Testing prime focus digiscoping setups (1 Viewer)

Paul Corfield · Jul 8, 2008

2X Aico 7 element teleconverter performed very nicely for this one. Sharper than the 4 element 1.5X Vivitar I used on the last test.

edit - As a comparison to the unprocessed RAW file I also posted a full size crop showing the RAW file after processing in Adobe Lightroom. You can see how well the RAW file comes up after some very basic editing. The Unprocessed RAW files in the Canon 450D can look slightly soft I think but the detail is there to be brought out.

Make and model of DSLR: Canon 450D
Make and model of scope: Skywatcher Evostar Pro 80ED
Make and model of converter or barlow: 2X Aico 7 element Teleconverter
Type, make and model of camera adapter: T-Ring with 2" scope adapter, both unbranded
Length of spacer needed to reach focus: 60mm
Focal length of complete setup in mm: 1920mm after crop factor of 1.6
Measured distance between target and telescope in meters: 15m 13cm
Evaluated resolution number: 20
Speed setting of camera: 1/60sec
ISO: 400
Original picture format (RAW, JPG) and resolution (mpx) RAW 12.2 million pixels
Date and time: 8th july 10:08
Weather conditions (sun and wind): Sunny but target was in shade, breezy but garden is sheltered.
Other pertinent information:[/QUOTE]

Paul Corfield · Jul 8, 2008

For this one I used my cheap, unbranded 2X barlow. Worked very well, nice and sharp even on the unprocessed images. A little bit of CA but that is understandable with such a cheap barlow and inferior multi coatings. CA not noticeable when photo is reduced in size. Compared to my 2X teleconverter I had to move the scope around 1m closer to the target which suggests the barlow is a little under its stated 2X power.

Make and model of DSLR: Canon 450D
Make and model of scope: Skywatcher Evostar Pro 80ED
Make and model of converter or barlow: 2X barlow, unbranded and mounted inside old teleconverter housing
Type, make and model of camera adapter: T-Ring with 2" scope adapter, both unbranded
Length of spacer needed to reach focus: 60mm
Focal length of complete setup in mm: unknown, slightly less than 2X teleconverter
Measured distance between target and telescope in meters: 13m 83cm
Evaluated resolution number: 20
Speed setting of camera: 1/800sec
ISO: 400
Original picture format (RAW, JPG) and resolution (mpx) RAW 12.2 million pixels
Date and time: 8th july 16:23
Weather conditions (sun and wind): Sunny with target in full sunlight, breezy but garden is sheltered.
Other pertinent information:

mouz59 · Jul 8, 2008

Target too Weak?

Hey guys, i"m Mike- Vandit recommended me to this site from Canon POTN.

I too, have been testing optics-

I will gladly contribute to this thread once i shoot some pics of your target, however, i personally think the target is on the weak side.

I use the Koren 2003 lens test chart- it is a PRESSURE COOKER for ANY lens! goes all the way from 0-200lp/mm across a 25cm spread.

a pic of the Koren target shot with my Astro-Physics telescope:

Canon EOS 1d Mk III
Astro-Physics Starfire 102
Astro-Physics prime focus camera adapter PFCT
813mm f8
16.5 Meters distance
ISO 100
RAW file
Shot in my basement

Resolved >100 LP/MM!! - actually went OFF my reference chart! - I need to adapt the chart for these high end optics. In comparison, the 200mm F2 L canon was around ~86LP/MM.

mouz59 · Jul 8, 2008

The web page of the Koren test chart..

http://www.normankoren.com/Tutorials/MTF5.html

ostling41 · Jul 8, 2008

mouz59 said:
The web page of the Koren test chart..

http://www.normankoren.com/Tutorials/MTF5.html

This is a very impressive chart. It goes to a point of where no lens system can be expected to resolve, showing a definite delineation between "go" and "no go." It allows calculation of MTF.

Many of us may not have an inkjet good enough for printing it, though.

Paul Corfield · Jul 8, 2008

ostling41 said:
This is a very impressive chart. It goes to a point of where no lens system can be expected to resolve, showing a definite delineation between "go" and "no go." It allows calculation of MTF.

Many of us may not have an inkjet good enough for printing it, though.

They do versions for different inkjet printers and also corrected versions to allow for 0.25 of ink spread. Should be able to get something that prints fairly well.

I agree, looks like a nice chart.

Here's the link again seeing as we are on a new page.

The web page of the Koren test chart..

http://www.normankoren.com/Tutorials/MTF5.html

Paul.

Derry · Jul 8, 2008

Mike, great read on that web page on testing lens,, is that your AP Starfire add on Astromart,, LOL

how do we know what our HP inkjet printer is able to print at for selecting the correct chart,,??

