ollypenrice

I no longer have an OSC. When I did have mono and OSC versions of the Atik 4000 I did a direct shoot out and article for Astronomy Now. There was precious little difference between the final images but I was imaging M42, a bright target and one not needing Ha. The longer I kept the OSC the more frustrating I found it on faint targets. Tidal tails and extensions in galaxies just took forever and, in the end, I went to dual mono cameras. Unlike Tim I never found OSC easier to process. Rather the reverse, in fact. But there are any number of reasons for this. I still think the double green is an issue for OSC in astronomy. However, Tim's point about 'getting something keepable' is a good one and is, as I said earlier, the real reason for using OSC if that's what you fancy. My real beef is with the speed claim. Olly

Ronin, you trot out this answer every time anyone asks this question and, alas, I don't agree with much of it. Please give some thought to the following points. 1) Mono is more expensive, agreed. 2) The increase in resolution by using all the pixels in a mono is actually trivial. The debayering routines are very sophisticated and interpolate (make an educated guess) about the 'missing' information remarkably well. I advocate mono but not for reasons of resolution because I have found very little or no gain in resolution when using mono over OSC on the same make of chip in the same telescope. 3) You do not need more time with a mono camera, you need less. An OSC camera shoots through colour filters all of the time so it can never capture more than a third of the incident light, ever, under any circumstances. However, when a mono camera is working in its luminance mode it is capturing all of the incident light and obtaining a massive speed advantage over colour. This cannot be less than a 6 to 4 time advantage and can easily rise to being twice as fast. The LRGB system was invented to save time. 4) OSC cameras are filtered for daylight and have twice as many green filters as red and blue. This is entirely inappropriate for astrophotography and wastes more time. 5) OSC cameras use low grade absorption colour filters rather than high quality interferometric ones availble to mono imagers. 6) Mono cameras can capture narrowband efficiently, Ha opening up many nights of moonlight to the imager. A while back I set myself the task of demonstrating the remarkable speed of the mono camera by doing a two hour Heart Nebula. This has just an hour of Ha and twenty minutes each of R, G and B. This was at a FL of 530mm and at F5. I do not believe I could have obtained this result, or anything remotely like it, from an OSC camera in the same telescope in two hours. At some point I'll do a fast LRGB image as well to make the same point. It's been argued that using colour filters adds to the complexity because you may have to refocus between colours. The other way to look at it is that non-parfocality does not come from the filters but from the optics, so at least you can refocus a mono but with an OSC some of your colour will always be out of focus. The genuine reason for going for OSC is that it may be less frustrating in terms of capturing an incomplete data set. But mono is faster. It really is. Olly

You won't need the flattener for the small chip but the colour correction is better with it. On most targets I don't think this will matter. Olly

Assuming Steve's using the TEC flattener the FL of the TEC will be more like 1015mm. It's also worth noting that the TEC flattener almost certainly improves the colour correction in the blue for CCD imaging. I'm convinced mine does, having imaged with and without it, and there was a CN discussion suggesting the same. It was OK without it but there was sometimes some blue bloat on bright hot stars. I'm also enjoying 0.9 "PP with my TEC/460 combination. It seems like a sweet spot and is getting me into the galaxies. On the Moravian/QSI decision I'd be very surprised if you noticed any difference in use. Olly

I don't know, Gorann, but our pair of Tak 106 FSQs produce just two of these dark shadows per bright star, 180 degrees apart. I call them the 'inverse lighthouse beams.' They don't bother me. On anouther forum Prof Greg Parker assured me they arose from slight optical pinching. I had always thought of pinching as producing triangular stars but Greg was confident. Olly

Such artefacts don't normally bother me, but here's one that does. Ignore the image quality, it's just a crop from a test stretch, but the artefact in question is the double spike only in red. In this example the one at about ten o'clock is faint. The one at five o'clock is more obvious. Sometimes they appear as really very bright and thin red lines either side of the star. They arise only in the TEC140 using a camera and filterwheel which does not produce them in the Takahashis. Indeed this example is from a new Atik 460 with different filters, so the effect must be produced by the scope. The lines are always and only in red. They don't afflict all stars by any means, or I'd be a lot more disgruntled. They few that they do affect I fix in Ps. Any ideas? Olly

