Well, I have shot some photos of the milky way with my Nikon 50/1,2 on a Canon 5D Classic. Are you doing wide angle or telephoto photos of the Milky Way? If you are doing wide shots, I'd recommend a 5D II and either the Canon 24/1,4 or the Rokinon 24/1,4 version. It will be very fast, so you can capture the photos with relative speed. Those cameras will also enable you to use ISO 1600+ without giving you a serious headache later in processing.
Best is a tracking mount - period. No (commercially available) camera can deal with astrophotography as well as "any camera" on a tracking mount. That in combination with generating your own dark field images for noise removal and just about any 2009/10 or newer body will do. Doing this you can expose as long as you like using the more desirable base ISOs.
For wide field (28mm on a FF camera qualifies!!!) it probably doesn't matter as much and you can safely grab the 15 to 20 second ISO 800-1600, exposures ya need without too much (noticeable) streaking. But I guess for 100mm (FF equiv) and longer there's no getting around the need for or at least the extreme usefulness of, a tracking mount.
To get good DSO images using such longer FLs we're often talking about exposure times in hours! The 60Da mentioned above will theoretically reduce those times (for red cloud objects ONLY) by 20% making a typical 2 hour exposure 80min - or a short 1 hour exposure 40min. Both still requiring star tracking.
With a tracking mount, besides needing a RC-able B exposure setting and a relatively noiseless base ISO, it almost doesn't matter what body nor how well it performs at higher ISO settings.
So to answer you question: what ISO / camera combination do you consider optimal for "clean" astro work. I would reply:
Almost any camera, base ISO, with star tracking! "Optimal" without question.
That said a camera with excellent shadow recovery will be better than one which clips shadows when your data is run through the processing steps.
Bifurcator wrote:
Best is a tracking mount - period. No (commercially available) camera can deal with astrophotography as well as "any camera" on a tracking mount. That in combination with generating your own dark field images for noise removal and just about any 2009/10 or newer body will do. Doing this you can expose as long as you like using the more desirable base ISOs.
I don't have much experience with astrophotography myself, but I still see that long exposures are usually achieved by stacking a series of 30s exposures, not one continuous exposure.
I guess I should have specified "digital" vs. film.
I understand tracking in order to avoid star trails ... but how does tracking help to improve noise / ISO relative issues?
NOTE: Tracking device is NOT in the cards for this question / application atm.
I also understand (haven't tried yet) stacking @ 30s intervals as a technique to minimize the effects, but that still doesn't suggest whether it's better to shoot base ISO, 800, 3200 or 1,000,000 as an optimal "trade-off" point @ noise vs. exposure.
I realize that shooting with a faster 1.0 lens than a 4.0 lens will impact your light gathering abilities and typically, ISO can be used to offset glass speed (with its penalty). So I guess the question is at what point (ISO/aperture limit) does one feel compelled to find faster glass than 2.8 @ wide or 2.0 @ tele is necessary for astro work ... in order to retain "clean" images.
RustyBug wrote:
I understand tracking in order to avoid star trails ... but how does tracking help to improve noise / ISO relative issues?
I also understand (haven't tried yet) stacking @ 30s intervals as a technique to minimize the effects, but that still doesn't suggest whether it's better to shoot base ISO, 800, 3200 or 1,000,000 as an optimal "trade-off" point @ noise vs. exposure.
Because a tracking device will allow you to use longer exposures without causing star trails, and it's the length of exposure (not ISO) that principally determines how much noise an image will have. Exposure is defined by how much light enters the camera, thus ISO is not a component of exposure. In fact in most cameras will have less noise at higher ISOs, provided the exposure is the same. This is due to how read noise (electronic noise) is optimized in the sensor/ADC for the gain applied for ISO.
RustyBug wrote:
So I guess the question is at what point (ISO/aperture limit) does one feel compelled to find faster glass than 2.8 @ wide or 2.0 @ tele is necessary for astro work ... in order to retain "clean" images.
Most large aperture lenses suffer from coma at their/near their largest apertures, so that's typically not the best solution.
Yeah, you will find that likely somewhere around ISO 1600 is the sweet spot as for a given exposure most cameras will yield less noise up until a certain point (usually where they switch from analog gain to digital boost).
Cheapest way IMO to get decent astro photos is an AstroTrac on a good tripod and head. Not inexpensive but far far less than a serious tracking mount.
Or you can build a barn door tracker for next to nothing and you should be able to get decent 30 sec exposures as long as your focal length is in the normal-ish range.
Also, as has been mentioned coma is an issue and can really screw up your shots. Check on some AP forums for info on the lenses you are interested in; e.g. the Canon 85/1.8 is terrible for this purpose.
I've been looking into astrophotography and the guys I've talked to all indicate that long exposures start to show more noise because of heat. If it's very cold weather, then this is alleviated. This is somewhat dependent on the camera. The Canon 5D2 heats up quite a bit. If you're not using a tracking device then exposures should be short enough to not have to worry to much about heat induced noise.
The camera, lens, focal length, aperture will all factor into the equation of what's the "best" ISO and exposure.
You also need to know what size output you want. Small prints or online posting would allow for more "lenient" setup, will big prints will mean optimizing your setup to get the best results.
I think a good starting point is the aperture that gets sharp results and exposures in the 20 to 30 sec range. Then select ISOs that yield the best image.
Hmm, interesting. It's news to me that higher ISO gains than base produce less noise. While I haven't tested this directly and exhaustively it's contrary to all of my ancillary findings - on µ4/3 bodies.
I'll have to prove it to myself in order to believe this. Yeah, yeah, I know, stubborn Doubting-Thomas me.
Most of the stacking I've tried and that I've seen on-line that produced any decent results were exposures of between 5min. and 40min. Usually 5 or 10 min. exposures with 20 to 40 exposures total. And of course all these require tracking!
ISO 100, GH1,
I think this is the FD 300L at f/5.6 or f/8 with TC but it might also be my telescope -
I've shot this more than a few times now. Pretty sure it's the FD tho.
GP2 tracking mount and I think these were 20min exposures each.
