Hyperion v BST

[sticks]

Has anyone got a Baader Hyperion EP and a BST EP in their collection and how do they compare?

[rwilkey]

Hi sticks, I have both in my collection and have to say it's a hard call because the quality of the BST Explorer is so incredible, so what are the differences? Well, the Hyperion has a wider FOV, 68 degrees compared to 60 degrees in the BST, the Hyperion is modular which means you can alter the focal length by using the Fine Tuning Rings (often referred to as FTR's, example: you can change an 8mm to a 5mm by using the FTR's). All the BST Explorers (based on the Astro-Tech 'Paradigm', see review here: Paradigm Dual ED) are fixed focal lengnth but I love them, great for planetary and lunar studies, whereas the Hyperion also doubles for deep sky in the longer focal ranges. Really it is horses for courses, but at the end of the day the BST's are smaller and more compact and pack a powerful punch for thier cost. I would choose the BST Explorer every time!

[chesty]

hmm definately food for thought in my search for 2 new ep,s

[Pug]

I've no experience of the hyperion but can vouch for the BST's. After researching here and other online sources, Robins website being one of them, I recently bought an 8mm and an 18mm (I don't get on with barlows) and I'm REALLY pleased with them.

Another thanks to Robin for his input!

[faulksy]

as said by rwilky they are very good. i have a 8mm and a 9mm bgo and only the very slightest difference in performance but not a lot also the bst has great eye relief

[sticks]

Thanks v. much rwilkey I just caught your eyepiece guide page at Swindon Stargazers - a great help. I have a 25mm plossl that came with the scope and a 15mm BST that I can use OK in my MAK 127- the 9mm plossl that came with the scope is useless. I now want more power but with NVG seeing I think 12mm is probs as far as I can go. At the other end I want to see as much of the limited FOV the scope gives without going into 2" EPs. What would you recommend? After your comments above I was going to order a 12mm and a 25mm BST...? But you also seem to say that a hyperion would be better for "deep sky"..........

[rwilkey]

Hi sticks, the BST 25mm is the runt of the litter, I am afraid, so that leaves the Baader Hyperion 24mm, which in most scopes gives a good account of itself, I have not tried it in an SCT but I should imagine it is very good, it's only in fast scopes that it doesn't excel, like my f/5, but OK in long focal ratios f/6 and above. Note that the FTR's cannot be used with the 24mm Baader Hyperion.

[Adrian]

I don't know if anyone else has noticed, but the 18mm isn't 18mm

I compared it to an 18mm BGO recently and Jupiter was noticeably smaller in the BST.

I thought it might be an optical effect caused by the different AFOVs, but over the weekend I was testing my SCT to calculate the focal length using all my eyepieces and the 18mm BST consistently gave a result of around 10% shorter FL(Scope) meaning a longer eyepiece FL as the FOVs of the 12 & 18 are not particularly different.

(The Omni 32mm plossl gave results consistent with a shorter eyepiece focal length)

I really liked my 8mm hyperion - in my previous scope (900mm focal length) it was really useful for planetary, using the FTRs to get the best magnification for the seeing. Unfortunately it was no use for my current scope - I have been considering selling my two BSTs and getting a 17mm hyperion instead...

[sticks]

Thanks again - I asked Alan at STL whether the 12mm would be sufficiently more high power than the 15mm I already have and he doubted it would (what a guy eh!) so I am now thinking I need between a 9 and a 12. At the other end I need to get near the 1* approx FOV of the scope.

So I am now thinking of a Hyperion at 21mm which gives a TFOV of 0.958* on my scope and barlowed would give me a 10.5mm. With FTRs it would provide more possibilities but I am worried about how much glass I would be introducing....

So a Hyperion 21mm and a Tal 2* barlow - what do you think?

[Stephen]

The FTRs don't contain glass so there's no extra there! They are just spacers.

If using Barlows was a "really" bad thing, no one would

[rwilkey]

I think the 21mm will be a good compromise, with the FTR's that would make a good range. Don't worry about too much glass, none in the FTR's, bit of a falacy in my view, the Hyperions usually Barlow very well, though they have a built in barlow as part of the lens groupings, throws out the eye relief a bit, but still OK.

Also Adrian, comparing a BGO narrow FOV with the huge eye lens on the BST Explorer would show a seemingly smaller planet, though I do not argue with your results, but very interesting I believe, I will look closely at the 18mm when I am next out.

[Damo636]

The only problem i foresee is that the 20mm eye relief of the Hyperion will be pushed out to an uncomfortable distance with the introduction of the 2x barlow. Another thing to be aware of is that the afov of the 21mm Hyperion is nearer to 60* so a lot of users skip this fl and opt for the 17mm instead which has the full 68* fov and the added bonus of a darker sky background due to the higher mag.

[Adrian]

I would also go for the 17mm - with FTRs gives 13.2mm, 10.8mm & 9.2mm - a nice range in your scope, and the 15mm BST sits between the first 2 lengths.... or you can sell it to fund the difference.

.

Also Adrian, comparing a BGO narrow FOV with the huge eye lens on the BST Explorer would show a seemingly smaller planet, though I do not argue with your results, but very interesting I believe, I will look closely at the 18mm when I am next out.

That's what I had accepted the cause of the apparent difference to be, but then the data I collected implied the same: that it is a longer focal length (the alternative is that the AFOV is actually 65 degrees, but I think that would be a more noticable difference ).

The full data/calculation is in the excel spreadsheet attached to this thread:

http://stargazerslounge.com/discussions-scopes-whole-setups/162625-sct-focussing-changing-focal-length-some-data.html#post2096062

Of course, that is just my sample of the 18mm BST Explorer (& 32mm Omni Plossl)