ollypenrice

For sure. Plus, we are working from a seriously dark site which often has very high transparency. On the other hand, the nearest fish and chip shop is about 600 miles away... lly

We aim to please! Happy Christmas, Dave. Olly

All broadband OSC. There's no telling which objects just won't play. In most cases we don't miss the NB but, occasionally, we get nothing without it. The Orion image is spreading its wings... 93x3 minutes, Alan. I'm sorry but I can't remember what UV-IR cut we use. In truth I don't remember a filter at all. It's a ZWO ASI2600MC. Might it have a filtered chip glass? Edit: Dave, below, says it does. Olly

You may have seen this field before. Paul Kummer shot this as a time filler but I'm glad he did because it has some nice differences from my existing TEC140 version. RASA 8, ASI2600 OSC, NEQ6. Anyway, we like repeats at Christmas! Best wishes, everyone. Big one here: https://ollypenrice.smugmug.com/Other/Emission-Nebulae/i-FtHhTq9/A We do have something special in the pipeline as well but it will probably be new year before we have it all in the can. Olly

There's no reason why a red filter won't, in principle, pass all Ha but there is every reason why an Ha filter won't pass all red. The Ha will also exclude more LP in many cases. And then, this being the case, we can stretch the Ha harder as well. Olly

Capture and pre-processing, Paul Kummer. My post processing. RASA 8, ASI2600, NEQ6. I think this is a stunning nebula which Paul and I did in close up a few years ago during one of his stays here. This time we have a wider view, though this is actually a crop from a considerably wider field. I particularly like the moon-like nebula to the left, LBN990, which seems to have a streak of cloud in front of it. Certainly one of my favourite objects. Large one here: https://ollypenrice.smugmug.com/Other/Emission-Nebulae/i-njVs8H4/A Olly

This target tends to be dominated by narrowband renditions but here we have deep broadband colour. The obvious difference is that the nebula is seen to be embedded in dust and lies at the edge of a dusty front. The RASA 8 was driven by Paul Kummer, remotely, and he did the stacking. My post processing. This was a very enjoyable data set to work on. For the finer details the big one is here: https://ollypenrice.smugmug.com/Other/Emission-Nebulae/i-7Z5phNC/A Olly

I don't want to present myself as a pundit but my view is that, if you combine it at the linear stage, you have relinquished almost all control over it. Let's remember that there is no 'natural' value for the Ha contribution. There is no way to calibrate it 'scientifically' with the rest of the image because the calibrated Ha is, surely, just what is already contained in the red channel.* The whole point of the addition of Ha is to distort its contribution to the image and allow us to reveal structures otherwise not visible, though certainly present in scene we are photographing. This is an artificial process and we are the the artists - or artificers - responsible. Olly *This does not apply to those daytime DSLRs whose filters do block most of the Ha.

I just downloaded AI4 and it is a catastrophe for our RASA images. We get elongated stars on one corner, some of which look almost like overlapping doubles. Blur XT with the previous AI module sometimes split them into doubles. With AI4 operating, it splits them into doubles even more perfectly and splits previously acceptable corner stars elsewhere into doubles as well! I know we should fix this with collimation and tilt but it is an undertaking to fiddle with the RASA and the problem is usually cropped out in the final cut anyway. Does anybody know how I can go back to my previous AI package? Olly

Of course! We all remember 'Sara's palette,' a dramatic orange-blue spin on HaOIII. Olly Edit: You could set up an ELP line for those wanting to try it...

Very crisp and three dimensional. Olly

It's an attractive palette. Olly

University of Central Lancs has a Grubb Parsons like this. (Actually it has two in parallel, one corrected for visual, one for plate photography. I observed Saturn through it once. This was not a very informative target but the image was decent, though not as good as that of a 12 inch SCT, I don't think. That's not really the point, though... Olly

I don't know how you'd do it in pixel maths (confound that American spelling!!) but, in Photoshop, I add it to the red channel in blend mode lighten. This means that it is only applied to the red channel where the pixel brightness is higher than the red. How might this be done mathematically? I really don't know but there will be a way. A couple of pointers to Ha processing, though, when the result is destined to go into the red channel. - You can ignore low level noise which is less bright than the red because it won't be applied. - You can stretch the strong signal very hard indeed. - Your background value in Ha should be a point below the red to avoid its being incorporated. - It can be good to go for extremely high local contrasts because these will be diluted by the red channel. In short, I wouldn't process an Ha image in quite the same way for adding to red as I would process it for standalone Ha. Olly

I think that, as a general rule, the worse your LP, the greater the advantage of tight bandpass filters. If I compare my 7nm Baader Ha with my 3nm Astrodon, at a dark site, the latter is more moon-proof and gives perceptibly higher local contrast. It is not slower than the 7 Nm. It may be faster. Olly

Sleep? lly

I denoise the starless layer whichever way I'm doing it. I do it as a top layer so I can erase the denoised regions of strong signal if necessary, though with NoiseXterminator this is rarely worth bothering with. What I do find is that a starless image which has what seems to be the right amount of noise reduction can often look over-smoothed when the stars are back in the image. I've been caught by this a few times and now leave a margin for a light final denoise at the end. Olly

