Uranus with details, 13 and 16 august
Posted 18 August 2013 - 01:48 PM
Two nights of good seeing allowed me to capture as well some details on Uranus. For this I use the Baader RG610 filter, which works better than the IR685 for my 250 mm telescope (more light, better resolution).
The best result, with 2012 comparison, shows the brightening on the north pole (in reality, this is a belt, but unresolved), and the equatorial belt:
The IR685 Baader shows only a faint EB:
And a RG610 image from the 13th, less good however:
All the images are taken from extremely long SER files (30-40 mn), a perfectly collimated 250 gregorian working at F/32. Some 10K raw frames are stacked each time, exposures range from 150 ms to 200 ms.
For each session I take a drift image that helps to find the correct orientation of the images, but if you can spot some moons at the same time, it works well.
Posted 18 August 2013 - 06:18 PM
Posted 18 August 2013 - 06:52 PM
Thanks Rolando, the drift is obtained from a single movie (where I drift the planet in RA) and made as a dark frame under Registax.
Posted 18 August 2013 - 07:28 PM
Have you been using a dispersion corrector with the 610? Although I think that it's not truly necessary with the 685 it may be worthwhile with the wider effective bandpass of the 610/camera combination.
Posted 19 August 2013 - 11:28 AM
Posted 19 August 2013 - 02:30 PM
John, I did not use the ADC. I assume this is not necessary with the RG610 - at least at an elevation of nearly 50°.
This could be discussed, but as my ADC (ASH model) blocks a small part of near IR I'm not ready to lose photons on such a hard target... !
Posted 19 August 2013 - 09:42 PM
Posted 20 August 2013 - 05:27 PM
I start the movie when the planet is on one side of the CCD, then drift it in RA (I don't care what sense is it since I know where is celestial south). When arriving at the other side of the screen, I stop the drift and let the planet alone for a few seconds (by this way I get two balls at each ends of the light path).
I process it as a dark frame in Registax ("made dark"), strongly enhance the luminosity, and reduce it to 33 %.