Another ultra-light travel kit project

[badhex]

Hello all, 

As mentioned in the postie thread, I seem to have developed reverse aperture fever.

I was lucky enough to be on holiday for around three weeks recently, which was not specifically astro focused but included some darker skies. I took my ZS73 travel kit which is a lovely compact setup and weighs about 12 kg total, and fits in one cabin friendly backpack, however I only really had the opportunity for about four sessions. Although it's certainly very manageable, it's still quite a lot of stuff to take just for a few nights, especially when it's more of a holiday that happens to have darker skies, vs going somewhere with dark skies for astronomy purposes. 

With this in mind, I spent some time thinking  about how one might put together and even smaller, lighter setup for these situations. Something small enough not to take up my whole hand luggage allowance, or even better, can be safely put into hold luggage without concern. 

So, onto the specific criteria:

 

Scope size, performance, and cost

50mm is probably the smallest you'd want to go. 60mm would be ideal, but as the existing travel kit already contains a 73mm I don't think I'd save much space/weight by going with a 60mm, so 50mm seems like the next step down.

With such a small objective, obviously high quality optics are needed to squeeze as much performance as possible out of every mm. Borg's fluorite options and modular nature would work well here, but is too costly for such a small and specific use scope, and would rule out putting it into hold luggage for me. I already own a TS 50mm RACI with 1.25“ fitting, which is okay at being a finder but suffers badly from both field curvature and at higher powers, CA.

This brought me to the EvoGuide 50ED with its FPL53 doublet objective, (reasonably) low cost and decent performance - a small scope which I've always admired but not had a good reason to purchase. As this scope was not designed to use a diagonal, some trickery would be necessary to deal with short in-focus. It's pretty fast at F4.8 (242mm FL), so perhaps not all EPs would be compatible, and let's face it this scope will never be a planet killer, but after reading a large number of threads and reviews and specifications here and elsewhere, I realised I could probably make it work.

So, I bought the EvoGuide, along with a Baader T2 prism diagonal (miniscule 33mm light path), and will combine it with a Baader ultra-low profile EP holder that I already own (10mm light path). This will screw directly onto the back of the scope, and takes up a total of 43mm which is 6mm less than the supplied extension plus the Baader low profile EP holder (49mm) in straight through mode. 

 

Eyepieces

As this is meant to be a lightweight kit, I will perhaps need to resist the urge to take my premium EPs which all weigh 350-450g each, so I'm hoping to use some of my existing B-team EPs which are significantly lighter. I do have the APM Superzoom 7.7-15.4mm but it needs a lot of in-focus in 1.25“ mode so I suspect it will not come to focus. 

I really like the BST 5mm (48x), and my old, but well loved, Meade HD60 9mm (27x) also fits the use case quite well. At lower powers, it will be very hard not to take my Morpheus 17.5mm (14x) because I absolutely love the views through it in every scope I've used it with, but again to save weight I think I will need to stick with an 18mm BST (13x). I may not even need this focal length, as there is not a huge difference between this and the lowest power/max field) 

The one area where I probably have to take an A-team EP is the APM 24mm UFF (10x) because I don't have anything else as light at that focal length. I do own a MaxVision 24mm SWA which could be decloaked, but I probably won't save that much weight and the APM is just a better EP, so I feel that this is a good compromise for max field of view (6.5°!). I'm also hoping that the UFF will cope better with the field curvature inherent to such a fast scope. 

I will need to do some testing to determine how well these selections work, and whether I might be able to employ a Powermate for higher powers. I have BST 3.2mm, but I've never found the views to be good through it in multiple scopes, so will try it but probably give it a miss. 

 

Mount and tripod

I already own a Gitzo Traveller Series 2 which is great, and the logic choice for weight saving/simplicity is probably the AZT6 which again I already own. The problem is that I've never really got on with that mount. It's either too loose, or too sticky, but I will definitely do some more testing once I have everything in hand. Another choice would be the Borg single-arm fork mount, however these are not so cheap. More to come on this. 

 

Storage

I have found a camera case which look like it will be plenty big enough for everything except the tripod, so that's also on its way. 

 

Progress

Whilst I'm waiting for the diagonal I have tested a few EPs on Jupiter last night in straight through mode, and they all come to focus with a bit to spare, so I should not have any issues there.

I'm happy to say that despite the neckache I was really surprised at how sharp the views were. Banding on Jupiter was clearly visible using the Morpheus 4.5mm and BST 5mm and I'm pretty sure I'd have been able to pick out the GRS had it been visible at that time. The skies were very hazy with intermittent clouds, so I had no opportunity to observe anything at lower powers, but the higher power views really surpassed my expectations! 

 

If you've made it this far, thanks for reading! I will update this thread (with pictures) as and when there are more developments. 

Edited September 28, 2022 by badhex

[cajen2]

Please note that I know virtually zero about mounts, being a confirmed dob man but how about a Berlebach Castor II?

https://www.firstlightoptics.com/alt-azimuth-astronomy-mounts/berlebach-castor-ii-altazimuth-mounting.html

It weighs only 1.3kg yet can support 8kg, and if you buy the optional extra dovetail clamp, would even hold two scopes.....Plus, despite being Berlebach, it's actually quite cheap. Perhaps I'm missing something obvious in my ignorance.

[badhex]

13 minutes ago, cajen2 said:

Please note that I know virtually zero about mounts, being a confirmed dob man but how about a Berlebach Castor II?

https://www.firstlightoptics.com/alt-azimuth-astronomy-mounts/berlebach-castor-ii-altazimuth-mounting.html

It weighs only 1.3kg yet can support 8kg, and if you buy the optional extra dovetail clamp, would even hold two scopes.....Plus, despite being Berlebach, it's actually quite cheap. Perhaps I'm missing something obvious in my ignorance.

Thanks! I have a Scopetech Mount Zero which I love and weighs around 1.4kg, so I would not gain much with the castor unfortunately. As it stands, the AZT6 is about 1kg so ideally whatever I go for would need to be either the same weight and a better mount, or lighter with the same performance as the AZT6. I might be asking too much! 

[happy-kat]

Something I've read on here before is a shorty barlow used in front of a diagonal improves available back focus distance helping with being able to use an eyepiece, though I haven't got around to try this myself yet but hopefully will this winter.

[jjohnson3803]

I have a Zero and was considering adding a Castor II, but a few people commented that their Castors had a habit of letting scopes crash into tripod legs.  Maybe just a matter of watching the az tension carefully, but it makes me somewhat hesitant to go with a Castor.  YMMV.

 

Edited September 28, 2022 by jjohnson3803

[Ags]

I had a Castor and can't believe it weighs less than 2kgs. I certainly wouldn't  consider it in a travel setup. On the other hand I can't imagine the Castor causing scopes to bash into tripod legs. With a Castor, the scope must be perfectly balanced, so there is no reason for sudden scope movements.

Why not an ES 68° 16mm - I have owned the 20 and 24 in the range and I hear the 16 is just as good.

[badhex]

22 hours ago, happy-kat said:

Something I've read on here before is a shorty barlow used in front of a diagonal improves available back focus distance helping with being able to use an eyepiece, though I haven't got around to try this myself yet but hopefully will this winter.

I read quite a few of the threads mentioning something similar including your own diagonal experiments with the Evoguide from a few years back. I was also thinking yesterday that I wonder if a 1.25x GPC could help here? Once I've done some testing with the current setup (when the diagonal finally arrives!) I will see how it works out but I'm confident I should be able to use my existing EPs.

There is also the option of adding a Starizona Evo FF v2 field flattener, which will not only help with any potentially disturbing field curvature, but also has a back focus of 55mm, so will give more room to play with. As it stands I'm a bit concerned that the barrels of some EPs might crash into the prism since the EP holder is only 20mm optical length, but I'll find out soon enough! 

