iOptron iEQ30Pro review – PART#1 – initial impression

This little mount caught my attention right away from its first appearance on the market some year (or two) ago. I simply love small but powerful astro-toys. But that time I was still using my old HEQ-5 SynScan from Sky-Watcher for occasional airline travel to dark (and mainly clear sky) locations to do some astrophotography. Also, I wanted to wait for first users’ experience – what a contrast to today when I am the first owner of this mount in Europe. Simply put, the mount has been there for a while and this „Pro“ version is the second generation so hopefully it would be mature now. I’ve been waiting for it for over 6 months.

The mount arrived in two, rather small boxes (weighting 8 and 12kg). The first one contained the iEQ30Pro’s head (6.9kg) and counterweight shaft (666g) while the second one contained the tripod, one counterweight (4.5kg), cables and standard accessories (RS-232 cable, handbox cable, DEC drive cable, power cable (12V), power cable (110/220V), polar scope illuminator cable, extension shaft and a printed copy of quick start guide). Full user’s manual is available from iOptron’s website as well as ASCOM drivers and firmware updates. Because I must always have something non-standard, my delivery was missing the Hand Controller (Go2Nova 8407+) and Tripod Support which was delivered to me in a separate package later, right after I claimed these missing parts.

First impression. The mount head is really small and lightweight and therefore easily portable. The color is not exactly white as I expected from pictures, but rather light-grey, the counterweight is black. Surprising was that the mount head is not fixed on the tripod’s top by the center screw as that doesn’t have any threads – it has smooth surface, just like the alignment peg. The mount is attached and secured via two AZ locking screws on side of the bottom plate of the mount. The bubble level indicator on the mount head is harder to use due to not enough (comfortable) clearance below the polar scope. The latitude adjustment knob is somehow difficult to use too due to limited clearance around the knob (but it’s not a big deal as the minor adjustments are fine and easy, just major adjustments are a harder task).

Connecting the cables is easy and straightforward though I advice to really carefully read the instructions manual (at least the short quick start). It’s very nice to have again a mount that only requires power supply cable, handbox cable, DEC drive cable and optionally (in my case mandatory as I never ever used ST-4 guide port at all) the RS-232 cable to connect the mount to the computer over ASCOM platform. When I first time powered on the mount and press RA/DEC buttons to play with it, to slew in both axis, I was very well surprised of a nice sound from the motors. It’s also very silent and looks very smooth and precise. Compared to my previous HEQ-5 (not taking into account that I owned a Losmandy and currently own a Gemini 53 friction mount as my main mount) the fit and finish and “manufacturing quality” looks very well.

As I was lazy (and too busy at work) to read carefully full user’s manual, it took me a little time to figure out why the mount, after powering on, doesn’t track even though the controller says SDRL which stands for sidereal rate of tracking. The trick is to press button 0 (zero) to toggle between Tracking and Stop (initial) mode. The keys 1-9 change the slewing speed (64x after powering on). Menu, Enter and Back buttons are self explanatory and I must admit it’s really easy to learn how to operate it and navigate through the menus. Really nice. Additional nice feature is the light-bulb button (symbol of a Sun) which turns on red flashlight on the back of the Hand Controller. This deserves a praise to iOptron (on the other side, the reticule (polar scope) illuminator power will be prone to water-damage from condensing dew as it’s located on upper surface next to power on button which is definitively not a good design).

First thing that I advice a new owner to do is to make a firmware upgrade. This is really well documented on iOptron’s website in the support section. Interestingly there are 4 various firmware (.bin) files needed (apart from the FW upgrade utility) which is rather uncommon. I managed to upgrade successfully without any problem. The reason to do so is that this procedure of upgrading FW changed my previously set time zone and therefore affected my local time. Thus, do a FW upgrade first, then set your time zone. The rest is set automatically by the integrated GPS feature which is very handy and one of the reasons why I purchased this mount. The GPS status is ‘ON’ after powering the mount on, but in few minutes it changes to ‘OK’ to indicate successful GPS time and location update. Obviously it works in the field, not in-house. Another reason, why I had to upgrade the firmware was that I was unable to connect from PC to the mount over RS-232 cable (COM port). The driver was claiming old FW.

