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Uranium235

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Posts posted by Uranium235


  1. 6 hours ago, Adam J said:

    whats your thoughts on reducing that to t2 thread straight after the M48 thread? would that result in vignetting?

    If the FW is attached directly to the camera - the m48-T2 adaptor will be about 11mm. 

    If you have a large format camera (diagonal of 22mm +l, I would use 36mm or 2 inch filters anyway. 

    The shorter I make the mod, the more options the user has got to configure it in a way that suits their camera. ☺


  2. 9 hours ago, Space Oddities said:

    Rob, I'm curious about the impact of your modification on the flange distance of the lens? Is it going to be similar to the Canon bayonet?

    I'm trying to keep it as close to the original distance of 44mm. But I can afford it to be up to 2-3 mm thicker (still leaves loads of room for a FW).

    I'm making the m48 thread just 4 or 5 mm.  That way any extension ring or FW will screw right up against the lens mod if you so wish ☺ 

     

    • Like 1

  3. 1 minute ago, KyleStoke said:

    Yeah didn't really mean it as a direct example more just a view of the inner workings, there isn't much in there. Seems to be as simple as 3 screws.

    I'm with you on the screw fits, I'm currently suffering from a horrible amount of tilt in my system  

    Its alright ;) Ive already seen the inner workings - a fellow SGL member was brave enough to take his apart so I could see if there are any nasty surprises lurking underneath the bayonet, and there isnt - so its all systems go :D


  4. 37 minutes ago, KyleStoke said:

    Hi Uranium, I am also very interested in these. 

    Take a look at this, I don't want to put the mockers on anything but seems very straightforward once you have a suitable replacement mount.

    https://www.dpreview.com/forums/thread/4234335

    https://www.dpreview.com/forums/thread/4157183 

    This also opens up the possibility of getting any version of the lens and simply replacing the mount (unless I've missed something)

    Im aware that the same rule will apply to any variant of the 135mm (and maybe other lenses - even for mirrorless), the modification Im proposing is about getting completely away from bayonet connections and moving it to a screw-fit.

    Those links seem to deal with the idea of switching between lens mounts of various manufacturers, which doesnt really apply to what im doing as im ordering a custom mount (focused on AP) from scratch. Of course, once its modded you wont be able to just pop it on your DSLR again - unless you take 10min to swap out the lens mount :)

    Lets concentrate on the 135mm f2 MF for now, get it working - and then we can take a look at where else this can be applied.


  5. If the camera is modded (as in filters removed, but not replaced), the sensor may need to be re-shimmed to work properly with some lenses. I had to do it to avoid the hard infininity stop with the Samyang 135mm.

    Or, you can try using EOS utils to get a proper look at stars while focusing.

    Typically, a modded camera in my experience has a difference between what you see through the viewfinder, and what you see on the preview screen  - the preview screen is the one that tells the truth (for daytime photography anyway).


  6. 46 minutes ago, Adam J said:

    All, 

    I will be going to Aus for a month early next year and am thinking of one of these for portable work with my ASI1600mm pro.

    I see a large number of people supporting both the lens and the camera as opposed to clamping only the lens or only the camera to the mount, is this strictly required or are people just doing it because droop / flex is an issue with the canon connector?

    Adam

    Adam, Im currently working on a fix to completely eliminate the droop issue with the EOS bayonet connection (conversion of the lens to M48 thread). Its going to be a prototype so watch this space and I will have some news in a week or two.

    Currently, the lens needs to be supported because its quite heavy, which causes compression of the bayonet fitting as the mount slews about - its only secured with three springs, which isnt really strong enough when imagng at f2 tbh - which is why people are supporting the lens to minimise the movement. Moving to an all-threaded connection will (in theory) resolve that issue.

    Another bonus of going all threaded is that you will claw back the space taken up by the EOS-T2 adaptor.

    • Like 2

  7. Just a thought..... if im to attempt modding the 135 I will need three measurements (I cant do it myself since I dont currently own a 135). The rear aperture looks quite wide when compared to some M42 lenses, so I need to know exactly what it is before hunting around for an M42 donor lens. If someone could whip out a digital caliper or ruler (for a rough measurement) that would be handy :)  

    The three measurements I need are as follows:

    16423_main2_1_measure.jpg.6845b562f3ed7a5189bf5731fdedb358.jpg

    If I cant find a lens that is suitable, then I know a chap who just might be able to machine something. If I were to go down the custom route, it would probably end up being M48 instead.


  8. 14 hours ago, Alien 13 said:

    I found that most old M42 lenses had a back that had three screws too, I did swap out a old lens using a donor one that fitted with no mods so worth taking some measurements and a visit to a few charity shops.....

    Alan

    Sounds like a plan! I've got a bench drill so I could drill any additional holes that might be required. The M42 donor lens doesnt even have to be working, as im taking it apart for bits.