[badhex]

2 hours ago, jjohnson3803 said:

I have a Zero and was considering adding a Castor II, but a few people commented that their Castors had a habit of letting scopes crash into tripod legs.  Maybe just a matter of watching the az tension carefully, but it makes me somewhat hesitant to go with a Castor.  YMMV.

 

I have travelled with the zero and I love the mount, but it is definitely the upper weight limit and kind of overkill for this scope. The Borg fork mount I mentioned is probably the eventual best option, miniscule but also expensive! 

[badhex]

2 hours ago, Ags said:

I had a Castor and can't believe it weighs less than 2kgs. I certainly wouldn't  consider it in a travel setup. On the other hand I can't imagine the Castor causing scopes to bash into tripod legs. With a Castor, the scope must be perfectly balanced, so there is no reason for sudden scope movements.

Why not an ES 68° 16mm - I have owned the 20 and 24 in the range and I hear the 16 is just as good.

Now that is an excellent idea as a longer term plan! Technically, I shouldn't be spending money as I'm unemployed as of the end of this week, however I have wanted to try the ES 68° range. Definitely keeping a hypothetical tab open for that! 

Edited September 28, 2022 by badhex

[badhex]

Lots of tests and tinkering happening, but unfortunately not had time to write out a full update on the portable kit.

In short, overall things have not worked out so well so far, and more work needs to be done to get this up and running 🙁

Firstly, the bag I bought is fine, but if anything it's a bit too large. I can fit everything in with no issues but it doesn't really fit in one side of my case so it needs to be about the same width and length but not as high. 

Secondly, I've found some tube rings that fit the exact tube diameter (without guidescope style adjustment screws) and attach to a standard vixen dovetail. This makes everything a bit smaller and less awkwardly shaped, plus I can remove the adaptor block as well savign a bit of size and weight. 

Lastly, the Baader T2 prism arrived just in time before I went away to darker skies for a few days and attached to the scope it looks great! As mentioned I used a Baader ultra short T2 EP clamp to keep the optical length down.

I had been a bit concerned that this could result in EP barrels crashing into the prism if I'm not careful, and was initially pleased to find that there was a small lip to stop this from happening. This soon proved to be a problem, however, when I realised that this lip means the whole optical length which I had carefully calculated was longer by just a few mm - and means that none of my EPs will come to focus 😱

Not to be defeated, I had a brainwave that perhaps the male T2 thread could be unscrewed to reveal a female T2 connection, allowing me to use a different male-male T2 adaptor without this lip and reclaim a few mm - a part that I already have lying around. I did some investigation before applying too much force just in case, and found online that another more expensive Baader prism does unscrew on the male side, so I figured this would be the same. I eventually managed to unscrew it to reveal... A much smaller female connection. It seems that the lip mentioned earlier is in fact the inner part of the male thread which screws in here, so there's no way to shorten the light path of this prism any further. It's really frustrating as the BBHS version of has the possibility of a female connection on both side of the prism, so I don't know why the construction is different here 🙁

So, even though I only need to shave a few mm off the light path to make this work, at this point I have only a few options left.

1. Try some other diagonals, such as this BBHS prism, however the light path is a few mm longer and it's an expensive option with no guarantee of it working
2. Cut the tube down on the objective side by 5mm or so, but I'm not super comfortable with that plus I don't know anyone with the tools needed.
3. Remove the focuser altogether and put something together with a couple of adapters. I have found someone who makes an M53x0.75mm male to M42x1mm male adaptor (they might even make up a customer one to T2) and I've seen a few M42x1mm to T2 adaptors around. It would also potentially drop a bit of weight from the overall package. 

At the moment, option 3 seems the most feasible but I suspect I'll end up spending nearly a hundred euros on various adapters - the M53 is 45eur alone as it is so specialist. Once it's reduced down to T2 however, there are plenty of extension tubes and adapters to get the correct length, and I can use the T2 focusing EP holder which hopefully should be enough focus travel. 

So far so frustrating. Perhaps this was not the wisest gamble in my astronomy history! 
Any thoughts or other options I may have missed are welcome! 

