ASI120MC - Long exposures for DSOs - AVI, BMP, or what?

julianh72

Apologies if this newbie question has already been asked and answered ...

I recently received my ASI120MC - what a great camera!

I've had some success with lunar / planetary images, and then I thought I'd have a go at some simple DSO targets. I tried firing off some AVIs and some series of BMPs, using a range of frame exposure times in excess of 1 second.

The AVIs that I shot with frame exposure in excess of 1 second don't seem to be able to be opened and viewed with any video viewing / editing software that I have acccess to, including AutoStakkert. However, any AVI video I shoot with sub-1-second frames work fine, but the individual frames obviously only capture the brightest DSO details. Is this a fundamental limitation of the AVI format, or have I done something wrong, or forgotten to activate a particular software option / function? Or should I be using a different video format such as "SER"?

Alternatively, I can produce nice sequences of BMP image using exposures much longer than 1-second, and I am seeing a LOT more detail in each frame with the longer exposures, but AutoStakkert doesn't seem to be able to open and process a bunch of BMPs; it wants a video file.

What is the recommended software chain for capturing and stacking "long" exposures - e.g. 10 to 50 x 30-second frames, say? (Or would I do better with 300 seconds of 1-second AVI say for DSOs?)

I have been using FireCapture 2.3.21 and AutoStakkert 2.1.0.5, but I'm happy to try other software if necessary.

Thanks for any and all comments!

riklaunim

For DS imaging you need a lot (hundreds) of 1-few seconds frames (TIFF, FITS, BMP) as well as dark and flat frame.

julianh72

riklaunim wrote:
For DS imaging you need a lot (hundreds) of 1-few seconds frames (TIFF, FITS, BMP) as well as dark and flat frame.

OK, thanks, yes I realise I need many individual long-exposure frames, and from your reply, it appears that I should use BMP or TIFF rather than AVI to capture the raw images.

Can AutoStakkert process a "stack" of BMP files, for example, or should I look at another stacking software such as RegiStax to process BMP files?

When I tap on "Open" in my copy of AutoStakkert 2.1.0.5, the only supported file types are SER and AVI. I'm probably doing something stupid, but I can't work our what!

Thanks!

riklaunim

It's better to process DS frames with DS stacking/processing apps (to apply dark and flat frame etc.) but still a folder with frames can be dragged onto Autostakkert for stacking.

sgazer

you can use bmp, png, jpg, but they are only 8 bit images. You are much better using 12 bit RAW/FIT images which will give you much better tonal range.

1s exposure will get you very little. For a static tripod, you should be pushing up to 30s, or until the star streaking is bad. On a tracking mount 1-3mins is good.

A single long exposure will show a lot, but multiple exposures stacked in DSS (Deep Sky Stacker) will significantly reduce the noise. The image should then be processed in Photoshop or equivalent.

riklaunim

Sgazer wrote:
1s exposure will get you very little. For a static tripod, you should be pushing up to 30s, or until the star streaking is bad. On a tracking mount 1-3mins is good.

A single long exposure will show a lot, but multiple exposures stacked in DSS (Deep Sky Stacker) will significantly reduce the noise. The image should then be processed in Photoshop or equivalent.

This is not a DS camera but high gain 8-bit camera optimized for fast framerate and not low noise. With a typical DS setup - telescope on an EQ mount such cameras can be used for DS imaging, but in a different way than DSLR or cooled 16-bit DS cameras. 30 or more seconds may give very very noisy frames and in many cases it's just better to collect multiple frames at shorter exposures.

And the exposure doesn't have to be very long to catch all the details of an object it's able to catch. The requirement is to have the signal from the object to be above the signal of camera noise. If thats done then you can get those features nice and visible on the final stack. The stronger the object-signal from noise-signal the better, but not every camera type can do it that easily.