TO BE CONTINUED…

References

iOptron iEQ30Pro review – PART#2 – first night out

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CCD Cameras – Calibration Process

I would like to share this appendix chapter to my talk (All you need to know about CCD cameras) given at CEDIC 2015 here as I believe it might be useful for many beginning CCD astrophotographers. The 40 minute slot of my lecture was obviously too short to tell the „full story“ as I like to give all the details and relations among them in this very complex topics. Let’s go to the story now :)

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QSI vs. ATIK Sony ICX master bias example

This is just a quick and actual/current (19th November 2014) comparison of a master bias from a QSI 660 mono camera versus Atik 460 EXM camera. Both cameras feature famous/great Sony ICX694 CCD detector known for its low noise and high QE being most suitable for narrow band imaging. This is not a random/single example of a „defect“, more samples from more cameras were showing exactly the same issue of amplifier glow [OK, it might not be exactly amplifier glow issue, but it is very similar issue - noise is added by thermal heating of some electronical components/parts located on the circuit board close to the sensor and therefore the longer dark frame the user takes the bigger visual appearance of the "defect" shows]. For more information on AmpGlow issue please check THIS article.

Let’s look at the images, stretched in PixInsight (my new software tool for viewing FITs files under Linux). All images are taken at -10 degrees Celsius in bin 1×1 mode and were 10 minutes long.

QSI660mono-masterdark

QSI660 masterdark

Atik460exm-masterdark

Atik460EXM masterdark

Atik460exm-masterdarksubtractedmasterbias

Atik460EXM masterdark with masterbias subtracted

The world of CCD manufacturers and their current offerings on the market changes/evolves as well as bugs are being fixed and new ones are introduced. Therefore any statement of who makes better cameras must be done at some fixed point in the timeline.

Currently, if you are about to purchase a Sony ICX based camera, the best is to go with Atik even though Atik has readout noise around 5e- [we are talking about ICX-694 cameras, the ICX-814 are by 1 to 1.5e- "better", but what you gain here you loose in the final SNR due to smaller pixel size of ICX-814] while QSI reached a readout noise around 4e- only. BTW FLI shall now make a very nice MLx694 camera with even lower readout noise then QSI, but I cannot confirm that at the moment and could not afford/justify to pay more than twice as much money for a 1e- lower RN camera being an european customer.

On the other side, if you wonder what’s better choice whether Atik 383L+ or QSI 683 when it comes to most popular KAF-8300 detector, then the QSI is currently better choice (after last 3-4 years QSI finally makes a great 8300 cameras) if we compare these two makers only (because currently best Kodak/TSI based cameras are produced by Moravian Instruments, from my perspective).

Talking about makers, all of them had issues in the past with some of their camera production lines. There is no general-truth and black-white vision. I will put AmpGlow test [thermal noise accumulation test] on the list of performance tests that I do with every CCD camera that comes into my hands :) I shall do it with my newly acquired Atik ONE, but as I was told, the electronics is the same as in Atik 4xx line so I do not expect any problem (but will test it anyway!).

Update

atik1

Atik ONE 6 masterdark


Yes, the Atik ONE behaves exactly the same way as Atik 4xx and that’s fine :)

Another update (11th December 2014)
After reading QSI letter to customers I decided to spend last few minutes more on this topic. They are probably right about the issue name, it should not be called amp glow, it shall be called glow or simply other way [from my perspective, the problem exists no matter how you call it but also the solution exists]. They are right that proper dark frame calibration (same binning, same cooling temperature, same subexposition duration matching light frames) takes care of it. They are right about their focus on low readout noise cameras (which is fine, I am the same type of guy, chasing ghosts). They are right that they had to make some decisions on the design (every maker had to do it, someone better someone worse) and they are right that the master dark frame calibration works.

What I do not like in the article apart of the fact that it is tendentious (to hide their amateur design)? The table data and chart. It is misleading and done on purpose to demonstrate something that only confuses normal, ordinary users who have no chance to understand it. There is no reference light frame used for calibration test? From where did they get the numbers and how? It is explained in the last paragraph and whoa they calibrate a single dark with a master, funny. The result is obvious and same with every correctly working camera on the market – that stacking multiple subs lowers noise is obvious. Just visually guessing the table and chart looks OK on first look because the longer subexposition the higher accumulated thermal noise (their „defect“) and therefore the higher demand/need to subtract it and obviously then „better“ ratio of correction. They simply correct for something they introduce into the image! But it is „foolproof“.

They are also not right about „subtracting a bias and a zero second dark results in an increase in image noise by 0.71, as expected…“. There are at least 3 errors. First, you either subtract bias or you subtract a dark, but I guess it’s just a wording issue as they speak about zero second dark – an equivalent of bias so they should only have put the latter into parenthesis. If you correct for both bias and zero second dark then you obviously do it a wrong way and „noise“ (without adjective) would be increased. If you say you increase noise by 0.71 you say that the final noise is lower! An increase is with multiplication and therefore with a floating point number higher then 1. OK, this was just a side note on the text quality. I think it makes no sense to comment more (last paragraph tells the reader that stacking multiple frames (whatever it is, light frame, dark frame) lowers the final noise in the frame, but that is obvious, every CCD beginner knows this rule).

