Sharpcap live stacking - alignment issues

[Moonstruck]

I usually concentrate my efforts on planetary imaging, but figured I'd try my luck imaging DSOs. I have a CPC 800 HD Edge telescope with a ZWO asi 224 MC camera. I have the paid version of Sharpcap Pro in order to have complete functionality using live stacker.

But when I tried to live stack, I got a message that the alignment failed. I am pretty sure that is because my asi 224 camera has an extremely small field of view, and the software simply didn't have enough sky to align on. So, I am looking for a camera now with a wider field of view; hopefully that will work better.

For now though, if I continue to use my asi 224, with its tiny sensor and very small field of view, if I uncheck the alignment box in live stacking, will it still allow me to live stack? How good a job will the software do without the alignment function checked?

[admin]

Hi,

for the live stacking to fail to align, it usually means that not enough stars are being detected in the image. You should have a look at the 'alignment' tab in the live stacking area which lets you tinker with star detection settings and also highlight the stars that are being detected so you can see the effects of your tinkering . It's not the small size that really matters - just not enough stars (aim for 10, but 3 or 4 might do in a pinch).

If you do not have the alignment enabled then the images will be stacked straight on top of each other, so unless your mount is tracking with superb accuracy, you will see stars turning into streaks and any deep sky features blurred out.

I might suggest that rather than jumping straight in with a bigger camera, it could be a good idea to try a shorter focal length telescope - a small 200-400mm focal length refractor would give a much bigger field of view with your current camera (and an even wider one with a bigger sensor camera that you might buy later). Perhaps it is possibly to piggy back mount a small telescope on your CPC800? Certainly starting DSO imaging with a 2000mm focal length is doing it the hard way!

cheers,

Robin

[oopfan]

I plugged your numbers in and got this:

Moonstruck FOV M57.png (20.95 KiB) Viewed 1145 times

Yep, that's narrow, but depending on where you are pointing your scope there should be enough stars to achieve alignment with LiveStack. In other words, the Milky Way is best.

Other people on the forum can help you out with settings.

Brian

[turfpit]

From Astronomy Tools FOV, M27 would look like this with your equipment:

M27-ASI224MC.JPG (46.68 KiB) Viewed 1144 times

Not many stars available for alignment. The ASI224 is described as planetary/solar/lunar. A reducer may help, which you can test out here https://astronomy.tools/calculators/field_of_view/.

The reality is planetary and DSO need different scope/camera combinations.

Dave

[oopfan]

If you are in the market for a wide-field scope, look into this:
https://www.highpointscientific.com/wil ... O-L-RC51IX

The benefits are:
1. Weighs only 2.9 lbs, so it can ride on your Edge.
2. Short enough focal length, so it is good for polar alignment.

Here is what the FOV looks like with your ASI224:

Moonstruck RedCat ASI224 M45.png (231.33 KiB) Viewed 1143 times

And if you want a good cooled camera with a wide FOV that won't break the bank: ASI1600

Moonstruck RedCat ASI1600 M45.png (68.66 KiB) Viewed 1143 times

Brian

[oopfan]

Moonstruck,

Forget about the ASI1600. The pixel size is too large for that short focal length. You want something at or below 2.4 microns.

Two suggestions:

Moonstruck RedCat ASI183 ASI178 M45.png (130.46 KiB) Viewed 1140 times

The 183 is cooled and less than a grand. The 178 is uncooled and only about 300 bucks.

Disclaimer: I've never used the RedCat or these cameras, so buyer beware.

Brian

PS: The 178 gives a FOV only a little larger than your 224 with the RedCat, but the problem is that your 224's pixels are FAR TOO BIG for the RedCat's focal length. You won't be happy with the image quality using the 224.

[oopfan]

The following is pretty impressive.

RedCat + ASI183:

Moonstruck RedCat ASI183 M31.png (189.91 KiB) Viewed 1109 times

With my scope and camera, I need a four-panel mosaic to fit it all in.

Brian

[Moonstruck]

Thanks very much! I'm considering getting the RedCat and 183. Looking into ways to piggy-back it on my scope.

[oopfan]

Regarding piggy-back, try to calculate how much extra load your mount can take. I searched for your kit at High Point Scientific and chose the most expensive one: "Celestron CPC Deluxe 800 with Edge HD Optics". I see that it has an Alt-Az mount. I don't have any experience with them, but I know that if I were to purchase an Equatorial mount that they would tell me its "Instrument Weight Capacity". In their write-up of the "Celestron CPC Deluxe 800 with Edge HD Optics" they don't tell me the "Instrument Weight Capacity" just that the OTA weighs 42 lbs. That is pretty heavy, so my first guess is that your mount probably has enough excess capacity to handle the RedCat (2.9 lbs) plus the ASI183 (1 lb).

At AstroBin, I found an image of M31 taken with the RedCat and ASI183MC:
https://www.astrobin.com/r9gqtk/0/
Total Integration Time: only 1 hour 36 minutes

If you zoom in, you'll see that the stars look round due to the small pixel size of 2.4 microns. If you used a different camera with larger pixels, then the stars would look like boxes.

Brian

[oopfan]

You are definitely going to want to LiveStack. The reason is the difference between an Alt-Az mount and an Equatorial mount. There is no field rotation with an Equatorial mount, therefore you can take long exposures. However, with an Alt-Az mount there is field rotation, so you will want to keep your exposures to 1 minute or less. Using 1-minute exposures you are going to chew up a lot of disk space with the ASI 183 if you save every frame, so that's why LiveStack is your friend.

Regarding guiding, you can probably use your Edge + ASI 224. It's a narrow field of view but you should be able to pick up several stars using a 2-second exposure. The nice thing about the RedCat is its wide field of view, so you should first concentrate on finding a suitable guide star with the Edge.

Before making a major purchase, I would learn how to use PHD2 guiding software (free) using the Edge + ASI 224 just to see if you can successfully guide with the narrow FOV. If you can't then you will also need a guide scope which will add more weight.

Brian