Saturn May 4 15 fps vs 7.5 fps

[Doodles23]

These shots show I have no business fooling around at 7.5 fps. Taking 1000 frames at that speed may give nice bright images relatively free of noise but all tiny planetary details are going to smear. Nothing shows it better when you see the storm in the 15 fps image which was taken just after the previous 7.5 fps image. Both have good banding detail but the storm is round in the 15 fps image as opposed to oval. I know our friend Bird wouldn't be caught dead imaging at 7.5 fps. Now I can see why.

Well it's time to head out again for another good night.

DB

[bird]

Dave, I was just doing some calculations to see how much light you had available (your 255mm mirror vs my 368mm mirror) to see if that's why you were down at 7.5fps. I know the DR2 can do better.

ps are you using Windows? If so then you should try Torstens FireCapture, it unlocks the extra gain on the DR2 and lets you go up to 36db :-) Much better than the default 24db ceiling. The noise will probably limit you to about 30db or so, but still a good improvement.

If you're using Linux then Coriander can do the same unlock on the extra gain.

Ok, so the calculation shows that you have about half the light gathering on your scope compared to mine, and I'm doing 30fps on Saturn so I guess 15fps is a good rate for you.

cheers, Bird

[Doodles23]

Sorry. Our instruments are essentially the same. Remember I'm the lone Mac guy in the crowd. I use Astro IIDC, a Mac program to capture. And you hit the nail on the head about the gain. Milton, the developer of Astro IIDC would NEVER allow the software to push gain beyond the 24 db ceiling. If pressed, he says "You're just amplifying noise!! Why would you want to do that?". The conversation ends shortly after that outburst. I can run the MacBook in Windows mode and it may be prudent to get Torstens FireCapture.

Incidentally Milton and Point Grey informed me that Astro IIDC will recognize the Flea3. So later this year I will be moving up to that camera from my grey market DR2.

I have attached the dim raw blue tiff captured at 15 fps from the camera. This is shown actual size in the 640 X 480 capture window. The tiff has been converted to a jpg for posting. Naturally I am scared when I hear you mention that Flea3 has somewhat LESS blue sensitivity than the DR2.

[bird]

ok, 355mm... hmm...

you don't need Miltons approval to do this, provided his software lets you put the gain register into "absolute value" mode then you can manually enter gain values up to 36 db :-)

The gain is applied directly to the a/d stage, so there is a point where it will reach maximum useful value, but this depends entirely on the camera and ccd, and it's s/n. It's not correct to state flatly that 24db is the limit.

cheers, Bird

[bird]

ps, here's a blue frame from the Flea3, at its max gain of 33.2db. The camera was running at 30fps and this is actual size , not scaled up or down.

You can see that the background is still quite reasonable....

cheers, Bird

[bird]

pps the noise is pretty much irrelevant :-) It's randomly distributed and goes away once you stack all the frames, what you're left with is simply a sharper result due to shorter exposures :-)

cheers, Bird

[riklaunim]

Dark scary colors :) Very nice. As for blue I'm planning to test UV channel with wratten 47 and IR-blocking filter. Should contrast the rings much stronger than the planet.

[bird]

Dave, also worth searching around to see if you can find a port of Coriander to MacOs - it's based on libdc1394 which has been ported already and the gnome gui toolkit which has also been ported. You might be lucky and find a precompiled version that you can try.

cheers, Bird

[Doodles23]

I really appreciated your posting of your raw blue frame. It enabled me to make a direct comparison with your camera. Granted the seeing may have been better at your end but I believe your final blue tiff image generated from the blue frame after stacking and optimizing may not differ a lot from mine. Note the larger amount of noise in your frame vs my frame. Your frame is somewhat sharper. A blue frame from the same night at 7.5 fps is shown for comparison. I should mention that I am capturing at 12 bits.

Overall you don't cringe from noise because you feel that stacking will reduce it sufficiently to make it irrelevant in the end. My Astro IIDC camera can be set for stretching that will make the captured image look very similar to yours in overall noise but I have an aversion to that much grainy noise and go for the dimmer, non stretched capture every time. In the end we seem to arrive at the same place in S/N land.