Some digiscoping experiments with a dslr (1 Viewer)

[Derry]

think we are going to have to draw the line in the sand somewhere and go with what we have,, just reading an article on how much AA filtering Olympus does compared to other brands which has negative impact on resolution,, you just mentioned the Oly E420 which seems to have even more AA as it is rendering some soft photos from the same lens, owners had sharper photos with on prior bodies,,

the more we read the more data to place into the coffer and digest,,

our end result is trying to resolve some fine lines at given distance,, either the equipment can or it cannot,, when we get to the longer distance air turblance is going to have great impact,, how do we control or calculate that into obtaining a sharp image,,

we have the base that Jules prepared with test chart(s),, lets shoot them at prime filling the screen and then start working at given distances to see what we can resolve on the lines at given X mags,,

if we want to use the cameras factor into the calculation I am fine with it,,

Derry

 

[Paul Corfield]

Here's a photo from this morning taken with the new 2" GSO 2X ED Barlow. I was photographing the test chart when this Wood Pigeon landed on the fence just above the chart so I knew the range was 15m give or take a few cm. This is a crop from the original and the crop was resized from 1568 px wide to 1024 px. The barlow gives excellent resolution and is a great alternative to the much more expensive teleconverters such as Kenko Pro, Sigma Apo or camera own brands. Only thing I had to do with the barlow was make some baffles to get rid of some internal reflections and this was a very quick and easy job to do.

I'll post some photos later of how I have the barlow set up on the camera/scope.

Paul.

 

[Paul Corfield]

Here's some more photos from this morning plus a crop showing feathers at 100%. Really loving the resolution this barlow is producing.

Paul.

 

[Neil]

Here's some more photos from this morning plus a crop showing feathers at 100%. Really loving the resolution this barlow is producing.

Paul.

Excellent detail Paul. You can see every feather.
Neil.

 

[JGobeil]

Paul - I'm impressed ! How do you make the baffles ?

 

[Paul Corfield]

Paul - I'm impressed ! How do you make the baffles ?

Here's 3 photos of the whole setup, middle one shows the baffles. I just used a large rubber eyecup from an old eyepiece and pressed it down into the 2" scope adapter. You wouldn't believe the difference that just using this makes. I'll have to show a photo taken with and without. Without the baffles the whole photo lacks contrast and covering most of the centre there is an obvious bright spot caused by stray light. As an extra I could probably do with making something for the front of the lens cell as there's some quite shiny black metal exposed. Also, the barlow housing forms a good extension tube but I could do with one more fairly short 2" extension just get me down to 4 or 5 metres. 2" extension tubes are readily available so that wont be a problem.

Paul.

 

[Paul Corfield]

Here's a before and after showing the difference made by inserting the baffles. It's not just the GSO barlow that suffers from stray light, all my collection of 5 other barlows do the same thing to varying degrees.

Paul.

 

[JGobeil]

Interesting... In fact, it seems that the reflections don't come from the barlow but from the T adaptor. You didn't put the baffles inside the barlow get rid of the reflections but inside the T adaptor. My CNC EOS adapter is fully baffled, I wonder if I would have the problem.

This barlow sure looks a nice inexpensive multiplier. I should be able to test my scope this morning with the TCs. I may very well decide to get one of those.

Regards
Jules

 

[Paul Corfield]

Yeah, it must be something to do with the light path and too many shiny surfaces. They may be black but it's a shiny black which I can never understand. The chrome barrel on the barlow housing is all matte black so I'll get an aerosol can of matte black paint and give all the internal surfaces of the t-mount a coat of that. Strange that it never happens with teleconverters and only with barlows.

Paul.

 

[JGobeil]

Yeah, it must be something to do with the light path and too many shiny surfaces. They may be black but it's a shiny black which I can never understand. The chrome barrel on the barlow housing is all matte black so I'll get an aerosol can of matte black paint and give all the internal surfaces of the t-mount a coat of that. Strange that it never happens with teleconverters and only with barlows.

Paul.

The light path must be different. On my 2X TC, the smallest element is only 2.1 cm wide - so the action is all in the center of the path. Your barlow seems to have a lens that takes most of the light path. There is no doubt that a TC seems to be a more sophisticated device which is designed for a DSLR while a barlow is designed for an eyepiece.

Jules

 

[Paul Corfield]

Been doing some more testing today. The 2" GSO 2X ED barlow works extremely well with the 1.5X teleconverter. I'll post some photos tomorrow. Also by using a couple of 60mm extension tubes I can get the magnification up to 4000mm and that's before the crop factor of 1.6X. Detail retention is excellent at long range which is mostly down to the barlow being very good at resolving fine details plus there isn't much glass being used to reach this magnification. Only 2 glass elements in the barlow and 4 in the teleconverter. The order I put the extension tubes in was one between the camera and the 1.5X teleconverter and the other one between the teleconverter and the barlow.

Paul.

