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Knight of Clear Skies

Back to the 60s - With Heart, Soul & Double Cluster

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Here's an image taken with some 1960s technology, my 135mm f3.5 Super Takumar lens. I read online somewhere that it may be flatter and produce less CA than the f2.5 lens I 'upgraded' to, so I thought I'd try this out and see if I could use it without stopping down. I'd tried this a long time ago on the same target, one of my first efforts at AP, but back then I didn't know about the 'thirds focussing' trick. I also wanted a better image of these targets together, I made other errors previously such as leaving the eyepiece cap off, allowing some stray light to sneak in.

30340455410_58426571be_h.jpg

This is 19x2 minute subs with dark bias but no other calibration frames, so 38 minutes in total - I was hoping for a longer run but cloud intervened. Gradient Xterminator sorted out the vignetting. Shot down in Cornwall earlier this month but I've only just got around to looking at it.

The corner stars certainly aren't perfect but it's useable, although the bright star at lower right has an off-centre halo or reflection. I've cropped the left hand edge as I did a poor job with the framing, wish I'd moved the Double in a bit. For some reason I can't fathom this lens gives good star colours, which I usually struggle much more with in processing. There is a fair bit of faint extended nebulosity just showing, especially around the Heart.

A successful test overall, I'm thinking about using this lens with my clip-in Ha filter while I'm up here in light-polluted Hertfordshire. It's also a good match for my EQ3-2 mount due to its light weight, it doesn't seem to like my 200mm f2.8 lens very much.

Edited by Knight of Clear Skies
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Simply awesome result :hello2: A way better result than mine with the Canon 100mm macro lens. Can you tell me what you mean with the "thirds focussing trick"?

A pic to be proud of ...

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That's really good.

I have a Zeiss Sonnar 135mm and it's pin-sharp when wide open as well. I need to use it more.

What's particularly striking about both my lens and yours is the absence of chromatic aberration.

<edit> it's hard to be sure, but it seems the sonnar lens configuration is apochromatic.

Edited by Stub Mandrel

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That is a cracking result for 38 mins of data. That has encourage me to get the Takumar 135mm out and onto my modded 450D.

I just need bring all my gear out of its summer hibernation. 

once again 'cracking image'

 

Tim

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For comparison here's one I did with my Zeiss 135 f3.5, wide open in August. IMHO its shows just how tight this type of lens keeps the stars.

The Sonnar and Takumar 135 f.3.5s appear to be excellent lenses for widefield - long enough to get detail while still faster than many scopes.

North America Nebula.png

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Thanks everyone. I put this one at the end of my processing queue as I didn't think I had enough data to improve much on my older image, but of my recent efforts in many ways I'm happiest with it. These targets are a natural fit at 135mm on an ASP-C sensor.

On 29/10/2016 at 21:38, Ruediger said:

Can you tell me what you mean with the "thirds focussing trick"?

Focussing on a star a third of the way from the edge gives better focus across the whole frame, this seems to work with any lens or scope.

On 29/10/2016 at 22:16, Stub Mandrel said:

I have a Zeiss Sonnar 135mm and it's pin-sharp when wide open as well. I need to use it more.

What's particularly striking about both my lens and yours is the absence of chromatic aberration.

I've heard good things about the Zeiss Sonnar 135 as well. Generally, older lenses exhibit a bit more CA than modern ones but these ones seem to be well corrected, at infinity focus anyway. The less demanding f3.5 models may be better than the faster ones in this respect.

Edited by Knight of Clear Skies

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36 minutes ago, Knight of Clear Skies said:

The less demanding f3.5 models may be better than the faster ones in this respect.

The 3.5 is the 'classic' version.

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14 minutes ago, Knight of Clear Skies said:

Tried a version with a bit more colour (boosted Ha and stars separately) but I'm not sure if I prefer it or not.

New.

30543295840_58240a780a_h.jpg

Original.

30340455410_58426571be_h.jpg

Oh yes, better for me. And, boy, did you ever have the focus nailed on this one. Sooooo tight.

Olly

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13 hours ago, ollypenrice said:

Oh yes, better for me. And, boy, did you ever have the focus nailed on this one. Sooooo tight.

Olly

Thanks. :) I think it's the lens more than anything, it's always produced tight starfields. It's a very simple four-element design:

Super-Multi-Coated_Takumar_135mm_F35_opt

Whereas my Canon 200mm f2.8 L lens looks like this:

ef_200_f_28l_ii_usm_block_dia.jpg

I've had a lot more trouble producing good starfields with the latter and have never achieved anything as clean, even stopping down using a front aperture mask, so I don't think it's user error on my part. I'll have to be a bit more scientific about using it next time. I suspect the 200 L may be over-rated for AP, unless my copy is less than perfect.

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hi this may be a daft question, but as these old lenses seem to focus to infinity, can you just whack them to infinity and shoot with a bit of stopping down?

My major bugbear as a newbie widefield astrophotographer is nailing focus. I know that many if not all modern consumer lenses seem to focus past infinity

 

I have a SMC 1:2/55mm lens to try here, but as usual skies are grey

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11 hours ago, mindburner said:

hi this may be a daft question, but as these old lenses seem to focus to infinity, can you just whack them to infinity and shoot with a bit of stopping down?

My major bugbear as a newbie widefield astrophotographer is nailing focus. I know that many if not all modern consumer lenses seem to focus past infinity

Kind-of. Before I had my camera modded I would focus the my 135mm lens by turning it to the stop, this gave a decent focus when stopped down slightly. However, I could never be sure the focus was a good as it could be, and it also depended on the thickness of the M42 adapter used - they do vary slightly. Some people end up adjusting old lenses to ensure they can reach infinity. After I had my camera modded the sensor was re-shimmed and this changed the distance to the flange. The same lens now focuses a little past infinity, less convenient but a good thing really.

I have a few tips for finding a good focus here that may be of some help to you. Old lenses do tend to be easier to focus than modern one with more travel in the mechanism. Auto-focus lenses need to go past infinity so they can find a point where the focus is getting worse and go back.

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