Prime focus seems quite simple, but I'm confused about magnification. Normally it is calculated by telescope length / eyepiece length. If you remove the eyepiece and go directly to the sensor, what is the magnification?
Prime focus is very simple indeed. In Astrophotography there is no such thing as magnification. In visual you say "magnification" but mean the comparison between the achieved field of view (FOV) of your setup and your normal human FOV. On a sensor this comparison is hard/ senseless so we just use FOV in degrees to describe our setup. The moon has roughly 1° diameter and that is roughly the FOV of me scope on prime focus. Changing the sensor size or the focal length will alter the FOV and you can use online calculators to see what FOV your combination of setup will produce and compare it with the angular size of your objects you want to image. Clear skies and have fun!!
@@Lord_VolknerLOL - no comparison. From trying to capture moons on Jupiter in 2022 to improving the crispness of horse head nebula images in 2023. A few upgrades in between. Thanks for asking!
I wish I could 👍this video multiple times. I've watched dozens, perhaps more than a hundred videos on the subject of astrophotography and this is the first that actually shows how to attach a camera to the telescope. Thank You!!
Thank You you covered it as of today I have all the accessories you covered in the video. Just waiting for clear skies..thank you showing us new guys these options..
Then it's technical not a newton anymore :-D But: Many modern observatory scopes (like big 5m NASA scopes) have the camera / sensors in the main focal point because: Whats the point of using additional optical components. Real bomber: In earls days you could STEP INTO the literal focal point and SEE the stars yourself: cool, he?
@@catchingphotons Makes so much sense : satellite dishes have the receiver in that spot aswell. Newtonians , Maks , SCT's are simply just a work-around to make long FL possible in smaller telescope. Standing in the Focal Plane of a 5m reflector added to my Bucket List ☺
Great video the most comprehensive explanation I’ve seen, now I understand, thank you I just love these videos, I’m working my way through them all. Please keep them coming, a real must for beginners and the experienced.
I love these videos they are so easy to understand, I’m slowly working my way through them all, a real must for both the novice and experienced. Keep up the good work.
To more experienced astrophotographer - I'm still getting my basics down and using fairly inexpensive equipment and am trying to figure out how I can solve a focus problem I'm having with my Astromaster EQ130 and my Canon EOS4000D - I've been able to attach the camera for Prime focus and got the EQ mount balanced and everything, but I'm finding I can't get the sensor close enough to the secondary mirror to get the best focus. I presume it's because the telescope just isn't designed for this use, but was curious if there was a corrective lens to help or if I'm better off saving my money for a higher end telescope.
the video is done well but, at minute 1:55 the formula for the equivalent focal length is a distance from the Posterior Principal Plane, and not the distance from the first lens! the distance represented in the video appears to be: f_L2 (m + 1) + f_L3, where "m" is the magnification of the telescope. Your opinion on it would be interesting! Thank you
It's the Planetarian range you pull the rubber shroud off and there is a thread u need a baarder thread adaptor to fit T2 I think they are the only company that have this feature I been using it for 7 years on a refractor just got a PDS 150 Skywatch er I have tried it on a land object so not seen the moon yet sinse I got it 2 weeks ago
I want to ask, can i use a mirrorless like fujifilm XT1 and SvBony MK105 to take prime focus photo with 3x barlow to take a good planetary photo? I mean clear and decently detailed? The astronomy tools website shows it'll be small, but i think i can crop the video using PIPP. I'm used to take afocal photo usign my phone, but it's still not that clear, it's still presentable tho. Clear skies!
Planetary all comes down to A) ... good seeing conditions and that's just luck, nothing you can do on this front but being persistent. B) ... A good optics and optical resolution. This is why you need at least a medium quality Barlow lens and.... Aperture helps :-) C) frame rate! This is the reason why planetary cameras are basically webcams. You don't need bomber resolution because going with full frame will only result in 95% crop and an overwhelming amount of data. What you need is something like 60fps go capture JUST the right frames during your 60 seconds caption round. That's really key. So: theoretically yes if your camera can record something like 60,80,120fps at something like raw data :-) Just remember: you don't want to capture one single frame but thousands and thousands and let Autostakkert or similar programs fetch the best ones.
Thanks for the video! This will help me pace myself and focus on learning before spending! That said, do you think it is possible to reach prime focus using a focal reduction lenses? DSLR camera sensor is still too far from secondary mirror and was wondering if a focus reducer lenses could help reduce that distance. Thanks!
Thanks for your encouraging words! It's the other way around: If the DSLR sensor is too far away (from focal point not from secondary) than you need the focal length of your scope to be longer than before. Thereby you'd need a Barlow lens. Other option: shorten the tubus aka distance prime/secondary with a saw. Than the focal point moves out of your scope as well. Clear skies!!
Great vid! Got a question. When u do prime focus with a dslr, with a T2 adapter to a 1.25" eyepiece holder, considering the sensor of the camera is larger than the T2 adapter, won't there be a circle as seen in 0:43?
If the light path gets obstructed in any way there will be vignetting on your image. If the sensor is big enough and the adapter small enough there will be "circles" for sure. Even without direct obstructions light intensity drops at the edges due to imperfections. Such things need to be accounted for using "flat frames" after imaging. Please be aware that it's not the total diameter of adapter and sensor that counts but if/if not the conical light path is obstructed during the path though your optical system. Using normal T2 adapters and normal cameras (even full frame) won't trouble you though. Clear skies!!
Very interesting! Would it make sense to use the eyepiece projection method to shrink down the secondary mirror? You could place the secondary in the focal point and make the obstruction roughly as small as the sensor of your camera, right? Wouldn't that be perfect for very small sensors and rather dim objects?
I don't think you need the eyepiece projection to use your method. You can always move mirror-parts to achieve certain things. But if you move the secondary back you will also increase the tube length with all the troubles that come with that (instability, wind vulnerability). I think there must be a sweet spot of tube length/mirror size. Clear skies!!
I have read that in the case of eye piece projection also the distance between the sensor and eyepiece increases the magnification. How does that work?
Around 6:37 I talk about the focal projection method. Base line: alter the distance eyepiece and sensor and you need to adjust the distance eyepiece and main lens to still get focus on the sensor. Thereby you differ the entire magnification of the system. Cheers!
@@catchingphotons Do you know if there is a limit to the amount of focal lenght which can be achived by eyepiece projection? I took pictures of the moon which fitted the whole frame with a 25mm eyepiece and 650mm telescope. When adjusted the focus er on the telescope the moon never really reached complete focus. Do you know why?
Thanks Chair! When I detach the DSLR lens you can only see the mirror for the optical finder. The sensor is hidden behind the mirror BUT when imaging the mirror will flip back and expose the sensor to the light of the stars. So it's possible that small dust particles will settle on the sensor. Same is true for dedicated astro cameras without any protecting mirrors. So as time goes by you will find more and more dust particles on your sensor. That is even more true when using an "open" system like the Newtonians. Refractor telescopes shield the sensor from incoming light. Newtonians don't. But luckily there is a row of good tricks: 1) Blow the dust away with dry and compressed air (not your breath!). 2) Use light-frames to subtract the dust particles from your final image. Light frames are taken at daylight and contain any errors in your light path. With them you can get rid of nearly any dust errors. Hope this covers your question! Clear skies to you my friend! -Chris
@@catchingphotons Yeah that covers it thanks. That's bad news for newtonians. Dry air sounds ok but I'm surprised there are no special protectors for that purpose. I guess filters do that indirectly but you might not be using one.
Thanks for the overview. I have a Sony A7iii full frame camera and got a very small image of Jupiter using a 2x Barlow and the "prime" method. Is it worth going for a 5x televue powermate for planetary imaging or will I just be magnifying abberations? I have a 254mm f/5 dobsonian.
With 1200mm and 2x Barlow you can expect some decent planets. Don't buy another Barlow but a dedicated planetary cameras. I recommend trying the "ZWO ASI120 MCS -Colour" - it's cheap (150 bucks??) and you'll get good first results. Trick is: planets are small! So you need just a small sensor. But seeing is everything so you will need a high frame rate (small and fast). A DSLR is de facto the opposite. Large and slow. Taking thousands of frames you than stack them in Autostakker3! to extract the best images and stack those. I did a video about that difference: th-cam.com/video/RvLl936NG5U/w-d-xo.html Clear skies!!
@@catchingphotons Thanks for the reply. The camera I'm using is a mirrorless which has some of the drawbacks of DSLRs (big sensor full-frame sensor isn't necessary here) but I wouldn't characterise it as slow- framerates of 120fps at 1080p at 100Mb/s and no binning I think are decent specs. How would a planetary camera compare?
@@ishanr8697 Ah, interesting. Few things: A) can you record in something like a raw video format? Even though you should be able to achieve results without - the planetary webcams in combination with SharpCap do store the video data uncompressed in order not to loose any data. B) Your resolution will make processing the data a pain because of the huge sensor size. Planetary webcams tend to have a small sensor because you are only interested in the "core" parts. C) The pixel-size of your DSLR is relatively large (6um) and you want to have a finer angular resolution for planets. My ASI has 3.5um I belive. D) Normal dedicated astro webcams can be interfaced with dedicated astro-software. SharpCap is your first choice here. E) The frame-rate of yours sounds cool!! My ASI "only" gets up to 60fps and that't totally fine for me. F) Do you have any results to show us? I would be highly interested in what is doable with a DSLR! Very much appreciated. Clear skies!! -Chris
@@catchingphotons I'm afraid I went ahead and got the 5x Powermate before your original reply so I guess we'll find out :) I plan to observe Saturn and Jupiter tonight and will get back to you with results. Ultimately, I may need a smaller sensor/dedicated cam but this might work just fine? I am a complete beginner in astro but I have some basic knowledge of photography, optics and physics which, along with your guides, I hope will see me through my second capture. Wish me luck!
@@ishanr8697 I do wish you the best and I am eager to see the results! Don't forget to post it - you can link me @ twitter or insta, than I will get alerted. In the end: the sensor size is "just" a matter of processing time. If every other criteria is met, the sensor size doesn't matter. It is wasted though, but so what. Clear skies!
I tried prime focusing the other night and with zero results. I got no where close to being able to focus the camera. The camera had the t-ring combined with the piece to slide into the 2” focuser. I wasn’t sure what setting I should have set on the camera, iso, white balance, manual, live or auto focus. So many variables. Oh, and I did try my cell phone but when I got close to getting the moon in the camera, then all of a sudden it was no where to be seen. I was wondering if the phone automatically switched to a different lense.
Hey! Focus and all that stuff needs some practice and such. Try the moon first - this is a very easy target for all cameras. For your prime-focus camera: Focus on something bright (moon) - set the ISO to the lowest and the exposure to get the best brightens. This works for the moon. For DSO (but this needs another level of dedication anyway): the highest exposure you can get out of your mount and then rise the ISO until your image is bright enough. I doubt it that your phone switches lenses (although who knows). Have you accidentally shaken the tripod? Cheers and clear skies! -Chris
Isnt the eyepiece projection method the ideal one for begginer astrophotography? i have an 8 inch dob which clearly isnt suited for that but cant i using the eyepiece projection method and with lots of short exposures have descent results with dso's?
Hey! For beginners the afocal projection is best suited. There a simple smartphone in front of an eyepiece can give you cool first results even on DSOs. See my latest video about smartphone photography. Eyepiece-projection onto the bare sensor can be used but since you need a naked sensor and adapters you can as well use a t-ring adapter and hop into prime focus This will give you better results because of the reduced numbers of lenses. With an 8" dob of say 1200FL and a DSLR you could try ultra short but high (!!) ISO snaps of DSOs and stack them. Though the short sub-exposure time will limit you. See my video about stacking for more info! Anyway: clear skies!!!
@@catchingphotons Thank you for the quick and helpful reply, I appreciate it! My concern is if I will be able to achieve the desirable zoom for DSOs with just using the t-ring and achieving prime focus. You definately earned a sub!
Thanks a lot!! Main thing about DSO: the objects are gigantic but faint. So high magnification is mainly not adviced. Example: with my native 750mm FL using a Canon 700D at prime focus the Orion Nebula just barely fits the FOV, North America nebula is WAY too big and Andromeda is cut in half. For this I'd need something like 450mm FL or in other words a 0.5x reducer. So: shorter is often better for DSO. Totally the opposite direction for planetary though. So if you don't have a Barlow lens and want to image you might use eyepieces projection. Clear skies!!
