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Topics - Ignacio

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Gallery / First image of 2018 - A classic if there is one
« on: 2018 January 22 14:20:42 »

This would be my first image of 2018 (hopefully of many to come). I had the privilege to spend three nights at a friend's observatory, located under very dark skies in Argentina. We enjoyed three consecutive clear nights, and was able to image one object per night (summer nights are very short!)

This image was acquired in the first night, after eluding a pretty strong summer storm by no more than 20 miles (with the full setup deployed!). After the southern celestial pole cleared of clouds, I polar-aligned, and enjoyed a very transparent night, although a bit windy.

I love how the image of this beautiful classic turned out. Its an LRGB (130:30:30:30) with a rather neutral (G2V) color calibration.

Usal setup: AP167FLZ + AP1100 + Apogee U16M + Astrodon 2nd Gen filters. Usual data reduction and processing with Pixinsight 1.85.

Here is a link to the full-res version, hope you like it.



Gallery / First NB images with renewed setup
« on: 2017 September 22 14:39:28 »
After much planning and a significant effort, I managed to renew all of my setup. Starting with my AP167 FLZ, which I have introduced to you already, I now added an AP1100 CP4 mount, and an Apogee U16M with deep cooling and a populated 7-filter wheel! This is no small feat for someone based in Argentina (anyway, not without breaking many banks!). I was able to take advantage of some level of mercy from the local customs, after being stationed in the USA for almost 2 years, which I took full advantage of.

A cooled monochrome CCD with NB filters allows me to start exploring the possibilities of NB imaging from my LPed backyard. These are my first two attempts: an SHO M16, and a bicolor Helix.

Hope you like them,

Gallery / First (proper) Light of 167 mm /f7.3 AP OTA
« on: 2017 March 27 14:37:15 »
After a long impasse of about 2 years, I am back in action with a new OTA, designed and built by Roland Christen of Astro-Physics. It is a 167mm aperture, oiled triplet, with a fluorite middle element, the blank of which came from Zeiss Jena's facility in East Germany and made it to the hands of Roland during the reunification. This is the same source of cristal used in the APQ series. Hence, I named the OTA AP167 FLZ in reference to this interesting back story.

I got delivery of it a few months ago, but only last Friday I had the chance to try it from a relatively dark site, close to Buenos Aires, hence the (proper) qualifier in this post subject title.

The object of choice was Leo's Triplet, which is kind of low from my location but still a great target to test the optics. Its is 2hrs 20 min integration with a cooled canon 6D. No need to say I am thrilled with this very fine instrument!


Gallery / IAPY 2016
« on: 2016 September 16 07:38:37 »
Happy to report that the Greenwich Royal Observatory has honored me with the 2nd prize in the galaxies category of this year IAPY competition. The image was the last I did before selling my OTA (AP130GT). I have taken  a "gap year" in astro-imaging, but will resume next year with a new, wonderful refractor that Roland Christen is finishing for me  :D :D :D

This is the awarded imagen which I have shared with you before:


Gallery / APOTY 2015
« on: 2015 September 20 09:54:32 »
I am happy to share with you that an Omega Centauri image of mine from last year has won the Stars and Nebulae category, in the 2015 Astronomy Photographer of the Year competition, organized by the Greenwich Royal Observatory.

This image was entirely processed in Pixinsight, and a key aspect of it was the use of the bayer drizzle algorithm to maximize star resolution and color.

As further examples of such approach to OSC processing, included bellow are two recent results, where I took advantage of the CFA2RGB module to have more control on each processing step.

Sagittarius Triplet:

SMC & 47 Tucanae:

Check out the hi-res versions to really appreciate the merits of the bayer drizzle approach. The achievable star resolution, separation and color, is remarkable. I can't emphasize enough the merits of this algorithm for those using OSC cameras.


Gallery / Batch of images acquired from dark skies
« on: 2015 February 19 06:59:41 »
Hey there,

Here is a set of 4 images acquired from a desertic valley in the Andes, same as my last Seagull Nebula posted here, with great transparency but poor seeing. All acquired with a modded canon 6D and an AP130GT in different configurations. You will find all the take details at the bottom of each image.

IC447 in Monoceros:

NGC2170 also in Monoceros:

Wide-field Pencil Nebula in Vela:

Sharpless 2-308 in Canis Major:


Wish List / Bayer drizzle independent of batchpreprocessing
« on: 2015 February 14 12:26:31 »
Juan, I would love to use bayer drizzle more often. But when I do, I miss all the flexibility and customization from doing the data reduction/registration step by step. Things like using different master calibration frames for different subsets of lights, or using subframe selector to generate weights, or tweaking image registration to accommodate lens distortion, etc.

Can a tool be devised, that would input the set of calibrated lights with the corresponding debayered registered subs and associated drz files (done independently), and output the set of calibrated, registered, bayered frames (with the drz associated with them) to then go directly into drizzle integration?


Gallery / Close-up view of Lovejoy from better skies
« on: 2015 February 02 16:04:32 »
This is the second image from my trip to a really dark site in Argentina. Taken with a FL of 860mm and processed to preserve the head structure without burning the core.


Gallery / Seagull Nebula from one of the better skies in Argentina
« on: 2015 January 27 07:44:22 »
Hi everyone! It has been a while!

For different reason I was kept away from astroimaging (weather, work, social events, etc.) for at least three months. To catch up, I took a one-week vacation at Barreal, Pampa del Leoncito, province of San Juan. This would be the equivalent of Paranal, Chile, where most of the professional observatories are placed. Maybe not as good, but still one of the better, if not the best, site in Argentina.

