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Messages - pfile

Pages: [1] 2 3 ... 248
1
General / Re: preview box with a Mac
« on: Today at 17:05 »
i think this is a longstanding problem that juan could not reproduce since his keyboards don't exhibit the problem.

i am a mac user and have only ever used PI on OSX, and all this time i've just been pressing the "new preview" button in the toolbar.

if the STF on/off or mask/on off keyboard shortcuts didn't work i'd be mad, but at least for me hitting the button is fine.

rob

2
New Scripts and Modules / Re: Subframe Selector PCL Module
« on: 2018 September 21 07:22:57 »
i can try to build it for OSX but i think i'm maybe behind a couple of revs on Xcode and don't have the latest PCL installed so it may take me a couple of days.

rob

well so i made the mistake of pulling the latest PCL from the pixinsight github, and i found that after i built the module that 01.08.05.1352 (which is the latest for OSX) complains that the API version is unknown (161) vs an expected of 160.

i guess i can rebuild PCL from your fork of the PCL tree which i assume is going to have api version 160... but something is funny here. either OSX core is a release behind the PCL release, or the PCL API version has been bumped without a corresponding release of the core application on every platform... (?)

i also have an older build of PCL that i used to build the last SFS so maybe i can just point to that instead.

rob

3
General / Re: Guide or Tutorial for how to evaluate subs?
« on: 2018 September 21 06:54:41 »
well i guess the FWHM is going to be a function of your seeing and the aperture of the telescope (and what filter you are using). i suppose the only way to know what is a good FHWM and what is not a good FHWM for you is to compare a whole bunch of subs taken thru the same filter on a variety of nights. the only problem with this empirical method is that it may be impossible to reach the theoretical capability of your system if your seeing is consistently poor. but in some sense it doesn't matter - you have to work with the sky you have.

here's a thread from some variable star observer guys which is pretty interesting:

https://www.aavso.org/fwhm-expectations-larger-aperture-instruments

adam of course has a point - i know that rick has mentioned just throwing everything he has at one integration to try to boost the SNR of the background and faint areas, and then more carefully culling for an integration of the target itself. of course that then leaves you with the problem of trying to merge the data, but i guess the point is sometimes it might make sense to integrate a bunch of 'crap' data.

rob


4
New Scripts and Modules / Re: Subframe Selector PCL Module
« on: 2018 September 21 04:42:17 »
i can try to build it for OSX but i think i'm maybe behind a couple of revs on Xcode and don't have the latest PCL installed so it may take me a couple of days.

rob

5
General / Re: Guide or Tutorial for how to evaluate subs?
« on: 2018 September 21 04:39:44 »
well... if you look at some of the stuff david ault has put out there regarding SFS approval expressions, or maybe jon rista, i guess it's all kind of mom and apple pie stuff that we can all agree on - good subs have low eccentricity, high star counts, low FWHM, etc.

have you dissected one of those expressions?

rob

6
General / Re: Flat frame artefacts showing in final integrated image
« on: 2018 September 21 04:37:17 »
i hope they get it sorted... my feeling is they have a lot of nice stuff in some really dark/great locations, but it all only kind of works.

rob

7
General / Re: Vertical band in image
« on: 2018 September 18 21:08:51 »
sometimes you can't see subtle problems in a subexposure due to the noise...

rob

8
General / Re: Pixel Math question
« on: 2018 September 18 21:08:06 »
well i suppose so... generally PM will show you something like this in the console when something is wrong with an expression:

Code: [Select]
*** Error: Mismatched right parenthesis:
$T*0.6+Image140_clone)
.....................^
<* failed *>

for simple errors like that one, it's pretty obvious what's going on. but when you have a complex expression that has an error, sometimes the error the parser spits out first is not necessarily an error, but is the result of some other error in the expression. some editors have special modes for different programming languages which will highlight in real time which braces/brackets match with one another so it's a bit easier to see where your syntax error is. if you go into the pixelmath expression editor you'll see for instance that when you close a parenthesis, the corresponding opening parenthesis is highlighted. if you have a bad expression with parenthesis in them, it might help to add and delete close parens to your expression and watch the highlighting to try to figure out what's wrong.

rob

9
General / Re: Pixel Math question
« on: 2018 September 18 19:32:28 »
pixelmath does not really require any knowledge of any specific programming language, and whatever it has in common with actual programming languages is just sort of the general syntax of different math operations, variable assignments and function calls.

there are tutorials available around the web... here are some videos that oldwexi made:

http://www.werbeagentur.org/oldwexi/PixInsight/PixInsight.html

https://pixinsight.com/forum/index.php?topic=11829.0

https://jonrista.com/the-astrophotographers-guide/pixinsights/narrow-band-combinations-with-pixelmath-hoo/

http://www.deepskycolors.com/PixInsight/PixelMath.html

rob



10
General / Re: Flat frame artefacts showing in final integrated image
« on: 2018 September 18 18:21:40 »
2nd time in a week ive seen lousy data from itelescope, and the 3rd or 4th overall. id ask for my money back and also ask them to fix their camera.

i agree with adam that this seems like frost.

also if im not mistaken, they provide calibration masters produced with maxim, which can be a real pain to make work in a different processing program due to 32b fits incompatibilities.

rob



11
General / Re: Ideal Steps for DSLR Frame-Flickering Issues
« on: 2018 September 17 19:45:58 »
OK - since the flats are doing funny things i just wanted to confirm that they had at least been bias subtracted.

you are right that there's negligible dark signal in the flats, so it's probably OK to skip the darks.

1/400 is pretty short for flats and i'd second dld's advice about trying to get the shutter open longer. on my STT-8300M i never do flats shorter than 1s, even though it has an "even illumination" shutter.

this video is of a canon DSLR, and the longest exposure they did was 1/500s, but you can see that at 1/500 the 2nd curtain is chasing the first, so it's at the point where the shutter stops opening and closing completely and starts becoming a "moving slit"...

https://youtu.be/CmjeCchGRQo?t=2m12s

for a sky flat short exposures might be OK but with a panel, there's going to be some amount of flickering and you want to make sure the shutter is open long enough to average out several cycles of flicker.

rob



12
i think the blue-green cast is inevitable as the filter cuts a lot of red wavelengths. i used to use one of these filters (when i used a DSLR) and concluded they cut out too much light to get proper images of broad-spectrum objects like galaxies. the CLS filter works great on emission nebulae though - in the end it's bandpass is something like the combination of a very wide Ha filter and a very wide OIII filter.

so i wonder if it's even possible to color balance a CLS image because of all the missing light.

one thing i used to do to make sure that my flats were well exposed in all 3 channels was to do t-shirt flats with a pinkish T-shirt. it's not really important to make your flats grey, but because of the blue/green channels saturating so fast, the red channel can be weak and thus have lower SNR.

i've heard that the IDAS filter is a little more forgiving on galaxies.

at any rate your m31 looks good.

rob



13
right - full DSLR mods involve removing the IR filter completely, so you need an IR cut filter somewhere (which doesn't block Ha)... not sure how sensitive DSLR sensors are to UV but obviously some sensors are since people use UV cut filters to try to prevent 'blue bloat'.

rob

14
General / Re: Ideal Steps for DSLR Frame-Flickering Issues
« on: 2018 September 17 18:36:23 »
you have to use darks, or bias on the flats or else they will not correct the lights properly. understood that the sony sensors have very minimal dark signal but they still have bias/offset that needs to be removed...

rob

15
i think by that sentence juan meant IR and UV *pass* filters - CLS-CCD has an IR cut component... not sure about UV though.

rob

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