Adreneline

Including the adapter - from the back face of the lens (the m48 adapter) to the sensor - 44 mm plus 1/3 the thickness of your filters. You want the lens to focus within the base of the 'L' - spacing has to be accurate to within 0.1 mm in my experience otherwise the focus position will be well before the 'L' or you won't achieve focus before hitting the end stop of the focus ring. If you look back through this thread you will find several images of members holding digital callipers to show the distance from the back of the lens to the camera body.

Very nice image Steve - nicely framed and very good processing with attention to the detail - where the devil resides! - and noise reduction - not too much. So much to enjoy in this f.o.v. Post-processing is a very personal thing when it comes to colours and colour balance (yours is excellent as per the histogram). Looking at the histogram I might be inclined to pull the black-point in a tad - you certainly have room to do so - doing so will enhance the depth in the image, but again this is a very personal thing. I use HT pretty much exclusively for taking the image non-linear. I use lots or incremental small stretches, each time resetting the black point but not too much or aggressively. I would say I typically apply 15-20 small careful stretches to an image always making sure I introduce minimal clipping, less than %0.001 - maybe a bit more on an RGB image. The depth can also be improved by careful use of LHE - I use settings of 320,1.2,0.5 - 1.2 is an absolute upper limit in my experience. I never use anything like HDRMT to enhance detail/structure - I find it introduces too many other artefacts you don't want! I prefer to use MLT with very small and decreasing bias levels on the first four layers, typically 0.20 - 0.05, with a CIE-L mask so the enhancement only applies to the brightest parts of the image. HTH. It's a great image. Adrian

My experience would suggest adding 1/3 the thickness of the filters; the 135 is really sensitive to spacing. Adrian

Thank you Peter for your generous comment - I'm glad you like it. Adrian

Thank you Tristan; it worked out better than I expected - it's a tricky target. As for becoming a reflector convert - that's a tricky one too! I love the speed but would my OCD let me cope with an open mirror that I can't easily wipe clean when a speck of dust comes wafting along. Ooooo! Adrian

I am posting this purely for interest. I have owned a Samyang 135 for several years and during that time it has been used with ZWO 1600 and 183 cameras. Throughout that time I have gone to great lengths to set the spacing such that the focus point with properly focused stars was within the base of the 'L' on the lens. Last night, for the first time, I used the lens with a Canon 6D camera and thought I would show the focus position when the lens was focused using AF and then checked with a BM. I know there is lots of debate on this thread about the ideal focus position. I should stress this is for my particular lens - I am sure there is variation between lenses. I hope this is of interest. Adrian P.S. The whole setup:

Thank you @tomato, @simmo39 and @The Admiral for your kind comments - I'm glad you like the image. I am happy being in the minority liking starless images. I don't have a problem with stars but if I am imaging a nebula I like to focus on just that and I love these star removal tools. I think the small pixels of the ASI183MM also help and any disadvantage they present due to small size are to some extent offset by the f2.8 of the SharpStar. Thanks again guys. Adrian.

Music to my ears! You can't beat a starless version 🤣 Joking aside, thank you for the kind and generous comments Lee. I thought you'd pick me up on the 'green' - rest assured I am not a changed man - this is an exception 😆 I am pleased with the way it has worked out though - APP doing its magic again joining the panes together. Glad you like it. Adrian

This is 60 x 300s of SHO taken with a SharpStar 13028HNT + ASI183MM and 6 nm Astronomik filters. I don't usually like any green in my images but for some strange reason it seems to work in this particular case - for me at least. Pre-processed in APP. Post-processed in PI. Keeping Propus and Tejat Posterior under control is a real challenge so here's a starless version; I understand P & TP are no where near the nebula itself. Thanks for looking. Adrian

That is my preference - with either the long or short side of the sensor perpendicular to the mounting bar. Having invested so much time in ensuring there was no droop or misalignment between camera/filter-wheel/lens I decided that introducing a camera rotation system was asking for trouble - assuming of course there is space to fit such a device and maintain the critical back focus spacing.

That's me! If I go to bed I can't sleep anyway! The last two nights have been very rewarding here. I could have imaged longer last night but I was imaging IC443 and it was down at about 40 degrees by 02.00 so I decided enough was enough. There was frost on the gear when I brought it all inside but no fogging on the mirrors. Same the previous night with NGC281 - except I got off to a bad start with spacing issues that needed sorting. This image is the first one with the ASI183 on the SharpStar and spacing is so critical! I needed 55.3 mm to accommodate the Astronomik filters and I put it out with 55.1 mm hinking it might be okay. It wasn't! So I fiddled around for ages getting to 55.3 (55.28 according to my digital caliber) and I think these stars are okay. What a game in freezing temperatures! Why do we do it!? Glad you like the image Steve. I will get more data at some stage but I am still at the stage of wanting to point the SS at all manner of stuff just to see what it does 🤣 Adrian

Hi Everyone, This one really deserves more time and may get so if the clear spells hold up for another night or two. As it stands it is 10x300s of Ha, OIII and SII taken with an ASI183 on a SharpStar 13028HNT astro-graph, using Astronomik 6nm filters. Pre--processed in APP and post-processed in PI; presented with and without stars. Thanks for looking. Adrian