AN EXPERIMENT
To not talk „bullshit“ I made a very quick experiment with a single Light Frame of my recently taken Sh2-249 and IC443 Jellyfish Nebula image. The single Light Frame has StdDev of 467.641 ADU . Now we have two options to calibrate the image:
(A) with a Dark Frame. Here you end with resulting StdDev of 462.678 ADU (5 ADU levels difference from uncalibrated image).
(B) with a Bias Frame. Here you end with resulting StdDev of 467.645 ADU, but do not forget to get rid of the hotpixels by using a hot pixel map removal, after BPM and after this common calibration process for every Sony ICX based camera [calibrating with master bias and using bad pixel mapping] you end with resulting StdDev of 462.608 ADU.

Can you see the difference? :)

Conclusion
In my personal opinion, it is a big shame and bad advertisement for QSI. But the dark frame calibration would work just fine, it is just an ugly tradeoff having to calibrate with darks where other brand cameras with the same chip doesn’t suffer from this „defect“ and can be calibrated with usual, common way of using master bias and hot pixel mapping only as it makes life much, much easier. On the other hand, QSI cameras really have about 1e- lower readout noise (it all depends on chip as chip variance is 1 to 1.5e- from my extensive testing experience) then say Atik, my favorite brand [just got another Atik recently and a price tag and ease of use was my decision point].

Another update (3rd May 2015)
From now on, QSI fixed the issue.

Rubriky: Articles in ENGLISH, Pokusy, Technika, recenze | 1 komentář

Atik ONE 6 review – PART#1 – unboxing, initial tests

29th August 2014 and 17th September 2014 two important dates in my CCD camera life. The former is when I sold my beloved Atik460EXM and the later is when I pulled the trigger and ordered Atik ONE 6. I simply cannot imagine a life without SONY ICX-694 even though I moved from a keen narrow band (Ha/OIII/SII) astrophotographer into a keen broad band one (LRGB) using a big full frame size chip. I would very much miss the opportunity to combine a nice HST images. My motivation was to have some kind of integrated filter wheel in place and possibility to add some OAG and therefore I purchased the Kit version which comes with a replaceable OAG and Atik GP guidecam.

Let’s check what you find in the box, OK two boxes:

1-Box1Of2-Camera

Box 1 of 2 - Main Camera Body in standard Atik box

2-Box2Of2-OAG

Box 2 of 2 - OAG with focusable guideport and AtikGP

In the first box you find the main camera body, 3m long USB cable, little shorter – 1.8m only power cable (with 12V socket), CD, manual, quick start guide and filter replacement tool. In the second box you find the OAG with mounted (could be unmounted) 2″ nosepiece and focusable guideport (for T-thread equipped guidecam) along with the small Atik GP guidecam body and short mini USB cable to be used to connect the guidecam with the main Atik ONE camera which possess a USB hub and some three hex tools (keys) and three replaceable screws (long ones) to mount the OAG on the camera body. The camera body comes with standard T-thread adapter which can (and must) be unmounted (three short screws) in order to (i) insert filters inside the internal filter wheel and (ii) to mount the OAG on the camera body. But, obviously, you can choose wheter to install the OAG or not, I still haven’t mounted mine and will do a first light without it as if I purchased Atik ONE 6 in the non-Kit version.

Since I haven’t used the OAG yet I give a brief comment only. It looks well built. The focusing seems just fine with the big focus ring, smooth and solid enough just as it is. The focus lock knob is kinda small and therefore ineffective as you can easily overcome it with just little force applied on the big focus ring, that’s simple physics. But anyway, the smooth focus (supposed travel 5mm) is NON-ROTATING which is great and as I said, seems solid enough. One downside, if I could afford to tell without actually using the device, is that the „sight-hole“ for the OAG camera is small (although the prism mirror is reasonably sized and could be put deeper or shallower inside of the OAG)! It is only 6mm in diameter which is suitable for only 1/4″ sized chip guide cameras! For my new G1-301 with 1/2″ chip and 656 of 9um pixels it won’t be usable without severe vignetting (knowing that prior purchase I got the non-Kit version and save $$$ for other OAG). Therefore I will probably use it with QHY5L-IIm (alccd5L-IIm) which I decided to keep for this other imaging setup or as a spare guide cam. From the backfocus-point of view, the Atik GP has 7mm of backfocus while QHY5L-II has plenty of variability based on which adapter you use – in the worst case I will have a custom adapter built.

What to say about the main Atik ONE camera?

