Trying to add a Widefield Setup on a Shoestring - How does this look?

[Xiga]

Hey guys

So i currently have a DSO rig (SW 80ED, HEQ5-Pro, a modded Nikon D5300, and a Finder-Guider) but am looking to add Widefield to my arsenal. Problem is, funds are extremely tight, so i'm trying to do the whole thing on an extremely low budget (max £200 all in!). So no Samyang 135mm F2 lens for me i'm afraid! ? So i thought i'd post up my plans below, in case either a) someone else finds it useful, and b) someone spots a massive whole in my logic (entirely possible!)

I just picked up a vintage lens off the 'bay for £20. It's a Tamron 135mm F2.8. It has a few dust spots but other than that it looks in good shape. I figured for only £20 it's basically risk-free! So the next thing is picking all the adapters and accessories to put the small rig together. And if the lens turns out to be a lemon, then at least i can hold onto the rig itself and wait until i can afford a better lens. Well, that's the plan at least. 

So here are the requirements that i need the rig to be able to fulfill:

- To be able to make use of a couple of 2" mounted filters that i already own - an IDAS-D1 and a Baader Ha. And have some way of protecting these filters from the elements (i really don't like the idea of them being exposed, without some form of protection). 

- To be able to use my finder-guider. I plan on stopping the lens down to something like F5 to improve performance, and just increase the subs length to compensate. Won't be a problem as i have the HEQ5-Pro, but i need to know that guiding is an option that i can call on if needs be.
I did think about having a setup that allowed for camera rotation (to aid with framing) but decided against it, for simplicity sake. I would also like to do some big mosaics too, and I'm already used to doing camera rotation with the 80ED, so i'm hoping this won't be a big drawback.

As i plan on stopping the lens down a fair bit, i will need step-down rings (as i don't like the multiple diffraction spikes that lenses yield). I would have needed some anyway, as my 2" filters have 48mm threads (i think, please correct me on that if i'm wrong) and the camera has a 55mm filter thread. Note, the camera also has a short in-built hood which extends out only a small amount. So i might have to add a DIY extension of some sort to that. 

So then i'm thinking the imaging train should look something like this: 

D5300 ->Adaptall 2 Nikon Adapter -> Lens -> 55mm to 52mm SDR (Step-Down Ring) -> 52mm to 48mm SDR ->IDAS-D1 or Baader Ha Filter -> 48mm to 46mm SDR -> Hoya 46mm UV Filter - 46mm to 26mm SDR's. I also plan on using the dew band from my 80ED (i'll just wrap it round more). 

So bringing the aperture down to 26mm, i think that makes the lens about F 5.2. And the Hoya filter should protect the more expensive 2" filters from the elements. And i have dew prevention too. 

As for the rig itself, i'm thinking that this will go directly into the HEQ5-Pro's saddle:

https://www.modernastronomy.com/shop/accessories/dovetails/deluxe-vixen-style-photo-dovetail-kit/

And then, using the 2 included screws from above, bolt the following to it to make a T-shape (one end will have to be a bit longer than the other):

https://www.altairastro.com/starwave-200mm-vixen-style-dovetail-bar-44.5mm-width.html

A flat-bottomed finder-shoe with M6 sized holes (not as easy to find as you'd think ) will go on one end:

https://www.astroshop.eu/mounting-brackets-and-accessories/astoptics-deluxe-finder-shoe-with-flat-base-m5-m6-/p,57782

And a baseplate with quick-release clamp for the DSLR will go on the other side (the baseplate even looks long enough that i might be able to add a DIY solution to help support the lens from sagging):

https://www.amazon.co.uk/Connect-Adapter-Release-Manfrotto-Stabilizer/dp/B01LVYYBB0/ref=sr_1_4_sspa?s=electronics&ie=UTF8&qid=1546567415&sr=1-4-spons&keywords=dslr%2Bquick%2Brelease%2Bclamp&th=1

