ollypenrice

That green glow... I bet you could be persuaded... These are great galaxies. Olly

It's very good and the colour is far more accurate than the bright blue spirals which we often see with M101. The core is saturated in the first one and still saturated, though less so, in the second. The first thing I'd want to do is look at the core in the linear data. Is that saturated? If it isn't, there is no need for it to become saturated during the stretch. You just need a better stretch, or a blending of two stretches. Maybe just a hand-shaped stretch in Curves would do it. What does the linear core look like? Olly

For me, this image didn't seem exceptional until I clicked for the largest size - and then I found that the central bulge and dust lane were absolutely stunning. Unfortunately the last one seems to have been posted at lower resolution, or am I giving it the wrong clicks? It needs to be seen in large format to show its class. What I do think is that the fainter outer regions are noisy, with a pronounced grain. I'm sure Russ Croman's Noise Xterminator would fix that easily and might allow you to give the lower brightnesses a bit more of a stretch. I wouldn't apply it to the brighter parts or dust lane. Those are superb. Olly

Ultra-promising. Olly

Interesting. This is the blue channel from our OSC camera. I'd probably vote for reflection, but who knows? Olly

The answer is 'yes.' This is a mosaic combining 42 individual images. I can't tell you how to do it in five minutes, though! lly

Look at that tail! Go for it!! Olly

Is it OIII or blue reflection? Olly

Very hard for imagers to capture the globular sparkle but you have it for sure. Great image. Olly

How well will it hold focus, do you think? Olly

That looks very promising. Olly

Ah yes, perhaps the OP is talking about a field de-rotator for long exposure alt-az imaging? I would just say 'Don't.' Don't throw money at de-rotators or wedges, just buy a proper equatorial mount. I'm not sure that there is any guiding sytem for alt-az de-rotated mounts, at least for amateurs. Olly

Preprocessing, APP. Post processing, a bit in Pixinsight and a lot in Photoshop. I also use Registar, particularly for composite (multi-scope) images. I consider StarXterminator and NoiseXterminator to be absolutely essential. Olly

One scope cannot do everything and a good beginner visual setup is likely to be totally different from a good beginner photographic one. Narrow down your objectives and priorities. Olly

So it looks as if the camera itself is very slightly vignetted. I've never tried this experiment so I don't know how my cameras would behave. To be honest, I don't see it mattering because the variation is minor and this vignetting will find its way into the final flats (shot through the optics) anyway. By the way, you posted some ABE-processed images earlier. What we see in them is a common ABE fault which regularly affects galaxy images. ABE puts background sky markers too close to the galaxy (or roundish nebula in your case) and treats faint outer glow as background sky. When applied, it lowers the pixel values close to the object and creates a dark region around it. I only use ABE when there is really no workable way to identify background sky anywhere in the image, as often happens in very deep stacks. Olly

I've no experience of motorized rotators but find myself wondering why you might want one. I only ever shoot with the chip sides parallel with RA and Dec, so that's a choice between landscape and portrait. Why do I do this? Because, if I want to go back at some later stage and add more data, I can do so very easily. I discovered that reproducing an arbitrary angle is a bit of a nightmare. I find that this hardly ever has any consequences for framing and it avoids complications with flats and makes troubleshooting easier. (Guiding, tilt adjustment, etc.) Olly

I moved from Derbyshire to a deliberately-chosen dark site in the part of France identified as the best by professional astronomers' site-surveys going back to the thirties. I wouldn't know where to start, really, in making a comparison. In Derbyshire I never saw M101 at all. Here I see it in a budget finderscope. I could never see the Rosette, with or without filter. Here I can see it either way in anything between binoculars and a 20 inch. I've seen the Gegenshein, naked eye, here but, on the other hand, I've never seen M33 unaided. While both visual and photographic astronomy are outstanding, here, they both take second place to the simple fact of living under an unpolluted sky. Even if we're just driving back from a restaurant, or I'm nipping out to fetch some firewood, the night is night, it's dark and starry. It feels like the difference between breathing exhaust fumes and oxygen. Olly

Fascinating stuff. The Samyang-RASA is a demon pairing for combining widefield and high res. Do you combine them in a starless state? I tend to do this then apply Samyang-only stars for consistency. Olly

Lovely clean result. Olly

OK, thanks for the encouragement! I tried again to exploit the TEC data in the inner galaxy and came up with the image below. To my surprise it was easy to upsample the RASA image to the scale needed for the TEC resolution to show. Full size is here: https://ollypenrice.smugmug.com/Other/Galaxies/i-psSP6gB/A Olly

This is just what tried to do and have done many times before, but I haven't yet managed to make it work this time. In fact, scaled to fit the RASA image, there is not all that much more resolution in the TEC than the RASA. If I were to rescale in the other direction, making the RASA image larger, I'd be lifting the noise in the RASA and it's already on the ragged edge of the possible stretch. It doesn't help that the TEC field of view stops short of the upper spiral arm. If I can come up with any new ways of making the composite I'll give them a try. The obvious solution would be a RASA 14.... If the people would like to give Olly one, he'd be most willing to accept it! 👌 Olly Edit: there is another problem, too. The TEC's resolution requires dynamic range, ie contrasts within the central spiral arms. In the ultra-deep RASA image a lot of the lower dynamic range has been used by the faint outer streams so the dark stuff in the central spiral is brighter and can't be as contrasty. I'd be in danger of having the tidal streams brighter than the dark regions between the bright spiral and, in reality, they are not.

You should be able to get far more of the long tidal tail to show, though it will run out of the frame on this crop, I think. It will be there in the data. If you have Photoshop, just go to Image-Adjustments-Equalize and it should leap out. You can't just use that as a processing technique but it will show what you have in the data. Olly

You wouldn't go far wrong with this, on the astrophotography side. https://www.firstlightoptics.com/books/making-every-photon-count-steve-richards.html Like most things in life, DSLR photography is best approached by thinking things through from the basics. There are really not so many of those and this is, for me, the big one: Understanding F stops and light cones. https://www.dpreview.com/forums/post/63155522 When a lens is wide open it lets in more light and therefore shortens exposure time, freezing fast action, but the steep light cone has a shallow depth of field meaning only selected parts of the image can be in focus. This can be good or bad, depending on the photographer's intentions. A stopped down lens has a greater depth of field but lets in less light and, therefore, needs longer exposure - which can introduce motion blur. If you were to go out with a basic DSLR and experiment with this single set of related parameters, and really get the feel for them and how they play out, you'd be self-educating very effectively, I think, and would have a grounding for further learning. For land and sky photography, check out the free Sequator software. https://www.startools.org/links--tutorials/free-image-stacking-solutions/sequator On image processing and U-tube tutorials, the instant you hear the presenter say, 'I just play with the sliders till I like what I see,' turn them off and never go back to them! Most astrophotographers are autodidacts and the best ones are the best because they seek to understand before they act. Olly

Just for info, an all-new RASA 8 image has gone much deeper than this. Olly

A deep dive with Paul Kummer (capture and pre-processing.) This had 9 hours in the RASA 8, equivalent to about 40 hours in a fast refractor of comparable focal length. After 3 hours we were going well but 9 hours brought out more structure and, of particular interest, the uppermost spiral arm winding anticlockwise in this orientation. This arm is a new one to me and was an exciting find in the processing. Edit: please scroll down for a version using TEC140 data to enhance the core. This is a close crop and is presented at one-to-one here: https://ollypenrice.smugmug.com/Other/Galaxies/i-sgC3bGn/A Olly