3-AtikONE-body

Atik ONE 6 Camera Body

Apart from it’s brother platform-4 family of Atik cameras (round body) it possess an integrated filter wheel which makes the square body of the camera bigger – 12 x 12 x 6 cm WxHxT. It has two standard 1/4″ tripod attachments (deep enough roughly 6-7mm), but unexpectedly on the side of the body. It has bigger (finally a good improvement for a field use / non-permanent setups) USB-B port and integrated USB hub. The downside is, it looks so, that the USB hub is somehow limited and supports only Atik GP camera. I tried to attach a MII G1-301 or QHY5L, but did not succeed. Maybe it is me (high probability as my stupidity doesn’t have a fixed boundaries), maybe it is the same (not-smart) decision from Atik like with their proprietary Dawn post processing software that was able to open only FITS frames from an Atik camera (not sure if this limit is still valid in the actual version of the SW). My personal opinion is that it is a silly decision.

4-AtikONE-dimm

Atik ONE dimensions and weight

Everything is a compromise. An ideal CCD camera would come with a 8 pos (at least, 7 isn’t enough – at least for me) filter wheel, but you can’t have it in a compact form. I like small and compact but extremely powerful cameras. Since shooting LRGB with a tiny pixel (4.54um which on the other hand yields nice resolution and detail) is „wasting of time“ for me and since the ICX 694 „sings“ in narrow band imaging due to the very low readout noise (and overall noise) of the chip (and camera) as well as with high QE in the desired wavelength (extraordinary OIII, very high Ha and SII) I am quite happy with 5 positions in the integrated filter wheel which keeps the camera compact (weighing 911 grams without filters, with T-thread adapter).

5-NewStuff

Astrodon Filters 3nm Ha, OIII, SII, infrared (Sloan z') and Baader UV/IR L

6-ComparedToG1andG3

Atik ONE 6 camera size compared to Moravian G1 and G3 cameras

Quick initial tests of a new camera
Installation of the drivers, plugging camera in and finding correct driver, shooting biases, testing cooling, checking out readout noise, testing filter wheel etc.

Installation of the drivers was smooth and OK as long as you had ASCOM 6 (or 6.1) installed. I did not have so I had to reinstall my ASCOM platform 5.5 along with all other drivers. The main driver works fine for Atik software, but for everything else ASCOM is the way to go. It is interesting that the main camera body must be selected as „Atik 2″ while the guidecam must be choosed as „Atik“. Would be wiser to choose better naming convention I guess. Anyway the cameras work.

One of the initial tests comprises of a TEC cooling test:

7-AtikONE-coolingtest

Cooling Test - Max TEC delta 38 degrees C in about 4 minutes

From ambient temperature of 22.4 degrees Celsius I got to my set-point temperature (-15) in about 4 minutes using 95-96% of TEC power. This shows the maximum delta to be around 38 degrees Celsius which is perfect even for hot weather countries. I forgot to measure the current draw though (but let’s assume the spec will be correct as it is with everything else I tested in order to confirm the facts).

Next quick test is download speed. For 1×1 binning I got the image downloaded in about 8 seconds. This seems little strange to me. I can recall that my former Atik 460EXM was downloading faster, I believe in some 4-5 seconds (not 100% sure at the moment as I can’t verify it now having my 460 sold). In bin 2×2 mode I got the image downloaded in roughly 3 seconds. Anyway, I never plan to bin unless I start to shoot small planetary nebulae with 2+ meter of focal length.

8-AtikONE-typicalsinglebias

Atik ONE 6 Typical Single Bias Frame

Another quick test is the readout noise test that I base on my Octave (Matlab) script I use for camera noise comparisons.

Here are the results from Atik ONE 6:
CCD Camera Measurement:
-----------------------
Gain = 0.26
Readout Noise = 4.71e-
Total System Noise = 5.06e-

and here are the results from Atik GP:

CCD Camera Measurement:
-----------------------
Gain = 0.08
Readout Noise = 5.78e-
Total System Noise = 6.17e-

The filter wheel looks fine, it produces some „click“ sounds when positioning the filters and according to images of the wheel (disc) internals it looks very well built. For mounting or replacing filters in the wheel you have to (the easiest way) unmount the camera adapter which is kinda inconvenient, but I won’t replace them frequently.

So far so good :) For a real first light test we’d have to wait until I get my other (2nd) setup up and working, now I am finishing some LRGB shots done with ASA and G3-11000 which has top priority.

References
http://atik-cameras.com/

Rubriky: Articles in ENGLISH, Technika, recenze | 5 komentáře

Miscellaneous Equipment Images 2013/2014

As an enthusiast in astrophotography I like to document various equipment that I had in my hands. In this brief post I would like to share with you couple of such images.

