ollypenrice

🤣 You'd have to be miles out of focus for those to be dots. They are circles. OK, I called them dots. Big dots - like circles... 😁lly

OK, if that's the full field, ABE might beat DBE. However, on this image I'd just try four DBE points as shown by the white dots. Olly

What was your uncropped image? To do DBE you need background markers distributed across the frame. One in each corner would be a minimum, I think. When I don't have that available I generally use ABE. This target tends to be full of nebulosity with dark sky conspicuosly absent! I'd certainly try SCNR green as well. Olly

I agree with Vlaiv that there's real OIII in there. However, I think you may have a red-green gradient (red left, green right.) This is common on OSC data, I find. Compare the dust patches in the lower part of the image. Those on the right are distinctly green. What we can see of the background (top left and top right corners) also confirms a greener right hand side. Lower levels of green will turn things magenta and that, too, might be going on just left of centre. What do you use to neutralize gradients? My guess is that Pixinsight's ABE would sort this out, and/ SCNR green. Olly

LRGB is actually faster than OSC because the luminance phase of the capture lets all colours of light onto all the pixels all of the time. If you want to add narrowband data then it becomes a lot faster. It can be frustrating to be robbed of a filter's capture by cloud, though. However, I think that OSC CMOS cameras are more convincing than OSC CCDs used to be and the dual or tri-band filters are a boon. I wouldn't try to choose a camera long in advance because the models are changing very quickly. You just need to choose a camera with an APS-C sized chip and it won't be significantly different from your 600D in format. Olly

I think the first thing is not to expect too much from those small mechanical setting circles. Not many people really use them. Polaris is, within the accuracy you'll achieve with these circles, at Dec +90. (It's less than a degree off from that.) If you centre Polaris in your eyepiece you can see what the Declination circle reads. It should be 90. Don't check your RA circles using Polaris because, during one day, it only describes a tiny circle. Choose a star as close to the celestial equator as possible to do that. A planetarium software such as the free Stellarium will tell you which stars are close. Olly

In my (amateur) understanding the incident photons energize the atoms they strike and these atoms then emit a photon of equivalent energy. Is it accurate to consider this 'the same photon,' whatever that might mean...? Weird stuff. 😁 Olly

But they don't. An incident photon is absorbed within the surface of the mirror and a different one is released - etc etc! Olly

I feel for you. That's why, to the amusement of many, I do nothing via PC which I can do by hand. Doing things via PC automation and control gives endless advantages till it stops working. How often does it stop working? Pretty often, say I, as the host of six remote imaging rigs. Computers promise the Earth and deliver... earthquakes. If you don't want to faff about with the optics, buy a refractor of proven performance. Don't read glass specs (FPL 52/53, yappety-yap, doublet-triplet-quadruplet-sextuplet-octuplet.) Just look at the images they produce. Your budget will only allow something with a bit of blue bloat? Fix it in post-processing. Olly

I know the theory but what I'm interested in is the practice. I have a 14 inch SCT (Meade) and its LX200 mount is acting the goat. It's over 20 years old. I don't do enough visual observing myself, or have sufficient visual guests, to justify (easily) an EQ8 and I already have a couple of EQ sixes. I've just tried a 10 inch SCT on an EQ6 and it is far more stable than the LX200 mount, which is like coil spring at best. I know the EQ6 would make the 14 inch under-mounted but it is already grossly under-mounted on its official LX200 mount, even for visual. You can still enjoy it, though. Has anybody tried a 14 inch SCT on an EQ6 for visual? I don't want to de-fork mine without knowing how I'm going to mount it. Thanks in advance. Olly

The SCT is admirably compact and the views are between good and excellent. (My own experience says that the bigger they are the better they get relative to Newts of the same aperture. That's just my feeling. The not inconsiderable downside is the restricted field of view. A 10 inch on an EQ5? Just this afternoon I've put a 10 inch Meade on an EQ6 for visual and I have four counterweights on there... Olly

You can, I gather, also get an ICC profile done online for your own monitor to ensure compliance with calibrated norms. I don't see myself going this far! Olly

A veritable rabbit warren, in fact! Since I started printing my own photos I've done the homework I should have done years ago. I'm still not sure I've got to the bottom of it. Olly

There are various different gamuts or colour spaces available for processing and viewing images on screen. There is no one, universal, way to combine red, green and blue so, ideally, an image should only be viewed in the 'colour space' or gamut in which it was processed by the imager. The 'best' colour spaces have the widest gamut or range of create-able colours when combining R, G and B. Many feel that Prophoto RGB is as good as it gets with Adobe RGB a good alternative. You can choose the one you want in Photoshop and, I guess, other photo editing suites. The internet standard is sRGB so you should post images in that colour space even when you have processed them in a better one. I used to keep it simple by processing in sRGB but I no longer do that. Conversion from Prophoto to sRGB is done in one click in Edit - Convert to Profile. (Be sure to use this rather than 'Assign Profile.') Photoshop etc will let you convert from Prophoto to sRGB for the version you're going to post. If you don't convert, the image may look horrendous. Print shops must choose a colour space for your image but I don't know what they use or how they choose, which is why I'd ask. Olly

