Here I am again ready to warm you a little head with some peers more, (this time with separations below 2) of the small but beautiful constellation Corona Borealis.
I must confess that this occasion and had to "currármelo" a little more.
And is that however good the night, that working to 6700mm focal length with a super-reduced field, has a crumb. Luckily over the years I learned to do a well aligned accurate (at the expense of many sweat and tears ...) which in addition to the familiar pointing accuracy of the LX200, 99% of the time I find the stars near the center of the chip.
still using the same equipment (except a x2 Barlow, a quite malilla) the technique used differs substantially from that used at prime focus for pairs with separations greater than 2. " On the other hand achieve results with the precision required is far more complicated than working with smaller focal lengths.
On this occasion, and in order not to dazzle the secondary with a saturated primary and try to "freeze" the effects of turbulence. The integration times were very short, ranging between 0.1 and 0.5 sec. This complicates the issue, because if QHY-5 behaves perfectly (as long as the images are properly calibrated) for exposures between 0.5 and 3 sec. When we reduce the integration time below 0.5 sec. The signal to noise ratio is very weak so it makes it difficult to isolate the stars in the images.
I think for future actions were to raise the number of images, 200 or 300 for example. Surely this way I'll get better S / N ratio and hence the final resolution of the images.
Another issue that has puzzled me is the calculating the rotation angle of the camera. If I use the usual method of calculating the rotation angle of the camera by the reduction of the images of the calibration stars, the plot thickens and gains in imprecision. So clearly I have such long focal using the Delta method of calculating matrix more suitable, is through a series or motor traffic stopped ....
On this occasion we have worked with the LX200R 10 "af/26 adapting a x2Celestron Barlow and QHY-5 mono, equipped with a filter Baader IR-UV Block. The temperature between the beginning and end of the session has varied from 23.6 º C to 23.1 º C. The relative humidity has remained around to 64% throughout the session.
The fishing method employed was to carry out series of 100 shots in each pair, to which they have been applied to their corresponding Darks (100 per pair). After filtering each series, with Best / Off (S / N), I have chosen the best images. Then have been aligned and stacked to later Autoreduc measure them in the case of STF 2004 because the final image resolution and permitted or using QuadPX and Surface features in the other cases. Of course the final number of images is much smaller steps that used to peer farther apart.
As I have used calibration pairs STF 1927 STF 2277 STF 2380, resulting in a rotation angle of the camera of 10.15 ° and a pixel scale of 0.31924 "
So that, here yo measurements and photos of a few copies of double guilty of my efforts.
-=-= STF 1932 Aa-B =-=-
Date: 2009.487
264.67 (sigma theta: 1.46) Med: 264.54
1621 (sigma rho: 0.03) Med: 1,621
Deltamed = 0.18
-=-= STF 1941 =-=-
Date: 2009.487
213.93 (sigma theta: 0.59) Med: 213.93
1529 (sigma rho: 0103) Med:
Deltamed = 0.05 1.5145
-=-= STF 2004 =-=-
Date: 2009.487
282.04 (sigma theta: 0.28) Med: 282.14
1712 (sigma rho: 0.019) Med: 1.71 = 0.65
Deltamed
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