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city viewing (1 Viewer)
- Thread starter opus914
- Start date
Hi,
First of all, welcome to Birdforum!
To see details at 10miles you would want at least a spotter, maybe even an astro scope, depending on your portability requirements. Over water the seeing should be fairly good.
On the other hand some nice bins will also get stuff closer, but you will still see a city and not one house. And of course bins can be taken on a walk...
Your typical 8x pair of bins with a 130m field of view at 1km will show you 1.3 miles of shoreline at 10 miles, a 10x pair with 100/1000m will show a mile and a spotter with a 30x wide EP will show 41/1000m or 720 yards at 10 miles, the same scope with a 20-60 zoom at 60x will show 17.5/1000m or 305 yards at 10 miles.
So what are your portability requirements and what is the budget?
Joachim
First of all, welcome to Birdforum!
To see details at 10miles you would want at least a spotter, maybe even an astro scope, depending on your portability requirements. Over water the seeing should be fairly good.
On the other hand some nice bins will also get stuff closer, but you will still see a city and not one house. And of course bins can be taken on a walk...
Your typical 8x pair of bins with a 130m field of view at 1km will show you 1.3 miles of shoreline at 10 miles, a 10x pair with 100/1000m will show a mile and a spotter with a 30x wide EP will show 41/1000m or 720 yards at 10 miles, the same scope with a 20-60 zoom at 60x will show 17.5/1000m or 305 yards at 10 miles.
So what are your portability requirements and what is the budget?
Joachim
The-Wanderer
Well-known member
Heat haze and other effects may limit the detail you can see
Hi opus,
For ten miles.
Firstly you need the Sun behind you or at least to the side.
You need height to avoid mirage.
At 60ft height the sea horizon is 10 miles, but you need higher and the city objects also need height.
The temperature must be stable with the sea, land and air temperture the same if possible.
Then clean transparent but stable air.
Mornings and evenings best. Most place are better spring and autumn. Don't know about your location.
I suggest a 120mm f/8.3 astro refractor and powers up to 100 or more.
At 3 a.m. I could see 1 inch marks on a clock face at 4.7 miles at 250x.
High quality 120mm f/8.3 doublet refractor.
10 miles is a serious distance.
There must be no heat sources in the way.
Grass and vegetation not asphalt concrete.
An alternative is perhaps a Celestron C8 or 6 inch Maksutov.
The ideal would be a seriously large long focus refractor. 6 to 10 inch aperture f/15. Very heavy.
A 100mm ED refractor would I think be the minimum, but not really large enough for small objects.
If viewing from indoors good window glass is needed and no central heating in viewing room.
For ten miles.
Firstly you need the Sun behind you or at least to the side.
You need height to avoid mirage.
At 60ft height the sea horizon is 10 miles, but you need higher and the city objects also need height.
The temperature must be stable with the sea, land and air temperture the same if possible.
Then clean transparent but stable air.
Mornings and evenings best. Most place are better spring and autumn. Don't know about your location.
I suggest a 120mm f/8.3 astro refractor and powers up to 100 or more.
At 3 a.m. I could see 1 inch marks on a clock face at 4.7 miles at 250x.
High quality 120mm f/8.3 doublet refractor.
10 miles is a serious distance.
There must be no heat sources in the way.
Grass and vegetation not asphalt concrete.
An alternative is perhaps a Celestron C8 or 6 inch Maksutov.
The ideal would be a seriously large long focus refractor. 6 to 10 inch aperture f/15. Very heavy.
A 100mm ED refractor would I think be the minimum, but not really large enough for small objects.
If viewing from indoors good window glass is needed and no central heating in viewing room.
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Not concerned about portability. Budget is flexible, though I'd prefer to avoid a second mortgage.
The best spotting scopes seem to be a Swarovski 95 with one or two extenders or a Kowa 88 and similar.
Maybe $5,000? new.
However, a trip to a good local astro dealer would probably allow better available views. For less money. Although one could easily spend $20,000 on an Astrophysics 7 inch rrefractor and mount, even secondhand.
The mount is as important as the scope and must be a heavy astro, perhaps altazimuth, Skywatcher AZ5?
I would think a suitable scope and mount might be $1,000 to $3,000.
Astro scopes are not waterproof.
A fixed pillar mount would work.
The reading of the weather and atmospheric conditions is much more important than the scope. But the scope must be big enough and of high quality.
Secondhand scopes are very good value if one understands how to appraise them.
But a good astro scope would show cars and people at ten miles in very good conditions.
I have been making observations at ten miles or more since the 1950s using telescopes up to 12.5 inch aperture.
Maybe $5,000? new.
However, a trip to a good local astro dealer would probably allow better available views. For less money. Although one could easily spend $20,000 on an Astrophysics 7 inch rrefractor and mount, even secondhand.
The mount is as important as the scope and must be a heavy astro, perhaps altazimuth, Skywatcher AZ5?
I would think a suitable scope and mount might be $1,000 to $3,000.
Astro scopes are not waterproof.
A fixed pillar mount would work.
The reading of the weather and atmospheric conditions is much more important than the scope. But the scope must be big enough and of high quality.
Secondhand scopes are very good value if one understands how to appraise them.
But a good astro scope would show cars and people at ten miles in very good conditions.
I have been making observations at ten miles or more since the 1950s using telescopes up to 12.5 inch aperture.
Hi,
if portability is not a concern, astro equipment will indeed do the trick a lot cheaper and probably better than a top tier spotter like the Swaro ATX 95 or the Kowa 883.
As has been said, the mount and tripod is important and should not be skimped on - the SW AZ5 should be regarded as a minimum for a scope of 100mm aperture or so (mainly due to the tripod) but it has a worm drive and can be adjusted by turning some knobs - which might or might not be your cup of tea.
A bit above the AZ5 would be an Explore Scientific Twilight 2 - this one can carry seriously big and heavy scopes if you're so inclined and has no knobs - you just adjust the friction and then push the scope whereever you want.
As for what to get - if I was in that situation I'd get an ED doublet of 100mm or above (SW 100ED or 120ED are nice options) and probably a baader zoom (maybe the kit with the barlow lens). That would give you 38-113x without the barlow and 82-248 with the barlow lens (although you should mark your calendar when the seeing allows more than 120x during daylight).
Nota bene, astro scopes are commonly used with 90 degree mirror diagonals (the two SW scopes come with one) - so you look straight down into the scope when it's level and the image is upright but flipped around the vertical axis. So called Amici prisms are available that offer an upright and correct image - some even at 45 degrees which is more comfortable for terrestial. Unfortunately most tend to impair the image quality, so for best results a mirror it is...
If budget is really not an issue, there is also very nice big binocular options... a 120mm APM SD-APO would certainly also give good views and with both eyes too... but with a proper mount and some eyepieces that is way north of the 5k mark...
Joachim
if portability is not a concern, astro equipment will indeed do the trick a lot cheaper and probably better than a top tier spotter like the Swaro ATX 95 or the Kowa 883.
As has been said, the mount and tripod is important and should not be skimped on - the SW AZ5 should be regarded as a minimum for a scope of 100mm aperture or so (mainly due to the tripod) but it has a worm drive and can be adjusted by turning some knobs - which might or might not be your cup of tea.
A bit above the AZ5 would be an Explore Scientific Twilight 2 - this one can carry seriously big and heavy scopes if you're so inclined and has no knobs - you just adjust the friction and then push the scope whereever you want.
As for what to get - if I was in that situation I'd get an ED doublet of 100mm or above (SW 100ED or 120ED are nice options) and probably a baader zoom (maybe the kit with the barlow lens). That would give you 38-113x without the barlow and 82-248 with the barlow lens (although you should mark your calendar when the seeing allows more than 120x during daylight).
Nota bene, astro scopes are commonly used with 90 degree mirror diagonals (the two SW scopes come with one) - so you look straight down into the scope when it's level and the image is upright but flipped around the vertical axis. So called Amici prisms are available that offer an upright and correct image - some even at 45 degrees which is more comfortable for terrestial. Unfortunately most tend to impair the image quality, so for best results a mirror it is...
If budget is really not an issue, there is also very nice big binocular options... a 120mm APM SD-APO would certainly also give good views and with both eyes too... but with a proper mount and some eyepieces that is way north of the 5k mark...
Joachim
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Or if one wants to do a really good job.
APM/LZOZ 304mm f/7.5 Super Bino on supplied mount.
Binocular 400Kg.
Complete with mount 2000Kgs.
I saw about $300,000 mentioned, but if interested one should enquire.
I suppose it might take a year or two to make one unless one paid extra for superfast.
It might mean selling the house.
One could just go for half of the bino and get one of the scopes.
APM/LZOZ 304mm f/7.5 Super Bino on supplied mount.
Binocular 400Kg.
Complete with mount 2000Kgs.
I saw about $300,000 mentioned, but if interested one should enquire.
I suppose it might take a year or two to make one unless one paid extra for superfast.
It might mean selling the house.
One could just go for half of the bino and get one of the scopes.
Hi,
a bit more expensive, half a million euro including tax... but even if you have the cash you might not get another one... Markus Schumann of Binoptic, the guy who built the bino adaption for this has sadly passed away ealier this month....
http://forum.astronomie.de/phpapps/...641/das_Weltgro_te_Apo_Bino_ist_Fe#Post980641
Joachim
a bit more expensive, half a million euro including tax... but even if you have the cash you might not get another one... Markus Schumann of Binoptic, the guy who built the bino adaption for this has sadly passed away ealier this month....
http://forum.astronomie.de/phpapps/...641/das_Weltgro_te_Apo_Bino_ist_Fe#Post980641
Joachim
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Joachim,
Sorry to hear that.
Difficult to find another.
Zeiss built three 300mm binoculars on huge altazimuth mounts. c. 1940, but I don't think they survived.
Leitz built a huge photographic lens also.
There was a 250mm Japanese binocular, at least still there in a museum a few years ago.
Sorry to hear that.
Difficult to find another.
Zeiss built three 300mm binoculars on huge altazimuth mounts. c. 1940, but I don't think they survived.
Leitz built a huge photographic lens also.
There was a 250mm Japanese binocular, at least still there in a museum a few years ago.
Not to bring this telescope discussion down to earth, but ...
I apologize in advance to the OP, but I am going to assume that you have limited experience with astronomical telescopes or moderate to large sized spotting scopes. My experience advising friends and family, is that most folks over estimate the importance or utility of magnification, and underestimate size, weight, and transportability of a telescope with stable mount. And so I would ask some questions about where you intend to keep this telescope and how you intend to use it.
Is this telescope going to be a permanent fixture in front of a window or will it be brought from one room to another, or brought outside? In other words, in addition to the logistics of setting up, placing, and using the telescope, are there any aesthetic issues? Viewing the city at several miles is one thing, and reading the time from the Ferry Building Clock Tower at that distance is another. In just what ways are you seeking to enhance your view?
As magnification increases, there are a variety of issues that make using a telescope more challenging. Defects in the optics and the mount become more apparent, pointing the telescope becomes more challenging, and your view will go from panoramic to looking through a soda straw in terms of field of view. And particularly for terrestrial viewing, as others have indicated, atmospheric instability (usually referred to as seeing) will limit the detail you can see.
Binastro's view of 1 inch marks at five miles is at the theoretical limit of what that telescope can do, so I assume it is a case of exceptional optics (telescope and eyes) under exceptional atmospheric conditions. Terrestrial viewing is challenging because you are looking through so much atmosphere with many possibilities of disturbing the air. I wouldn't be thinking about 250x from the Berkeley or Oakland Hills looking at the city. BTW, perhaps Binastro would like to quote the weight of the telescope, mount and tripod used for that sighting.
I would suggest contacting a local astronomy club or local science center like Lawrence Hall or Chabot, and inquiring about telescope loaner programs or viewing opportunities during the day. I know that Lawrence Hall parking lot has an excellent of SF and SF Bay in general, so looking through a modest telescope or pair of binoculars from there could give you a better idea of what to expect at home.
Good Viewing,
Alan
I apologize in advance to the OP, but I am going to assume that you have limited experience with astronomical telescopes or moderate to large sized spotting scopes. My experience advising friends and family, is that most folks over estimate the importance or utility of magnification, and underestimate size, weight, and transportability of a telescope with stable mount. And so I would ask some questions about where you intend to keep this telescope and how you intend to use it.
Is this telescope going to be a permanent fixture in front of a window or will it be brought from one room to another, or brought outside? In other words, in addition to the logistics of setting up, placing, and using the telescope, are there any aesthetic issues? Viewing the city at several miles is one thing, and reading the time from the Ferry Building Clock Tower at that distance is another. In just what ways are you seeking to enhance your view?
As magnification increases, there are a variety of issues that make using a telescope more challenging. Defects in the optics and the mount become more apparent, pointing the telescope becomes more challenging, and your view will go from panoramic to looking through a soda straw in terms of field of view. And particularly for terrestrial viewing, as others have indicated, atmospheric instability (usually referred to as seeing) will limit the detail you can see.
Binastro's view of 1 inch marks at five miles is at the theoretical limit of what that telescope can do, so I assume it is a case of exceptional optics (telescope and eyes) under exceptional atmospheric conditions. Terrestrial viewing is challenging because you are looking through so much atmosphere with many possibilities of disturbing the air. I wouldn't be thinking about 250x from the Berkeley or Oakland Hills looking at the city. BTW, perhaps Binastro would like to quote the weight of the telescope, mount and tripod used for that sighting
. I would suggest contacting a local astronomy club or local science center like Lawrence Hall or Chabot, and inquiring about telescope loaner programs or viewing opportunities during the day. I know that Lawrence Hall parking lot has an excellent of SF and SF Bay in general, so looking through a modest telescope or pair of binoculars from there could give you a better idea of what to expect at home.
Good Viewing,
Alan
Hi,
I use my ED 100/900 quite often terrestially at up to 180x (albeit my farthest visible targets from the balcony are about 1km away - I only have a river and not San Francisco bay...).
Pointing and aiming is not a problem with my Giro III mount on a surveyor tripod and a Rigel Quikfinder. The whole contraption is probably 10kg or so and can be grabbed from its place on the bedroom window (also looking at the bird sanctuary at the other river bank) and put on the balcony in 30s.
Regarding apparent field of view (or afov), it's the other way around - since true field tfov (and thus apparent field which is tfov in deg * magnification - disregarding distortion) has an upper limit determined by the field stop size, low magnification EPs tend to have a smaller afov than high mag EPs - see for example the Televue Ethos series with 100 deg afov which tops out at 21mm, while the Panoptic series with 68 deg afov goes up to 41mm and correspondingly lower magnifications.
In any case, modern astro EPs have far greater afovs than your usual pair of binoculars or spotting scope zoom EP. When using the scope mentioned above at 180x with a 5mm Nagler, I can't see the field stop without moving my eyes - with the 9m ES 100 deg (Ethos clone) I have to move my head and the eye to see the field stop.
Joachim
Hi Alan.
I have 3 identical 120mm aperture custom made aluminium tube simple scopes. Grey enamel? It was cheaper to get three at the same time. No finders. I don't need them as I use a low power eyepiece if necessary to find stuff.
I had 2 objectives coated at my own risk. I left one uncoated in case the coating heat cracked the glass.
