Paul,
It's time to take your setup down to the local ponds/park/wetlands to test it out in a real world environment. I'm looking forward to seeing the results.
Neil.
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Some digiscoping experiments with a dslr (1 Viewer)
- Thread starter Paul Corfield
- Start date
Paul,
It's time to take your setup down to the local ponds/park/wetlands to test it out in a real world environment. I'm looking forward to seeing the results.
Neil.
Paul Corfield
Well-known member
I'm having a week off mid August and staying in a farm cottage with my family so I'll be getting plenty of photo opportunities then as we will be surrounded by countryside. Also hoping to get out and about this weekend and definitely next week to some local spots. After testing today I know the set up is going to perform well but it will be interesting to see just how well.
Jules - I don't think it matters about the spacer. A lot of 3X teleconverters are just 2X ones that have longer bodies which in effect is just like using a spacer.
Paul.
Paul Corfield
Well-known member
The way I've tested and found to be pretty accurate is to visually measure the magnification differences between two photos taken at the same place with one of those photos being at a known focal length -
(1) Take 2 photos from the same place, one at the scopes native focal length (photo1) and one with the barlow/teleconverter combination (Photo2).
(2) In Photoshop I resize both images to say 800 pixels wide just to make them easier to work with.
(3) Then I increase Photo1 by a given percentage, whatever is a best guess to make the subject in the photo the same size as the subject in Photo2.
(4) Then I drag Photo1 over the top of Photo2. In the layers channel I apply some transparency to Photo1 and then you can see how well it lines up to Photo2 underneath.
(5) If they don't line up right first time then delete all the stages in the history palette to get you back to stage (2) and then repeat the process again, just refining the percentage until you get a perfect match.
Photo1 is a known focal length, in my case it's 600mm. If I need to increase Photo1 by 400% to get a perfect match then I know it's 4 times bigger or in theory I would need a telescope that was 4 times longer to produce the same amount of magnification. 4x600mm=2400mm
Another way to look at it would be that a 600mm lens is 12X magnification so at a 400% increase we would get 48X
Paul.
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vkalia
Robin stroker
Hi guys, sorry I have been away but I've been following this thread as well as the test results. I have been trying to finalize my order for the Televue but the good folks at Anacortes seem to have stopped replying to emails (well, mine anyway), so it may be time to either give them a call or find another vendor.
Anyway, I wanted to ask something while I put together all the bits and bobs: I am planning on getting the 1.25" Prime Focus T-adapter from CNCSupply, which is supposed to fit into the eyepiece port.
Am I correct in assuming that if I want to use a barlow, I simply insert the barlow into the telescope's eyepiece port and then the same T-adapter attaches to the barlow? It would make sense, but I just wanted to check anyway.
Thanks,
Vandit
Anyway, I wanted to ask something while I put together all the bits and bobs: I am planning on getting the 1.25" Prime Focus T-adapter from CNCSupply, which is supposed to fit into the eyepiece port.
Am I correct in assuming that if I want to use a barlow, I simply insert the barlow into the telescope's eyepiece port and then the same T-adapter attaches to the barlow? It would make sense, but I just wanted to check anyway.
Thanks,
Vandit
Paul Corfield
Well-known member
Personally I would think it better to buy everything in 2" fitting rather than 1.25". I started out with all 1.25" but soon upgraded to all 2". Most scopes these days allow you to use both 1.25" and 2" fittings, just check before you buy but the Televue TV-85 will take 2" fittings.
Between the T-mount and the scope you will also need some sort of extension tube to allow you to reach focus. The best size to get is the 50mm and a 35mm lengths. See here for some examples on ebay.
If you get 2" fittings then get the 2" GSO ED 2X barlow and the lens cell will screw into the CNC T-mount. This then goes into the scope extension tube and the extension tube goes into the scope eyepiece port.
Paul.
vkalia
Robin stroker
Thanks for the info, Paul. I've decided to get the 2" T-adapter sold by Optcorp.
One question about the above and how this stuff is sequenced. If I am reading the websites correctly, the sequence is like this:
Camera -> T-ring -> 2" T-adapter -> Barlow -> 2" Ext tube -> Scope
Is that correct?
I wonder if I can also use my regular camera extension tubes in the following sequence:
Camera -> Canon ext tube -> T-ring -> 2" T-adapter -> Barlow -> Scope
To add to the complications, there is also a third method, using T-2 extension tubes, which I assume goes as follows:
Camera -> T-ring -> T-2 ext rings -> 2" T-adapter -> Barlow -> Scope
Any preferences with one over the other? I would assume that spacers are just spacers, but the larger diameter of the Canon extension tube or the 2" extension tubes would be preferable.
Regards,
Vandit
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Paul Corfield
Well-known member
Yes, I think all those combinations will work. All you can do is try all sorts of combinations when you get the scope. It's only small percentages between which one is better than the other, just depends on the quality of the optics.
