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Old Oct 21, 2004, 8:22 AM   #1
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Ok here's the problem i own a 90mm celestron (C90 Mak) spotting scope which was originally bought just as a spotting scope and i'm attempting a little digiscoping with it.

I'm having difficulty getting high enough shutter speeds in apeture priority mode (aperture set at 5.1) to prevent the image from being too blurred (the tripod is not the problem its a manfrotto 055 with 701-rc2 head)

using a coolpix 4500 with a solid adapter setup.

anyways i was just wondering what the blame is here, it is a pretty miserable day today, very cloudy and so lighting is not the best so is it that or is it the scope.

the scope specs...

90mm lens at the front
focal length of 1200mm

so yeah just wondering what the specs are on other scopes especially focal length and f/ value so i can figure out if its just a bad day for digiscoping or is it a bad scope and its never going to be a good day.

Hope someone can help

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Old Oct 21, 2004, 8:23 AM   #2
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Well been out today again at around lunch time and its been fairly bright and I've been taking some readings of what shutter speeds I can achieve with different settings pointed at sun lit areas, the brightest I could find and so here are my results...

Firstly working with no camera zoom and so some vignetting at f/2.6 (aperture priority mode)

ISO 100 gave me speeds of 1/30
ISO 200 ......................... 1/60
ISO 400 ......................... 1/125
ISO 800 ......................... 1/250

Secondly I zoomed in enough to eliminate the vignetting and ended up at f/3.7

The highest shutter speed I was able to achieve at ISO 200 (what Andy recommended I switch to) was 1/60 and very rarely 1/125 (think I was pointing directly into the sky at that point)

SO the question still remains, is the scope simply not up to the job due to its large focal length and therefore its small f/ value (f/13.3)

I've calculated the f/ values (focal length/objective diameter) of some other scopes both astro types similar to my celestron c90 mak and some regular spotting scopes.

I've not been able to find out the full technical specs of the more popular digiscoping scopes such as the zeiss, swarovski, kowa etc but I'm assuming as they are all refractor scopes then it'll be roughly equivalent to the scope body length.

Anyways most of the dedicated spotting scopes I've came across all come out at about at most f/6 and all astro type scopes and reflectors are all above f/9 with my own scope being a tiny f/13.3

Ok so basically this whole thing is just for someone to validate my thoughts that my scope will just never going to be able to achieve fast enough shutter speeds to take any decent wildlife photos through it.
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Old Oct 22, 2004, 4:01 PM   #3
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Hi Steve

I have a Swarovski scope, either F10 or F13. What do I do?

My camera is a DSLR, everything set to manual. ISO: 500

Plus I shoot in NEF. I wish I could use a higher ISO, but the results become to noisy.

With the F10 on a sunny day I shoot at ASA 500, usually about a half F stop to low, so I push it a bit in the NEF converter. Excellent results!

Sometimes the results are perfect because of the subject location etc.

Today was cloudy, not heavy clouds but light, shot at ASA 250, or 160 depending on the subjects location, once again excellent results.

With the F13 adapter I have to, of course compensate even more...

However NEF still allows me to push the shots two stops, although this gets a bit grainy. zSo I ususally shoot at ASA 400 for sunny days and push the shots a stop and a half. Cloudy days, you MUST use a tripod.

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Old Oct 23, 2004, 9:22 AM   #4
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Sorry about putting ASA in front of the speed I am shooting at - Early Alzheimers....

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Old Nov 3, 2004, 1:13 PM   #5
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Hi Steve,

It depends on what the wildlife is doing. With digiscoping you generally will not be able to get shots of wildlife moving without motion blur, but if they are standing still, you can usually get excellent results even with reasonably slow shutter speeds and low ISO's.

There are two factors which play into a successful image. First you must have a rock solid tripod and second you really need to get a remote release. My suggestion is to get the Harbortronics DigiSnap 2000. This remote lets you zoom set autofocus with the half press and trip the shutter. Forget conventional widsom of trying to use 1/focal length for shutter speed and don't go over ISO 200. Actually, I get great results with my Meade ETX-90 and CP4500 which has approximately the same F rating as your Celestron.

Another thing you need to realize is that even if the capture is quite dark, you will be able to pull it up with levels in PhotoShop and minimize noise if necessary with noise reduction software.

I also use the Swarovski ST-80 HD for digiscoping and it is "slightly" faster than the Mead and your Celestron but not all that different. Thenative focal length of the Meade ETX-90 is1250mm while the Swarovski is468mm. By usinga William Optic DCL-28 (dedicated 24mm eyepiece) I can use nearly theentirezoom range of the CP400 and still get very usable shots witheither scope.

Best regards,

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