[happy-kat]

This might be useful it's a very long thread about the telescope with lots of details 

https://stargazerslounge.com/topic/314564-sky-watcher-evoguide-ed50/?do=findComment&comment=3449062

Edited October 3, 2022 by happy-kat

[badhex]

1 hour ago, happy-kat said:

This might be useful it's a very long thread about the telescope with lots of details 

https://stargazerslounge.com/topic/314564-sky-watcher-evoguide-ed50/?do=findComment&comment=3449062

Thanks @happy-kat- this is indeed the thread where from where I gleaned most of my info and I'm following essentially the same process. Given that @DRT  had managed to reach focus, I thought I might be onto a winner so I did some measuring. I believe part of the issue is that the televue EP he used also has its focal plane low down in the EP barrel or whereas mine seem to be further inside the EP. 

[badhex]

A bit more of an update. I've done some more research and it turns out that I do have a couple of EPs that will come to focus, just, but generally they are either too bulky for a travel kit (MaxVision 24mm SWA) or only provide a small FOV (Celestron 25mm Plössl, BCO 10mm and 6mm). Since I will tend toward low power views with this this scope, I do want to maximise FOV where possible. 

Which brings me to my next point. I have frequently used Ernest at Astro-talk's reviews when researching eyepieces but had never paid attention to the fact that he measures what he refers to as "parfocality" i.e. the distance of the EP's focal plane from the shoulder of the EP body where it joins the barrel. He gives either a positive (closer to the objective) or negative (closer to the eye) number in mm, where the higher positive numbers = better for my use case. It is not a perfect test of course, because the barrel is longer in some EPs which could potentially add optical length to the path.

Having now looked at a good number of EPs that he has reviewed including all the ones I own, it turns out that almost all TeleVue EPs have a significant positive number (in most cases, at least +6.5mm) - so I could basically solve my issue without deconstructing the tube etc if I just invest several K in a few Naglers 😂😱

It seems that EPs with about +3mm or higher parfocality *should* work in my system, so it is progress in that I have some reference data, but I don't know of anyone else measuring parfocality in this way. 

I will keep at it! 

[badhex]

Oh and one last thought - I have let's say, a fan theory, that the EvoGuide was actually supposed to be 250mm FL instead of 242mm making it F5 instead of F4.84, but for some reason (perhaps a manufacturing issue) the objective's FL became 242mm instead. This loss of 8mm would account for the minimal available in-travel, and my theory is supported by the instruction manual having a sticker over the FL spec, which originally said 250mm. Possibly the instructions were all printed up and ready to go, and the FL was later changed to 242mm. 

[ED Splitter]

Any excuse to buy a nice eyepiece is a welcome one. 
can’t wait to see pictures of the setup once finished. Scared to read the final bill. 

[badhex]

46 minutes ago, ED Splitter said:

Any excuse to buy a nice eyepiece is a welcome one. 
can’t wait to see pictures of the setup once finished. Scared to read the final bill. 

Agreed! However, at the present moment TeleVues are definitely outside my financial reach 😅

I would quite like to try a T6 Nagler, but I had envisaged this travel kit to be a lower cost alternative to something like the Borg 55FL so although it works from a weight perspective, not sure it would be in keeping with the projects budget! 

I'll post a picture shortly of the current setup. 

[badhex]

This is the current status:

The MaxVision is a bit too big for it! As you can see below, there is always a bit of the EP barrel visible due the inner lip I mentioned. 

I've also found a source for tube rings that fit flush to the tube adn attach to a standard dovetail, so I'll be able to cut down the awkward shape a bit as well as save a few hundred grams by removing the block etcm in this picture. 

[badhex]

Quick update. 

I've found a potential EU source - Adriano Lolli in Italy - for custom camera/telescope adaptors, so I'm waiting to hear back from them on possibly making a custom M53x0.75mm - T2 adaptor. They already have one that is M52 so I am hopeful. 

With that in mind I wanted to be absolutely sure it *is* M53x0.75 so I bought a strap wrench and thread gauge to check, and it is as expected. 