Derry

Paul Corfield · Jul 8, 2008

Derry said:
Mike, great read on that web page on testing lens,, is that your AP Starfire add on Astromart,, LOL

how do we know what our HP inkjet printer is able to print at for selecting the correct chart,,??

Derry

For inkjet printers it says to use the .25 correction. For the HP printer you would need -

5mm, 1.5, 0.25, 5906 which is http://www.normankoren.com/Tutorials/Lenstarg_50_5906p_15g_25is.png

Paul.

Derry · Jul 8, 2008

tried the Korean test chart,, did two photos as wanted to see if the resolution was better in the center of the scope, see center photo,, use the 10X on live view on the camera for final focus,,

line readings on my original photos,, have 24" HD monitor,,
full test chart photo I can read to about 110 lines,,
on the second photo I can read to the 200 lines,, see third photo which is a small area crop from the center photo,,

reducing them to post here the resolution certainly suffers,,

Make and model of DSLR: Olympus E3
Make and model of scope: TeleVue TV85
Type, make and model of camera adapter: Olympus 4/3 to OM T mount
Length of spacer needed to reach focus: 50mm
Focal length of complete setup in mm: 600mm (camers has 2X crop)
Measured distance between target and telescope in meters: 10.m
Evaluated resolution number:110 lines to 200 on original photos
Speed setting of camera: 1/200 sec
ISO: 100
Original picture format: RAW then to JPEG, final 9.56 million pixels
Date and time: 2008-07-08 14:00
Weather conditions: partly sunny, temp 92F and RH at 86%, kind of muggy

mouz59 · Jul 9, 2008

lots to say, and no time!

No, my Starfire isn't on Astromart- there is one on there for $400USD less than what i bought mine for, which makes me kinda jealous!

I'm attaching a copy of my recent science fair project which outlines my procedure for testing. It's not the same as the Koren test chart, but it's alot simpler. - and will save me alot of time typing my procedure out on here...

oh, and concerning the printing- i printed mine out straight with my Canon iP6700D on Brilliant Luster paper from Calumet Photo. I might try it on a fine art or high resolution paper here soon from Hahnemuhle- I'm really digging' their fine art canvas paper.

i'll post all my data from all tested lenses in the next day or two. In the mean time, keep the tests coming!

Mike

mouz59 · Jul 9, 2008

? awesome..

Thats some INSANE resolution!!! - I think the smaller sensor with more megapixels plays a large part.

kinda scared that a TV85 can out-resolve my Starfire.... thats scary... really scary. - and not even possible, right? Dawes Limit... it has to be the crop sensor and the distance.

whatever, mine is "vintage" anyway ; )

Derry said:
tried the Korean test chart,, did two photos as wanted to see if the resolution was better in the center of the scope, see center photo,, use the 10X on live view on the camera for final focus,,

line readings on my original photos,, have 24" HD monitor,,
full test chart photo I can read to about 110 lines,,
on the second photo I can read to the 200 lines,, see third photo which is a small area crop from the center photo,,

reducing them to post here the resolution certainly suffers,,

Make and model of DSLR: Olympus E3
Make and model of scope: TeleVue TV85
Type, make and model of camera adapter: Olympus 4/3 to OM T mount
Length of spacer needed to reach focus: 50mm
Focal length of complete setup in mm: 600mm (camers has 2X crop)
Measured distance between target and telescope in meters: 10.m
Evaluated resolution number:110 lines to 200 on original photos
Speed setting of camera: 1/200 sec
ISO: 100
Original picture format: RAW then to JPEG, final 9.56 million pixels
Date and time: 2008-07-08 14:00
Weather conditions: partly sunny, temp 92F and RH at 86%, kind of muggy

Derry · Jul 9, 2008

Mike, know about Dawes limit,, my 3.5 Q has exceeded it several times in past years splitting doubles on a good night,, there has been some bright sunny days that the Q can resolve more detail than my TV85,, was looking at a small hex head nut on a power transformer about 1/4 mile away,, could see it with the TV85 but not definer it as a hex head,, the Q is from the early 1990s and my TV85 is about nine years old,,

as you can see there is roll off when looking at the first photo toward the edges,, have never been able to see that while observing or in any of my bird photos,, guess the verticle lines are tougher to resolve than a bunch of bird feathers,,

have an adapter arriving tomorrow to mount the E3 and one of my camera lens (Oly 50mm) behind the various TV eyepieces for some real high power,, would imagine air disturbance is going to play a roll when we get into those test,,

interesting reading on the science fair project,, nice work,,

Derry

mouz59 · Jul 9, 2008

3.5Q ?? Questar 3.5? not sure what your referring to, sorry.

anyway, I'm gonna re-shoot my target at a closer distance and see what i get. should be alot better resolution (but not necessarily fair). also, the E-3 has MUCH smaller pixels- 4.7u as opposed to 11u ... and you also are talking about a much smaller chip- and we dont know what kind of in camera processing is going on. Regardless, the photos are SHARP! Maybe i should rent a E-3 from Calumet and see my results. - although the 40d has a 5.7u pitch, which is alot closer.. and my buddy has a 40d. Hopefully i can get him over by Sunday and get the results up.

yeah, Oly lenses on the back of the scope? that'll be interesting for sure. - probably will hurt your image quality, but should get you VERY close to distant objects, which will be interesting. Hope you post up some pics!

