Pacman with silica gel

[cfpendock]

Thursday night was the first clear sky for a long time here, so I had a go at the Pacman (NGC281).  This image really needs some Ha and Olll, but I only had time for LRGB (16x5 minutes for each).  I was hoping to add some Ha last night, but no chance. Tak and Atik as below. 

 

Whilst observing a refocusing run later in the evening, I noticed the stars didn’t look quite correct and suspected either the collimation was out or the off-axis guider had slipped into the field of view.  However, I continued imaging - skies like that are too rare to start serious investigations.  In any case, the in-focus images looked fine even at 400% enlargement, and the guiding was working very well.

So when I came to put everything away, I found a small bag of silica gel resting up against the objective (I always keep one there in this climate) but had forgotten to take it out when setting up…… I had not noticed it when I had checked the objective for dew because it was on the lower side where I could not see easily. 

 

And I believe that this is the reason for the spikes on the brighter stars which appeared during processing.  Ah well, it’s not the first mistake like that I have made, and fortunately it doesn’t seem to have detracted too much from the image.  Almost certainly I will use the subs again when I get some Ha.

 

Any criticisms would be very welcome.

Chris

[toxic]

very nice indeed 

[Martin-Devon]

Despite the silica gel matter, the image has come out well - there's good colour in the stars and decent definition in the nebula; if you can get some HA this will boost further the detail and resolution so let's see what weather conditions the next week has in store.

Martin

[cfpendock]

Thanks Martin.  Here's hoping for the good weather.........   If we do get a few nights, I may well try the RGB again - I am not entirely happy with the stars, although the whole image of course looks a lot better without the website image degradation.  It makes me wonder sometimes - the images I see on this site which really impress me - what they would look like without that degradation.....absolutely fantastic I would imagine!

Chris

[Brent]

Chris, that's a really lovely image even with the issues you describe having.

With regards to the image quality on the forum, try saving as .PNG. The forum software will accept it and will show it in the post but won't compress (as far as I understand)  it more as it's a lossless format.  I had the same problem posting .jpeg's but my .png's always look exactly the same.

[cfpendock]

Thanks for that information, Brent.  

The problem is that when I save the original image as a PNG (from photoshop), the file size is around twenty times bigger than the best quality JPEG.  

If I save the JPEG as a PNG, it still results in a file four times bigger than the JPEG.

 Is this normal?  Should I first reduce the image size to keep the file small?  My particular problem is that because of my location, I have a very slow broadband speed - around 0.4 Mb/sec, and file transfers take a very long time.

Chris

[laudropb]

Very nice image, especially given your problem. Thanks for posting.

[Brent]

Thanks for that information, Brent.  

The problem is that when I save the original image as a PNG (from photoshop), the file size is around twenty times bigger than the best quality JPEG.  

If I save the JPEG as a PNG, it still results in a file four times bigger than the JPEG.

 Is this normal?  Should I first reduce the image size to keep the file small?  My particular problem is that because of my location, I have a very slow broadband speed - around 0.4 Mb/sec, and file transfers take a very long time.

Chris

Oops, forgot to say, I convert it to 8-bit first.

It sounds daft but I can never see a difference when the 8-bit and 16-bit versions are side by side. That may just be down to my lack of expertise though! If there is a difference I think it generally shows up in gradients and we've hopefully got rid of those in the processing    It is a lot less noticeable than jpeg artifacts are.

Obviously, you'd only do this once all processing is completed, and only for forum display.

Give it a try anyway, you've nothing to lose.

[cfpendock]

Ah, Thanks.  Never thought of that.  Obvious really.......

Chris

[ultranova]

A very nice pacman indeed

on the plus side, having Silica gel on your

objective it wont mist up

well done Paul