Here I present results of some experiments comparing eyepiece projection and my X2 SLR extender lens using four different filters. Two of the filters (Hα and OIII) are narrow-band filters, the IR-block is a Baader IR-UV blocking filter, and the IR-pass is a commercial filter passing light of wavelength greater than 685 nm. This IR-pass filter is not the home-made one that I have used extensively in the past for lunar imaging. All the pictures were processed the same way in Registax, wavelets 1-3 = 10 and contrast increased to 150. I used a 28mm Plössl eyepiece (from Meade) separated from the camera by a distance that gave me approximately a X2 magnification compared to the image at prime focus. My SLR adaptor lens also gives a X2 magnification. At the top of the table of pictures below, is an image made at prime focus using the Hα filter for comparison. The enlarged images are reduced by 50% in order to make them more comparable to the image at prime focus. I seldom find that the X2 lens produces better pictures than at prime focus, but it is capable of excellent images given the right conditions (see for example my first image of Clavius). So I feel that the SLR lens produces pictures as good as the conditions permit and the comparison should be between the eyepiece projection and the X2 lens, rather than either with the image at prime focus. The telescope was my LX200, and the camera was my raw-modified Atik 1-HS (which is based on a Toucam fitted with a monochrome CCD). Images were captured using K3CCDTools, a gamma of 33% and the exposure and gain adjusted to give a reading of around 150 on the brightness meter. The pictures were taken on 25th March 2007 between 19:21 and 20:00 UT when the Moon was at first quarter. The two major craters are Boguslawski (the northern one) and Demonax which are deep in the southern highlands of the Moon. The libration was highly favourable at -6° 1' in latitude and 7° 8' in longitude which is about as good as it gets for the south-east. Finally, at the bottom, I show the assembly that fitted into the back of the LX200. The tubes come from Meade camera adaptors.
Prime Focus.
Hydrogen Alpha
Eyepiece Projection
X2 SLR Teleadaptor Lens
Hydrogen Alpha (Hα)
Oxygen III (OIII)
Infra-red light (>685 nm)
Visible Light (IR-block)
This is the set-up for eyepiece projection. Inset is a view of the front part showing the eyepiece. The parts other than the camera and the filter wheel, come from Meade camera adaptors. The front piece (also shown in the inset) is designed to hold the eyepiece and has a screw to hold it in place.
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