Greens and Stars

Experiences from "Kellotapuli"

noreply@blogger.com (Antti Kuntsi) — Wed, 07 Mar 2012 15:41:00 +0000

Kellotapuli (bell tower, clock tower) is the nickname for my astrophotography gear shelter, given its looks. It's a variation on the rolling roof shelter with minimal footprint (120cm x 65cm base) where the top half rolls off east. This enables using a steep 30/60 degree roof (convenient when living 60deg north) and a wall-sized door. Many claimed the tower would topple seeing it standing at close to 2.5m tall on a hill, but the looks deceive. It may be 65cm wide at base, but in that direction at the 1.2m level there's also the 3.5 meters of track bolted to bedrock at the far end.

The main design principle was to avoid shoveling snow at winter and this was achieved handsomely. A bit of shoveling is still needed to access the lower compartments where I store the EL-foil for flat fields, but next summer I'll build some additional removable shelving and other fasteners to keep the need for lower comparment access to a minimum. The rails froze over once, that caused a two minute delay opening the box. A reasonable improvement over the "out-house" shelter which necessated shoveling snow for a good hour or more.

The design was also based on the assumption that this is for astrophotography only, no creature comforts or visual observation conveniences are necessary. There's a small shelf on the north side for a laptop, power and network outlets on the wall, a small ceramic heater keeping dew out during cloudy nights and that's it. The site has a separate, heated cabin for observers, so a remote desktop connection over LAN works wonders. Almost all aspects have been motorized, polar alignment is a bit of an issue with the Synta mounts in fluctuating temperatures. Although it's mounted on a pier the alignment can be off one half a degree if the temperature changes signficantly. This I guess is mostly due to the very long lower altitude bolt contracting at a different rate than the aluminium mount base. Modding the mount base to allow for a shorter lower altitude bolt should solve this problem. The second option for the current mount is to build a completely new alt-az assembly with linear actuators for an automatic polar alignment.

Over all I'm ready to declare the Kellotapuli a success. Now I can head over to the observatory with camera and laptop in my backbag and start exposing the skies in less than 10 minutes from arrival. The slowest bit now is starting the laptop, running the imaging SW and reaching initial focus. From then on the automation could take over should I have written more scripts, but that's worth a separate blog post later on.

Pacman nebula NGC281

noreply@blogger.com (Antti Kuntsi) — Thu, 02 Feb 2012 17:33:00 +0000

Pacman nebula NGC281
Originally uploaded by Mickut

Day 4 in learning to use PixInsight is starting to yield results.
I tested morphological star size reduction, selective de-saturation with a star mask and very moderate luminance and chrominance noise reduction with a lightness mask to smooth out the boosted shadows while leaving the brighter, better SNR nebulous areas and stars intact.

The year 2011 in a couple of pictures and a few more words

noreply@blogger.com (Antti Kuntsi) — Sat, 31 Dec 2011 11:21:00 +0000

Snowy observatory

The year began in snowy, wintery weather in the south. After frequent and plentiful snow-storms it often took over an hour to dig out the observatory deck and roll the outhouse off the scope.

"Second" light

Despite the snowy conditions and random technical problems, I managed to take a successful exposure of the Rosette nebula.

The test setup

The mechanical shutter and difficult dew conditions sparked the idea for building a microcontroller based dew heater and flat-frame illuminator controller box. After a few nights of tweaking I had my first protoboard build up and running, the flat-panel light level was adjustable after all.

Rosette nebula

At the end of February my "big" project reached its conclusion and my first reasonably good HST palette image ever taken saw the light of day. Rosette nebula in narrowband false color with total integration time of 21 hours was the new par to exceed in coming weeks and months. The project was shot with 2x2 binning since I couldn't get pin-point round stars across the field for some reason with the astro-club's William Optics FLT-110 and the WO FR/FF-III reducer/flattener.

Center of the Heart nebula

My balcony observatory provided with great views as well. As Cassiopeia slowly dips north it becomes visible from my balcony and I was able to use my Celeston C8 and Hydrogen alpha narrow bad filter to capture the central emission nebula and the Melotte 15 open cluster there-in.

Kotkatsaari

And what would a summer be without Wene-WiOL?

Nukkuva kirkkovene

Kuolimolla

I had taken the task of captain, charting our rowing route with plenty of options for camping, lunch breaks, swimming breaks and other breaks as well as alternate routes for various wind directions. After crossing to lake Kuolimo we had five huge rowing boats in the water at the same time, a veritable armada with an advanced sonic weapon called "a slightly tipsy mixed choir".

Reposia Espoossa

In the fall the nights grew dark again and the Sun gave a few nice lightshows with northen lights. I was trying to take a nice time-lapse for a star-trail pic, but it was ruined with an exceptionally bright display while I was happily asleep. Later in the fall I happened to wander outside while photographing in order to do some visual observations of Jupiter. The sky look ominously bright and fearful of unexpected cloud-covers I wasn't the least worried about ruined exposures after watching a mesmerizing display of green and red filling the sky beyond zenith. Definitely the best Aurora Borealis in southern Finland within nearly a decade.

WO odottamassa

Being fed-up with all the snow last winter I built a minimalistic rolling-roof observatory box at Komakallio. It's just barely big enough to fit the WO FLT-110 as well as my C8.

