markse68

17 minutes ago, upahill said:

Out of curiosity do these suffer from the same delay problems as mentioned earlier?

They’re pretty fast acting I think as fuses go

6 minutes ago, fifeskies said:

wired inside the box is a tad inconvenient compared to a panel fuseholder on the outside where a few seconds lets you change a fuse

Not really- they’re thermal fuses that reset when they cool down so don’t need changing though they do degrade if activated too often. They don’t completely break the circuit but limit the current to a safe level

Polyfuses are cool for short circuit protection- just wire in series with outputs inside the box- should be there from the manufacturer really 

https://www.ebay.co.uk/itm/1-1A-1100mA-RGEF110-UF110-Resettable-Fuse-30V-PTC-Polyswitch-Polyfuse-12v-Z346-/323820428730

Caught in passing car headlights- first light for dob upgrades. This was second outing last night after having had to go home and hairdryer the primary which was soaked in dew along with everything else. Didn’t realise how handy having a door in the tube actually is till then!

Turns out a remote focuser is a really useful and enjoyable luxury! More than I’d imagined 

Moonlite finally fitted so a 2” case was needed

That’s what it looks like tbh 😂

not very convincing 🤔🤣 

It really doesn't look real but it's an amazing view- would like to see more of these!

Shame about the green fringe

Thanks John, yes I’m keeping my eyes peeled for the other members of the TV WF family but they don’t seem to turn up very often these days- particularly the shorter focal lengths. I don’t think the Tal is the greatest plossl optically but I love its wide afov and find myself reaching for it every time I get out with the scope- it’s a favourite.  I have a feeling the military ep will be another 😉

Too early to say really- I think if you have a fancy wide-field wide angle ep already  then only if you’re into curiosities, but if you’re after a cheapish very wide angle ep probably similar to say a 55mm plossl but with very ergonomic eye placement then it might be worth a punt? Steve at ENS says he uses them for outreach as they’re so user friendly and you’re not going to worry too much about kids mucky fingers on the lens 😉 It’s the widest view ep I have (tying with the TV WF 40mm but I’m not lugging that around- beautiful though it is- so I’ll be using it for the time being 👍

@Stardust @dannybgoode I made a new post comparing this ep to some others- 

Mark

I should preface this by stating these are just some observations from me- I’ve only been in this hobby this past half year or so and am no eyepiece or optical expert- I have very little experience of eyepieces, particularly high end ones and  I’ll probably even use the wrong terms. And this is based on about an hour comparing these eps in daylight on terrestrial targets. Eyepieces compared in my 8.75” f7.3 dob.

I finally yesterday finished major upgrade to my dob which included fitting a 2” moonlite focuser. Over the past 6 months I’ve been collecting a few 2” eyepieces in preparation for this momentous event! 

So today I had first chance to try them and compare. From left- Tal 25mm Plossl (1.25” reference ep), mystery military ep of unknown fl, the intriguing Siberia Erfle 50mm (available from ENS), TV WF 32mm, TV WF 40mm

My target was the HSBC building, 1.3miles from me and useful for comparing  actual field of view by counting visible window panes across the afov. This is the actual view through the Tal 25mm plossl. Mine has an unusually (for a plossl) large afov of 60deg.

Mystery military  EP

Been dying to try this ep since I picked it up on eBay for £20 as it seemed to have a huge afov- similar to a Nagler! Early observations suggested it  had an orthoscopic characteristic with very low rectilinear distortion but how did it perform in my scope? Well I like it a lot. It seems to compare in magnification to the Tal plossl so I think it’s a 25mm too. The field of view is huge, the image very sharp in the centre and colours neutral. There is no noticeable rectilinear distortion- the frames of the windows appeared perfectly straight across the field of view though I’m not sure how important that is in astronomy 🤔. Downsides were it loses focus right at the edges but it wasn’t the worst offender for that. It also shows a colour fringe at the very edge but that’s so far out it’s not offensive. In terms of actual fov (counting windows) it matches the TV WF 32mm. In terms of ergonomics this was the second best- it was very comfortable to view through and eye placement was fairly easy though it was possible to get blackouts if you moved too far off axis

Siberia Erfle 50mm

I stumbled across this on eBay and purchased it from ENS for what seemed a reasonable price given it’s new old stock and quite unusual- possibly manufactured by Tal but branded Siberia. It’s a very physically long ep but remarkably light for its size- significantly lighter than the TV WF 40mm! I’d read others commenting that they couldn’t reach focus with it in their scopes and it turned out it needs 15mm in-focus to reach its focal plane. So I made sure when designing my upgrades to allow 20mm in-focus from the primary focal plane. This ep has afov comparable to a TV plossl, so about 50-55degrees I think. That makes it the narrowest afov on test. It has a slight but noticeable yellow caste to the image- a vintage tone. It has a lot of rectilinear distortion (pincushion) though comparable to the Tal plossl. It is the worst on test for edge loss of focus. Doesn’t sound very good... But it has the easiest eye placement of the eps on test! And it has the same actual fov as the TV WF 40mm, yet is much lighter than that lens. And it’s available to buy new! (very limited stocks though I believe). I think I’d rather carry this around with me than the TV WF 40 (which is a lump!) but I need to use them both properly first to evaluate.

