- Notes about the observations -
Some words about the observations described here
Evaluation of sky quality is unfortunately a really subjective matter. I have decided to choose the Bortle scale for all my observations because of simplicity. Most of my observations were done under Bortle 4 sky with NELM (naked eye limiting magnitude) of about 6.0m. But in the next time I will attempt to evaluate the NELM in addition to the Bortle scale. I will also provide SQM-L measurements, since a bought this device to determine the brightness of the sky.
Basically the conditions are evaluated for the zenith. If I have some more meaningful values for the observed region, I will include these information in the object description.
The observations are divided into three difficulty levels, depending on aperture, quality of sky and magnification (and maybe filter). Easy objects can be mostly seen with direct vision and should be doable for most beginners. Moderate objects need in most cases averted vision and can be a challenge for beginners. Difficult objects are only visible with averted vision, often at the limit of perception. These objects even can be a challenge for experienced observers. In addition I have listed also objects that I couldn't see until now.
In the case of resolvable open clusters or asterisms the difficulty level corresponds more to how evident the object appears. An inconspicuous object would be rated as rather difficult.
For carbon and red stars there is given the perceived color (red/orange) instead of the difficulty level.
Due to getting more experienced over time the given difficulty level can significantly differ on similar objects. I will try to make this clear in the descriptions of my observations.
Descriptions of objects
At the moment I explore the sky more systematically, so that the descriptions are partially poor. On the other side I have found some interesting objects like the more unknown but bright galaxy pair UGC3445/46 (Lyn). But in the future I will spend more time for observing to give more precise descriptions :-)
The object data were extracted from several freely available catalogues and other sources (SAC,PGC,UGC,NED,WDS,SIMBAD,AAVSO...). Unfortunately there are discrepancies over object names, magnitudes or angular sizes. That's why I've choosen only those data that seem usefull for visual observation.
The magnitudes are divided into visual magnitude (v) and magnitude of blue spectrum (b).
For double stars the magnitudes of the components, angular distance, position angle and last year of observation are given. For variable stars you can find also the period in days.
It is well known that a larger aperture shows more in many cases. That's why most beginners tend to choose a larger aperture that can be just handled. My experience shows that especially spontaneous observations fall by the wayside, because of much more hassle. So most amateur astronomers have some smaller telescopes for those situations. Who wants to see really much should not only be oriented to big aperture but keep in mind, how often the telescope will be used. Many observations show at least more than a few, because becoming more experienced over time. I realized that, when two other observers were not able to see a galaxy in a 12 inch Dobsonian, where I had no problem to see it in my 8 inch Dobsonian. Besides the experience there is also the quality of the sky very important. As the saying tells us: The best telescope is when it is often used.
There are many discussions about which eyepieces are practicable with an Dobsonian. In most cases wide angle eyepieces are recommended by observers to increase observation time without tracking. Nevertheless also simple designs like plossls or orthos can be a very good choice. Especially telescopes with low focal length are less critical concerning tracking the object. The statement, orthos are not practicable with a Dobsonian, is unreasonable in general. I use on my 8 inch Dobsonian some simple wide angle eyepieces (erfle design) and the good, old Baader Genuine orthos. Besides the sharpness there is also the contrast very important when observing faint objects. If a faint object is located nearby a brighter star, a small field of view can be advantageous to reduce scattered light and to focus more easily on the object. On the other side well made orthos costs a fraction of the cost of Nagler or Ethos ;-)
Exit pupil / Magnification
In short: When observing faint, more compact objects, higher magnifications are needed. With my 8 inch Dobsonian I often go down to 1mm exit pupil, when I observe for example fairly faint galaxies. At 8 inch aperture this corresponds to a magnification of 200x. Also for extracting details it can be very advantageous to increase magnification. I recommend to play around with magnification. However I must point to the fact that small exit pupils requiring getting used to because of a really dark image.