DeepskyLog

DeepskyLog, a unique database for visual observers

Astrophotographers record their observations on pictures. Visual observers by definition don’t do this. Nevertheless, most of the visual observers also have the need to record their observations. In the past, before the digital era, this happened in a small notebook. It described as precisely as possible what exactly had been observed and often, a sketch or a precise drawing was also placed with the tekst. Nowadays, this can all be done digitally. Observers can not only view their observations again later, but the observations can also be compared with the notes of other observers. The ultimate tool to do this is DeepskyLog[1].

By: Jan van Gastel, Tom Corstjens and Wim De Meester

• DeepskyLog has become much more than an online logbook for observations.

• Besides logging and comparing observations, DeepskyLog also offers the possibility to create observing lists and atlases.

• DeepskyLog is still being expanded, improved and adjusted.

Figure 1. Log of a sketch of galaxy M99 in DeepskyLog by one of the authors (Tom Corstjens).

Figure 2. The observations in DeepskyLog are done in a lot of different countries.

DeepskyLog, as the name says, was originally intended to add deepsky observations of objects that are outside our solar system, such as open star clusters, globular clusters, galaxies and different types of nebulae. DeepskyLog was originally developed more than 10 years ago by volunteers from the Deepsky section of the Astronomical Society (VVS) in Belgium, including two of the authors of this article (Wim De Meester and Tom Corstjens). The database now contains tens of thousands of observations and thousands of sketches  and drawings made by amateur astronomers from all over the world. It is – by far – the largest database with observations in this area. Some data in the following table.

Data concerning the use of DeepskyLog

Number of active observers	306
Number of observers with at least one sketch	112
Total number of observations	138127 *
Total number of drawings	16132 **

  *  135691 deepsky, 2436 comets

 ** 15864 deepsky, 284 comets

 

Figure 3. The number of entered observations per year.

 DeepskyLog is now also being used far beyond Belgium (Figure 2). The number of observations imported each year is also growing (Figure 3), especially since 2003[2]. The value of DeepskyLog for visual observers is increasingly being discovered.

It is very easy to use the menu to find observations of all types of deepsky objects individually or together, logged by a particular observer or observations of a particular galaxy, made with a certain type and size of telescope, observations from objects with a certain brightness and much more.

 

More than an extensive logbook

DeepskyLog is much more than a tool for logging or searching for observations. It is also an excellent tool to plan observations with the correct search maps and to estimate the visibility of the objects with a particular instrument. More programs can do that, but an internet application such as DeepskyLog makes it possible to compare your observation with those of other observers with the same or a different telescope and under the same of totally different conditions.

Let’s further investigate the possibilities DeepskyLog offers[3]. We take the moonless night from February 28 to March 1, 2019 as an example, based on excellent weather forecasts and focus on galaxies in Coma Berenices. As an observation location we choose our back garden, in a village not too close to a large city, with a border magnitude of about 6 after dark adjustment of our eyes and an SQM value[4] between 20 and 20.5. Not bad for a small village in Europe. The moon only rises after 4 o'clock that night, so there is plenty of time to enjoy a dark sky for a long time.

We log in to DeepskyLog and select the ‘Search Objects’ button on the home screen.

Figure 4. The header of the home screen of Deepskylog with various options.

Then, we can fill in all sorts of things, such as the type of object, the minimum and maximum brightness of the object, the constellation in which the object is located, whether we want to see objects that we have seen before or not and much more. We can also choose which telescope we use. We choose a 30 cm Newtonian telescope and ‘Only objects that haven’t been seen by me’. We select Galaxy and the constellation Coma Berenices. Because we only want objects on the list that we can actually see, we choose objects with a minimum brightness of magnitude 12. We can also enter a surface brightness, but we don’t do that this time. We do, however, enter a minimum contrast reserve of 0.1[5], then click on Search and then get a list of galaxies that meet our specifications. Each page will show 10 objects (Figure 5)[6].

Figure 5. The page with the objects of the search query.

 

This page provides us with a wealth of information. We find, for example, under Best time what time the object reaches its highest position in the sky that night and under Best at which magnification we have the highest chance of seeing the galaxy. This magnification does not necessarily shows the most details, probably we need to use a larger magnification for that. An other important variable is the contrast reserve. In our list it varies between 0.1 and 0.4. These are not the easiest objects for our telescope, but with some effort and under good conditions, theye can bes een with our 30 cm telescope.

Another interesting column is the column Seen. If we hover over this column for a specific object, a pop-up screen will appear, saying Object already observed by others, but not by me. By clicking on it we get a list of all observers who have viewed this object and entered their observations in DSL, with information about the telescope they use and a description of their observation. If, for example, it appears that someone has not seen the object before with a 30 cm telescope, we can still delete it from our list. Or we see this as a challenge and anyway try to observe the object.

