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Uranium235

Imaging with the Samyang 135mm f2

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On 18/09/2020 at 14:29, mAnKiNd said:

Finished another project with this gem of a lens :)

Full details in the link: https://www.astrobin.com/g569tc/?nc=user

Cheers,

Minos

192318416_HeartnSoul.thumb.png.3a72bf35ce80a7c3e1000896f86f30eb.png

Minos, that's simply fantastic! Superb image, and great work! I spent a few minutes contemplating the details you captured, and like you I was surprised at these dark areas. Fascinating!

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Thanks to @mAnKiNd I've changed the mounting arrangement of my Samyang by using the WO tube ring - it is soooo much better. I find that the CEM25-EC allows me to image without guiding up to 180s which is also the sky limit around here.

This is 10 x Ha, 20 x SII and 30 x OIII (all 180s) stacked in APP and processed in PI with a little bit of noise reduction (Dfine2) in Affinity.

1325442509_Soul_SHOLumDfine2levels.thumb.jpg.df0d2ff514d9a8be17b68a56c44ebb08.jpg

The new setup.

IMG_0649.thumb.JPG.1c5fec6d0d290f837d4f2a63fc2b2541.JPG

IMG_0648.thumb.JPG.b569923b1ca3063387f460845602c986.JPG

IMG_0650.thumb.jpg.5fba72feab422afe2725ec0734ad8fe9.jpg

Adrian

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25 minutes ago, Dinglem said:

where did you get the pulley/belt for your EAF from?

MotionCo - they provide a very comprehensive supply of pulley wheels and belts.

I bought an additional belt to cut and stick to the lens itself to help with registration.

HTH

Adrian

Edited by Adreneline
Clarification
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I thought I would combine H, O and S in the linear state and then stretch, so this is 10 x 180s of Ha, OIII and SII mapped as SHO. At least this approach ensures all channels are equally stretched (as advocated with RGB) but results in a rather pastel look.

424297536_ET_FB-SHODfine2Lum.thumb.jpg.2f2cb68df9c19c473e44a0c4125b5965.jpg

More data would be good but surprising what you can get with 90 minutes and a Samyang 135mm.

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10 minutes ago, Adreneline said:

I thought I would combine H, O and S in the linear state and then stretch, so this is 10 x 180s of Ha, OIII and SII mapped as SHO. At least this approach ensures all channels are equally stretched (as advocated with RGB) but results in a rather pastel look.

Stretching color can make it turn pastel as it changes the RGB ratios for non linear stretch.

Try following approach:

- create artificial luminance (just add all three linear channels with pixel math for starters - that will create usable luminance) and stretch that to your liking

- do what you already did - make linear combination of RGB (SHO)

- paste stretched luminace as new layer on top of linear rgb and set its blend mode to luminance (LAB color model - Gimp does this, not sure if PS has that option, it should).

This will make color transfer keeping RGB ratios (I hope).

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2 minutes ago, vlaiv said:

Try following approach

Thanks Vlad - I'll give it a go and see how I get on.

P.S. The GSO is boxed up for moving to darker skies - It might be a few weeks before it see the light of night again.

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Currently just playing with this excellent lens using a modded 550D but eventually intend to switch to my ZWO ASI1600MM-Cool + x7 31mm EFW.

Just wondering if 31mm filters will be large enough for this fast lens or will I need to go bigger (36mm) to avoid vignetting at say f2.8 or faster?

Graham

 

 

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11 hours ago, groberts said:

Currently just playing with this excellent lens using a modded 550D but eventually intend to switch to my ZWO ASI1600MM-Cool + x7 31mm EFW.

Just wondering if 31mm filters will be large enough for this fast lens or will I need to go bigger (36mm) to avoid vignetting at say f2.8 or faster?

Graham

 

 

Easy, go bigger for anything not just the lens, you will know that you will be in safe side always, i didn't process my image yet to see if i can see much bad vignetting, but i don't have Samyang 135mm lens actually.

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OK I get that but for those using the ZWO1600 what size filters are you using and do they work OK? 

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1 hour ago, groberts said:

those using the ZWO1600 what size filters are you using and do they work OK?

I use the Samyang 135mm (at f2.8) with the ZWO EFW (8 position), filled with 1.25" Baader LRGBC and Astronomik Ha, OIII, SII filters with the EFW attached directly to the ASI1600MM-Pro (set up as in photographs above). I find there are no problems with vignetting that flats cannot sort. FLO sell the ASI1600 packaged with either the 1.25" or 31mm filters so I guess that is some sort of endoresement that the pairing works.  I am very happy with the results that I get but then I am not as discerning as some.

Adrian

Edited by Adreneline
Clarification

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Thanks Adrian that's reassuring.  It's just that I haven't used my ASI1600 with the Samyang yet and am considering upgrading my filters to Chroma / Astrodon and wanted to make sure the 31mm would still be OK.  As a matter of interest  what bandwidth do you use 3 / 5 / 7nm & what sort of exposure times do you need?

Graham

Edited by groberts

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22 minutes ago, groberts said:

As a matter of interest  what bandwidth do you use 3 / 5 / 7nm?

