Whilst waiting for Near Earth Asteroid 2008 BT18 to clear some trees, I had some fun capturing M16 (followed by Uranus and Neptune - separate posts).
There was a big, bright, bold almost full Moon some 35 degrees away, but I was astonished at how ccd cameras can “shrug off” the light pollution and gradient, although the ST7E does only have a 765x510 pixel chip. Sorry, no RGB colour this time!
Brisbane, QLD, Australia
19th July, 2008 starting at approx. 8:40pm AEST (GMT+10).
Takahashi Mewlon 180 F12 at prime focus.
SBIG ST7E CCD camera, 10 sub frames of 240 secs each.
Now they are big Pillars!
Done well in the moonlight!
Did you use any filters?
cheers Gary
Thanks Gary! No filters used, as the Mewlon is a relatively slow system at F12, so I daren’t contemplate adding filters! Although being so slow, I think is makes it more immune to light pollution, especially with a smaller CCD?
I’m in awe of the imagers who have conquered mega-pixel chips and DSLRs; fixing up the gradients must be awful!
Nice shot Dennis - I know what you mean about the CCD performance cutting through the sky glow.
Peter
Thanks Peter – is certainly was bright last night so I wasn’t expecting too much from the M16 image. It is quite dark as at F12, I just didn’t capture enough data.
A pleasing "fill in" image Dennis. At F/12 I wouldn't expect the ST7 to bloom very quickly. Perhaps could have gone longer subs, though there are a few bright stars in the FOV. Hope to see more of your DSO imaging adventures at 2160mm FL.
A pleasing "fill in" image Dennis. At F/12 I wouldn't expect the ST7 to bloom very quickly. Perhaps could have gone longer subs, though there are a few bright stars in the FOV. Hope to see more of your DSO imaging adventures at 2160mm FL.
Thanks Jase. I tried a 5 min sub frame and one of the stars bloomed, so I reduced the subs to 4 mins to help prevent the blooming. LRGB imaging at this fl requires a lot of skill and dedication to all aspects of the process, from equipment set up and tuning through acquisition followed by hours of reducing, calibration, aligning, combining and processing. I’m not too sure I’m up for this just yet.
I’m still at the point and shoot phase of my development, and have a long, long way to go before I move into the arena of capturing optimised data over several nights for a single target using large chips. A daunting path to follow!
However, these occasional excursions at over 2000mm do help me appreciate the technical skills and mastery behind some of the deeper images I see on IIS, especially yours!
Quote:
Originally Posted by AlexN
Oh yeah! captured those pillars marvelously Dennis.
Well done. Esp. under full moon conditions.
Thanks Alex – I was pleasantly surprised with the outcome given the conditions.
Quote:
Originally Posted by Ric
A lovely up close capture of the pillars Dennis.
A top shot.
Thanks Ric - it was nice to point the scope at a DSO once more. Without a 25” dob, this is the only way I’ll get to see some of the beauty of these amazing celestial sights.
Quote:
Originally Posted by iceman
That's some serious FL, Dennis. very challenging indeed but a very nice result.
Thanks Mike. The set up and system all worked well, which was a really pleasant surprise after such a relatively long lay off. However, I’m not too sure if I’ll make a career of long fl DSO imaging just yet though, it certainly is one tough journey.
Technically, if you're dithering a few pixels between subs, you can let the camera bloom a bit more than usual. After you've removed the blooms and aligned the subs, you'll find that the dithering will result in minimal loss of details due to the bloom. Of course if you have a blooms that bleed a large amount of pixels, it does create a little more work for you, but still manageable.
Actually, you can salvage most subs with bad blooms if you've got one sub that you use as a reference frame that does not contain heavy blooms. You can then subtract the the details using the reference frame. This is somewhat a tedious task, but works if you don't have the luxury of mega data.
If there is one thing that catches me off guard regularly with NABG camera's is to know the optimal exposure time to get over the noise hurdle, but not introduce heavy blooms. There is no set value you can work with as it depends on what is in the FOV.
Don't leave it too long for another post. Perhaps try some straight RGB's and ditch the luminance for a while.
A lovely close up of the pillars and considering the conditions it has turned out great. I tried to capture the Eagle nebula with my DSLR camera a couple of days ago and the whole frame was washed out because of the Moon.
A lovely close up of the pillars and considering the conditions it has turned out great. I tried to capture the Eagle nebula with my DSLR camera a couple of days ago and the whole frame was washed out because of the Moon.
Very well done.
Thanks Matt. The SBIG ST7E CCD camera is a 2nd hand unit I purchased from an IIS member several years ago and although it’s quite old in terms of years, it does have a reasonably high quantum efficiency (QE) which is great for my slow F12 ‘scope.
QE is a measure of how efficient the chip is at converting incident photons into electrons and from memory, my ST7E has a QE of around 65% at a wavelength of 650nm.
When I first used my Canon 40D DSLR on the Mewlon at F12, I was dismayed at how dim the images were, as the DSLR chip has a lower QE and the Bayer matrix further reduces the efficiency for astro photography. The ST7E is also cooled which help keep noise to a minimum, although I think the Kodak chips used in my model are quite noisy compared to CCD cameras that use the Sony chips.
This is not to knock DSLR’s, more just an observation from using my particular set up, as there are some very talented DSLR imagers out there producing superb results.
captured those pillars marvelously Dennis.