I also had a 110mm f/16 Fraunhofer objective in a cell, David Hinds hand made, that became a solar telescope. The 4 objectives were bought very reasonably priced from an eyepiece supplier. He had them in a drawer and I asked if I could buy them, he said yes.
(David Hinds made 6,000 mirrors all good standard, but the objectives were just one off I think.)
David Hinds, himself, hand made doublets. 1,000mm f.l. 4mm ortho Japanese eyepiece.
All my custom scopes have metal handles, with holes for aligning.
However, terrestrially it is much easier to find something than astro. One just pans the horizon,
The 4.7 miles is over suburban mostly houses but parks etc. looking north.
Seeing black marks on a lit 5ft? clock face on a tower is like sunspots, much easier than other resolution targets.
The tripod is a simple mahogany garden tripod from my 3 inch Starboy Broadhurst Clarkson scope made for me in 1956/1957 total cost £28.10s. The head is brass as simple as they come. The bolt is tightened to adjust friction.
The 2 telescope mounting holes are 10 inch apart.
My 123 mm Jaegers objective custom scope in blue enamel also fits same garden tripod.
Maybe 8 kgs the lot.
Bathroom window open. Left 1 or 2 hours to stabilise temperature unheated.
3 a.m viewing many occasions. Repeatedly saw these tiny tick marks.
I normally used 150x but switching to 250x I straight away noticed these very small tick marks that marked the minutes. I had not even suspected them before. Don't be afraid of high magnification.
I believe in utter simplicity rather than crazy Goto scopes.
I could find multiple deep sky objects a lot faster than anybody with a Goto scope.
I have 3 identical 120mm aperture custom made aluminium tube simple scopes. Grey enamel? It was cheaper to get three at the same time. No finders. I don't need them as I use a low power eyepiece if necessary to find stuff.
I had 2 objectives coated at my own risk. I left one uncoated in case the coating heat cracked the glass.
I also had a 110mm f/16 Fraunhofer objective in a cell, David Hinds hand made, that became a solar telescope. The 4 objectives were bought very reasonably priced from an eyepiece supplier. He had them in a drawer and I asked if I could buy them, he said yes.
(David Hinds made 6,000 mirrors all good standard, but the objectives were just one off I think.)
David Hinds, himself, hand made doublets. 1,000mm f.l. 4mm ortho Japanese eyepiece.
All my custom scopes have metal handles, with holes for aligning.
However, terrestrially it is much easier to find something than astro. One just pans the horizon,
The 4.7 miles is over suburban mostly houses but parks etc. looking north.
Seeing black marks on a lit 5ft? clock face on a tower is like sunspots, much easier than other resolution targets.
The tripod is a simple mahogany garden tripod from my 3 inch Starboy Broadhurst Clarkson scope made for me in 1956/1957 total cost £28.10s. The head is brass as simple as they come. The bolt is tightened to adjust friction.
The 2 telescope mounting holes are 10 inch apart.
My 123 mm Jaegers objective custom scope in blue enamel also fits same garden tripod.
Maybe 8 kgs the lot.
Bathroom window open. Left 1 or 2 hours to stabilise temperature unheated.
3 a.m viewing many occasions. Repeatedly saw these tiny tick marks.
I normally used 150x but switching to 250x I straight away noticed these very small tick marks that marked the minutes. I had not even suspected them before. Don't be afraid of high magnification.
I believe in utter simplicity rather than crazy Goto scopes.
I could find multiple deep sky objects a lot faster than anybody with a Goto scope.
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That would indeed be a correct assumption.
It's likely to be a permanent fixture, though it might occasionally need to be moved a few feet (for cleaning purposes etc)
This is just for casual fun viewing, for me and various house guests.
Excellent idea, I'll give that a try.
Thanks Alan!
Dear Alan,
The observing conditions were not exceptional, as I could repeat the observation with any of the 3 scopes on good nights.
However, we have a temperate climate and quite often static temperature.
My observing height was 30ft above the ground and the clock tower clock maybe 80ft, possibly higher.
With 20/15 eyes I could see sunspots with a penumbral diameter of 38 arcseconds, or 34 arcseconds with my head braced against a lamp post. This using a tilted large welders glass 13 at the optimum density.
However, those with very fine eyesight can see sunspots 20 arcseconds penumbral diameter.
Sunspots are not really black at the edges.
I followed a Mercury transit with an exactly 3x opera glass with a Mercury diameter of 12 arcseconds.
Both sunspots and transits are easier way from the Sun's limb.
The 120mm scopes have a magnification range of 20x to 330x.
The 123 mm Jaeger scope 16x (4.7 degree field) to 145x Swift Ortho (or 210x Clave 3mm but slight objective misalignment noticed here).
Horace Dall had good clear photos of a church gutter end on perhaps 5 inch across at 17 miles taken with his 108mm f/30 Camera Obscura objective corrected for 4 colours. He was on a high hill with a very high roof on his house.
The problem with birdwatching scopes is that the the observations are maybe 5ft or 6ft above the ground and the birds also low, so one is looking through the boundary layer between the ground and air above it.
Often the air is turbulent.
The observing conditions were not exceptional, as I could repeat the observation with any of the 3 scopes on good nights.
However, we have a temperate climate and quite often static temperature.
My observing height was 30ft above the ground and the clock tower clock maybe 80ft, possibly higher.
With 20/15 eyes I could see sunspots with a penumbral diameter of 38 arcseconds, or 34 arcseconds with my head braced against a lamp post. This using a tilted large welders glass 13 at the optimum density.
However, those with very fine eyesight can see sunspots 20 arcseconds penumbral diameter.
Sunspots are not really black at the edges.
I followed a Mercury transit with an exactly 3x opera glass with a Mercury diameter of 12 arcseconds.
Both sunspots and transits are easier way from the Sun's limb.
The 120mm scopes have a magnification range of 20x to 330x.
The 123 mm Jaeger scope 16x (4.7 degree field) to 145x Swift Ortho (or 210x Clave 3mm but slight objective misalignment noticed here).
Horace Dall had good clear photos of a church gutter end on perhaps 5 inch across at 17 miles taken with his 108mm f/30 Camera Obscura objective corrected for 4 colours. He was on a high hill with a very high roof on his house.
The problem with birdwatching scopes is that the the observations are maybe 5ft or 6ft above the ground and the birds also low, so one is looking through the boundary layer between the ground and air above it.
Often the air is turbulent.
Binastro: A 5 inch refractor with tripod and head steady enough to use without excessive vibration at 250x and weighing only 17 lb is impressive indeed! My 3" F7.4 apochromat with head and sturdy tripod is closer to 20lb.
Joachim: Long focal length eyepieces have apparent field of view limited by the barrel diameter not by any limitation of the eyepiece design. For instance, Plossl eyepieces typically have modest apparent field of view by today's standard, but the longest Plossl in 1.25" barrel with the full 50 degree apparent field is I believe around 32mm. If you go to a 2" barrel, then a lower power 50mm focal length with full 50 degree field is available. Further, my comments about panorama, looking through a soda straw, and pointing the telescope were related to actual field of view, i.e., apparent field divided by magnification. At 180x, even an Ethos design will only show you only approximately half a degree. Zoom eyepieces are another kettle of fish and are not known for wide field of view, but as you say apparent field improves as you zoom higher. Yet actual field of view decreases significantly as you zoom (Nagler 2-to-1 zooms with constant 50 degree field are the exception here). BTW, most of my binoculars have apparent field of view similar to Panoptic eyepieces--65ish degrees.
Binastro and Joachim: I agree that higher magnification is nothing to fear, and I am happy that your telescopes and viewing situations allow you to enjoy such high magnifications for terrestrial viewing.