Board with no name?

My project for controlling the dew heater and flat-box took a step forward when my PCBs arrived. "All" I have left now is putting it into a case, write the firmware and PC-end control-SW plus add a few sensors for sky-temp, air-temp, relative humidity and ambient illumination.

Elephant's trunk

The annoying star-shapes issue was solved. The WO FR/FF-III reducer/flattener doesn't work correctly with larger sensor sizes on the FLT-110 telescope. I bought myself a WO AFR-4 reducer and now the stars are round within 5% in the corners. The Elephant's Trunk nebula shows beautiful details despite the short total exposure.

Messier 33 - The Triangulum Galaxy

My main project was the Messier 33 Triangulum galaxy. This has the second longest total exposure, 14 hours, of my astrophoto projects. It's an LHaRGB image, where the letters stand for Luminance, Hydrogen alpha, Red, Green, Blue. The Luminance channel adds brightness to the whole image, RGB channels add brightness and color and the Ha channel is used here to accentuate the bright red hydrogen regions. It took several attempts to get the colors right, although I'm not yet completely satisfied with this.

Pleiades exposed

My secondary fall-project was the Pleiades, I took an hour and a half from the morning sky in September and later a bit more light for this slightly off-tinted rendition. A bit more training is needed for color grading the shots.
The December was effectively lost to clouds, better luck next year.

Instant gratification

noreply@blogger.com (Antti Kuntsi) — Sun, 27 Nov 2011 13:03:00 +0000

Messier 35 and NGC 2158
by Mickut

The open and globular cluster are as close to instant gratification as you can get in astrophotography. No finicky wisps of nebuloisty to stretch out from the background noise, just simple stars and lots of them at times. I'm not sure how much more I could get out of this frame even if I increased the exposure ten-fold. Effectively "all" the stars are already there and the SNR is quite good, so there isn't much to gain from spending a month exposing the cluster. Unless there's some faint nebulosity lurking in the darkness...

Syksy ja sumuiset yöt

noreply@blogger.com (Antti Kuntsi) — Mon, 26 Sep 2011 08:26:00 +0000

Syksyiset pimeät saapuivat taas, valitettavasti syksyn matalapaineetkin tulivat samalla pilviverhoineen. Afrikan tropiikissa alkunsa saaneiden myrskyjen jäänteet kulkevat pitkän kiertoreitin Karibian kautta päätyäkseen Siperian aroille. Siinä missä isot matalapaineet kulkevat parissa päivässä koko USAn itärannikon korkeuden, kestää niillä yhtä kauan ohittaa kapea Suomi, seuraavan rintaman hönkiessä jo niskaan Atlantilla. Tästä seurauksena Suomessa ei syksyllä ole kovinkaan montaa kirkasta yötä, peräkkäisistä kirkkaista öistä puhumattakaan. Matalapaineet tuovat myös mukanaan runsaasti sadetta ja ne harvat kirkkaat, kuulaat päivät päätyvätkin usein sumuisiin öihin, jolloin kaikki peittyy kasteeseen.

Tähtikuvauksen kannalta sumu on ilkeää, sillä sen läpi ei näe kovin hyvin. Kasteen kanssa on opittu elämään lämmittämällä kohti taivaita osoittavaa optiikkaa niin, että sen lämpötila pysyy kastepisteen yläpuolella. Ilman lämmitystä kirkaalla säällä optiikan pinta jäähtyy alle ympäröivän ilman lämpötilan säteilyjäähtymisestä johtuen, täten kosteassa ilmassa jäähtyminen jatkuu alle kastepisteen. Pahimmillaan kosteutta voi kertyä niin paljon, että linssi voi peittyä kokonaan veteen. Veden suuresta ominaislämmöstä johtuen kertyneen veden poistaminen vaatii paljon energiaa, mutta jo melko pienellä lämmityksellä voidaan pitää optiikan pinta kastepistelämpötilan yläpuolella. Liian suurta määrää lämpöä puolestaan ei kannata käyttää, koska tällöin optiikan sisäiset lämpötilaerot voivat aiheuttaa kuvanlaatuoa merkittävästi huonontavia konvektiovirtauksia putken sisään tai pahimmillaan jopa linssin ulkopuolisen ilman pyörteilyä.

Näitä optiikan etuelementtien lämmittimiä kutsutaan huurrepannoiksi, ja markkinoilla on useita erilaisia ja erihintaisia ratkaisuja. Lisäksi liiallisen lämmöntuoton estämiseksi usein käytetään säädettävää ohjainta, jolla vallitsevan ilmankosteuden perusteella säädetään lämmitystehoa juuri ja juuri riittäväksi. Nykyään kaupalliset ratkaisut perustuvat lähes yksinomaan paksukalvovastuksesta, jonka käyttäminen kotikonstein on turhan hankalaa, ja saatavuus pienissä erissä lähes nolla. Tee-itse -henkisille on kuitenkin kaksi muuta toimivaa tekniikkaa, yleisin ratkaisu on juottaa suuri määrä vastuksia rinnan tai sarjaan ja toinen tapa on käyttää vastuslankaa. Sopivan tehontarpeen (ja siten vastuksen) laskemiseen löytyy helppo kaava, P = 0.0606 x D +1.18, jossa D on lämmitettävän elementin halkaisija millimetreinä ja lopputulos on watteja. Tarvittavien vastusten laskemista varten on tehty myös kätevä taulukkolaskentapohja. Suomen oloissa kannattaa tehdä hieman ylitehokas lämmitin (kosteimpina kevättalven öinä sulavasta hangesta vapautuva vesihöyry tuottaa helposti kaiken jäähän kuorruttavat olosuhteet), sillä tehoa on helpompi säätää pienemmäksi kuin suuremmaksi.

