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| p.2 #10 · Nightscapes using AstroTrac Tracking Mount |
Fred Miranda wrote:
You've captured incredible images. Thanks for sharing them. I can see you got to the point of no return!
Trying my 500 II on it was not my initial intention and I was shocked to get something to work with on a full moon sky. I almost attached my 1.4x extender on it.
When focusing using Live View at 10x, I could see the stars moving rather fast. The Astrotrac wedge gave me the confidence for its precise and stable alignment.
Thanks for the suggestion on using an autoguider for long focal lengths.
Have you tried the LVI SmartGuider 2?
I have the new AG version and realized that a precise alignment is crucial for declination with long FLs because as far as I know, with the Astrotrac, an autoguider only works in right ascension axis.
From the info I've read, it's almost better to take many stacked photos using the same exposure. Staking is well-known for increasing S/N ratio but can we get extended dynamic range?
Thanks for taking a look Fred... and you're right about being at the point of no return.
I personally have not used the LVI smartguider. I use a separate CMOS sensor through a device called an off-axis guider. You can see the set-up here:
The guide camera is the small square box, on top of the scope, near the rear. For my astro set-up, it simply connects to the software on my laptop (MaximDL), and it handles all the guiding. For portability, I'd think you would want a self contained guider, like the LVI, or similar. But you'll generally get better results with a laptop and separate guide camera. You can use a free copy of PHD :
Regarding stacking, it's definitely better to stack, than a single frame (at least in most amateur applications). Stacking helps fill-in the noise, found in a single sub-frame (increases the S/N). 10 is better than 1; 100 is better than 10... I stack all my images. I also calibrate, with flats, bias and dark frame subtraction. You'll find that a stacked & calibrated image will be much easier to process. Also, you want to shoot in RAW, to stack the highest bit-depth that the camera allows. You'll be able to stretch and push the processing much better in 12, 14 or 16 bit.
Here's a quick write-up on calibration:
Also, Deep Sky Stacker is a free image stacking package, if you wanted to give it a try. You can stack in Photoshop, but if you're stacking a large number of frames, a dedicated program will be much easier.
Feel free to PM me anytime I can be of assistance for Astrophoto stuff...