A 3D print schematic for a 135mm Lens (the Samyang 135mm F2 actually). I can get this printed for as little as £12 online. It will probably be slightly too big for the Tamron, but if needs be i can just add a thin layer of something to the inside to make it a more snug fit. Hopefully this means i can still focus in my normal way - take short test subs on a bright star in SGP, while dialing in the focus using Bahtinov Grabber.

https://www.thingiverse.com/thing:2168672

Here are the links to the step-down rings, Hoya UV filter, and the Adaptall 2 Nikon adapter:

https://www.amazon.co.uk/Neewer®-Anodized-Step-down-Adapter-Including/dp/B00WW314VC/ref=sr_1_fkmr3_4?ie=UTF8&qid=1546142418&sr=8-4-fkmr3&keywords=dslr%2Bstep%2Bdown%2Bring%2B55mm%2Bto%2B26mm&th=1

https://www.bristolcameras.co.uk/p-stepping-ring-52-48mm.htm

https://www.bristolcameras.co.uk/p-stepping-ring-48-46mm.htm

https://www.bristolcameras.co.uk/p-stepping-ring-46-43mm.htm

https://www.amazon.co.uk/Hoya-Pro-1-Digital-Screw-Filter/dp/B007N8Q7KE/ref=sr_1_3?ie=UTF8&qid=1546139251&sr=8-3&keywords=hoya%2B55mm%2Bpro-1%2Bdigital%2Buv%2Bscrew%2Bin%2Bfilter&th=1

https://www.amazon.co.uk/d/Lens-Flash-Adapters-Converters/Concept-Adaptall2-Adaptall-2-adaptall-adapterll/B00LECY3XS

And then the only other thing should be some M6 screws for attaching the finder-shoe and quick-release clamp. 

All in, including the lens, it comes to ~£170. Assuming it works of course, lol.

 

Ok, if you made it this far and you're still with me, Congratulations, lol. So how is this looking overall do you think? Can you spot any gaping holes in my plans? The 2 things that spring to mind for me are, how to finely find and maintain focus, and weight. I've seen the Telefokus75 rings from Telescope-express, but at €75 i'd only be willing to add it if it's truly going to be a nightmare finding focus without one. I'd be interested to hear how others focus using a lens, and whether or not they consider the Telefokus a necessity. And as for weight, all i have are 5Kg counterweights. I wonder if i could get away with just pushing one right to the top of the bar? I know the FL here is short, so won't be demanding in terms of guiding, it's more about not wanting to stress the mount unduly with a big weight imbalance. 

Really interested to hear what you guys think, as i think i'll hold off on buying any of this until it's been through the official SGP Peer Review process ?

[tooth_dr]

Interesting read Ciaran and a well thought out plan. I’m currently working on something like this myself.

Do you think the second glass filter might cause issues with reflections etc?

I used a normal SW dovetail bar and SW finder bracket, but added a small bar or aluminum to dovetail bar for a flat mounting surface. I know don’t think this really was even necessary as the finder shoe fits fine on top of the dovetail bar without it.

I added a longer dovetail bar to the bottom of the camera, to allow balance with the long heavy lens on it ( I have a Sigma 105mm F2.8 lens)

I’ll try to find some pictures for you  

 

 

[teoria_del_big_bang]

Hi Ciarán,

Very interesting to me as I also am looking into a similar setup without too much outlay. I am not really experienced enough to offer advice but following with interest and would love to see your final setup. Please update this thread as you go ? 

Steve

[almcl]

Very interesting and well thought through (at least compared to my slightly less wide field rig) !

One thing I found, which wasn't obvious at the outset, was a need to rotate the camera to get the required framing.  Eventually this was achieved with a lens mounting ring. But then another problem arose: gradual differential flexure.  It took a while to discover the cause but it was cured with a second lens mounting ring.  To tie the camera and the guidescope together, a 5 mm aluminium plate of suitable dimensions with holes drilled to accommodate the various clamps was acquired from eBay for a few ££. A cheapskate solution, but I can now rotate the camera to any angle required and the target doesn't drift across the frame during the session. 

[happy-kat]

I would first dry run test your lens for chromatic aberration as that might drive the size of your step down ring, you might be lucky and find f4 a sweet spot on your lens.

