wimvb

Street lamps are not point sources, ie they have a form and size. For proper collimation you should ideally use a light source that is a point source in order to resemble a star. One way to do this is to use a reflecting sphere near the light source, and use the reflection as the artificial star. A disassembled ball bearing or christmas ornament will do fine. Chrome details on a parked car will also work.

These cameras are also used for microscopy, where Ha response is not an issue. Maybe RisingCam first developed cameras for microscopy, but has now found a market in astrophotography. Their technology simply hasn't caught up with different demands in each sector. Maybe.

Most IR blocking windows have their cut off at 700 nm, past the Ha line. The worrying bit is that Ha sensitivity of the RisingCam cameras may depend on the (lack of) quality control at the camera manufacturer. If they have variation in their coating process, some buyers end up with good Ha sensitivity, while others get lousy Ha sensitivity. It will be the toss of a coin. I would like to see the spectral transmission curve of the IR block window before commiting to that version of the camera. One could of course go for the camera with the AR coated window. But that camera can possibly get problems with IR light making its way to all pixels, which would interfere with colour balance. (Colour pixels have a similar response to long IR wavelengths.) Here's a typical example of the spectral response of an OSC camera. This may not always be a problem, but personally I would prefer an IR blocking filter blocking everything above 700-750 nm, unless doing IR photography.

Interesting thread. @wsteel33 does your camera have an AR coated window or the IR block window? RisingCam specifies the IR block window to have transmission up to 650 nm, which is just below the Ha line.

That's a very nice looking elephants trunk. 👍🏽

Glad you like it, Göran. It seems to me you got more detail in the main galaxy. I had to throw out a large numer of subs due to poor guiding. In the end I decided to create a synthetic luminance image from the combined LRGB data, excluding everything with too large FWHM and eccentricity, and setting a weight on every sub based on FWHM and eccentricity. Today I will recollimate my Mak-Newt. Something you won't need to do with a refractor.

Ngc 4725, ngc 4747 and ngc 4712 are three galaxies in Coma Berenice. The larger of these (ngc 4725) is a Seyfert 2 galaxy, located about 38 - 50 million light years away. This galaxy is about the same size as the Andromeda galaxy. Equally far away is its companion ngc 4747 which shows signs of a violent past. The smaller galaxy ngc 4712 is not bound to the former two. This is an emission line galaxy, some 200 million light years from us. If you draw a horizontal line from ngc 4747 and a vertical line from ngc 4712, at the intersection of these lines is galaxy 2MASX J12494045+2546186, at about the same distance as ngc 4725. Half way between this small galaxy and ngc 4725 lies a galaxy cluster. Its largest member LEDA 1745311 (just a small reddish smudge in this image) is at a distance of 2.4 Billion light years and is roughly the same size as the largest galaxy in this image (ngc 4725). Data for this image was collected last April with my Skywatcher 190MN and ZWO ASI294MM. Total integration time was about 5.5 hours.

Your flats are overcorrecting. This can happen if lights and/or flats don't have a proper dark correction. The proper workflow should be Calibrared Light = (Light - dark) / (Flat - bias) For a dslr you can experiment with using a bias in place of a dark. (For a cmos camera you need matching darks.)

So, very likely there is ERE around M33 as well. Fancy a challenge? 😋 (I can blame lack of astro darkness for another month or so)

To test for linearity, you need a fixed light source (flat panel?). You then take a series of exposures with increasing exposure time and measure and plot the ADU count. At short exposure time there is a floor, which is dependent among other things, on the offset you set in the capture software. At long exposure time you reach a ceiling, which is saturation or full well.

Of course. I was thinking you could deBayer the flat to see if it has a colour bias.

Excellent capture Peter. The red isn't actual Hydrogen-alpha emission, but so called extended red emission from interstellar dust. Small particles (molecules rather than hydrogen atoms) absorb high energy light from (stars in) our galaxy and re-emit it as lower energy red light, a process called photoluminescence. The spectrum of this emission is much wider than Ha emission. (So a wider band nb filter should capture it better than a narrow nb filter.) https://iopscience.iop.org/article/10.1086/305571/fulltext/ One reason we normally don't see it in images is the way we calibrate colours. Unless done very carefully, PixInsight background neutralization for example, would obliterate it. The emission is extremely weak.

