Photographing bright planets.

[pringlepowell]

Hi

I have a new 200pds with HEQ5 and use a Sony NEX-3 for imaging. Been getting some pretty good results with moon, DSO and star imaging but have fallen completely flat with planets. It seems no matter what ISO and exposure time I set the camera to, all I get is a large white blob (Jupiter) and 4 smaller blobs (moons). Even playing around on Photoshop I can't get any detail on the planet due to the amount of light captured compared to clouds etc.

Any idea how to cure this? I've even tried to use a moon filter and light pollution filter in the eyepiece.

[Digz]

I think you will be better off using a webcam to shoot planets. Even then they will be small in the FOV.

Take a look in the planetary imaging section to see what kind of kit people use.

This was taken with my 250p DS and DSLR at 1/40th of a sec

This should give you an idea of where to progress.

[pringlepowell]

Can you remember what ISO you had it set on, and whether you used a Barlow to get an image that size? It used to be fine when I had a smaller Mak-Cass but the 200 obviously lets far more light in.

[Digz]

Mmmm, good question. I have a feeling I did use a barlow, as for ISO ill need to take a look at the exif and get back to you.

A webcam or similar will allow you to take an avi vid and stack which will help get over the over exposure issue to a certain extent.

[FarSide]

Ideally you need a long FOV to photograph planets - 2000mm+ at 9-14 inches in aperture to pick out detail. And yes webcams are brilliant for planetary imaging due to their dynamic nature. You need to be able to photograph potentially hundreds if not thousands of short exposure images and all very quickly - especially when imaging Jupiter which rotates 2 and a half times within an Earth day otherwise you'll encounter smearing (similar to star trails).

[pringlepowell]

So a video would be a better bet? As long as it's in a format that will stack?

[VigdisVZ]

I'm borrowing the thread. How would a DSLR in full HD movie mode work for imaging planets?

[Digz]

So a video would be a better bet? As long as it's in a format that will stack?

Correct - it allows you to get the desired exposure for these bright objects, but also allows you to 'cut' through variations in seeing. i.e. the stacking will take the best frames and ditch the ones where there is too much wobble etc.

I'm borrowing the thread. How would a DSLR in full HD movie mode work for imaging planets?

It might work providing you can get the right file output for the chosent stacking software. The only thing I would say is the chip size will probably be too big. I think my shot above was heavily cropped. Thats why webcams are favoured because of their small chip.

HTH

[Stryda]

I've got a canon 5D, and have tried video recording in HD, but unfortunately (as far as I am aware) DSS doesn't recognise the file format, and this means converting the HD video to an AVI file, which would lose a lot of data, and make the HD quality obsolete. I'm also not sure if converting from HD to avi would produce a lesser quality image/video than a video simply recorded in avi to begin with...

[jimmyjamjoejoe]

You shouldnt lose quality if you convert with the right codec/settings, thought the filesize may increase a little.

[IanL]

The other option with a Canon DSLR is to use something like BackyardEOS or APT to do your imaging. These can record the LiveView mode as an AVI. They also have a 'zoom' mode which effectively uses a subframe setting to stream just a portion of the chip to the on-screen preview and recorded AVI; the only issue with that is that the subframes are fixed sections of the sensor so you have to frame the target appropriately.

The major benefit of this approach is that the large chip size and live preview make it really easy to acquire and frame your target. A lot easier than trying to get and keep a planet on a small webcam chip at a long focal length (I run at 2,000m plus a 2x Barlow). I have found quite a few downsides though; firstly the ISO/Exposure settings appear to be largely simulated in software with the on-chip gain settings fixed (there is some debate about this though). The colours tend to be a bit washed out vs. the webcam I have used previously, you can correct in software but it takes more effort/care in post processing to get a natural looking result.

The response to changing seeing seems to be a bit 'weird' compared to the webcam too, the DSLR movies tend to have a lot more variation in brightness between frames as the seeing blurs the image, whereas the webcam seems to cope a lot better. The biggest issue with this approach is getting a satisfactory exposure level, as the amount of control in LiveView mode is pretty limited. On less bright targets (especially Saturn) I find that the simulated exposure goes straight from too dark to completely overexposed in one step with no ideal setting in the middle.

The other option is just to capture a bunch of standard images (as RAWs), convert and stack them (e.g. AVIStack can cope with multiple individual frames rather than an AVI). It is more work but you have much more control over the exposure. Using a capture tool as described above you can just set it running to grab as many exposures as you need, but the main downside is that capturing and downloading each frame takes upwards of ten seconds. This limits its usefulness on a fast rotating planet like Jupiter, with an webcam or LiveView AVI you can easily capture a couple of thousand frames in the two minute window before rotation prevents any further stacking. Using individual RAWS you're going to end up with 12 or so frames to choose from (which is why I tend to use the latter approach on targets like the Moon instead).

Below is an example of my results with a DSLR LiveView movie: