Archive for February, 2011

Rosette Nebula in Narrowband with Stellarvue SVR90T

Location: San Bruno, CA

Telescope: Stellarvue SVR 90T with Televue x0.8 reducer on Takahashi NJP-Z Mount

Camera: Qhy9 CCD with Astronomik H-Alpha 12nm Filter and OIII 12nm Filter

H-Alpha: 20 exposures of 480sec on 01/22/2011

OIII: 26 exposures of 480sec on 01/21/2011

The pictures uses H-Alpha for Luminance, Red, and OIII for Green and Blue – and took a total of 6 hours of exposure. The regions rich in H-Alpha emission are red – but note the rosette nebula emits  quite considerably also in the OIII band – making the central regions appearing withe.

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B33 / Horse head and Medusa Nebulae with 8″ Newtonian in H-Alpha

Location: San Bruno, CA

Telescope: Orion Astrograph 8″  on Takahashi NJP-Z Mount

Camera: Qhy9 CCD with Astronomik H-Alpha 12nm Filter

Another series of H-Alpha images this time with the 8″ Orion Newtonian Astrograph.

Once the telescope is well collimated, it produces good images along with the Baader MPCC coma reducer.

The B33 / Horsehead image is  a composite of 14 exposures of 390 seconds, processed with Maxim DL v5 and Photoshop CS4.

B33 / Horsehead on 2/10/2011 with 8″ Newtonian telescope

The next picture is the more challenging Medusa nebula (planetary nebula).

This nebula was discovered in 1955. It has a very low surface brightness.

The technology to record Hydrogen Alpha images became after World War II (source: galaxymap.org).

I assume this combined with the very low brightness of this nebula is one of the reason why it was discovered relatively recently.

By comparison, it is quite easy to see the shape of the Nebula with one sub-exposure of 6min done with my 8″ telescope in 390sec amidst the City light!

The image is a composite of 15 exposures of 390sec, combined with Maxim DL 5 and processed with Photoshop CS4.

Sharpless 2-274 / Medusa Nebula on 2/9/2011  with 8″ Newtonian

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Jellyfish, Cone and Rosette Nebulae in H-Alpha with SVR90T

Location: San Bruno, CA

Telescope: Stellarvue SVR 90T with Televue x0.8 reducer on Takahashi NJP-Z Mount

Camera: Qhy9 CCD with Astronomik H-Alpha 12nm Filter

Even with the short focal ratio (f/d 5.6) obtained with the televue reducer, I had to apply 2×2 Binning and take a fair amount of exposure to get details in the Nebulae.

The H-Alpha filter does wonder to combat light pollution, even though the FWHM of this filter is not very narrow (12 nanometers).

Some words about the combination of Stellarvue SV 90T and televue reducer. I had to find the best distance between the CCD chip and the reducer / flattener. Initial trials with a distance of 58mm were not successful. Then 55mm of distance between the CCD chip and reducer/flattener seemed to yield better results.

My tests were done with the Qhy9 having a relatively small sensor (15mm x 19.7mm)  – and even with this sensor size stars were not perfectly round on the egdge.

That’s why I am not sure if the televue 0.8x reducer/flattener is a good match with the Stellarvue SV90T for large chips. But at least in my case it turned out fine. On the other hand, the Stellarvue flattener gives perfect flat images with round star till the edge with an APS-C size sensor … but … the F/D is still at 7,  making it more difficult to image faint extended objects. That is why  I opted for the Televue reducer for this set of images, even though it does not produce a perfect flat field with this telescope optics.

Jellyfish Nebula (IC 443 or Sharpless 2-254)  – 01/28/2011

Cone Nebula / Christmas Tree Cluster  (Sharpless 2-273Ngc 2264)  – 01/28/2011

Rosette Nebula (Caldwell 49, Sharpless 2-275) – 01/22/2011

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