The Admiral

Last night, after a very turbulent day weather-wise, I unexpectedly spotted Mercury just before it dropped behind some cloud. I grabbed my camera and got this rather poor quality shot, but at least it's a record. All from an upstairs bedroom through double glazing. The previous night (Monday 10th) gave a much better viewing, but I didn't have my camera to hand. The forecast isn't looking good for this week, but I need to be better prepared . Mercury is well placed this month, with the greatest elongation on 17th May, with nice conjunctions later in the month with the Moon and Venus. Ian

Lovely videos. Beautiful scenery seen from an ideal perspective. Ian

Perhaps I'm being a bit dense here, but won't the output levels from either camera be influenced by their respective gains or ISO setting. How do you take that into consideration? The CR2 raw can surely still be linear data, even if there has been a lot of gain applied from using a high ISO? Ian

As Peter Drew suggested, the TTS-160. Not far off your weight requirement. But it isn't cheap 😉. https://trackthestars.com/tts-160-panther-telescope-mount/ Ian

And still you keep producing them 😉. Another lovely shot revealing a beautiful, normally invisible, nebscape. Ian

I don't find any of them good at predicting, and in some cases, even agreeing with what the conditions are currently! I think the best you can do is to look at satellite views of the clouds, though that doesn't help deciding whether to set up in advance. The weather in the UK is very complicated and notoriously difficult to predict, and different weather models usually give widely differing results. See for example https://www.meteoblue.com/en/weather/forecast/multimodelensemble/oxford_united-kingdom_2640729 Ian

Just be aware that some (latex) gloves are powdered on the inside to aid getting on and off, if I understand correctly, so using this type risks introducing dust. Choose a powder free variety. Ian

Well done to the winners, and all the authors of the many and varied submisions who all made the competition interesting. Not just a processing challenge, but a judging one too! Ian

What caught my eye was how tiny the bright stars appear in this image. Or am I imagining it? A lovely image as usual Göran. Ian

I'm just an interested by-stander on the ASI294MC pro issue that you are getting, and it would be nice to get to the root of the problem. For information, when you say 'using a white T-shirt', was this a single layer or double layer of material? I'm asking because its appearance is to my mind like Moire fringing, which you could get if two layers of cloth are together but one is stretched a little more than the other, so that the 'thread density' (my term!) is slightly different. Possibly also, the thread count of the material might be very similar to the density of the light emitting pixels of the flat aid, so you could be getting moire fringing between the fabric and the light source. All very much complete stabs in the dark here, but you never know . What puzzles me though, is that this is not revealed by the stretched flat. Do the flats from your original look any different from the flats taken without the T-shirt? Care to elaborate on the 'other issues'? Did you get around to stacking with Siril? Your latest image looks very nice by the way, I hope that you have found a way forward. Ian Edit. Hmm, but then you found that stacking just the darks and lights together gave you the same result. Have you checked every sub to see if anything is visible? No overhead cables to get in the way? I've got several here and I've found it's easy to try to image through one .

Ha-ha, what a doughnut! That's what happens when one gets old . Thanks for the heads up, I'm glad someone is on the ball! Ian

It's not the first time I've read about issues with this camera, nothing very consistent though. In this thread a particular issue is raised. Now the effects are quite different to what you are finding, but Vlaiv raised an issue with APT in his post on 26 March where he thought that APT wasn't working properly. So clutching at straws, it might be worth checking it out. Sorry if this is a red herring. Ian

So, it's not visible in the darks, it's not visible in the flats, and it's not visible in the subs! In which case, could it be something in the way that DSS is doing the calibration, registration, and stacking? What else could it be? What software did you use to capture the files? At what temperature(s) did you take the files? All the same? I don't suppose you have an alternative means of stacking to test it do you? Otherwise, I wonder if you are able to upload all the files so that others could have a tinker? Ian

