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"fast" refractors for astrobirding (1 Viewer)

John250

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Hi folks,
Is a “fast” (f/5-6) refractor unsuitable for bird photography because of its shallow depths of focus and field? Does focus peaking or other camera focusing aids mitigate focusing problems with fast scopes?
Thanks, John
 
Hi folks,
Is a “fast” (f/5-6) refractor unsuitable for bird photography because of its shallow depths of focus and field? Does focus peaking or other camera focusing aids mitigate focusing problems with fast scopes?
Thanks, John
Hi John,

What focal length did you have in mind?

I have two scopes, a short 80mm F/6 and a long 102mm F/6.8. Many people here use 80mm F/7.5 and are pleased with that. I could potentially think of a 80mm F/5 for some close range situations but I would not sacrifice the reach that the big scope gives me in favor of speed. If you have to choose one useful focal length it would probably be around 600mm. But with F/5 the portability/weight (and cost) of such a scope could be an issue, so better stay at around F/6.

Focus peaking is one way to ease focusing accuracy. EVF magnification is an other way. I am a friend of the EVF magnification, but both methods work fine. If you have a high quality EVF and have no sight impairment then with some practice you should be able to get shots with correct focus in >50% of the cases, shoot a handful of pictures and at least one will be spot on.

Welcome to the forum by the way.
 
Hi Tord,
Thanks for your comments. I currently use a spotting scope for afocal bird photography (f/21, ~1800mm). I have a 4 inch refractor for visual astronomy, but at 14+ lbs and over 36 inches it is larger than I can handle for birding. I am interested in a lighter, compact scope with 75 to 85 mm aperture. Based on your comments I will probably try to find something in the f/7-8 range.
Thanks, John
 
Look into the many versions of the Synta scopes, like the Skywatcher 80/600mm doublet. Marketed under many different names. Light, cheap, and sharp, extremely so if you get a really good one. They are usually in the range of 0.92-94 Strehl. Lots of bang for the buck. Just make sure it has Ohara FPL-53 glass in it. If you want to spend more, get a 90/600mm triplet in a carbon tube. Same weight but better optics.
Mine is 0.97-98 Strehl. 1.0 is theoretically perfect.
 
Look into the many versions of the Synta scopes, like the Skywatcher 80/600mm doublet. Marketed under many different names. Light, cheap, and sharp, extremely so if you get a really good one. They are usually in the range of 0.92-94 Strehl. Lots of bang for the buck. Just make sure it has Ohara FPL-53 glass in it. If you want to spend more, get a 90/600mm triplet in a carbon tube. Same weight but better optics.
Mine is 0.97-98 Strehl. 1.0 is theoretically perfect.

Dan is right. I started with a no name scope purchased on eBay and I never got a sharp photo out of it. I then purchased a SkyWatcher Black Diamond 80 ED and got great results. Those scopes are sharp ! You can get it with accessories included like the eyepiece and the spotting scope or get a stripped model. I suggest you get the Black Diamond since it has the dual speed focuser - it is very smooth, easy to adjust and the knobs can be reversed so the dual knobs are on the left side where they should be for good ergonomy with a camera attached.

http://ca.skywatcher.com/_english/01_products/02_detail.php?sid=350

Shop carefully since the same scope is offered under many names and models under a very wide price range. The Black Diamond is a great value for the price. Of course, there are better ones but they are more expensive - Dan and Tord can offer good suggestions.

You will be happy with one as long as you are ok with a big and heavy slow (f/7.5) manual focus lens. Make sure you have a sturdy stable tripod and a gimbal is strongly suggested.

These days, there is lots of interest for lighter camera gear. A few of us are playing with a Canon 400mm attached to an Olympus EM-1. This is nice but it cannot beat a good astro scope, specially for long range bird photography.

Welcome to the club
 
Hi Tord,
Thanks for your comments. I currently use a spotting scope for afocal bird photography (f/21, ~1800mm). I have a 4 inch refractor for visual astronomy, but at 14+ lbs and over 36 inches it is larger than I can handle for birding. I am interested in a lighter, compact scope with 75 to 85 mm aperture. Based on your comments I will probably try to find something in the f/7-8 range.
Thanks, John
Hi John,

I started with the same scope as Jules (but branded with the name Skywatcher, and with a single speed focuser). Bang for bucks can hardly be beaten. I got really good results but wanted even better so I bought a 102mm APO triplet refractor. Mine is F/6.8 (700mm focal length) and weights around 6.5-7 kg. The one that is on my avatar. 700 mm is a tad long and 7 kg a tad heavy but when mounted on carbon fibre tripod and gimbal head the operation is easy. Transporting the setup deployed over the shoulder is acceptable, as long as the terrain is easy. Later on I bought a short scope, 80mm F/6 triplet APO that I am using for closer range action and also for travel as it fits in the hand luggage. That one weighs around 2kg and can be operated hand-held (some dexterity is required), although I usually have tripod or bean bag support.

From what you write it seems yours is ~F/9 / 900mm.

What camera are you planning to use?
 
Thanks everyone for the comments and suggestions. Tord, I just last week started using an Olympus Air/iPhone 6 with my spotting scope. I will probably try this with whatever scope I purchase.
John
 
You would be better off with something like an E-M5 directly on the scope. The can be found quite cheaply now and it is far better than "digiscoping".
 
Thanks everyone for the comments and suggestions. Tord, I just last week started using an Olympus Air/iPhone 6 with my spotting scope. I will probably try this with whatever scope I purchase.
John
John,
Then you would be using an afocal system, which is something completely different from what we are discussing in this section of the forum - prime focusing, i.e. coupling the camera body directly to the scope, no lens, no eyepiece in between. Afocal systems are capable of high magnifications, but I am afraid you will be disappointed by the image quality delivered by an (expensive) F/6 refractor, eyepiece and camera lens (e.g. Air) compared to what the scope alone coupled directly to the camera sensor will deliver.

/Tord
 
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John,
Then you would be using an afocal system, which is something completely different from what we are discussing in this section of the forum - prime focusing, i.e. coupling the camera body directly to the scope, no lens, no eyepiece in between. Afocal systems are capable of high magnifications, but I am afraid you will be disappointed by the image quality delivered by an (expensive) F/6 refractor, eyepiece and camera lens (e.g. Air) compared to what the scope alone coupled directly to the camera sensor will deliver.

/Tord

To make it simple:
Prime focus: the telescope becomes a manual lens
Afocal: you are using a camera and lens to take a photo of the image that comes out of the spotting scope and eyepiece.
 
The Olympus Air is effectively an Olympus EM-5 without the EFV, screen and mechanical controls. The iPhone is used to view the image and control the camera remotely. It will be used at prime focus on the telescope.

http://www.imaging-resource.com/PRODS/olympus-air-a01/olympus-air-a01A.HTM

John,

The Olympus Air is an interesting device but, IMHO, I don't think it is the best camera choice to use with a scope unless you already own one. Astro scopes are manual focus devices and you need to see a very clear image in order to be able to focus accurately. This won't be the case with the iPhone on clear days where there is lots of light to wash out the image on any LCD screen, even the best ones. However, in situations when light on the LCD is not a problem, the large screen and its high resolution must be very nice indeed.

2 hands are needed with a scope: one to focus and one to actuate the shutter. Even if the contact is light, putting your eye on the viewfinder gives you a third connection point with your device, making your setup much more stable and easier to control. It also makes it easier and more natural to find and then follow a bird in movement. Some people may not agree with this but this is how it is for me.

When I made the switch from Canon to Oly because of weight and size, I discovered the EVF and IMO it is one of the most important benefits of mirrorless cameras. A good quality WYSIWYG EVF is a natural with an astro scope.

Of course, you can use the AIR to communicate remotely with the iPhone over WiFi but I don't think it will be very useful for most bird photography situations. Many cameras offer WiFi and you can do the same thing when you want to reduce shutter movement or actuate shutter remotely.
 
The Olympus Air is effectively an Olympus EM-5 without the EFV, screen and mechanical controls. The iPhone is used to view the image and control the camera remotely. It will be used at prime focus on the telescope.

http://www.imaging-resource.com/PRODS/olympus-air-a01/olympus-air-a01A.HTM
John,

You cannot use the Olympus Air for prime focusing.

What you need is a camera body, e.g. E-M5, and attach it to the scope with an adapter (2" - micro 4/3). In between the scope and the adapter you will need a 2" extension tube in order to support focus at close distance. 80mm length is what most people here use, it should allow close focus distance of some 4-6 meters while still being able to focus at infinity. How close is depending on the design of the scope and the camera used.
 
John,

You cannot use the Olympus Air for prime focusing.

What you need is a camera body, e.g. E-M5, and attach it to the scope with an adapter (2" - micro 4/3). In between the scope and the adapter you will need a 2" extension tube in order to support focus at close distance. 80mm length is what most people here use, it should allow close focus distance of some 4-6 meters while still being able to focus at infinity. How close is depending on the design of the scope and the camera used.

Humm... not sure. I think it is as simple as attaching the Oly Air where we attach the EM-1 on our scope assemblies (scope, extension and adapter) and it should work. The Air is made to use M43 lenses just like the EM-1.

Now, it is a good choice ? I don't think so.
 
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