Travelscope for eclipse...

[Wavytone]

All, I'm off to the US for the eclipse and looking for a refractor that can do duty as a telephoto lens (aiming to record the eclipse in 4K video with an m4/3 body) and ideally be a nice visual scope later. Looking for a focal length in the range 480mm - 600mm.

So... does anyone here know anything about the following scopes which are my shortlist:

1. Stellarvue SV70T - its an ED APO triplet, 70mm f/6 420mm fl which is a tad on the short side.

2. APM Imaging Star 70mm f/6.78 475mm fl, ED triplet APO + a corrector internally;

3. APM TS Photoline 80mm f/6.25 500mm, ED APO triplet again;

4. APM TS Photoline 90mm f/6.6 600mm, ED APO triplet again.

The APM optics are evidently from SharpStar in China.

[barx1963]

Wavy
Andy Campbell (andy01) has a SV70T. Having seen the results with that it inspired me to have a go a buying an SV scope myself. Maybe touch base with him for some thoughts on the scope maybe.

Malcolm

[Wavytone]

Ok wil do.

One aspect of the APM scopes that is interesting is their OTA have several segments - ostensibly to accommodate several configurations - visual or AP with assorted bodies needing different back focal lengths - and it also means a larger OTA can be split to fit as cabin luggage, hence the 90mm scope.

The APM scopes can accept a 0.75 X reducer/corrector, screws on via an M63 thread.

Heck I might even get into AP afterwards... Heaven forbid.

[DJT]

Hi

Thought about an FS60Q? I have the FS60C at F5.9, 354 MM, but with the Q module which is effectively a Barlow at 1.6x, that puts it into your ball park though at F10. With the Q attached, you get a very flat image. it's really very good.

Again, breaks into 2 parts so great for hand luggage.

Just a thought

[wavelandscott]

Where are you planning to view the eclipse?

While not related to your question, I see that Lunt has some Sunoculars available and was considering grabbing a pair...

[Wavytone]

We have accommodation in Corvallis, OR, just south of the centre line. If it's looking bad in the wee hours, there's also a road east over the Rockies to Madras...

Sunoculars... Hmmmm....

[wavelandscott]

Safe travels...I am hoping to be in Southern Illinois

[OzEclipse]

Wavy,

Why do you say 420mm is too short? I've attached one of my pics taken on APS C with a WO 70mm f6.3 APO, super imposed with an outline of an M4/3 field.

Corona is growing as we head for solar minimum so next years corona should be a bit bigger than this one from 2015.

A 420mm refractor fits into a mid size camera backpack for carry-on.

Longer focal lengths will start to crop the corona.

cheers

Joe

[Wavytone]

Thanks joe, more food for thought. I'd drawn a sclediagram of what I want to do - which was a 4K video of the diamond ring and chromosphere - not so much the corona,though I know the inner corona will show at 30fps frame rate and f/6. The camera will be completely automated and hands free.

To be honest though I'm wondering if it's worth the trouble knowing that literally many thousands will do a better job. Maybe better to simply watch, and see a pic or two online.

[Peter Ward]

At port Douglas I was using a Canon 500mm F4 with a 1.4x teleconverter, which in retrospect was not ideal.

I previously used William Optics 80mm refractor and barlow with great success (won the Malin award that year)

I've since been exploring new options as well, and will be running with my Baby FSQ85 and probably a 5DMKIV or maybe 60Da. The system is razor sharp, with a flat field and fits neatly into a carry-on camera bag.

I've tested various systems in the past by pointing the camera/scope at a Mercury-lamps/street light. Any reflections become very obvious and will also show during the diamond ring phase of the eclipse...and then some...so you might want to explore that prior to packing any gear.

[Wavytone]

Hi Peter,

I'm well aware of how severe an optical test an eclipse will be, I've seen several in the 1970's and 80's. As for the internal reflections... yes well aware of this - seen it many times in images of the diamond ring taken through camera lenses, even Questers used to shoot movies of it are perfect either.

Long ago my own photos were long ago using 35mm film; the scopes then being 8"f/7 newtonian with an off-axis filter, huge setup but very effective; a C8 which I took to Tasmania twice for annular eclipses (OK but not great) and later a 4" f/10 SCT + glass filter which was great for 35mm, but way too big for m4/3 (anyway that scope is long gone).

Of the m4/3 lenses the upper limit is the Panasonic 100-400 zoom and that's both expensive as I'll probably never use it again, and optically no match for the triplet ED APO's around, though reflections are basically an unknown with these.

After a lot of hunting around and reviews and info I'm leaning towards this beastie http://www.apm-telescopes.de/en/telescopes/refracting-telescopes-ota/apochromates/ts-imaging-star-70-mm-f-678-ed-quadruplet-flatfield-apo-refractor.html

Another idea I'm kicking round is to use a singlet lens optimised for a single colour with an optical glass filter, and shoot monochromatic in a narrow bandpass. Might not be so photogenic, but should be sharp and free from reflections.

... Will also buy a 90mm ED APO for domestic use.

[N1]

Not a bad idea when you consider that the image that even remotely approaches The Real Thing has yet to be taken. I've decided for myself that nothing is worth sacrificing even one second of viewing time during Totality (except emergencies obviously). That does not mean one shouldn't image, but simplicity is key.