BrendanC

I guess so, I was just surprised that one particular dust cloud seemed so definitely to emanate from M51.

Yep, checked out that image too. I have no idea what it could be. I guess I could go through the subs, say, every half hour or so, and if it's persistent then it isn't clouds. Don't know what the 'background noise' could be? It's a definite structure.

Bortle 4 skies, not very much light pollution. It was shot broadband, which is why I was surprised something would appear in what seems to be O3. I can't really give it another shot elsewhere because my rig is static.

Hi all, I recently imaged M51. On using the range selector tool in PixInsight, I could see that there was a large structure fanning out from the object, mostly in the green channel. I thought it was a problem with calibration or light pollution, but the more I looked and played around with the data, the more I became convinced it was an actual thing. So, I stretched it out a bit more, and here it is - the green cloud going to the top right corner. My question is: what is this? I haven't seen it in any other images. If I've discovered it I'm going to call it Cooper's Cone or something. Any takers? Thanks Brendan

Looks like separate items it is, then. I agree, unless someone wants this exact setup it might take a while to sell, and I don't want too much delay. Thanks!

Hi all, I'm moving back to London soon, and won't have much sky to enjoy. Also, after four and a bit years of enjoying astro, I find the balance between enjoyment and frustration has tipped the wrong way, especially with our diabolical weather. So, I'm thinking of selling my stuff, but I'm not sure what the best thing would be to do. I can see that it makes sense to break the system down and sell it in bits. It's nothing special, just a 130PDS scope with focuser and guidescope, NEQ6 mount, ASI533MC camera with some filters, Nevada power supply. However, I can also see that as it's all working nicely, it's essentially an 'observatory in a box', so someone could just take it in toto, download drivers to their computer, plug it in and off they go. If they use APT, I could even supply them with the settings. The 'break it down' approach would mean a bit of faffing to dismantle the focuser, put the knobs back on the scope, advertise etc, but would probably be the quickest route. The 'observatory in a box' approach would give me a nice warm feeling inside because I'd be helping someone get set up quickly, but I can see that if someone is just starting out, and wants to get into this game, adopting a complete system in one go rather than starting simple and building up might be a bit of a challenge. Also, I haven't really seen anyone else do this, which implies to me it's not 'done'. So, what would you do? Any ideas/thoughts/opinions? Thanks Brendan

Hi all, While the weather in the UK continues to stink, I've decided to hone my PI processing skills (or lack thereof). I never really got the hang of adding Ha from a OSC dualband image for nebulosity, to an OSC RGB image, especially with galaxies, and especially with M101. What I tend to find is: When extracting the stars from the Ha image (using StarXTerminator now, but even back when I used StarNet), it pulls out some of the nebulosity too, because it recognises them as stars, and I can't figure out how to get it back, or stop this from happening in the first place. When combining the Ha with the RGB, I get a red cast from the Ha across the entire image. So I'm looking for ways to extract just the stars from the Ha image, while preserving all of the nebulosity (or, how to put it back in); and how best to combine the Ha starless with the RGB starless (and then I apply the RGB stars via PixelMath, which isn't a problem). I've tried several methods, from extracting the channels and recombining the Ha as red, also using an HaRGB script I came across on the Visible Dark YT channel, also various masking techniques - again, including one from Visible Dark where you use the Ha image as a mask - but nothing quite seems right. I seem to get too much Ha, so it's all a wash of red or purple and loses that lovely blue hue; or not enough, where it's almost as if there's no pronounced Ha nebulosity in the image at all. Does anyone know of a good workflow that will help with this? Or, ideally, a nice video that walks me through it? Thanks Brendan

Interesting. Thank you both again for your help. I'll try the flats test and I'll give the 1.25 inch filter another go but at the end of the day, since I had no problems with my 2 inch filter, if that just works then I'll go back to that, keep calm, and carry on.

I've just been going through my old flats and they all have it too. I recently installed the Backyard Universe secondary spider, and before and after that, I can still see ghost views of the central obstruction. I guess that no matter what is being captured in a flat, it should be calibrating out what's in a light. Which leads me back to your test for things shifting when taking flats.

That's no moon... Right. So, is this a light leak?

Sure, here you go - really stretched master flat (actually taken from the GHS preview cos I think it displays in fewer bits and shows off the artefacts better). I can see what you're saying (literally) - the two circles do look somewhat like what you'd expect to see when looking down the OTA, complete with a bit of secondary spider for good measure. and therefore could be reflections.

Thank you for the input Olly. I've tried reading this several times and I still don't quite understand it: "Could the bright flats-equivalent of the dark patches on the calibrated image be reflections created by some part of the light path illuminated by the panel?" I'm wondering whether it's reflections too. This is from a 130PDS Newtonian.

Wow. Perfect demonstration there. Thank you again.

Absolute superstar - thank you so much for taking the time to do this, as ever I really appreciate it. As you say, the difference in focus positions shouldn't be drastic, as focus changes throughout the night. I refocus every hour. It's a strange one. Here's a super stretch of another cluster I took the same night. I think I can just about make out similar artefacts in this one, but they're very indistinct. So clearly something happened between that one, and this one. I'm wondering if it's a combination of factors: The M67 data was collected at the very end of astro night (and in fact going about 15 minutes beyond), and at that time, it was pointing at a house nearby. I think they might have had a light on all night, without curtains, so the scope was pointing almost directly at that light. This could have affected things in some way, with lots of light bouncing around. There were certainly strong gradients in the subs, as you probably noticed. I recently removed the flocking from my scope because it was coming away. So, if there was lots of light bouncing around in the OTA, the lack of flocking might have exacerbated it. There may have been dew. It wasn't forecast, but when I brought the scope in later that day, the primary was dewy, and I had to discard almost half of the subs but I assumed that was because of cloud, not dew. So, the subs may not have matched the flats because of this. So, I wonder whether these, combined, have just created a unique set of circumstances. Thing is, wouldn't you know it, they happened on the same night I was testing a new filter. Anyway I will definitely do your test. When I do the pixel math, will it really just be a simple expression of zenith flat / horizontal flat? And it should yield a flat image with no details at all? Thanks again, you've already been very helpful.

Interesting test, I'll give that a go when I get the chance.