Ags

It's always night in space 😃

I think maybe my problem is i am not checking "mormalize stack" so perhaps the floating point values gt collapsed back to the same integer scale. I will try repeat the above image with "normalize stack" set to 75%. BTW, there is definitely no 32-bit option or "scientific stack" option in AS!3. I assume it just uses 32 bit precision all the time?

Did I miss another setting in AS!3? I don't seem to be able to sum, I can only increase SNR.

Don't blame the eyepiece, it was made for an age of long refractors. Get a cheap F13 four inch mak for it and enjoy the views 🙂

My signal is skimming the bottom of the histogram - if a pixel has a value of 5 or 6 in individual stacks, then after combining them I am still only left with 5 or 6. But if I increase the gain so the same signal gives a pixel value of 10 or 12, then after combining all the sequences I should have 10, 11, or 12, more closely reflecting the average of the sequences?

I am not able to get down to 100 ms frames. I am looking at an F4 reducer lens suggested on another thread by @vlaiv, which would get me closer the 10 Hz frontier. https://starizona.com/store/night-owl-4x-sct-reducer-corrector I stacked this image with a low frame rejection rate (80% of frames accepted into the stack), so I wonder if I reduced that to 50% or less I would get more detail in the core and tighter stars in general. The trouble is noise would go up... Another thought is to increase gain from from 310 to 360 on my ASI 178 - the theory is this will spread the weak signal so I will end up with a richer spread of levels after stacking.

Lots of mentions of various 25 mm Plossls. My 25 mm Celestron E-Lux plossl is the one eyepiece I really regret selling.

Just to write a happy ending to this thread, I got darks working, and also found that lucky imaging / lucky tracking works much better at F6.3 than at F10!

Here is a new version reprocessed from scratch without using the AS!3 banding removal feature.

The wider fields and ability to reach larger exit pupils are useful of course, but I want to emphasize I am seeing significant benefit at high mags too. Performance on doubles has been transformed by the reducer. Another consideration is weight - I don't want to be using enormous eyepieces or mixing barrel sizes.

I found the problem with my darks. I was applying darks and also removing horizontal banding in AS!3. Turns out the AS!3 horizontal banding feature results in a very slight gradient.

Thanks. Initially I was making the mistake of thinking I would get a brighter image by binning, it took a while to realize the image would stay the same brightness but with a bit less noise. A major reason to bin is the size of my hard drive - the above image is 80GB of SER files! I only have 150GB free space. In another question, does flooding an SSD with data every week reduce its lifespan?

On the subject of binning, does it ever make sense to bin? Why not capture at full resolution and then do more sophisticated stacking of pixels. You can downsample at the end. Binning seems to force small stacks of 4 subs (assuming 2x2 binning) which can't be great mathematically...? I had to bin at F10 because the signal was so attenuated... but in general am I right in thinking that binning is best avoided if at all possible?

I would describe them as "recently annoyed"... 😀

I believe the blue stars in the cluster are not younger but instead are recent mergers of ancient stars.

This is my latest attempt at lucky imaging (or lucky tracking) with my C6 and AZ-GTi. This is 48 one-minute sequences of 400 millisecond frames. Compared to previous efforts I have added a 6.3 reducer and changed from 2x2 binning to no binning. Each sequence is processed in AS!3, the the TIFs from each sequence is stacked in DSS, and finished in Gimp. I retained 80% of the frames in each sequence, not only was the night calm and windless, but also the reduced focal length made a big difference I expect. I think the principle of this approach to imaging works, but I need to resolve the problems I have with darks and flats - the flats don't flatten and the darks leave traces of amp glow. Also processing is too laborious - I would like to shoot longer sequences than one minute so need to get a wedge and shoot in equatorial mode.

Processing my data from last night - normally AS!3 gives a quality graph with barely a quarter of the data over the 50% line, but last night's data is 90% over the 80% level! I think quality only dropped at the times when I recentered M13.

