inFINNity Deck

Hi Wim, This is indeed typical for overhanging wire(s), but could also be caused by the edge of a dome's shutter (or another edge). Is your equipment in a domed observatory? See my white-paper on this for more info: https://www.dehilster.info/astronomy/imaging_artefacts.php Nicolàs

In general a ratio of 3x pixel-size should suffice unless you are imaging from Mount Everest or using the HST or JWST (thanks to lack of atmosphere), while going above 4x only is of interest in the blue end under those conditions. Please note that using 3x makes exposure times significantly shorter compared to 5x. I have written two articles about this, best to start with the second one (which directs you to the first): https://www.dehilster.info/astronomy/optimal_focal_ratio_part_2.php It includes two methods to check whether or not the images are oversampled (mine are when imaging using 3x pixel size and an 11" SCT @ f/20). Nicolàs

Hi Hughsie, this capture was six days before yours (19 June 2020 15:38UTC): My imaging and processing skills were still pretty poor, but having those prominences visible was a jaw-dropping experience at the time (and there was one whole sunspot at the upper-left!). What a difference a few years make (27 June 2024 08:23UTC) Such a shame that she will go back to this quiet featureless orange we saw some four years ago.... Nicolàs

Hi Andy, the focus point will move slightly further away, about 60% of the thickness of the two glass wedges (I believe they are approximately 4mm each, so 8mm together, and thus the focus point will move backwards (i.e. towards the camera) some 3mm. But I think you mean that the minimal camera distance will move further backwards as well due to its physical length. Depending on how you mount the ADC it takes at least 26mm extra space between focus-tube and camera (from which we can subtract those 3mm for the additional focus distance). Nicolàs

If you have an ADC at hand, try to incorporate that in your imaging train. Moving the handles to a non-zero position should remove Newton rings, see my website: https://www.dehilster.info/astronomy/removing_newton-rings.php Nicolàs

Hi Carole, that form should indeed do the trick, I filled it out some years ago and still use the free version of TV. If you still experience issues I can recommend AnyDesk. I had the commercial-use issue with a Canadian friend while trying to assist him setting up his observatory a few years ago. As action from TV was not instantaneously at the time we switched to AnyDesk and still connect that way in case he requests for assistance. Nicolàs

Hi David, for a first attempt your image is not too bad, and much better than I managed the first time! 🙂 Over time I have written three articles about solar imaging, the third one being the method I still use (the method in the second article was way too complicated). The third article shows how to produce inverted solar images and how to get the sun in your scope's sweet spot (but that is pretty okay in your case). https://www.dehilster.info/astronomy/solar_imaging_part_3.php Although I still use the method as explained in the article, I managed in the meanwhile to improve on sharpening, something I explain on my Solar Imaging page: https://www.dehilster.info/astronomy/sun.php Nicolàs

Ok, that is interesting. The tilt can be checked by placing a Cheshire eyepiece in the focuser and brightly illuminate it while the lens-cap is on. If the lens-cell is tilted you will not see concentric reflections of the Cheshire's reflector. Nicolàs

Hi Dan, indeed it is quite curious why these artefacts are not point symmetrical. Did you check the front of the lens-cell to see of the are any small uneven spots along its circumference? Do you also see the artefacts in each and every sub? Nicolàs

Hi PottyMonster (is that your real name?), the effect you see could be an uneven spot along the edge of the aperture, although I would expect it to be symmetrical, which it is not in your case. The same for pinched optics, these should be symmetrical as well. The Tak FSQ85 indeed has these dark spikes, which are always oriented perpendicular to the centre of the image. Most likely cause is an unfortunate lens spacing in combination with the type of coating of the lenses and that they are the result of physical amplification and extinction of the light. More information on imaging artefacts in a white paper on my web-site: https://www.dehilster.info/astronomy/imaging_artefacts.php Nicolàs

If this photo is the pin in your focuser, then that is not the original one. The pin should be smooth, only having a smooth thinner section where the large balls run against. The original pins are made of hardened steel, not sure if the dowels you found are made of it as well. If not, they will be too soft. cheers, Nicolàs

Hi Giles, that cage should indeed be properly filled as otherwise the pressure of the ring-nut does not get properly and evenly distributed. And replace all balls, so that they all have the same size. Then when tightening do it in steps and test whether it holds enough load. When overtightened the central pin may get dented at which stage the focuser gets beyond repair (unless you can source another pin). Nicolàs

Hi Giles, see fig.3 on my webpage about my SkyWatcher Esprit 150ED: https://www.dehilster.info/astronomy/skywatcher_esprit_150ed.php The tiny balls, 18 in my FeatherTouch focuser, should fill the whole bearing. The purpose of the large balls is to create friction between the central thin pin and the conic outer bearing cage. This friction is created by tightening the large brass ring-nut, which pulls the three balls down in the conic cage, and to avoid that this causes too much friction between the gear housing and that nut a bearing with small balls is placed between them. As I wanted zero slippage I replaced the whole friction planetary gear by teethed planetary gear from a electro-motor gearbox (see above page). Nicolàs

Hi Andro, I have written software (FITSalize) to do sub arc-second level deformation measurements using a stationary scope and plate-solving. During development, based on the algorithms in J. Meeus, Astronomical Algorithms, (Richmond (VA), 2005), I tested my software against Stellarium and soon found out that Stellarium corrects for precession and nutation, but not for aberration (the phenomenon where celestial objects exhibit an apparent motion about their true positions based on the velocity of the observer). Precession and nutation are accurately corrected for, I could not find significant differences with my software. In order to be still able to compare the results with Stellarium I made the aberration optional. Nicolàs