Derry · Jul 9, 2008

Mike, yes the Q is a Questar,, this is my second one,,

also had a 12.5" f5 Portaball when we lived in Florida,, very interesting scope and what resolving power with those Zambuto mirrors,, could see the central star in M57 (Ring Nebula) on a good cold night,,

will be interesting to mount the Oly glass on the scope,, they make some extremely good lens in the pro line,,

Derry

mouz59 · Jul 9, 2008

Not surprised- Questar is probably (i dont know for sure, never used one) on par with AP- there all custom built hand figured, right? kinda wanted one back in the day, but I'm content with what i have. The Portaball sounds intriguing too- saw one at a astro convention once, adn i must say, i was impressed.

anyway, the resolution figures in my project are crap because i shot outside on a windy day. I just went with it anyway because it proved a point. The figurees i'll be posting soon are all MUCH better data- shot in the basement, hence a much more controlled environment.

Paul Corfield · Jul 9, 2008

mouz59 said:
oh, and concerning the printing- i printed mine out straight with my Canon iP6700D on Brilliant Luster paper from Calumet Photo. I might try it on a fine art or high resolution paper here soon from Hahnemuhle- I'm really digging' their fine art canvas paper.

Mike

I printed my test chart onto Hahnemuhle Torchon 285gsm paper using my Epson 2100. Comes up really nice. Been using the Hahnemuhle paper for years and really love the quality it produces.

Regarding lenses through eyepieces, in all the tests I've tried the teleconverters have always beaten lenses by quite a bit as far as details resolved, probably because of the amount of glass involved in eyepieces and lenses. With lenses and eyepieces the light really sufferes for birding purposes and the magnification is on a similar level to that of teleconverters. The weight is a major issue too. Just sold all my lenses on ebay to pay for more barlows/teleconverters. :t:

Paul.

Paul Corfield · Jul 9, 2008

Here's a 100% crop of the Koren chart taken through my Skywatcher 80ED with the Canon 450D. Chucking it down with rain here so I had to take this one indoors which was lit with just a couple of bulbs. Range was 6m 20cm which is a similar range to my photo of old chart. Resolved the lines all the way to 200.

Paul.

JGobeil · Jul 9, 2008

Duplicate post - see below. Sorry....

Jules

JGobeil · Jul 9, 2008

Hey guys, don't you think we are a bit fast !!!

We can't change the target in the protocol at will. Let's not forget that the reason for this protocol is to define a standard way of testing digiscoping setups.

So far, we have tried 2 targets - the standard ISO 12233 target and one that I made derived from the first one. IMO, both are inadequate: the first one is impossible to print with a home printer and the second does not allow small enough resolutions as demonstrated by Paul's 2X barlow and 2X teleconverter that still resolve maximum resolution with his scope and camera.

Should we use the Koren target ? I am not sure !
Can it be printed at home ?
Can it measure resolution in the corners ?
Can it evaluate chromatic aberration, a most important characteristic ?
This target is copyrighted !

I don't mind changing the protocol - this is OUR protocol, not MINE - I only had the privilege of writing it (and I'm perfectly willing to give the job to somebody else...) !

Paul Corfield · Jul 9, 2008

I quite like the chart we have now as it pretty much covers everything that we want to test. All my tests so far have been under 20m which isn't really taxing the scope or any of our scopes so I guess we need to increase the range. I would normally use a 2X converter at around 30m and beyond. Maybe we should get to the point where the test chart fills the frame and then move an additional pre determined distance, say 15 or 20m or maybe find out at what range the current chart starts to fail and use that as a guide.

The Koren chart is ok to print and has some very fine lines but for what we want to do it's unsuitable in that the finest lines are way off to one side and it doesn't test all the corners for softness. Plus as we have already shown it's still fairly easy to resolve all the lines at the ranges we are already experimenting at.

edit - comparing the lines on our current chart with the Koren one I'd say our chart is around the 150 range so it's already testing quite fine detail.

Paul.

Testing prime focus digiscoping setups (1 Viewer)

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