ollypenrice

I think our wires are crossed! (Probably my fault.) I was talking about the resizing and aligning of the high res over widefield which I understood you to be doing in Photoshop when you said, 'I first resized (reduced) the high resolution image in PS (I usually do it by measuring the distance (in pixels) between the same two stars in the images to calculate a reduction factor). I then just did a star alignment in PI using the RASA image as template. Then I added it as a layer to the RASA image and used the dreaded brush too to let about 50% through on the nebula.' When you do this in PI does it re-curve the high res to match the widefield? On small regions this might not be an issue but therre will be different field curvature in the two images, something which Registar adjusts. When Rodd contacted the PI developers about including a facility for resizing and aligning high res for inclusion on widefield they replied by insisting that this was 'painting,' and not something they'd get involved in. Since neither image is 'painted' I fail to see why they should say this. Olly

Although it's not cheap, Registar would do this job in a couple of clicks and do it infallibly. If you're going to do a lot of composite imaging I think it would be worth it. I don't combine the component images in Registar for the reasons implicit in your workflow. I do it in Photoshop so I can feather in the high res gradually and control the opacity of the blend. https://aurigaimaging.com/ Splendid M45. Olly

Just seen this. Super! Olly

Ooh yes, much nicer. Well blended. (What did you use? The PI Inquisitors regard this as 'painting.') What continues to impress me (and make me curious) is the level of contrast between brown dust and background sky. I would say that I have as much signal in mine but the contrast, particularly in distinguishing brown from dark background blue, is far less. Olly

No pain at all! That's what the forum is for. Olly

Yes. If the telescopes have the same focal length but one has a faster F ratio it must, by definition, have a larger objective. And that alone is why it catches more light and gives faster exposures. The reason F ratio becomes contentious and confusing in astrophotography is that it is also possible to change a telescope's F ratio by using a focal reducer. In this case the aperture has not been increased so there are no new photons. (The photons which there are, however, are concentrated onto fewer pixels, trading resolution for speed.) Olly

No problem. In the yellow box you see four sections, 1,2,3 and 4. Each one refers to a sample point. The brightness values for each channel, R,G and B have two values next to them. The first one, identified in red, is the present value. When you open a tool which can change the present values, as you have done with the Colour Balance tool, a second figure appears to the right of the present value. That's the new value, highlighted in green, which will show you what the tool does as you adjust it. In the screen grab below, the Colour Balance sliders are all at zero so the new and old values in the info window are the same. Move the sliders, though, and the new values will change in real time. You can see in boxes 1 and 3 that the blues are much higher than the rest. I think you'd do better to stretch the image rather more before looking into the colour balance. At some point you are going to want to acquire a gradient-removing tool. Gradient Xterminator is a good plug-in tool for Photoshop. Personally I use Dynamic Background Extraction in Pixinsight. AstroArt also has a gradient remover, as does Astro Pixel Processor. A gradient is just a gradual drift in brghtness across an image. You'll get them even from very dark sites. Olly

Where do the extra photons come from? When you choose a faster setting you are opening the diaphragm to create more aperture. Olly

In imaging there is no single step which is difficult. The difficulty arises from the fact that there are so many small steps! Olly

Yes, but I read 7.8 hours at f/2 corresponds theoretically to 96 hours af f/7 as a statement making no reference to pixel size. If it is a statement in which we are to consider pixel size as a constant then that's another matter. Olly

Surely focal length is only half the story. The other half is pixel size, since resolution derives from focal length and pixel size. What matters is your resolution in arcseconds per pîxel, not your focal length. These images were shot at 0.89"PP using a guidescope (ST80 with Lodestar Mk 1.) https://www.astrobin.com/419975/?nc=user https://www.astrobin.com/393219/?nc=user https://www.astrobin.com/335042/?image_list_page=2&nc=&nce= I really don't know what problem anyone is trying to solve with a guidescope and a refractor. Once you move to a reflector the need to avoid pinching the mirror does argue in favour of an OAG which will 'see' mirror movement. Olly

Shows what you can do. Be encouraged! Olly

The problem for me with the rule about not being able to increase surface brightness (which I'm not disputing) is that it carries with it the risk of suggesting that you can't see fainter objects in a larger telescope. Olly

In Photoshop you can go to the Eyedropper menu and select the Colour Sampler Tool. In the top bar you can then choose 3x3 average as a sample size. This lets you put 4 sample points on the background and the readings appear in the info box. I like to get the background equal in all three channels with a brightness of 22 or 23 ideally. One way to adjust is to use the colour balance tool set to shadows. Olly

