Some digiscoping experiments with a dslr (1 Viewer)

[TenaCJed]

Paul,
Thanks for the quick response and explanation. After I read you comment on the diag. it hit me that the mirror in that is what makes the image reversed.
Any recommendation on where to get the extension tube? Is it a telescope extension tube or cameray? The camera tube's add a bit more to the cost compared to telescope tubes.

 

[Paul Corfield]

Paul,
Thanks for the quick response and explanation. After I read you comment on the diag. it hit me that the mirror in that is what makes the image reversed.
Any recommendation on where to get the extension tube? Is it a telescope extension tube or cameray? The camera tube's add a bit more to the cost compared to telescope tubes.

Either way they can both be found inexpensive on ebay. Nice quality GSO telescope extension tubes can be found cheaply from either of these sellers.

http://stores.ebay.com/SMARTASTRONOMYS-TELESCOPE-PRODUCTS

http://stores.ebay.com/Agena-AstroProducts

I'd probably get both the 50mm and the 35mm. They do an 80mm one as well but I'd avoid that one because on the Celestron scope it will not let you get infinity focus but it would let you focus down to around 4.5m. Most of the time you could just use both the 50mm and the 35mm together and when you want to get to infinity you would just remove the 35mm one. If you only wanted to get one now and one later on then get the 50mm one first.

The camera macro extension tubes are handy for mounting teleconverters/barlows in various positions away from the camera to increase magnification. I got one of the cheap oriental imports which are found easily on ebay. Because they are cheap they only screw together but apart from that they are fine for the price.

For the 2" camera mount, the one that Jules uses is a nice one and can be found here. You could go the other route of getting a t-ring and 2" adapter but it would work out roughly the same in the end as far as cost goes.

http://www.cncsupplyinc.com/homepage.htm#TRUE2

Paul.

 

[TenaCJed]

Derry, thanks for the info and the picture, pictures always help.
Paul, thanks again for the info. Already looking at the GSO barlow you have, so the GSO tubes might be the way I go. I would like to get the tubes that work with my camera(electronics), but that is a bit more then I am looking to go for right now. Thanks for the info on the camera mount, I like the look of that.

 

[Paul Corfield]

The camera electronics can't communicate with the scope so it's only worth getting expensive tubes with the electrical contacts if you also wanted to use them with lenses.

Paul.

 

[TenaCJed]

The camera electronics can't communicate with the scope so it's only worth getting expensive tubes with the electrical contacts if you also wanted to use them with lenses.

Paul.

That is why I would like to get get the kenko's, to use with current lens and doing the best macro I can with what I have have.

OK, just to make sure I have a firm understanding of what would be needed.

Scope adapter hooked into the focusing cell of scope, extension tube if used next, barlow, then camera T ring (is this also considered an adapter?) or the CNC EOS which I will most likely go with.

Does this sound correct? I just want to make sure I understand the extra parts needed. Unfortunately I am not familiar with telescopes so the picture posted a couple of posts back did not help me understand what is needed. If only there was an updated picture from the very first post that had lines showing what is what.

I thank you all for the help. Hopefully I can work it out and go this route to get some more reach. I have been very impressed with the pictures that all of you have been posting.

 

[Paul Corfield]

What you would have is (mounted in this order)

Telescope - telescope extension tube of whatever length needed to achieve focus - 2" scope adapter like the CNC one - dslr camera.

This is the basics that will get you up and running. After that you have options. The 2" CNC adapter has the camera bayonet on the back of it. This mean you can then insert teleconverters between it and the camera to boost the power of the scope by the amount that the teleconverter provides. With a 2" barlow like the GSO ED one you can unscrew the lens cell and screw it into the 2" CNC adapter. You can use this in combination with the teleconverter or on it's own. You can also mount macro extension tubes between the camera and teleconverters or between the camera and the barlow and this will also boost the magnification by quite a bit because the image is being projected to the camera ccd over a greater distance.

Paul.

 

[Derry]

Tena,,

1. T mount adapter, to attach to your camera body (Canon mount),,

2. T mount, attaches to the cameras t mount ring (may be able to buy a T mount with Canon bayonet)

3. Extension tube, would buy a 35mm & 50mm,, I have the 80mm and seldom use,, 35 + 50 = 85mm anyway,, again buy the 2 inch,, these do not connect to your primary camera lens,,

4. Barlow, the 2X GSO 2" that Paul has tested is working very good,, (not displayed below)

5. Telescope, any decent 70 to 100mm APO refractor will work fine,, scope will need to accommodate 2 inch,, some will only handle 1.25 inches,,

please take a look at Astromart in the classifieds in the telescope-refractor section,, always some very nice buys there and the astro folks are good people to buy from,,

http://www.astromart.com/classifieds/

you may also want to consider a teleconverter at some point,, for general use of the camera a 1.4 or 1.7 converter is very nice to acquire additional reach with the lens you are using for your general photography,, agree with Jules comment below on some issues with the non Canon converters,,

Derry

the below photos show the T mount adapter, T mount and extension tube,,

camera attaches to the item on the left and the right end goes into the telescopes eyepiece tube,,


......each piece ..............then how they fit together

 

[JGobeil]

What you would have is (mounted in this order)

Telescope - telescope extension tube of whatever length needed to achieve focus - 2" scope adapter like the CNC one - dslr camera.

This is the basics that will get you up and running. After that you have options. The 2" CNC adapter has the camera bayonet on the back of it. This mean you can then insert teleconverters between it and the camera to boost the power of the scope by the amount that the teleconverter provides. With a 2" barlow like the GSO ED one you can unscrew the lens cell and screw it into the 2" CNC adapter. You can use this in combination with the teleconverter or on it's own. You can also mount macro extension tubes between the camera and teleconverters or between the camera and the barlow and this will also boost the magnification by quite a bit because the image is being projected to the camera ccd over a greater distance.

Paul.

One must be careful with teleconverters. If you connect a TC to a DSLR like the Canons, it will expect a Canon compatible lens at the end of the TC. Of course, the scope is not Canon compatible and you will get an error message, rendering picture taking impossible.

In order to use one of those "automatic" TCs, a Canon 1.4X, I had to put a Canon compatible spacer between the 20D and the TC. I used the shortest one from the Kenko spacer kit for Canon. I then had to grind some metal from the bayonet mount and tape some of the electronic contacts on the spacer. It now works correctly with the scope but has rendered the spacer inoperative for "auto" work. If I had to do it again, I would have purchased a barlow instead.

The final setup is like this:

20D + modified Kenko spacer + Canon TC + EOS adapter + scope

Regards
Jules

 

[TenaCJed]

Thank you all very much for the help and recommendations. I am pretty sure I now know what I need to get, will just see if I can free up some funds.

Nevermind Jules, just reread your post and you are already taping the pins!!!!
Jules,
You probably could have just used the trick of taping the pins on the TC to get it to work. This method makes it so that the TC no longer reports to the camera, so there is no longer the expectation on what the lens is. I use this method on my Sigma 2X TC on my Sigma 100-300 F4 so that I can still get the focus assist flash and beep. I am not lucky enough to have auto focus work on my Rebel XT in this config, so I have my lens in manual focus. However it is still nice to get the focus assist since the viewfinder in the Rebel does not lend itself to manual focus very well.

 

[Paul Corfield]

Not had a chance to do much long range stuff but I spotted this Kestrel hovering in the distance from my house and it was just a small speck in the viewfinder. I'd say it was around a couple of hundred metres away.

Taken through the Skywatcher scope with the 2" GSO ED barlow and a 60mm extension tube between the barlow and camera to further boost the magnification.

ISO400 1/250 sec.

This is cropped from the original photo and reduced from around 1300 pixels wide to 800 wide.

Paul.

 

[Derry]

nice work Paul,,

never have any raptors hovering here just flying in slow circles hunting,, have tried a few photos but it will be pure luck if I capture one when using the big scope set up,,

Derry

 

[bluedubius]

Great spotting, Paul. The head on that Kestrel is remarkably sharp for that distance. Looks like a barlow is in the near future.