The RASA does not naturally produce the best stars so this may be a factor. A separate 'stars only' layer and blend mode Screen was how I was doing it as well. I agree that blend mode lighten is not good with a layer of extracted stars but, in the workflow I describe, the stars have never been extracted so they have never had their outer boundaries defined. Olly

This is the wrong question. The right question is What mount should I use? The mount is the most important part of the setup. If your hands are trembling, it makes no difference at all whether you shoot with a Hassleblad or a 50 euro compact. The pîctures will both be blurred. There are tracking mounts for cameras with camera lenses. https://www.firstlightoptics.com/star-tracker-astronomy-mounts/skywatcher-star-adventurer-mini-sam-wifi-astro-imaging-mount-bundle.html There are mounts for small telescopes. https://www.firstlightoptics.com/equatorial-astronomy-mounts/skywatcher-heq5-pro-synscan.html There are mounts for larger telescopes. https://www.firstlightoptics.com/equatorial-astronomy-mounts/skywatcher-eq6-r-pro-synscan-go-to-equatorial-mount.html And there are mounts... https://www.modernastronomy.com/shop/mounts/mesu-optics-mounts/mesu-e200-mount/ This was taken with a 130mm camera lens. https://ollypenrice.smugmug.com/Other/Emission-Nebulae/i-XjrmQNd/A For starting in AP I would suggest a telescope with a focal length of less than 500mm. Beyond that, everything gets much more difficult. Olly

Stop before wasting your money. Astrophotography is not like normal photography. If you look at amateur astrophotos of the deep sky and would like to have a go at taking them, it is vital to understand how they are taken. They are taken using mounts which track the sky, and the Fi6 does track the sky but not, unfortunately, in the right way. It tracks by moving left to right and up and down. That is not how things track across the sky. When Orion rises he is leaning to the left. When he sets he is leaning to the right. Your photographic mount must allow for this, meaning it must be equatorial and not alt-azimuthal, like the Celestron. You can tilt the Celestron on a wedge to make it equatorial but, trust me, just don't. Mounts simply switched on and left to guide cannot guide with the accrurarcy needed to take the pictures you may have seen here and elsewhere. They can get you started, though. It is much better to start with a short focal length than a long and, at 1500mm focal length, the Fi6 is very long indeed, especially with modern cameras which have small pixels. Take a step back, read as much as you can and ask away here on SGL. Olly

In Photoshop I had more or less settled on the extraction of a stars-only layer for putting back onto the fully starless, highly stretched image. However, I had an image which wasn't playing nicely this way so I tried the following. Standard linear stack, partial stretch till stars are about where I'd want them at the end. Copy Layer. Run StarXt on the top layer. Further stretch and sharpen and generally process the starless till all the faint stuff is pulled out and details are sharpened, etc. Change the blend mode to lighten. When you do this, only the stars are visible from the bottom layer and, using levels, curves, contrast, etc. on that bottom layer you can manage the stars as you wish. I've now done this on my last three images and have found it to give a very clean, natural result. In a sense the stars in the final image have never been removed from it, they have always been present in the bottom layer. Olly

Not eye-candy targets but, if they're there, we wanna see 'em! As usual, scope driving and pre-processing, Paul Kummer. My post processing. These lie just above Orion's head. Getting deep into the dust is pure RASA. What a great instrument. The objects closer up are really rather nice. Big image here: https://ollypenrice.smugmug.com/Other/DUSTY-DARK-AND-MILKY-WAY-TARGETS/i-TmRrRLw/A Olly

Exactly. I have been a long term advocate of mono for speed and flexibility. I'm not persuaded that there is much gain in resolution, the debayering algorithms being as good as they are. I am now blissfully happy imaging with two OSC CMOS cameras but both rigs are F2. It they weren't, I'd be missing my mono. I work from a seriously dark site, too, and with lots of clear nights - so a clear, moonlit night is not exasperating! Olly

The only mechanical variable I can think of is balance. On the other hand, your flips will be performed later in the night, by which time the seeing is very likely to have improved. Have you tried taking a short-term RMS just before the flip to compare with one of the same duration just after it? Your pre-flip RMS may have a lot of earlier-evening bad seeing built into it. Just a pointer to the fact that round stars, of themselves, say nothing about guiding precision other than that errors in RA and Dec are equivalent. If they are both large and equivalent you will get round stars and lost detail. We actually had this while setting up our first Mesu. Olly

It will give you a decent result even if not an absolutely optimal one. There are so many other things that come between the imager and the perfect image that this won't be the biggest deal on the table. I would say that the best regularly attained RMS for the EQ5/EQ6 will be about 0.5 arcsecs. Someone will have got below that, I don't doubt, but 0.5" is very good for these mounts. How much improvement, if any, would come from a longer FL guidescope? Who knows? It won't be much and it might be nothing. Olly