wimvb

By PhotoShop, merge mode additive. A very solid connection comprised of several layers. They don’t??? 🫣

@almcl With perfect collimation, if you defocus, the central spike of the 11 and 1 o'clock patterns move towards each other, and the 3 o'clock central spike moves up. The 5, 7 and 9 o'clock patterns are the same as those that differ by 6 hours (opposite of the central star). If the 3 o'clock spike moves up, so does the 9 o'clock spike. A tri Bahtinov mask produces three ordinary Bahtinov patterns. The idea is that with miscollimation, the three patterns are focused at different focuser positions. Collimation equalises the focus positions. It's like a three legged stool, where you want the seat to be absolutely level. What I found in my second test was that I could move focus position quite a distance before I could see a clear shifting of the central spike. That is why I questioned its applicability. Otoh, it may very well be that the coupler between the focus motor and the focuser shaft has come loose during the winter, causing some play in the focuser. The large temperature fluctuations that we've experienced during winter, can do that. I just put my gear in summer storage until mid August (no astro darkness left after the coming full moon), but I plan to do some more tests when I set up again. I will have to check collimation then anyway, so I will be doing a side by side comparison (barlowed laser/cheshire vs tri-Bahtinov mask) then.

Thank you, Lee. I got the idea from Seti Astro on youtube. I didn't remember the exact steps, so I "winged it". Normally I would emphasize the H-alpha regions a bit more, but this time I went for subtle.

So the ASIAIR doesn't accept any other focusers than ZWO's own?

A while ago, I designed a tri-Bahtinov mask to aid in the collimation of my Mak-Newt. I even cnc-ed the secions of the mask. Since my cnc machine is limited to a 30 x 18 cm work area, and the telescope has a 20 cm tube, I had to make 3 sections of the mask. Before I had an opportunity to assemble the sections, other things got in the way, and I forgot all about it. (I wasn't happy with the final outcome, so forgetting was quite easy, and age helps.) A week or so ago, I came across the sections and finally glued them together. On a partially clear night, I put the mask on my MN190 and tested on Arcturus. For the first test, I only did a coarse focus and took RGB images. For the second test, I focused better and took an image with the L filter in place. Here are the results. When I did the second test, I found the mask not that sensitive to defocus, so I wonder how sensitive it will be as a collimation tool. Does anyone here have experience of using such a mask for collimation? Here is my design. Each third of the mask holds one section of the three zones, as described in this link. The mask is cnc-ed from 2 mm black acrylic. The slots are 4 mm wide and spaced 4 mm. The sections are glued together with epoxy (butt jointed). I have since designed supports to make the joints more stable, but haven't yet cut those. https://satakagi.github.io/tribahtinovWebApps/reports/improveSensitivity.html

Since astro darkness is all but gone up here, the moon is gaining, and clouds are obscuring it all, I have started to reprocess data from a few years back. Inspired by deep images posted here and in the deep field challenge, I've reworked my 2022 version of M51. This is 15 hours of data, captured at f/5.3 with my SkyWatcher MN190 and ASI294MM camera. Reprocessed, as always, in PixInsight. For H-alpha and red combination, I tried something new. I created an HaRR image with channel combination in PI, and colour calibrated that with the standard colour calibration process. Then I merged the red channel of this image with an RGB image. It took a bit of tweaking, but the result looks pleasing. The original version, which was all about the Ha regions in this galaxy, is here:

Unfortunately, StarXTerminator doesn’t eliminate just stars.

@ollypenrice There's a very thin "string of rubies" coming in from the right edge in your image. It's different in your two versions. Is this real signal, or maybe an artefact?

That's definitely more than "one drop". Very nice image.

Unless the telly is an antique, it may be easier to take it out to the scope. Not completely unrelated; many years ago a colleague built his own large format camera around the lense from an airplane surveillance camera, a really massive piece of glass. The camera was so heavy that he mounted it on a truck to do nature photography. When he told me that, he sighed that it would be easier to keep the camera indoors, and take nature to the camera. More related: a street light, even with t-shirts isn't good for flats. A street light is more of a point source than a flat surface.

There is a limit to that, set by your sky darkness. Going past some 22+ Mag/arcsec2 just isn’t feasible. But yours is an excellent image as is.

