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Posts Tagged ‘np-101’

M31 – The Andromeda Galaxy

November 14, 2012 Leave a comment

After taking the luminance exposures that were intended to be a test for the new STL-11000M, I couldn’t help but dig up some old DSLR exposures of M31 and merge their color data into the image.
This is 18×10 min luminance with an SBIG STL -11000M through an NP-101 at the native f/5.3 combined with color data from 169×4 min (11+ hrs!) taken with a Canon 450D through an 80 mm refractor at f/6 last November.

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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.

M42 Orion Nebula in Narrowband

February 5, 2012 1 comment

Some weeks, everything goes wrong.

To quench the never-ending thirst for more concentrated photons, I sold my previous scopes so I could trade up to two high-end, fast refractors:  a Borg 77EDII at f/4.3 and a TeleVue NP101 at f/5.3.  I seized rare opportunities to get both used and at great prices.  Only if a Tak FSQ came my way would I have room to improve in the short focal length department.  But with all new scopes come new problems.  The NP101 needed rings to sit on my mount, and an adapter for my stepper motor to control the focuser — $200 and two weeks.  The Borg needed precise spacers to fit my camera, and I’m still working out other kinks — $100 and at least two weeks.

Now I find out that my SBIG’s cooling is not functioning correctly, so basically every piece of imaging equipment I have is “in the shop,” in one way or another.  But sometimes even with adversity, something fun or beautiful slips through.  I took the NP101 out on a hazy, moonlit night because I really wanted to start working with narrowband data.  The obvious, reliable target sat just above my roof:  M42.

The world needs another image of M42 like a hole in the head, but I couldn’t resist.  Before it set, I grabbed two hours of narrowband exposures, and here is my very first narrowband image:

Stats:  SBIG ST8300M, Baader filters, TeleVue NP101 on a CGEM

6x300s H-alpha, 10x300s O-III, 12x300s S-II, 25 flats, NO darks

Stacked in DSS, process in Photoshop CS3.

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