Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Topics - Bobinius

Pages: [1]
1
General / Masked stretch and big star appearance
« on: 2019 September 18 02:39:11 »
Hi everyone,

I am working on a narrowband project and the best stretching method for obtaining nebular detail and equilibrium (O3 is really faint) in this cas was Masked Stretch. However the bigger stars in the image have completely saturated circular white core with a net separation from the rest of the star (similar to the deconvolution artefact when the stars are not masked). Is this a known artefact of masked stretch on big stars and are there any setting for obtaining a more gradual tapering of the signal from the center of the star?

Thanx.

Bogdan

2
General / The problem of green in narrowband SHO palette
« on: 2019 August 03 01:24:43 »
Hi guys,

I was wondering what would be the correct and scientific way of dealing with green after combining the channels/masters in narrowband images using the SHO Hubble palette. Since we assign the Ha data to the green channel, when we use SCNR to decrease the green aren't we actually clipping Ha data? While this is normal when using an OSC camera with 2 green pixels for the Bayer matrix, it seems incorrect for narrowband.

The problem is that in order to obtain for example a correct blue colour that represents the Oyxgen, I am almost always obliged to decrease the green using SCNR. I generally try to use equal total exposition times for the 3 channels, but even after stretching the three channels in order to obtain equal median pixel values using Statistics, the green is still too strong and unbalanced. That is the case even when I have less total exposition for Ha! Or when I combine the images in Linear using linearfit. Astrophotographers using equal duration exposures still present the classical appearance of the nebula, with less green than 'normal'.

The question is, am I doing something wrong? I like Pixinsight especially for its scientific way of processing images, so I don't want to end up cosmetising things in order to obtain the result that I am looking for by clipping data and misrepresenting reality.

Thanx.

3
General / Dark frames are not correctly subtracted
« on: 2019 April 21 13:10:13 »
Hi everybody,

I am having this problem which seems to be reccurent during different sessions. I am using an Altair Hypercam 294C and Altair capture. After the integration using Batchpreprocessing, the image still has the sensor sideglow present and it seems that the dark frames did not subtract this signal completely.

Any idea what could be the cause? Pixinsight can correctly determine the duration of the darkframe (I capture fits). The glow goes away when I uncheck "optimize darks" but the image seems noisier (probably because the flats are no longer correctly calibrated).

Thanx

B

4
General / White circular patch on the stars
« on: 2019 March 12 09:22:05 »
Hello everyone,

I observed an artefact during post-processing which I believe it is due to an imperfect mask during deconvolution. The stars have in their center (visible on the big  ones) a solid white circular area which is homogenous and saturated white? Is it a known effect of some imperfect setting? How could I improve that ?

Thanx.

B

5
Hi everybody,

First post here. I have a problem with the background extraction process. After having applied the process, the new generated image is actually a cropped and larger version of the original one. I did  not modify the resolution during the settings and I tried with downsample at 1. Is there a default setting that reduces the size?

Second question: I have two series of subs with different exposures and ISO of M42. One has a gradient that is more pronounced a bit difficult to extract. Should I stack them in linear mode after having applied DBE for each and StarAlignment and then redo DBE on the final image or perform DBE on the stacked image before any treatment?

Thanx

B

Pages: [1]