Huurrepantojen säätöelektroniikkaa on saatavilla vaihtelevin hinnoin, kalleimpien ollessa useita satoja euroja. Tee-itse ohjaimen saa tehtyä helpoimmillaan muutamalla analogisella komponentilla 555-piiristä PWM-kytkennässä, jolla ohjataan tehotransistoria tai FETtiä, pulssinleveyttä säätämällä voidaan rajoittaa huurrepannan keskimääräistä lämmöntuottoa lähes nollasta täyteen tehoon. PWM-taajuus kannattaa pitää joko hyvin matalana (alle puoli hertsiä) tai kohtuullisen korkeana (muutama kHz), tällöin kuorman kytkennästä aiheutuvat virtapiikit on helpompi suodattaa pois häiritsemästä herkkiä kuvausinstrumentteja. Toinen harrastajan helposti saavutettavissa oleva säätötapa on tuottaa PWM-signaalia mikrokontrollerilla, etuna tällöin on kohtuullisen helppo lisätoimintojen saaminen, esimerkiksi lämpötilan ja ilmankosteuden mukaan automaattisesti säätyvä teho tai tietokoneohjaus USBn kautta. Moderneilla mikrokontrollereilla ulkoisten komponenttien tarve on varsin pieni ja nykyään löytyy myös hyviä TTL-tasoilla ohjattavia FETtejä, jolloin erillistä FET-ohjainpiiriä ei edes välttämättä tarvita.

Oma automaatioprojektini käyttää USB-ohjattua mikrokontrolleria tuottamaan useita PWM-ohjattuja signaaleja, kaksi on varattu huurrepannoille (toinen kuvausoptiikalle, toinen ohjausoptiikalle), yksi valopaneelille ja kolme on varalla. Lisäksi voin kytkeä mikrokontrolleriin 1-wire -protokollaan käyttäviä antureita mittaamaan kosteutta ja lämpötilaa, sekä erilaisia mekaanisia käyttöliittymäkomponentteja tietokoneettoman käytön säätimiksi. Taloudellisesti mikrokontrolleripohjaiset projektit eivät kannata, jos laskee omalle ajalleen minkäänlaista hintaa, mutta harrastuksena ne tuovat mukavan lisän kuvausöiden kokemukseen.

William Optics Flattener comparison

noreply@blogger.com (Antti Kuntsi) — Wed, 21 Sep 2011 18:00:00 +0000

I recently acquired the William Optics Adjustable Flattener Reducer 4 as I wasn't too happy with the image quality I was getting from the local astro-club's William Optics FLT-110 telescope with the William Optics Focal Reducer/Field Flattener III.

William Optics FR/FF III
50 minutes of Ha in 10min subs
Cropped view around target.

Although I had used the WO FR/FF III the last season while using the FLT-110, I noticed my star shapes were way off considering how good the scope was supposed to be. I had put the blame on the less than stellar polar alignment of the mount, especially since the mount was secured to the pier and aluminum base plate only by the central bolt. Needless to say, as the temperature during the imaging season fluctuates between +15 C and -35 C, the bolt comes loose due to thermal effects and the mount starts to drift off. During the summer I built a new observatory for a new EQ6 our club had purchased and I made sure the polar alignment won't move. With the mount aligned I discovered that the horrible looking stars were not caused by polar alignment but an optical issue instead. I played around with the flattener to sensor distance and the star images improved a bit, but the stars near border turned from warp effect to cross shapes. Reading thru forums I found out I'm not the only one faced with the same issue on the FLT-110.

William Optics AFR-4
90 minutes of Ha in 10min subs.
Nearly full field of stack.

After a bit of research I placed an order for the William Optics AFR-4, as it had a reasonably long back focal distance, and more importantly, the flattener lens group location can be moved for 20mm by rotating the lockable adjustment ring. The various posts on forums recommended a distance of 73.5mm for the FLT-110, so I made a rough estimate and started waiting for a break in the clouds. A week later I took another set of frames of the Sh2-101 () so I could make a direct comparison on the images produced by the flatteners using the same equipment. Incidentally the sensor distance was quite good with my first guess and now the sensor tilt is the prominent image quality reducing factor. I was able to reach 1.05px HFR stars at center with the stars in corners were around 1.08 pixels HFR. The image scale is a bit tighter than with FR/FF3, the field of view is 2 arcmin narrower at 97.2 arcmin with the AFR-4 compared to 99.0 arcmin with the best star shapes on FR/FF-III. Of course the field of view with reducers depends on the sensor distance, so the final figure after more adjustments is subject to change.

So far the only negative aspect has been a bit of flare around brightest star in the field, but it could be partly caused by the humidity, as the air was far from clean on the test night. Hopefully more to follow on the experience with AFR-4 as the imaging season 2011-2012 progresses and I reach a better optical alignment.

But what to call it?

noreply@blogger.com (Antti Kuntsi) — Sat, 17 Sep 2011 18:47:00 +0000

Board with no name?
Originally uploaded by Mickut

My automation project for tedious astrophotography tasks reached a new milestone today as I assemebled my new control board for functionality tests. The board has two main duties, one is to control the dew-heater bands and the other, main reason for this, is to control the EL-foil luminosity while taking flat frames. My astro-camera has a mechanical shutter with a limited speed, so the flat frame exposures have to be at least 2.5 seconds to eliminate the shutter movement below a few ADUs. As the LRGB filters pass a lot of light, the light has to be fairly dim to reach such a long exposure with a sensitive camera. Unfortunately, the narrow-band filters are just that: narrow. Using the same low setting on a 7nm SII filter (deep red near infrared) the not-so-warm light of the EL foil is diminished to extinction resulting in almost one minute flat frame exposures. Taking 30-60 exposures at one minute each doesn't sound like something I want to do at 6am, I can now make the light brighter for the narrow band filters keeping the exposure shorter, and brightening the light for wideband filter for extending the exposure.

Board bottom
Originally uploaded by Mickut

I drew the board in KiCad a while ago, and kept upgrading new features, most notably the extra IO-lines were added when I noticed I had an extra ATMega644. A bit of an overlook at the datasheets left me with a grave error in the schema, I had connected the VCCIO pin of the FT232RL to the VUSB instead of VCC network, so I had to cut the trace on the board and jump the SOIC-28 leg to VCC on the ICSP header. Unfortunately I realized this only after my order had already been sent back from iTead Studios, so hacking was necessary.

This would have been relatively easy, but I had found out that the ATMega644 can run an Arduino compatible bootloader called Sanguino and all I needed was a way to reset the board while programming. I had forgotten the reset switch completely, although one can pull down the reset pin on the ICSP just the same. The Arduino also supports auto-reset over FT232RL by connecting the DTR# -pin to ATMega reset thru a series capacitor (pulsing the reset). Not so fortunately the DTR# -pin is one pin over from the VCCIO and in between there's RST# pin that I don't want to touch at all. Plenty of light, magnification and a narrower soldering tip was used to make the bits of wire go to the right spots without solder bridges.

The auto-reset isn't fully reliable, I might have used a wrong value cap in the series. The Sanguino bootloader installation made almost miss a heart beat, as it didn't say what it was doing while writing the bootloader. As you can see, my board relias on the internal clock source of the ATMega, and the first thing Arduino IDE does when flashing the bootloader is setting the fuses to use an external clock source. This caused a few minutes of frustration wondering why nothing works, until I realised my ATMega needed a temporary heart transplant. With a 12MHz oscillator I was able to reset the fuses and then it was time to adjust the Sanguino bootloader code and flashing settings to match my setup. Now I'm able to upload Arduino sketches onto my board and they run jst fine, serial data receive excluded (this seems to be a known bug in Sanguino).

My actual test-code is just basic C-code with avr-libc and avr-gcc. Being able to upload the code thru the Arduino bootloader makes field-upgrades easier, though, since now there's no need to carry the programmer device along. The test-code sets the PWM channels at 50% duty cycle, the fast channels at 4kHz, slow channels at 13Hz and the servo channels at 50Hz with 16bit OCR1 registers for accurate positional control (ICR is set at 19999). The board takes around 10-20mA when operating without load, the possible servos are the only external load on the VCC line keeping the LM7805 from heating up too much. The FETs are N-channel IRF540N, saturating at 4.7 volts, so I can drive them directly with the uC outputs with minimal protective circuitry around the FET. Possible flywheel diodes for inductive loads are omitted, they can be added closer to load if necessary. A bit of probing and coding proved that the circuit works now pretty much as planned, I was able to connect over USB-serial to the uC and change the PWM duty cycle from my computer, and the EL-foil changed its brightness just as expected (non-linearly). For the EL-foil I'm also using a current limiting resistor inline with the load, the 2.2ohm 50W resistor heats up to around 20C above ambient, very close to my estimates on theoretical power dissipation.

Now it's time to call it a day/night, start thinking about those free IO-lines on the side and plan the firmware and PC-side code a bit further into reality.

Oh, what to call it? The ability to use the Arduino IDE after all (when the Sanguino UART bugs are fixed) kind of necessitates something Arduinoish and the astrophotography background should somehow be present in the name as well. Thusfar the best name I've been able to come up with is Astruino, and that's what I shall call it from now on.

Pelican Nebula (IC 5067/5070)

noreply@blogger.com (Antti Kuntsi) — Wed, 07 Sep 2011 07:30:00 +0000

Pelican Nebula (IC 5067/5070)
Originally uploaded by Mickut

The Pelican Nebula is located in Cygnus right next to North America Nebula, and it is in fact the same cloud of glowing hydrogen gas. From our point of view the cloud is split in two forming the more photographed N-A nebula and the Pelican nebula by the dark dust between the Earth and the gas cloud.

The dark dust has a lot of intricate detail I wanted to bring forward by increasing the local contrast using a contrast mapping algorithm.

