DMK camera users question

[rat156]

Hi,

I'm still debating over whether I'll get one of these, so I need some info.

the 30 or even 60 fps sounds great, but can it do it? Is 1/60th of a second exposure long enough to grab anything?

The main reason I ask is that I was using my SBig last night on Saturn, with a 4x powermate in line as well. I have an 8" SCT and was using the shortest exposures that the SBig would allow 1/10th second. The pictures were dim on the SBig, which has one of the highest QE's of any CCD.

Cheers
Stuart

[Dennis]

Using a TeleVue x2.5 on my C9.25, it is possible to image Jupiter at 60fps although the image is a little dim (<200 on the histogram).

45fps and 30fps would be far more common for Jupiter with the above set up.

Saturn requires me to drop down to 10 to 15fps.

Cheers

Dennis

[bird (Anthony Wesley)]

I think you would use 60fps only on the moon unless you had a very large mirror, but 30fps is reasonable in anything from 10" and up.

The DMK doesn't let you select in-between rates, so you only have the standard rates of 60,30,15,7.5,3.75... etc.

cheers, Bird

[[1ponders] (Paul)]

There is something else to consider Stuart. You will be using rgb filters which will tend to lower the light levels as well. But on the up side you can take luminence runs without filters which will help bump up the brightness when you combine them. If using a luminence than you can go for slower colour frames to get the depth of colour and then use the faster rate frames for enhancing the detail with luminence.

[rat156]

Hi All,

Thanks for the input.

I reckon I'd still be pushing it to get anywhere near 60fps. But you've given me hope.

I'm gunna cheat on the colour. Use the DMK to get the Luminance data, then switch over to a webcam for the colour.

Now all I have to do is buy the DMK. Have the prices dropped due to the dollar being at 83c?

Cheers
Stuart

[rumples riot]

Stuart, you cannot compare the Sbig camera to the DMK, they are too different in their abilities. One is designed for DSO imaging and the other is designed for speed. Besides the well depths will hold differing charges, which gives differing responses in sensitivity.

Being able to acheive those rates of expose really depends on which image scale you are working to. I would say that with a 2x barlow and an extension of say nearly 100mm will allow a good size scale (like I achieved last year) and allow you to image at 1/34 of a second or 30fps. For 60fps you will need a much larger aperture or a much brighter target, like the moon or the sun (using the correct filters)

As you increase the scale (say near to 10,000mm) your ability to gain light becomes the overriding factor. With my images this year I am using near 1/23 of a second exposure at 10,000mm and the gain is nearly at max with my C9.25. On the other hand my 18" SDM gains so much light that I am at 30fps (I have a pre 60fps DMK that I bought April 2006) and with the gain down quite low and exposure at 1/34-1/60 on Jupiter.

Best of luck.