Yet, I believe that an inexperienced owner and/or a casual viewer will find it difficult to use a telescope near it's theoretical limit of magnification looking through an exit pupil of ~0.5mm. This opinion is based on observing new telescope owners and casual viewers at public star parties. That is why I recommended that the OP take the opportunity to actually see some telescopes in person and look through them before deciding on a purchase. Since OP's interest was terrestrial and perhaps daytime views, I suggested the science centers, though public star parties might also prove interesting.
Alan
Joachim: Long focal length eyepieces have apparent field of view limited by the barrel diameter not by any limitation of the eyepiece design. For instance, Plossl eyepieces typically have modest apparent field of view by today's standard, but the longest Plossl in 1.25" barrel with the full 50 degree apparent field is I believe around 32mm. If you go to a 2" barrel, then a lower power 50mm focal length with full 50 degree field is available. Further, my comments about panorama, looking through a soda straw, and pointing the telescope were related to actual field of view, i.e., apparent field divided by magnification. At 180x, even an Ethos design will only show you only approximately half a degree. Zoom eyepieces are another kettle of fish and are not known for wide field of view, but as you say apparent field improves as you zoom higher. Yet actual field of view decreases significantly as you zoom (Nagler 2-to-1 zooms with constant 50 degree field are the exception here). BTW, most of my binoculars have apparent field of view similar to Panoptic eyepieces--65ish degrees.
Binastro and Joachim: I agree that higher magnification is nothing to fear, and I am happy that your telescopes and viewing situations allow you to enjoy such high magnifications for terrestrial viewing.
Yet, I believe that an inexperienced owner and/or a casual viewer will find it difficult to use a telescope near it's theoretical limit of magnification looking through an exit pupil of ~0.5mm. This opinion is based on observing new telescope owners and casual viewers at public star parties. That is why I recommended that the OP take the opportunity to actually see some telescopes in person and look through them before deciding on a purchase. Since OP's interest was terrestrial and perhaps daytime views, I suggested the science centers, though public star parties might also prove interesting.
Alan
You are correct Alan.
On bad days in daylight even 30x is sometimes a turbulent mess.
I should point out that the clock face was upside down with nothing but objective and ortho eyepiece.
I have Kelners of 50mm, maybe also 60mm in 2 inch barrel. The 2 inch 32mm Erfle is lovely, as is the 25mm Erfle in 1.25 inch fit. I have Naglers also but orthos are just as good centrally.
The Kodak eyepiece is about 2.5 inch or wider.
Mahogany wooden, simple 3 one piece leg tripods do absorb vibrations.
After many years I took the tripod back to Broadhurst Clarkson as it was wobbly and the master craftsman made 3 brass spacers to go into the enlarged wooden holes.
He charged me nothing after maybe 30 years use.
I found that the 3 inch Starboy objective elements had rotated a lot. I used the original best position pencil marks to reset the elements after cleaning.
In the bathroom I had to be careful my body heat did not destabilise the air. I wore enough to stop body heat escaping.
P.S.
How about a 2.5Kg Slik 88 tripod and Vivitar 600mm f/8 solid Cat, Japanese monocular converter 10mm eyepiece and 3x Barlow giving 180x and easily resolving both sets of pairs of epsilon Lyrae with clear sky between. About 2.5 arseconds each pair. total weight around 4 kg.
Mirador 70mm Maksutov easily used at 120x on many days in daylight through double glazing at birds on chimney pots at 124m. Crows, magpies and herring gulls.
90mm Skywatcher Maksutov at 125x best power or 190x same tripod through double glazing. No problem, although 190x is empty magnification but crows are huge. The eyes are amazing, but needs bright sunlight.
On bad days in daylight even 30x is sometimes a turbulent mess.
I should point out that the clock face was upside down with nothing but objective and ortho eyepiece.
I have Kelners of 50mm, maybe also 60mm in 2 inch barrel. The 2 inch 32mm Erfle is lovely, as is the 25mm Erfle in 1.25 inch fit. I have Naglers also but orthos are just as good centrally.
