Celestron C90 + Nikon Coolpix 4500 = Vignetting + Black Spot in Middle (1 Viewer)

Just getting into true digiscoping after years of just messing with an 8x "teledapter" on my Nikon Coolpix 4500. Ordered a nicer tripod with a fluid drag head, and decided on the Celestron C90 for a budget scope.

So I thought I needed the Celestron T-adapter, but I guess the new one like I got doesn't need it. So I have the step-ring attached directly to the visual back and the Coolpix 4500 and I'm seeing a black spot right in the middle of the visual field that won't go away.

Also the vignetting is severe...like staring down a tunnel with only maybe 1/3 of the visual field being the actual image.

I'm guessing that instead of photographing directly off the back of the scope that I need to be photographing off the eyepiece? If so, what do I need to make that happen?

I dunno, just knowing I'm missing and/or misunderstanding some piece of the puzzle, so my apologies if I seem confused.

Can anyone give me some advice?

Thanks in advance,

Kevin

Hi Calvin,

Welcome to the realities of digiscoping, where nothing is simple or easy and great pictures are really rare.
The Celestron you have is a reflecting telescope, so when you take pictures directly from the back, the reflector shows up as a black spot in your images.
If you use the eyepiece, the black spot drops out but the impact is distributed across the total picture. You did not think it would just go away, did you?
A good eyepiece will help form an image with less vignetting and no black spot, but the offset is a darker, less sharp image. No free lunch here either.
The whole discipline has lots of complexities and gotchas, way beyond my competence.
My best suggestion would be to read up on the topic here and perhaps at sites such as cloudy nights or astronomy review, to find some kindred spirits to discuss things with.
All the very best!

Thanks for the welcome!

Yeah, I knew there would be compromises, since I don't have that big of a budget (comparatively to some folks). I've been taking some rather grainy images with a Crystal View 8x teledapter of some juvenile white-tailed kites and enjoying that, so anything else is an improvement...and the 90mm Celestron will probably not seem very "dark" compared to my current setup.

I'm not looking to contribute to a stock photo house or get into National Geographic. Just take shots of animals (not just birds) from farther out where they won't get scared and run away. I can get alot of enjoyment even from dark, grainy images.

But it does sound like my best bet may be be to shoot from the eyepiece with something like an Eagle Eye DigiMount? Also have seen some mentions of using the macro mode when shooting in that fashion?

Even my current images have benefited a great deal from using the many (and identical) camera setup instructions for the Coolpix 4500...I'm glad the camera I already had is a favorite amongst digiscopers.

Thanks!

You will definitely need to shoot through an eyepiece, there's no other way to do it on the type of scope you have. The focal length of the scope is already 1200mm so I'd use quite a low power eyepiece. Something like a 30mm or 40mm would probably be about right and should give quite bright views. Divide the focal length of the scope by the mm of the eyepiece and this will give you the magnification power. So 1200mm/30mm would give 40X and 1200mm/40mm would give 30X. A 40mm eyepiece would be about right I think, coupled with the mag from the camera. Try the different modes on the camera, macro will probably work best.

Paul.

Thanks for the great info Paul!

Your calculations match the "39x zoom" I was seeing others mention for this scope given the 32mm eyepiece it comes with. Also thanks for confirming using Macro mode, easy enough to change and try.

I think 39x is going to be plenty considering I've been fairly happy with 8x, despite the small diameter lens/teledapter I was using. But of course once I can see/photograph X far away, I may be wishing for X+...seems to be the nature of most hobbies of this sort.

I ordered a universal camera adapter that I hope will work, but it won't arrive until next week. This weekend I can't wait to see my friend the white-tailed kite up-close, even if I might not be able to photograph him that close just yet (unless I get brave and shoot hand-held through the eyepiece). Been photographing these two kites every weekend for a month now with my current meager setup. Beautiful raptors, much more striking than our usual turkey vultures.

CalvinFold said:

But of course once I can see/photograph X far away, I may be wishing for X+...seems to be the nature of most hobbies of this sort.

Click to expand...

This is generally the way this hobby goes and it's quite natural to want to do this. A lot of money can be wasted before you realize that what you started off with was probably the limit anyway. There's a point with high magnification where you soon reach zero gains in quality and things start to go downhill. The air has imperfections such as haze and worst of all is the shimmering air currents as the sun heats the air. As you ramp up the magnification all you do is magnify the imperfections in the air and they become much more apparent. A subject photographed with less magnification that only fills half or quarter of the frame will often look better than one that fills it completely. Also the higher you push the magnification then the more you will notice any slight vibration in the equipment from wind or pressing the shutter. You might want to use the cameras timer if this is the case. Shutter speeds also drop dramatically if you push things too much and then vibrations also become a factor.

Paul.

Sounds like all the more reason to stick with what I have. This is more of a part-time hobby of personal enjoyment (not really out to impress anyone else) and I'm quite bit less "hard core" than many folks here. Your message rings true with my personal outlook for digiscoping.

At best, I might look at buying a 40mm eyepiece at some point, there is quite a bit of merit in my case of having access to a bit LOWER magnification at times. So thank you for all the math info and advice so I can make smart, reasonable choices.

Funny you should mention the close-in vs. the wide. I hadn't considered that...I actually like to take shots where there is background around the animal...some "reference" or "environment." So I'm not aiming for "bird fills the frame" (unless it happens that way), I'm just aiming for "oooh, I can get a picture of that bird from waaaay far away when before I couldn't."

(The problem of parks in urban areas is the crowds of people scare the wildlife away from the trails. So I just want to be able to take photos of animals that are far away enough to ignore the people, cyclists, etc. and say "see, this is in our own back yard." Also why I get up and go take photos in the hours after sunrise before the world wakes up.)

Thanks for all the info and "outlook." Sorry for the slightly OT blabbing...I'll report back my results once I get the scope out into the field an take some photos.

First try this past weekend: much better luck from the eyepiece, though I had issues with dark photos which I think was the camera being off-center from the eyepiece, very fiddly getting that right. Also seemed to work better with the camera in Landscape (or auto) rather than Macro mode (photos less dark).

And figures after I bought the Universal camera mount that I found someplace still selling the DigiMount adapters for the Nikon Coolpix 4500, and right here in California, no less (DigiMount UK isn't answering emails). So that's on order, and was my preferred solution anyway.

Thanks to everyone for the advice to go after this via afocal photography.