[tooth_dr]

Here’s my setup, after looking at it, the aluminium isn’t really necessary. That isn’t the finder I use, just a spare one. The other one I use is on my other kit  

 

[Xiga]

15 hours ago, tooth_dr said:

Interesting read Ciaran and a well thought out plan. I’m currently working on something like this myself.

Do you think the second glass filter might cause issues with reflections etc?

I used a normal SW dovetail bar and SW finder bracket, but added a small bar or aluminum to dovetail bar for a flat mounting surface. I know don’t think this really was even necessary as the finder shoe fits fine on top of the dovetail bar without it.

I added a longer dovetail bar to the bottom of the camera, to allow balance with the long heavy lens on it ( I have a Sigma 105mm F2.8 lens)

I’ll try to find some pictures for you  

 

 

Funny, i was thinking the exact same thing Adam as regards reflections. I guess there's no way to know other than to test it out under the stars? I wonder is it better to have the two filters as close as possible, or would having a bit of a gap be better? Not ever having used a lens, I've no idea myself. Also, if anyone can recommend a better filter than the Hoya UV one i linked to above, one with better coatings that might help reduce reflections (or even if there is a better way to use my 2" filters, protected) then please do let me know, as i wouldn't mind spending more on this part of the rig. 

[Xiga]

15 hours ago, teoria_del_big_bang said:

Hi Ciarán,

Very interesting to me as I also am looking into a similar setup without too much outlay. I am not really experienced enough to offer advice but following with interest and would love to see your final setup. Please update this thread as you go ? 

Steve

Thanks Steve. Good idea. When the time comes, i will definitely take some test subs using different sized step-down rings, to see how big i can keep the aperture without sacrificing edge sharpness too much. 

[tooth_dr]

1 minute ago, Xiga said:

Funny, i was thinking the exact same thing Adam as regards reflections. I guess there's no way to know other than to test it out under the stars? I wonder is it better to have the two filters as close as possible, or would having a bit of a gap be better? Not ever having used a lens, I've no idea myself. Also, if anyone can recommend a better filter than the Hoya UV one i linked to above, one with better coatings that might help reduce reflections (or even if there is a better way to use my 2" filters, protected) then please do let me know, as i wouldn't mind spending more on this part of the rig. 

Would there be any real issues just using them without protection.  I cant see how it would harm them?

[Xiga]

1 minute ago, tooth_dr said:

Would there be any real issues just using them without protection.  I cant see how it would harm them?

You're probably right Adam, and i'm just being paranoid, lol. I guess i'm just used to the filters being shielded inside the OTA of my 80ED. Have you, or anyone else, used filters in this way? It would be good to hear of any potential pitfalls before giving it a go. 

Now that i hear myself talk about it, i think i would be willing to just use them exposed to the elements. The dew band from the 80ED should be more than enough to keep any moisture off them. 

[tooth_dr]

It certainly would be good to hear some other opinions on it, but I imagine the coatings are hard, and as you say, wont really get a chance to get damp.

[Xiga]

12 hours ago, almcl said:

Very interesting and well thought through (at least compared to my slightly less wide field rig) !

One thing I found, which wasn't obvious at the outset, was a need to rotate the camera to get the required framing.  Eventually this was achieved with a lens mounting ring. But then another problem arose: gradual differential flexure.  It took a while to discover the cause but it was cured with a second lens mounting ring.  To tie the camera and the guidescope together, a 5 mm aluminium plate of suitable dimensions with holes drilled to accommodate the various clamps was acquired from eBay for a few ££. A cheapskate solution, but I can now rotate the camera to any angle required and the target doesn't drift across the frame during the session. 

That's a brilliant setup Al (hopefully that's your name! lol). Simple, yet effective. I take it you just drilled the holes yourself? 

