Uranium235

Just putting my thinking cap on about something  - namely how to collimate this (and other newts) with the imaging camera in place.

Previous thoughts about this always involved putting a short focal length lens where the filter would be... however... today I had another idea.

Astro cameras are very sensitive things and can easily cope with a high f ratio. So, what about doing away with the lens concept and using a pinhole instead? 

It's cheap, anyone can make it, and with a few careful calculations should deliver the right focal length required for taking images of the secondary mirror.

Daft idea? Maybe... maybe not 😄

I guess if its just for the heater, you could try a lithium pack with a 12v output, maybe something like this?

https://www.amazon.co.uk/TalentCell-Rechargeable-6000mAh-1a4XT9/ref=sr_1_7?keywords=12v+power+bank&qid=1581114689&sr=8-7

If i didnt know better, but whoever made that adaptor probably got the idea from here...lol..

I built my mod a good 4 or 5 years ago:

8 minutes ago, mAnKiNd said:

Impressive that you built one. Yeah, no rotation is a bummer, but I suppose I've learnt to live with it.

I took off (and lost) the rotation ring on the FUFmpcc because it compromised stability, which was my whole purpose for using these adapters.

I was pretty lucky in that mine rotated to portrait (with respect to the focuser) right at the point where the threads started to really tighten up. If it was to far before that I'd either have to come up with a different configuration - or take a chance and tighten it up as much as poss until the right camera rotation is achieved.... but the big danger with that is a cold-welded thread (never much fun to try and undo). Thats why I apply boot polish to my threads to reduce or prevent binding when doing things up fairly tight.

Im using the same kind of thing, but I built mine myself

The only issue with this arrangement is that the camera rotation is arbitrarily set by the travel of the threads - so you dont have much wiggle room to get it right (to the nearest 90 degrees).

Just rolling my 130 for just over an hour... got the MPCC spacing utterly wrong though...lol. So ive had to crop the ugly part out.

10x450 (Ha)

Samyang mod now available from FLO

https://www.firstlightoptics.com/adapters/astro-essentials-samyang-lens-to-m48-adapter.html

Product discussion thread here:

From what it seems after discussion, is that there is a good chance it will also work with the manual 85, 50, 35 and 14mm lenses (canon fit). Hopfully someone can verify this over time.

5 minutes ago, Davey-T said:

And 14mm f2.8.

Dave

 

That looks almost identical!  You will notice that the three screws are not quite 120 degrees apart - one of them is offset by about 10deg, same as the 135mm.

What it looks like is that the rear end of all the MF canon fit lenses are the same construction, just with different optics upfront (makes sense to keep production costs down).

More on spacing... You can see the M48-T2 adaptor (plus delrin spacer) im using is roughly 8.5mm, and the distance from the camera T2 plate to the sensor is a whopping 35.5mm.

Both add up to the magic number of 44mm, when setting up your spacings, dont forget to add distance when using filters.

Example:

Astronomk: +0.33mm (may not need to bother)

Badder: +0.66

Astrodon: +1mm

It might not seems much, but 1mm can put you well short of infinity focus. The camera im using has a mixture of Astrodon and Baader filters - slighly more complicated

Okey doke, back in front of a proper keyboard now:

As for the question of other lenses in the Samyang range, I have to stress that this mod is for manual lenses only - as the electronics invoved with an AF lens would simply get in the way.

Now, looking a the bayonet for the 85mm Sammy - it looks like the mounting is suspiciously similar to the 135

I suspect the 50 and 35mm manual lenses would follow suit. So if you already have one of those in your box then there may be a good chance it would work.

6 hours ago, Adam J said:

I asked Uranium about this several months back and he said it was in the pipeline so glad to see this. The samyang 135mm is one possibility for my coming mobile setup. 

I wonder if there is room for a filter draw and a filter adaptor...

Great Idea. 

More than enough room, you can use a standard thickness filter wheel which is usually about 21mm and still have room left for whatever adaptor and extension rings you need.

Always better to space it just short to start, then add a delrin spacer or two in order to get it focusing as close to infinity as possible.

I'm chuffed that one of my ideas actually turned out to be useful 😄

I'm out working at the mo, but I'll fill in with more info when I get home. 

Quick update chaps, the Samyang mod will be available from FLO shortly.... watch this space

23 hours ago, TareqPhoto said:

Very nice results!

So, which camera did you use for those? and at what F number did you use the lens?

Thanks

Its the QSI683ws camera (KAF8300), and the lens was stopped down to f4.

Its been a while, what with work, Christmas, and endless cloud getting in the way of things. But I've gotten a few images out of the modified lens now

The only downside, this particular lens is not quite on par with the two Ive had previously - so Ive had to stop it down a bit. The following images are all fairly short runs, just over an hour for each, and absolutely no calibration:

29 minutes ago, spikkyboy said:

hi Matt, i have looked at the Samyang 135mm lens. around £400. I then found a zoom lens 50mm to 200mm. so will that give similar results to the 135mm or am i missing something? I know the sayang has superior umc coatings but wonder if the focal length is the main thing here? thanks.

You very seldom get a flat field with a zoom lens, questionable levels of CA too. 

Fixed, prime lenses are always better. 

This is the one I used:

https://www.teleskop-express.de/shop/product_info.php/info/p2742_TS-Optics-short-Adapter-from-2--to-T2-thread---Rotation-System.html

Example of a dovetail adaptor:

(attached to the CC via M48)

1 hour ago, Fieldsy said:

I've looked at the compression ring but that seems out of stock , I've been told a twist lock is more secure but requires a extra 10mm in focus which I'm down to a few mm left and already poking into tube.

Compression rings are a waste of time/money, and the clicklock eats up far too much backspace for it to be of any use to the imager.

Two best ways are either screw fit, or three screws with a dovetailed 2"-T2 adaptor.

9 hours ago, 8472 said:

Are there any owner's who know if the OTA will cover a full frame sensor without vignetting, coma and the like?

Thanks

Vignetting is pretty much unavoidable with the 130 (or pretty much every other telescope to some degree), depending on the size of the sensor. 

Same goes for coma.... BUT .... that is what flats and coma correctors are for

I got the KAF8300 sensor working with the 130, but only after a few modifications to the telescope. But if youre talking about full frame as in 35mm....lol.. no chance. There are very few astrographs that can cope with that (and the ones that do cost a mint).

1 minute ago, Davey-T said:

What have you done with all my bunnies ? 😂

Dave

Its not quite in true focus Dave, so there may be more to come    the filters are now clean, but I didnt get a look at the sensor since the shutter was closed.

Taken some test flats to see what the illimination might be with this camera, some darkening in the corners but I reckon the flats will sort that out on real data:

Taken @f2

Oh, and ive just checked the technical drawings for the 683 camera... it appears the filter is ~20mm away from the sensor surface. Hmmm.... it might work, worst case scenario would be that I have to take it down a few stops to correct any vignetting from the filters.

8 minutes ago, JamesF said:

Even looking at the still from the video I'm thinking "Nah, that's really not my bag"

James

Only the first couple of minutes are relevant for this, but even getting the bayonet off seems like a bit of a pain.

Ive just looked at what it takes to disassemble a typical canon (200mm) lens - its much more complicated, but not impossible. Like I previously thought, the engineering involved would have to be bang-on for it to all go back together as it should: