Another ultra-light travel kit project

[Jules Tohpipi]

On 19/10/2022 at 20:38, badhex said:

After quite a lot of back and forth with the vendor mentioned previously, we may now have success! They will make the adaptor for 45eur plus shipping, which is pretty reasonable! 

I've also created an overview diagram of the planned setup:

 

On a slight tangent, I love the graphic you created for this! Out of pure curiosity, did you use a 3D package or get very creative indeed overlaying rectangles and ovals in PowerPoint or 2D drawing software?

[badhex]

14 minutes ago, Jules Tohpipi said:

 

On a slight tangent, I love the graphic you created for this! Out of pure curiosity, did you use a 3D package or get very creative indeed overlaying rectangles and ovals in PowerPoint or 2D drawing software?

Haha thank you! I used a whiteboarding/ diagramming tool called Miro which I have used for work for many years. 

It is 2D only, Miro is very free-form and a bit like powerpoint in how you can group and join shapes, so most of the shapes (being variations of cylinders) were actually the standard flowchart database shape of a cylinder, which I then joined several of and shaded accordingly to give me a rough version fo the shape I wanted. I'm a very visual person so diagrams are very helpful to me. 

I even made the focuser (which I am removing so was not really necessary!) 

[Jules Tohpipi]

55 minutes ago, badhex said:

Haha thank you! I used a whiteboarding/ diagramming tool called Miro which I have used for work for many years. 

It is 2D only, Miro is very free-form and a bit like powerpoint in how you can group and join shapes, so most of the shapes (being variations of cylinders) were actually the standard flowchart database shape of a cylinder, which I then joined several of and shaded accordingly to give me a rough version fo the shape I wanted. I'm a very visual person so diagrams are very helpful to me. 

I even made the focuser (which I am removing so was not really necessary!) 

 

Wow - mind blown all over again! I've had a 20 mins play in Miro and I can see its various templates and features are going to revolutionise my little world in PowerPoint for looks/speed/efficiency. I love the way you used it to create 3D representations of your astro gear. I'm truly inspired.

Good luck with your ongoing portable project which I'm finding equally interesting

[badhex]

Thanks, that's very kind! Glad you liked Miro - it is awesome and it certainly revolutionised my work (in tech/IT). I use it for everything - planning, project tracking, flow/process diagrams, whiteboarding, or cobbling together a quick diagram to help me and others visualise what I'm doing.

One of the coolest features is that if you have a physical whiteboard or wall with loads of post-its, you can take a photo and Miro will convert all of them to digital versions including handwriting recognition! 

[markse68]

On 03/11/2022 at 10:40, badhex said:

Anyway, a bit more progress! Still awaiting the M53x0.75 to T2 adaptor but I believe it is being anodised this week, so hopefully some news on that soon. 

How much is this custom adapter @badhex? I have a suitable ep for my finder project that reaches focus with the baader t2 prism i’m also currently playing with  but would like to use an amici prism which must surely have a significantly longer optical length so this might be a good option for me also.

BTW i have the evo-ff from starizona but haven’t noticed much improvement but i need to play some more with getting correct back focus distance

Mark

[badhex]

2 hours ago, markse68 said:

How much is this custom adapter @badhex? I have a suitable ep for my finder project that reaches focus with the baader t2 prism i’m also currently playing with  but would like to use an amici prism which must surely have a significantly longer optical length so this might be a good option for me also.

BTW i have the evo-ff from starizona but haven’t noticed much improvement but i need to play some more with getting correct back focus distance

Mark

45 EUR without shipping, so as far as astro gear goes, not too bad! Once it arrives I'll keep you in the loop as to how it turns out, and if you need one we can figure something where I let him know you're going to be in touch. 

The Evo-FF 2 also intrigued me because it has a good amount of back focus and is T2 but not sure how critical the front distance is but if I can get this stage working I am considering investing. I'm not totally sure if 55mm is enough to then add the diagonal so it would definitely be a gamble! 

Interesting that you said you don't feel like it makes a huge difference. How are stars at the edge when panning around? FC is certainly noticeable natively, which I'd expect given the fast FR. 

[markse68]

I guess the trouble is knowing if the fc comes from the objective or the ep. In my short time of testing it so far i didn’t notice much difference between with and without but it could well have been ep fc which i don’t think the ff could correct. I’m not sure i have any ep with good flat field which i’d need really to analyse it better. The only Naglers i have are short fl but may be useful for analysing it’s effect- they seem pretty flat. I suspect like with coma correctors the back focal distance is critical and i’m not sure how to work that out accurately with a prism in the way. BTW do you know what the difference is between “glass path length” and “optical path length” with respect to the baader t2 prism and where it’s measured from/to?

