ollypenrice

Project with Paul Kummer. This image is based on an all-new 2 panel mosaic in the RASA 8 but incorporates data from an earlier HaOIIILRGB rendition. In the earlier image the narrowband-boosted nebulae seemed to pop out of nowhere. The RASA has found outlying gas and dust which lets them emerge more gently, except in the case of the SNR with its hard-edged shock front. Larger version: https://ollypenrice.smugmug.com/Other/Emission-Nebulae/i-29mLhmD/A Olly

Be aware, though, that getting the colour on this was like getting blood out of a stone. I used multiple iterations of every trick I know. Olly

I also use the bog standard Brightness and Contrast tools on the star layer. This is essentially just a Curves tool but I find it works well. I look for a curve which gives me the right size of stars but which doesn't brighten the background at all. In blend mode Screen the star layer can influence the background if its low brightness values are too high. Olly

Paul and I have just done this target in the RASA/ASI2600 OSC rig. The key thing is star removal at a fairly early stage in the stretch so you can stretch the hell out of the rest. Then there's star replacement. This is where I would rather be in Photoshop than PI because, in Ps, I can see what I'm doing in real time. That's to say, I have the extracted star layer as a layer over the starless and can adjust its histogram using various tools while seeing what that does in real time. Once the black point is set in the star layer, you simply use the Levels mid point slider to choose the star size you like best. I'm sure that Catatonia could have more nebulosity and less star, so to speak. Olly

I've been meaning to PM you for a while, Steve. When we first started with the RASA I was persuaded that it was a widefield instrument but not one likely to reach its theoretical resolution. I said this on one of your posts. I now think I was wrong about this: it is resolving fine detail at a level I truly never expected. Most impressive. Olly

By the way, I seem to think that Paul calculated the width of the plasma jet as being about 2 pixels wide in this rig. Olly

Three hours and three minutes in the RASA/ASI2600. 61x3 mins. Crazy. The only filters were those of the Bayer matrix on the chip. I have a very dark site, sometimes recording SQM22. Olly

Three hours integration. Nuts! lly

I've imaged this region at least three times and those curious edges are there every time - and always in the same form. I do believe them but don't know the astrophysics to explain them. Olly

Just buy it, Michael! Blame me all the way... Olly

Imaged with Paul Kummer. Image five of this week. I think that's it! The RASA again off it's regular stomping ground but the acid test is the high res: https://ollypenrice.smugmug.com/Other/Galaxies/i-Sbc5zmk/A Olly

Imaged with Paul Kummer. Halton Arp was the second most famous astronomer to doubt that Hubble's redshift-distance relation indicated an expanding universe. The most famous was Hubble. Arp's catalogue of galaxies was part of his one man campaign to unseat the established redshift-distance theory. Here Paul took the RASA away from its usual territory and into galaxies at around 100 million LY. See what you think. True to form, it also found some nice IFN around the Arp 80 group. This is image four of our crazy week. Sorry! High res more or less essential for this one: https://ollypenrice.smugmug.com/Other/Galaxies/i-NjWhSPV/A Olly

Imaged with Paul Kummer. Image three from an insanely productive week. This could do with extending either side but it's a nice object and would be worth it. This is just OSC. Hi res: https://ollypenrice.smugmug.com/Other/Emission-Nebulae/i-KRDV37J/A Olly

Imaged with Paul Kummer. A second DS image this week. Large version is here: https://ollypenrice.smugmug.com/Other/Emission-Nebulae/i-KBLWZQm/A Again, the OSC is softer on the gas and deeper on the dust than the HaOIIILRGB I have already and the OSC image in the RASA took - ahem - 3 hours! Olly

Imaged with Paul Kummer. The first of five deep sky images completed this week. It is hard to keep up with the RASA! Flaming star and Tadpoles. I've done this before in HaLRGB but this is just RGB (OSC.) The big difference is the amount of dust in which the emission nebulae are bathed. Because I used to rely on the NB data to find the emission nebulae I didn't go as deep as the RASA goes on the broadband. Finding so much dust around the emission nebulae was a real surprise and gave the region a new look, to my eye. I've also been impressed by the resolution in this week's images, not having thought of this as a high res rig. See what you think of the Tadpoles in this link to the full size: https://ollypenrice.smugmug.com/Other/Emission-Nebulae/i-gKkD2DQ/A Olly

Sorry, posted in wrong section. Olly

Epsom Premium Glossy. Olly

I don't! I may be odd (as has been suggested frequently over the last seventy years) but I do not pixel peep the corners and recommend this omission whole heartedly. lly

I use an ink tank Epson 15000. The bottled inks are really not expensive and go a very long way. It can print up to extended A3 and, although it's only a 4-ink machine, I find the prints to be excellent - and I'm fussy. Because I can do a small test print first, this beats hoping for the best with a third party service. Olly

Start with your unreduced, processed final TIFF in Photoshop. Use the crop tool to set the proportions you want to end up with, so 12x16. (This crops to a proportion, not to a final size.) Go to image, size and uncheck resample. Set the dimensions to cm or mm, not pixels. Set these dimensions in the appropriate boxes. See what PPI value this gives you. It's shown on the screen. If it's enough for the printer, fine. It should be. If it's not, check resample and next to that choose Preserve Details (enlargement.) Type in the PPI you want. The other thing to remember is the colourspace. The printer needs to know which one you are using. The internet standard is sRGB but it isn't the best to work in. I process in ProphotoRGB and print from that but, for the net, I go to Edit-Convert to Profile (note, not Assign Profile) and choose sRGB if that's what the printer wants. If you're not sure what colourspace you're using in Ps, go to Edit - Colour Settings and see what colourspace is there in your working spaces. It should be OK just to tell the printer what you're using. It's always best to do a small test print first because, with the best efforts in the world, getting the screen and the paper to match up is not dead easy! Olly

Just buy a Mesu and autoguide it. There are five of them at my place and they simply work. Olly

It does depend on the target. In the IFN image, here, there is nothing much to resolve apart from M81 and M82 and, if you want to see those in detail, just take a telescopic image. Now that star size can be controlled, the big lens disadvantage of large stars is rectified. However, if the frame contains lots of finely detailed objects, you will see a lack of resolution in those regions when using a lens, even unzoomed at PC screen size. This is where it becomes advantageous to do composite images in which regions of interest have a boost in resolution from higher res data where it will make a difference. Since the high res data will be downsized to fit, it does not need a high S/N ratio. Our plan is to try, say, 4 hours in the Samyang plus an hour per region of interest in the Rasa and blend those. The blending is simplified because the starless high res can be blended with the starless widefield and then the widefield stars re-applied for the lot. This will provide visual continuity and make the overlays seamless. Olly

It's an interesting comparison. The main structures agree, which is good. In some places I have more contrast, in some places he does, but the shapes are very comparable. Since it isn't an image inviting 'zoomability,' and since star size can now be controlled, I have to say that I'd rather take this picture in 3.4 hours, but a real IFN buff would, rightly, go for his. It's beautifully put together. Olly

I think we all do that with the IFN - and quite rightly. I overlaid this on my earlier version and was relieved to find good agreement. Olly

No, the image I posted is a single panel from a Samyang camera lens, 135mm. Olly