Haha! 6mm! Trust Astonomik to be different.

I'm afraid Astrodon and Chroma would require me to dig far deeper than the bottom of my pocket! I also have the Baader NB filters but was never happy with the 8mm OIII, hence the change to Astronomik. I rarely image in LRGB because the light pollution round here is so high.

Again I stress I am not that discerning - I can live with the dodgy stars in the corners and the minimal vignetting - at the end of the day I usually crop them out as part of the alignment process in PI. I try to put what I am imaging in the middle of the frame and if others are more interested in the corners of my images (as some clearly are) then that's their problem and not mine.

Just as an aside I have also used my Canon 200mm f2.8 lens with the same setup and get just the same amount of vignetting and dodgy stars in the corners. I am confident I've got the spacing right - it's just the way it is.

HTH in your deliberations.

Adrian

Edited by Adreneline
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This lens is the best astrophotography purchase I've ever made. Pictures taken with Samyang 135mm, a modified Canon 60D and SW Star Adventurer.

 

NGC7000_16_8_2020_KÄSITELTY_V2.png

Elephant_Trunk_1h48min_KÄSITELTY.png

Sadr_Region_1hr_41min_Samyang135_27_8_2020_KÄSITELTY_V2.png

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I managed to grab 'first light' using my Samyang 135mm f/2 lens on Friday 16th Oct 2020 for this image of the Heart and Soul grouping (IC1805/IC1848), framed with the Double Cluster (NGC884/NGC869), all straggling the boundary of Cassiopeia with Perseus.
 
I thought that I would do this test at f/2 just to see how well the lens performed wide-open and although there is some coma at the edges/corners the worst is conveniently trimmed to better frame the picture🙂 It's a very nice lens and seems to justify its reputation.
 
36x300s (3 hours)
Samyang 135mm lens @ f/2
ASI071MC Pro
IDAS D2 light pollution filter
SW AZ-GTi in EQ mode
Guided by 50mm finder with ASI224MC
All powered by ASIair Pro👍

IC1805_group_135mm.png

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On 29/10/2020 at 23:43, fireballxl5 said:
I managed to grab 'first light' using my Samyang 135mm f/2 lens on Friday 16th Oct 2020 for this image of the Heart and Soul grouping (IC1805/IC1848), framed with the Double Cluster (NGC884/NGC869), all straggling the boundary of Cassiopeia with Perseus.
 
I thought that I would do this test at f/2 just to see how well the lens performed wide-open and although there is some coma at the edges/corners the worst is conveniently trimmed to better frame the picture🙂 It's a very nice lens and seems to justify its reputation.
 
36x300s (3 hours)
Samyang 135mm lens @ f/2
ASI071MC Pro
IDAS D2 light pollution filter
SW AZ-GTi in EQ mode
Guided by 50mm finder with ASI224MC
All powered by ASIair Pro👍

IC1805_group_135mm.png

Nice image. Still waiting the delivery of my lens. About 7 weeks now!

Edited by Chefgage
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On 21/09/2020 at 21:22, Space Oddities said:

Minos, that's simply fantastic! Superb image, and great work! I spent a few minutes contemplating the details you captured, and like you I was surprised at these dark areas. Fascinating!

Thats an absolutely amazing image 🙂

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Hi all, if I want to use this lens at f4 using step down rings am I right in thinking i'll need to step down to approx 32.5mm? I don't want to use the internal aperture ring as it gives diffraction spikes that I don't really like. 

Thanks.

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135mm / 4 = 33.75mm

135mm / 32.5 = ~ F/4.15

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I think the actual focal lengh is closer to 129mm as calculated by plate solving etc but i'll have a look at the step down rings and see which is closest :)

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I've been using step down rings as well, keep in mind this will create some vignetting. I've been using an aperture of 49mm (f/2.8) for the Samyang, but I've seen some people recommending ~37mm (f/3.6). 

From what I've read, I think the sweet spot for this lens is around f/3.2. Less, and you give up some sharpness. More, and you give up some light. I guess it depends where you want to place the threshold, I personally thought it's a shame to waste the light gathering ability of this lens for rounder stars, which is why I went with 49mm (also because with another 49-48 ring, I can screw in filters).

Anyway, you should get good results anywhere within this 37-49mm range :)  And given how cheap step down rings are, why not try a couple and see what works best for you? 

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Fantastic image @mAnKiNd ! I really like the image scale you've achieved with your ZWO, you've been able to dive a lot deeper into space than I can with my DSLR. 

Here's my recent shot of the belt and sword of Orion taken with my astro-modified 60D.

 

 

 

Orion_Samyang 135mm_SGL.png

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@AstroFin Nice image! If you dither your every frame and then drizzle, you can halve your image scale and “go deeper” as you say without using a ZWO. 

I wouldn’t necessarily say going deeper has as much to do with image scale, as it does with integration time. In my case, just under 31 hours to get that deep signal. There’s also blinking out the bad frames and many post-processing skills involved to bring out that signal effectively. Having said that, yes, a cooled, lower noise sensor does help a lot!

CS

Minos

Edited by mAnKiNd

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