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Opticron Mighty Midget 3 MM3 60, yes I mean MM3 60 not 50 (1 Viewer)

Thanks for the review David, it was challenging on the day. The HDF zoom eyepiece which is shipped with most of the MM3 models to date has some magnificatio indicators still on it from when we used to sell previous models, eg GS 665 ED etc. The next shipment of HDF zoom will show show the magnification indicators for the the MM3 models
 
No info yet on Opticron website about MM3 60ED

Hello, all,

It is mid Thursday, nearly a week after the opening of Birdfair and the Opticron website has not been updated to tell us all about the new MM3 60ED, no information, no specifications.

As a tried and tested conspiracy theorist, and if I did not own one, I might think it was all smoke and mirrors and, perhaps, a few grains of ED dust!

Maybe Opticron is preoccupied bringing its MM3 70ED onto the market. Considering it can rustle up a new scope so quickly out of the ether, when do you think it will be here - in time for Christmas? Perhaps it is on the high seas already.

'PG Tip of the week'. ————-We have no plans for an MM3 80ED

Wanderer aka Cassandra
 
Focal Length

Thanks Chris.

Can anyone tell me please, what the scope's focal length is? And how to calculate it?
 
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Can anyone tell me please, what the scope's focal length is? And how to calculate it?

From Pete Gamby's reply #241 in this thread: http://www.birdforum.net/showthread.php?p=2970812#post2970812 we are told that the focal length of the 40862 zoom eyepiece is 8mm to 24mm.

At reply #243 we have that the focal length of the scope is calculated as (magnification)(eyepiece focal length). The magnification achieved with the zoom at 8mm is stated to be 45X http://www.opticron.co.uk/Pages/mm3_scope.html.

So the MM3 60mm focal length is (8)(45) = 360mm.
 
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for Chris Galvin,

You will see that Allan found for me a way to calculate a scope’s focal length but, if I am correct that it is a fundamental property of a scope, could this not be included with with the specifications on the website?



The-Wanderer
 
I don't write the product specs for the website or the paper Product Guides, but I will relay your concerns. However that info is really only required by a handful of Birdforum subscribers and they can all work it out
 
Wanderer,

Until Pete, Chris or Rob chime in with the actual number I would suggest the focal length of the scope to be "around" 360 mm. That is a general average for scopes in the 60-65 mm objective class. The 50 mm MM3 was 286 if I remember correctly so 360 can't be too far off.

I am curious why you are asking though. Unless it has to do with either putting an after market eyepiece on the scope or something for photography?

After doing a little math....working backwards with the 50 mm MM3 and the HDF zoom .... 286/12=23.8x15=358.... so my 360 guess probably isn't too far off.

Edit: sorry, didn't see the previous posts. Browser took me to the previous page when I clicked on new posts for this thread.
 
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Allan,

Thank you for answering FranckD’s query for me. The time difference doesn’t help - at least you are both on the same continent!

The Jayandawanda is site is down so I used google to search for others. There were some but the links did not work for me.

This one, however, http://jerryjourdan2.blogspot.co.uk/2007/05/digiscoping-start-to-print.html does provide a method of calculation. But it does not use the scope’s focal length. It seems much simpler than Jay and Wanda and I have prepared the results I need on a spreadsheet.

How accurate it is, I do not know.

The-Wanderer
 

Nice to see that Jay and Wanda's calculator is working again.

I entered the parameters for the MM3 60mm, and my Sony RX100 III at max zoom (70mm equiv). The combination is equivalent to a 1050mm f6.4 lens.

As a comparison, the same camera on the MM3 50mm is equivalent to a 840mm f6.2 lens. So for digiscoping there may not be much incentive to upgrade to the new MM3 60mm.
 
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Hello, Allan,


I am calculating for my Canon S110 on my MM3 60ED.which has the SDLV2 eyepiece fitted. I am using the listed Nikon PS100 as a surrogate for the Canon as it has the same sensor size, similar zoom and mega pixels. I think that will be good enough for me.

I use aperture priority set at f5.9 because wider apertures tend to close down to that anyway, or it did on the MM50 ED.

The camera zoom range is 24mm - 120mm on 35 mm equivalent format. I have to set the rig to maximum zoom to save the camera lens from hitting the buffers (the eyepiece lens).

The camera has a stepped zoom ring and I can set it from 120 mm down to 100mm and 85mm without significant vignetting, but no further.

With the Scope eyepiece at 15x magnification and the zoom at 85mm the calculated focal length is 1,274mm and for 45x and at 120mm the calculated focal length is 5,400mm, so that is the range.

IMHO digiscoping is not a good choice, for me anyway, up to about 1,200mm focal length. I am using two bridge cameras, the Panasonic Lumix FZ150 with a maximum zoom length of 600mm; with two teleconverters it can reach 1,020 mm and 1,320 mm respectively. Image quality is very odd on both, but not towards the periphery in the latter case which I find not to be problem for birding. This camera has good performance shooting in RAW. Unfortunately the RAW performance in the Canon SX50HS is nowhere near as good, but it does have a maximum zoom of 1,200mm.

If I get a windfall, I may try to buy a used Opticron 32x eyepiece (40858) but opinions on fixed lenses over the SDLv2 do not give me confidence that the money would be well spent.

Thanks for your help
 
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and for 45x and at 120mm the calculated focal length is 5,400mm, so that is the range.

You can look at the exit pupil of the eyepiece, and notice how small it gets when you zoom to 45X. This is why digiscoping is almost never successful at such extremes. The digiscoping calculator at Jay and Wanda will calculate the effective f-stop. If that is f11 or wider you can get a good image. If it is f32 (yikes!) you will be in diffraction-limited territory, even if you can manage to avoid apparatus-shake.
 
The digiscoping calculator at Jay and Wanda will calculate the effective f-stop. If that is f11 or wider you can get a good image.

Allan,

Since your post I have been trying to get to grips with the dark arts of digiscopy.

The dealer I bought my first scope from advised that digiscopy should not be tried at more than 20x magnification. I suspected that this was either urban, or perhaps I should say, rural myth.

It seemed to me that loss of definition had to be laid at the door of diffraction, but it was not until your post that I thought the mist might be lifting.

Earlier on bird forum.net, I had read that “The usual design target is a 2mm to 2.5mm exit pupil which optimizes aberration and diffraction effects in the eye so 20x to 25x with a 50mm scope. And hence the usual fixed 25x or 30x eyepiece on 60mm scopes and 30x or 40x on 80mm scopes.” There was no science given to back this up but I suspected that diffraction would be significant even at 2.5mm pupil exit diameter.

You suggested diffraction limiting would be at about f11.

Using http://www.jayandwanda.com The two criteria are close for most settings I tried, but not the same. I suspect that the Optical Resolution figures would give me a better understanding of when diffraction effects limit the final image, but my science and maths are not up to this.
 
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