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Messages - dpaul

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General / Benefit of Drizzle?
« on: 2018 October 03 17:58:25 »

Can someone give me advice on whether adding drizzle files during integration will ''in my case'' help?  I have a 30'' F3.5'' scope which when used with a Paracorr means the focal length is just over 3 metres.
I'm using a CMOS camera with 3.8 pixel size and using 2x2 binning. I know this is seriously over-sampled but I'm generally happy with the results, aided by the superb optics from Mike Lockwood.

So here's my question - I think I've seen Juan's original announcement of adding Drizzle in 2014 and there may have been comments where it helps with ''under-sampled'' images. So in my case would I expect any benefit?  I'm still confused about what drizzle is really doing but doesn't it make the image less ''grainy''?  I tried redoing an image for the very first time by adding drizzle files (there were plenty of frames, 25 in this case and I used linear rejection during image integration). It did seem to make a small difference, a little less noisy maybe?

Any comments from experienced users are very welcome. Sometime I use 3x3 or 4x4 binning with narrowband so would that be more beneficial then?



Gallery / IC 5146 (Cocoon Nebula)
« on: 2018 August 07 16:05:30 »
Attached image was taken with an Atik Horizon CMOS camera - LRGB filters.
Scope is 30'' F3.5 with Lockwood optics on an 'unguided equatorial platform'.
Each frame was 25 seconds and about 20 frames integrated per filter.

Technically speaking with a 105'' focal length and 3.8 pixel size this is seriously over-sampled. I used 2x2 binning which helps reduce star bloating.


« on: 2018 July 20 17:41:51 »
Hi John

Apologies for the slow reply - Unusually for me I haven't logged in for a while (too many clear nights in last 4 weeks).

thanks for the advice


« on: 2018 June 27 14:21:08 »

I've been taking narrowband frames of M57 and also using a 2x Powermate to increase the image size. The frames are good but there are not that many stars in the field but still enough (I hoped) for star alignment. However, no matter what settings I use, I can't get star alignment to work, or at best I got about 20% of the frame sto align.

What is best settings for the most difficult cases - the other probelm is that HA and OIII by their nature also reduce the number of visible stars.

It all works without the powermate but not with it.

Is there a way to manually selct the reference stars?


« on: 2018 June 19 12:22:46 »
Thanks Rick

If you don't use it often maybe it would happen again with continuous use


« on: 2018 June 18 13:22:14 »
Hi Rick

Thanks for the reply - I can see Juan has made earlier reference to potential issues with Dell graphics and also possible ''poor windows 10 updates''.

I'll have to manage ''as is'' for now.

If anyone else has input on their experience, would be good to if the same machine and / or operating system as I have. I have a Dell XPS (30 Ram, I7 processor, 4K screen)



« on: 2018 June 17 16:36:07 »

This is a well documented topic on the forum.  I have the latest update of PI and use a Dell 30 MB Ram / I7 laptop with Windows 10.

I've had the ''access violation'' error come up on and off over the last 6 months. Some times I can use PI on several occasions and I never get the problems. Other days (like today) is happened about 8 times.

As already documented by others, it does help if PI is properly closed down after use (not just using the 'X'). Even doing this I can still get the error part way through a PI session.

I wanted to share my experience because there are 2 distinct processes which tend to cause this problem for me, they are ''dynamic crop'' and dynamic background extraction''.  Is it possible there really is some kind of bug?

It would be useful to have a survey of PI users to ask how many have had the problem, how often and any trends in when it happens.

I love PI so apologies for this note but it is very very frustrating - I hope there is a solution within PI itself?

One question - recent PI updates only were minor ones, wasn't there meant to be a major one soon?
The version I have is



Thanks Juan,

I'll be patient until the new software update - its only happening some of the time !
Yes, windows 10 can be very annoying!!!!!!!!!!!!


Thanks Rick

I'll keep an eye open for this - last night I did get the problem again during the same session after using it for an hour - so it is intermittent.


Hi Rick

That's the problem - its intermittent / unpredictable.

It seems to happen most often after exiting the program following a lengthy processing period then restarting soo afterwards.

I'll try to look for trends



I've been getting this same issue for about 6 months now (I have the latest version of PI). Laptop has 30 RAM, i7 processor and disc less than 50% full.
I can use PI for hours then after closing and re-opening it has the access violation error until I've closed and re-opened a few more times.

Often certain processes seem to cause it - Dynamic crop and Dynamic background extraction seem the worst culprits.  I can live with this but I'm always saving data regularly in case it bounces me out.

I love PI and don't mean to be critical but so many people seem to mention this, surely it must be a bug in some way. Nothing else I do ever causes this.



Hi Wim,

Thanks for the note -

Still struggled to get a decent star mask from the stretched luminance image. HDRMT did help reduce the dominance of the galaxy core but I still barely detected the nearby brightest star.

In the end I redid the whole thing (to get better colors, etc) and taking a bit more care. Everything was in the order that you suggested except I did MT just prior to stretching which was much easier with the star mask generation. Also I did arcsinhstretch for the RGB then a little bit of HT too to stretch a bit more - better contrast. It meant the RGB was more balanced with the HT stretched luminance Image. The end result seems to be better and stronger colors.

Incidently, I tried PCC and color calaibration and the latter was the one final chosen, the colors seemed better 'on this occasion'. Sometimes I get the opposite.

See attached final image, not perfect - still a bit noisy. The reason is that the mask I used for the galaxy when reducing noise was probably too wide - better if I'd just protected the inner spiral arms.



Hi Wim,

I think I did deconvolute before noise reduction (could be wrong). I also made a mask to protect the galaxy by using arcsinhstretch on a clone and stretching / black level until everything but the galaxy was clipped. This I believe may have also create weird contours.

Either way, I've had another attempt, definitely convolution done first. Also a mask created with a light extracted clone then range selection to just show the galaxy and made is blurred with the smooth slider.

Tthe attached result seems a lot better, no contours.

The only issue I still had was creating a star mask and doing MT to reduce star size. No matter what star mask settings I chose, I couldn't include the brightest star near the galaxy. So some of the stars are still a little bloated but at least not too over-processed now. Advice on star masks would be useful.



I've just been using a mask to protect a galaxy (M66) whilst using MLT for noise reduction. This was on both RGB al L images (still Linear).
The masks in each case were created by creating a clone then using range selection to only include the galaxy. I also made is blurred  it with the smoothness slider.
In both cases I still some subtle contours - see attached images, the RGB is still linear and the L is stretched but in both the contours are visible.

How can avoid these contour lines?



General / Re: Processing Question: Where did the color go?
« on: 2018 March 04 16:03:30 »
Thanks Cho


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