Adreneline

They are just the standard version - not the MaxFR ones.

I've recently imaged NGC7000 with my SY135+ASI183MM - 300s subs using Astronomik 6nm filters and this is a comparison for you with one single sub from each session: Difficult to tell but you do seem to have a little less O and S compared with H (and with my filters). My H and S focus in almost the same position - O is a little different but not that much. I also image at ~f2.6 using a 49mm sdr - gain was 111 and temp was -20 degrees. "This Samyang 135 is driving me crazy, specially due to bakcfocus and tilt problems, so adding one more issue is tempting me to sell it and buy a proper scope " It took a while to get mine up and running properly and a lot of patience with assembling and disassembling to get spacing and tilt issues sorted - it was worth it in the end. As for buying a proper scope - my experience of so-called 'proper scopes' has not been that great. Adrian

Well in my opinion it would be. Good luck!

Hi Mike. Sounds like a good plan - I have no experience of the Poseidon camera so cannot offer any advice. Finding the correct spacing with the SY135 is all about well informed trial and error - and patience! Hopefully a Poseidon user will pop up and offer some first hand help. Good luck.

Just for the record I use the AstroJolo adapter which provides an M42 thread rather than M48; not sure it is still available but this is a possible alternative. The ZWO 1.25" EFW has an M42 thread either side and I prefer to have the EFW right up against the camera although I do use a shim at this interface to ensure I can achieve a 'landscape' orientation for my camera sensor. Adrian

An excellent idea. I used my 6D+SY135 in January but never got around to looking at the subs I took of M42 - they are still residing on my old ASIair Original - 20s, 40s and 60s subs - 86 of them! I've just loaded one of the 40s subs into Siril to look at the tilt - if any - and this is the result: The same analysis from ASTAP: This all looks very good but close inspection of the subs might suggest the lens is very slightly too close to the sensor: All of this does make me think I still have a tiny amount of tilt in my SY135+ASI183 image train I have found in the past that not all M42 extension tubes are "perfect". Hope this is of interest. Adrian

Is that also the case when you use the lens on a Canon dslr?

Hi Pete, In my opinion this is essential. I used my SY135 with my Canon 6D in January this year and took a photo of the focus position after using the autofocus routine in the ASIair and checking with a BM, this was the result: No two lens are identical, no two cameras are identical. The back focus of the cameras themselves is subject to a manufacturing tolerance so in the case of a ZWO camera you cannot be sure it is spot on 6.5mm. I fail to understand how some people state the definitive spacing is 44mm (say) for the SY135 when used with a ZWO camera. Filter thickness will have affect the spacing. I use 1mm Astronomik filters so in theory they affect the spacing by ~0.33mm. Haha! You would like to think so! Again, this is my opinion only, but the SY135 is a consumer dslr lens not a dedicated astrograph. If you are lucky it will be a good one. (I recently bought a dedicated astrograph lens which had been tested prior to despatch but it still didn't perform as one would expect; I am awaiting a replacement). Well mine is! I guess it comes down to the quality of the flats. This is my current setup - I've been through so many iterations and variations I've lost count. I am sure there is no misalignment or droop and the NB filters I use focus in the middle of the 'L' and I still have a slightly dodgy corner. It is what it is and I am happy HTH Adrian P.S. I am also a firm believer in using a step-down-ring and not using the aperture control on the lens. I use a 49mm sdr so the lens operates at about f2.6 and you don't get facets around the stars.

Can I ask what spacing you have between the back face of the lens and the front face of the 2600MM? I noticed in an earlier thread (M42 et al) that you mentioned introducing an additional 0.5 mm shim/spacer. My experience of using this lens is that introducing (or removing) a 0.1 mm shim is often too much and will give rise to a significant change in (a) focus position and (b) star shapes. I have three or four ~0.1 mm shims along with ~0.2 and 0.5 so I can get step values between 0.1 and 0.5 when fine tuning. Spacing and alignment are so critical with this lens. I've owned mine for more than three years and I still can't get it perfect in one corner despite trying numerous mounting arrangements to try to ensure the alignment is perfect and the spacing is as close as I can get to within the base of the 'L'. I am a firm believer that the focus mark should be within the base of the 'L' when focussed on a star field. I have used a Canon 6D on my lens and it focus almost dead central in the 'L' base. @Uranium235 has suggested introducing 0.01 mm shims/wedges to correct the final issues I am having but I for one don't want to go that far - it is what it is and once BlurX has worked its magic viewing at 1:1 the stars look fine to me. In my case I am convinced it is either a lens or alignment problem as the problem persists even if I swap from using my ASI183 to an ASI1600. I now use two PrimaLuce Labs 80mm rings to support the camera (a perfect fit) and the lens (a perfect fit if I remove the padding) and if an error exists it is less than 0.1 degree (relative to a reference flat surface) - see image above in this topic thread. You also mention using the lens at f4. I use mine at ~f2.6 achieved by using a 49 mm step-down-ring which gives much cleaner star shapes than using the in-built aperture control in the lens. There are Askar alternatives at 135, 180 and 200 mm f.l. HTH

Very nice - GCs are such a challenge!