I've started printing my own using an Epson Ecotank ET1500. I generally found Monoeuvre to be fairly good with astrophotos but then spent a hefty sum on a large image on aluminium which came back miles out. Astrophotos, being highly stretched and having a lot of dynamic range, are particularly unpredictable - especially broadband. I now easily beat the standard of the Moneouvre prints and am happy with my prints - despite being a fussy so-and-so! The printer was expensive to buy but there's a less expensive A4 version. Mine does A3 and even extended A3. The great thing is that it uses bottled ink so running it is extremely inexpensive and not an issue. It's also possible to do a small test print to check out the result before doing a big one. I usually do this. I also calibrate my screen with a Datacolor Spider. Colour fideltity is usually good in the print but brightness levels sometimes need adjusting, the highlights lowering and the shadows lifting. A calibrated screen will help a third party printer get a good result as, perhaps, will the adjustments I mention. I'd also ask the printer what colour settings they use. I now process in ProphotoRGB and convert this to sRGB for the internet. I print from Prophoto at home. Olly

That's good to know. Many people report success with APP as well but in this 32 panel, captured by Yves Van den Broek, it was able to make an excellent job of the geometry but not of the seamless joining or calibrating. Yves is very competent with software but short of time, so he gave it to me to assemble the DBE subtracted panels. I used the DBE- partial stretch-manual adjust- join-patch-check in PS Equalize-repeat method described above. It isn't fast! I worked in strips of 5 images at a time and then joined the strips together. https://www.astrobin.com/g82xf7/B/ The trouble is that are are things the software won't automatically allow for, like changes in FWHM, levels of sky transparency affecting levels of blue bloat, etc etc. With a large mosaic you can't hope for perfect or identical sky conditions for every panel. Far from it. Some of the panels in the Cepheus image needed quite a lot of cosmetic work to make them blend in visually with the rest. Almost everything I now do is a mosaic and sometimes, but only exceptionally, a linear combining of DBE-subtracted, colour-calibrated panels gives a stretchable result. Of course, this also depends on how hard you want to stretch but it's in the nature of mosaics to beg for very hard stretches in search of the faint, linking nebulosity between 'areas of interest.' Olly

If anyone thinks that one system will always work for deep sky, they haven't done enough mosaics, or they've been luckier than I have! One system will not always work. If you're lucky, you can combine calibrated, flattened, gradient-corrected, colour-balanced linear images and get a seamless result. I find that this occasionally happens on modest mosaics, up to maybe six panels, though it's far more likely that there will be the odd joint or glitch visible when you stretch. There is a quick way to test the seamlessness of your mosaic: run it through the Equalize adjustment in Photoshop. Joints, colour changes, etc etc, will scream at you! Don't panic, this is a diagnostic tool to tell you where your problems lie. You'll then discard it. The most consistently reliable method I've found for very large mosaics (like the 30-odd panel ones I worked on with Tom O'Donogue and Yves Van den Broek) is to combine partially stretched panels using Registar. However, keep all the registered-calibrated panels that went into this. Move on to Photoshop and check for irregularities using Equalize. They will be there. Use the saved registered-calibrated panels, adjusted by hand, to make patches over the problem areas. The software to make seamless linear deep sky mosaics reliably, such that they can then be stretched and processed for local contrast enhancement, etc, which you will want to do, does not exist. Olly

Please feel free. I used it as a teacher when encouraging argument as an activity. All I had to do was say, 'I can make an argument for anything. Go ahead, try me.' One of the kids would always say, 'Argue that black is white,' and away I went! 🤣 Olly

The ADU value is tolerant but you might need a lot of paper to get up to 3 seconds... Olly

Step down rings do stop down the aperture and so increase the depth of field. The stopped down light cone has a shallower angle than the wide open one so the focal plane can be moved forwards and backwards by a larger amount while retaining acceptable focus. Since the rings are designed primarily for daytime use, which will include aiming at bright blue skies, I imagine they must be effectively blackened against internal reflection. Olly

Sorry to repeat myself! The joy of the real Mk1 is that it is PC free and standalone. I remain a great fan of the handset mount, having had so many fights with externally controlled ones. Olly

Ignore my doubts about focus. I think you must be getting close to what the system can deliver. Good going. Olly

Oh but you can! It's quite easy: consider black as being the darkest possible form of grey, while white is its lightest form. Both being grey they are, therefore, the same colour... 🤣lly

I agree, and the fact that they don't listen to their users confirms the charge. Behind a communication problem lies an attitude problem. I spent the first half of my working life as a teacher, a job in which much more effort goes into finding ways of communicating ideas than goes into mastering the ideas themselves. I met two imagers who signed up for a two-day PI course run by the developers. They lasted 10 minutes and walked out. These guys were not fools, both having established and managed very successful businesses. Olly

Great image. I never get dust to look like that, with such a brightness range. Although it's pushed very hard it's also impressively clean. I must admit that I'd like to peep over your shoulder when you process your dusty stuff... 😁lly