Uranium235

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!

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

 

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.

30 minutes ago, al-alami said:

Apparently the night we were hit with winds gusting at around 45 or 50km per hour. 

I tried rebuilding but the focuser is too messed up, and the metal under the focuser got really bent. So, collimation of the focuser is next to impossible. ?

Just had a bit of a brainwave..... in future get a couple of dumbell weights and hang (or place) them on the accessory try/leg spreader, that would provide a bit more protection.  Or maybe a way to anchor the tripod?

On 19/04/2019 at 00:10, al-alami said:

I am sad to say that my 130pds has seen the last of it's imaging days.  I very strong gust of wind blew it and my mount (HEQ5 Pro) over.  The tube has got good selections of bends in it, and the focuser is a mess. ?

I took everything apart and rebuilt it, but it seems the metal under the focuser is so bent out of shape that the focuser doesn't sit right anymore. I won't even talk about the focuser needing a helping hand to focus properly, so focusing is a 2 handed process.

So basically it's easier and cheaper to buy a new one than to fix it. ? 

Unless someone has a used one they don't want any more!  

Sounds awful mate.... that must have been some gust of wind! Ive never heard of an NEQ5 being blown over before.

To look on the bright side, the 130 isnt an expensive bit of kit to replace and your camera was not damaged. Just think what it would be like to have a nice APO and CCD camera hit the floor!... ouch!  

On 16/04/2019 at 17:23, Adam J said:

 The 178 will be better for small galaxies due to the 14bit A/D and the ASI1600mm pro or a KAF8300mono camera will be better for nebula work, I would not discard something like a 460EX either.  

 

Exactly what I would have said

The 1600mm and KAF8300 have roughly the same sized sensors, so it should work (with a little tweaking to get the flattest field possible). The 1600 is cheaper, so that will allow extra headroom for a couple of filters etc if the budget is around 1k ish. Get a Ha filter first, that will do the most for you (well... in about 2 months when the MW swings back around). Even so, the resolution with the 1600 is 1.2" p/p - which is still pretty damn high, but not so high as to exceed the resolving power of the telescope aperture (~0.9").

The 178 is best used either as a galaxy buster on the 130, or if you want a larger FOV - mount it on something like a Samyang 135mm f2 or the 200mm Canon EF lens.

The 178 with a 135mm lens:

And the 178 with a 130pds:

Massively different FOV sizes there.

23 hours ago, JP50515 said:

Uranium it's good to so you're still here in this thread after all these years. Honestly mate I chuckle at one of your earliest comments regarding Skywatcher paying this thread commission for uptick in 130PDS sales...more like paying you commission! I think your images are the reason that a large number of us landed on this scope, and to this day I am beside myself to understand how you pull such amazing data off a cheap imaging newt mounted to an EQ6. 

21 hours ago, matt_baker said:

I can agree with this for sure. 

One of the reasons I got a 130P-DS was seeing a few of Uranium's images and thought there's no way such a cheap scope could grab stuff like that.

 

Thanks guys

But we have to take a number of things into consideration if you want to get the best out of it.

Starting off with the mount, the 130 is quite light so it never bothers an NEQ6 (not even close...lol).

Secondly there is the camera, that is were the magic happens - which as we all know can only be achieved with a mono (yes... there, i said the M word ) CCD or the one of the recent crop of cooled CMOS cameras because you need very low noise to get good data. This point would need a lot of consideration in regard to sensor size and/or pixel size, and what you want to image.

Then, its the 130pds - probably the simplest way to deliver photons to the sensor..... no fancy-dan glass required  (barring the coma corrector) - just a couple of small mirrors... its as uncomplicated as it can be

Lastly, its guiding, choice of target, framing and mosaic planning and total integration time.

But at the moment, its my only telescope - so its going to get used a lot, especially now I've got it bagging galaxies with some decent detail. With the ASI178 though, ive found it takes a 100+ short(ish) subs to get a very clean image.

Just a quick 2 hour pop at M51, no proper calibration though so its a bit on the rough side. Also had a bit of flex somewhere, but I will track that down and eliminate it.

(taken with the ASI178MM cool)

9 hours ago, emyliano2000 said:

Are they in Ha?

The first two are Ha, the third is luminance  

Heart nebula with the ASI178MM cool: (50x240)

Belt/Sword

Bubble to Cave (25x240)

Not to say that the 200 cant make a good image (because it can). But the difficulty is in a different ball park compared to the 130.

Plus your choice of targets would be limited by the fov available from a 1 metre focal length.

1 minute ago, Startinez said:

Crikey, I think I've got my next scope sorted... I currently have a 90mm f/10 refractor so I think the two would make a good pairing.

 

Out of curiosity, if I can afford the 200PDS should I go for that over the 130 or are there other things to consider than how much light will be collected? Same focal ratio. I guess one thing to consider is that when adding a coma corrector into the mix you're throwing another £100 on top of the scope price.

The 200pds? Hmmm nope  

It's the weight and bulk you have to consider (its heavy when loaded up), and it will catch the wind like a sail. It's easier to just get more out of shorter focal length by using a camera with smaller pixels (as long as you don't over sample the resloving power of the optics).

30 minutes ago, RolandKol said:

 

I had to circumcise mine also...

Ouch...   

19 hours ago, Andywilliams said:

A definate yes please from me......I look forward to seeing more of you guys images with this lens.

Cheers,

Andy

Already done mate, it's in the getting started with imaging sub forum (since its am option that would be great for beginners as well). 

https://stargazerslounge.com/topic/333381-imaging-with-the-samyang-135mm-f2/

^^ Now... that is a tough target! Nice one

Quite right, it allows to go for stuff that with an ordinary f5 imaging scope, would be a bit of a slog.

2 hours ago, RolandKol said:

 

By the way, while adjusting the lens holding bolts, - how do you know you do not introduce any tilt?

I did mine very, very carefully

What I did was to sit the whole thing vertically, so the back of the camera is on a flat surface and the lens is pointing upwards. Then tighten up the bolts one by one until the barely make contact... just until you feel the smallest amount of resistance. They neednt be done up tight - the guidescope ring is just there to stop the lens flopping about under its own weight and compressing the bayonet adaptor (even though any movement is tiny, its enough to upset an f2 field).

The 3d printed bracket looks like a good solution to that (I would probably add felt to the rings), but I would also want the camera braced.

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.

@Alien 13 @Knight of Clear Skies

Now moved

I'm out at work at the moment, so I'll move it later or tomorrow morn  

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):

 

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?

 

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

Great for big mosaics too

Suppose I'd better kick this one off then with a few pics

A random bit of Cephus:

CTB1 (Difficult)

Iris nebula (Atik 383L+ Lum, Canon 1000d RGB):

M81/82 Integrated Flux Nebula (Difficult)

Rho Ophiuchi and galactic core:

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).

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   

Hmmm.... Im thinking that there may be enough users of this particular lens to start a showcase thread (similar to the 130pds or 80ED thread).

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: