ollypenrice

Perhaps a member near you might let you try your handset in their mount? Olly

Fabulous! Exceptionally deep and yet exceptionally clean with superb levels of local contrast in the Ha. Beautiful processing, too. The result has rewarded your effort. Olly

Très belle galaxie! Balanced colour and brightness giving a natural look. Olly

This target really comes to life in NB, with a distinct change in gasses, therefore colour, between body and pincers. Very deep and clean. A just reward for your patience. Olly

Your OIII is way better than mine, which had 11 hours at an exceptionally dark site. I was using a mono CCD (Atik 11000) and Baader OIII filter. This was a decade ago and I think we can say that the technology has improved! Great stuff. Olly

I certainly agree that the Samyang is mightily out-resolved by the RASA but here, we are comparing massively different apertures. As regards depth, I think it's 'aperture per pixel' which matters. I'll go back and compare our own RASA and Samyang data on the same targets. I've blended the two without paying particular attention to this. Olly

The theory will be overwhelmed by the practice in comparisons like this. An 8 inch scope has higher optical resolution than a 6 inch if both are diffraction limited. To give the same FL the larger scope has to be faster, making it more susceptible to optical imperfections in the grinding of the mirror, the collimation and the mechanical alignments. Which will be the real world winner? It depends on the specific instruments in use. In DS imaging, sharpening in post processing has an effect on final resolution and more signal can take more sharpening than less signal. This favours the faster scope. If you are over sampled the optical resolution comparison goes out of the window because you'll be seeing limited, but the larger, faster scope gets more light. See previous point. I firmly believe that these discussions are academic and that the success or failure of an image derives from a dozen other things before the niceties we are discussing here have any contribution to make. I also know from experience that not all reducers play nicely with all optics and, given the very questionable wording of Starizona's Hyperstar advertising, I would read anything they write with a high degree of critical distance. For example, The HyperStar 8 lens converts a standard Celestron 8" SCT from f/10 to f/1.9, making the system 25 times faster. That means 25-times shorter exposures! For this to be true, the Hyperstar lens would have to increase the area of the clear aperture by 25 times and then we could consider it to be the same 'system.' Olly

For some time I used a Takahashi EM200 mount which has no facility whatever for leveling the top of the tripod. EM200 users at latitudes outside the fairly limited adjustment range of the mount routinely tilt their tripods to reach alignment. I'm assuming a reasonable degree of intelligence in not overdoing this. Within reason it is a perfectly normal thing to do to make your mount's adjusters more comfortable. If they are OK when horizontal, then fine. You can also expect Polaris, if visible this close to the horizon, to be displaced visually by about half a degree by atmospheric refraction. I have observed on the equator and would not make Polaris my primary means of alignment if I lived there. Olly

Can't agree on NR. It already looks like 'vaseline on the lens' and that's the root of the problem. But I do agree that it's a good image. How about resampling it down to a lower resolution , accepting a smaller rendition, and getting a cleaner image? Olly

I disagree with most of the advice above. 7 degrees above the horizon is not going to work for any kind of Polaris-dependent PA routine. You'd need a fantastically low horizon and minimal light pollution to see it at all. No design of pier is going to get around this, so forget it. You can Polar align by other means, quite successfully. Use a compass, corrected for your magnetic deviation, to point the mount north. https://www.magnetic-declination.com/Sri Lanka/Colombo/1481546.html#:~:text=Answer%3A -2.09° (-2°5') For the purposes of this method, just remember that your compass will be pointing about 2 degrees west of north. That will do. Even just using the compass's magnetic north without correction will do. That gets you in the rough position for Azimuth. Don't use the compass close to anything magnetic, like electronic devices. The rough position for altitude is going to mean that your polar axis is only going to be about 7 degrees off horizontal. If this is a problem for your mount, don't hesitate to tilt your tripod to make it easier. The base of the mount does not need to be horizontal. Many will say it needs to be horizontal but they are mistaken. I would make a physical wedge with a 7 degree angle and place one side on the the mount and put a spirit level on the other for quick repeatability. Once the mount is in this position, just use the drift method. It has various versions. This is a very intelligent one for imagers. https://www.cloudynights.com/articles/cat/articles/darv-drift-alignment-by-robert-vice-r2760 Forget Polaris. It will not help you. Olly

I regard SCNR as a linear-stage tool. Sometimes I'll run it and not run it, making two versions which I can then blend easily and selectively in Ps Layers. Olly

Personally, I'm suspicious of this stage. The effects you describe look like excessive NR to me. Regarding NoiseXt, or any other NR, I don't know what the official recommendations are but I cannot imagine running NR before knowing where I wanted it and what its consequences were. Hence I run Noise Xt on the starless once it is sufficiently stretched to reveal noise. I apply it to a top copy layer in Ps so I can blink the NR version on and off to see where it's good, where it's bad and whether or not it's over-done. I can then erase it from where it's harmful, retain it where it's good and adjust its opacity. Using layers I can see what I'm doing as I do it. I don't think anyone could ever persuade me that making a guess at what to mask and hitting 'Apply' was a better way of doing it. Olly Edit: regarding green, try SCNR green. I run it on 9 images out of 10. DBE doesn't deal with it for me.

