Rare alignment of the planets

On 10th December, Mercury passes from east to west of the Sun. Then, and until the 13th December, all the planets will be ranged out across the sky in their true order from the Sun. Venus, Mars (difficult), Jupiter and Saturn are all visible to the naked eye on that day/night, Uranus and Neptune are evening objects both requiring telescopes or binoculars to be seen, and Pluto is observable only with large telescopes.

Finally, on the 13th December, Pluto is in conjunction passing to the west of the Sun and the sequence will be broken.

Imaging astronomical subjects using digital cameras - the moon

Fig1: Minolta Dimage F300 5 mega pixel digital camera (now discontinued). All photographs John Vetterlein. Click the image for enlargement.

Typical 1.25" Super Plossl eyepieces flanking an Optolyth x45 eyepiece (when used with the 100 mm telescope). The rubber shield has been removed from the 12.4 mm Plossl. Note the deeper recess for the eye lens in the 40 mm Plossl. This makes for tricky alignment when attempting to get a full disc shot. Click the image for enlargement

Fig3: Moon. Full disc imaged with 45x100 telescope. 1/250 sec. ISO 200. 2004 November 02, 06h 10m UT. Click the image for enlargement

Fig4: Moon. Full disc imaged with 68x150 telescope. 1/250 sec. ISO 200. 2004 November 02, 06h 12m UT. The location of crater Theophilus is shown. Click the image for enlargement

Fig5: The crater Theophilus imaged by 175 mm Maksutov working at x135.1/90 sec ISO 200. 2004 November 01 22h 30m. UT. Click the image for enlargement

The crater Theophilus imaged by 175 mm Maksutov working at x135.1/90 sec ISO 200. 2004 November 02 05h 40m UT. Click the image for enlargement

Since the short piece on digital cameras last year I have received a number of queries mostly to do with the Moon.

Observers find that in general they are unable to feature the Moon in its entirety when photographing through the eyepiece of a typical spotter telescope.

As I pointed out in the original article, the camera's lens has to be sufficiently small to fit over the eye lens of the eyepiece. But this is not enough. Ideally the camera lens and the eyepiece should be in virtual contact. If the camera lens is set too far back in its housing this becomes impossible.

I struck lucky with my first digital camera (a Minolta Dimage F300) since the construction of the lens housing is ideal (Fig. 1).

With this camera it is possible to obtain full disc images as well as higher magnifications simply by using the x3 optical zoom on the camera. (For choice of camera settings see archives.)

I have tried other cameras (Sony DSC V1 for example) most of which have the correct barrel diameter (approximately 27mm) but whose lens is set too far back to enable one to get satisfactory results.

The telescope eyepiece also plays a part. In Fig. 2 the middle eyepiece of the trio is from an Optolyth 100mm spotter telescope. With this telescope working at x45, I can get the Moon's entire disc in the camera quite comfortably simply by holding the camera against the eyepiece. (The two lenses are very close but not in contact.)

Indeed, I use this setup for full disc images of the Sun (using Baader filters) in preference to larger telescopes since everything can be done so quickly. Very often by the time I am ready to use more sophisticated equipment the weather closes in and rules everything out!

The full disc image using the 100 mm refractor (Fig. 3) is quite clearly less detailed than that obtained with a 150 mm instrument (Fig. 4).

Images of the Moon using the Minolta in conjunction with telescopes of between 100 mm and 200 mm have yielded results comparable to those achieved via custom built CCD equipment. I give an example for the crater Theophilus.

A close-up of the crater Theophilus is shown from a 175 mm telescope using an eyepiece giving a power of x135. Changes in the shadow features thrown by the multi-peaked mountain within the crater may be seen from the two images taken some six hours apart. (Fig 5 & Fig 6)

Physical data for Theophilus;

• Dimension: 104x104Km / 61x61Mi
• Height: 4400m / 13300ft
• Height/Wide ratio: 0,044
• Circular formation making a trio with Cyrillus and Catharina.
• Flat floor. Central mountain 1,400 m high
  with 4 summits. Line of crests, hills and craterlets.

Where stability is concerned, holding a camera to the telescope eyepiece is bound to be something of a hit and miss affair when exposures are as long as 1/100. One should therefore take a series of ten or more shots and pick out the best results.

Since this information is directed at those using quite basic equipment considerations of telescope driving do not come into consideration here.

Likewise I have not featured the Sun in these articles for the safety reasons I have often given in the past. However, I am quite happy to advise individuals should they wish to undertake solar photography or other work. I can be contacted through The Orcadian.

JV 06/11/04