It was a while before the penny dropped with me, too. Olly

That's true. The other reason is that it makes the image more repeatable if you want to come back to it for more data in the future. It takes ages to recover an arbitrary camera angle when framing. And then there are mosaics. I once tried to do a mosaic with an arbitrary angle optimized to the target. Never again!!! Olly

Dead easy, Steve. Have the camera running on a bright star. Open the crosshairs on your capture screen and put the star in the middle. Now slew slowly on whatever is the long side of the chip (which could be RA or Dec depending on Landscape/Portrait orientation.) Unless you're already orthogonal the star will now be above or below the line of the crosshair so you rotate the camera so that the star is back on the the line. Now 'slide' the star along the crosshair by slewing the other way to the opposite side to confirm it's remaining on the crosshair. Give the camera a final tweak of rotation if necessary. It takes two minutes at most. Olly Oops, beaten to it! As Freddies says, you can't have both optimal framing and orthogonal alignment but I find I hardly ever need to move from orthogonality.

Yes. But, thank God, Monique hasn't... lly PS, Seriously, filters really do start to get expensive in large sizes. The absolute killers are the square ones for the 36X36 chips. If you decide to look (and I wouldn't!) do so while sitting down.

One of our robotic scope owners has just installed a large format Moravian and it looks very convincing. Olly

I'd do a net search on the subject of customer service.

Ha is very deep red and I will always add it to the red channel. I don't like to add it to luminance, which is the lighting across the full range of colours. OK, I may use a whiff as luminance on some targets but it ain't right! OIII lies on the blue-green border (sometimes called teal blue) so I add it to both green and blue but in separate images which I then blend to taste. Others will use different methods. When I add narrowband I have the natural colour image on another screen and try to respect it when adding NB.

I have plenty of problems in processing for full size zoomed viewing, Rodd. It's just that I feel like a cheat if I don't! In this one the big problem was the noise in the colour layer, which is a technology issue, I think. I did far more NR than I'd like to do. I used custom techniques based on zooming in to pixel scale to see what was going on. Since I can find nothing wrong with the cooler on the camera I'll have to look at the usual suspêcts like the USB leads, etc. Olly

It's important to be clear that ALL electronic cameras are monochrome, including DSLRs and 'one shot colour' CCDs. We don't 'colourize' * and we don't invent colour. We measure it. In terms of colour there is no significant difference between a mono and a 'one shot colour' camera in terms of how the colour is obtained. Both use a red filter to block green and blue, a green filter to block red and blue...etc. In a 'one shot colour' these filters are placed over each pixel in a 'Bayer Matrix.' Red, green, green, blue - repeated across the chip. (Why two greens? Because it works in the daytime but is a very bad idea at night!) In a mono the imager shoots through an R then a G then a B in turn and combines them later - but the idea is the same. The same kind of software calculates how to weight the three colours of light. My main point here is to stress that there is no such thing as an electronic colour detector, as yet. They are all mono and they all use filters to work out the real colour. Olly * That is, in natural colour imaging, which is what I do in deep sky photography. I have invented colour from purely mono images in solar imaging. This is always declared. The colour in this image is pure invention:

That's the planetary, Paddy. I don't know if the bright star visually centred on it is the progenitor. I'd be surprized. It seems too bright. Probably line of sight. Olly

I only noticed it in SkyMap when planning the framing. It isn't a popular target, it seems. Here it is with 1.5 Hrs of OIII from guest Ton's own TEC140/GM1000/QSI683 Astrodon. 3x30 minutes, guided. (And with its poor neck wrung in Ps! It shows OIII is the way to go, though.) Olly

Yes, that's the one. In fact our present guest shot 1.5 hours of OIII in his own TEC last night and we've just blended it. It's nicer. I'll update the pic when I get a chance. The SCT project went on 'hold' because the idea was to mount it on one of our robotic guest's mounts, a GM1000, but he had so much trouble with it that he took a refund and is now using an Avalon which is too small for the SCT. However, I have a second Mesu coming next month so I'm aiming to give it a run on that. Actually the ODK data was very soft. I guess it was down to poor seeing but I can't remember. The resolution was much the same as in the TEC data. The problem was poor S/N in the TEC colour because the camera isn't happy for some reason. I like to have equal amounts per channel of L,R,G and B becaue it makes processing easier. However, with the usual Photoshop thuggery you can work with two or three times as much L. I perfer not to when possible, though. There are no ODK stars in this. They would have added spikes. There was no star reduction here other than on the handful of bg ones, which I pulled down in Curves near the end. Olly

