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11/30/-1
    
Monday, March 22nd, 2010
Tonight was another shot for M13. Virtually the same setup, but I wanted to try using the WO 0.8x Focal Reducer/Field Flattener and get a real image in with using it.
I have several reasons why I'd like to use it:
1) I own it.
2) I like the idea of speeding up the f/8.8 to f/7.
3) I'd like to use more of the field then I get without a flattener.
4) It holds the camera straight unlike the MPCC which gets tilted in the focuser due to the thumbscrews in both the drawtube and the required extension tube and in turn goofs up one corner of stars.
5) It doesn't require an extension tube so the camera isn't hanging so far back.
6) It has a camera rotator on it.
7) Are there others.... dunno. But these are all good reasons to use it.

So with that said, the gallery has the shot of M13 tonight to compare to the shot of M13 from the last journal entry on the 18th. It's essentially comparable.

Info on the night:
Date: 3/22/2010
Temp: 40F
Seeing: 7/10
Transparency: 7/10
Lunar Phase: Waxing Gibbous, 55% Illuminated
Location: Vancouver, WA
Bortle Scale: 5

M13 Image
This picture is very similar to the one from the 18th. The primary difference being that the field is considerably wider although the presented size of the globular cluster is nearly the same. This picture has more background galaxies in the field because 1) it's a 2.5 hour shot and 2) the field is wider picking up faint fuzzies on the outskirts of the field. That's my kind of image! 

Scope: Vixen ED103S with WO Flat 2 0.8x FR/FF
Mount: Orion Sirius EQ-G with GoTo
Guiding:  Meade DSI Pro and PHD Guiding
Guide Scope: William Optics ZenithStar 66 SD
Camera: Canon EOS 1000D (Modified)
Special Settings: None
ISO: 800
Exposure: 2 hour 30 minutes (15 x 600s)
Processing Software: Acquired in Nebulosity with high dithering, Stacked in Deep Sky Stacker (Kappa-Sigma Clipping for all frames), Levels, Curves, Astronomy Tools, Gradient XTerminator and Noise Ninja in Photoshop
Support Files: 40 flats, 40 bias, one dark used as a bad pixel map
See Gallery below for image



Image Gallery For This Session
01 M13 2h 30m WO08 02 M13 2h 30m WO08 2xDrizz
   

01-M13-2h-30m-WO08.jpg
Click picture above for larger version
If the picture seems too bright or too dark, try adjusting the brightness below.
Brightness:
|
  



Comments:
On 04/09/10 at 06:34pm Miquel wrote:
Man! It is such a beautiful picture!!! Congrats!

On 03/24/10 at 10:56pm Greg wrote:
I have to say that in terms of distorting the star shapes I can't tell the difference between the two. The WO FR/FF image has more detail, of course. We can't really say that the reducer contributes to that by making the focal ratio faster (since the total exposure is so different), but it should make for shorter subs and I always like that.

Even if it weren't for the other factors you listed I would favor the FR/FF over the MPCC just because it somehow isn't right that the MPCC works this way! It is nice to have the choice of reducing or not and get a flat field either way, but the mechanical issues with the MPCC sound pretty nasty.

So how does it happen that the WO Flat 2 works so well when the "improved" Flat 3 is so crappy? Well, we know part of the reason: The Flat 3 was designed to produce a bigger image circle, so they must have compromised elsewhere.




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