Regarding the spacers, depending on where you put them they will add quite a bit to the magnification. This is because the light rays leaving the barlow or the teleconverter are leaving at an angle. If you put the spacer between the camera and the barlow or teleconverter then the image has further to travel and therefore increased in size by the time it hits the camera ccd.
Whatever T-adapter you get, make sure it is threaded for standard 2" filters and then this will also allow you to screw in the 2" barlow lens cell if at some point you buy one of those as well.
EDIT - regarding your combinations. You will always need some sort of extension tube going into the scope no matter what combination of lenses you use. This has to be like this because all scopes don't have enough back travel to reach focus when doing prime focus style photography.
Paul.
Regarding the spacers, depending on where you put them they will add quite a bit to the magnification. This is because the light rays leaving the barlow or the teleconverter are leaving at an angle. If you put the spacer between the camera and the barlow or teleconverter then the image has further to travel and therefore increased in size by the time it hits the camera ccd.
Whatever T-adapter you get, make sure it is threaded for standard 2" filters and then this will also allow you to screw in the 2" barlow lens cell if at some point you buy one of those as well.
EDIT - regarding your combinations. You will always need some sort of extension tube going into the scope no matter what combination of lenses you use. This has to be like this because all scopes don't have enough back travel to reach focus when doing prime focus style photography.
Paul.
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Paul Corfield
Well-known member
The reason it's not a simple mathematical calculation is because I also have a 60mm macro tube between the camera and the 1.4X teleconverter which increases the magnification of the teleconverter through optical projection. Also the lens cell of the barlow is screwed into the 2" scope adapter so the distance from this to the teleconverter also has to be considered as its magnification will be different than the 2X that would be provided if the lens cell was screwed into the barlow. In the end I think my way of working it out is fairly quick. I use Photoshop a lot so in reality it's only a couple of minutes.
Paul.
Derry
Well-known member
Ernie, Paul's method is an easy way of calculating for a close mm (FL) length,,
telescopes FL is established at infinity with a set distance to the eyepiece,, when you start adding various length extension tubes and mounting barlows mid way in the path the math to figure real FL can get wild,, certainly way beyond what I can pull back to memory,, |=)|
Derry
telescopes FL is established at infinity with a set distance to the eyepiece,, when you start adding various length extension tubes and mounting barlows mid way in the path the math to figure real FL can get wild,, certainly way beyond what I can pull back to memory,, |=)|
Derry
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erniehatt
Well-known member
Thanks Paul and Derry, for the very clear explanation, I will give it a try. Ernie
Hello
I'm new to the forum and have just bought my self a celestron c5 spotter(5inch Schmidt-Cassegrain).
I use it on my pentax k20d and a berlebach tripod with a gitzo video head.
I have only properly tested it with the pentax connected straight on the scope with the t-adapter and t ring.(no optics between)
It could also connect trough the eyepice but i thought it gave a worse result so havent done more testing.
My first opinion is that it's not all that sharp but it could be me needing more practise.
It gives a very shalow dof at close ranges so if you are in a hurry you need a bit luck to get focus. and the focus knob i slow to use but it's very precise
in god dayligt i get shutterspeeds like 1/90s at iso 100 (picture below)
Anyone know if i could get better result using either a eyepice or/and a lens to connect to the spotter?
i have a 40mm lens and a 100macro lens, both with good quality. Could i use them for anything good?
Celestron have this reduser/corrector which convert the c5 f10 1250mm(connected straight on to the camera) to a f6.3 and ?mm
Anyone know what focal range it gives. And would it do miracles to my photos?
picture under is what i manage to do. I have taken it trough Photoshop and sharpend it. Can i espect more?
(i reposted the post in this tread when i found it.)
I'm new to the forum and have just bought my self a celestron c5 spotter(5inch Schmidt-Cassegrain).
I use it on my pentax k20d and a berlebach tripod with a gitzo video head.
I have only properly tested it with the pentax connected straight on the scope with the t-adapter and t ring.(no optics between)
It could also connect trough the eyepice but i thought it gave a worse result so havent done more testing.
My first opinion is that it's not all that sharp but it could be me needing more practise.
It gives a very shalow dof at close ranges so if you are in a hurry you need a bit luck to get focus. and the focus knob i slow to use but it's very precise
in god dayligt i get shutterspeeds like 1/90s at iso 100 (picture below)
Anyone know if i could get better result using either a eyepice or/and a lens to connect to the spotter?
i have a 40mm lens and a 100macro lens, both with good quality. Could i use them for anything good?
Celestron have this reduser/corrector which convert the c5 f10 1250mm(connected straight on to the camera) to a f6.3 and ?mm
Anyone know what focal range it gives. And would it do miracles to my photos?
picture under is what i manage to do. I have taken it trough Photoshop and sharpend it. Can i espect more?
(i reposted the post in this tread when i found it.)
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Paul Corfield
Well-known member
The photo isn't too bad. A faster shutter would possible result in a sharper image.
