just pure moonlight.
For the rest of January, I had two more nights where I attempted to capture this target, luckily no moon glow just LP. So here is take 2, this time about 1 hr each of RGB and only 40mins of Ha. But you can easily see the improvement from by the better seeing and lack of moon – more fine details in the galaxy and lots of smaller galaxies sprinkled throughout the image.
Captured while waiting for M1 to clear some trees. This is an ideal target for a quick imaging session. 1.5hrs of RGB imaged with the ASI1600 on my 250mm Newtonian. Simple stacking a processing in Pixinsight. On this occasion I used a combined dark-flat with the flat frames This seems to work well.
I first imaged this supernova remnant back in 2005 using a modified web-cam.
I tried again is 2012 with a DSLR:
Picture saved with settings embedded.
I was very pleased with the results then but my recent efforts (Dec 2021) are significantly better as they should be given all the high-tech I have thrown at it:
It still needs more signal to get a decent SNR but the results so far are excellent given this is 1.5hrs RGB, 1hr for Ha and S2 and 2hrs for O3. By coincidence we have the same orientation for each image so a direct comparison is easy.
1 month later (6th Jan. 2022) with an additional 4.5 NB data and 45 minutes of RGB I was able to produce this version which uses only SHO data for the Crab nebula itself:
The narrowband light emitted by the nebula images very differently showing that the Crab has lots of very complex structure:
Combining Narrow Band signals to produce my Crab Nebula image.
This is a tricky target from my back yard, I only have about a 50-minute window between some trees to capture this. Imaged on a windy night the stars are not a great shape but I can live with that. This an Ha only image cropped and focused on the horsehead itself:
IC434 The horsehead nebula.
And here is the full frame:
Imaged using the ASI1600 on the OO250mm Newt, just 22 x 120sec Ha. Accidentally imaged at 0 gain! It’s tricky to get more data at this focal length due to the small window of opportunity so I’ll likely go portable for the classic a wider view with my short focal length refractor.
Messier 45, The Seven Sisters, The Pleiades Cluster
This is the bright 7-Sisters star cluster in Taurus visible high in the winter northern skies. This is a target that has been long on my list of failures – results have previously been poor with not having the right focal length and not taking enough sub-frames. It’s a broadband object so it is also at the mercy of light pollution.
Whilst the stars are bright the reflection nebula surrounding this cluster is quite faint and easily swamped. Bringing out the reflection nebula without saturating the stars requires choosing an exposure length that does not clip the stars and then take lots of exposures.
I decided that it was a good target for my un-modded, uncooled Canon 550D, matched to my 70mm APO refractor to give me a good level of detail with some surround star field for context. The result above took 479 x30sec exposures (4hrs). It was processed in Pixinsight and finished off in Paintshop Pro as a full frame resized to 30%. If I took another 4 or 8 hrs(!) I might be happy to display this at native resolution.
The HEQ5-Pro continues to be an excellent mount for this scope. Basically, its sub-arcsecond tracking accuracy with this load means it’s rare to lose a frame due to mount errors.
Earlier this year purchased a ZWO ASI1600mm Pro + 36mm 7-position filter-wheel complete with the LRGBNB filter set.
The ZWO filters represent very good value and I have had a lot of fun with them. However, of the set the Oiii is not the best performer, it produces distracting halos around bright stars and rings around dimmer ones.
I have learnt a technique to reduce the impact of halos during image processing but it is better not to have them in the first place if they can be avoided. Its asking a lot of budget filters so I had a look around, prepared to spend a lot more. But I noticed that the Baader filters had recently been updated with improved anti-reflection halo reducing layers (even claiming halo free). At Ā£143 from FLO they are a similar cost to the ZWO filters when bought individually. I decided to give the Baader filter a trial to see how it lived up to the claim.
I fitted both the Baader and ZWO Oiii filters to the filter wheel for a side-by-side comparison. The optical train was ASI1600mm Pro, Filter-wheel, Lacerta KomakorrF4, Orion Optics 250mm F4.8 Newtonian. Autofocusing between filter changes was done with a ZWO EAF.
The camera gain was set @ 139, sub-frames were 120s. I took 34 subs with the ZWO Oiii and selected the best 10 frames to stack. I took over 100 frames with the Baader. Using the same quality selection criteria I had 38 frames, from which I took the first 10 for stacking for this comparison. I used the N.I.N.A autofocus routine with each filter change. All subs were taken during the same one-night session. Conditions during the night varied but because I restarted a few times, the conditions evened out for the two filters.
To conduct the test, I chose a new target for me but one with a reasonably bright star in the ROI. I chose the Bubble Nebula. Below are the stacked images with automatic stretch applied:
ZWO 7nm Oiii Narrow Band Filter
ZWO 7nm Oiii 36mm filter
The ZWO filter gives us a very obvious halo around the bright star.
ZWO 7nm gives a bright halo after 20 minutes of integration
Baader 6.5nm Narrow Band OIII Filter – CMOS Optimised
Baader 6.5nm Oiii
The Baader filter also has a halo but it is very faint. Additionally, the star appears better defined suggesting less scatter overall. The fainter stars appear brighter than in the ZWO image. (More testing would be needed under stricter conditions to verify this).
Baader 6.5nm – Very dim halo after a 20-minute integration.
Baader 6.5nm – Even after 80 minutes integration the halo is still faint and remains fainter than the halo produced by the ZWO filter 20-minutes of integration.
Finally for comparison here is a closeup of the ZWO Ha subs (80 minutes integration). There is no halo apparent.
ZWO Ha 40 subs stacked. No halo to worry about.
Conclusion
The new Baader 6.5nm Oiii filter offers a significant improvement in halos over the ZWO 7nm. There are still halos present in my particular setup, but the Baader halo is over 4 times fainter that the ZWO.
There is also the suggestion of less light being scattered, giving brighter stars and better definition in distributed objects like galaxies and nebula.