With the afocal method - one can control magnification - and thus have more options for different types of targets, even though the captured images do not have the same quality as prime focus. With prime focus, magnification is fixed and is typically very high. Often times in the order of 130x This degree of magnification makes it extremely difficult to center on an object. With prime focus it is almost impossible to center an object using simple visual object finder devices such as a 9x50 scope, red-dot or Telrad finder. Prime focus really requires precise computerized goto mount. And in most cases - people use plate solving to accurately center on objects. So a significant difference between afocal and prime-focus - is that prime-focus typically requires a significant personal investment in learning complex softwares, and the use of higher priced equipment. But people often get spoiled by what they are able to see with Prime focus! :-D
Thanks for your input DW. Personally I wouldn't agree with the statement of prime focus magnification. This really depends too much on your focal length (300mm refractor Vs 5000mm SCT) and your sensor (planetary camera Vs full frame sensor). So there is no given magnification. You are right that the field of view can't be changed and hence you are limited to a certain set of objects. But on three other hand image quality is on another level. Finding objects mainly depends on that object. Deep sky objects are normally very dim but no matter the projection method. Clear skies!!
That totally depends on you imaging sensor. The two factors must be calculated together. Download "Stellarium" for PC and enter your FL and your sensor data. Stellarium shows you the field of view. Very helpful. Clear skies!!
Do you know if there is a limit to the amount of focal lenght which can be achived by eyepiece projection? I took pictures of the moon which fitted the whole frame with a 25mm eyepiece and 650mm telescope. When adjusted the focus er on the telescope the moon never really reached complete focus. Do you know why?
Normally there shouldn't be a limit to focal length. For every given focal length there is a pair of distances (main lens eyepiece | eyepiece sensor). It might (!) be that your focus drawer can't reach (eyepiece sensor) distance but I've never heard of that. What do you mean with: not in focus? Can you defocus in both directions or is the moon just blurry by itself? Second reason might just be bad seeing. I'm looking forward to hearing from you. Clear skies!!
dear Chris, thank you for the video. can you help me clarify my problem. I use the Starsense 102mm refractor telescope, focal length is 660mm, camera i used is DSLR Canon EOS T3i, APS-C sensors, I can use prime focus for taking picture of the moon with extend tube (the tube same with tube in your video) but I can not use eyepiece projection method (i used 25mm eyepiece) i can not see any thing in my camera live view. what is wrong with my system.
dear Chris, sorry for late reply. i have found solution for my problem, it is because i removed the diagonal mirror btw telescope and eyepiece. last night i tried again with diagonal mirror then i can get focus for both eyepiece and barlow lens 2x. thank you again for your suggestion.
If you scope has 1 1/4" eyepieces than you need a t-ring adapter for the canon and a t-2 to 1 1/4" adapter for attaching the camera to the eyepiece holder. Please don't expect miracles from this scope. My advice: Rather than plug the canon to the scope invest into a proper smartphone holder and take snaps or videos of planets and the moon with your phone though the eyepieces. I think this might be a good first entrance into this field! Attaching the Canon will increase weight too much and probably destabilise the mount. Clear skies!!
That's normally true. If you buy a Newton scope you need to be aware wether it's made for Astrophotography or not. The photography-Newtons are shorter - so focal point lays further outside of the focuser. Downside: you have to use simple adapters to use eyepieces but that's not too bad. Clear skies!!
I have attached my camera with a barlow lens 2,25x to my telescope (130, 900mm) How do I know how zoomed in I am? Am I only going to be able to take planet photos? I've only used eyepiece projection before but I was never able to pick up anything from things other than planets. Will this "new" way just give me similar results? I wanted to have nothing but the barlow is the only way I can get it to attach.
Hey Adolphus, 900mmFL and 2x Barlow equals 1800mmFL and that is quite long!! So as a result the field of view is rather small. What is the sensor size of your camera? You can download Stellarium and enter your specs to see what the resulting field of view is. I have a tutorial for Stellarium, check it out. Tltr: 1800mm FL is best used for tiny galaxies (super high precision tracking and super solid= expensive mount required) or for planetary (no high end mount necessary). Clear skies!!
I took a look in stellarium, I can see my field of view is way too small for large galaxies and nebulae. Finally I got an understanding of the scale, always was something I felt I missed
Great that you looked Stellarium up! Having an idea if scale is super important! You knew that Andromeda is 4-5x the full moon??? It blew my mind when I read that :-D Clear skies!!
