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Posts Tagged ‘FSQ’

Testing out the Takahashi FSQ 0.73 focal reducer on the Virgo Cluster

May 31, 2014 3 comments

I recently purchased the 0.73 focal reducer “QE”for my Tak 106ED. It promises to turn it from a speedy f/5 to a ridiculous f/3.7 while still filling a full frame sensor. In fact, with the full frame sensor of the STL-11000M, we’re looking at a field of view of 5.3 x 3.5 degrees.

Of course any new purchase like this causes days of clouds and rain, but that’s been the case for about six months anyway. It gave me time to order the insanely priced adapter required to mate it with the STL camera. Once I had a clear night, I seized it, even though it was a full moon. Because of this, the image you’ll see below is far from optimal. Consider it a test image more than a aesthetic image (though the effect is still pretty cool). I fought a valiant battle with gradients in PixInsight, but for the most part they got the best of me.

Wide Field of the Virgo Cluster of Galaxies

Wide Field of the Virgo Cluster of Galaxies

Even after cropping a little, that’s a WIIIIDE field. Looking in detail at the extreme corners, the left side showed a little distortion, but that could potentially be due to some non-orthogonality in the connections.

Extreme corners of the image

Extreme corners of the image

Overall, the image is very sharp, and it’s a pleasure to capture a field that would normally require a mosaic. I look forward to the beginning of narrowband season to really give this new system a try.

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NGC 6888 Narrowband (plus some PixelMath)

September 29, 2013 Leave a comment

Finally, some color images!  (Or at least false color.)

This is one panel from my earlier Crescent Nebula 4-panel H-alpha mosaic, with OIII and SII data added.  The first version is in a slightly modified “Hubble” narrowband palette (R=70% SII+30% H-alpha, G=100% H-alpha, B=100% OIII).

NGC 6888 in Hubble Palette

NGC 6888 in Hubble Palette

Image data:
Exposures: 13 x 1200s Ha, 16 x 1200s SII, 18 x 1200s OIII (Total exposure time: 15 hours, 40 minutes)
Software: guiding by PHD, stacking in DeepSkyStacker
Processing: PixInsight 1.8
Telescope: Takahashi FSQ-106ED (530 mm f/5)
Camera: SBIG STL-11000M with Astrodon 6nm narrowband filters, 2×2 binned
Mount: CGEM
September 16, 17, and 28 2013

PixInsight allows you to easily blend and mix images or color channels to create alternate palettes, so let’s use this image as a simple example.  Consider the following simple PixelMath parameters.

PixelMath

PixelMath refers to the color channels in an RGB image as [0], [1], and [2] respectively.  So this tells PixInsight to create a new image with the:

  • red channel composed of the original green channel
  • green channel composed of 70% of the original red channel + 30% of the original green channel
  • blue channel unchanged

The result is a false color image with a different flavor.

NGC 6888 Red-Green Reversed

NGC 6888 Red-Green Reversed

Sh2-129, The Flying Bat Nebula

September 28, 2013 Leave a comment

This is another monochromatic image I captured while the moon was near full this month. Sh2-129 is a very dim, but very large H-alpha region at the bottom of Cepheus. It’s close to the far brighter and more famous IC1396, which explains why it is so often overlooked among the sea of emission nebulae in that area. I’ve seen it referred to as the Flying Bat Nebula, but it probably has more claim to be a “Tulip” nebula than Sh2-101. This is definitely a challenging object to capture.

Nicola Montecchiari recently captured a terrific image of this nebula with the OIII-emitting planetary nebula OU4 at its core.  Looks like I will have to go back and capture some OIII data here soon!

Sh2-129, The Flying Bat Nebula, H-alpha

Sh2-129, The Flying Bat Nebula, H-alpha

Image data:
Exposures: 19 x 1200s Ha exposures
Software: guiding by PHD, stacking in DeepSkyStacker
Processing: PixInsight
Telescope: Takahashi FSQ-106ED (530 mm f/5)
Camera: SBIG STL-11000M with Astrodon 6nm narrowband filters, 2×2 binned
Mount: CGEM
September 15, 2013

The Moon and Venus

September 8, 2013 Leave a comment

Sometimes when you’re setting up to take pictures of incredibly dim things, the sky presents you with something incredibly bright and beautiful. The moon and Venus were in conjunction in this evening’s western sky. I used an H-alpha filter as a sort of 99% neutral gradient filter so they wouldn’t overwhelm the sensor.  This is a single 0.2 second exposure, through a 6 nm H-alpha filter, with the STL-11000M on the FSQ-106ED.

Moon and Venus
The Moon and Venus in Conjunction (9/8/13)

For perspective, tiny little Venus there is actually 3.5 times bigger than the moon, but 415 times further away. The light from the moon took about 1.3 seconds to get here; the light from Venus traveled for almost nine minutes.

A quick evaluation of the NP-101 for use with the SBIG STL-11000

November 10, 2012 Leave a comment

I recently purchased an SBIG STL-11000, and my biggest concern was whether buying a camera with such a large sensor was going to require me to buy a new telescope to cover that sensor.  My main scope is a Televue NP-101 (the non-is version), which means I have to shoot through the 2″ focuser.  While I’d trade up to the NP101-is or even a Tak FSQ-106 at the right price, let’s face it:  those are very expensive upgrades.

Last night was first light with the new camera, and I’m posting this information to help others make a similar decision.  Two important caveats here:

  1. Focus was a little off.  I think I need to recalibrate FocusMax, and this was just meant to be a “first light” test of the camera. So compare the relative sharpness of the corners, not the overall sharpness.
  2. No polar alignment was done, so there is a little field rotation evident.

First is the question of whether the NP-101 can deliver sharp stars all the way out to the corners.  Let’s have a look at the full image first.

This is 18 10-minute exposures taken through a luminance filter, synthesized in DeepSkyStacker.  When I loaded up the files in Photoshop, it was impressive to see their scale:  4000 pixels across!  Now, let’s look at the corners:

This is sharp enough for me, especially with the field rotation evident.  I am really impressed with the edge performance of the NP-101.  At this point, I’m not seeing a need to upgrade to the FSQ or 101-is.

Second, we have to consider the light fall-off.  I braced myself for considerable vignetting.  Here is the master flat with levels on an 8-bit scale marked in green:

Again, to me this is acceptable performance, though less than ideal.  There is about a third reduction in light at the corners versus the center.  That’s a lot, but it’s not nearly as bad when you move just a little bit inward.  I figure with the usual cropping and overlapping of frames that happens, this won’t be much of an issue.  It’s almost the same levels of vignetting I’ve seen on the ST-8300’s chip when using this scope at f/4.3 via the reducer.  Careful processing there proved that the vignetting wasn’t a problem.

So what’s the verdict?  The NP-101 is perfectly acceptable for use with the STL-11000.  My guess is that the -is version with its larger focuser would perform better, but until I see a deal on one of those, I think I can happily image with this combination.  If anyone has similar information for the STL-11000 with either of the Televue -is scopes or the Tak FSQ scopes, please post a comment for comparison.

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