Amateur Astronomers Association of Princeton

by John Church

At the December AAAP meeting, Gene Ramsey, Dave and Jen Skitt, and the writer reported their progress on a plan to upgrade the refractor mount to make it more usable for both club members and the general public.

To review, there are two issues that need attention. First, the donated Losmandy GoTo mount that was installed in 2014 has not worked out well; it has a steep learning curve and other disadvantages. Fortunately we have a donated computer-capable Paramount which we believe can be readily mounted on the original cast-iron pier. The Paramount should also be able to take the current plate that holds the refractor onto the Losmandy.

Second, when pointed at objects higher than about 60 degrees above the horizon, the eyepiece has always become inconveniently low. Replacing the Losmandy with the Paramount will raise the entire OTA about 8 inches more above the floor, and it should still clear the roof when it is being rolled off.

This height gain alone should be helpful, but in addition we also propose moving the tube about a foot more up in its rings, which would give a total gain in eyepiece height of about 20 inches for the higher altitude objects. This will of course require that the assembly be rebalanced around the declination axis, but the existing sliding weight at the upper end of the tube should be able to compensate for this. Balance around the polar axis should not be affected.

Philosophically speaking, different sets of observers have legitimate and totally understandable preferences for the kinds of objects that they like to observe and possibly photograph. To accommodate these different interests, we feel that having two distinct types of fine telescopes in the observatory, each with its own special advantages, is very beneficial. The C14 is good for deep-sky objects and the refractor is good for solar system objects and open clusters, where its sharp definition and wide coma-free field of view can make for a rewarding observing experience. Additionally, the latter types of objects are often more appealing to the general public than deep-sky objects, as well as being much more easily accessible under the observing conditions that typically prevail in our area.

Another advantage of the refractor is that its objective and tube are always close to ambient temperature. It therefore needs very little equilibration time after the roof is opened. The large primary mirror of the C14 can take much longer to equilibrate and give images steady enough to appreciate, especially during the warmer months when the building heats up significantly during the day. Irregular air convection currents due to slow internal cooling within the wide tube can also be an issue.

Club members already know about the history of the refractor, and this background is typically of great interest to visitors. They also appreciate the opportunity to use a classic 135-year-old instrument that can provide excellent views of the moon, planets, open clusters, multiple stars, and some of the brighter deep-sky objects. Of the three objectives that Hastings ground himself, this is the only one still in active use as far as is known.

If we are successful in the remounting project, the next step would be to make the instrument fully computerized and have it operated by The Sky software in the same way that the C14 is operated. It would need its own computer, as of course any instrument would.

Here are photos of the lunar craters Copernicus and Tycho that I took on High Contrast Copy film and processed in my darkroom. The jagged shadow of the central peak in Tycho can be compared with the same area in a closeup taken by Lunar Orbiter V. Using a 2x Barlow gave an EFL of 4600 mm and therefore a large image scale, bringing out details down to nearly 1 arcsecond.

Even better resolution can be obtained visually. Watching the shadow play as the terminator creeps across the floor of a crater in the period of half an hour or so can be entertaining and educational to members of the public, and sometimes even to us hardened observers!