TV WF 32 and 40mm

these shared common characteristics. They have the same afov of more than the Tal plossl but less than the mystery military ep- so maybe 70deg? They have a lot of pincushion distortion but are pretty sharp to the field stop. They were also the worst for eye placement with the 40mm being the worst. Seeing the whole field sharp was really tricky on the 40mm but I wonder if that will improve at night with larger dark adapted pupils? I think this has something to do with exit pupil size.

Mine is quite a slow scope so I’m not sure coma would come into this (I’ve not knowingly seen coma yet anyway) but will update if this should become apparent under the stars.

Mark

I’ve been busy on a major upgrade for my old banger for what seems like absolutely ages... but tonight it’s finally come together! It all started with wanting to swap the 1.25” focuser for a 2” and finding a Moonlite at a good price cemented that idea.

But then I decided if I was going to do that I should swap out the secondary as the old one had a poor surface and I reckoned it could be improved on.

And if I was going to do that I really needed a new secondary mount/spider as the old one while quite nice in principal was the wrong size...

Then I saw someone with a manual motorised focuser and that seemed like a good idea but I figured making my own would be the impetus I needed to finally learn Arduino...

So after many moons I’ve finally ended up with a nice 2” focuser with stepper focus motor (will finally be able to try out that Siberia Erfle @Stardust 😉)

And a beautiful new Protostar quartz secondary mirror in a new mount and spider

Now I just need some clear skies for its first light

Trouble is- it doesn't feel like an old banger anymore 🤦‍♂️ I’ll be gutted the first time I clonk that moonlite loading it into the car- think I need to make some sort of protective cover

10 hours ago, johninderby said:

I also have one of these although it’s started having problems with clamping the eyepiece as the jaws aren’t closing evenly... Maybe taking apart and cleaning needed? 🤔

Has one of the jaws jumped a “tooth” on the scroll thread John?

23 minutes ago, adyj1 said:

I have one of these, and it was really effective with my Skywatcher 25mm, but wasn't the right distance from the eyepiece to focus with my 10mm SW ep (and I couldn't adjust the distance). 

It is extremely good value, but if you don't get good results with the first eyepiece you try, make sure you have a go with any others you have.

Good luck! 

Ady 

Thanks for the tip Ady- it’s a terrific design with the chuck jaws to grip the eyepiece and I couldn’t believe all the threaded parts are brass inserts- incredible for the money! 

Its also perfect for microscope-phone-photography 👍 (random pic of a Wago connector up close I took earlier trying it out 😉)

Possibly the most useful £3 spend yet 😉

39 minutes ago, rorymultistorey said:

Pics of the secondary assembly ( i hope) 

Thanks very much Rory- what a quirky and interesting design! Looks great! I wonder what kind of ribbon it is- you'd think it'd stretch and loosen over time? Guess not- looks pretty taught. Does it hold the secondary solidly?

Agree on it being a much nicer mechanism than the simple 3 screws

1 hour ago, rorymultistorey said:

The mechanics of the secondary holder is (IMHO) brilliant

Hi Rorymultistorey, got any pics? 

Could it just be the laser collimator shifting in the ep tube?

9 hours ago, FLO said:

A photo of the StellaMira 104 ED2 Triplet refractor: 

I was looking at that handle thinking it looked a bit uncomfortable until I realised it’s a picatinny/weaver rail for a rdf- nice touch 👌 

I wondered why there weren't many harmonic drive mounts about. I guess price and maybe torque ripple- though with decent control that shouldn’t really be an issue? And now the Chinese are making decent quality ones since the patent expired they seem ideal 👍 Surely you’d want to balance it though- they’re backdriveable and the motor’s going to be taking the load? 

On 09/11/2019 at 16:20, vlaiv said:

Not sure about that one. In classical interpretation of gravity hollow sphere (or any other shape) will not have gravitational field inside as gravitational influences of small pieces all cancel each other out perfectly. Have no idea what would be the case in GR though.

Does gravity really cancel out like that? So in this classical interpretation you could float out of the zero gravity interior of the hollowed out planet through a tunnel that the excavators had conveniently left and instantly feel normal gravity when you emerged onto the outer crust? 

Really puts the hugeness of our star into perspective- such a tiny planetary spot compared to say Io’s shadow on Jupiter! But then you see this 😳

Don’t know the answer to your question except increasing secondary obstruction reduces contrast I think 🤔 

Protostar have 1” quartz mirrors

https://www.fpi-protostar.com/quartz.htm

edit- out of stock 🤦‍♂️

13 minutes ago, johngm said:

Also you have the added advantage of aluminium of being lighter. This is my input, but would be interested in others views on this subject

And it won’t rust of course

I bought a lilo footpump from Tesco’s during the summer. Yet to use it in earnest but hoping it’ll do the trick. Need to make a fine nozzle for it first though. I reckon it should give a good high pressure jet of air for sustained blowing of dust, I don’t really like the little hand squeezy blowers and like you say the cans have a habit of squirting liquid content. It’s got a nice long tube so should be pretty dexterous. No idea about that powered blower though it looks a bit ungainly 🤷‍♂️

3 hours ago, Ships and Stars said:

Haha, figured it was someone on here. Thank you very much! Can't wait to use it. The OIII is my fav all-around filter, the Veil is wonderful!! Hope you get to see it. We might have some clear skies here tomorrow night for a bit. I'll believe it when I see it! Thanks again! 👍

No don’t thank me- I was bidding against you (I think) 😬 Glad it went to a good home though 😉

Mark