Canon 30d for astrophotography

[crosswire80]

I have a chance of getting a used canon 30d with its kit lens etc.However, im new to a DSLR world and wondering if this is a good enough camera for astronomy picture taking.I have a telescope at home too.

 

[padraighaz]

You need to be very careful of your expectations when it comes to photography and I say this because your post is setting off some alarms for me.

A 30D is probably a good camera for this purpose. I have a 20D and there has been considerable discussion over the filter that protects the actual detector reducing red sensitivity. This is a huge issue for astrophotography since many of the most interesting nebulae glow using hydrogen light which is intrinsically red, hence the off the shelf 20Ds don't see them well. You can pay about $500 to have the 20D filter changed or you can buy the 20Da which has this and some other mods for astrophotography. The same issues might apply to the 30D which is why I mention them.

You say you have a telescope at home. You didn't say you have done astrophotography with your telescope at home. Most people don't realize that typical home telescopes are next to useless for photography. You might get a shot of the moon but that's about it. Most people don't realize that astronomical nebulae are so faint that decent pictures demand time exposures and these in turn demand a stable, non-shaky mount, that can track the motion of stars - otherwise you'll have streaked stars. At high magnification, the problem is worse. Astrophotographers get around this by having a second high magnification telescope - usually with a CCD detector that can feed correction information back into the main telescope driving mechanism. So, having a telescope with an adjustable drive that can support the weight of a guide telscope with a guiding CCD is also a requirement. This is a fairly expensive set up and unless your scope cost more than a few thousand dollars it won't work for deep sky photography.

Small telescope can be used to get a few images of brighter objects, but their ability to capture faint objects is totally dominated by the lens aperture. If the mirror is less than 8 inches (with some exception for specialized cameras) you're wasting your time buying a 30D to work with it; the 30D is probably overkill by orders of magnitude.

Astrophotography is an extremely specialized art and is very expensive. In my opinion, the camera is only about 20% or less of the outlay to begin to get images that are good. Magazines like Astronomy, or Sky And Telescope show the work of people who dedicate their lives to this niche, and their wallets. My impression is most of the great published astrophotos from amateurs are coming from $10k set ups at a minimum. When you do astrophotography, you will end up judging your results with published ones, and you might be frustrated that for the most part the main difference is equipment and investment. Good/expensive equipment won't guarantee great photos, but it is extraordinarily difficult to get great astrophotos without it.

One thing about astrophotography is the sky doesn't change all that much; stars, galaxies, nebulae just don't vary much on human timescales - with obvious exceptions like supernovae, variable stars etc. What this means is there are hundreds of thousands of photos of the same objects out there - the Orion Nebula, The Andromeda Galaxy, The North American Nebula etc. These are the brightest of the deep sky objects. The sad truth is unless you want to spend a fortune on equipment, your best efforts will be another so-so average Orion Nebula photo. To me, this is very different than the variety of opportunities available with normal photography - children's expressions, lighting, building illumination, landscapes, clouds, have considerable variation and so there are opportunities for photos to stand out because of content and composition, even when taken with modest equipment. This is just not tru for astrophotography in general - again with some exceptions.

Astrophotography is a blast to try and learn, but it can be very frustrating, and one needs to be aware of the limitations of their equipment. A 30D is not an inexpensive camera, but unless you have at least 3 - 4 times as much invested in telescopes and other devices, astrophoitography does not really justify the expense of buying a 30D iin my opinion.

 

[LDunn1]

Canon launched a special 20D specifically for Astrophotography - From memory the std 20d had an infra red filter permantly attached to the sensors surface to improve general photography results. The special version they launched removed this filter to significantly improve exposure times when catching the night sky.....it is more sensitive to IR without the filter. I am not aware of any special version of the 30D, but I have not looked recently.

You want shorter exposure times to reduce risk of 'hot pixels' for one.....these are individual pixels that effectively give too strong a signal during long exposures & appear as Red, green or blue 'dots' in long exposures of the night sky.......turning up iso can make the problem worse for the same exposure time.

When I bought my standard 20D I tried some night sky shots with my long lenses but exposures were limited to about 10 secs (no equatorial mount to track night sky movement). I noticed these hot pixels & investigated on the web further (this site was helpful).

I learnt that there was a free program called starzen which analysed black frame images for dead & hot pixels (black frame = take long exposure shot with lens cap on in dark room)

I checked my results against those of oter posters & used similar settings.....by initial 20D seemed one of the worst for hot pixels - so I got a replacement & re-ran tests.........4 or 5 bodies later I found one that gave me slightly better than average results. Interestingly there were no dead pixels on any of the bodies.

by long exposure I mean between 1 sec up to 1 minute......hot pixels start becoming an issue at around 10-20 secs depending upon iso....& how lucky you are.

A cold night helps too as the sensor takes longer to heat up while the exposure is being made - hot sensors make the situation worse apparently.

I documented my starzen results on here - don't know if you can still pull them up or not - it was shortly after 20d was launched around the xmas time of year.

......you probably already are aware but your telescope will need a motorised mount to track night sky objects.......you should beable to get ok-ish near full frame shots of full moon with exposures that dont give too many hot pixels or blurring from night skys relative movement, but dont expect wonderful shots of crab neabular in 15 sec exposures......not without stacking 100s of exposures anyway.....

Google 'barndoor astrophotography' for details of home made motorised mounts if you do not have one.

Hope the little I have learnt on the subject helps you.....there was one final point, but it escapes me for the time being!