michael.h.f.wilkinson

I briefly had a 4x Powermate for my Solar Spectrum filter. I needed to have a seriously long extension tube in the focuser of my 80 mm F/6 to reach focus, i.e. the focus travel outwards was not nearly enough. This is probably the reason you cannot reach focus. The Baader TZ-4 I have now have requires less. A 4x powermat eon an F/7.5 scope delivers an F/30 light cone, which is perfect for most etalons. I now use a Baader TZ-3 with my F/10 Tri-Band SCT. My ASI174MM is quite happy at that magnification (although it can take faster optics, like F/25). The Baader TZ tele-centrics have an optimal rated back focus, which allows you to set the correct distance between rear element of the tele-centric, and image plane of the camera. Keeping that fixed, you then simply tweak the focuser until you reach focus. The same could be done with the powermate, but I do not know the optimal back focus distance.

Jupiter managed to peep over the trees behind our garden, so I quickly set up the C8, with Siebert Optics 1.3x tele-centric Barlow and ASI183MC camera. This is 1250 out of 5000 frames stacked in AS!3, sharpened in Registax May have pushed sharpening a bit far, will see if I can produce a better result later. Still, chuffed at getting my first Jupiter of the season, and first light on the Siebert Optics tele-centric Barlow

Nice one!

100 mm

It was the 100 mm setting

Took 125 subs of 60 s with my modded Canon EOS 550D, Sigma 50-100mm F/1.8 zoom at full aperture, and Optolong L-eNhance filter on the Vixen GP mount. Quite pleased at the resulting wide field. Stacked the result in APP Full aperture is perhaps a bit optimistic, so I might get that Samyang 135 F/2 after all

Went home a bit early from work to make use of today's clear, if hazy skies. First go in WL, where I noticed FireCapture refused to talk to the new ASI294MM, but did want to talk to the ASI183MM. Not sure why, but the image size might be beyond the capacity of FireCapture. Even with the ASI183MM, I decided to select an ROI around the big AR. Could only stack 200 out of 2000 frames, and I am not quite sure I nailed focus, but here goes: In Ca-K seeing was predictably worse, but I am not too disappointed, and I could stack 500 out of 2000 frames. Grey scale: Pseudo colour: H-alpha was taken with the ASI174MM at F/30, so a small 5-pane mosaic was called for: Grey scale: Pseudo colour: Even an arbitrary piece of solar surface becomes fascinating at this resolution: Clearly, H-alpha comes out best, and I am still waiting for a day with really good seeing, but I am getting the hang of this instrument

Indeed, data is the main thing. Will certainly revisit this winter, weather allowing

Last winter's effort is here: Really needs a lot more work

I only have a bout 5 hours on M78, using my Meade SN-6 6" F/5 Schmidt Newton, and (uncooled) ASI183MC. I hope to use the bigger, cooled ASI294MM-PRO next time round.

Very nice indeed. Not an easy target at all. I really hope to get a lot more on this target next winter

I am not sure these are compression artefacts. I sometimes get these at times of bad seeing. I would in any case start by adding RGB alignment, which does not seem to be switched on. Furthermore, trying various sizes of APs helps, as does reducing the the percentage of images to stack. Sometimes it helps to first process in PIPP, to do an initial alignment of the frames and a coarse selection of the frames to stack

Nice pics! I have just spotted these with the Coronado SolarMax-II 60. Hope to catch them with my bigger scope when I return from work. Hope the health keeps improving

I always keep the original, linear image for that exact reason. I also like the following representation, which uses a heated body colour map direct applied to the linear grey scale. This map is know to represent differences in intensity in a way that corresponds well to perceptual differences in the human visual system, again allowing a larger dynamic range to be represented than the roughly 64 grey levels the eye can distinguish on screen (or 32 on paper). It is frequently used in scientific visualisation in many fields. Science often does need pretty pictures. BTW, strictly speaking this is a pseudo-colour map, not false colour. false colour is when you map different spectral bands to RGB, like in the case of the Hubble palette, or like the IR-R-G image of Saturn I took years back, mainly because seeing in B was so bad I decided to give this false colour representation a go

I notice clear improvements up to 13h of exposure time with my Meade SN6 Schmidt-Newton (6" F/5) and (non-cooled) ASI183MC on M27 using an Optolong L-eNhance filter which gives quite a dark background. I am certainly interested in getting a RASA 8, but as stop-gap will go for a Starizona Night Owl 0.4x reducer on my C8, giving me roughly the same focal length at F/4.

Bit late to this discussion. The key reason to use star calibration is that complete knowledge of the image train cannot be obtained, because part of that train is the atmosphere. Neutralizing the background corrects not just for issues in what we normally consider the optical train and the camera, but also for (variable) light pollution. The degree of moisture or dust in the air changes transmission significantly, in particular in the blue. I remember imaging Ca-K in Estes Park, Colorado on August 20, 2017, and being surprised at the need for sub millisecond exposures. The next day in Glendo, Wyoming, during the eclipse, I needed 3-5 ms expsoures, due to a high haze caused by smoke from distant forest fires. That's a factor of 5-10 on the edge of the visible spectrum. The best way to calibrate any imaging system is by imaging a calibration source, and working from there. Stars with known spectral properties are very handy in that respect. Calibrating ton them helps correct for any colour cast in the optics as well. The other issue I see is that the CIE system works with a "standard observer" model. No human being is such a standard observer, because the spectral sensitivity of the eyes varies dramatically depending on lighting conditions. Proper calibration of the image can certainly maintain the correct ratios of colour components. How the brain interprets these is a matter beyond our control. Another issue is the dynamic-range compression needed. When printing on paper, the dynamic range is at most 30-40 (if you have VERY good quality print, with 2-3% reflection in the darkest areas). Slides, and monitors can handle 10x that dynamic range, but that is still woefully inadequate to show all detail. Non-linear stretching is one way to allow the human eye to see a much larger range of features than the raw data would allow. The other is the use of pseudo colour, which I use in most of my solar images. The first image is straight from the camera, showing detail on the surface, but hardly showing the prominences True colour would look like this Use of a non-linear stretch combined with a heated body colour map brings out hidden detail.

If we assume the fields of view are similar, quite clearly the RASA will be gathering roughly 4x the the number of photons. The 6D will most likely have a lower QE than the ASI2600, which may offset the slight increase in photons per pixel, compared to a camera with smaller pixels. To match the performance of the RASA at 4 hours integration, you would need to nearly quadruple the exposure time on the Esprit.

Not really handles, but certainly handy

My C8 is getting on for 26 years old. Still works like a charm. There are signs of use on the dovetail, but otherwise the scope is fine

Nice capture despite the difficulties. Wall-to-wall clouds here, alas

Very nice indeed. Haven't seen this one before. Might have a shot at that with my Meade SN 6 Schmidt-Newton should the weather finally give me a break

I use firecapture for all planetary, lunar, and solar work. APT only for DSOs. Both work a treat for me

Nice report. Might get a 9 mm to fit between my XW 10 and Delos 8. I always like to have closely spaced EPs in the planetary range to tune the magnification to the seeing

I have taken flats after a session with at least three filters and not seen dust being dislodged in my flats. Not ideal perhaps, but to date it has worked

Had a look yesterday, and it seemed to be a bit fainter, compared to a trio of stars just north of it. Still haven't got me a comparison chart, so cannot put magnitudes on it accurately.