Finder charts

Without a go-to system on our telescope, finder cards are needed to find the objects. These are also available in DeepskyLog. Go to Maps at the bottom of the page with the selected objects in the previous step. We then get a page with the previously selected objects, on which we can enter how many cards we want and from which object(s). In the row with the blue marked letter V, we enter which field of view (FOV) the cards must have. A maximum of three FOVs can be entered and we opt for 120, 60 and 15 arc minutes, the first of which mainly serves as an overview card and the third provides the most detailed information to actually get the object in view. Next, we specify to which magnitude deepsky objects must be shown per chart, and also to which magnitude stars must be displayed. We enter 10, 11 and 12 for objects and 10, 12 and 15 for stars. Weaker stars makes no sense, because even under very good conditions we will not see any stars weaker than magnitude 15 with a 30 cm telescope. We can also choose to get photos on the map from the Digital Sky Survey. To do this, we fill in the Photos column to see how large the image field of those photos should be. Once completed, we check behind each object in each column under the blue marked Vs whether we want a chart from it (no check mark is not a chart of the relevant object). As an example, we only select the first object: galaxy NGC 4889. Then we click on each blue V and behind every object that we have selected the data that we have entered in the row with the blue Vs appears. We then click on the name of the object for which we want a chart.

We then receive a .pdf file with a chart per image field. We can print the charts or take them outside on a laptop. We also bring drawing equipment to make a sketch of each object. If the object can only be seen with great difficulty during the observation session, we note in the sketch: "NGC 4889 is difficult to see with direct vision, but better with averted vision." We see an oval galaxy, with a fairly even light distribution and perhaps a hint of a brighter center. ”

 

Logging observations

After the observation session we enter our notes and drawings in DeepskyLog. In the home screen we click on Add observation, after which we enter the name of the object, in this case NGC 4889, and click on Search object. In the screen that opens, the telescope that we have set as standard telescope has already been entered, as well as the observation location and other data, such as the naked eye limiting magnitude and / or the SQM value. If necessary, we can adjust that data to the situation as it was during the observation. Then we fill in the date and time, eyepiece used and the visibility of the object: very good to see, or just visible. We also enter the description of the object and add the drawing. When everything is filled in, we click on Add observation and the observation will be added to the database.

Now we can immediately compare our observation with these of others. A screen appears in which not only our own observation can be seen, but also how many other observers have entered their observations of the object in DeepskyLog. In this case, including ourselves, 63 observations, including 9 drawings. That's good, because a good drawing often contains a lot of information. If we now click on this number 63, we will get a list of all these observations. Using the last column we can compare our observation of this object with these of others. If we select the letters AO (all observations) behind our own observation in that column, then we get to see all other descriptions of the observation of NGC 4889 in addition to our own observation.

 

Making atlases

DeepskyLog can also make complete atlases. To do this, click on Download atlases on the home screen. You can then choose between general and personalized atlases. For a general atlas, the preliminary work has already been done by DeepskyLog. With personalized atlases you indicate the sky area you want to have an atlas from. Personalized atlases also show which objects you have already viewed (and have drawn), by placing a line above them: very handy. They also contain the very latest updates to the objects. For both types of atlases you can choose the level of detail of the maps by choosing between Overview, Search and Detail. The Detail maps cover an area no larger than six degrees, with stars up to magnitude 15. It will be clear that the program needs some time to compile such an atlas, but then you also have a decent, free atlas.

 

Creating observing lists

DeepskyLog contains the most extensive databases of deepsky objects, to be used by amateurs. The Messier and NGC / IC catalogs are the most used, but also catalogs such as Stock, Abell, Hickson, Arp, Melotte, Minkowski, Lynds (LBN / LDN), Perek-Kohoutek (PK) and (much) more are available in DeepskyLog. Using these catalogs, every registered user can compile an observing list in DeepskyLog. You can do this for your own use, but you can also make such a list available to other observers. Examples of such public lists are:Astronomical League – Bright Nebulae List, Best of Barnards Dark Nebulae (Steve Coe), Edge-on Challenge List, … There are also many well-known lists, such as the Herschel 400 list and the Caldwell list available

 

Conclusion

It will be clear that maintaining such an impressive, free-to-use online tool is a big job. The work is done entirely by volunteers and as always: they come and go. So there is always a need for extra people, to correct mistakes, to adapt the application tot he ever changing web technology and to possibly add extra possibilities. In particular, there is always a need for new programmers. So do not hesitate to sign up for this and participate in maintaining this unique web application. This is possible by sending an email to the mailing list at deepskylog@groups.io

---

[1] Available on https://www.deepsky.org

[2] Observations before 2007 were added retrospectively, because DeepskyLog didn’t exist before that..

[3] For this we need to register as a DeepskyLog user.

[4] Sky Quality Meter, an instrument that measures the brightness of the sky background in magnitudes per square arcsecond. The higher the SQM-value , the darker the sky.

[5] The higher the contrast reserve, the easier it is to see an object. The limit is a contrast reserve of 0. Theoretically, an object can no longer be seen. Because the calculations assume a uniform light distribution in the object, a bright object core can often still be seen at values of 0 or slightly lower.

[6] Because the map would otherwise be too wide, we have omitted a few columns.