Via Flickr:
The Pelican nebula in Hydrogen alpha.
Tone-mapped to show the rich low-contrast details, although the "pelicanness" is reduced a bit in the process.

Total exposure: 1h30m.

Komakallion Kellotapuli

noreply@blogger.com (Antti Kuntsi) — Tue, 16 Aug 2011 19:55:00 +0000

Havaintokaudella 2009-2010 havaintoilta Komakalliolla alkoi usein kaivamalla muutama neliömetri satanutta lunta kallioon asti kolmijalkaa varten, ja arvokasta havaintoaikaa kului tähän usein turhankin paljon, varsinkin jäätyneen nuoskalumen kohdalla. Kesän 2010 aikana virisi ajatus tolpan valamisesta lumitöiden vähentämiseksi. Syksyllä 2010 tulikin valettua ison Observatoriokopin luoteisnurkalle tolppa, joka painui kovettuessaan luonnollisesti hieman pohjoisen suuntaan. Tolpan suojaksi löytyi vieläpä sopiva, kookas ja painava suojaputki, jolloin lumitöiden tarve väheni noin puoleen neliömetriin suojaputken päältä. Kaudella 2010-2011 tuli kuitenkin havaittua, että vaikka seurantapään ja kaukoputken tykötarpeineen saa nyt noin vartissa kokoon, kestää napasuuntaus vielä turhauttavan paljon. Varsinkin talvella tuo aika on pois havaintoajasta arkipäivinä, jolloin valoisana aikana ei vielä ehdi paikalle. Kun Komeetta osti EQ6 seurantapään, syntyi tarve tehdä kiinteä säilytyspaikka, jossa aktiivikuvaaja voisi säilyttää lähes valmista, napasuunnattua kuvauskalustoa. Kaudella 2010-2011 Komakalliolla oli usein kolme tai neljä aktiivihavaitsijaa, joten tällaiselle oli selvästikin tilaus.

Kesällä aktiivikuvaajien keskuudessa pyöriteltiin erilaisia ideoita rullaavista kopeista kääntyviin kattoihin, mutta mikään ideoista ei oikein tuntunut erityisen toimivalta. Pienen mittailun ja mallailun jälkeen oli selvää, että suojakopista on tehtävä pohja-alaltaan pienin mahdollinen, ja se puolestaan rajasi vaihtoehtoja lisää. Rullaava koppi vaatii tasaisen liukualustan ja paljon lumitöitä toimiakseen, liukuva katto taas paljon tilaa tolpan ympärille laitteiston asentamista varten. Taittuvaa kattoakin pohdittiin, mutta ongelmaksi muodostui pelkästään puutavaralle laskettu 25-30kg paino ja hankala saranointi. Heinäkuun alussa keksin ratkaisuksi liukuvakattoisen havaintosuojan ja syrjään rullaavan astrohuussin välimuodon, jossa puolet kopista liukuu syrjään, ongelmana oli vain rullaavan osan suunta. Pohjoiseen ei voinut tehdä kiskoja, koska pääsy "Huussille" eli WilliamOptics -putken suojalle oli tuota kautta. Lännen puolella on parkkitilaa ja kulku työmaakoppiin ja isolle kopille, idässä ja etelässä rajoitteena ison kopin katto ja kiskot. Ison kopin katto ei kuitenkaan rulla aivan kiskojensa päähän ja varmistusmittauksen jälkeen olikin selvää, että kiskot on asennettava noin metrin korkeudelle kohti itää. Tällöin yläosa rullaa ison kopin kiskojen päälle ja ison kopin katto mahtuu yhä aukeamaan kokonaan. Pohjavalu tehtiin heinäkuussa, mittaa pohjalle tuli 120cm etelä-pohjois -suunnassa ja 70cm itä-länsi suunnassa, kiskojen matkustuskorkeudeksi 100cm pohjalaatan yläpinnasta. Näillä mitoilla tarvittava betonin määräkin oli kuljetettavissa henkilöautolla ja valettavissa kahden hengen voimin. Viisi säkkiä, neljä rautaa ja 12 osittain upotettua kierretankoa myöhemmin tolpan ympärillä oli kiiltelevä betonivalu, jonka ulkoreunoja kiersi sojottavat kierretangot rungon pulttausta varten.

Heinäkuun lopussa sain piirustukset valmiiksi ja tarvelistan laadittua, rakentaminen voi siis alkaa. Kajn kasvihuoneessa työturvallisuudesta tinkimättä sahasimme pohjakerroksen seinävanerit valmiiksi ja kävimme hakemassa muutaman juoksumetrin puuta ja kaksi levyä vaneria. Alin, betonia vasten oleva kerros sahattiin painekyllästetystä 50x100 millisestä puusta, naulattiin kasaan ja kiinnitettiin kierretankoihin. Kopin alempi kotelo sai raamikseen 48mm x 48mm puusta nousut, 50x100 takapalkin ja sivuihin 3.5m pitkät kiskot. Kaikki liitokset rungossa tehtiin talttaamalla loviliitokset ja kiinnittämällä ne liimalla ja ruuvein. Kiskojen peräpäähän pystypuiden pohjaan laitettin pienet, säädettävä tolppakengät, koska kiskojen pään kohdalla kallion kumpuilu ei mahdollistanut tarkkaa mittaan sahaamista, lisäksi näin puu saatiin sopivasti irti kalliosta. Kiskojen päälle löytyi sopivaa 40mm leveää alumiinilattaa, johon porattiin upotetut reiät ruuveille, joskin kiinnitykseen käytettyjen ruuvien kanta erosi hieman upotusten sovitukseen käytetystä ruuvista ja kannat jäivät hieman ylös kaikesta huolimatta. Lattojen alle levitettiin noro polyuretaaniliimaa, ja kiskot ruuvattiin paikoilleen. Kiskojen päälle päätettiin laittaa suuret kuulalaakerit rulliksi, ja yläkopin runkolankkuihin kaivettiin sopivat kolot ja akselireiät. Rakenne on osittain vastaava kuin isossa kopissa, joskin pienempään tilaan mahdutettuna: kuulalaakerit puristetaan holkkien avulla rungon sisään akselireiän kohdalta. Tässä tapauksessa toisella puolella on noin 25 milliä palkin mäntyä ja toisella puolella 15mm vaneri.