DSS will rotate images to align them, but with Alt-Az imaging, stacking aside, the rotation that takes place during each exposure becomes sufficient to be visible on every image if the exposure duration gets too long. It's unavoidable I'm afraid. Think of it as a mild form of star trail images. It means that detail will be smeared and definition will be lost, even at the centre. Field rotation is at a minimum towards the West and East, and becomes large towards the zenith. Here is a good description https://calgary.rasc.ca/field_rotation.htm Ian

Stuart, if you are doing Alt-Az imaging might I suggest that you have a look at the (rather long) thread dedicated to such imaging (if you haven't already)? There you'll get a feel for what to expect and what can be achieved. Whatever scope or focal length you use, you will be limited to short exposures in order to avoid field rotation, so anything you can do to maximize the number of photons captured and signal to noise ratio the better. A lower f-ratio could help; you could think about a reducer for your SCT which will bring it down to f/6.3. The other thing that you'll need to do is to capture a lot of subs for stacking, and I mean, a lot. When I imaged M51 with an f/7 102m refractor, I used 200 x 30s subs , and even then the results were not exactly overwhelming (https://stargazerslounge.com/gallery/image/30726-m51/). Also, as Vlaiv pointed out, with the focal length you are using, light from an object is spreading over too many pixels so that the noise from each pixel tends to overwhelm the signal. By 'binning' data it means treating several pixels together as a block so as to improve the signal to noise ratio. With your DSLR you can only do this is software. Ian

Yes, I image at ~ 560mm, and there's no doubt that the longer the FL the more difficult things become. I use it with a 50mm, 200mm fl guide scope and so far have just used the 'one push' mode! The new model uses a later camera and can (or supposedly, will) be able to be controlled by software using ASCOM, allowing it to provide dithering with an astro camera. It can be remotely controlled as well as working in stand-alone mode. What's not to like, apart from the price . Ian

Nice one! There is an astonishing colour range isn't there, it must be quite gratifying to get that in an image. There must be vast amounts of such dust around, so I think you've got several year's work ahead of you yet 😉 Ian

I've read that too, but it has left me wondering whether this just applies to the mono version. I don't see how that can be compatible with a Bayer array of the OSC version. Perhaps a 294MC user can confirm? DOH! Why didn't I read your reply properly 😀. Ian

I have recently bought the MGEN III, but I'd not previously used guiding so I'm not in a position to judge how good it is. However, for the few times I've used it I have been quite happy. What is it that makes your friend think it is not as good as v.II ? I'd be surprised if the earlier version is still available. Ian

Sorry to hear that. Ian

I've read something about flats issues with the 294. Whether this is a similar thing I wouldn't like to say, but I suggest you Goggle "flats and ASI294MC Pro", and you'll find threads which might be pertinent. Apart from flat non-uniformities with filters, flat exposure time seems to be important too I believe. It's just a thought, but I'd be interested in the outcome. Good luck. Ian

And it's all your fault John . I must say that I found the thread reassuring and it was helpful to have the support of others whilst I honed my skills. Ian

Well, let me add another then . The itch needed scratching I'm afraid . I rather felt that my previous attempt was somewhat too blue, so I took the output back into Lightroom and began moving sliders around. Principally I made a white balance shift towards the warm, reduced brightness a tad, and played with the HSL sliders, beefing up the red in particular. Changed the cropping a little too. May be it would be better to play more in the primary fits processing rather than with the final tiff, but hey ho. Just one of an infinity of possible variations, as we are seeing by all the responses so far! Call it a day now I think! Ian

Oh what the heck! Might as well have a go, even though I've only processed OSC colour data before. I tried to use Affinity Photo (totally new to me and had to give up). This is the result of using APP which I've only recently become acquainted with. Combined with the 'Combine RGB' tool, using just 13% Ha, did a background calibration and calibrated star colours, and then final tweak in Lightroom to reduce the brightness a tad, adjust the black point, add some clarity, sharpen a little and some gentle luminance noise reduction. Ian

Yes, I noticed Ivo had posted above saying that he had written on how to combine the data on the ST forum. Ian