1-newASA10inchgeartestinandout

2013 - New ASA 10 inch Newtonian setup in the field vs. getting ready in-door

2-CollimationTable

Custom made collimation table

3-ASAmountingWynneOAGcams

Mounting ASA Wynne 3 inch with OAG for G3-11000 and Atik CCD

4-HowieGlatterTuBlug

Howie Glatter TuBlug laser game - Actually I prefer using CatsEyeCollimation!

5-newMIIG1guiders

New G1 guiders from Moravian Instruments, G1-1200, G1-300 and the overall winner is G1-301

6-newMIIG3cameras

With a G3-series CCD from MII you simply can't go wrong (for LRGB imaging)!

7-Atik460SXFWAstrodons

Atik + SXFW + Astrodons, my setup before I got Atik ONE 6 with integrated FW

8-Atik460testingbeforesellingit

Testing Atik 460EXM before selling it to check that everything is OK

9-newELpanelAspike

New 16 inch Spike-A Flat Fielder

A-AAAtikOOOne

The more Atik cameras the better.

B-AtikGPoag

Quick test of Atik GP camera

:)

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Sightron nano.tracker quick test

nanotrackerAs a 100% mobile astrophotographer I like to test and review portable mounts and portable tracking units (I owned AstroTrac TT320X in the past). Since my ultra-mobile setup (for catching all sky timelapse videos and possibly meteor showers) weights only about 135 gramms including lens (!) I decided to give a Sightron’s nanotracker unit a try. Another reason was that unlike from AstroTrac it doesn’t have a 2 hour tracking limit. Since the purchase on 6th December 2013 I have used the unit 3 times, once on 13th December 2013, once on 8th August 2014 and for last time on 28th August 2014.

Here’s what you find in the box:

nanotracker-box

Sightron nano.tracker tracking unit package

First quick test took place on 13th December 2013 (Friday) using Canon EOS 600D with 50mm Zeiss lens. The tracking unit was VERY ROUGHLY polar aligned (just guessing).

060secTEST-50mmLENS-APSC

50mm LENS, center crop, very rough PA, 60 seconds

Second test took place on 28th August 2014 using Canon EOS 600D with 17mm Tamron lens. The tracking unit was, this time, better polar aligned through the „sight hole“ only.

360secTEST-17mmLENS-APSC

17mm LENS, center crop, sight-hole PA, 6 minutes

In the meantime, on 8th August 2014 I have used it for some all-sky timelapse testing:

session-2014-08-08

Sightron nano.tracker IN ACTION

As I prefer not to worry about running out of power during a night I have improved the hand controller by adding an ordinary „jack“ connector instead of using 3×1.5V batteries (that possibility was preserved).

nanotracker-power

power input from a DC to DC step down converter

For an easier polar alignment I have let a friend of mine to build me a custom made holder for the nanotracker unit. It looks exactly like depicted on following image. The idea is to use it along with stronghold tangential assembly from Baader that serves like an ALT/AZ wedge.

nanotracker-holder

custom made holder for nanotracker placed between the wedge and nanotracker body

Summary

  • nice, small, compact and reasonably precise tracker
  • not for higher payload, the Canon 600D with a simple lens weighing over 1 kg (without ball head) is quite a lot!

References
http://www.sightron.co.jp/

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ALccd5L-IIm / QHY5L-II mono

Well, I said, that I will not buy any QHY camera any more. But I could not resist. I was so much interested in the performance of the new Aptina MT9M034 CMOS chip that is said to have high QE and that could be also found in other „planetary“ CCDs (CMOSes) cameras like ASI/ZWO, but QHY (or astrolumina) offers something like „Premium Package“ or „Deluxe Kit/Package“ which includes some wide field lenses (with supposingly 180 degree view) and C-mount/Cs-mount adapter and tripod camera body holder etc. Since I said I won’t go with QHY any more I got the same thing rebranded as ALccd from astrolumina.

alccd5l-iim-1

ALccd5L-IIm / QHY5L-II mono Premium Package

alccd5l-iim-2

ALccd5L-IIm / QHY5L-II mono Premium Package

I always wanted to capture the whole sky at once as it is so beautiful when you are in the country-side enjoying the silence at some quiet place with completely clear sky and freezing temperatures :)

alccd5l-iim-3

AllSky Setup with ALccd5L-IIm

alccd5l-iim-4

AllSky Lens with ALccd5L-IIm

First Light Test (with hotpixels included) from 2nd October 2013

30secQHY5L

30sec sub from my home-place

Master Dark Frame

mdark_30sec

30sec Master Dark Frame

Camera Test Report

At some unknown temperature with default settings (gain 12 and 12bit ADC).