Mark

[badhex]

41 minutes ago, markse68 said:

I guess the trouble is knowing if the fc comes from the objective or the ep. In my short time of testing it so far i didn’t notice much difference between with and without but it could well have been ep fc which i don’t think the ff could correct. I’m not sure i have any ep with good flat field which i’d need really to analyse it better. The only Naglers i have are short fl but may be useful for analysing it’s effect- they seem pretty flat. I suspect like with coma correctors the back focal distance is critical and i’m not sure how to work that out accurately with a prism in the way. BTW do you know what the difference is between “glass path length” and “optical path length” with respect to the baader t2 prism and where it’s measured from/to?

Mark

I have an APM UFF 24mm which will be used with this scope, hopefully that should give us the results we need re FC so I will report back. 

On the subject of glass path vs optical path - the glass path is potentially aimed at binoviewer folks I'm guessing, as these diagonals are frequently used in binoviewing applications. I don't know why or if this is different to optical length. Are you seeing two different measurement listed somewhere? 

Also which T2 prism are you using? The one with the removable male thread (which reveals another T2 female thread) or the one like mine with the much smaller female thread behind the male thread (see my post earlier in this thread)? 

[markse68]

I think it is this one- I didn’t know there were different versions! :

https://www.baader-planetarium.com/en/baader-prism-diagonal-t-290°-32mm.html#

In the specs they say the glass path is 32mm but optical length is 35mm. Does one of those take into account the refractive index of the glass (they don’t mention glass type)?  Maybe that’s the glass path value as it should be shorter than the physical length I think (it gets quite confusing!)

Mark

[markse68]

I did ask Baader about this but it is still confusing haha- There’s a guy there called Alex who was very helpful (others less so) This is what he said:

“The glass path is not the pysical length of the piece of glass, but the space which the complete part needs in your setup. We give this value, because usually the backfocus of a telescope is known (or can be measured), and then you know how much of this length is needed for a filter, star diagonal or binoviewer is needes to reach focus. 

So: If you reach focus with this prism and use the T-2-threads for connection, you can replace it with a T-2-extension tube of 47.5mm and reach focus again. That is what we mean with optical length - the length the part takes up in the optical system.

At least for the regular 36mm T-2-prism #2456095, where we give a length of 38,5mm, this value should be correct - I use it at one of my own telescopes, and the optical length matches my experience.

Because of the way the light passes through a prism, it doesn't require as much back focus as a mirror in the same housing. That's also the reason why we always recommend prisms instead of mirrors for binoviewers: There, every millimeter is important to reach focus, and with a prism, you need less back focus than with a mirror.”

(ignore the numbers he used- they were for the Amici prism)

but in another email he contradicted that (I think…?) :

“The glass path is the actal length whichthe light travels through the glass - because this moves the focus point outwards, it is actually longer then the resulting optical length.”

I say I think he contradicted himself as he says the glass path is longer but in the specs it is shorter than the optical length 🤷‍♂️ 🤯

Mark

[markse68]

I think it must mean that the Baader T2 prism has a physical length of 35mm between the T2 mounting planes but only takes up 32mm of the scopes back focus as it shifts the focal plane 3mm outwards?

Mark

[badhex]

That makes sense - in a world of contradictory measurements! The two different prism diagonals also have slightly different optical lengths (or paths), the one I have is supposedly shorter (and the prism is fair bit cheaper, so maybe not as good optically).

[markse68]

Ah is it the "Zeiss" one with BBHS coating you mean? that is M34 according to their specs if you remove the male T2 adapter. Mine's definitely the cheaper one

https://www.baader-planetarium.com/en/baader-t-2-stardiagonal-(zeiss)-prism-with-bbhs-r-coating-(t-2-part-01b).html

[badhex]

Mine is this one:

https://www.baader-planetarium.com/en/accessories/optical-accessories/prism-and-mirror-star-diagonals/baader-prism-diagonal-t-290°-32mm.html

although I got the version that also comes with a nosepiece and focusing EP holder (non clicklock). 

I believe this one has the shortest possible optical length, from what I can see of all the specs (I spent a long time reading them 😂) 

[badhex]

No updates as of yet, still awaiting the adapter! Apparently it was sent to be anodised last week or so, maybe if I'm lucky it might be shipped in the coming week or so. 