I was not very lucky weatherwise, though. Being a desertic area, I still got a couple of rainy days  :sad:, and too many cloudy/windy nights. Sessions are rather short too, during the summer, so all-in-all, I collected about 15 hours of data on 5 objects thru the week. Still very worth the trip (2-day drive form BA). I stayed at a beautiful posada (Posada Paso de los Patos), very well served with great food and wine, which contributed to some late session starts too. :)

I worked form the posada's backyard, right next to my room, which is at 1560 meter over sea level (compared to 2500 meters for the professional observatories in the area). Transparency was excellent, but seeing was kind of a disappointment. Maybe is a matter of altitude or time of the year (summers are unstable/windy).

Ok, so here is the first object, which I haven't done before: Seagull Nebula. It's a 3-hour integration with an AP130GT at f/5, and a canon 6D. I did my "standard" processing in PI, but may try bayer drizzle in the future. Hope you like it.

hi-res version:


General / Maximizing SNR in a stack
« on: 2014 October 03 09:46:24 »
This topic has always puzzled me. Although I think I understand the concept and theory behind it, its algorithmic implementations and results many times left me wondering what is going on exactly.

I am fairly aware of the difficulties in finding a robust metric for SNR, particularly on the signal side of that equation (ie, scale).  It is often the case, when I use SubframeSelector to look at a data set, or when watching the weights being calculated during ImageIntegration, that higher weighted subs don't generally coincide with what I would consider the better subs upon visual inspection (sharper, darker background, etc.) and other metrics (fwhm, star support, estimated noise, etc.).

We have discussed here before, the effects of significant and changing gradients on estimating signal strength that often skew scale estimates, and the way to handle this during processing. But many times, even with no apparent gradients, I also see unexpected results. Could it be subtle changes in transparency? of maybe bloated stars due to poor guiding/focus read as better signal? or a bug? I don't know.

Lately, I have been trying to combine two data sets of M33: one from a couple of years back and of lesser quality (shorter integration, worse fwhm due to seeing/focus/guiding, worse camera), with another from last new moon. I calibrated and stack both sessions independently, removed background gradients and color-calibrated both stacks. Then I registered one to the other with no problems.

To my eyes, the latter stack looks better than the old one (sharper, more detail, and better low-scale contrast), although from a distance they both look similar (after a STF stretch). But when I try to combine them (using ImageIntegration with SNR weighting), I see higher weights on the older stack (say, 1.35 vs 1), and I have tried many if not all of the scale estimator methods available in II.

Then I thought that maybe the fact that the old camera was 12-bit (canon 1000D) and the new one is 14-bit (canon 6D), was getting in the way. So I proceed to apply a LinearFit of one stack to the other, as a sort of rescaling. Then ImageIntegration went bananas, attributing a weight between 100 and 170 to the RGB channels of the worse stack!

By close inspection of the console output, I see noise estimations an order of magnitude smaller than what I get with the NoiseEvaluation script, but only in the older (ie, 1000D) stack.

One last note: since ImageItegration cannot work with only two images, I had to duplicate both entries in order for it to run. Hope this is not causing an unexpected problem.

I am uploading both stacks to the Endor server (under the folder "M33 SNR"), so that you can try to replicate the problem, and maybe help me understand what is going on. Be aware that each file is 119 MB.




Wish List / Bayer drizzle and BPP
« on: 2014 September 22 14:18:27 »
Would love to have tools/options to do bayer drizzle without going thru BPP, or alternatively, have the option of feeding fully calibrated subs to BPP.


Gallery / Galactic Center Mosaic
« on: 2014 July 01 12:25:44 »
Last Friday, I tried for the first time this combination: a full-frame canon 6D with an old SMC Takumar 75 mm f/4 lens (which had proven to be a great performer with APS-C size sensors). I targeted the galactic center, due to its perfect position in the sky this time of the year from my location.

The lens was stopped down to f/5.6, and 12x5-minute shots were taken on each pane. Although there is some distortion towards the corners of the frame, which in part I attribute to a tilted lens mount as one side is considerably worse than the other, the overall performance is very good.

The 3x1-pane mosaic registration and assembly proved to be quite a challenge, due to optical geometric distortion. I ended up using ImageSolver and MosaicByCoordinates. These are remarkable and powerful tools to deal with wide field mosaics. My appreciation to Andres Pozo for such impressive contributions!

I like the final result very much, and hope you do too.

low-res with data:



General / Bayer drizzle question
« on: 2014 June 13 11:45:57 »
Is there a way to isolate the steps out of batchpreprocessing, corresponding to bayer drizzle, so as to use it manually? It would be the part that takes the calibrated CFA monochrome subs, and transform them in bayered color images; and also the change of drz file headers, I guess.


Gallery / First try of DrizzleIntegration: Omega Cent
« on: 2014 June 02 19:35:06 »

Last Saturday I acquired a bit over one our of data of Omega Cent, taking advantage of its good elevation, and a fairly good seeing. Needless to say, I rushed to try the new DrizzleIntegration module, and with great success!

I processed 22 dithered frames, 3 minute each, taken with my canon 6D (ISO800) cooled to -5°C (sensor), and a FL of 865mm. The module handled beautifully a couple of satellite trails, and produced a very finely resolved image. BTW, with the native resolution of the canon (20MP), and 2x drizzle, I ended up post-processing a 1GB fits file!

Very happy with this result. Recommend viewing the high resolution version (14MP, 50% of drizzled output).

low res:

hi res:



This is my latest production, from last new moon, totalling 3:40 hours (1:40 Ha from previous month + 2:00 OSC). Color data comes from a canon 6D, while Ha data comes from a mono 450D. This is my second attempt (Carina was my first), in combining Ha with color data. I tried to be subtle, and not completely break the color  balance of the image.

It is such an interesting nebula complex in Scorpius, that it may deserve more integration time.  Nonetheless, I like how it turned out. Hope you like it too.


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