Whilst I was at it, I did some additional measurements in case anyone else needs them in future. 

Objective cell is M56x0.75 (female) 

Focuser is M53x0.75 (male) 

Thread depth on the focuser end of the tube (M53x0.75 female) is 8mm

Focuser optical length (min.) is 43mm

 

So, assuming I can adapt to T2 I also did a bunch of research on what should be next in the optical path. A couple of standard T2 extensions would be the easiest, but I'd have to spend some time getting the length right so that the focusing EP holder has enough travel to accommodate the EPs I want to use. 

I've also found these two options which would give me the most flexibility:

Variable T2 extension from TS-Optics

 

Non-rotating version (which is identical to the Borg T2 focuser I might add) 

 

Obviously the non-rotating version would be best but it is 70eur vs 35eur for the rotating version. I guess I'll wait and see what the custom adaptor might cost and take it from there! 

Edited November 4, 2022 by badhex

[badhex]

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:

[badhex]

The new non-adjustable rings arrived yesterday so I set about installing them in the existing dovetail bar. 

I'd be lying if I said a was super happy with the quality, but it seems that options are limited for rings of this size. At least one of the screws was several mm than the others (in fact onyl two were the same length) , the threads on the rings could be a bit cleaner and there's no felt or similar inside the rings. They are also not quite perfectly circular, only clamping the tube at the top and bottom and not the sides, so I decided to put three pieces of self-adhesive soft rubber foam at 60° angles inside each ring to distribute the clamping force and provide a bit of protection. 

As you can see, they do not sit quite flush when screwed down. This was already the case before I added foam, but I'd rather have the foam there even if it slightly exacerbates the situation. I might try to get some felt, and try that, or alternatively black nylon washers/spacers for the aesthetics between the rings halves. 

I had hoped that the rings would attach directly to the green dovetail to minimise size and weight, but the holes are tappe to fit the existing flat plate, so I would need to drill the flat plate and use ¼" bolts to screw into the green bar, which I would have to order specially (metric only in German hardware stores!). 

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. 

Edited November 3, 2022 by badhex

[RT65CB-SWL]

I have purchased a few items via Adriano Lolli's website as well... https://www.adrianololli.com/ and very pleased with them.
I am also subscribed to his YouTube channel... https://www.youtube.com/user/lolliadriano

He may be the saviour/solution for me, as I need a set of 'custom' tube rings for my 're-modded' ETX105, as the diameter is 124mm.

The alternative is a pair of rubber lined 122 to 127mm Munsen rings.

At the time of writing/posting, the dovetail bar is secured by a pair of rubber lined Jubilee/hose rings, as shown in the image above.
 

[badhex]

5 minutes ago, Philip R said:

I have purchased a few items via Adriano Lolli's website as well... https://www.adrianololli.com/ and very pleased with them.
I am also subscribed to his YouTube channel... https://www.youtube.com/user/lolliadriano

He may be the saviour/solution for me, as I need a set of 'custom' tube rings for my 're-modded' ETX105, as the diameter is 124mm.

The alternative is a pair of rubber lined 122 to 127mm Munsen rings.

At the time of writing/posting, the dovetail bar is secured by a pair of rubber lined Jubilee/hose rings, as shown in the image above.
 

Yes, I'm very hopeful that this M53 adaptor works out!

In my case the tube rings I got were Lacerta - perhaps in the future I will contact Adriano about some custom tube rings as well!

[badhex]

Bit more progress today. Drilled (or enlarged) the holes on the tube ring adaptor plate necessary to bolt it direct to the dovetail without the need for the large adaptor block. 

Tested it with a couple of spare ¼" bolts which were juuust a few hairs shy of the tube but got some countersink head ¼" bolts arriving tomorrow anyway. 

The lower profile looks great and shaves a bit of unnecessary weight off.  

[grjsk]

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

[badhex]

8 hours ago, grjsk said:

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

Thanks! Yes, it's a bit niche. Do any of us really ever have a need for anything astronomy related? 😅

Edited November 5, 2022 by badhex