Ags

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!

Rural location matters because that determines how bright your sky background is. The contrast technique people are talking about on this thread works by attenuating the sky background but as yours is already dark I don't know if you will see the effect. M13 is a star cluster - I am talking about reolving the individual stars in M13, which is possible for scopes of 4 inches aperture and up, roughly. Technically, the greater magnification will attenuate the fuzzy glow of M13 itself, so I will stick my neck out and say that you should resolve more stars at high mag in M13 from your location.

Of course I understand that as do most other observers. But (unless you are at a very dark sky site) you will only see stars at the limiting magnitude at high magnification, and definitely not at such low magnification that exit pupil exceeds eye pupil. M13 is easily visible at the moment. Why not look at it with an eyepiece giving a 7mm exit pupil and one giving a 1 mm exit pupil and see which resolves more stars in the cluster? I am assuming you are in an urban/suburban location.

There is no other light to cause "increased brightness". The image you see in the eye is described fully by the light in the exit pupil. So if the exit pupil is larger than they eye pupil due to low magnification, the star is dimmer. It is astronomy 101 that you use high magnification to resolve faint stars in star clusters. This is a technique used by most observers. Who is wrong - your theory or all those observers?

Here is my latest version of M57 - 17 2 minute sequences of 240 frames (frame length being 500 ms clearly). I kept 40% of the frames. I think (after a bit of sharpening to see what's there) I am starting to pick out some detail in the nebula. Still very noisy but I think I can add to this. Also need to work on not overexposing the stars - this happens when i linear stretch the data for DSS (otherwise the stars are too faint to register). I think I can improve here though. @vlaiv - no drizzle in this version.

Have you tried? Don't knock it till you've tried it! 😂

Yes I figured out i need to use Global. I see Emil Kraaikamp uses frames of 1 second and still calls his results lucky imaging. I would go longer than 1/3 or 1/2 second, but the limiting factor is for me is tracking not seeing. The 6.3 reducer should let me add a few more milliseconds. Why won't my drizzle trick work?

I was just regretting selling that AZ3...!

Yes AZ mode - that is what limits my sequences to a couple of minutes. With a wedge I could be shooting 10 minute subs. Actually I could shoot subs of any length I liked - 1 hour would not be an issue, except for the fact I have to watch the screen and keep the target on the crosshairs! Maybe tracking will be better in EQ mode though...? My main issue with tracking is the ALT slips a gear tooth every minute - I guess in EQ mode my buggy ALT gear wouldn't be spinning so no problem.