CCD Camera Measurement:
-----------------------
Gain = 0.05
Readout Noise = 4.79e-
Total System Noise = 7.17e-

My Results

All Sky Timelapse Movie ALccd5L-IIm 1.25mm F/? lens:
All Sky Timelapse Movie ALccd5L-IIm 1.25mm F/? lens

Tenerife Nightsky Timelapse (February 2014):
Tenerife Nightsky Timelapse (February 2014)

My Friend’s Results

Since I am lazy enough to do all the testing myself (there is one clear sky night per 3 months), I gave the camera to a friend of mine who is talented and skilled enough to squeeze the best out of this lil cam when attempting on some Deep-Sky Object imaging… His results are amazing!

Michal Ringes, QHY5L-II

CONCLUSION

What I liked:

  • the camera is small, lightweight and easy to use
  • drivers installed on 1st attempt (using alccd CD)
  • really powerful camera

What I didn’t like:

  • there was some random banding (horizontal) happening occasionally on top or bottom part of the frame making it useless for timelapse (it looked like there was a thunderstorm around the horizon)
  • the lens are (all of them, all CCTV lens I tested) quite distorted and screwed up – not made completely perpendicular to the CMOS chip when focusing so the distortion changed corner from corner based on the actual focus position (you could focus that or the other part of frame, but not a complete image) – but that seems to be problem with every CCTV lens I have ever tested even on different C(s)-mount camera

References

ALccd5L-IIm
QHY5L-II

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Ultralehký, mobilní, stabilizovaný 12V astro zdroj

LTM4613Představa zněla jasně – škálovatelný (s rozumnou, volitelnou kapacitou), malý, lehký, přenosný, stabilizovaný 12V zdroj na astro-krámy. No a jak víme, buď má zdroj dostatečnou kapacitu a je těžký jako vepř, nebo má nedostatečnou kapacitu, ale zas je lehký. Jako nejlepší řešení mě vyšlo jej založit na Li-Po battery packu, který splňuje alespoň tolik, že je vzhledem ke své kapacitě poměrně lehký. Nevýhodou je ovšem pořizovací cena, ale budiž, něco se prostě obětovat nakonec musí…

Vzhledem k dalšímu požadavku, aby bylo na výstupu stále 12V a zároveň nedocházelo ke ztrátě energie (kapacity) tím, že použiji nekvalitní, čínský stabilizátor či step down modul, jsem musel místo 4S battery packu (bych se pohyboval v rozmezí 12-16V dle nabití) jít do 5S, tj. 5ti LiPo baterii v sérii. Tudíž se pohybuji o pár gramů hmotnosti na jeden battery pack výše, ale zase se lépe shání kvalitní (s vysokou účinností přes 92% po 95% podle zatížení) stabilizovaný DC to DC step down modul :) a v rozsahu od 15ti (vybito) do 21V (nabito) na jeden battery pack, vážící 666 gramů a mající kapacitu 5Ah.

Jako ideální step down modul se ukázal býti LTM4613 od Linear Technology, který lze rovnou zakoupit i s osazenou deskou – demo board za příznivých 65 babek (USD), kde si volbu výstupního napětí zvolíme přes jumper. Na vstup jsem přivedl výstup z odpojovače zhotoveného Milošem Zajícem, který mám nastaven na cca 15V, takže když mi dojde šťáva prostě se to celý samo vypne, aniž bych vycucnul poslední zbytky energie z baterry packu/ů, čímž je chráním před pod-vybitím.

Následující obrázky jsou „self explanatory“, samo-vypovídající.

ultralightmobileps12v

Ultra-light (mobile), scaleable, stabilized 12V power supply

ultralightzdroj12v-kompletace

ultralightzdroj12v-finale

Ultra-light (mobile), scaleable, stabilized 12V power supply

Parametry

  • vstup 15-30V (pro můj případ 15-21V) a to 4x battery pack nebo 1x banánek konektor
  • kapacita zdroje podle počtu zapojených battery packů od 5Ah přes 10Ah, 15Ah až po 20Ah a 0.7kg resp. 1.4kg, 2.1kg až po 2.8kg váhy
  • výstup 12V stabilizovaných, 8Amp max

:) cílem je vylézt na vrchol sopky někde v divočině a tam fotit noční oblohu přes ultra-mobilní astrofoto sestavu. Prozatím jsem tento svůj sen realizoval jen částečně a snad jen jednou (Mauna Kea) ale neměl jsem štěstí na jasnou oblohu… tak snad někdy příště!

