Adreneline

I do think it is better without the green BUT that is entirely personal taste. I had a very quick go in PI with green and magenta removed but only minimal boost to blue and yellow/gold: As with all these images colours are all down to personal preference. If you wish I can let you know my steps in PI to achieve the above - I am sure with more time it could be better. Thanks for sharing your masters - it's always fun to have a play with other peoples data. Adrian

SCNR will remove the green from the image; some like to remove it all (1.0), some like to leave a trace (0.9). If you invert the image and apply SCNR at 1.0 it will remove the magenta which often occurs as star halos - again a matter of personal choice/preference. Once green is removed some like to boost the blue and the yellow/gold regions using ColourSaturation and/or CurvesTransformation.

Excellent Maurice - a very deft touch with the processing with great colour palette. Looks like the Tak-ε is doing a great job for you with very nice stars all the way to the corners. Adrian

Just eye-balling the image the stars on the right look 'bigger' to me than on the left of the image - that might suggest there is a bit of tilt from left-to-right - maybe?

Sadr taken mid-May, presented at 1:1 : 12 x 300s of S, H and O: Just the edge stacking effects cropped reveals the stars look pretty good all the way to the corners: Processed to tame Sadr and reveal the heart of Sh2-108 Don't you just love the Samyang 135

This image is nothing much to write home about but I was keen to revisit Sadr and try to get a result where Sadr itself does not dominate this region of nebulosity. This image is just 12 x 300s of S, H and O taken in nautical darkness and no Moon, taken on 23rd May. Pre-processed in APP and post-processed entirely in PixInsight: Presented at 1:1 with only minimal edge cropping so you can see the star shapes all the way to the edge: I am pleased that even with the Samyang 135 mm I have been able to reveal the beautiful area of nebulosity at the centre of Sh2-108 that is so often obscured by Sadr itself, a star that is well separated from the Gamma Cygni nebula and plays no part in ionising the nebula. Solved to reveal the main features: Even in grey scale it presents well: Thanks for looking. Adrian

Ebay.

I'm not sure why you are not following the advice I gave you on the 28th May; you need to make incremental changes of 0.1 mm not 1 mm.

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! 🤣