Archive for category Deep sky objects

New Mexico Sky: America and Pelican Nebulae with Astrotrac and Qhy8

I was able to escape from the Bay area light dome and spent two weeks in Abiquiu, NM, where I used extensively the Astrotrac Travel System with a set of good Canon teleobjectives and my Takahashi fs60-c.

I’ll post most of the pictures I took – but I was very satisfied with the performance of the Astrotrac for unguided wide field photography.

Photographies were taken either with a modified Canon XTi, or with a Qhy8 CCD coupled to the Teleobjectives.

Here is NGC 7000 and the Pelican Nebulae with the Canon 200mm f/d 2.8 L  Teleobjective and the Qhy8 CCD camera.

It is a combination of 27 exposures of 2 minutes, processed with Dark, biais, and Flat frames.

When coupled with the CCD it is not possible to control the F/D ratio of the Teleobjective, but at f/d 2.8 the lens performance is still honorable and shows sharp stars.

I was able to observe the Qhy8 does a slightly better job in capturing faint details of the nebulae. I suspect it is due to the  pixel size of the Qhy8 sensor (7.8 microns). This  is about 50% larger in area compared to the Canon XTi sensor, and captures in theory 50% more photons by pixel in the same exposure time for extended objects like nebulae.

Below is the cropped image showing details of the Anerica and Pelican Nebulae.  As you can see the image is still full of details when magnified.

Combining 27 frames contributes a lot in increasing the signal/noise ratio. Focus has been done using the real time view of the CCD, and here again advantage for the Qhy8 compared with the Canon XTi. Focus is done by looking in real time at the Full Width Half Maximum measurement on a bright star  – and allows a very precise focusing – which is not a small feat at f/d 2.8.

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Pelican Nebula in HAlpha wavelength

Date: 7/31/2010

San Bruno, CA

Takahashi FS-60C with Qhy9 CCD, HAlpha 12nm Astromik Filter and Astro-tech field flattener.

Auto-guided with 50mm Finder turned into a guidescope and Orion startshoot autoguider

9 exposures of 420sec taken under Moonlight (77% illumination). Thanks  to Narrowband imaging, it is possible to do long exposures under light pollution and moonlight illumination…

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M17 with Canon EF 200mm f/2.8 L II and Astrotrac

Date: 8/9/2010 – San Bruno, California – near the SFO airport

Transparency: 3/6 – Wind between 5mph and 10mph

Mount: Astrotrac travel system

Camera: Modified Canon XTi (Standard IR filter replaced with an astrodon IR filter by Hap Griffin) with Canon 200mm  f/d 2.8 teleobjective (prime lens) opened at f/d 3.5 – at Iso 400.

22 exposures of 90 seconds with Astronomik CLS CCD clip filter, 10 flats frames, 10 darks, 10 biais.

Full Frame

M17 Area – Skytools v3

Cropped Frame centered on M17

Processing:

  • MaximDL5:  darks and flats subtraction, alignment and averaging
  • Photoshop CS4: stretching, selective sharpening
  • Noise Ninja:  noise removal

I used a Bahtinov mask as a focus help on a bright star (Antares).

This is important to use a bright star when using the Bahtinov mask, to have the right in-focus diffraction pattern.

Note that at f/d 3.5 the focusing tolerance is +/- 7 Microns!  See Thierry Legault’s site on this topic.

Interestingly, having the canon not perfectly in focus elongates slightly the stars on the frame edges.

I initially thought the lens was the culprit and using it at f/d 3.5 was “too fast”.

In fact, by having an optimized focus the stars are round on the whole frame! See below – pictures are at 100% size.


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Lagoon and Trifid Nebulae: second try

Date: 8/1/2010 – San Bruno, California

Mount: Astrotrac travel system

Camera: Modified Canon XTi with Canon 200mm  f/d 2.8 teleobjective (prime lens) opened at f/d 3.5 – at Iso 400. Installed on a tripod collar ring and  a Manfrotto ball head.

32 exposures of 90 seconds with Astronomik CLS CCD clip filter, 12 flats frames, 10 darks, 10 biais.

For Flat fields I use an electroluminescent panel from Glowhut.  This is by far the best way I found to take flats that “work” in a consistent way.

This is my second try at this with the same set up. I got much better results this time…. Even though it is taken from my backyard where usually magnitude 3 stars are barely seen. Transparency was a little bit better than usual  – I would say between 3/6 and 4/6 (magnitude 3.5 stars seen at best) and M8 was quite low (below 30 deg.) so imaging was still a challenge!

The big difference with my previous posting is that my Canon XTi has been modified (Standard IR filter replaced with an astrodon IR filter by Hap Griffin) – and the response of the camera in the Red and especially HAlpha wavelength is much better…

Also this time I made sure the astrotrac polar scope had a centered reticule for better polar alignment.

I used the sane  CLS CCD anti pollution filter, same digital processing, and same exposure time as in my previous try. The Astronomik CLS CCD works wonderfully with the modified Canon.

But this time I also  used an “X-Tend a Sight mount” from Photosolve along with an Orion EZ Finder.  It really helps to find and approximatively center the objects in the canon 200mm field of view since seeing stars through the Canon XTi is almost impossible. Then I take a short shot and re-center the object.

In addition I used a Bahtinov mask as a focus help. Focusing the Canon 200mm open at f/d 3.5 is really hard: in a fraction of a turn stars get out of focus. I found the mask to be of some help in getting more consistent results (even though you do not obtain the usual diffraction patterns you observe when focusing a telescope with the mask).

Processing:

  • MaximDL5:  darks and flats subtraction, alignment and averaging
  • Photoshop CS4: stretching, selective sharpening
  • Noise Ninja:  noise removal

M8 and M20 – Canon 200mm Teleobjective and Modified XTi

Details of M8/M20- Cropped image

The following objects can be seen in the field of view: M8, M20, M21, diffuse nebula  Ngc6559, globular clusters Ngc 6544, Ngc 6553, open clusters Ngc 6530,  Ngc 6546

Skytools 3 Atlas

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Trifid Nebula with 8″ Orion Newtonian Astrograph

Date: 7/4/2010

Seeing 3/10 – Transparency 3/6

8″ Orion Newtonian Astrograph with Baader MPCC on Atlas mount

Autoguiding with Takahashi fs60-c and Orion auto-guider

Camera: Qhy8 with CLS CCD – 11 exposures of 360sec

Trifid is quite low on the horizon (about 30 degree) – and being right in the middle of the  city with the SFO airport not very far, the sky glow and turbulence makes imaging quite challenging.

Especially the blue of the reflection nebula is quite hard to isolate from the overall noise – that’s why it is necessary to stack many images to improve the signal to noise ratio.

But thanks to the CLS CCD astronomik filter, and processing with Photoshop CS4 and Noise Ninja, the final image looks acceptable.

Having tested the Coma Corrector from Baader with the Orion 8″ astrograph, I can now tell that once the collimation is perfect (at f/d 4 collimation tolerances are very small), the Baader coma corrector does a great job to obtain round stars across the image, at least for an APS-C size sensor like the one the Qhy8 has.

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Markarian’s Chain with Takahashi FS60-C and Qhy8 Camera

Date: 6/11/2010

Telescope: Takahashi fs60c with Astrotech Field Flattener – Guidescope orion 102ed

San Bruno, CA

12 exposures of 420sec with Qhy8 CCD and CLS CCD – Seeing 4/10 – Transparency 3/6

Processed with Maxim DL5, Photoshop CS4 and Neat image.

Negative


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Eagle Nebula with C9.25

Date: 6/12/2010

Location: San Bruno, CA – near the SFO airport…

Telescope: C9.25 at F/D 6.3 with Focal reducer / corrector

Mount: Atlas Mount with Orion Short tube 80mm and Star Shoot autoguider

Camera: QHY8 – with Astronomic CLS CCD Filter.

17 exposures of 420 seconds bin 2×2 (False color)  – processed with MaximDL5. Dark, Flat field, and biais images were used.

Post processing with Photoshop CS4, Noise Ninja, and Focus Magic.

I used layers and careful processing to make sure details in the center of the Nebula are not over-saturated / lost. It is one of the first picture I processed with Noise Ninja, and I like all the controls it provides compared to NeatImage (another noise reduction program).

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