I would never have thought that differential flexure would be possible imaging with just a lens. I can't tell from your picture, what camera and lens are you using? I presume it's a FF camera and a long FL lens? If so, what is the total weight of each? I think my D5300 and Tamron 135mm F2.8 lens will only weigh about 850g in total. Add on the finder-guider and it shouldn't be much more than 1Kg. Based on this weight, and a FL of 135mm, i wonder if differential flexure is something i will need think about myself? 

I love that you have kept rotation as part of your setup. You've got me worried now that i should go back to my original plan of including this! FWIW, here is the part i had originally sourced to allow for camera rotation. It only moves in one axis, so would be perfect for getting the right angle. I was planning on putting it directly onto the StarWave dovetail bar, and then the camera quick-release clamp on top of it, but in the end i ditched the idea as i wasn't sure it would provide a secure enough base for the camera & lens assembly, especially if it needed to be rotated a lot. What to do you think of it? 

https://www.amazon.co.uk/Manfrotto-234-Monopod-Tilt-Head/dp/B000KHZ8AA

I would love to emulate your own setup, as it looks much more simple, secure, and allows for rotation. To do that, i would have to wait until the lens arrives, as i'd need to know the exact width of the Tamron's barrel before i could order some lens mounting rings though. I don't suppose you have a link to where you got the aluminium plate? 

For info, here are some pictures of the Tamron:

[Xiga]

6 hours ago, tooth_dr said:

Here’s my setup, after looking at it, the aluminium isn’t really necessary. That isn’t the finder I use, just a spare one. The other one I use is on my other kit  

 

Thanks for posting these Adam! ?

I'm a bit confused by the orientation though. Does the EQ-6 have a horizontal saddle? My HEQ5-Pro has a vertical saddle, which is why i've been thinking i need some sort of T-shaped assembly (or a large square plate, as per @almcl above). Would your assembly not be pointing East or West when in the Home position of my mount, rather than pointing at Polaris? Or am i missing something simple here? 

My finder-guider will still be getting the bulk of it's work from the 80ED, so it will need to be able to freely move back and forth between both rigs. So i definitely need a finder-shoe on the small rig. The finder-guider has a (now ancient!) QHY5 guide cam attached to it permanently. The whole thing resides in a set of guide scope rings, the one labelled as #FRS8 below. I also used a wingnut screw to tighten it down real tight) it seems to do the job for subs up to 20 mins on the 80ED, so fingers crossed it will be no different on the small rig. 

[geordie85]

1 hour ago, Xiga said:

Thanks for posting these Adam! ?

I'm a bit confused by the orientation though. Does the EQ-6 have a horizontal saddle? My HEQ5-Pro has a vertical saddle, which is why i've been thinking i need some sort of T-shaped assembly (or a large square plate, as per @almcl above). Would your assembly not be pointing East or West when in the Home position of my mount, rather than pointing at Polaris? Or am i missing something simple here? 

If you turn the saddle 90 degrees before you turn the mount on then your camera will be pointing north. 

It doesn't have to start vertically 

[tooth_dr]

1 hour ago, Xiga said:

Thanks for posting these Adam! ?

I'm a bit confused by the orientation though. Does the EQ-6 have a horizontal saddle? My HEQ5-Pro has a vertical saddle, which is why i've been thinking i need some sort of T-shaped assembly (or a large square plate, as per @almcl above). Would your assembly not be pointing East or West when in the Home position of my mount, rather than pointing at Polaris? Or am i missing something simple here? 

My finder-guider will still be getting the bulk of it's work from the 80ED, so it will need to be able to freely move back and forth between both rigs. So i definitely need a finder-shoe on the small rig. The finder-guider has a (now ancient!) QHY5 guide cam attached to it permanently. The whole thing resides in a set of guide scope rings, the one labelled as #FRS8 below. I also used a wingnut screw to tighten it down real tight) it seems to do the job for subs up to 20 mins on the 80ED, so fingers crossed it will be no different on the small rig. 

 

As @geordie85 saysyou definitely don't have to have the saddle vertical.  The saddle slot can be any which way you choose to have it.  Unless you mean something different to this?  My dual rig of ED80s is mounted in exactly the same fashion as my widefield setup (which I haven't used yet )

[Xiga]

13 minutes ago, geordie85 said:

If you turn the saddle 90 degrees before you turn the mount on then your camera will be pointing north. 