Thank you Dave. No, not tried that - thanks for the tip - I'll give it a go. Also worth a try - thank you. Adrian

Thank you - glad you like it. Thanks for the prompt regarding SiriL - I’ll give it a go. Adrian

Thank you Peter. The SS has certainly teased out some detail. Adrian

Haha! ... and nice optics in the SharpStar also play a part. It's a joy of a scope to use - if only I could figure out why it won't register I could have a whole load of fun with some of my old RedCat data. Glad you like it Adam. Adrian

I imaged IC1805 in late November 2022 using a RedCat 51 and 6 nm Astronomik 1.25" filters. I have since been entrusted with a SharpStar 13028HNT f2.8 astrograph from a fellow SGL'er so I revisited IC1805 with a 2" Astronomik Ha filter and combined the new Ha data with the previous OIII and SII data. For whatever reason (still to be determined) PI refused all attempts to register the SS and RedCat data; in the end I managed to get APP to register everything with the Ha as the reference, and this is the end result. Post-processing in PI. Thanks for looking. Adrian

"A short stack of subs" or not this is a great end result and definitely worth sharing. Just goes to show what can be done with minimal data and careful and considerate processing. NGC2158 steals the show for me. Adrian

That is an outstanding image Adam. Great subtlety of processing has revealed an intriguing object in perfect balance with the background star field. Star shapes and colours are excellent across the whole field of view - your twin scopes are doing an amazing job. As you’ve rightly pointed out, patience is the name of the game in AP! Glad to hear you’ve crossed the rubicon with PI too - patience and persistence pays off in every aspect and it shows in this fantastic image. Thanks for sharing. Adrian

I'm afraid that "designed by monkeys" and "... PixInsight ... a barbaric environment of tyrants fresh from the Spanish Inquisition" don't amount to compliments in my book. I have now used BlurX on a number of my images and have been impressed by the early results, all the more so since using PSFImage (a PI script) to obtain a value for the PSF. As with all these processes and scripts it is taking care to ensure you are not taking more from the data/hardware combination than it has to give. Adrian

I'm really not sure @ollypenrice and @Magnum that that all these insinuations and name calling are helpful, and I speak as someone who has been banned from the PI forum for comparing one script within PI with APP. I am disappointed, but not surprised, a Moderator has not stepped in and made comment. You may be employing the use of emojis to imply jokes but the jokes are in poor taste. As for cost comparisons in my case PI represents less that 5% of my total outlay and in my opinion that small cost has been recouped many times over. This is a hobby and as such to be enjoyed because it enriches our lives. If you cannot rise above the differences and use PI, PS or whatever you care for to your own benefit and hence the benefit of all without resorting to name calling and insults then perhaps you should find another hobby. Keep this thread on the subject of BlurX and not a debate about PI vs. PS. Adrian

I had the same problem. I use a 24W heating pad (for cats) strapped to the mount before placing the cover; it’s on for 2 hours and then off for 2 hours. The mount stays dry - no sign of moisture or condensation.

Thanks Lee for your very generous comments but above all thanks for the data and thanks for the invaluable critique whilst I arrived at the final image. What you see is in no small part due to you. Thank you Michael. I am always concerned about overstretching the data but also aware that many prefer the more saturated approach to processing - I am not one of them. Thank you Adam. Really clear nights - with minimal/no Moon - are so few in the UK and getting sufficient data to complete an image can be very frustrating. Because my equipment and Lee's have so much in common it makes sense to share, otherwise you can end up with insufficient data to get anything at the end of the season. Thank you @Sunshine - I agree it is a tough one. I tend to feel that if I am imaging a nebula then that is what I want to see as clearly as possible and in my opinion that is best achieved with the stars removed. I recognise many, maybe even most, like to see the stars in the image so I've done both and processed the stars as carefully as I can, but not at the expense of the IC1396 and other nebula in the image. Thank you to one and all for your comments. Adrian

This is another collaborative image with @geeklee This is my first image with my new 3nm Antlia NB filters - Ha and OIII so far - and was going to be a HOO image. Lee offered me some of his data taken with his RedCat51 + ASI294MM and in particular some SII data to allow me to put together a SHO image - my preferred option. This is 33x300s 3nm Ha + 25x300s 3nm OIII from my RedCat51+ASI1600MM, and, 26x300s 3.5nmHa + 24x300s 4nm OIII + 24x300s 4nm SII from Lee's RedCat51+ASI294MM. In total the above equates to 11 hours of data. Calibrated, registered and integrated in APP and post-processed in PI. This was processed as starless and stars separately before combining in PixelMath. The normal processing in PI using NoiseX and StarX along with the usual PI processes. BlurX was also applied in the linear stage using the PSFImage script in PI to set the PSF value in BlurX. I know it is customary to have the trunk at the bottom but I quite like to see the dancing dervish down there. Thanks to Lee for all his comments and critique in arriving at the finished image. Thanks for looking. Adrian & Lee