Odkazy
LTM4613EV Demo Board: Ultralow EMI, 36V, 8A Step-down uModule Regulator
Odpojovač akumulátoru při podpětí programovatelný
Turnigy 5000mAh 5S 20C Lipo Pack
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iCharger 106B-plus 250W 6s Balance/Charger

Rubriky: Technika, recenze, Výjezdy (jednonoční) | Napsat komentář

Zdroj 12V z autozásuvek na mobilní astro s dobíjením

Přesněji řečeno rozvaděč 12V autozásuvek pro použití „na poli“ při focení astrosestavou náročnou na spotřebu proudu s dobíjením mimo dosahu 220V tak, aby nedošlo k poklesu napětí na astro-autobaterii a tímpádem nedošlo k např. resetu montáže či jiného nastavení…

Modelová situace – autobaterie v autě je sice pěkná, ale její kapacita je příšerně malá (stačí zapomenout rozsvícená světla na pár hodin a už nenastartujete) nehledě na přechodový odpor v jedné jediné volné autozásuvce a na fakt, že člověk obvykle potřebuje odebírat několik ampér v kuse. Takže na napájení astrosestavy je nutné koupit nějakou dedikovanou trakční autobaterii, čím vyšší kapacity tím lépe (používám aktuálně 90Ah trakční Vartu (a záložní 75Ah), která má ještě trochu normální rozměry a hmotnost, že se dá unést, dříve jsem měl netrakční 95Ah a po 4 letech měla kapacitu 48Ah). Dále je dobré vědět, kolik ampér ten který spotřebič vyžaduje, u mě to je např. 5A pro hlavní CCD kameru, 2A pro montáž, 2A pro notebook, no a k tomu několik dalších drobností (chlazení, vyhřívání, …, další kameru, další notebook). Mám-li celkový požadavek na odebíraný proud 10A, tak teoreticky mi vystačí 95Ah autobaterie na 9 hodin, prakticky na cca polovinu, podle stáří a hlavně v závislosti na okolní teplotě (mnohdy fotíme i při -15 stupních Celsia a potřebujeme celou noc, třeba 8 hodin). Tudíž je zřejmé, že bude třeba během noci trochu dobíjet.

Klíčovým prvkem je spojení autobaterie v autě s astro-autobaterii vně auta, ze které vedou kabely k vlastnímu rozvaděči 12V autozásuvek a ke spotřebičům. No a zde právě není možné použít běžné startovací kabely. Je třeba si vyrobit vlastní a to jednak z maximálně tlustého vodiče a za druhé na (+) pól přidat diody usměrňující tok proudu jedním směrem a to jest z autobaterie v autě ven nikoli opačně z astro-autobaterie do autobaterie v autě. Tím by totiž došlo během pokusu o nastartování vozidla k poklesu napětí na astro-autobaterii (při startu se odebírá šíleně veliký proud – řádově mnohonásobný, byť jen na kratičkou chvilku) a k resetu či poruše nastavení astrovybavení. Diody tomuto zamezí a tak můžeme vesele startovat během noci několikrát a to úplně bez obav. Navíc, přes zimu obzvláště, je nutné si v autě kolikrát zatopit, aby člověk noc přežil (být někde 10 hodin v -15ti je docela náročné, zvláště mezi pracovními dny), takže spojíme příjemné s užitečným.

Pro vlastní rozvaděč platí, že je opět vhodné použít co nejsilnější vodiče s co nejnižším vlastním odporem. Když jsem před 5-6ti lety začínal, udělal jsem si první rozvaděč na pouhé 4 zásuvky řka, že potřebuji napájet montáž, kameru, počítač a ještě něco (vyhřívání objektivu). Dnes používám stále ten stejný rozvaděč první generace jen upraven o další rozvody, aktuálně potřebuji napájet montáž, hlavní CCD kameru, chlazení dalekohledu, fokusér, vyhřívání dalekohledu, počítač (ten napájí pointační CCD kameru a další z USB portu), EL-panel, … .

Aktuální rozvaděč má už digitální voltmetr na tlačítko a banánek-konektory / zdířky pro rozšíření možností napájení.

zdroj12v-drive-nyni

vlevo - dříve, vpravo - nynější podoba

Takovýto jednoduchý rozvaděč si dokáže postavit každý, kdo umí „dát“ plus na plus a mínus na mínus :)

zdroj12v-autokabelynabijeci

zapojení astro-autobaterie a autobaterie v autě

setupinaction

astrofoto sestava v akci

Na závěr musím poděkovat MMysovi (Martinu Myslivcovi) za volbu diod a zhotovení startovacích kabelů před expedicí Chile 2010.

