Starwiz

I was undecided about that myself. Perhaps I need to expose for longer with the RGB stars to bring out the fainter ones. John

I've just looked at the image on my phone and it does looks way too high in contrast, whereas on my laptop it looks fine. I'll have a look at checking screen calibration. John

Thanks. Imaging done over four nights last week. Ha = (44 x 200s bin 1x1) + (138 x 90s bin 1x1) OIII = (22 x 200s bin 1x1) + (38 x 150s bin 2x2) SII = (41 x 200s bin 1x1) + (40 x 150s bin 2x2) RGB for stars = (70 x 7s bin 1x1) for each filter. Darks, Flats & Dark Flats = 20 x for each subset. A subset of the Ha was used for luminance - I selected all the frames that scored above 1600 in DSS. Camera = ASI1600mm-Pro cooled to -10C. John

And here's the result...... John

My second narrowband image. This time I've tried removing the stars before processing the colour, then adding the stars back in RGB at the end. Feedback/comments for improvements welcome as always. John

Very nice Carole. John

Thanks all for the help. I'll give it a go in PS. John

Can anyone direct me to a tutorial that shows how to replace narrowband stars with RGB? I've searched but can't find what I'm looking for. Thanks John

I'll have to add beer to mine then. 🍺 John

That's great work you're doing! John

Great start msacco, you're on your way! John

There shouldn't be any difference. If you focus on something on the horizon, it's effectively at infinity as far as the camera is concerned. So, it will just be a matter of getting the exposure right and tweeking the focus. John

You could always try some daytime experiments to get an idea where the focus is. Point your scope at something on the horizon, then try focusing using live view. With all the extra light, you shouldn't have a problem seeing something with live view. Once, you've confirmed it can actually achieve focus, then try again on a clear night. John

As I understand it, you shouldn't need a light pollution filter for the RGB component, as the filters deliberately exclude the band of sodium light between green and red. Luminance may benefit from a LP filter, but I've no experience on this. I'm using the 31mm unmounted filters and also have the Ha, OIII, SII for narrowband. John

I've only recently started with an ASI1600mm Pro myself, using the ZWO filters. It's recommended to place them as close as possible to the sensor to help reduce vignetting. I don't use a field flattener, so can't comment on this. I know ZWO have made some improvements recently, to reduce light leakage at the edges of the filters if I remember rightly. John

I like it. John

Plumb71, You've posted in the 'Getting Started With Imaging' section, so if your intention is to starting imaging, a Dobsonian is not the best choice. John

If you are not auto-guiding, then your exposure time will be limited before you start seeing star trails. Maximum exposure length will depend on how good your mount is and how well it is polar aligned. I can't say what it will be with your kit as I have the 200p on an NEQ6 mount. Maybe someone else can comment? So, you'll be better off taking a lot of shortish exposures, then stacking these. I would experiment by taking different length subs, then examining these before you start your main imaging run. You might want to start off as I did, by imaging some of the brighter DSOs, such as star clusters and planetary nebulae. John

You can use a single camera as either a guide camera or for imaging, but not both at the same time with the same camera. You could have the ASI290mm Mini being used for guiding and the ASI290mc used for imaging if you wanted. I can't see a problem with that, and you could always swap them over if you wanted to try some mono imaging. John

I use an ASI120mc with an Orion Mini Guide Scope for guiding a SW200p on an NEQ6 mount. It seems to do the job, so I wouldn't think you'd have a problem. John

I bought the ASI120mc myself to start planetary imaging and was using this before I got a DSLR. Another benefit is the download speed of the images. Because the sensor is quite small, the image size isn't very large, so frames can download to the computer much faster. I was getting around 40 fps downloading, but it can vary depending on the image size you select. I would capture around 1,500 - 2,000 frames, sometimes more, before stacking. Now I mostly use the ASI120mc as a guide camera, but I could switch it back to planetary at any time if I want to. John

Thanks. I got it working. I decided to use the drift alignment tool in PHD2 as although I can see Polaris from my terrace, it means assembling the scope too close to a wall for comfort. Once aligned, I use CdC to slew to the chosen target, then do a platesolve, sync and goto using the APT Point Craft tool, which platesolves again when it reaches the object. Very similar to the process you've described, but using APT instead of Sharpcap. John

Histograms is on the Tools tab. John

I read somewhere recently (can't remember where), that the step increase in benefit becomes less the lower the temperature you go. So, although going from -10C to -15C gives a reduction in noise, the step improvement isn't as much as you would see going from -5C to -10C, for instance. I've settled on -10C out here in Malta, at least for the summer. 😎 John

The Histograms tool in APT allows you to auto-stretch the image. I've found this really useful after going from a DSLR to the ASI1600mm-Pro. With the latter not stretched, all I can see are a few stars in the image and even less when on live view. The images shown are of the same Ha sub, with and without the APT auto-stretch applied. John