ollypenrice

Glad you've sorted it. I regard the 'Pixinsight ethos' as being pure tosh. It reminds me of those monks whose vows forbade them to handle money so they wore gloves. If the PI ethos is based on being 'true to the data' then your only option is to leave the spike in place. I see no difference between painting by numbers and painting with brushes! Olly

With a working reflector! But please don't take my comment seriously, it was tongue in cheek. Olly

You're aware of Steve Richards' setup guide for the SiTech Mesu? I have never used it but it is universally praised. Olly

Gradient removal does need the right software tools. I think the top dog is still Dynamic Background Extraction in Pixinsight but there are others. AstroArt is pretty good. The previous post shows that the data are workable. Olly

With an LRGB image a good trick is to use only the RGB for the brightest parts. Often they are equivalent to short subs for this purpose and they'll carry more colour as well. I haven't processed this latest IKI set but that was how I did my own Iris and a good number of other images with bright parts needing control. Olly

That's great. No question. Personally I'd have another look at the core, though. I suspect that, with a dedicated stretch carefully blended in, you could resolve the central star as a round star with bright nebulosity around it. As your stack has increased, so has the saturated area around the progenitor star, but that can be prevented in processing. It's well controlled as it is but I bet you could perfect it. Olly

'Clone Stamp' suggests you're a Photoshop user. Noel's Actions (now Pro-Digital Astronomy Tools, I think) has an action for removing vertical banding. I would run the action on a bottom copy layer so that you could then go to the original top layer and erase the lines to reveal the repair only where it was needed. If you don't have the actions - you should! You could also make a copy layer and, again, work first on the bottom, very crudely clone stamping the lines and not bothering to avoid the stars. Just stamp them out. Then go to the top layer and use Colour Select to pick up the lines. This will pick up all sorts of other stuff as well but with the right sized eraser you could erase the top fairly quickly with no great need for accuracy. Or yet again: copy layer and work on the bottom. Curves. Pin the curve at the background sky brightness and add a fixing point below that. Pull the curve down just above that till the lines have the same brightness as the background (ie they have disappeared.) Restore the curve above that to make the rest of the image fairly similar to the orignal. Go to top layer and erase the lines, maybe using the Colour Select tool as above. Olly

A helpful post. As your signal builds, so does the need for some differential processing to preserve the core while stretching out the dust. In PI you'd do this by masked stretching. I'd do it in Photoshop using layer masking. They key thing, though, is that it would be well to process the long set differently from the short. Olly

As Michael says, this is an emission Nebula filter but I think you should have had some success with the Lagoon which is quite strong in Ha. I've imaged it easily from my dark site with an OSC camera unfiltered. You say one image is autostretched but I don't know what this autostretch process is. It hasn't stretched the stars so why would you think it had stretched anything else? Does the nebulosity show if you stretch manually in the usual way (eg Levels and Curves in Photoshop? And has it been debayered for colour? It doesn't look as if it has. This may just be a software/image extraction problem. Olly

No, the Mk 1.5 is festooned with nuts and bolts: the real Mk1 is extremely elegant! 🤣 Something tells me it has been a long time since your wife last visited a scrap yard!!! You now have the best mount in the business. Bar none. Olly

The colour in the Horse and Flame is perfectly convincing so the debayering and stacking process was being done more or less correctly in that one. In the Sadr image the red channel is overwhelming and there is clear evidence of black clipping. The sky is flat jet black and the clipping is confirmed using Photoshop's Levels. As you can see, the histogram peak is jammed up against the left hand side. The left hand half of the peak has been discarded, meaning we don't know what it contained. This test was performed on a JPEG screen grab but I have found by experiment that it is, none the less, reliable. In order to analyse an image properly we need to see it in its linear, unprocessed form, straight from the stacking software. There is always a temptation to remove light pollution (including that from the Moon) by black clipping, ie moving the black point slider to the right. Resist this temptation because it simply discards a large part of your image. The stretched image should have a histogram with a fully formed peak away from the left hand side and at least a small strip of flat line to its left. It also looks as if you have an issue with alignment since there is a 'frame within a frame.' Before trying to analyse or process an image it is vital to crop away any such edge artifacts so you are working only on an image to which all the sub exposures have contributed. Olly

What point are you making? I genuinely don't know. Olly

Why leave the house at all? Pictures of the whole world can be seen on the internet. Why? Because looking at pictures (other than original works of art) is not an occasion. Occasions are made when we go somewhere in real life and do something. Your garden out with your telescope will not be your garden as it has ever been before. It will be out in space. You will see the roll of the Earth with your own eyes. Space will be real and tangible and you will be in it. Seeing a deep space object will be an occasion you will never forget. But hang on, am I not an astrophotographer? Yes I am, and making my own photographs is not something I do primarily in order to look at the finished pictures. In fact I look at them for a short while afterwards and then have increasingly little interest in them. This may seem odd, but does an amateur musician play an instrument in order to listen to a recording of themself later on? No, they play because they like to make music. I'm an astrophotographer because I like to make astrophotos. The act of creation is both thrilling and satisfying. The act of creation. Olly