 

[maxxxx]

Paul,
This thread has gotten so long that I have lost track of what scope you are using in your last series of shots?
And also what is the presumed effective focal length for these shots and at what aprox distance?

thanks,
Maxxxx

 

[wings]

I agree with maxxxx. Paul, what setup do you use to get 4000mm? That's amazing!
Also, please educate this newbie on how you arrive a those numbers. Help much obliged.

 

[Paul Corfield]

Paul,
This thread has gotten so long that I have lost track of what scope you are using in your last series of shots?
And also what is the presumed effective focal length for these shots and at what aprox distance?

thanks,
Maxxxx

The scope is the same Skywatcher Evostar Pro 80ED. They were taken with just the 2" GSO 2X ED barlow. The scope is 600mm and with the barlow lens cell screwed into the 2" nosepiece of the T-Ring the 2X barlow gives a little more magnification than my 2X teleconverter.

So that would be just slightly more than 1200mm before the crop factor. Range for all the photos was 15m and that was measured. All these shots have been cropped just to show the detail captured on the bird. Camera was Canon 450D and all photos taken in RAW.

Wings - the way I arrive at the magnification is to take a photo of the same target using the scope at prime focus which in my case is at 600mm. Then I take another photo with the combination of barlow/teleconverters. In Photoshop I scale up the 600mm photo and overlay it onto the other one. I apply some transparency to the top layer and see how well they match up. It takes a few goes to get the scale just right but once a perfect match is made I make a note of the percentage needed to get that match. If I needed to increase the 600mm photo by say 530% then that converts to 600mm X 5.3 = 3180mm

Paul.

 

[maxxxx]

OK. So it looks as though your last pics were taken at about 38x. Does that sound about right to you?

 

[Paul Corfield]

OK. So it looks as though your last pics were taken at about 38x. Does that sound about right to you?

Yeah, that sounds about right.


Some decent weather today so plenty of time to play. All the photos below were taken of a target at approx 35m range an I think there's a fly on the light in all the photos to use as a comparison. Using the 600mm photo as a guide, the last photo with the most magnification is around 400% bigger or about 2400mm before 1.6X crop factor.

All the photos apart from the first one were taken with just the 2" GSO 2X ED barlow.

All photos are uncropped, just resized to 1024.

1st photo is prime focus.
2nd photo is with the barlow mounted close to the camera via the t-mount.
3rd photo the magnification was increased by adding a 60mm extension between the camera and the barlow.
4th photo had a 180mm extension tube between the camera and the barlow. I haven't posted one with 120mm extension tube but it is quite similar to the 180mm.

Initially the first 60-120mm extension tubes provide quite a good jump and then it tapers off quite quickly. You don't get such big jumps in magnification once you start adding even more extension. 60-120mm is about the ideal. The 180mm one is similar to what 120mm would show.

In all the photos however the resolution stands up very well. I couldn't get as a good a quality by using the barlow in combination with teleconverters, too much glass. I should think in most situations the barlow either alone or in combination with extension tubes would cover all the ranges where a good quality photo can be achieved with digiscoping. Also because the resolution with the barlow is so good the photos can stand a lot of cropping, even at 100% they are usable.

Paul.

 

[JGobeil]

Great pics Paul - I guess I'll have to get one of those barlows and some extension tubes !

Regards
Jules

 

[TenaCJed]

I am really interested in doing this as well. I currently have a Canon Rebel XT and may get a 40D soon. I have been looking at getting the Celestron 80 ED APO Refractor Spotting Scope. I do have a quick question. How are you guys hooking this up to the camera? I know you need the adaptor for the camera, but how from the Telescope is everything hooked up. Do you use a diagonal, or go directly from the scope's focuser to the barlow / extension tube / camera mount? If you do not use a diagonal, is the image in the viewfinder correct, or is it reversed?

Thanks for the help, really interested in this setup.

 

[Paul Corfield]

I am really interested in doing this as well. I currently have a Canon Rebel XT and may get a 40D soon. I have been looking at getting the Celestron 80 ED APO Refractor Spotting Scope. I do have a quick question. How are you guys hooking this up to the camera? I know you need the adaptor for the camera, but how from the Telescope is everything hooked up. Do you use a diagonal, or go directly from the scope's focuser to the barlow / extension tube / camera mount? If you do not use a diagonal, is the image in the viewfinder correct, or is it reversed?

Thanks for the help, really interested in this setup.

Going straight through the scope or with a barlow or teleconverter attached the image will always be up the correct way in the viewfinder. You don't need a diagonal.

The correct method from the scopes focuser is to have the 2" scope adapter connected to a macro extension tube, 60mm long is about right to get focus from infinity down to around 4 or 5m. Everything else like a barlow or teleconverter then joins to the back of that. For a 2" barlow you would mount as in my photo description a few posts up this thread.

Paul.

 

[Derry]

Tena,, here is a photo of my Oly E3 on the back of my TeleVue TV85 scope,,

I have the T mount to the camera and then there is one spacer to allow me to focus closer than the scopes focus rack will move,, for father distant objects the spacer/extension tube would be removed and just the T mount would be used,,

Derry