Telescope Reviews: Saturn and stuff - Canon A590 P&S cam's 1st light

Congratulations on your Moon shots, they look nice.

Regarding A590 settings for single exposures:

Set camera dial to "M"/Manual, push the center "Func. Set" button, then press the down/up buttons on the function set cross to scroll through the various options. There you can change the ISO setting from 80 to 1600. Most of the time I use ISO 800 to 1600 for single exposures.

While in "FUNC. SET" scroll down two items down from the ISO settings which is the "Drive Mode". Set it for "10" seconds, or "2" seconds (these permit vibrations to dampen out before the shot is taken) or multi-frame (the one that shows three frames) this permits multiple frames, but the automatic dark frame subtraction is shut off when using this mode (which is valuable for removing noise in DSO shots.)

Moon - if you are doing single exposures, always keep the shutter time below 1/25th of a second. If the Moon is bright enough, 1/60th of a second or shorter is even better. Indeed, during every session you'll want to adjust the exposure time to the current view. Exposure time is dependent on the Moon's phase, aperture of your scope, whether you are looking at the terminator etc. (i.e. how much white/light is visible in the field of view.) Unless the Moon is a crescent, you should be able to fiddle with the ISO, but if you are just starting out, I would just set it at 1600 or 800 and fiddle with the shutter speed first.

Planets - It appears from your signature line that you might be using a 10" non-tracking dobsonian telescope. This can be a challenging issue for the planets when trying to magnify them and keep them in the field of view for a video stack (the preferred method of shooting planets).

Video Mode - Video mode is the preferred method for shooting the planets. It permits signficant improvements in the signal to noise ratio of the target object, when used in conjunction with stacking software. If you are going to use the Canon A590 for planet shots in video mode, keep the quality level at it's highest, "Stanard" 640x480 mode, consider turning off the Image Stabilization (IMO it might introduce camera processing errors that could show up later in a stack of hundreds or thousands of frames.)
Video clip durations for planets (if you are using a tracking mount) for my 8" scope are in the neighborhood of:
Mercury = any duration clip, but I'd keep it under 2 minutes for manageability.
Venus = any duration clip, <2 minutes for manageability.
Mars - 1-2 minute clip.
Jupiter = 90 second clip.
Saturn = 2 minute clip.
Uranus = Whatever you want.
Neptune = Same as Uranus.

Manual Focus - Hit the "MF" button to access the focus controls and set it to "Manual Focus". Then push the right cross button next to Func. Set to set it at Infinity. This is very important, if you do not do this, the camera will often mis-judge the focus or constantly keep adjusting it (and mis-judging it.) While in Manual Focus at Infinity, adjust the focus on your telescope's focuser knob while looking at the viewscreen of the camera. Fly in and out of focus until you 'feel' the center of focus between your fingers and your brain (it's sort of like timing it, hard to explain, you just have to do it.) You may have to reset the Manual focus between each clip (it's a pain, but IMO a necessary evil.)

Although video mode is very preferred over single exposure for planets, if you can only do single exposures, the trick is to strike a balance between the shutter speed and the ISO setting. IMO, when first starting out, leave the ISO at 1600 and fiddle with the shutter speed first. Each object has different requirements. Considering that you might be using a non-tracking mount, I believe that you need to keep the shutter speed at 1/25th of a second or faster to minimize smudging from Earth's rotation.

SINGLE EXPOSURES OF PLANETS - Not many people are posting single exposures of planets these days, but if you just want to bag a few of these for the fun of it, these are estimates for single exposure's of Planets with the A590:
Mercury 1/30th to 1/60th of a second (phase dependent, better to do video mode on this very difficult object, and shoot during the daytime when near zenith and furthest from Sun, a neutral density filter can be of use too.)

Venus 1/60th of a second or even faster (phase dependent and filters usually necessary, consider getting a UV pass filter for this planet, but if you can't, throw every other filter you have at it. Wait for greatest elongation from Sun, or better yet, do it during the daytime when it's crossing your local Meridian, at greatest elongation from the Sun.)

Mars 1/25th of a second or faster (blue filters will show ice caps better, however neutral density filters are probably best for overall color.)

Jupiter 1/25th of a second

Saturn 1/20th to 1/10th of a second

Uranus 1 second

Neptune 1.6 seconds.

Sun - using an Orion glass solar filter, video mode with addtional moon/neutral density filters is best, but if you have to use single exposure, 1/500th to 1/800th of a second exposures are a good place to start.

Comets- 10 to 15 second exposures, ISO 1600.

Meteors - set camera shutter to multi-frame (I use a clamp to very gently hold down the shutter button while in multi-frame mode), set for 6 second exposures (no telescope or tracking mount necessary), ISO 1600 and at the widest optical field of view (don't worry, you can still get detail because it's an 8 megapixel camera.) Here's a recent meteor I caught at the peak of the Orionids
http://setisociety.org/meteorat125IMG_0579.jpg
and here it is again relative to Orion
http://setisociety.org/MeteorNearOrionIMG_0579.jpg

M42 Orion - 15 seconds, multiple frames stacked, ISO 1600.

Globular clusters and Galaxies, 15 seconds, ISO 1600, multiple frames stacked.

Good luck, Jason Higley

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Criterion RV-8 and RV-6 (8" & 6" '70's newtonians) and a bunch of other scopes.
My astro-images taken with point-n-shoot cameras , my SETI website: http://setisociety.org

Edited by Jason H. (11/04/09 03:15 PM)