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Uranium235

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Posts posted by Uranium235


  1. 11 hours ago, Space Oddities said:

    According to their website, it's the QSI 583 WSG-5 with a Nikon adapter :) 

    Just noticed the camera in those pics... see the reinforcement/support added to the camera itself? That is exactly what I did with the Atik 383L+ so both lens and camera are supported - when operating at f2 any compression of the bayonet adaptor will cause tilt in the field, so its best to take all potential strain out of that weak spot. Getting all four corners perfect is the first essential step if youre thinking about putting a mosaic together.

    Probably not an issue with a light DSLR, but if youre sicking a big CCD or FW on it - then support will be required.


  2. 2 minutes ago, Space Oddities said:

    Rob,

    Apparently it's possible to use a belt system to focus this lens. I found one using a Robo focus motor (found on the Deep Sky West remote observatory website):

    IMG_1312-min.jpg

    IMG_1313-min-1.jpg

     

    The Samyang/Rokinon 135mm also exists in a video version (135mm T2.2), which is the same as the f/2 optically, but with a different focusing system. It might be easier to interface the lens with a focusing motor.

    However, I believe the aperture ring is clickless, like most video lenses. I'm not sure that's a good thing for astro?

    09634adee97aa5f13c6056a0dcad9c21.jpg

     

    Is that a 683WSG? I never managed to get a bayonet adaptor short enough due to the ridiculous backfocus requirement of the camera...lol.

     


  3. This excellent little lens has carved out quite a niche for itself over the past few years, outperforming lenses of higher value - and one of the very few lenses available that can operate wide open at f2 and still maintain a relatively flat field. To give you some idea of what f2 is like, well.... its as fast as you can possibly go! (at that focal length). Great for quickly bagging targets - or going very, very deep to chase the toughest of challenges.

    Here you can share your images taken with this little (but heavy!) lens, and perhaps offer suggestions to others as to how to set it up. For the Canon variant, the flange to chip distance is 44mm. You should get as close to this as possible, but definitely not over becuase then you wont be able to focus to infinity. Ideally, you want it a tiny bit short... perhaps 0.5mm or less to avoid the hard infinity stop.

    Mounting is also important, the connection between the lens and camera should be a snug as possible - even to the extent of padding you your bayonet adaptor with a thin spacer to get that bayonet connection as stiff as possible (as that is the weakest link in the imaging train).

    • Like 4

  4. 13 hours ago, Adreneline said:

    An excellent idea - and not just images but also images of how members have mounted the lens and overcome spacing and remote focussing challenges maybe?

    Thank you.

    Adrian

    Sure, later on i will kick off another thread for people to share their experiences with this brilliant but of kit. 

    Not sure about remote focus though, perhaps someone else has figured out a belt type system? But I found that manual works fine - and it saves a couple of hundred quid :)  

    • Like 1

  5. 18 hours ago, Andywilliams said:

    Hi Rob,

    Is this imaged through a Samyang f2??

    Is so, its fantastic.

    Just one question. The stars are showing quite pronounced diffraction spikes (I personally really like them). Is this a quality of the sheer length of the integration time here? or is it a quality of this lens?. I wouldn't have  expected to see spikes like this off of a camera lens ?

    Many thanks,

    Andy

    Hi Andy,

    Its a combination of a number of factors, the lens was wide open @ f2 but the largest contributing factor was the very lengthy processing required to dig out the IFN but keep the stars down to a more acceptable size. Next to the 100Mp mosaic I did a few years ago, this was by far the toughest thing to process as I had to learn a whole new method (called screen mask invert).... which takes forever (as its an iterative process).

    I did cover that method a couple of years ago at one of my processing workshops, but it did make a few brains explode...lol.

    Normally diffraction spikes from refractor telescopes are caused by the cell clips - which gives a good indication of your quality of focus (no spikes = focus not good enough).... but I'm not so sure that is the case with a camera lens (as in having cell clips).

    Though in the grand scheme of things 6 hours isn't that long, but a I was at a dark site so that helped a lot. Its just a shame I never got to add colour to it.