You have tried a lot of eyepieces and speak of this cheap zoom so highly I am tempted to get one... This is the same thing, correct? https://www.firstlightoptics.com/ovl-eyepieces/hyperflex-72mm-215mm-eyepiece.html

I picked up a second hand 6.3 reducer/corrector for a very reasonable price and just came in from my first night out with it. Seeing was exceptional (in some directions, not in the direction of Tower Block C that looms to my south). I started out visual using my ES 24/68 and ES 6.7 eyepieces, with an achro Revelation barlow making a guest appearance. I had a shock when aligning on Arcturus - the star was massively distorted! But I soon realized it was just the 24/68 was misaligned in my cheap diagonal. Second alignment star and first target was Polaris. I have been having some trouble with doubles with my C6 - the star images have been looking a bit untidy making doubles unsatisfying. Polaris A looked a lot cleaner in the 24/68 but I could not split it at that magnification - it normally splits with this eyepiece when there is no reducer in the image train. I switched to the 6.7 mm EP and the view was delightful - a clean and round Airey disc with clear diffraction rings and the faint companion nicely resolved. The view was very similar to the clean and satisfying images I usually see in my Maksutovs. I added the barlow for 280x magnification, and the view held up nicely except for the chromatism of the barlow. Next stop was Izar. This has always been a difficult split with the C6. Once again the view with the 6.3 reducer was cleaner and more pleasing at 140x and 280x and the split was easy and the fainter companion much more prominent. Izar was in the vapor trail of Tower Block C so conditions were not favorable, but the scope, reducer and eyepiece performed well. Next on to M3 - goto was slightly off but now my C6 is a widefield scope so the globular was easily located and centered! The view was OK, a tie with similar views without reducer. By the way I am comparing (by memory of course) the view on no-reducer with a 10 mm eyepiece and with-reducer and 6.7 mm eyepiece - so very similar magnifications and the same 82 degree fields. M13 was next and I felt I got a particularly good view tonight, with stars resolved right across the cluster at 140x. Not sure if the improved and tighter star images the reducer/corrector is providing just helps me tease out those faint stars at the limit of my scope's light gathering abilities? Switch to my camera and started shooting M13 - so much easier with a wider field. I don't have to keep correcting for drift every 30 seconds, the stars are more point-like, so much brighter on the pixels they do hit - and with less focal length the AZ GTi doesn't micro-wander nearly as much. Unlike imaging at F10, I could now image without binning. I kept shooting until my laptop ran out of space (which doesn't take a lot of shooting). Currently AS3! is refusing to process the gigantic video files, but I will sort that out in the morning. I absolutely agree! It's funny how two people can look through the same equipment and see polar opposites. I feel the difference with my scope is like night and day 😀

Those CN threads seem to suggest the 5.5 would work for me.

Not so relevant, but I once made a little program to model diffraction patterns using the Huygens-Fresnel principle, high school maths and Java. No Fourier transforms, just brute force programming... as I increase the number of samples the pattern evolves like this:

But if we are talking about an airy disk / diffraction pattern, we should stick to treating the photons as waves right?

I am thinking about picking up a few cheaper and lighter eyepieices to fill out my collection - in particular looking at the ES 5.5 mm 62 degree, which i would use in F6 scopes for higher magnifications - mostly for looking at doubles, the Moon and planets. Has anyone used this EP? Also thinking about picking up the 14, 20 and 26 mm in the same range.

How can you talk about how "bright" something is without talking about how you are measuring it? If you are not measuring it (either with an eye or a camera) it doesn't make a difference...

@nicoscy I don't think the GTi would be able to guide 1500mm focal length. I am going the opposite route and stacking thousands of millisecond subs. I have seen the TS wedge and it is way too ugly. No way that thing goes on top of my Berlebach! The WO one looks nice but way too much money. Guess I will have to go for the SkyWatcher one. Maybe if I add this I won't need to change the huge knob as it looks like it would add a bit of clearance? https://www.teleskop-express.de/shop/product_info.php/language/en/info/p11371_Artesky-Polsucher-Adapter-fuer-Skywatcher-AZGTI-Montierung.html