Using an eyepiece and a lens will give slower shutter speeds most likely. It does on any set up I've tried in the past due to all that extra glass. You could use a low power eyepiece which would have a similar effect as a focal reducer in that the magnification would be reduced resulting in brighter images. I always think that to get the best quality image you need the least amount of glass possible between the image and the camera ccd. Using an eyepiece and a lens usually creates more problems than it solves.
I think the f6.3 reducer would make it around 800mm. F ratio is the focal length multiplied by the aperture size. So 1250mm divided by 127mm = F10
f6.3 would mean 127mm x 6.3 = 800mm
Don't how much that would improve depth of field but it would give a much brighter image which gives faster shutter speeds. Downside is you lose quite a bit of magnification. Wouldn't like to say what the quality of the end photo would be like, it could go either way.
Paul.
Using an eyepiece and a lens will give slower shutter speeds most likely. It does on any set up I've tried in the past due to all that extra glass. You could use a low power eyepiece which would have a similar effect as a focal reducer in that the magnification would be reduced resulting in brighter images. I always think that to get the best quality image you need the least amount of glass possible between the image and the camera ccd. Using an eyepiece and a lens usually creates more problems than it solves.
I think the f6.3 reducer would make it around 800mm. F ratio is the focal length multiplied by the aperture size. So 1250mm divided by 127mm = F10
f6.3 would mean 127mm x 6.3 = 800mm
Don't how much that would improve depth of field but it would give a much brighter image which gives faster shutter speeds. Downside is you lose quite a bit of magnification. Wouldn't like to say what the quality of the end photo would be like, it could go either way.
Paul.
Thank's
i think the reduser is designed to flatten the image. I found out reading the net that the reflector type scopes gives a little curved images. With a small DOF and a subject covering the image woulden't that make it hard to get the whole subject in focus.
will it be possible to increse the magnification when using the reduser by adding macro rings or something simular?
Another benifit of the reduser is that you seal the back end of the scope. Maybe i have to try it one day. Not now, because my budget i's blown straight to the moon
i think the reduser is designed to flatten the image. I found out reading the net that the reflector type scopes gives a little curved images. With a small DOF and a subject covering the image woulden't that make it hard to get the whole subject in focus.
will it be possible to increse the magnification when using the reduser by adding macro rings or something simular?
Another benifit of the reduser is that you seal the back end of the scope. Maybe i have to try it one day. Not now, because my budget i's blown straight to the moon
Paul Corfield
Well-known member
I think focal reducers have to be kept to a very specific distance from the camera cdd for them to work correctly and to provide the flat field of view. For that reason it probably wouldn't be possible to alter the magnification with spacers as the image quality would likely suffer.
Paul.
Paul.
You have enough light with your setup , you just didn't use enough iso . One of the main reasons people switched to using a DSLR on a scope was to get higher shutter speeds using the higher iso/lower noise capability. The Canon guys have been using iso 800/1600 for some time. With the high magnifications that we get with digiscoping and subject movement you always choose high shutter speed over lower noise. With my Olympus I'm using iso 400 as default and my Nikon iso 800. I go to 800 and 1600 respectively when necessary. Only occasionally do I drop lower when digiscoping night herons or other cooperative birds.
Your image is not too bad for your first effort and if you had dropped the exposure down 1 stop to hold more detail in the feathers you would have been happier.
Go out and shoot some more at iso 400 and you'll be pleasantly surprised.
Good luck, Neil.
Derry
Well-known member
Phaser, nice photo for the first time out,, agree with the others on the higher shutter speed and ISO but do some peeping when your shooting and if the highlights are blown out start dropping the ev,, silght under exposure is far better than one with blown highlights,, you can save the underexposed in PP,, your scope and camera are certainly able to produce some outstanding photos,,
I have the TV85 as well as a Questar 3.5,, shooting through the Questar is more difficult than my TV85,, the Q needs an extremely steady mount as I find it is far more subject to any vibration than shooting through the TV85,, the Q is less mass and even the small amount of shutter actuation can induce some movement with the mirror locked up for 5 seconds before the shot,, I'm working on a different mount arrangement for the tripod to offer more mass to the scope,, have not weigh a C5 but you may be experiencing the same issues not allowing those crystal clear photos,,
here is a post of my current Q arrangement,, when I have the new one made I'll post a photo,,
Derry
I have the TV85 as well as a Questar 3.5,, shooting through the Questar is more difficult than my TV85,, the Q needs an extremely steady mount as I find it is far more subject to any vibration than shooting through the TV85,, the Q is less mass and even the small amount of shutter actuation can induce some movement with the mirror locked up for 5 seconds before the shot,, I'm working on a different mount arrangement for the tripod to offer more mass to the scope,, have not weigh a C5 but you may be experiencing the same issues not allowing those crystal clear photos,,
here is a post of my current Q arrangement,, when I have the new one made I'll post a photo,,
Derry
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