Rick

 

[JGobeil]

Thank you all very much for the help and recommendations. I am pretty sure I now know what I need to get, will just see if I can free up some funds.

Nevermind Jules, just reread your post and you are already taping the pins!!!!
Jules,
You probably could have just used the trick of taping the pins on the TC to get it to work. This method makes it so that the TC no longer reports to the camera, so there is no longer the expectation on what the lens is. I use this method on my Sigma 2X TC on my Sigma 100-300 F4 so that I can still get the focus assist flash and beep. I am not lucky enough to have auto focus work on my Rebel XT in this config, so I have my lens in manual focus. However it is still nice to get the focus assist since the viewfinder in the Rebel does not lend itself to manual focus very well.

No, taping the pins is not enough. I have tried it and is is well documented if you search on the Net. The 20D has a micro-switch that is turned on by the bayonet. This must absolutely be disabled by removing metal on one of the wings of the bayonet mount on the spacer.

 

[JGobeil]

Some bird pictures with my new scope yesterday. Attached are 2 taken with the teleconverters stacked, CANON 1.4X and 2.0X for 2509 mm or 50X, including a 1.6 sensor crop factor. They were lightly processed in PS but not cropped.

The first one was taken under dull cloudy conditions at 90 yards, about 80 m., and focus is not quite perfect.

The second one clearly demonstrate that chromatic aberration will pop up if conditions are right for it, as it is the case here with the sun behind the birds and lots of bright reflections. I wonder if a barlow would perform better than the 2.0X TC.

 

[Paul Corfield]

Pretty good Jules. I think your ED scope uses FPL-51 for the low dispersion glass which is probably why the CA is present to that degree.

Are your teleconverters Canon brand? If they are I wouldn't like to say if a barlow would out perform them.

Paul.

 

[RJM]

Paul, the type of glass element used is not the prime factor in color correction. True APO lens were made long before FPL53 was developed. The design of the lens and the mating elements are much more important.

Which leads me to my next point...the image you see is entirely formed at the objective. Pretty much any aberation seen such as CA, field curvature, astigmatism, distortion, etc. is due to the objective. The function of barlows, teleconverters, and eyepieces is simply to maginify the all-ready formed image. If made correctly, they should take away nothing from the on-axis image quality. Barlows and teleconverters are especially easy to make because of their simple 2-3 element design. However, the main issue with in-expensive barlows is poor baffling leading to glare and scatter, which you have discovered. Complicated eyepieces, can also add aberations to the image, but these are mainly off axis. But unless you are using a full-frame camera, these aberations will generally be outside the sensor.

Now all this said, in order to properly evaluate these telescope lenses/systems you will need to push the optics to limits of distance/magnification that are well outside the normal parameters used in most digiscoping situations. Like I said in another post, the resolution of your camera on axis will "give up" before the telescope probably will. Only the the latest 12mp and larger DSLRS will start to outresolve the typical telescope lens.

Finally, why I guess it could be interesting to experiment with different gear combos there is really nothing new to what you are doing. Tele Vue designed their Powermates years ago specifically for long focal length imaging. Simply unscrew the barrel and attach a T-mount. I myself have used the 2.5x and 5x Powermates on a 100mm Pentax F4 SDUF II Petzval telescope. The image quality is excellent, they are fast and simple to swap out, and you are not adding long extentions making for difficult-to-balance mounting.

Hope this helps,
Rick

 

[wings]

Jules, we have basically the same equipment, i.e., Canon 20D and Kenko automatic extension tube set, although currently I am digiscoping with a newly acquired Canon 590IS P&S and Kowa scope. I am less-than-satisfied with the focusing on the camera's LCD due to its low resolution and long setup time.

