So, an often discussed topic on online forums is what capture settings should I use, how much should I cool my CMOS camera, what exposure, and what gain. The answers to all these questions depend on your equipment and the amount of light pollution at your site. The following video was given at a recent Astronomy gathering by Dr Robin Glover, which gives a real insight into how far you should take the extreme possible settings of your equipment in order to optimise the gain in quality for the amount of pain and patience needed.
Towards the end of the video Dr Robin Glover ran out of time, but later posted the missing parts with relation to what gain settings are helpful in various set ups.
This is a quick video about “The Box”, the system I use that connects my equipment (via INDI), to my desktop indoors, and allows me to control everything without having to go outside. Although it is sometimes enjoyable to go outside and watch some of the automation tasks, such as a meridian flip!
During the focus procedure on Friday night, I seem to have captured what I’m going to call “Musk Trails”. I expect this was part of a constellation of SpaceX Starlink satellites traversing my field of view while I was trying to focus. Here is a still from the video:
So, I did make a screen capture of the session on the 9th October, it is not particularly interesting as I was not really commentating throughout, had my webcam flap down for some reason, but you will see certain aspects – we are using the new SEP multi-star algorithm in Ekos, which is great for stability, it does show off the AS290MM mini, it shows how I have to manually focus every so often (APO and SestoSenso arriving soon will be greatly appreciated).
I would not expect anyone to watch this five hour marathon through from start to end, although if you happened to be watching it live it might be interesting if you were acquiring the same target, but certainly skipping through the footage, you might come across something I’m doing wrong, or right, and have some comments on my progress in this field.
Don’t expect so see the thumbnail in this video to appear in the video itself, this is the acquisition phase of individual sub-exposures, I will post a video on processing of the data, including this night’s, in a later video, when we’ve hopefully improve on the data substantially. The preview picture displayed is the accumulation of data so far, without any discarding of bad data so far.
I do have to wonder, how I will proceed when the APO arrives, it is a f/7 telescope, while these are taken on a f/5 telescope. Maybe I can proceed with a 3×3 mosaic, or something similar 3×2 or 2×3 and add to the data, or perhaps I need to choose to start all over again. APP will help when I start, as it will quantify the quality of the images I already have, and be able to merge frames from different optical equipment.
As always, if you are here as a genuine viewer with an interest in Astrophotography, then please leave a comment, I will moderate and reply if necessary.
So last night, we obtained some more Oiii sub-exposures in order to bring the number to the same level as our Hydrogen Alpha sub-exposures. I also started to obtain some Sii exposures, only managed 10 or so for each pane of the mosaic. It looks like I should obtain more Hydrogen Alpha sub exposures as well now, as the quality does not appear to be as good as the other narrow-band wavelengths, and of course Hydrogen Alpha is a strong part of the composition. You will notice we are now using a different palette for the RGB composition. I probably need to flex up some of my GIMP processing skills as I still feel I am floundering around not really knowing what I am doing. Anyway, without further ado, please find below the current rendition:
So I managed to get some extra frames for the Heart Nebula.
I’m now working with around 190 individual frames, so my registration and integration process is changing, as rather than just load all the frames and tell APP to work on them, the DDC is taking an inordinate amount of time, and I suspect that this also affects other processing later on.
So, now, we load each pane of the mosaic, and integrate them separately using a normal registration process. After which we then do a single mosaic registration and integration with the eight panes, 4 per channel of Ha and OIII.
Here are the results:
We can see here, how the detail comes, and aberrations recede as we add more data. Below, upper image is the intermediate, while the lower image is the original initial data acquired.
Thought I would rework the data of the Heart Nebula IC1805, I have managed to obtain some darks and bias frames. So I loaded everything into Astro Pixel Processor and started the registration and integration process. I’ve now discovered that there must have been some alignment issues during capture as there is a distinct rotation artefact in the top left frame. Still, this one has more contrast, and we can see more detail than before.
Well, a rumour going around that there is life on Venus.
There will be an online press conference at 15:00 GMT (16:00 BST), but it amounts to measurements of levels of phosphine (PH3) being far too high in the region of potentially habitable space in Venus’ atmosphere. Levels far too high, to have been produced via chemical processes. Or so the scientists say – remember the cold fusion thing in the eighties?
Although this video has already appeared, and the videos below are what should go live at 16:00 BST.
Now my ASI120MC-S is no longer my guide camera, I mounted it on a ordinary camera tripod and tried a few All Sky exposures. Because we’re not tracking or even aligned the result isn’t great quality, but you can make out an arm of the milky way.
So, at last the ASI290MM mini & Helical Focuser have arrived. This will hopefully be a significant improvement to guiding.
But first, some backstory.
Back when I went and got my main imaging camera, the ASI1600MM Pro, I bought the set of the 8-slot Filterwheel, all the filters (L,R,B,G,Ha,OIII,SII) and an Off-Axis-Guider (OAG). I was looking for a reasonable guide camera to attach to the OAG. The long list of equipment for the imaging train meant that my budget was somewhat limited. I chose the ASI120MC-S.
Really, the ASI120MC-S does guide quite well, but it is not entirely suited to the task. Firstly it is a colour planetary camera. Colour is not necessarily of any use when guiding, and might even hinder it for all I know, but at the time, completely new to astrophotography (and not really experienced now!). I thought, well, it will probably work for guiding, and I might be able to use it for other things too. In any case that’s what I got, and it has served me well for guiding.
Recently I’ve been looking to see whether I could get some improvement in this area, and eventually decided that the ASI290MM mini might suit pretty well.