Yläosan rakentaminen puuvalmiiksi sujui myös nopeasti parissa illassa, ainoita hankaluuksia tuotti kattotuolien tarkka mittaaminen, harjakaton kulmat ovat 30 astetta pohjoisella puolella ja 60 astetta eteläisellä puolella. Näillä kattokulmilla saadaan kopin sisätila tehokaasti maksimoitua ja sivupuiden pituudet pidettyä yksinkertaisina sekä seinävanerin kulutus mimimoitua. Avuliaista neuvoista huolimatta ratkaisu löytyi ja rakentaminen eteni päällystämällä kopin seinät vanerilla. Kattomateriaaliksi päätyi paksu kattohuopa, toimistolla sermin toiselta puolelta löytyi ylimääräinen rulla huopaa, jota oli juuri oikea määrä, oikean kokoisina paloina.

Kattohuovan kiinnityksen ja ovien teon jälkeen oli aika nostaa koko komeus harjakorkeuteensa, hieman reilut kaksi metriä. Torni sai jo runkovaiheessa monia nimiä, kuten kaappikello ja kellotorni, koska itse kopin rakenne on itä-länsi -suuntaan verrattuna hämäävän kapea ja korkea, sillä kiskoja ei juuri mielletä rakenteen kantaviksi osiksi. Korkeus korostuu varsinkin kun tornia katsotaan keskimäärin alarinteestä, parinkin metrin päästä katsoja on lähes metrin tornin kohtaa alempana. Rakenteellisesti torni on tuossa huojalta vaikuttavassa suunnassa hyvin tukeva, tukeutuuhan koko metrin korkuinen alaosa 3.5 metrin matkalle. Yläosaksi jää raskas, 70cm syvä, reilun metrin korkuinen koppero, joka molemmissa ääripäissään pysäköityy ruuvisaranoista tehtyihin kippiestoihin. Sivuttaisliikkeen estämiseksi yläosan molempiin rullapuihin laitettin kaksi sivulaakeria ulkopuolelle ja yksi sisäpuolelle pitämään seinät kiskojen suuntaisina. Näiden kiinnitämisen, lukkosalvan ja ilmastointireikien teon jälkeen koppi olikin valmis maalattavaksi. Komakallion harmaata sävyä en löytänyt mistään järjelliseen hintaan, mutta onneksi funktionaalinen observatorionvalkoinen on maalien perussävystöä. Puunsuoja-aineellista ulkopohjamaalia kului perjantaina kaksi litraa ja lauantai-iltana sen päälle meni kolme litraa öljymaalia. Tätä kirjoittaessa kopista puuttuukin enää sähköpistokkeet, tietoverkkopistoke ja jonkinlainen pieni kosteuden tiivistymisen torjuntaan sopiva lämmityslaite, kuten pienitehoinen hehkulamppu.

Mitäpä tämän kopin tekemisestä tuli opittua? Ainakin se, ettei suunnitelmiin kannata tehdä muutoksia kesken rakentamisen, vaikka kuinka joku pitää omaa ideaansa parempana. Parissa kohdassa kävi nyt niin, että suunnitelmista poikkeava "helpompi" ratkaisu tuotti useita tunteja enemmän säätötyötä kuin suunnitelman mukaan tehtynä olisi mennyt. Lisäksi rakentamisen loppusuoralla ideanikkarit ajettiin nuotion ääreen paistamaan makkaraa ja kopin läheisyydessä keskityttiin pohdinnan sijaan rakentamiseen piirrustusten mukaan, varsinkin viimeinä isona puutyöiltana, jolloin monia upotuksia ja leikkauksia veistettiin ja jyrsittiin tarkasti mittojen mukaan sivurullille ja ovien heloille. Kaikesta avusta huolimatta valmista tuli, aikaa kului vain yksi viikonloppu ja kahden viikon illat, eli minulta vajaat 40 tuntia ja muilta rakentajilta (keskimäärin eteenpäin auttoivat ainakin Kaj Wikstedt, Lauri Kangas, Panu Lahtinen, Mika Luostarinen ja Samuli Vuorinen) parista tunnista reiluun kymmeneen. Toivottavasti pian sää selkenee, niin pääsen ottamaan kalustosuoja Kellotapulin ensivalot.