I've had my RedCat 30 months now and I love it - it's a "keeper" for me 👍 Phil

I really like the depth you have achieved in the galaxy, and all the better for the bonus SN. Adrian

Thanks for the detailed response Rob. I'm not sure I want to start playing with 0.01mm shims to correct such a tiny amount of tilt - I know the devil is in the detail and it would be nice to think it was perfect but .... I've looked at screw tilt adjusters in the past and came to the conclusion I could spend numerous imaging sessions chasing my tiny amount of tilt and not do any imaging! Let me/us know if ever you produce your shim design! Thanks again. Adrian

Just for completeness this is the rc1600 data (standalone) processed as close as I can to the SY183 and combined rc1600+SY183 data. Adrian

Thought I would add the Samyang 135+ASI183MM component of the above image - processed as close to the original as I can get - for comparison, if anyone is interested. Adrian

... if for no other reason than to keep your hand in with processing

The lack of astro-dark is a problem and the short time window just compounds the challenge. Two near identical rigs helps - when they are both singing along nicely! I've tried doing Ha and SII on the RedCat and OIII on the Samyang but the result doesn't seem as good as the method I adopted above. No Moon and Bortle 3 round here does help. I am hoping to replace the Samyang 135 with an Askar 180 + ASI183 which gives a near identical f.o.v. to the RedCat + ASI1600 - just waiting for stock to arrive. The ups and downs and highs and lows of AP always reminds me of A Tale of Two Cities, “It was the best of times, it was the worst of times, ...... , it was the season of light, it was the season of darkness, it was the spring of hope, it was the winter of despair.” Since taking up this hobby I've now had seven winters of despair! 🤣

Despite the lack of astro-darkness it is still pretty dark in this neck of the woods so I decided to try combining data from a Samyang 135 + ASI183MM (6nm filters) with a RedCat 51 + ASI1600MM (3nm filters). The image comprises 12 x 300s of S, H and O from both rigs amounting to 6 hours of data from one night. Pre-processed in APP and post-processed in PI. Following cropping to remove the Samyang only region I used BlurX and NoiseX followed by StarX on a duplicate of the linear image. Each component was then subjected to careful incremental Histogram Transformation before combining with PixelMath as straight SHO. SCNR to remove the green and magenta (I don't like either!) followed by a slight saturation boost in Curves Transformation (which I am not sure it really needed). The originals were treated to a dose of EZ Soft Stretch before extracting the stars, de-stretching them in HT, and recombining with the starless image using PixelMath. Thanks for looking. Adrian

Interesting. It is not just a SY135 problem that's for sure. I know in my case it is not a sensor problem because I have used the ASI183 with a RedCat and an Askar 180 and the corner stars are consistent in all corners. All the image train is screw-tight rigid and I have even tried different spacer rings but the problem persists. DynamicCrop sorts it 😆

I envy you your lens corner performance. My SY135 has a dodgy corner as seen in this raw, linear, unprocessed sub - it's no big deal but nevertheless it is frustrating. I am convinced there is no droop or misalignment of any kind in my mounting arrangement and nothing I do changes the situation. Once BlurX has done its magic and I've cropped off the edges it does not detract from the overall image. I still think that for a consumer camera lens it out performs many so called astrographs.

No astro-darkness and just 10 x 300s of S, H and O but it's not turned out too bad considering the lack of data. Sadr is such a challenge to process - it's determined to steal the show. Using the latest incarnation/variation of my SY183 setup + 6nm filters. Will it ever stop evolving?

Thank you Pete. I was caught unawares on Monday when I saw it, and made a complete hash of trying to record the event - but so pleased that I (and the good lady) had actually managed to see it at all. When I got a second chance I thought I'd best get my act together. I've never knowingly seen Mercury (other than the transit a few years back), so I was well happy. It's been a good few months as late last year I caught a sight of Neptune and Uranus as well - both "firsts". Adrian

These things are so frustrating to track down so I wish you good luck in finding the source of the problem; whatever it does not detract from the excellent image. Adrian

Nice image Wim and interesting write up - as always. Looking at your image at 1:1 what is causing this to happen to the stars on the r.h.s.? The l.h.s. of the image shows nothing similar. Adrian

Two nights in one week and great views of Mercury setting: This is one of 84 images I took using a Canon 6D + 50mm lens - click to open full resolution image to see Mercury between the tree and bush: Used QuickTime to produce a video from the 84 images: Mercury-070423.mov This little video (really short!) was taken with an old Canon G16 - great for low light imaging and star trails/star videos: MVI_2533.MP4 Adrian