a55 and ASTRONOMY

[OneGuyKs]

http://forums.dpreview.com/forums/readf ... d=36714057

looks like it works fine. All the "ghosting" issue turns out to be nothing serious.

[Greg Beetham]

Nah it's not serious, if you aren't serious about accuracy that is. If you were looking for NEO's or comets each night you'd certainly have some work to do with that camera crossing off all the false ones after comparing the photo with star charts, by the time you were certain that you'd found an asteroid on a collision course with earth using that camera we'd all have joined the dinosaurs.
Greg

[Neonsquare]

@Greg
So where on that posted image are all those ghosts you see?
Me thinks you are a bit overly critical here**.

**)
Which doesn't mean that I think the A55 would be a good choice a astronomy camera, I just start to feel that some are hunting witches and not ghosts here .

[Greg Beetham]

The camera design seems quite ok for general use (except I haven't seen how one is supposed to clean the inclined thingy yet), but for serious astronomy it's not the camera I would use; if there is any artifacts produced by the camera in a sky search they 'could' mask the existance of a real threat.
I'm not saying that it's highly likely an incoming could hide behind one of those artifacts but the possibility does exist; and the camera did produce quite a few faint doubles in the Lyra constellation photo that don't actually exist in real life; so that's it for me it's useless for serious astronomical work.
Greg

[David Kilpatrick]

It is also not much use for sunsets - most lenses produce a large flare patch, created by the internal design not the lens of course. Some pictures work, depends on where the sun is placed. Others have flare spots. The NEX-5 is very good for being flare-free, the A55 is the reverse.

David

[mike2008]

The camera design seems quite ok for general use (except I haven't seen how one is supposed to clean the inclined thingy yet), but for serious astronomy it's not the camera I would use; if there is any artifacts produced by the camera in a sky search they 'could' mask the existance of a real threat.
I'm not saying that it's highly likely an incoming could hide behind one of those artifacts but the possibility does exist; and the camera did produce quite a few faint doubles in the Lyra constellation photo that don't actually exist in real life; so that's it for me it's useless for serious astronomical work.
Greg

Serious astronomical work would require a dedicated low noise monochrome CCD camera with filter wheel, you wouldn't be doing any serious work with a dslr in the first place.

[mike2008]

It is also not much use for sunsets - most lenses produce a large flare patch, created by the internal design not the lens of course. Some pictures work, depends on where the sun is placed. Others have flare spots. The NEX-5 is very good for being flare-free, the A55 is the reverse.

David

Have you any examples of this to share?

[Greg Beetham]

Glad too hear that you know all about astrophotography there mike2008, do you have any good pix to share?
Greg

[mike2008]

Glad too hear that you know all about astrophotography there mike2008, do you have any good pix to share?
Greg

I use ccd cameras + filters to image gases, essentially making them into low resolution spectrometers. The pictures are very boring, so I won't share them here. I based the design of the instrument I made on ccd cameras used for astronomy, so I went a little bit into the details there.

Don't get upset with me, please. It's simply the case that DSLR's with their Bayer filter are ill-suited to serious astronomical applications, certainly any kind of quantitative work would be very hard. They're quite good at taking pretty astro pictures though... But then, so is the A55

[David Kilpatrick]

It is also not much use for sunsets - most lenses produce a large flare patch, created by the internal design not the lens of course. Some pictures work, depends on where the sun is placed. Others have flare spots. The NEX-5 is very good for being flare-free, the A55 is the reverse.

David

Have you any examples of this to share?

Here is an example. This is with the 18-55mm and no filter, of course. The patches may not seem all that bad to you, but they are not lens-flare of the usual type, being a different shape and clearly caused by internal reflections in the camera body - perhaps between mirror, sensor cover glass, and AF module, and lens - who knows?

[David Kilpatrick]

Here is another example - as you may realise, I've been seeking out some very tricky subjects (metering is great, ignores anything like this entirely). The EVF view is incapable of handling the contrast. Mostly, you do not even think there is sun in the picture; the area becomes a plain greyish white with no detail. This flare is not like any lens flare you'll ever see. It is definitely an internal reflection.

[mike2008]

This flare is not like any lens flare you'll ever see. It is definitely an internal reflection.

Interesting. Did you find this in every shot with direct or strong reflected sunlight, or is it more occasional? I've seen a few sun shots and don't recall seeing quite such dramatic flare before, e.g.:



I look forward to seeing the complete review, it will be very interesting I'm sure.

[David Kilpatrick]

It depends on the position and strength of the sun, and the composition, and what is in the background. I've got some usable shots with no flare patches, others with very strong patches - and of course, there are also potential flare patterns from each lens. All I can tell you for sure is that under some conditions flare will be created which would not occur with a conventional DSLR using a well designed darkchamber.

If you are using the camera yo will already be aware of the issues when shooting sunsets or contre-jour - you must judge the scene by eye, and not rely on the EVF providing a 'preview' of the actual picture.

Our daughter was amazed to see the quality of shots taken with the A55. She said this about the EVF - 'It is like looking at someone's very bad home video'. She thought most of her shots would be very poor, in fact they are colourful and stunningly sharp. The camera simply fails to communicate that through the EVF.

David

[mike2008]

Better to have a positive surprise than a negative one

Regarding sharpness, perhaps the lack of mirror flap helps to reduce the vibration even during handheld shooting, when MLU is not usually employed. Perhaps the DSLT design is better suited to getting the most out of high pixel density sensors compared with DSLR, thanks to this reduced shock.

[Greg Beetham]

Personally I don't do astrophotography myself because basically I don't have a very good tracking mount; I have friends in the astronomy club who do though and some use DSLR's and some use SBIG's. Like you say you can take some nice fine textured photos with DSLR's of extended objects like nebula and galaxies.
There is one section of astrophotography that you could never have too many people doing; finding moving dots (the undiscovered ones), you take and compare a photo of a small section of sky against the one taken the night before of the same area to find any tiny dots that moved in relation too all the other dots. (none of the dots should move, but if any do it could possibly be trouble, you stay clear of planets and their moons of course).
I wouldn't be worried about using a standard design DSLR (and stacking with a large scope) instead of an SBIG, not from the results I've seen anyway.
I would worry about depending on a camera like the A33 or A55 too provide accurate results though; even if they 'might' be ok at doing that just the same, after all most of the dots in the field will be hundreds of times too faint to be seen with the naked eye and unlikely to produce the overexposed ghost effect, thing is, there is often a couple of mag 10 or 11 stars in such a field of mag 15 or fainter stars that could produce unwanted problems.
Doing something like that is difficult enough as it is, you don't need additional unnecessary problems.
Greg