Since the 20D has bayonet mount, as well as the Kenko tubes, what mounting ring would I need that would connect the camera/extension tube assembly to the Kowa scope eyepiece end which is threaded? and where can I get such a ring? The way I see it, this ring would have to have threads on one end and a bayonet mount on the other. Also, do you need a long track support to take up all the weight of camera and assembly off the scope eyepiece connection?

Dennis

 

[RJM]

Dennis, the easiest and best way to connect a DSLR to a Kowa fieldscope is with the Kowa TSN-PA2 camera adapter. Here it is with a Nikon D40 on 663 Prominar:

cheers,
Rick

 

[JGobeil]

Paul, the type of glass element used is not the prime factor in color correction. True APO lens were made long before FPL53 was developed. The design of the lens and the mating elements are much more important.

Which leads me to my next point...the image you see is entirely formed at the objective. Pretty much any aberation seen such as CA, field curvature, astigmatism, distortion, etc. is due to the objective. The function of barlows, teleconverters, and eyepieces is simply to maginify the all-ready formed image. If made correctly, they should take away nothing from the on-axis image quality. Barlows and teleconverters are especially easy to make because of their simple 2-3 element design. However, the main issue with in-expensive barlows is poor baffling leading to glare and scatter, which you have discovered. Complicated eyepieces, can also add aberations to the image, but these are mainly off axis. But unless you are using a full-frame camera, these aberations will generally be outside the sensor.

Now all this said, in order to properly evaluate these telescope lenses/systems you will need to push the optics to limits of distance/magnification that are well outside the normal parameters used in most digiscoping situations. Like I said in another post, the resolution of your camera on axis will "give up" before the telescope probably will. Only the the latest 12mp and larger DSLRS will start to outresolve the typical telescope lens.

Finally, why I guess it could be interesting to experiment with different gear combos there is really nothing new to what you are doing. Tele Vue designed their Powermates years ago specifically for long focal length imaging. Simply unscrew the barrel and attach a T-mount. I myself have used the 2.5x and 5x Powermates on a 100mm Pentax F4 SDUF II Petzval telescope. The image quality is excellent, they are fast and simple to swap out, and you are not adding long extentions making for difficult-to-balance mounting.

Hope this helps,
Rick

Interesting and valuable comments Rick.

I agree that Paul has not invented prime focus digiscoping. However, before his experiments, most considered a DSLR as a poor choice for digiscoping. Paul has demonstrated that it is an efficient and low cost way for long range digiscoping.

I didn't know much about Powermates and was under the impression that they were Tele Vue's name for barlows... Was I wrong ! Thanks for the info. There is some good info about them on the Tele Vue site and I'll be reading more about them. A 4X Powermate would be an interesting replacement for my stack of 2 TCs (2X and 1.4X) with more magnification.

 

[JGobeil]

Jules, we have basically the same equipment, i.e., Canon 20D and Kenko automatic extension tube set, although currently I am digiscoping with a newly acquired Canon 590IS P&S and Kowa scope. I am less-than-satisfied with the focusing on the camera's LCD due to its low resolution and long setup time.

Since the 20D has bayonet mount, as well as the Kenko tubes, what mounting ring would I need that would connect the camera/extension tube assembly to the Kowa scope eyepiece end which is threaded? and where can I get such a ring? The way I see it, this ring would have to have threads on one end and a bayonet mount on the other. Also, do you need a long track support to take up all the weight of camera and assembly off the scope eyepiece connection?

Dennis

Dennis,

I also don't like P&S cameras for digiscoping. Focusing on the LCD is slow, like you pointed out. It is also difficult under strong light and far from efficient when you are wearing glasses.

IMO, the easiest way to connect a DSLR to a spotting scope is to use the camera side of a T mount and connect it to a threaded eyepiece via a stepping ring.

For example, the Pentax WX eyepieces have a 43mm thread and the bayonet side of a T mount has a 47mm thread (I'm not sure of that - please check). Using a 47-43mm step down ring connects the 2 solidly and cheaply.

Like Rick points out, you can also use specialized mounts but these are usually more expensive. You can get the T-mount for your camera and stepping rings on eBAY for not much money.

Regards
Jules