No need for an OCAL, in my opinion. A cheshire for the secondary, and a barlowed laser (I use the cheap one that came with my scope), is all you need.

Courtesy of my computer screen. It shows even the smallest irregularities even when my Galaxy Tab just shows pitch black.

Yes, It shows better in the image you posted on AstroBin, as does the red in the background.

Amazingly deep image, Olly. On my screen I definitely see a faint red background towards the right. (But also a very blue star, so can it be colour saturation?)

Holmberg IX, right next to M81, is an irregular sattelite galaxy, similar to the LMC. Many galaxies have sattelite galaxies. They are the remainders of past accretion events. https://www.sciencenews.org/article/dwarf-galaxy-m81-astronomy-space

What you see around the single star is the diffraction caused by the mirror clips. To get rid of this, you'll need a mirror mask, a ring which you attach on top of the clips, and which covers them. This will decrease the effective aperture by about a cm, but that isn't necessarily a bad thing. You can 3D print your own mask, or buy one. https://www.firstlightoptics.com/misc/backyard-universe-primary-mirror-mask-for-sky-watcher-250mm-newtonian-telescopes.html Regarding the need to collimate, the Quattro is a fast newtonian where the secondary mirror is offset. This may mean that the secondary mirror holder is offset. If so, the out of focus doughnut will not be symmetrical. Another Quattro owner should be able to clarify this. (The alternative is that the holder is mounted symmetrically, but the mirror is offset on its holder.)

A small section of the Coma Cluster of galaxies. This is 5 hours of RGB data on this galaxy-rich part of the night sky, captured with my MN190 and ASI294MM camera, and processed in Pixinsight. Captured during two clear nights April 11 and April 12. For the annotated version I used the ngc/ic (pink), LEDA (blue), and GMP (yellow) catalogues. GMP is a compilation of 6724 galaxies in the Coma cluster, published by Godwin, Metcalfe and Peach in 1983. Apparently, this catalogue only goes up to DEC 29o 16' Some of the most distant galaxies in this image are more than 2 billion light years away from us. I targeted this area because of the interacting galaxies ngc 4922 in the upper part of the image. The tidal stream was just about visible in the captured data.

You forgot one thing. The future 'Alexa' will be customisable. Mine will say, with that typical Dirty Harry voice (yes, I'm old enough to remember that): "D'you feel lucky, punk? It sure looks mighty cloudy from where I stand."

That's a very nice image. The only problem I see with it, and that touches on the problem with bought data, is that it lacks Ha. I haven't seen any other image of this target, but the blue arms with all their knots just scream H-alpha. And since this is from a bought set, where others have decided what to capture, you'll probably never get it. When we capture our own data, we get to decide the what and how.

Live fast, die young, that's my motto.

I run Ekos (StellarMate) off a 64 GB micro SD card which holds everything I need. For my 1 m fl scope and ASI294, I have all the index files down to 5.6 arc minutes (fov 66 x 45 arc minutes). Using the internal solver and off the micro SD card, plate solving is reliable and fast, the fist solve usually within a second or two, and next solves take about a second or less. But I do need to clear the mount model (in the mount tab of Ekos) about twice per imaging season. The last time I had poor solving performance, was when I used the ASI 174MM as imaging camera. This camera has a much smaller sensor (and larger pixels), giving a fov close to 0.5 degrees. I believe that fov does matter for the plate solving performance, especially when doing polar alignment. Btw, powered (USB) hubs can be a problem. People who use them seem to prefer industry grade hubs, and not ordinary home/office hubs.

Which index files do you have loaded? The recommendation is to go down to 10% of the fov, but if you have the space for it, it doesn't hurt to go lower. For me, that has been one of the causes for poor platesolving. Other causes for general poor performance are low power and poor wifi connection (I now only use my Pi with an ethernet cable).

Thank you, guys. Much appreciated.

This target needs no introduction. The image is a collaboration with @Firas. He collected the data with his ONTC 8" telescope and Moravian G2-8300 CCD camera, and did the preprocessing. I processed the masters. data: RGB: 50 + 30 + 20, 180 s exposures (5 hours total) L: 171 180 s exposures (8.5 hours) Processed in PixInsight. The RGB data was a bit thin, but the XT-suite made it manageable.