Re: [APML] Horsehead and Pleiades testshots with 6x9 camera/OAG and BRC

["tan@home.com" <tan@home.com>]

Matt,

	Yes, it is grain and not due to compression. I am not compressing the 
images much. In your experience, are you expecting a whole lot less 
grain with 3-5 stacks? Maybe it's my processing or enhancement. Sure, I 
can upload higher quality jpegs. I will email you privately when I have 
done this later.
	I have thought about tricolor TP at f/5 but I do not have any filters at 
the moment. It would be nice to use filters with better transmission 
qualities than the Wratten ones. Also exposures would be very long.
	The star halos gradually get less symmetric as you go from center to edge 
of frame. I am very reluctant to attempt collimating a RC. When I look 
at the diffraction rings on axis, they appear virtually concentric so I 
think it is almost perfectly colimated, at least I think so.

Loke


Matt BenDaniel wrote:

> Loke,
> 
> You're putting in a lot of time in AP, aren't you? But I guess I'm
> "calling the kettle black". <g>
> 
> These are excellent images.  It's very impressive how quickly you're
> getting this new setup working.
> 
> You're stacking a lot of PPF frames, but the grain is still evident (or
> is just compression artifacts).  Have you considered doing tricolor TP
> at f/5?  That's slower than you're used to, but still a lot faster than
> what most others have.  Also, can you upload higher quality JPEG?  I see
> compression artifacts.
> 
> Looks like it needs a bit of collimation; the stars halos aren't
> symmetric.
> 
> The Pleiades shot is nice and deep.  I love the diffraction spikes!  I
> don't care what SOME people say. <g>  Again, JPEG compression
> artifacts.  Also, some vignetting.
> 
> The horsehead shot looks a little dark to me, or maybe just vignetted.
> 
> The color balance in both shots is superb. You have an excellent eye.
> 
> 
>>From: <tan@home.com>
>>
>>>Just got the chance to try out the Mitsuboshi 6x9 camera with OAG on a
>>>Tak BRC250. Here are shots of the Horsehead and Pleiades Nebulas which
>>>are cropped from a full 6x9 frame:
>>>
>>>Horsehead:
>>>http://www.starryscapes.com/nebula/horsehead.html
>>>
>>>Pleiades:
>>>http://www.starryscapes.com/clusters/pleiades.html
>>>
>>>These were processed rather hastily and should be considered work in
>>>progress.
>>>
>>>A single full frame of the Horsehead (1 hour exposure) can be seen here
>>>for those interested. The large version is really large so beware of
>>>long downloads. The small version suffices if you want to check out
>>>illumination. The larger version is better for seeing stellar spot sizes.
>>>
>>>Small 178kB version:
>>>http://www.starryscapes.com/tmp/hh2_small.jpg
>>>
>>>Large 903kB version:
>>>http://www.starryscapes.com/tmp/hh2.jpg
>>>
>>>As can be seen, there is vignetting at the very edge of the corners.
>>>This could be attributable to some form of obstruction, but this is only
>>>a guess. Since it is rather small, I do not think this to be critical.
>>>Also noticeable is some gradual light dropoff.
>>>
>>>I have not empirically measured the stellar spot sizes of this
>>>combination but I can tell they are small. Please judge for yourself.
>>>Also noticeable is the fact that there is somewhat of a degradation of
>>>spot sizes towards the edge of the 6x9 field.
>>>
>>>Anyway, I thought this information might be of interest to someone.
>>>
>>>Loke
>>>



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