Automatic switching is a ZWO "feature". Altair Astros 26M (imx571) also has two modes which the user has to choose. (Have a look at the graphs). The camera driver must have a switch for this. https://www.altairastro.com/altair-hypercam-26m-aps-c-mono-camera-16bit-7974-p.asp

Have you looked at your deBayered flats? They can have a colour bias. A minor colour bias shouldn't be a problem, but it shouldn't be too strong (what ever too strong means).

According to the caption of the graph it has, but apparently it is always turned on. I'm a bit sceptic about the numbers in the graph. The FW is less than ZWO's value in LCG mode, but still there's a dynamic range of 14 stops, due to an incredibly low read noise of less than 1 (e? ADU?)

I’m following this discussion with interest. My concern with a non branded or rebranded camera would be compatibility with software. And yes, things like amp glow and noise are camera dependent. If I remember correctly, only a few years ago, both ZWO and QHY were struggling with amp glow. ZWO got their cmos cameras out first, but with amp glow. QHY lagged, but when they came out with theirs, they were marketed as amp glow free. Same sensors. I believe that part of the amp glow reduction that QHY applied was inactivating certain circuits on the sensor during exposure, as well as having a memory buffer. ZWO added a buffer later on, in their ”pro” models.

As the saying goes: ” it’s not a bug, it’s a feature.” glad you got it solved.

One thing occurred to me: during the second longer run (19 minutes), when the guide graph just wanders off, does the mount stop moving there? I'm not at my computer, so I can't check. But you should be able to calculate a tracking rate. Rate (arcsecs/sec) = pixels/sec × pixel scale (arcsecs/pixel). If this equals or is close to 15 arcsecs/sec, it means that the mount stopped moving.

I had a look at your guide log. The good news is: you're getting good at polar alignment. The bad news: the log doesn't give any new insights. The mount has a large periodic error (at least 50 arcseconds peak to peak), but that guides out very well. As you wrote, after some 10 - 15 minutes the mount just wanders off, and guide pulses have no further effect. My first thought when I saw the graph was; perhaps something is gradually working its way free, but because the pattern repeats with the next guide period, you would have to fasten whatever that was, and you'd know it. I also briefly thought that dew might have something to do with it. But the same goes here; because it repeats, the dew would have to be away for a while. Next time out, you could try letting the guide assistant run for some 20 minutes, just to check if the mount veers off again. Other than that, I'm out of ideas. But, if you have the possibility, take an image of your gear and post it here. Maybe that will turn up something.

Hi, and welcome to the bottomless pit that is wonderfull world of amateur astronomy. If you want to start in astrophotography, make this your first investment https://www.firstlightoptics.com/books/making-every-photon-count-steve-richards.html As for a setup, focal length isn't the most important aspect of a telescope. For someone starting out in deep space astrophotography, I would almost recommend not to go over 1 000 mm in fl. There are plenty of objects in the sky that more than fill a full frame sensor at a focal length that is shorter. And longer fl telescope are difficult to manage for a beginner. Have a look in the imaging sections of this forum to get an idea what people are using.

I use SD formatter. I'm not at my computer right now, but I believe it's an older version of this https://www.sdcard.org/downloads/formatter/ I can check tonight, when I'm home again. Btw, if the card works in the asiair, it's not corrupted or damaged. And it shouldn't be the cause why the log file wasn't saved. But definitely try to replace it. Any sudden movements, noise or sound, star hopping on screen, etc. At one time, my guiding misbehaved whenever I moved around the rig I was babysitting. Vibrations moved through the ground when I got too close to the mount. I moved the rig from the patio to the lawn, where I drove fence anchors into the ground for the tripod to sit on. I also made sure never to step close to a tripod leg. Don't assume anything when troubleshooting, work methodically and keep an open eye to details. When the error occurs, you should see the guide star suddenly move on screen.

The MN190 has a low profile focuser, and in order to achieve focus in visual mode, Skywatcher decided to put an extension tube inside the draw tube. This extension is the part that usually causes problems. You can shim it to make it more rigid. I put a small strip of aluminium tape along the tube and then pushed it back in. This fixed the extension tube inside the draw tube.

Testing on a laptop is a good idea. If the problem persists, it must be something mechanical. I would babysit the gear during such a test, and check everything when RA starts to misbehave. Unfortunately, I don't have any further ideas at the moment.

If you need help with specific problems, and not just general tips, you really need to provide us with a guide log. I can also recommend phd log viewer. https://openphdguiding.org/phd2-log-viewer/

You can have stiction/backlash/binding in the gear box. Even belts which don't have proper tension, can cause guiding problems (in case you have a belt modded mount).