It doesn't have to start vertically 

 

1 minute ago, tooth_dr said:

 

As @geordie85 saysyou definitely don't have to have the saddle vertical.  The saddle slot can be any which way you choose to have it.  Unless you mean something different to this?  My dual rig of ED80s is mounted in exactly the same fashion as my widefield setup (which I haven't used yet )

Well, don't i feel foolish! ? I've always just started my HEQ5-Pro pointing North, so i've never even considered just starting it from a different position. What a numpty! ? 

Ok that's great. I no longer need the Photo Dovetail Kit, which brings me back down to a single dovetail, which is much better. 

Now i just need to work out the simplest way to attach the DSLR + lens, solidly (with no sag), and which allows rotation. I wonder if the Manfrotto 234 and quick-release plate would be up to the job? ?

[tooth_dr]

Cool looking lens btw 

[Xiga]

11 minutes ago, tooth_dr said:

Cool looking lens btw 

Thanks Adam. Hopefully the dust spots (of which there are definitely quite a few, from the photos i've seen) don't impact it's performance under the stars. 

Here's a link to some more info and user experiences with it:

https://www.pentaxforums.com/userreviews/tamron-adaptall-135mm-f-2-8-ct-135.html

 

I've also just come across this:

https://www.amazon.co.uk/TARION-Professional-Aluminum-Follow-49-82mm/dp/B01BHPPTAC/ref=sr_1_6?s=electronics&ie=UTF8&qid=1546647869&sr=1-6&keywords=focus%2Bring&th=1

For £7 it's got to be worth a punt. I think all it does is add some extra distance to the point of where you turn to focus, thus adding some extra sensitivity? 

[almcl]

8 hours ago, Xiga said:

I take it you just drilled the holes yourself? 

Yes, pilot holes using my Dremmel drill press then had held electric

what camera and lens are you using? I presume it's a FF camera and a long FL lens?

As per sig, it's the Canon EF 200 mm Lens weighs 850 gm with step down rings attached to Canon 700d/T5i (APS-C sensor)

 Based on this weight, and a FL of 135mm, i wonder if differential flexure is something i will need think about myself? 

I was surprised and initially went for camera mounting and lens ring, but the frustration of trying to get the Spaghetti nebula (Sh2-240) in frame eventually led to the solution above.

I love that you have kept rotation as part of your setup. You've got me worried now that i should go back to my original plan of including this! FWIW, here is the part i had originally sourced to allow for camera rotation. It only moves in one axis, so would be perfect for getting the right angle. I was planning on putting it directly onto the StarWave dovetail bar, and then the camera quick-release clamp on top of it, but in the end i ditched the idea as i wasn't sure it would provide a secure enough base for the camera & lens assembly, especially if it needed to be rotated a lot. What to do you think of it? 

You have obviously given this much more thought than I did initially, so that looks a great set up..

I don't suppose you have a link to where you got the aluminium plate? 

Ebay seller alum-droitwich was my source (here) but there are quite a few suppliers here in the West Mids.

 

 

[Xiga]

9 hours ago, almcl said:

 

Thanks mate. 

850g is indeed a heavy lens. I think I read somewhere that if the lens weighs more than the camera, then it needs supporting. My D5300 weighs 480g and the Tamron is supposed to weigh only 370g, so I'm going to try the Manfrotto 224 and see if I get lucky enough that sagging and differential flexure won't be an issue. 

Ps - How did the differential flexure show up in your subs? Just wondering so I can look out for it myself. 

[almcl]

4 hours ago, Xiga said:

Ps - How did the differential flexure show up in your subs? Just wondering so I can look out for it myself. 

Despite apparently good guiding by PHD, stars were moving by anything up to 60 pixels during an imaging session, comparing the first sub with the last.  While this wasn't a problem for the stacking software, it did give rise to walking noise.  Had a thread about it somwhere, if I can find it, I'll add a link.