markse68
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Posts posted by markse68
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Couple of other pretty telescopes i’ve come across on the interwebs:
from a French artist Jacques Civetta a beautiful futuristic bino-dob:
And from a Swiss artist the Spherae “dob” https://www.spherae.ch/english in walnut laminate:
Mark
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I’ve been contemplating building a diy blower to defog my ep as i’m finding if i take a break from observing i have to endure a period where the ep is fogged as it has cooled and the humidity is so high at the moment. Which is a bit of a pain. But I had a look around and it seems that we’re getting spoilt for choice on new high performance rechargeable blowers. There are a lot of generic computer duster blowers on amazon quite cheaply but a couple stood out- the Kica looks a really nice very high power blower that i’m sure would clear an ep fogging in seconds but at a price:
https://www.kica-tech.com/en/kica-jetfan
Then there’s a very compact unit from Nitecore - the blowerbaby , designed as a replacement for the rubber bulb blowers used for dusting lenses, but again at quite a price:
https://www.nitecore.co.uk/products/nitecore-blowerbaby.html
Anybody have any experience of these or similar? They’re not heated but I think a strong blast of air should clear fogging anyway? I guess putting the ep in a pocket to keep it a bit warmer would also work but i worry about pocket lint and dust creating worse problems…
Mark
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Yes cloud dodging seems to be the order of the day- I shall do my best to get out as often as possible this week so long as it’s not hammering down. I have a large bin bag to throw over the scope should there be a light shower. I think light cloud can make a useful brightness filter- observing last night as thin cloud crept across the view the gradual dimming seemed to help the details show a bit better at times. I need to get a blower to demist the ep though as any break from viewing always results in fogging, the humidity is so high.
Mark
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Had a quick look tonight between clouds with my 150p and it was indeed looking good- at around 200x the distinctive form of Syrtis Major well defined, a lightening where Hellas should be and quite clearly defined N polar cap- first time I've been able to resolve it this time round.
Mark
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1 hour ago, Ratlet said:
I'm probably going to get banned for this, but I've always thought Taks looked cheap. Not a fan of the colour scheme, although I do love the mewlon. It looks like something from Battlestar Galactica.
Haha 😳 that’ll go down well! but bravely honest! I’m no Tak fan boy in general (mainly cos i can’t afford one
) but they’re bought for looking through mainly i think. I do like the look though- it’s not just slung together and there’s a retro futuristic thing going on that appeals. I just like this one as it goes really well as a combo with the mount- to my eyes anyway
1 hour ago, Sunshine said:my eyes struggle with reading the decals but this just screams Tak, I have no idea what model this is but I agree it looks really nice!
it’s a Teegul- i think it was really meant as a spotting scope but they were short lived i think, probably not great optically but visually interesting I think this is a 150 but they did a 60 and 100 which look nice too
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I want one of these just for its looks- mount and all
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Strange- might be worth updating to latest version
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that's a beauty!
Mark
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Tell me more about that sexy looking vintage tripod. And that stool- nice setup!
Mark
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1 hour ago, discardedastro said:
Please take this as the compliment that it is intended to be: you are quite insane. That's magnificently mad!
Mind bogglingly awesome! How reliable is it @windjammer? Imagine finding any connection issues must take a bit of headscratching!
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5 hours ago, DaveL59 said:
Have fun. I used spray hammerite when I did the little TAL-M a couple years back, found it helps to warm the metal a little before spraying as well as use several thin layers than try for a good coating off the bat - less paint runs that way. Think I used several cans doing the OTA and pillar but it looks much better for it. One day I'll treat the TAL-1 to the same but that's still in reasonable shape compared to how battered the paint looked on the M.
I’ve noticed most of the Tal-Ms that come up for sale tend to be in rough condition yet a lot of Tal-1s look pristine! I guess they were bought for kids more and got a lot of use whereas the Tal-1s are a bit bulkier to setup and went in the loft after a few goes
Mark
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What a fantastic opportunity! Do you think you’ll get a chance to point it at things of your choice too out of hours?
Mark
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Telescope Express have a few options
Mark
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Been playing with other eps that reach focus and this Nagler 7mm has I think a pretty flat field. Enough magnification to see banding on Jupiter and rings of Saturn quite clear and sharp. Without the FF there was slight distortion of Jupiters disk at the field stop and the banding was smeared to unobservable. With the FF there was same slight egg shaped distortion but the banding remained quite clear. I think the disk might have been a tiny bit sharper in the centre of fov without the FF though but not much in it.
So i think with a good enough ep with itself a flat field the FF is probably worthwhile though the view was perfectly acceptable without.
Mark
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Some rubber retained spotting scope caps arrived today- much better than the silly metal cap supplied with the 50ed for an active finder scope I think
Mark
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15 minutes ago, HollyHound said:
Heavy yes, but almost the same weight as the XW30 and XW40, and also all 2”… this could be the start of a fantastic matched set 🤔
yes I am going to have to start saving
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Thanks Don, just checked a plossl that calculated by Globs method comes out at 55deg and using the flashlight method 57.4deg
Mark
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Totally over the top this but I managed to pick up a second hand 50ed for a reasonable price so why not. The classic SW 9x50 RACI is surprising good for the money- nice and light and compact, bright and sharp but having looked through the superb Tal 9x50 straight-through finder I really fancied something like that but with a right angled eyepiece. The SW RACI is advertised as 45 AFOV, the Tal 55deg and it really makes a difference to the viewing experience.
Trouble is the 50ed has quite a short back focus even with its extension tube removed which doesn't leave much space for a star diagonal to still reach focus.
I had a Baader T2 prism diagonal already and wasn't using it much- it's the cheaper one (not the Zeiss) and spec'd at 35mm physical "length" and 32mm glass path which I think means its effective length is 32mm as it shifts the focal plane backward by 3mm.
Using a Baader ultra short 1¼" eyepiece-clamp I tried a few eps and struggled finding the right one that would reach focus. My 19mm TV Widefield does and is nice but would give a magnification of ~13x a bit too high. None of my 24-25mm plossls would reach focus.
Then I remembered I had a rather peculiar Tal 25mm plossl from a Tal-M scope. It's the same optics but much shorter than the standard Tal 1.25" plossl putting its field stop close to the end of its barrel. But the barrel is 32mm diameter so wouldn't fit the Baader clamp. As it happens I think it's the same plossl optics in the lovely Tal finder too.
Couple of weeks later and a couple of ebay T2 eyepiece holders arrived direct from china- a bargain at £3.99 each. I skimmed the bore to 32mm and had to shorten it by about 1mm but now I could fit the Tal plossl to the new finder.
The peculiar plossl had a 21mm field stop but the one in the Tal finder and the 1.25" plossls I have are 24mm. This would have meant an AFOV of only 48deg vs the Tal finders' 55deg so I ordered some o-rings the correct size to replace the metal field stop with.
The view through this finder is very similar to the Tal now- identical eyepiece and all. Same nice big 55deg AFOV, slightly higher magnification at ~9.7x. They both have a similar amount of edge of field distortion but strangely it is different. Stars stretch into arcs at the field stop in the Tal finder but are stretched to radial lines in the 50ed. Nothing too bad though and the larger AFOV is just nicer to look at than the Skywatcher. The ED glass should give better colour I guess and less chromatic aberration but the Tal is really very sharp and the colour pretty good at its low magnification.
It's not RACI though. I might look into fitting an Amici prism at some point but it would involve seriously shortening the tube by removing the nice helical focuser of the 50ED and would need to be quite a large prism anyway to cover the larger field stop. The SW wins here.
When I bought the 50ed it came with a Starizona Evo-FF2 field flattener meant to improve it as an imaging scope. I need to play with it some more but am not seeing a great improvement visually but then it's probably swamped by the edge of field distortion anyway. A Panoptic 24mm would be a better eyepiece- larger field of view, better edge correction and there maybe the field flattener would be appreciated but I don't have one and buying one for a finder really would be a bit OTT!
Is it worth it and will I use it? Not sure yet- it is nicer to look through than the SW but it's still just a finder...
It's bigger and heavier than the others- twice the weight of the SW! It doesn't fit in the case I use currently for the SW finder and bracketry either... Time will tell
Mark
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25 minutes ago, globular said:
If there aren't too many distortions produced within the eyepiece then the following formula works well:
field stop 180
------------- x ----- = FOV
focal length πThanks Glob, that seems to give realistic sounding values 👍
Mark
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19 hours ago, Don Pensack said:
Let's do the math.
Hi Don, off topic sorry but is there a way to calculate the afov of an eyepiece given the field stop and focal length?
Mark
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29 minutes ago, Don Pensack said:
More of concern is that though they give a 20mm eye relief from the glass, they are stating only a 12mm eye relief from the rubber eyecup, ruling out glasses use.
If there is a way to modify the top and change the eyecup to yield more eye relief, then they would be sold to glasses wearers.
They look like they will have the same removeable top section as the other XWs so probably have the 43mm thread that a TV Dioptrix could be mounted to?
Mark
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8 minutes ago, SthBohemia said:
After looking as closely as I could via your photograph as posted a few slots ^, am I correct in thinking that the medium of the mirror has inclusions of 'bubbles'??
most pyrex blanks do 🤷♂️
Mark
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Interesting! Yes hopefully they’ve addressed the common complaint about fc
Mark
edit- of course they did
“The new eyepieces feature a new optical system with 7 elements in 5 groups that surpasses the performance of the conventional XW series to obtain sharp star images all the way to the edge of the field of view.”
from the same press release they’re aiming squarely at us astro users too (rather than spotting scopes) This makes me happy as I feared Pentax (Ricoh) had abandoned us
“The new smc PENTAX XW16.5 and smc PENTAX XW23 deliver an apparent field of view of 85° -- the widest viewing angle in the XW series, suitable for observing nebulae and star clusters.“
They’re huge though- heaviest in the lineup but i guess that was to be expected.
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) but they’re bought for looking through mainly i think. I do like the look though- it’s not just slung together and there’s a retro futuristic thing going on that appeals. I just like this one as it goes really well as a combo with the mount- to my eyes anyway 
Blower for de-fogging eps/secondary mirror
in Discussions - Eyepieces
Posted
That looks like one of the more generic ones on Amazon Don- certainly looks up to the job of blowing dust. I guess part of my question is a physics one- will blowing cold saturated air at a cold eyepiece actually evaporate the fogging or does it need to heated? I think it will as blowing air on a wet hand cools by evaporation and from your description of the folded fan it does?
Mark