Hi Alan, I just saw this thread last evening, so a bit late to chime in. I built my own dome six years ago of corten steel (base ring), pine (rafters), plywood (first layer of cladding), and zinc (final cladding), the construction of which can be found on my website: https://www.dehilster.info/astronomy/building-an-observatory.php Regarding your questions: Wind: it is a very good wind breaker, I have been imaging and observing quite often in conditions that seemed to be unfavourable. If you are going to build your own dome you need to avoid any openings larger than 10 millimetres that cannot be closed as the wind will blow in rain, hail and snow. Size: my dome has an inner diameter of 2.8 metres, which is fine when I am alone or only with my wife, but not suitable for more than four adults. I'd recommend a diameter of at least 3 metres (yes, 0.2m already makes a difference), but preferably at least 3.5 metres, that will easily accommodate around 8 adults. Move house: why, if you have an observatory? More seriously: you are moving to a new home and already considering selling it? In other words: do not live on fears! My wife and I hope to move from our current home with our feet forward first. In case future decides otherwise we probably have bigger concerns than an observatory on the roof of our house. A motor for controlling the dome azimuth is a must, for controlling the shutters is nice to have, but so far I am doing without and I have not missed it yet (for my azimuth-motor solution, see https://www.dehilster.info/astronomy/dome_automation.php). Main advantage of a dome is that you can do maintenance and test-runs while the weather is poor, most ROR domes do not allow for the mount to turn when closed. Domes also do have a downside: whilst very comfortable under windy/cold conditions, the capacity of a dome to provide this also results in what is called dome-seeing. Especially when doing solar (but at times also planetary) imaging the dome seeing can have a significant effect of the quality of the collected data. One way to overcome this, is to have the option to open a door or large window opposite or below the slit to allow a steady airflow (in our case the observatory is 7 metres above ground level and we can have all doors open, creating a chimney effect that brings cool air). Looking forward to your progress on this! Nicolàs

I use an ADC to get rid of the Newton rings. It has the added advantage that you can move the solar disc into the sweet-spot with it. Nicolàs

Those four bolts (six in my pier) are also referred to as a "rat-cage" (or "rat-box" as you called it yourself) of which is said that it would ruin the stability of your set-up. My rat-cage is very low, but friends of mine have 'decent' rat-cages and no issues at all. As long as the bolts are thick enough and the set-up properly balanced, the rat-cages are fine (IMHO that is). Nicolàs

Hi Vox24 (is that your real name?), both have some wisdom and truth in it. I am a hydrographic/land surveyor for 35 years now and know a fair bit about setting up all kinds of optical instruments on tripods, piers, etc. In addition I built my own domed observatory six years ago. Setting-up instruments on a level base is always easier than on a non-level base. But as mentioned, there is no need for the base to be level. In astronomy doing a polar alignment is easier on a level base simply because when the base is level the altitude of the mount does not change when the azimuth of the mount is changed. On a non-level base the altitude will change and as a result doing polar alignment may require a few more iterations in that case. So, for convenience, it is good to have the base level, but that is all there is to it. Nicolàs

Excellent work as always! Nicolàs

Nice to also see the Jovian moons that clearly in above image! Nicolàs

Yesterday I had another chance, this time it stayed long enough clear to shoot 20 x 15s subs in RGB and 60 x 15s luminance. Processing was thus now done with luminance instead of the blue channel as luminance. Capturing done between 19:35UTC and 20:08UTC with the SkyWatcher Esprit 80ED and ZWO ASI1600MM Pro Cool. Unguided tracking on the comet. P12/Pons-Brooks was at that time just south of Hamal in the constellation Aries at a distance of 241 million kilometres from Earth (1.611AU). The bright star in the end of its tail is HIP10657, the one at the left is HIP10795. Nicolàs

Here are two nice resources related to solar activity and sunspots: http://haso.unex.es/haso/index.php/on-line-archive/ https://svalgaard.leif.org/ A recent work that I would recommend is C. de Jager, S. Duhau, A.C.T. Nieuwenhuizen, Solar Magnetic Variability and Climate, (Alkmaar, 2020). Kees the Jager was a renowned Dutch solar astronomer and published this work when he was 99 years of age! Weather permitting I do sunspot observations daily both for a project led by Leif Svalgaard and for SILSO. My data is archived at HASO, hence above two links Nicolàs

Tonight had had another chance. Again weather was not quite cooperative. First I had to wait for the clouds to disappear, then, 10 minutes after imaging started, fog started to form. Luckily my observatory is 7 metres above ground level, so not too much issue there for the first five minutes, but it kept me from shooting luminance. Same processing as above. The bright star is Hamal. Nicolàs

Just found this thread. My last chance to image the comet was almost a week ago on the 24th around 19:43UTC: Imaging done in RGB using a SkyWatcher Esprit 80ED, ZWO EFW with ZWO RGB filters and ZWO ASI1600MM Pro Cool. Twenty subs of 15 seconds were collected per channel while a force 5-6Bft wind was pestering my set-up head-on, causing quite a few subs to be useless. Unguided tracking was done on the comet using a 10Micron GM3000HPS mount. Processing in APP both on the comet and on the stars, then recombined. Sadly enough clouds arrived at the moment I wanted to shoot luminance, so I decided to use the blue channel as luminance instead. Nicolàs

Hi Birman, I have written an ASCOM Generic UPS SafetyMonitor: https://www.dehilster.info/astronomy/ascom_generic_ups_driver.php Provided you use an UPS that uses the Windows logbook to log its status (for tested models see near the bottom of that page), the SafetyMonitor can trigger events in your imaging software such as parking mount and dome, warming up the camera. If the UPS is allowed to shut-down the PC a simple on-shutdown script can be used to shut down the mount (provided it ca be shut down using a command, see https://www.dehilster.info/astronomy/mountcmd.php). Nicolàs