inFINNity Deck

Thanks! Not sure if James was was of much help, seemed to have been tied up with his own stuff... Really, that web was not there when I started the sequence the evening before I found the web, amazing how fast James delivered... Nicolàs

We have this little critter called James, who managed to produce his web in our observatory last night while imaging. I kindly requested him to do this elsewhere... Luckily he did not interfere with imaging... SkyWatcher Esprit 150ED, ZWO ASI1600MM Pro Cool, ZWO NB-filters. 36 x 420s H-alpha, 62 x 420s O-iii and 64 x 420s S-ii, 18 hours and 54 minutes integration time in total (8, 10, 11 and 12 August 2022). Processing with APP, Siril, PSP and Topaz. Nicolàs

I am not sure about the Cassegrains, but have been fiddling with a few RCs (8" and 10") and found the focal length to change with about 10-11 times the change in inter-mirror distance. Best is to change the distance and then test the scope using a Ronchi-test. Gerd Neuman sells these great photographic Ronchi filters, which can easily be mounted to a camera (with lens!) to test the inter-mirror distance. I have written an article on RC-adjustments. It is in Dutch, but opening it with Chrome should result in a reasonable translation (scroll down to step 3 for the Ronchi-test): https://www.starry-night.nl/stap-voor-stap-collimatie-van-een-rc/ I have to say that the Ronchi test on a RC is not terribly sensitive, but then, if the test says it is okay, the scope should perform fine. Nicolàs

Got it around 14:36UTC with a Lunt LS80THA, TeleVue 2x PowerMate, ZWO ADC and QHYCCD QHY163MM: Captured 500 frames @ 1ms exposure time, assisted by a Solar Scintillation Seeing Monitor (grabbing anything better than 2.5" seeing), stacked 25% with AutoStakkert!3. Post-processing with PSP (Unsharp-Mask), ImPPG (Lucy-Richardson Deconvolution, histogram inversion) and PSP again (colourize, vibrancy, mirror and crop). Full resolution on my server. Nicolàs

SCTs and MAKs can do a proper job on solar imaging, especially for high-res imaging. This is an example of white-light imaging using a C11 EdgeHD @ f/20 with Baader ND5.0 foil and Baader Continuum filter: But mind you that going over about say 150mm-180mm aperture creates seeing-related problems. Above image is one of those rare occasions that I could actually image with that scope. In addition full-disc recordings are impossible with this scope/camera combination, see this recent post: Lunt nowadays has day-and-night scopes, which can be used for white-light and H-alpha imaging. The idea is to have a single scope that can be used for deep-sky, white-light (requires a white-light filter) and H-alpha by swapping the whole focuser/etalon unit. If you want to learn more before acquiring a scope, I would suggest reading C. Viladrich, e.a., Solar Astronomy: Observing, imaging and studying the Sun, (Saint-Lys, 2021). HTH Nicolàs

It very much depends on focal length, aperture and seeing. I observe the sun daily (weather permitting) using a Galilean type telescope and image it using a SkyWatcher Esprit 150ED @ native focal length (1050mm). With those two scopes the sunspots are small as shown by @TheycallmeRiver, granulation is only marginally visible with the Esprit and sometimes details within the umbra show. I also regularly observe the Sun using a Celestron C11 EdgeHD, Baader ND5.0 foil filter and a Polaroid filter. When seeing permits, one can see granulation and details within the umbra and penumbra. For the C11 I normally use a TeleVue 41mm Panoptic eyepiece, which gives a full disc view with much more detail than the image shown by @TheycallmeRiver. Under good conditions I use a Ethos 21mm or 17mm eyepiece to see more detail. When seeing is poor, the C11 is best left at piece, it performs much less than the other scopes. If you want to prominences a H-alpha set-up is required. Nicolàs

