The RASA 8 already proved itself as practical and easy to operate in the first tests. Without annoying mirror shifting I could focus the camera (Fujifilm X-T3) within one minute. Thanks to the very fast f-ratio of the RASA 8, it is even possible to focus on average bright stars in the field of view, without having to point the telescope at a bright star.
No collimation was necessary after unpacking and mounting the instrument (the telescope seems to be very resistant against shocks and temperature changes). The star image in APS-C format is perfect down to the corners of the image. Due to the high light intensity, very short exposure times of less than 30 seconds and low ISO values can be used, as in the image shown below. This accelerates the image acquisition and increases both quality and comfort, since you don't need the perfect aligning of the mount to the celestial pole and don't have to bother with tracking errors and a parallel mounted guiding scope.
The RASA 8 is one of the few instruments that I know that are a very good choice for the ambitious astrophotographer as well as for the beginner. A top price-performance ratio for an extremely fast instrument which shows very fine stars, the RASA 8 is unrivalled. The RASA 8 is one of the best instruments I can imagine to capture large, dim gas nebulae in great detail on the chip.
The Cirrus-Nebula in Cygnus. The area fits completely onto an APS-C-sensor when used with the RASA 8. The exposure time is ca. 70 minutes (141 x 30 s) with a Fujifilm X-T3 (ISO 800) and a Celestron RASA 8. The image was taken at Spicherer Höhe close to Saarbrücken in Germany.
We are happy about the positive feedback we received.
For this test, Sebastian Voltmer got a Fuji X-T3 by our Celestron dealer Fotohaus Wiesenhavern. We would like to thank him very much for this.
Hi there,
Very informative article, especially for me as I really like using Fuji XT cameras. Im just wondering if attaching the Fuji to the front of the RASA needed any extra hardware or spacers? Also, what mount did you use? Cheers,
For the Fuji, you need the Baader Wide-T-Ring Fujifilm X with D52i to T-2 and S52 # 2408331. The adapter from the RASA to the T-2-thread is already included with the RASA. You also need to leave the clear glass filter which is mounted in the RASA at its place (or install another filter) to get to the right distance; the thickness of the filter is part of the optical design.
We do not not know which mount was used for this image, probably a 10Micron GM2000 HPS - but the good thing about the RASA are the short exposure times, so that tracking errors are not much of an issue.
Hi,
I'm a little confused by this. The article seems to indicate that the XT-3 will fit the RASA by using the Baader Wide-T-Ring but, in the questions section of that item's page, it says that the combination is 'unluckily 1mm too short' to meet the RASA's very critical back focus. Does that 1mm not affect the focus?
thanks
Unfortunately this is a question that it is not very easy to answer. According to the manufacturers specification Fujifilm as well as Celestron, the optical length of the adapters and the camera flange to chip distance is one mm too long, or the backfocus 1 mm too short. However the tests on the field that Mr. Voltmer has done, showed that this distance is not so criticall. It can be that due to the tolerances, the telescope that Mr. Voltmer tested, allows it to work, but another specimen might be too close to the tolerances, but yet unable to achieve a perfect image.
The main issue with not being able to respect this distance, is not the focus itself rather than unwanted effects like unround stars for example. By such a small difference from the recommended backfocus, it should be visible only on the stars near the edges, which can be taken out with editing software. However there are people that don't want to make this compromise.
That is why we have both answers on our website, so the clients can decide for themselves.