LukeBL posted a nice NGC4725 recently. Here it is again in a wide field which includes PNG339.9+88.4, the tidally distorted galaxy NGC4747 and the Sbc galaxy NGC4712. Plenty of faint fuzzies, too. NGC4725 is a barred spiral with prominent ring structure. One of my favourites. I've a suspicion that this camera isn't cooling properly so the colour was a real fight and the Ha I shot last night is scrap. The PN shows well enough in LRGB like this and I've emailed a query to Atik to ask if the FITS header temperature is a record of what temp I set or whether it is a measurement of the real temp. (It was showing -25 but I'm not convinced.) The day was saved by using old ODK14 data for colour in the three galaxies. Once we have the technology sorted the addition of Ha and OIII for the PN would be nice. TEC140 and ODK14. WIdefield L 4Hrs, RGB 1.5 hrs per colour. Similar exposures from the ODK14. Enough excuses, here's the pic! Best seen in the larger size. Click on the image and full size button is lower left. Olly

As I said, I'm not aware of anything to beat DBE. That means what it says - I'm not aware of it. I don't claim that it doesn't exist! I'm not in the business of trying every new bit of software that appears on the market and I suppose that I'm mainly motivated to try new software when I see an image that breaks new ground. If I think, 'How did he or she do that?' then I'll be in there, full of curiosity. I'm hardly a PI evangelist, I'm manly a Ps imager, but DBE is profoundly impressive. If you have an alternative, tell us about it. Give us some demos. I'm all ears, I promise. If there is something out there which is more sophisticated than DBE - great. Olly

Just think about what your imaging hardware costs. It's a lot. Now think abut how much of the final image quality comes from processing. It's also a lot! It's more than a lot, it's going to be something like 80%. You can't process rubbish so the hardware is very important, but a good capture is no more than the collection of good raw data. You still have to do something with it. My captures are no better now than they were ten years ago but my processing is a lot better. DBE in Pixinsight has no rival of which I'm aware. I still think the software giants are PI and Ps. Look at the images 'out there' which you like the most and see how they were processed. Olly

I don't think there is much doubt amongst historians that Hooke did have a role in giving Newton a cenceptual, though not a mathematical, leg up on his way to his theory of gravitation. Of course Newton would never admit this. When Newton said he had seen further because he stood upon the shoulders of giants he was, in fact, taking a swipe at Hooke who was deformed and dwarfish. There's a geat Hooke biography byu Stephen Inwood which I have read and another by Allan Chpman which I have yet to read. Olly

No point in my repeating my enthusiasm for this mount. Hope you're as happy, Harry (and Steve.) Olly

An unusual look and feel to this one. Sh2 126, 2 panel HaLRGB, twin Takashashi FSQ106/fill frame CCD, Mesu 200. The 'Breaking Wave' extension around Gamma Cass, down to the Pacman. 3 panel, twin Taks. NGC 2170 using twin Tak and TEC 140 data. 35 hours. Beverly Hills here we come. A joint effort with Mr and Mrs Gnomus. HaOIIILRGB, 35 hours. And finally IC447, LRGB TEC 140. An eleven hour quickie! As ever, the kit is co-owned by myself, Tom O'Donoghue and Yves Van den Broek. Thanks guys and guests, a good year. Olly

The speed of the system is not linked absolutely to the F ratio rule in AP when using reducers. If you are interested in everything that fills the frame then the rule applies in useful way. If your real target is a small discrete object framed by dark sky which doesn't interest you, then the F ratio rule does not apply. (It becomes the F ratio myth.) The photographic F ratio rule is predicated upon varying the aperture. A focal reducer leaves the aperture where it was and alters the focal length, so it brings in no new light from the discrete object. The two situations are entirely different. I wonder what the effect of binning really is on this CMOS camera. From what I've read it may bring no increase in signal to noise, in which case why bin at all? More homework needed! I like many aspects of the camera so I'd better get studying. Olly