Lunt supplies blocking filters of various diameters, especially for imaging with large and even larger sensors: https://luntsolarsystems.com/product/lunt-blocking-filters-b600-b1200-b1800/ Scroll down to the section "Focal Length Suggestions for Imaging Use:". Of course a larger blocking filter is more expensive. Most, if not all, are also available in straight-through version (i.e. not as diagonals). Nicolàs

I think that indeed it is wiser to get a dedicated scope to start with. May I suggest (if you not already have done so) to search this forum and the SolarChat forum for examples of what you want to achieve and choose the make and model based on that? When you go for Lunt and want to do imaging then the pressure tuners are the way to go, as the tilt tuners generate ghost-images. Getting rid of Newton-rings can be done using a camera-tilter or by adding an ADC in the imaging train (I use the latter). A highly recommended read (before buying a scope) is C. Viladrich, e.a., Solar Astronomy: Observing, imaging and studying the Sun, (Saint-Lys, 2021). Nicolàs

Whether or not a full-disc view can be achieved depends not only on the scope, but on the scope/camera combination. I use a Lunt LS80THA, which is 560mm focal length, in combination with a 2x PowerMate and QHY163 mono (same chip as ZWO ASI1600). This set-up gives great full-disc images in H-alpha with room to spare. Easiest way to test this is using Stellarium. Simply define the scopes, cameras and barlows you may want to use and you can test on-screen if that is a suitable combination. But we can do the calculation ourselves: If you know your smallest imaging chip size (the height) and the focal length of the scope/barlow combination, the chip size in arc-minutes follows from 3438 x [chip size in mm] / [focal length in mm]. Examples (solar disc is approximately 31 arc-minutes): LS80THA/QHY163/2x Barlow: focal length = 2 x 560 = 1120mm, chip height = 13.2mm => image height = 3438 x 13.2 / 1120 = 40.52 arc-minutes SkyWatcher Esprit 150ED/ZWO ASI1600: focal length = 1050mm, chip height = 13.2mm => image height = 3438 x 13.2 / 1050 = 43.22 arc-minutes The Esprit150 is of course not a H-Alpha scope, but is only used to show that focal length below 400mm is not required. If you would create a solar scope from it, it would give full-disc images at amazing detail. Your Askar FRA400 has a focal length of 400mm. So if you want to do full-disc imaging, you need a chip at least 32" x 400 / 3438 = 3.7mm height, but then there is no room to play. A ZWO ASI74MM would do (sensor height 7.13mm). From 100mm diameter upwards you will get nice details ('hair') of chromosphere. When using a Quark a cheap achromatic telescope should be just fine as there will be no issues with chromatic aberration (you are only looking at H-alpha). I have no experience with Quarks, so cannot give any further recommendations in that respect. Nicolàs

When you plan to build your own dome, like I did (for automation see here), you can use LesveDomeNet to automate it. Meridian flips are properly dealt with in any imaging software that can handle a dome (e.g. SGP or NINA). However, when you plan to use a side-by-side set-up, you will need to check whether the imaging-software can handle lateral offsets to the imaging scope. I used to use SGP, but that could not handle side-by-side set-ups, nor was that implemented within a year (!) after asking to do so, despite even offering the required algorithm. Another issue with SGP (and perhaps other imaging-software as well) is that it would control the dome during imaging instead of in between integrations (synchronised slewing). As a dome-slew will result in vibrations, that will mess-up your image(s). In the end I felt SGP was a dead end and switched to NINA as that had the lateral offset already implemented. I asked the developer for synchronised dome-slews, which was implemented with a few days. My imaging scope has a GEM-offset of 430mm and a lateral offset of 180mm and never have issues during nightly sessions where the mount does its meridian flip when using NINA. Nicolàs