I stopped learning anything about image acquisition years ago. Processing, though, is a never ending... er... process! lly

It's a very good question. I started about 13 years ago. I have the advantage of lots of clear nights so I was able to make recognizable images of larger galaxies and nebulae in a couple of months. They look now, of course, like many beginner images look. It probably took about three years for the learning curve to flatten such that what I did after three years looked something like what I do now. What I do now is not very different from what I did five years ago, so the curve is now pretty flat. That doesn't mean I've learned it all, it just means that I'm pretty much out of ideas! Olly

Indeed. I once bought a Genesis very cheaply because the front cell was out of collimation. It was very easy to fix once I'd had a chat with TV, who were extremely helpful. Olly

A point I would make is this: it is fundamentally unscientific to say that all reflectors can be easily and successfully collimated. All anyone can say is that they have successfully collimated the ones on which they have worked. Sometimes individual instruments may have defects in construction which prevent them from behaving in accordance with the theory. I tried, unsuccessfully, to help a guest with a GSO RCT one time. We watched all sorts of tutorials, including Steve's (Kirkster's) and we kept encountering interactions between adjustments which were not covered by any source of information we could find. Singlin's excellent thread on sorting out a Quattro is instructive in this regard. Olly

There are lots of things nobody has ever seen in a telescope but which can be photographed... Olly

I don't like messing about with optics so I use refractors. That means two things: I'm lazy and I enjoy astrophotography... 😁lly

That might have been my review in Astronomy Technology Today? (My only appearance on American soil!! 😁) Olly

My somewhat fatalistic opinion: the only way to make high res dual rigs work is to follow Peter Goodhew and use an active optics unit on the slave scope. There is now a wide body of opinion 'out there' that you can't beat diff flex on high res dual setups by any other means and I'm persuaded by this. I was an early dual rig adopter with twin FSQ106/Atik 11000 systems on a Mesu and with a Cassady T-Gad alignment device. It just worked - perfectly - from day one. I confidently assumed, therefore, that the transition from that system at 3.5"PP to a TEC 140 dual rig at about 1"PP would be easy. It wasn't and still isn't. Sometimes the 'slave' trails, sometimes it doesn't. I've had plenty of conversations with others similarly afflicted and the only winner I'm aware of is Peter with his AO unit. He says his FWHM on the AO-corrected slave is actually better than than that of the guided tube.) I'm not up for fighting with one of these notoriously difficult devices so I'm at the point of using two mounts, one per TEC 140, as being the least painful way forward. (I do already have two mounts.) One thought: since dual rigs are popular I wonder if a manufacturer might be able to make a factory-assembled one-piece dual rig with a monobloc chassis for two optical paths. Or would diff flex in the focusers still get us? Who knows? Olly

Focus certainly moves during the night, though how quickly depends on the rate of temperature change, the thermal stability of the scope and the imaging resolution. (Higher resolution will 'show' focus drift more readily than low.) I wouldn't use the FWHM value from one night on a subsequent one or in a different part of the sky. The seeing varies considerably so you might reach a lower value tonight than last night, etc. And the higher you are in the sky the lower the value is likely to be. Olly

Having made the first ever solo flight by Marquee across Kinder Scout I can easily follow your line of thought... Olly

I think that some astronomy manufacturers have achieved a considerably inflated reputation based on prettiness and lots of red anodizing. My only WO scope looks OK but the focuser slips and sags and the main tube is far too short. At the other end of the scale someone described my Mesu 200 mount as looking like 'a bag of spanners.' This mount, approaching ten years of age and in commercial use, has yet to drop a sub exposure to guiding error. My TEC 140 is a very 'plain Jane' of a scope, nothing cutesy, but it ain't for sale! Olly

...and they mire themselves in that nightmare term, 'crop factor' in which chip size risks becoming an equivalent of focal length. (They also mire themselves in the notion that full frame cameras have a greater depth of field but this is only because, at present, full frame cameras tend to have larger pixels.) It is the astrophotographers who have the proper understanding of focal length, field of view and resolution. (Says an astrophotographer! ) Focal length is written on the lens. Chip size determines field of view. The ratio of focal length and pixel size determines resolution measured in arcseconds per pixel. Deviate from these simple facts and you plunge into the mire! Daytime photographers do have an interest in perspective, however, since the naked eye creates a relationship in size between foreground and background objects which they may wish to preserve or to over-rule and here the vile term 'crop factor' might be spared from summary execution! Astrophotographers always work at infinity. (Infinitely difficult, infinitely expensive, infinitely exasperating...) Olly