24.05.2020 Testing-testing..

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I thought it might be interesting to test the result of camera zoom on image quality. Sadly it was the same, heavy overcast as yesterday. Moreover I placed my test subject in the shade of a tree.

The test piece was an A4, black and white, crisply printed, illustrated guide to plumbing fittings. At 24 meters [26.25 yards] from the target the telescope was placed on its tripod.

Visually, I could easily read every word, at all powers. Just as if I was standing right in front of the target.

Then I attached the camera. Minimum camera zoom [5mm] caused vignetting. The dark corners only disappeared with increasing camera zoom.

Medium camera zoom [10mm] provided excellent sharpness and fine black and white images. Full camera zoom [20mm] produced violet print at all powers instead of black. This means that I must zoom the camera and telescope carefully according to my needs. 

Then I went back out again and retested at my maximum clear baseline of 56 meters [61 yards.] Hedges intervene on potentially longer lines of sight. It was windy outside the shelter of the garden so I had to peg the target firmly to the tripod. This caused some creasing. Visually I could read the bolder text at 60x but it rapidly became too small to read at lower telescope powers. It wasn't possible to read the normal text at this distance at any telescope power.

See applied image labels above for details of camera and telescope combinations.
All images reduced from 4000x3000 to 1000x750. [Left click for enlargements.]

Telescope's nominal power.......................................27, 40, 50 & 60x.  

Effect of camera zoom at 5, 10, 17 and 20mm:  Ixus 117 sensor is 11mm.
Camera focal length /sensor diagonal.                                                                                                                                             

  5/11 Reduces the telescope power by 0.45x..........12, 18, 22 & 27x.

10/11 Reduces the power by 0.9x............................24, 36, 45 & 54x.

17/11 Amplifies the power by 1.5x............................40, 60, 75 & 90x.

20/11 amplifies the telescope power by 1.8..............49, 72, 90 &108x!

The Ixus117 does not give actual figures for zoom on the camera screen. Just a slider and guesswork. The actual focal length has to be read off the details later. Which are provided by image cataloguing software like Google's Picasa. Microsoft's OneDrive Photos shows the basic details. Google Photos the same, under Info.

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24.05.2020 Thoughts on optical quality and digiscoping:

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Given that I am a beginner with the new kit, perhaps I am being too unkind to my Vortex Razor? Vortex has a good reputation but without the premium optics, premium price tag.

Their Razor 85mm is their top spotting scope model and by no means inexpensive. Mine is the later "improved model" with the large focusing collar around the body.

Yesterday's weather  conditions were certainly not ideal due to a lack of sunshine. Longer exposures in [relatively] dull conditions are the enemy of digiscoping because of the very high powers involved.

This can be directly related to very long telephoto lenses. In the 1000s of millimeters range! The slightest vibration can cause softening of the image. Long exposures will amplify any atmospheric effects like mirage and certainly won't freeze subject movement. The birds' feathers and the grass, water and trees were all in constant movement yesterday.

The 85mm Swarovski and Zeiss models are more than twice the price of the Vortex Razor! Is that the price one has to pay for true APO correction? Colour error and softness of the image are not nearly so noticeable when used visually. Even the experienced human eye is far more forgiving than a camera.

Though now I better understand why the "serious" people choose the top names in optics. The very high price is built on a potentially fragile reputation. It should guarantee the highest quality and the most stringent quality control. If it leaked out that there was "variability" the very high prices and advertising claims would begin to look like empty hype. The internet can spread rumours like wildfire!

The general view of the lake from where I was standing yesterday. I held back behind the nearest shrubbery to avoid startling the distant birds. 

As can be seen, a small field lay between the lake and myself. The cloudy sky is obvious too. 

That said, there are always unhappy customers who found better optics elsewhere. From makers like Kowa and Pentax and many others. They have returned the big names equipment as unsatisfactory at the very high asking price. I have read a lot of reviews and forum posts recently. Plus all the birding/hunting YT reviews of course. All in my search for affordable [within my own budget] digiscoping [afocal] equipment.

I can rely on my 60 years of astronomical, optical experience and photography to judge the value of personal opinions or commercial reviews. Many of which are just sales hype to move product. They use the same terms for all of the equipment they sell. Many of the terms are borrowed straight from the manufacturer's own [sales] websites. This doesn't help anybody make valid or useful comparisons.

Dimensioned photo of the lake for scale. The nearest point was 125 yards away.

I have been taking pictures though my astronomical equipment for many decades. Including birds , animals and landscapes. Digiscoping is not remotely new in that sense. It has always been done by amateur astronomers wanting more power. [Magnification] The technique even had a name: Afocal photography.

The arrival of the digital camera just made it far more popular and affordable for terrestrial subjects. Particularly as Asian optics spread prices for equipment steadily downwards to more affordable levels.

The enormous advantage of digital cameras [over film] is that you can take literally hundreds of trial images at no extra charge. Hopefully you learn more rapidly from your mistakes. With film the cost was so high that it severely limited how many exposures one was ever willing to take.

If you relied on the local chemist or camera shop for processing it could take a week to get your prints back. There was little chance to improve your skills by repetition or trial and error. With digital you can just keep pressing the shutter until you grow old and tired. Hopefully learning what works and what doesn't along the way.

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