Remeis observation guide

This page should contain information and tips & tricks about what to do to obtain beautiful images from planets, nebula, galaxies, etc pp.

We are equipped with two important cameras: the astronomical CCD camera SBIG STL-11000M and the consumer DSLR camera Canon EOS 1000D.

Moravian C4-16000

The new camera for imaging in the EHT is the Moravian C4-16000. The camera has a CMOS detector with size of 4096x4096 pixels. Each pixel has a size of 9x9 micrometer that means a sensor of 37 × 37 mm. The camera has an effective pixel depth of 16bit which is obtained by combined the high and low gain mode. The gain values of the two mode are fixed, and two set of calibration frames has to be used in order to calibrate the images.

The C4-16000 can be used with or without reducer. The reducer is an optical system which reduce the focal length of the telescope by a factor of 0.66. Using the reducer improves the sampling rate of the camera, and it increases the FoV from approximately 0.60 deg to 0.91 deg.

SBIG STL-11000M

As all astronomical CCD cameras, the ST11K does only obtain black/white images, i.e. to obtain color images one needs to make images with different filter wheels and combine them later using software like ISIS or AstroArt.

See the observation log for an overview of what has been achieved so far.

The ST11K has a 11 Mpixel 36 x 24.7 mm CCD sensor.

Field of View

The Field of View (FoV) when attached to the 40cm MEADE telescope (f/10) is 0.52° x 0.35° i.e., 31.0′ x 21.1′. Or, if the camera is oriented in a way that North is up, i.e. the camera is attached to the telescope so that its one side is parallel to the mounting, we can express the FoV in minutes of RA and DEC (where RA is given in hours rather than degrees): RA 0h 2.1′ x DEC 0° 21.1′. This information is helpful when comparing the FoV to the image in Stellarium displayed in equatorial mount mode.

When attached to the 51cm telescope (f/6.8) the FoV is 35.9′ x 23.94′.

For comparison, the former 60cm telescope (f/18) has 11.5′ x 7.8′ (RA 0h 0.76′ x DEC 0° 7.8′).

Regenerating the Desiccant

The ST11K has a small container of desiccant inside to reduce the (air) humidity. This avoids the growing of ice on the CCD. The desiccant is, however, saturated after some time and has to be regenerated:
1. Open the camera by removing the screws on the front. Be careful not to touch any filter on the filter wheel, which is mounted at the back of the front plate.
2. Remove the desiccant container mounted at the right of the CCD chamber (see picture).
4. Close the resulting hole in the chamber with tape to avoid dust to flow in.
5. "Bake" it in an oven (e.g. in the kitchen of the meridianbuilding) for 4 hours at 175°C.
6. Attach the container (after it cooled down, of course) back to the CCD chamber and close the camera.

Canon EOS 1000D

Being a very recent addition to the Remeis imaging crew (Fall 2010) not so many pictures were yet taken with the Canon. It's big advantage over the ST11K is that color images are obtained directly, making the post-processing much easier and more beginner friendly. Its huge disadvantage is the higher noise-level and that all images are already strongly processed by the internal computers, so that astrometry or photometry is impossible. In January 2011 it was modified by Canon to be more sensitive in the Infrared, a so-called Astro-Mod.

The Canon has a 10.1 Mpixel 22.2 x 14.8 mm CMOS sensor.

Field of View

When attached to the 40cm MEADE telescope (f/10) the FoV is 0.32° x 0.21° i.e., 19.1′ x 12.7′.
Attached to the 60cm telescope (f/18) the FoV is 7.07′ x 4.71′.