    But another great thing about f2 is that is it is so fast, you can work at a speed that counters the Earths rotation - its the only way I was able to bag the below image from 52degrees North:

    35260828101_3e7082668a_k.jpg

    • Like 3

  6. On 20/03/2019 at 08:02, masjstovel said:

    @Knight of Clear Skies ive decided to go for the 150 PDS with EQ5 and then add the synscan goto st another time. I made a post on the equipment beginner  forum, and were told it then would be exaclty the same performance as a EQ5 pro synscan goto. Correct?

    With 9 kg limit on the mount i guess that would be stable enough with a 988grams nikon d810 added. 

    No i havent even considered that. Thank you! What is a coma corrector? 

    I also wonder what adaptor(s) i need to mount a Nikon full frame

    I think the 150 will be too much for a standard EQ5 - that requires a HEQ5 at minimum. You need to keep the weight down with the EQ5, so its either the 130pds or 80ED (or smaller.. perhaps the 72).

    As a general rule of thumb for mounts at the chepaer end of the scale, your payload should not exceed 50% of the rated maximum load. A fully loaded 150pds with corrector, camera, and guider will probably take you well over 5kg which is too much for reliable and consistent guiding.

    Oh, and the corrector (coma corrector) is an additional correcting lens to remove the coma/field curvature that you get from newtonian type optics - they are pretty much mandatory.

    Or..

    Push all the cash into an HEQ5 and use it with just the DSLR and whatever lenses you have to hand (any lens between 100-200mm will give good results). It might be worth scouring the for sale ads to see if there is one up for grabs at a knockdown price. The point of this is that you will not have to upgrade further down the line (false economy etc...) when you want to use a bigger, heavier telescope.

    The mount is the heart of the setup, get it right first time :) 

    • Like 1

  7. Atik 383L+ says it all :) With that camera you have to bake the desiccant tablets roughly every 5 months to keep the moisture at bay.

    Another thing I used to do was first, cool the camera to -10, let it stabilise for a bit (you could be doing your mount calibration or focusing while that is going on), then I drop it another 5c as my usual operating temperature was -15c (going down to -25 during colder months).

    Great camera though, its one of the very few (in fact... i cant think of another!) that has a 1/4" photo screw hole - very, very handy if you are using lenses with it.

    • Thanks 1

  8. 18 minutes ago, Adam J said:

    Its a real shame ASI have stopped making this camera as I have always wanted one for a dedicated galaxy camera. 

    Stopped making it? Thats a shame.... well, I suppose there would be the QHY equivalent if youre stuck for finding one.


  9. Being as galaxy season is here, I've switched to the ASI178 Cool, which turns the 130 into something of a galaxy hoover :) 

    Leo Quartet - ARP316 (usually overlooked for the triplet), 30x180 - only darks applied. Needs probably 100+ subs and proper calibration to make it decent:

    Leo-Quintet_PSDBE.thumb.jpg.e11740fc1d619e7afa5447b4202d1ecd.jpg

    • Like 5

  10. Good idea to rotate the light source. 

    But if anyone is using a laptop or monitor for flats, it's worth making sure that it is square on to the OTA. Purely because computer displays don't do so well off axis (like trying to view a monitor from an angle isn't as good as being directly in front of it).

    • Like 1

  11. 80ED or 130pds? Hmm, ive had both.

    130pds: Bang for buck, faster (f5), cheap, but may require user improvements or mods.

    80ED: Ease of use, slower (f6.35 with 0.85x), nearly double the price with reducer, requires very little in the way of tweaks (usually the focuser tension).

    • Like 2

  12. I use registar for the same thing. Though it's sensible to use a colour sensor that's larger than your mono (so no mono data is wasted).

    It's also possible to combine different focal lengths and telescope types. This is data taken using a star 71 (widefield) and a 200pds and 130pds (newtonian) for high res details:

    NGC7000 North America - Pelican - Refined HST

     

    • Like 1

  13. 8 minutes ago, RolandKol said:

    My ASI224MC nicely fit into 2", however even so, it was not dead central....
    I am skeptic with this experiment, but very curious about your results! :)

    Yeah, there are the manufacturing tolerances - it could be way off, but if works it will be one of the all-time top bargains!

    I will double check it with a cheshire to see if it got close.

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