If I look at the stars in the corners, I see that in the upper two corners the stars are elongated in a direction perpendicular to the centre, while in the lower two it is in direction of the centre. I have drawn red lines in the direction of the elongation: This would indeed indicate a tilt issue, see this thread: When the sensor is too close to the flattener, the stars all point towards the centre. When too far the point in a direction perpendicular to that. In your case the upper half of the sensor is too far, while the lower half is too close. In other words: yes, you have tilt. Is that camera clamped to the filter-wheel? If so, you could improve that by using threaded connection. It could also be that the sensor is not perpendicular in the camera housing. You can check that by rotating the camera 90 or 180 degrees and take another shot. If the elongation stays on the same side, the issue is in the camera housing. HTH, Nicolàs

On 23 June 2022 @ 08:14UTC a large prominence was visible on the Sun's eastern limb. Recording made with Lunt LS80THA, TeleVue 4x PowerMate and QHY163 mono. Post-processing in AutoStakkert!3, PSP and IMPPG. Nicolàs

What you would need for this is a infra-red tracking mount like this SAT/SAGEM Minilir in my collection. These lock-in into the heat of the plane's engines. For filming they were equipped with a camera, making it a cinéthéodolite. Mine is from 1980, not even sure if it still works (probably not, last serviced 25 years ago). Needless to say that these are expensive toys when new, but they may pop-up at militaria auctions (but then they may be defective). Nicolàs

The Sun as imaged on 16 June 2022 @ 08:14 UTC, using a Lunt LS80THA, Televue 2x PowerMate (f/14), ZWO ADC, and QHY163 mono. Keep on clicking to get the full resolution. Nicolàs

Active regions AR3030/AR3032 as imaged with a C11 EdgeHD, ZWO ASI174MM, Baader ND5.0 foil and Baader Continuum filter on 17 June @ 09:10UTC. Nicolàs

This is about what I can achieve with my full aperture C11 EdgeHD (imaged with ASI174MM, 2x Barlow, ND5.0 filter and Baader Continuum filter), but I have to admit that I get this kind of seeing only a few days a month (in this case it was just below 2"). Nicolàs

Another read: https://sci-hub.se/10.1109/JSEN.2017.2732499 Nicolàs

Do I understand this right: this is 30 hours worth of darks? Nicolàs

Good that you found that document as well, thanks for sharing! The first paragraph of the Nobels and Bremer article explains it likewise: Nicolàs

That would me quite interesting! Could you please post your findings here? Nicolàs

Indeed most likely cosmic rays, the following article may be of interest: https://www.astro.rug.nl/~nobels/Characterising_the_cosmic_rays_in_a_CCD_nobels_and_bremer.pdf Nicolàs

I created a full aperture filter from aluminium and Baader ND5.0 foil for my C11 EdgeHD. It gives magnificent views, but only when seeing allows. So, if that is your only scope for solar observing, you may want to have a second filter with a smaller aperture. You will loose some detail, but may still have better views than with full aperture. Nicolàs

I do solar projection on a daily basis (weather permitting) with a 1490mm focal length f/50 Galilean type telescope and found most importantly that the eyepiece is made of metal. It may be useful to check the draw-tube of the focuser, best to have metal there as well. Being a Galilean type telescope I use a home-made plano-concave singlet eyepiece made of an off-the-shelf -75mm focal length, 24mm diameter lens, but have been projecting with Plössls and Kellners as well without issues (apart from the plastic parts melting away). Be careful with demonstrating the projection method, people do tend to dive to the eyepiece to see what is happening there! A safe alternative is the projection funnel. Nicolàs

Hi Pete, I still see it, but you can also try following this link: https://www.dehilster.info/pages/images/sun20220610213004b.gif The animation is quite large (18Mb), so perhaps it is a matter of patience? Nicolàs

Today an aeroplane 'ruined' the shot. Using AutoStakkert!3 (export frames), PIPP (centring and resizing frames to 900×900px), PSP (batch sharpen and colourize), and EzGif.com (animation) I created this animation. Imaging was done with a SkyWatcher Esprit 150ED and ZWO ASI1600MM Pro Cool. Enjoy! Nicolàs