The Kodak eyepiece is about 2.5 inch or wider.
Mahogany wooden, simple 3 one piece leg tripods do absorb vibrations.
After many years I took the tripod back to Broadhurst Clarkson as it was wobbly and the master craftsman made 3 brass spacers to go into the enlarged wooden holes.
He charged me nothing after maybe 30 years use.
I found that the 3 inch Starboy objective elements had rotated a lot. I used the original best position pencil marks to reset the elements after cleaning.
In the bathroom I had to be careful my body heat did not destabilise the air. I wore enough to stop body heat escaping.
P.S.
How about a 2.5Kg Slik 88 tripod and Vivitar 600mm f/8 solid Cat, Japanese monocular converter 10mm eyepiece and 3x Barlow giving 180x and easily resolving both sets of pairs of epsilon Lyrae with clear sky between. About 2.5 arseconds each pair. total weight around 4 kg.
Mirador 70mm Maksutov easily used at 120x on many days in daylight through double glazing at birds on chimney pots at 124m. Crows, magpies and herring gulls.
90mm Skywatcher Maksutov at 125x best power or 190x same tripod through double glazing. No problem, although 190x is empty magnification but crows are huge. The eyes are amazing, but needs bright sunlight.
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If one wants real low weight telescopes one could look up Horace Dall's pocket scopes.
He made dozens from 2.5 inch to 6 inch aperture.
They folded to fit in his pocket including folding tripod legs.
They were high quality thin optics with raytubes, Dall Kirkham design. I think that all his scopes gave upright images. He was a master of relay lenses. Mostly aspherised optics with some cemented triplet components.
He took them on his pioneering bicycle trips around Iceland and Lapland. He used dry riverbeds to cycle.
Also Patagonia where he met his second wife Helena.
Some are now in the Science museum, London.
He made dozens from 2.5 inch to 6 inch aperture.
They folded to fit in his pocket including folding tripod legs.
They were high quality thin optics with raytubes, Dall Kirkham design. I think that all his scopes gave upright images. He was a master of relay lenses. Mostly aspherised optics with some cemented triplet components.
He took them on his pioneering bicycle trips around Iceland and Lapland. He used dry riverbeds to cycle.
Also Patagonia where he met his second wife Helena.
Some are now in the Science museum, London.
Fascinating!
Seems like a wonderfully convenient design, all mirrors, so no chromatic aberration. Surprising that no one offers anything like it commercially today. Particularly considering the push for small and light.
Are they perhaps difficult to use?
Hi,
modern Dall Kirkham telescopes used for imaging often have a sub diameter corrector for better performance in the field.
Horace Dall was primarily a planetary imager so field performance was maybe not a primary concern...
They are available commercially mainly in quite large sizes for professional use. The most common and affordable versions (which are still rare birds) come in the form the Takahashi Mewlon series.
Here's some links:
http://martinmobberley.co.uk/dall.html
http://www.telescope-optics.net/dall_kirkham_telescope.htm
http://www.gettyimages.de/detail/na...ng-telescope-was-built-and-picture-id90770286
http://www.takahashi-europe.com/en/mewlon.php
http://planewave.com/technology/
https://www.toscanoptics.com/cassegrain-dall-kirkham
Joachim
modern Dall Kirkham telescopes used for imaging often have a sub diameter corrector for better performance in the field.
Horace Dall was primarily a planetary imager so field performance was maybe not a primary concern...
They are available commercially mainly in quite large sizes for professional use. The most common and affordable versions (which are still rare birds) come in the form the Takahashi Mewlon series.
Here's some links:
http://martinmobberley.co.uk/dall.html
http://www.telescope-optics.net/dall_kirkham_telescope.htm
http://www.gettyimages.de/detail/na...ng-telescope-was-built-and-picture-id90770286
http://www.takahashi-europe.com/en/mewlon.php
http://planewave.com/technology/
https://www.toscanoptics.com/cassegrain-dall-kirkham
Joachim