     

    Edit: Patent pending....lol :D

     

    • Like 2
    • Haha 1

  9. 12 minutes ago, Alien 13 said:

    Sounds good, as to price a similar Canon version would be 6K+ so its a bargain......

    Alan

    Hmmmm.    that PL thingy has got me thinking a bit. It would be so nuch better if there was a custom adaptor that did away with the whole bayonet business  for standard photo lenses, it would hex bolt to the lens (using compression) and be ultra short....lol... I know might be dffiicult to envisage, but given some time and perhaps a test 3d print (before moving on to aluminium), it might be possible.

    lol... I wish Samywang made an M48 or T2 fit version... that would be fantastic :D


  10. I was looking around for a cheap used 135mm sammy, but came across something very interesting this evening. Samyang have released a 135mm cine lens, rated at T2.2 (transmission value, rather than F ratio). Its expensive, but I found that you can get a variant with a fitting  called "Positive Lock". Which gives a much more secure fit than the standard EF springs found on your typical camera mount (as cine lenses are heavy beasts).

    A little more digging found that there is a PL - T2 adaptor available, and the flange-chip distance of the lens is a generous 52mm.

    Would be nice to see someone with deep pockets give that a go for astro :) but as always, best to keep your powder dry until someone else makes the leap. Its only been released this month, so its yet to get any attention. If its anything like the standard 135, it would be quite special - especially given the secure nature of its mountings.

    The price? £1544 .... hahahaha yea right (if I won the lotto) :D:D:D 

    Weight? 1.4kg .... lol...

    Thats a lot of dough for 135mm (though probably cheap in the world of cine)

    https://rokinon.com/xeen/xeen-cine-system/135mm-t22

     


  11. It is entirely possible to get rho ophiuchi from the UK 😊 you just need a dark, unobstructed location, and pick your nights well (no fuzzy skies). 

    Now is a good time for it.  But you have to stay up well late for it...lol 

    Actually, I'm thinking of getting yet another of these lenses since my new home has such a limited window of opportunity I would need to cram in as much data as possible in just 3 hours... and the only way to do that is to go superfast.


  12. On 20/06/2019 at 16:53, Kaydubbed said:

    At F2 would you get phase shifting issues using normal narrowband filters?

    It also depends on the bandwidth of the filter.  A standard Baader 7nm filter is fine in my experience, however a 3nm Astrodon would be more inefficient. A 12nm Astronomik on the other hand would fare better.

    But hey, youre at f2!! :)  so a slight loss in transmission is no big deal at that speed.

    • Like 1

  13. On 13/05/2019 at 08:03, JohnSadlerAstro said:

    Hi,

    It's something I definitely wasn't expecting! The jet is in the correct direction though, and is in the opposite direction to the coma. It's also strongly luminous in the blue.

    I would suggest disregarding the standard method of taking short (<1min) subs, my ones were 120 and 200 sec, at iso800, I believe. It's quite possible to get the galaxy core + jet without too much clipping. 

    Good luck!

    John

    Just working on it now mate (its been a while since I last got out).

    But.... ive just checked the first sub (240s) and bingo... its there!! :) my first (intentional) jet!

    I'll leave the camera running for an hour or two - just for the sake of nose reduction - and hoovering up some background fuzzies. Im getting a few unexpected bumps in RA guiding though, no idea why becuase there is absolutely no wind our there tonight.

    • Like 1

  14. On 17/05/2019 at 16:39, Adam J said:

    Rob I have looked at this a couple of times over the last year and I always wonder how you control camera rotation with this setup. Also how do you colimate?

    You have some degree of control over the rotation (prior to attaching camera) by simply taking out the screws on the tilt adjuster and rotating it in portions of 120deg, if you get it close, the rest of the camera orientation is finished by tweaking up the tightness of the extention rings (not too tight though... dont want to bind them). Its kinda arbitrary, but Ive never failed to get the camera landsacpe or portrait with it (in repect to the focuser).

    Collimation is done simply by removing the corrector (it screws out). Or... if you have a short cheshire in your box you can just leave the CC in, attach an EP holder to the M48 thread and off you go... but I do stress that it needs to be a short cheshire - otherwise you will hear the glorious sound of metal on glass... not good! :D


  15. On 30/04/2019 at 20:49, JohnSadlerAstro said:

    ZoomedJet.jpg.51ec627bbccd0f7894c477104fba6cf5.jpg

     

    Have you checked if the jet correct? If it is - im impressed! Jets are something i've been trying to capture for years...lol. I dont think I have a close up of that galaxy in my archive, so I'll have to get some fresh data while i still can.

    It might be worth me getting the 178 on that for some close-up action... and possibly enhance the jet slightly with some creative layer masking in Ps.

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