August 28, 2010: Jupiter and Moon with the new Ritchey-Chrétien
¡UPDATE!: The Jupiter photo in this page has been awarded with the first prize in the Astrophotography Contest of the XIX Spanish Astronomy Conference.
Checking Internet one realizes that one of the most common ambitions of any amateur astronomer is to have an observatory. A place where you can easily observe without the hassles of mounting, connecting wires, adjusting your alignment in every observing session. In fact we are pretty sure that the best observatory is not the one with the best sky, less light pollution and best seeing but the one which you can use more often. Professional observatories don't choose their location in places with better sky but in places where the sky is good the maximum number of nights. Nights with good seeing conditions are almost everywhere and the important thing is to be there even if it is not a weekend or holidays.
From the beginning of the “La Azotea” project of making astronomy from a urban environment we have tried different places: Granada, Armilla and currently Churriana de la Vega in an attic oriented to the East. After some observation sessions we have noticed that Vega de Granada (a flat area near Granada, where Churriana is located) even having quite heavy light pollution presents some quite good seeing nights.
Thus, we are in the process of establishing our urban observatory there. We want to use it for both deep sky photography (using narrow band filters) as well as for planetary and lunar photography. As we need our set-up to be compact (we don't have a lot of space and to better protect it) we have decided to use a Cassegrain configuration with 2 small ED refractors (our Sky-Watcher ED80).
The only element that we didn't have was the planetary telescope with a high f. Searching Internet we found the opportunity of acquiring a 8'' Meade LX 200R (currently the model is called ACF) for a good price. This telescope has a quite good coma correction and optical quality. Its main features are:
- Modified Ritchey-Chrétien configuration (Meade has added a correction plate)
- Aperture: 8''
- F 2000mm
- f 10
- UHTC (Ultra High Transmission Coatings)
To attach all the optics to a single equatorial mount (the EQ6 Pro) we made an aluminium plate were the three telescopes and the guiding scope are fixed. Moreover, we have make an extension tube (made of aluminium) to achieve focus in the video cameras. So, our final configuration is the following:
- LX 200R + Webcam SP900 or QHY-5
- ED80 + field flattener + Canon EOS 300D
- ED80 + field flattener + QHY-9 + narrow band filter wheel + autofocus
- Guiding solution from Lunático
The size of the whole set-up are less than 1m x 1m x 1,5m and in the near future we are going to construct a detachable box to isolate it from bad weather conditions (we will show it here once it is ready). Its main advantage will be to preserve the alignment and to avoid the disorder of the optics.
We have made some tests to check the quality of our last acquisition and the stability of the set-up. In the following we show one the results with whom we are more satisfied after a good seeing night for a urban environment:
It is not our first Jupiter image. In fact, in our first attempts we were a little careless with some aspects that are crucial to obtain a good quality image. For example, collimation of the optics is basic and thus, we have decided to check it in every planetary session. An image is as good as the worst of the elements involved in the capture. So, every factor that we are in control of should be revised and ready. In the following video you can check that seeing conditions were quite good (at least for what we are used to):
We also tried to take a picture of the Moon:
Another important factor has been to learn to process the obtained videos. Our personal taste guide us to obtain images where fine details are shown and where coarser features do not look over-processes, as it is quite common in many images that you can find on the Net.
Finally, our experience has lead us to create the following “recipe” for planetary observation sessions:
- Check hard disk space (you'll need MANY Gb)
- Check polar alignment (to avoid drifts in the videos)
- Achieve good acclimatization (preparing the telescope at least one or two hours in advance)
- Check collimation (very important!)
- Check focus and, if necessary, go to step 5
- Use a small ROI to get the maximum number of frames
- Record during a small amount of time to avoid the rotation effect
- Be careful with processing (we will write about it in the future), you should not try to get detail wher e there is not
- Hey! Did we mention focusing?
In the next images you can see the Airy disks of Vega , stacked with Registax, after collimation with Metaguide and Europa and Ganymede from the same night. We were surprised (though we shouldn't) that when we takes into account each and every one of the factors involved in the global image quality, the result is much higher.
A future project that we have in mind is to capture the planet's rotation along one night.
But that's another story...!