[badhex]

Hello all, 

After aeons of waiting for the adapter, it has finally arrived! It took ages to be manufactured, then was sent and made as far as Germany only to be returned to sender for reasons unknown, and finally resent. Not thrilled with the speed of manufacture and communication could have been better, but the product itself is great:

The adaptor fits the tube perfectly, so I've put everything together and done a bit of testing on the most distant object I can (a chimney) so I think this will be the final config:

No dark skies test yet as it's obviously been 100% cloud cover, but with this arrangement there is plenty of inward travel available for infinity focus so I'm fairly sure this should work. 

Here it is with the APM 24mm UFF, AZT6 mount and Gitzo Series 2 Traveller:

 

All in all I'm pretty pleased so far but need a proper test! 

 

[markse68]

Looks great Joe- they did a really nice job on that adapter with the engraving and all! Interested to know how much of a weight saving this has made if any? That SW focuser seems pretty hefty

Mark

[badhex]

Cheers Mark, bit of an ordeal actually getting the thing and they randomly charged me 5 eur more than quoted - I only realised afterwards and it felt like more trouble than it was worth to quibble as I was already messaging them for updates on the delivery situation - but the quality is really great. Anodised aluminium and engraved with the adapter size etc., fits really well. 

I meant to mention the weight! The whole scope set up (modified dovetail/rings, scope, M53 adapter, T2 5mm extension, T2 low profile EP holder, T2 prism diagonal diagonal, nosepiece and T2 focusing EP holder) comes to 985g so I'm pretty pleased with that outcome. I could probably even shave off a few more grams by replacing the low profile EP holder, 5mm extension tube and diagonal nose piece with just a slightly longer extension, and I may do this once I'm definitely happy with the optical path length, but for now this works well and gives me a bit of flexibility. 

[ED Splitter]

Wonderful setup. Have often wondered whether the 50ed could be used this way. Any chance of a full product spec list in a post with a link to the fabricator you used? Thanks.  
 

[badhex]

On 08/05/2023 at 18:28, ED Splitter said:

Wonderful setup. Have often wondered whether the 50ed could be used this way. Any chance of a full product spec list in a post with a link to the fabricator you used? Thanks.  
 

Of course! Actually, life got very much in the way of me spending any time doing any astronomy at all; having moved countries in February all my stuff went into storage in Jan so I only had a month of bad weather with it. As it happens though, I get all of my kit back later today! Once I'm settled I'll try to get a full list together for you. 

[grjsk]

On 04/11/2022 at 19:09, grjsk said:

I have no real need for a ultra light setup, but your project is very intriguing!

Hmm, what happened? Suddenly, out of nowhere, this tiny thing showed up. I blame this thread 100%. 

 

[badhex]

On 16/05/2023 at 11:46, grjsk said:

Hmm, what happened? Suddenly, out of nowhere, this tiny thing showed up. I blame this thread 100%. 

 

Sorry I missed this post - so you succumbed! Looks good, I think I did some research on this scope when I was looking into small scopes - you'll have to let me know how it performs. It's certainly a lot simpler than the faffing I've had to do to get the Evoguide up and running! 

[grjsk]

On 20/05/2023 at 22:37, badhex said:

Sorry I missed this post - so you succumbed! Looks good, I think I did some research on this scope when I was looking into small scopes - you'll have to let me know how it performs. It's certainly a lot simpler than the faffing I've had to do to get the Evoguide up and running! 

It took a while, but I wrote a bit about my experince here: 

 

 

[badhex]

On 17/10/2023 at 10:48, grjsk said:

It took a while, but I wrote a bit about my experince here: 

 

 

Excellent! I'll give it a read, very interested to hear how it performs. 

 

On a related note, I wrote into the Actual Astronomy podcast with a few topics, one of which was the ultra-portable concept, what they refer to a 'suitcase observatory', and it got a small mention! Email from about 14m20s on the episode "Oddball accessories". Not sure if you listen but I'm sure they'd love to hear about your setup too. 

 

[grjsk]

4 hours ago, badhex said:

Excellent! I'll give it a read, very interested to hear how it performs. 

 

On a related note, I wrote into the Actual Astronomy podcast with a few topics, one of which was the ultra-portable concept, what they refer to a 'suitcase observatory', and it got a small mention! Email from about 14m20s on the episode "Oddball accessories". Not sure if you listen but I'm sure they'd love to hear about your setup too. 

 

I am an avid listener, but I haven't gotten to that episode yet. I'll give it a listen!