Let’s look at some comparisons from the graphics at the ZWO website. First, the ASI120MC-S
Now, the ASI290MM mini:
OK, so the sensor on the ASI290MM is bigger, but so is the resolution, the pixel size on the 120 is 3.75 um, the specs don’t highlight that on the ASI290MM, but I believe the pixel size on that is 2.9 um. The read noise on the ASI290MM is a lot lower, also note that on the mini it is USB2.0 rather than USB3.0, which probably counts for why the frame rate on the AS120MC-S is higher. It is difficult to compare QE between the two, the MM mini slightly higher.
Clearly with the ASi120MC-S having a full well 13000, capable of higher frame rates, seem to lean that this is a camera meant for planetary imaging, which can do guiding, whereas the ASI290MM mini is a guide camerea, that you might be able to do some mono planetary imaging. So the mini is squarely aimed at guiders, and I hope it will excel at first light.
The areas where the ASI120MC-S excels at better than the ASI290MM mini are not significant for guiding, and the areas where the ASI290MM is better (lower read-noise, more pixels, lower pixel size) are all areas which should improve guiding, hopefully allowing me to reduce exposure times and cope with the small amount of light pollution I sometimes have.
Here are some pictures of the imaging train:
So I had my first outing with using the ASI290MM mini as a guide camera last night. I can confirm that the camera behaves as a distinct step up when compared against the ASI120MC-S. Firstly, with exposures set to 1s and binning set to 2×2 I was able to constantly guide without losing a star for quite a few hours, and the only times I lost guiding was when I attempted more aggressive settings. The frame acquisitions during guiding showed considerably less noise, and it should be noted that I was guiding without any dark or calibration frames. The helical focuser was great as well, I was able to quickly use ASICAP on my Tablet to ensure that the guide camera became parfocal with the main imaging camera. It literally just took a few seconds, and the position was easily locked into place with the thumbscrew. My experience of trying to use the adjustments on the OAG previously had led to a lot of frustration messing about with Alan keys in the dark trying to achieve some sort of focus. The clamp on the helical focuser also allows for rotating the guide camera to ensure that it is somewhat aligned properly with the mirror and/or the main camera. I’m of the opinion that with time, and the upcoming upgrades to OTA and focusing I will routinely be achieving sub-arcsecond guiding.
I’m gearing up for a new season, we have some pretty poor autumnal weather here at the moment, and very few clear skies forecast for quite a few days.
However, I have placed an order for the following new equipment:
A SkyWatcher Esprit 120ED Pro Triplet Apochromatic Refractor. This is to replace my achromatic SkyWatcher Startravel 120T. Unfortunately there is a long leadtime on these to arrive from China, so it might not be until November that we see first-light with it.
A Field Flattener purpose made for the above, to ensure better astrophotography results.
An Astro Essentials Filter Cell Adapter, which should allow me to fit a light pollution suppression filter between the field flattener and the focuser on the Esprit.
An IDAS P2 Light Pollution Suppression Filter to be used in the above (2″).
A Primaluce Lab Sesto Senso V2, this is a a stepper motor to replace the HitecAstro DC motor, it should be more accurate with less slippage, although going with an Apo should mean I have to spend less time refocusing during filter changes.
A Temperature sensor for the Above.
A 17ah Powertank – I will be trying to power all my kit from a battery this year, in preparation to see if travelling to a dark-skies site could be possible.
I suspect that this means that I will soon put the StarTravel 120T, with its focus motor and HitecAstro DC unit on the second hand market, it will come with a fabric carrying case as well, and I may be able to throw in a few extra accessories.
Of course, it all depends on when the above will arrive, which is forecast to be around 10-12 weeks at the moment.
I’ve also gone to place an order for the following now:
ZWO ASI 290MM mini USB2 mono camera for guiding
ZWO 1.25″ Helical Focuser for the above
On briefly attempting to guide with my ASI120MC-S at the weekend, I was reminded how noisy a camera it can be, and unfortunately, while I bought it for guiding I kind of let myself be lent to a possibility of doing planetary imaging, which it is probably more suited to. The ASI290MM should be a better dedicated guiding camera, and I hope the helical focuser will allow focusing off the off-axis-guider easier.
Still a work in progress, will probably work on some other channels to add.
I’ve not uploaded the video of processing the mosaic as it was necessary to use a downgraded version of the software due to bug in the current version, I had that version on my laptop, so I used that to stack the mosaic, but don’t have Video recording software I know how to use on the laptop.
Will re-do when there are more sub-exposures available, and the bug in the software is fixed.
This is an example of processing data of the Andromeda Galaxy, with Astro Pixel Processor. The data was obtained from the Internet, rather than captured with my equipment (cloudy and windy the last few nights).
There are some other targets available there, I’ve seen some other processed data and the nebulae are quite astonishing.
An issue I have with using practice data, is that often the data is just too perfect, otherwise it won’t have found its way on to the Internet. It sometimes is more instructive to try and process bad data and make something good of it rather than process just good data.
So, another cloudless night, how lucky we are. Disappointed with the results of two nights ago, I revisited the Soul Nebula, and this time get somewhat better quality in places that were disappointing. Here are the new results.
I may try and join the two sessions together and see whether I can pull any more detail from the two.
So. Now what we are able to do, if merge the results from Monday evening with the results from Wednesday and build a composite mosaic, I fiddled with the colour palette to bring out the detail. We can continue to add exposures and the mosaic would eventually lose the noticeable borders.
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