Yes, I too find that enough is enough! 😁lly

Bon appétit!!! I like the high contrasts in the dust and wouldn't hesitate to blend in high res Iris. That's exactly what I did. Olly

I think your orientation is north-down? Is that right? (No reason why it shouldn't be!) What struck me about this image, which is a very striking one, is the intensity of the contrasts. The background sky is held down and the reflecting and scattering dust is relatively bright, which emphasizes the shapes in the dusty structures. It really is very forceful and impressive in that way. The blue components in the Iris also extend more widely than we usually see. Both the imaging system and the processing have, I think, brought something new to the target. I have a couple of reservations, which I only mention because this is such a memorable image. The resolution into the core of the Iris could be better at this image scale. The progenitor star is saturating the area around it. And there are some faint pinks near the core, probably from Ha, which we are not seeing. What I take away from this image, and what I don't know how you achieved, is the intensity of contrast in the low brightness regions. That is spectacular. Now you know what I'm going to say to that! 🤣 How did the photons entering your objective know the focal length of the system that followed? What matters is aperture and pixel size. F ratio is hot air. You proved this with your Liverpool Telescope images! Olly

They do appear from time to time. Don't despair. Both halves of our dual rig arrived from the used market. Olly

I think it's a very good idea. Things stay much drier. I tend to use the hard sheets of roof and wall insulation like Celotex, or whatever equivalent they have in the builders' yard. I certainly start with the roof, which I think is the most important part. If you don't insulate the roof but do insulate the walls you'll drive all the condensation onto the roof where it will drip down. Another good thing is to have plenty of ventilation. That also resists condensation. Olly

You might want to make notes on steps in your chosen software, too. These are specific to the packages you use but many of them have little traps to avoid. Classics are to restore full frame capture after subframe focusing and to autosave all captures! If you use a Bahtinov mask to focus (a good idea) remember to take it off for the imaging run! Not that I'd make any of these mistakes, of course... 🤪 Olly Oh, another thing: set your camera along RA and Dec, not at a random angle. Your camera has a round body so mark it on the rear (eg with tape or permanent marker) to show the orientation of the chip. When you put it in the scope make that line parallel with the dovetail or at right angles to it. Two main reasons: it's easier to come back to the target and add more data if the camera is at a repeatable angle and you know which axis is misbehaving if you have a guiding-tracking issue.

Yes. Your camera has a 'Bayer matrix' of colour filters, red-green-green-blue, arranged in a pattern designed to sample each individual colour over as small an area on the chip as possible. Each pixel has just one filter, so a block of four might have RGGB arranged anyhow on the block. B might be top left, or top right, or whatever. When you bin 2x2 you read the entire block of four pixels as one, so there is no colour information contained in that reading. The same applies to any binning scale. Only in Bin1 do you read different values for different colours, so allowing the software to create and then reassemble three images, R,G and B. This is why the term 'One Shot Colour' is slightly misleading. In reality it's 'Quarter of a shot red, half a shot green, quarter of a shot blue!' Olly

I know Dave and would have absolute confidence in him. We already have two here so a third would be hard to justify! I absolutely love this instrument both for visual and for imaging. For APS-C sensors and up it will need the TEC flattener (don't buy any other alternative) and then it has a flat field big enough to land a Spitfire on. The flattener, according to many people including myself, further improves colour correction. I managed without it, but only just, using a 15mm square sensor for a while. Olly

Mr Technology!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 🤣

Firstly I want to say that I'm not making this up: I have used the system! You can buy puppy warmers. Yes! They also work on cats and telescopes... Mine consists of a table mat-sized stainless sheet with a tiny heating element in it. It costs virtually nothing to run and, if it's left near the mount in an insulated, ventilated area it will keep things near it above the dew point and prevent condensation. In your application I would make or source a deeper lightweight box to pop over the mount. Thin marine ply is easy to work with, duly varnished. I'd then line this with insulation material, anything from the hard stuff for walls and roof insulation to flexible camping mat. This will trap the pet-warmer's heat inside and increase its efficiency. Electronics don't like damp in my experience, especially handsets. Olly PS The puppy-warmers are designed not to be damaged by damp - for obvious reasons!🤣

I like this the best of all the images you've posted and think it's lovely. The background level is nice and high so little dark features show against it and the stellar blues, in particular, look right - but so do the reds. The noise is insignificant and if you've used NR it doesn't show. A gentle and perfectly crafted image to my eye. Super. Olly Edit: I've only done this in widefield in search of the extended nebulosity. Joint project with Tom O'Donghue. https://www.astrobin.com/295716/?image_list_page=2&nc=&nce=