Gallery XXV

          The StellaCam face off , II vs. EX

            The conditions on 1/6/04 were cold 18-20 degrees f, and it was a full moon, but the sky was clear and I had a new camera.

          I've been wanting to try to compare the Stellacam EX to the Stellacam II. With the full moon out the conditions were less than ideal. I pointed the C14 in the Donald C. Martin Observatory at Messier Object 82, the irregular galaxy in Ursa Major. A favorite object of mine, it was barely visible in the 24mm Panoptic EP. But both Stellacam's showed it nicely.

          I wanted parity between the cameras. To make things "equal" I set the Stellacm EX at a "sense up" of 128x and the Stellacam II at 64 frames - both are roughly 2 second exposures. I imaged with The Stellacam EX at 50% and 100% manual gain with and without a LPR filter (Lumicon "Deep Sky") for 60 images or 120 seonds.. With The Stellacam II I imaged at 50% gain with hi and lo contrast also at 60 images for 120 seconds. At this point I began to wonder what "parity was". Numbed by the cold I shot 50% gain lo contrast for 120 frames or 240 seonds. I ended with 95% gain (one "tic" below maximum) with no contrast. An Optec f 3 reducer was used for all these images.

Up first the venerable Stellacam EX

Stellacam EX

 with and without LPR at 50 and 100% gain, sense up 128x, 60 x 2 second images (120 seconds total)

Each image is an unprocessed (other then for being cropped) composite of  60 x 2 second images captured and added (integrated) on the fly  with AstroVideo.

50% gain	50% gain and Deep Sky LPR filter
Max gain	Max gain, deep sky filter

Up next the new comer, the Stellacam II

Stellacam II

 60 x 2 second images (120 seconds total), frames set at 64

50% gain, lo gamma, 120 seconds	50% gain, hi gamma, 120 seconds
95% gain, no gamma, 120 seconds	50% gain, lo gamma, 240 seconds (I doubled the time for this one but at lo gamma the results on the raw image were disappointing)

            At the end of round one of the Stellacam face off several things were apparent. There is higher back ground brightness on the Stellacam EX images. This was improved by the LPR filter. The gamma control on the Stellacm II has a big effect on the images. More detail was seen at hi gamma with 50% gain. Even comparing the 120 second "hi gamma" image to the 240 second "lo gamma" image, more detail is seen in the shorted "hi gamma" image. When I cranked the gain all the way up the image was "washed out at hi or lo gamma. I think that the "no" gamma image at 95% gain shows as much or more detail as the "hi" gamma 50% gain image, but with a higher back ground brightness.

Now for images "head to head", EX vs. II

Mid gain images - 120 second images

Stellacam EX, 50% gain, sense up 128x

Stellacam II, 50% gain, lo gamma 64 frames

Stellacam II, 50% gain, hi gamma 64 frames

High gain Images - 120 second images

Stellacam EX, 100% gain, sense up 128x

Stellacam II, 95% gain, no gamma, 64 frames

Now lets look at the same images but with some image processing.

Nothing fancy, all I did was play with the top and bottom sliders in the "levels" tool in GIMP. This is not sophisticated and is not the way to "eek" the most out of an image.

Stellacam EX

 with and without LPR at 50 and 100% gain, sense up 128x, 120 second images

50% gain	50% gain and "deep sky" (LPR) filter
100% gain	100% gain and "deep sky" (LPR) filter

Stellacam II

 60 x 2 second images (120 seconds total), frames set at 64

50% gain, lo gamma	50% gain, hi gamma
95% gain, no gamma	50% gain, lo gamma, 240 seconds  (the others in this box are 120 seconds)

       Now the head to head images repeated, EX vs. II

Mid gain images - 120 second images

Stellacam EX, 50% gain, 128x sense up

Stellacam II, 50% gain, lo gamma, 64 frames

Stellacam II, 50% gain, hi gamma, 64 frames

High gain Images - 120 second images

EX at 120 seconds vs. II at 240 seconds

Stellacam EX, 50% gain, 128x sense up, 120 seconds

Stellacam II, 50% gain, lo gamma, 240 seconds.

            As I look at these I wonder if these are apples to oranges. I wonder what the best settings are for each camera. In the past I've just "cranked up" the settings on the Stellacm EX and images for longer periods of time. Perhaps now it is time for subtlety and mixing of gain (and on the II gamma) settings to optimize the image.

          I wonder what role M82's "infra red excess" (it emits more IR light then visible light) plays in the Stellacam's ability to detect it. Hmmm.

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