Shrnutí

  • astro-autobaterii zvolit trakční a s co nejvyšší kapacitou (Ah) ale tak, aby ji člověk unesl
  • udělat si pořádný, masivní startovací kabely s diodama a velkýma svorkama
  • udělat si rozvaděč na těch 12V autozásuvkového konektoru (nebo alternativně kombinaci banánky na kabel (černá, červená) a zdířky do panelu, tj. dva póly pro každý spotřebič)
  • naddimenzovat rozvaděč, tj. 8 přípojek se mi jeví jako optimální hodnota
  • nebýt líný a kromě centrálního vypínače udělat i on-off tlačítko/vypínač pro každou přípojku/zásuvku
  • dbát na tloušťku vodiče, kterým přivedu napájení z astro-autobaterie do svého rozvaděče, používám délku tak 5-6 metrů a tloušťku hooodně velikou, uvnitř vlastního rozvaděče pak o něco menší, aby s tím šlo pracovat
  • připojení na astro-autobaterii buď krokosvorkami nebo přes očka
  • kvalitní autozásuvkový konektor se špatně hledá, ideální je tento, případně obrázek
  • nikde není žádný DC-AC měnič!!! na notebook a jiné příslušenství existuji DC-DC měniče z 12ti V na 15-21V dle volby, viz „Další odkazy“ níže. Je vhodné mít baterii v notebooku z domova plně nabitou! Pokud notebook „prská“, že nemá originální napájecí zdroj (typicky Dell, já tedy používám nejčastěji Toshibu a Lenovo), mělo by být vše i přes to OK, jen nebude baterii dobíjet, což ale ničemu nevadí
  • řízení dražších montáží (Losmandy Gemini, GTD Pulsar apod.) má obvykle „rádo“ vyšší napětí než 12V což se řeší podobným (k notebookům) DC-DC měničem s tím, že koncovku si napájíme dle typu řízení montáže a nastavíme vhodné napětí (používal jsem 16V pro Losmandy a teď pro Pulsar mám nastaveno 18V), např. Ansmann DCPS 2460 Univesal Power Supply DC/DC
  • barevně či jinak označit si jednotlivé kabely od spotřebičů a USB kabely, osobně používám elektroizolační lepenku různých barev a vzorů (červená – hlavní CCD kamera jak napájení, tak USB kabel, černa pointační, zelená vyhřívání atd.)
  • přelepit všechny možné diody, které obvykle svítí velmi jasně (až oslňují) tak, aby v noci opravdu tolik nerušily, za tmavé noci je jas opravdu přílišný!
  • jako 100% mobilní fotič noční oblohy ráno uklízím kabely na jednu hromadu (na karimatku) a pak celou podložku dám spolujezdci k nohám a než dojedu domů mám kabely vysušené a můžu je suché uklidit

Další odkazy
Trakční baterie VARTA Professional Dual Purpose (Deep cycle) 90Ah, 12V, LFD90
120W Compact Notebook Power Adapter PW-3120
Intelligent Car DIY 3-Digit Display Digital Voltmeter Module

Rubriky: Technika, recenze, Výjezdy (jednonoční) | Napsat komentář

Flat Calibration Example (Kodak CCD)

This is just a quick-look example to show how important it is to perfectly well calibrate your flat fields with either master bias (for really short flat field subs taken with interline readout Kodak chips and cameras with electronical shutter only!) or master dark or a combination of master bias and master dark when some kind of optimization (scaling) is used in the calibration process (typically when you do not have a proper length master dark for your individual flat field subs).

Calibration with just a master dark (without a flat field) is a „no-go“ for large CCD chips even with a high-end astrograph having small amount of vignetting.

Master dark frame ONLY calibration.

Calibration with just a master flat field (no darks at all) is also a „no-go“ due to over/under correction of vignetting for our case (Kodak, large surface chip).

Master flat field frame ONLY calibration.

Calibration with both master flat and master dark is „almost-a-go“ in case when you do not calibrate your individual flat field subs. In such a case you may again face some minor over/under correction of vignetting.

Master dark frame AND improper (without flat-dark) flat field calibration.

The correct approach for Kodak, large format chips, is to perfectly calibrate your individual flat field subs with proper length (and temperature) master dark frame (or a combination of master bias and master dark at the same temperature and binning as the light frame subs were taken at when scaling/optimizing techniques are used in order to create a matching master dark).

Master dark frame AND proper (with flat-dark) flat field calibration.

It is normal to see some amount of slight gradient in the images (even in narrow band, namely in the OIII channel) while part of it comes from the real, in some way „polluted“, night sky and some of it might be introduced by a not perfect master flat (which becomes a real problem with faster F-stop systems like below F/4). Flat field calibration is a tough „magic“ even for experienced astroimagers… :(

BTW again, I’d like to emphasize that this approach master dark + flat dark calibration of your individual light frame subs is essential for all Kodak chips and for OSC (Color) versions of Sony chips (to get rid of electroluminiscence and to fix bad pixels in the individual pixels of Bayer matrix). But that’s another story…

Rubriky: Articles in ENGLISH, Pokusy | Napsat komentář