Niin, miksi nimeksi tuli lopulta Kellotapuli? Syyhän on ilmeinen kopin rakenteesta johtuen, eikä pelkästään ulkonäöllisistä syistä: katon eteläpuoli osoittaa lähes suoraan taivaannapaan ja eteläseinä etelään, joten räystääseen kiinnitettävällä katon suuntaisella viisarilla eteläseinään saadaan piirtymään aurinkokello.

Kuvia
Katso Kaappikelloprojektin kuvasarja Flickrissä.

Testing continues

noreply@blogger.com (Antti Kuntsi) — Sun, 22 May 2011 16:31:00 +0000

Testing the imaging quality proved difficult to say the least. With nine points to adjust and some structural flexing focusing and collimation is almost impossible. Overall the system seems a bit soft and low contrast, but at least on H-alpha narrowband filters it gave a fairly good resolution on the focused area. Still, the high intensity regions bleed over darker ones reducing the contrast a bit too much. Additional baffling migh help keep the stray light away, but the glow around bright areas does indicate that high contrast isn't a priority for these lenses.

Initial focus testing

noreply@blogger.com (Antti Kuntsi) — Sat, 21 May 2011 09:42:00 +0000

Initial focus testing
Originally uploaded by Mickut

Via Flickr:
I wish I had a DSLR with live view, it made focusing and testing a lot easier. At short focal lengths the image is soft and low contrast, so unfortunately the optics seem useless for a fats, widefield astrograph. I still have evaluate at a significantly longer FL to see is it any good as a planetary scope.

Short and stout

noreply@blogger.com (Antti Kuntsi) — Sat, 21 May 2011 09:38:00 +0000

Short and stout
Originally uploaded by Mickut

Via Flickr:
The telefocus optics keep the overall length very short compared to focal length. This rig is a major pain to collimate, but luckily its main purpose in life is to evaluate general usefulness of the lenses and the distances between flanges for a suitable focal length and sufficient back focus distance.

Assembled for testing

noreply@blogger.com (Antti Kuntsi) — Sat, 21 May 2011 09:37:00 +0000

Assembled for testing
Originally uploaded by Mickut

Secondary secured to the board

noreply@blogger.com (Antti Kuntsi) — Sat, 21 May 2011 09:36:00 +0000

Secondary secured to the board
Originally uploaded by Mickut

Via Flickr:
Camera mount in the background

Clamps for main lens

noreply@blogger.com (Antti Kuntsi) — Sat, 21 May 2011 09:35:00 +0000

Clamps for main lens
Originally uploaded by Mickut

Lots of clearance

noreply@blogger.com (Antti Kuntsi) — Thu, 19 May 2011 20:13:00 +0000

Lots of clearance
Originally uploaded by Mickut

I didn't break anything, although it looked a bit dangerous at times. I had a small measurement error, so all holes needed to be enlarged a tad.

Drilling

noreply@blogger.com (Antti Kuntsi) — Thu, 19 May 2011 20:12:00 +0000

Drilling
Originally uploaded by Mickut

Making a hole for the main lens. The small central hole was used to align all boards for threaded rod holes and as a guide hole for the cutter tool. Everything should be fairly well centered for getting the measurements right for the actual OTA.

Raw material for test rig

noreply@blogger.com (Antti Kuntsi) — Thu, 19 May 2011 20:10:00 +0000

Raw material for test rig
Originally uploaded by Mickut

Via Flickr:
Thick, 27mm plywood for the main lens, thinner 10mm ones for negative lens and camera mount. Four holes will be drilled into each, three for threaded rods and a big one at the center for optics.

Astrograph project starts

noreply@blogger.com (Antti Kuntsi) — Wed, 18 May 2011 15:22:00 +0000

Fast positive triplet
Originally uploaded by Mickut

Negative doublet
Originally uploaded by Mickut

My mystery optics order from Surplus Shed of a very fast air spaced triplet and negative doublet arrived today. The weight is a bit of a concern, the triplet lens (D=155mm, f/1.23) weighs a whopping 2.5 kg and creating a stable focusable system for these two is going to be challenging. The smaller, but not lesser, negative doublet weighs "only" 414 grams, and is unmounted, edges painted black with elements glued together. I took a chance on these, as the big lens for half off, and at a total price well below 200€ shipping, taxes and customs included wasn't too bad if these can be combined to even a reasonably good fl=465mm f/3 astrograph. Since I'd use mainly narrow band filters with it, I'm not too concerned about color aberrations, mainly about the image plane flatness for the fair size CCD sensor in SXVR-H18.

The next step is to create a temporary rig for determining correct spacing between elements in order to reach the desired focal lenght, the thin lens equations say it's in the order of 150-160 mm, but this is now the real world. In theory short test exposures should be doable with it as well before creating the actual tube assembly.

The structure for the OTA served a challenge, as the back focal distance from the negative element to image plane at infinity focus is fairly short, in the order of 80 millimeters at desired focal length. This leaves out the option of building a rigid tube and attaching a commercial focuser at the back, but I realized I might just be able to construct a Huge Crayford focuser and put the optics into the inner tube and attach the camera to the outer tube, eating only 15-20 millimeters of the focus travel. As a result the final tube would end up around 20cm diameter and 20cm long looking more like a snare drum than a telescope, but who cares.

