M27 - The (old fashioned) WATEC way!

[Macavity]

M27 - The (old fashioned) WATEC way! 😛

Still persisting with my trusty Watec 910HX eight-bitter... USB Video-Grabber...
GSTAR3 etc. Now using AS!3 to stack 100x (5.12s) hardware integrated images.
As ever 8" f/4 TS (steel) Newt on HEQ5. Post-processing using GIMP 2.8 etc. 

A while since I did any imaging and initially the images went much less DEEP
that they did a few years ago? 🙄 But then I remembered... For "better or
worse" to increase the software contrast to max! (Hey, it spreads the histo). 😸 

Not a lot of Astronomical Darkness so just "Testing" with M27 as the subject.

First the "ordinary image" with no filtering. Note the nebulosity is starting to
"blow out"... concealing stars. If cut deeper, I get into sky background too! 🙄



So I added a Baader UHC filter and 10dB gain to compensate. This is a summation of THREE
different "levels" of processing (lo, med & hi brightness) via GIMP contrast masking macro! 🤔



Something of *my* desired result? Certainly I can now see a fair bit more of the "outer"
regions of nebulosity. As ever and typically a bit rufty tufty with "heat" at the edges?!?
But, checking with stellarium, I find I'm getting to STAR Mag +17... Despite the UHC.

Casually wondering: What is the Surface Brightness of M27? (Anyone know?). Hope 
I can go hunting "grey blobs" (Hicksons... ARPs) again --- When it gets a bit darker? 😍

"If we knew what we were doing, it wouldn't be SCIENCE"?!?! etc. etc. 😸

Edited July 5, 2019 by Macavity

[Martin Meredith]

Nice work getting so much of the fringes Chris. The old kit is obviously still quite capable of delivering good results. Sounds like an interesting process. I wonder if it could be automated, or whether some nonlinear stretch could approximate your three levels?

Martin

[shirva]

Great to see the watec still getting used,, great cameras

[MarsG76]

I take it that it's a old camera..... still quite a good result.. perhaps stack video grabs of less exposure time per frame???

The surface brightness of M27 is Mag 7.4.

 

[Mike JW]

Hi,  

5 hours ago, MarsG76 said:

The surface brightness of M27 is Mag 7.4.

If i understand correctly (and I may not) visual brightness is 7.4 but the surface brightness is about 11. The light from this extended object is spread over a large area thus making its surface brightness somewhat less. I regularly get confused between visual brightness (=total brightness as if it were a point source such as a star) of an extended object and its surface brightness.

Great to see a Watec still doing the business.

Mike

[Macavity]

Yes, certainly Surface Brightness is... "rather different"! Here's a couple of links:
https://tonyflanders.wordpress.com/surface-brightness/
http://www.clarkvision.com/astro/surface-brightness-profiles/introduction.html

The skies around here are "not bad" for the UK visual limit Mag+5 (better)
corresponding to a Sky Background of anything upto Mag +24?!? I know I
can just image small galaxies (stars) to Mag+19 with a (fair bit) of effort! The
surface of some of  common objects can be found in the above. The SB of
M27 is maybe +18. The SB of e.g. M42 in Orion gets to significant values...
like +24! YET can still be imaged with EEVA (this often surprises people!) 😎

From second link above:

In answer to @Martin Meredith I have convinced myself so-called contrast
masking CAN achieve useful gain over simple stretching when the "number
of bits" is limited. You can see how this might be so from this reference:
https://tutorialized-gimp.blogspot.com/2008/12/creating-contrast-mask-in-gimp.html
Basically you obtain a histo without gaps (which give "steps" in greys etc.) 😉

ANYWAY, not trying to make new/significant points, just saying "HI" to a
few "veterans" (I hope they won't mind the term! lol) who also started out
with "integrating" Cams (Like the Watec... Mallincam... ) a few years ago!  😸 

Extended nebulae... Nearby Galaxies (M31, M33 etc.)  are not the easiest
to image. But it is possible to have good results with more compact (and
often more distant) objects! Such is a good thing about EEVA generally? 🙂 

Edited July 6, 2019 by Macavity

[Howie_Oz]

Great result ... makes me want to get the old Mallincam VSS+ out again! One question ... what is AS!3 ???

[Macavity]

On 08/07/2019 at 03:21, Howie_Oz said:

Great result ... makes me want to get the old Mallincam VSS+ out again! One question ... what is AS!3 ???

Heheh... Well. sometimes a post generates an *unexpected* level of interest? 😸
Usually the ones which I feel are a "bit rubbish" or have obvious deficiencies! lol
Sorry to be late returning to your post. AS!3... "Autostakkert" imaging stacking:
https://www.autostakkert.com/ 

In my earlier EEVA days (with Watec etc.) I always used Registax to *stack* the
(already hardware stacked!) farems on .AVI files. Since I began solar imaging,
I have increasinglu used Autostakkert. I provides a plot of image quality... So I
can get some kind of a handle on seeing. AS!3 does seem to require a certain
amount of *contrast* in the image to "lock on" re. stacking? But who knows!

It is for that reason, I tend to "whack up the contrast" in the (Gstar3) image
capture software?!? I sometimes play with the GAMMA setting as well now!
I used to be "scared" of non-default [camera] settings, but sometimes being
able to see a decent (contrasty!) image on screen is not such a bad quide? 😛

Edited July 11, 2019 by Macavity