None of them does. The alignment adjusters you'll have seen were invented for the opposite reason: They allow the guide scope to be moved off axis in search of a guide star. In the past, this was necessary for guiding on a star by eye or when using early and insensitive guide cameras which only picked up brighter stars. They are now redundant and I would far rather have a guidescope bolted down hard than carried in potentially flex-prone adjusters. Guiding on an off-axis star has one side effect. If polar alignment is out, the imaging scope will describe an arc around the guidestar. If you guide on a dead central star the chip will rotate on its centre point. If it's off axis it will describe an arc. If shooting in old-school 30 minute subs, polar alignment is critical. Since CMOS cameras use only short exposures, and since stacking software will easily align slightly rotated subs, polar alignment is less of an issue. Nutshell: guidescopes don't need to be precisely aligned, as everyone has said. They do need to be rigidly mounted. Olly

Dramatic improvement. The processing of dense starfields has been transformed. Olly

Dust from the city is very good going indeed! Olly

Good going on a tiny target. Impressive. If you are shooting in RGB, rather than colour mapping in narrowband, there is a right colour, at least in a reasonably broad sense. It can be checked by looking at your background, which should be about equal in RGB, and your stars, which should match the astrophysics of their spectral class. I think that, in this image, the colours are a little out in a consistent way, with the reds too yellow and the blues too cyan. I would guess at this arising from too high a value in the greens, perhaps because of the filter. I haven't used this one. Olly

Super, Rodd. I think refractors are fine on globulars. My TEC140 did well on M13, too. Olly

It will probably have no visible effect whatever, though it might just create a slight diffraction spike on brighter stars. If it does, try covering it (on the outside) with something black, like a small piece of electrical tape or black paint. Avoid straght lines on this tiny blackout patch. If this seems odd, remember that many telescopes have large, opaque obstructions slap in the middle of the objective. Ours, for instance... The obstruction is far too far out of focus to form an image. Olly

Clearly you're going to have to find the right power supply if using it in the field but, running on mains and a regular 12V transformer, ours is fine. It's a great camera and you did the right thing going for a bigger chip. In fact the Redcat covers full frame very sweetly. Olly

I used a motorhome for going to dark sites before going to live at one permanently. It can work well but there are issues. Motorhomes are often totally useless on soft surfaces and get stuck at the drop of a hat. This may explain the campsite rules mentioned earlier. The trouble is that the best places for astronomy are, therefore, often the worst places for campervans. This was a major stumbling block for me. It also proved disappointing not to be able to Certified Locations (minimalist campsites) because, again our coachbuilt got stuck too easily. Olly

Sometimes tilt is improved by rotating the camera in the OTA, probably because a number of imperfections cancel themselves out. There might be a bit of tilt in one component which goes the opposite way to that of another in one particular orientation. It might be worth a try. If you find such a sweet spot, as we did with our RASA, you can still rotate to frame a target by rotating the entire OTA/camera in the tube rings. Olly

I was assuming the camera would be appropriately filtered in this regard. This has been the case with all my OSCs but maybe some just have a clear filter, in which case you'd be right. Olly

Let's think it through. An OSC camera has either a red, a green or a blue filter permanently fixed in front of every pixel. That is what makes it an OSC camera. If you put a red filter in front of this, only the camera's red-filtered pixels pixels will get any light. The same applies to the other colours. With a green filter in front, only the camera's green-filtered pixels will get any light. Clearly, therefore, RGB filters would be pointless. What's a Luminance filter? It's one which passes R and G and B. But your camera's filters are only going to pass the colour they pass, so R or G or B. A luminance filter would, therefore be useless. Basically, you are going to be imaging with the camera's in-built RGB or with the dual band filter which further restricts what you capture to the light emitted by two gasses. Some targets will be best unfiltered, some filtered and some combining filtered with unfiltered. The worse your light pollution, the more favourable the filter becomes. Olly