The Great Orion Nebula narrowband

noreply@blogger.com (Antti Kuntsi) — Tue, 15 Feb 2011 18:43:00 +0000

January 2010 version of M-42

The Great Orion Nebula narrowband
Originally uploaded by Mickut

I've learned a few things over the fairly short period I've been trying to do astrophotography, here's the ever-so-cool M42 with my current capabilities. As a comparison, side-by-side from January 2010 and February 2011 the same target. Naturally, part of the difference comes from changes in equiment used, the 2010 was shot on a Canon 350D thru an el-cheapo achromatic fl=1000mm f/10 refractor with racket-and-pinion manual focuser seated on tripod-mounter HEQ5 mount and no guiding. For the 2011 version I used Starlight Xpress SXVR-H18 CCD-camera, high-quality Baader filters, guided exposures with dithering and for optics I have now access to the astro-club's William-Options 110-FLT on pier-installed EQ6 mount.

Many small changes a small change in image makes. Oh, and the image on left was taken at nearly new moon, and the newer version is 70% full moon glaring right above Orion.

NGC7000 - LBN354

noreply@blogger.com (Antti Kuntsi) — Sun, 28 Nov 2010 22:26:00 +0000

NGC7000 - LBN354
Originally uploaded by Mickut

Oh well. If it can fail, it will fail.

Not sure if anything went smoothly tonight, first I went almost off-the-road then got nearly stuck on the hill to the imaging site. When there, the scope shelter was buried in a foot of snow and the locks were frozen. Finally I got almost everything assembled, simply to realize that the power-cord from the transformer to 12V distribution block was left home. Luckily I found one in the nearly warm cabin, so it was time to fire up the gear. Velcro glues peeled off the mount in the -20 temperatures, and I had to fetch a rope to tie the distribution block to the mount. Quite soon it was obvious that nothing worked perfectly, so park the scope, dis- and reconnect all wires, restart applications and everything seems to work nicely for a change. Except, when focusing I noticed that the shutter isn't fully open on all of the frames. Tried a few longer exposures and the same thing continued, the upper half was more likely to go all the way off-sensor, lower half got stuck one third the way down. In six hours I managed to get 30 minutes of botched luminosity instead of targeted 3+ hours of LRGB data.

Slow progress is still progress

noreply@blogger.com (Antti Kuntsi) — Wed, 17 Nov 2010 14:08:00 +0000

My simplistic SW-project for automating the tedious task to center on a target is slowly bearing fruit. At last I have a GUI written that can be used to test whether my library works correctly or not.

The current capabilities of the GUI are capturing an image (at least screenshot, ASCOM and from file works), solving it with astrometry.net -solver, syncing and reslewing an ASCOM compatible telescope, and calculating the distance from assumed target and solved image center.

I'm still not decided on the name, currently the library is AstroMate and the preliminary name of the GUI is AstroTortilla. Hopefully I end up with a single name, although the second utility based on the same library is an alignment helper (currently unstarted and unnamed) based on automatic imaging and solving when moving on the RA axis.

The end of a season

noreply@blogger.com (Antti Kuntsi) — Sun, 14 Nov 2010 16:53:00 +0000

Yestarday was the end-of-season party at the golf club, featuring a fairly funny comedian trickster who had a couple of new tricks up his sleeve, but mostly his definitely well practiced quips on people and events around made an impression. This year I didn't succeed on any of the competitions, so hopefully I get to practice a bit during the winter and early spring in order to improve my game come next summer. This season was definitely "ruined" by the short game. On the Hill course I reached the green from tee five times, and on 15th three times, didn't score a single eagle. What's even worse is that out of those eight chances for an eagle I made only two birdies. Anyone willing to go practice with me, just to make sure that practicing would happen?

Blog relocation

noreply@blogger.com (Antti Kuntsi) — Wed, 10 Nov 2010 13:00:00 +0000

I've relocated my old blog(s) here from Wordpress and MovableType, and it was almost a straight forward conversion using the google-blog-converters-appengine web-services. Only some minor issues like character encoding didn't auto-convert to UTF-8 so that had to be done by hand, and one of the blog-posts had an eight-dash line which in MovableType export file marks the end of a blog-entry. This caused the XML to be malformed and the entry importing froze without indication of error.

All in all this should now be my real blog, some old entries are likely broken, especially the ones trying to show images in pop-up windows.

The Running Man - NGC 1973, 1975 and 1977 in LRGB

noreply@blogger.com (Antti Kuntsi) — Wed, 10 Nov 2010 10:56:00 +0000

The Running Man - NGC 1973, 1975 and 1977 in LRGB
Originally uploaded by Mickut

LRGB image of the often neglected companion of M42 The Great Orion Nebula. The Running Man nebula is a combination of an open cluster and reflection, emission and dark nebulae. I wanted to show the eerie faint red glow of the ionized hydrogen behind the bright reflective parts as well as the immense depths of darkness available in the vast nebulous region.

The battle against reflections continues. I've been suffering from horrendous internal reflections, and after matting most of the inner surfaces I still have a serious problem with something reflecting to the edges, the current suspect is the inner surfaces of the filter rings. Time to go looking for a very dark matte black with an extremely fine pigment.