Archive for May, 2010
I recently acquired the 8″ orion Newtonian astrograph for a couple of reasons:
- Fast focal ratio telescope to reduce exposure time
- Great capabilities given the price – it compares well with a SCT of same aperture but provide a faster optic
- Large field of view compared to instruments of similar diameter
- Lightweight and easy to set up (compared to larger focal length Newtonian)
I use the Astrograph with a Coma corrector (Baader MPCC – Multi purpose coma corrector) – this is a must be accessory for a Newtonian with such a high speed focal ratio. The telescope needs to be thoroughly collimated – but when you get used to it this takes a couple of minutes (first cut with laser collimator and fine tuning on a star).
Look also at the Trifid nebula shot I recently took with the 8″ Newtonian and qhy8 …
Leo’s triplet – 3/19/2010 – 9 exp of 360sec with Qhy8 CCD
This instrument is not meant to be a visual telescope (at least for Planetary observing). I can notice some spherical aberration on mine – but it is not a big deal for deep sky photography at focal plane (at least for the average conditions I have on my observation sites).
This telescope excels in Nebula and Galaxy clusters. For planetary nebulas , or details in small galaxies, a larger focal (e.g. the one you have with a C9.25″ at f6.3) performs better.
I used a couple of time CCD inspector from CCDWare with it to optimize the collimation. This is a fantastic product allowing you to collimate the telescope in real time while the CCD camera is attached to it. You do a rough collimation first – and then fine-tune the collimation with CCD inspector in real time. It can be used with any telescope, but this program is particularly useful with fast telescope where collimation has to be done within high tolerances.
Ngc 4565 – Needle galaxy – 3/6/2010 – 19exp of 165 sec – Canon XTi
M86 – Part of Virgo Galaxy cluster – 5/6/2010 – 18exp of 360 sec with Qhy8 CCD
(collimation was far from perfect there … stars become donuts on the egde..)
M1 – Crab Nebula – 9exp of 240sec with Qhy8 camera
I compared pictures of the same objects taken with my Orion 102ED refractor, and not only the images are much brighter, but they capture many more fine details with the 8″ astrograph.
The Full Width Half Maximum (FWHM) of stars is significantly better with the 8″ astrograph as well (even though not taken with the same Camera – Canon XTi with the 102ED, and Qhy8 with a larger pixel size for the 8″ astrograph).
The comparison stops there – the Orion 102ED refractor is a very versatile instrument, that is very easy to use (no collimation, no significant cool down time for the optics), and the 8″ Astrograph is not so much for beginners and is dedicated to deep sky astrophotography. So far I am very satisfied with the 8″ astrograph – it is a telescope fun to use – and of great quality / price ratio.
This picture of M51 was shot in San Bruno, CA, near the airport.
Telescope: Celestron 9.25″ SCT with Celestron f.d 6.3 corrector / reducer
Camera: QHY8 CCD cooled down at approximatively -40C
Filter: Astronomik CCD CLD
Composite of 6 images of 360sec and 17 images of 240sec.
Software: Photoshop CS4 and NeatImage. I applied high pass filters to enhance contrast in the Galaxy spirals and use Astroart deconvolution to enhance details.
My new camera QHY8 is really amazing – small in size, very easy to use, with a large CCD sensor, and so few noise that I don’t need to shoot each time dark frame. In fact the noise is so low I barely notice the difference when calibrating with Dark frames.
I am always in the quest of improving my deep sky imaging and battling with light pollution. Many nights, the best magnitude I can visually see is between 3 and 4… The skyglow of the city, San Franciso airport, and close caltrain station surround me… I tried different ways to improve contrast by using different light pollution filters and narrow band filters..
I am impressed with the performance of the Astronomik CLS CCD filter. It really reduces the light pollution, filtering the city lights, but let critical wavelengths such as OIII passing through. I was able to compare with other filters such as the Orion Skyglow photographic filter, and even through the Orion filter allowed me to take nice pictures (see the Pacman nebula with an Orion 102ED, Orion Skyglow filter, and Star Shoot Pro II), the Astronomik filter blocks light pollution to a greater extent and allowed me to do exposures of +6 minutes even with short focal ratio (f/d 4), and this without saturating the image.