Jump to content

Banner.jpg.b89429c566825f6ab32bcafbada449c9.jpg

I give up - I need to Guide. Pls advise.


Spacehead

Recommended Posts

6 minutes ago, kens said:

Right click the link and Save link as... worked for me

 

1 minute ago, Spacehead said:

Geof I dont know whats wrong there - I have checked, its uploaded in Binary mode and its a directly output file from DSS - completely untouched with any other software.
Have you tried right click save as, because if your browser doesnt know how to display fits - it may simply display its content in ASCII or something.

ok, right click worked thanks both, but my astroprocessing software ImagesPlus won't open it. I got it open in MaximDl, but the image is green, so I'll keep trying.....

Link to comment
Share on other sites

  • Replies 92
  • Created
  • Last Reply

HappyKat - Yes - the flats were at 200 - the reason being that the tutorial I read said use below 400 or 400 - and by combining 200ISO with the maximum dimness setting on my flat screen computer monitor (which is what I used to produce the flats - so scope with tshirt up against monitor) and a shutter speed of 40% of 1 second, I was able to attain 50% mean which was as close as I could get to the suggested 51%.  The tutorial said that I could be +- 5%.

Interestingly, the program I used to check the mean of the pixels would not read the cr2 (does anything lol) - so I took JPEG and CR2 flats, and attained the mean from the JPG which in theory should be the same as the cr2.  Naturally I am using the cr2 for the stack though.

The system which provides the mean is free - called astroimagej.   The numbers it provided on my laptop for the jpeg were 
min-0 black-113.00 mean-128.01 white-173.02 max-255    So mean as a % of 255 gives about 50% - so whilst people say lots of different things about flats, such as 30% for example - I just worked with the 50%.  Obviously I am open to suggestion.

I have flat sets now though - lots of them - some of which are too bright - but AFAIK i have the odd set at 30% aswell just in case.

TBH - I have stacked with the 30% and I found the 50% better.

Link to comment
Share on other sites

I'll bow out on flats can't say I measure that, I've just gone on only altering exposure length to get histogram in the middle. But you have greater aims and are going for more so I can't comment further on approach to flats. I'll try your fits file later.

Link to comment
Share on other sites

The ISO of flats is not critical nor is the temperature but DSS does complain if they are not the same.
In fact use a low ISO for best SNR.

If you use flat darks they must match the ISO and temperature of the flats.
 

Link to comment
Share on other sites

1 minute ago, wxsatuser said:

The ISO of flats is not critical nor is the temperature but DSS does complain if they are not the same.
In fact use a low ISO for best SNR.

If you use flat darks they must match the ISO and temperature of the flats.
 

I know this is a topic for debate, but it is what I do when imaging with a DSLR. I shoot my flats and flatdarks at ISO100 regardles of which ISO I shoot my lights. ISO for Darks and Bias though always match the lights.

Link to comment
Share on other sites

Great - thats what I needed - the images show the intensity of the nebula which is available in the image..... for bringing out before distortion of surrounding items (stars).
Its a problem I have encountered on this set too - the more I bring out the Ha, the more the stars bloat - so it seems to be a compromise.  Thats after about 30 hours of messing by me.

I think the solution, (whilst HUGE progress has been made here) is the transition from tracking to guiding - whereby hopefully longer subs and more of them will increase the Ha intensity and reduce the need for harsher stretching and fiddling which causes the bloat on the stars.  Thats what I'm thinking along the lines of - nothing scientific yet!!!

Learned TONNES from this thread - a huge thankyou!  From flats, to layers, to tracking issues the list is endless of what ive learned here - so I hope others find it useful too.

My next "mitherings" will relate to Guiding.  I'm sure to fall all over the shop on that one too - but with patience come the winter I hope to be set up and well practiced on guiding so that I can get those stunning shots of the Horsehead and others.  Thats my goal for the moment.

:)





 

Link to comment
Share on other sites

10 hours ago, spillage said:

Nice Kat. What do you use to keep the two bright stars under control. Mine keep bloating out..:BangHead:

Star mask, though it was easy when stretching to make them ghastly, if I play again and it's much better I'll share it and the log.

Link to comment
Share on other sites

24 minutes ago, Spacehead said:

For Geof - a visual representation on my machine of the flat samples I have been using.
viewflat.jpg

Cheers

Thanks. That looks better than what I saw when I downloaded the .cr2 and opened it in ImagesPlus, where the image was much darker. My concern would be that the JPEG you posted is a stretched image and not what you'd use to calibrate the raw light frames. This is what I saw in ImagesPlus, image on the left and histogram on the right.....

Mark-Flat.thumb.JPG.1756f84265c2e3861699ad95db4c8ea1.JPG

The histogram (displayed in 8 bit) shows the correct bell curve for the vignetted image, but its too far to the left (only 10% from the origin) whereas I'd want to see the peak of the curve some  30%-40% along the X-axis.

Maybe I did something wrong when I downloaded and converted it in ImagesPlus, so I'd be interest to hear what others though about the .cr2 flat that you posted.

Cheers, Geof

NB ignore the reference to 11% in the image header - that is just the display size on my laptop screen.

Link to comment
Share on other sites

Well this is my poor effort. Thanks to @happy-kat for the previous work flow. Until this I was always an autodev guy but loving the manual dev. I have no real idea how this will look as at work on a ancient laptop. Definitely not as good as other here and probably a bit on the grainy side. 

 

test2.jpg

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.