Ags

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

Here is my lucky M57 with some adjustments to the process following the feedback on this thread. I ditched drizzle after doing a side-by-side comparison: it only added noise not resolution (except maybe on the stars inside the ring). I also changed to 400 ms frames - 500 ms was too much for my mount but I could do better than 333 ms. At 400 ms I was able to retain 65% of the frames. I processed as 12 bit in AS!3 using the Global setting and Noise Robust 8. I also increased sub time to 3 minutes and got away with no field rotation. Maybe I could go for 4 minutes? Is there an online field rotation calculator? Work night so I only shot 10 subs and a dark sequence. No flats because I am only able to shoot antiflats - I apply them and the image less flat than before. Quick stretch in Gimp and some sharpening on the nebula. I will add a few more nights to this if I can. But I have a new 6.3 reducer to play with and this is not the target for it I think. My initial issue was stacking the faint stars and looking across the field I think all the stars are coming out ok.

Never tried the Pan but I have no complaints about my ES 24/68. Well... They should have purged it with Helium not Argon to save some weight!

I got a second-hand Celestron 6.3 Reducifier in the post today, securely wrapped in bubble wrap and ample orange tape. Looking forward to trying this out for photography and visual.

I am having fun imaging DSOs using "lucky imaging" or more accurately "lucky tracking" techniques, but I am limited by the fact my AZ-GTi is in AZ mode. I would like to switch to EQ aligment but I have a few questions. By the way, I plan to keep the mount in AZ mode, just aligned for the north pole - I had a few issues with the EQ alignment last time i tried it. Firstly, my load is about 4 kgs including an uncooled planetary camera, sometimes a filter wheel and a C6 with RDF. Can the AZ-GTi take that kind of load (albeit counterbalanced) with its AZ gears tilted 50 degrees? Secondly, what is the bestest cheapest wedge to get for the AZ-GTi? My tripod has a 3/8 photo thread, as does the GTi. I hear that the Star Adventurer wedge is not compatible as one of its knobs collides with the GTi AZ clutch? Would the Ioptron wedge be a better choice?

Looked at the Starlight Express one - 3 updates per second on M57 in their example. Apparently that is 50x slower than actual seeing jitter. Just do lucky imaging with 333 ms frames and get the same benefit in software for free?

Yes - tried it once with my 17 mm - I didn't like the view at all. The view with one, two or the FTRs was excellent however. I would go for the Explore Scientific line these days as the Hyperions are only good in slow scopes.

Having used the FTRs (I had the Hyperion 17, the rings giving 13, 11 and 9) and I wouldn't change rings in a session, I would set the EP to what I wanted for the whole evening. They are a bit of a fiddle in the dark.

I like to think I have some nice mid range eyepieces, but when I go out imaging, the alignment eyepiece I bring with me is a humble Super 25. I don't need anything better to align the scope and center the targets, and the Super is light and cheap. But... I really enjoy using it. The crude build of the eyepiece reminds me of the simple eyepieces I had as a kid, and the rudimentary narrowfield views it provides are equally nostalgic. Maybe I should get some plossls... Do you have any eyepieces you hang on to despite having better options in the bag?

Depending on the paint, you might still need an IR-block filter.

For a second I thought you were talking about someone's new CCD!