Canon IXUS 100 IS targets

[george7378]

Hi everyone,

I am looking to buy this Canon IXUS (From Ebay or another supplier):

Canon SD780 / IXUS 100 IS Black Digital Video Camera on eBay (end time 08-Jul-10 20:20:16 BST)

Canon Digital IXUS 100 IS Digital Compact Camera - Canon UK

Canon Digital IXUS 100 IS Digital Compact Camera - Canon UK

It has a maximum exposure of 15 seconds, and I was wondering what this would let me image? Will I be able to stack photos of 15 seconds to get star trails and satellite trails, and maybe Milky Way shots? I have already managed some constellation shots with my Dad's camera of the same model:

http://stargazerslounge.com/imaging-widefield-special-events-comets/108158-some-nice-basic-images.html

Thanks.

[sgazer]

I think the main problem will be with noise with a compact camera. I've spent some time comparing my Sony Cybershot HX5 with the Canon 1000d and the noise levels are no-where near close (1000d better of course), even thought the Sony has a clever feature of internally stacking 6 frames effectively dropping the noise by 2.5x.

Having said that, it's definately worth trying as I'm sure you'll get something the more frames you stack. I'm not sure about the Milky way, I recently used the 1000d for this, 18mm, f3.5, 120s ISO200 and it took a huge amount of histogram stretching and curves for the MW to show. For 15s exposures, a higher ISO would be needed, but noise could become excessive above ISO200-400, so you may have to stack a large number of subs. 100 subs would reduce the some noise elements by approx 10x, but there are other noise elements involved due to so many readouts from the sensor. In any case I think a lot of histogram stretching and curves will be required in Photoshop, Gimp or something similar.

Anyway, I'm waffling, definately give it a try!

oh, regarding star trails, there is some software available that will enable you to layer lots of 15s subs effecting combining all the trails into one image, but I can't recall what it is having not used it. I'm sure someone on here will know.

[dph1nm]

I think there is a SD780IS - CHDK Wiki firmware port for this camera, which will give you exposures up to a minute.

You can do lots with compact cameras - they are much maligned on this forum!

NigelM

[Hypernova]

I managed to just about capture the nebulosity of m42 with an ixus 80is with an exposure of fifteen seconds. The resulting image shows star trails when zoomed in and is very noisy and there is a strong orange light pollution background as well.

[george7378]

Thanks for the info - I am definitely getting this camera now. The 15 second exposures gave some nice results (see thread) when I used the camera; I could even see both optical double stars of Epsilon Lyrae with the photo of Lyra I took.

Also, that CHDK sounds great - I have skimmed through the wiki and it seems to be perfect - is it free, and where would I download it for that camera (is it with the link on that page)? Thanks.

[sgazer]

I think there is a SD780IS - CHDK Wiki firmware port for this camera, which will give you exposures up to a minute.

You can do lots with compact cameras - they are much maligned on this forum!

NigelM

I hope it didn't appear that I was maligning (if there's such a word) them . Afterall the Sony Cybershot was quite an investment for me and actually cost more than my 1000d DSLR. Just stating that for deep sky work, the noise is significantly greater than a DSLR, which itself has greater noise than a cooled CCD cam. It's only a fact, I don't believe they are much maligned on the forum. When I'm out and about, it's the compact cam that's in my pocket

[george7378]

Is it possible that the CHDK firmware could damage the camera in any way? Will keeping the shutter open for a minute cause damage (is there a reason they limited it to 15 seconds?). Thanks.

[dph1nm]

the noise is significantly greater than a DSLR

Yes and no. Compacts can have lower read noise than DSLRs, which is important if you are doing lots of short exposures.

For general photography they are noiser, because they collect far fewer photons in a given exposure (much smaller lens apertures) hence higher shot noise. However, if you use them afocally at the telescope this effect is nullified, because the number of photons is then dictated by the telescope not the camera lens.

What they do seem to have, though, is worse thermal noise.

NIgelM

[dph1nm]

is it possible that the CHDK firmware could damage the camera in any way? Will keeping the shutter open for a minute cause damage (is there a reason they limited it to 15 seconds?). Thanks.

I haven't actually used it myself, but as I understand it the answer to the firmware question is no - the modified firmware is stored on the memory card and the hardware firmware is untouched. So to get back to the Canon version you just take the card out.

As for the camera, somewhere on the CHDK forum there is a thread on using modified cameras for astrophotography, so some people are certainly doing it without any problem.

Here's one, there are others. Try searching the forum for 'astrophotography' or 'long exposures' etc:

• Night sky 60 second exposures
  

I think the download is linked to that CHDK page I gave, but I suggest you go to their home page and read up on how to install it.

NigelM

[george7378]

Thanks. I have decided to buy this camera, which has exposures up to 60 seconds by default, and has a dedicated night sky mode:

PANASONIC Lumix DMC-FS10 Compact Digital Camera buy online | Currys

[george7378]

I have ordered a Panasonic Lumix DMC-ZX1 which has exposures up to 60 seconds in its dedicated night sky mode, and a whole host of other nice features. One thing - it is fixed to ISO 80 mode when taking long photos using the night sky mode - why is this, and will there be any implications when taking, for example, a 60-second ISS exposure?

Thanks.