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Messages - gvanhau

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General / Re: StarAlignment and Flat/Dark/Bias Files
« on: 2016 November 28 07:31:17 »
You have to calibrate your light images prior to align them.

To do this, you have to intregrate your bias frames to generate a master bias.
Then you calibrate your darks and integrate them to generate a master dark.
Then you calibrate your flats and integrate them to generate a baster flat
Finally you calibrate your ligts using the previous masters.

An option is to use the Batch Processing Script where you can add the calibration frames to each seccion (bias, dark, flats and lights) and process them all together.


General / Re: Continuing problems with Mosaics.
« on: 2016 October 06 11:09:53 »
Hello Bob
A different aproach would be:
Generate a star field the size of your whole mosaic, then register all the tiles to if.
finally use gradient merge mosaic to combine the registerd tiles.


Hello Diane
I would not use teleconverters in astro imaging, unless you have a good method to support the camera and the tele lens; the weight of the camera and/or the tele lens introduces flexure that will cause distortions in the image.
Yet, with the 600mm tele lens you already have a good "telescope".

for adapters you only have to search the internet, but it is wise to buy the camera first, to see what kind of interface you need. There are some CCD brands that provide their own adapters to lenses (for example, moravian, QSI, sbig, etc).

Edited: when choosing a CCD camera, you have to take in mind the distance from the lens to the sensor (ie filter wheel and whatever other equipment you put between the lens and the CCD camera, they mut still allow the lens get focus) in Canon lenses this distance is about 55mm.

Good luck.

General / Re: Help With Noise Estimation
« on: 2016 August 22 06:33:03 »
This pattern seems to me a little drift between images.  if so, Mono CCD's will show the same streaks, and the best method to avoid it is dithering.

In order to remove the noise, you could try the FFT transform, remove the dominant pattern and then inverse FFT transform (simmilar to processing comet images).


General / Re: FLATS !
« on: 2016 July 26 19:09:25 »

Here is the link to the proyect (zipped file)

The whole proyect uses drive F to read an store files.
On screen, from left to right:
I integrated dark files, Then integrated FlatDark files
Then I calibrated flats only using master FlatDark (bias is already included in master FlatDark).
Then I Integrated calibrated flats, giving a normal masterflat.

The next step is my proposal:
Y use splitCFA to split a single light, The master Dark and The master Flat
Then with pixelMath I generate a semi calibrated light for each of the CFA0...CFA3
(note the cfa images ar written in separate folders into the f drive)
the resulting images are then used to linear fit each of the CFA images of the Master Flat.
Finally the resulting CFA_Flats  are recombined into one image using merge CFA.
This resulting master flat  is then used to calibrate the lights.

Note: calibration of lights is done only using MAsterDark and the master flat from previous steps.
No bias is necesary because it is already included into the masterDark.

note: Batch debayer is a placeholder for the batch debayer script.

Hope this litle explanation hepls.


General / Re: FLATS !
« on: 2016 July 22 17:22:53 »
Hello Paul

I did a test on your images, using my workflow.
If you are interested, I can share the proyect

On the left image I integrated calibrated ligths with normal master flat. On the Right is the image integrated using the Adapted master Flat.


General / Re: FLATS !
« on: 2016 July 21 07:23:11 »
Hello Paul

The zero secconds bias frames will not work with long exposures, because the readount mode is different.
If you take flats over 4 secconds you have to take flatDarks.
Note that more than 4 secconds flats have amp-glow  and bias of zero seconds do not have amp glow.

I this case, you have to integrate the set of flatDarks (without calibration) and then calibrate the flats only using the resulting master flatDark.


General / Re: FLATS !
« on: 2016 July 20 13:49:04 »

I think that you can't use BPP with QHY8L, because it acts different when taking short exposures than when taking long ones.  (On short exposures it takes 2 images for each half of the image, on long exposures (>4s) it takes only one image, wich has some amp glow that builds up during readout of the second half of the image.

In my experience, what I do is the following:
I take the flats with very short exposures, and calibrate them only with bias frames.

I then do a linear fit of the master flat using this procedure:

Finally I calibrate the lights only with darks and the master flat obtainded from the above procedure.

This workflow works almost all the time for me.


General / Re: Hardware vs software binning
« on: 2016 May 04 11:17:10 »
I'm no an expert on this, but as far as I know, there are two advantages in using HW binning vs Softw.

The first is that in Hw binning you only have once the readout noise, in softw binning you have the readout noise from each pixel you sum up.
The second advantage that you may have, is that fractions of ADU that are lost in soft binnin may be counted up by HW binning.


General / Re: Bad flats, trying to recover
« on: 2016 April 27 12:29:12 »
Geert - what I posted was a calibrated image, attached to this message is an uncalibrated one.  You see that there is a dark large spot to the upper right of M106, it's just that this spot isn't quite aligned with the flat.  My only explanation is that the dust mote shifted.  The scope used is a refractor in my backyard, equipment and conditions which have never caused me reflections in the past.
Ok, I understand now.
Not related, but I see a gradient from left to right that is not in the calibrated image, dit you apply any other process to it?


General / Re: Bad flats, trying to recover
« on: 2016 April 26 12:29:55 »

The circular band (if we are talking about the same brighter band to the right of the galaxy) seems more a reflection than a dust mote (dust motes are usually darker than the background). It is very unlikely thay a normal flat will correct this. May be a synthetic flat as Rob proposes will do.



This old post may help you.


No bug here, just normal behavior. However, everything is guess work without the image in question.
Sorry Juan I Did'nt see your reply. By this time I already found a work arround (using the masked stretch script).
It may be usefull to include the minimum level where this procedure can be applied in a tooltip.


Bug Reports / Re: Star Alignment
« on: 2016 March 31 08:15:24 »
I once got this, and it was that Hot pixels where detected as stars.
Try changing the detection parameters or to remove hot pixels before aligning.


General / Re: Quick and dirty BPP in the field
« on: 2016 March 15 07:53:38 »
There are several catalogs you can download for  free. (GSC1.1, UCAC4, etc).
The image solver script doc is here:
See  charpter 2.3 how to use a local catalog.


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