As said in the video: not every scope is built for photographic usage. Hence the rather long focal length of the eyepiece needs to intercept the focal point of the scope, the focus wheel can't be inserted enough to make prime focus possible. There is nearly no way around: A) use a Barlow lens BUT this will highly alter your field of view... Not best choice. B) flex the tube shorter.... If you dare. C) Use this scope for planetary anyway because this is what you can use your score for and just take an eyepiece and clip your phone in front. See my video about smartphone photography on my channel for more information. This is the method I'd choose. Cheers and clear skies!
This is a image stack of Saturn I used with an ED wide angle 15mm eyepiece and a DSLR. puu.sh/Jg0MV/e395b8d48b.png You're correct about eyepiece enhanced imaging. The eyepieces have to be of high quality or the image will indeed suffer.
Your image looks great! The quality of the optical light path is of great importance. Even with prime focus with additional Barlow you'll notice the quality of the Barlow right away (achromat Vs Apochromatic). Thanks for sharing your result! Cheers!
Hi, When i try to use eyepiece projection with my Canon T5i , and a 10mm super plossl the image is always completely dark, EXCEPT for the moon. Everything else is complete darkness. Any idea on what is wrong? thank you
Prime focus seems quite simple, but I'm confused about magnification. Normally it is calculated by telescope length / eyepiece length. If you remove the eyepiece and go directly to the sensor, what is the magnification?
Prime focus is very simple indeed. In Astrophotography there is no such thing as magnification.
In visual you say "magnification" but mean the comparison between the achieved field of view (FOV) of your setup and your normal human FOV.
On a sensor this comparison is hard/ senseless so we just use FOV in degrees to describe our setup. The moon has roughly 1° diameter and that is roughly the FOV of me scope on prime focus.
Changing the sensor size or the focal length will alter the FOV and you can use online calculators to see what FOV your combination of setup will produce and compare it with the angular size of your objects you want to image.
Clear skies and have fun!!
@@catchingphotons Thank you for clearing that up! Looking forward to making my first images.
@@ronmac1832 One year later, how are your images?
@@Lord_VolknerLOL - no comparison. From trying to capture moons on Jupiter in 2022 to improving the crispness of horse head nebula images in 2023. A few upgrades in between. Thanks for asking!
@@ronmac1832 Glad to hear it.
I've been toying with the idea of getting into the hobby myself.
I wish I could 👍this video multiple times. I've watched dozens, perhaps more than a hundred videos on the subject of astrophotography and this is the first that actually shows how to attach a camera to the telescope.
Thank You!!
Haha thank you so much! Glad I could be of any help! Cheers!
CONGRATULATIONS FOR 1k !!!!
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Waiting for 1 Million 👍🏼😁
Thanks for the encouraging comments! What a cool journey!
This video solves the problem that has troubled me for a long time about eyepiece projection. Thank you very much.
Glad I could be of any help! Cheers!
That was a clear, clean overall review. Thank you
You are very welcome!!! 🤗
Thank You you covered it as of today I have all the accessories you covered in the video. Just waiting for clear skies..thank you showing us new guys these options..
Cool! Have fun :-)
Thanks! Im just getting a Sky-watcher Explorer 130PDS and this helps a lot
You are very welcome!! Have a lot of fun with your new scope. It's such a cool hobby. Clear skies!
Un vídeo muy bueno y muy claro. Gracias!!!
You are very welcome!
Wow after 30 years in astronomy hobby I never heard of eye piece projection. Impressive knowledge 👏
Thanks for your encouraging words! It's a wide field and there is always new things to discover for everyone. This is why I love it so much.
Thanks for the useful tutorial ❤
You are very welcome!! Thanks for your comment!
Saw a Newtonian which did not have a secondary but instead a camera at the beginning of the tube. Now that's genius!
Then it's technical not a newton anymore :-D But: Many modern observatory scopes (like big 5m NASA scopes) have the camera / sensors in the main focal point because: Whats the point of using additional optical components.
Real bomber: In earls days you could STEP INTO the literal focal point and SEE the stars yourself: cool, he?
@@catchingphotons Makes so much sense : satellite dishes have the receiver in that spot aswell. Newtonians , Maks , SCT's are simply just a work-around to make long FL possible in smaller telescope. Standing in the Focal Plane of a 5m reflector added to my Bucket List ☺
Man I should've started with your channel!
Attach the camera to the scope - this is absolute physics gold!
Thanks a lot pioneer, means a lot!
Fantastic video, really easy to understand!
Thanks for your kind words!!
Very informative, with just the right amount of detail.
Thanks Andy!!
thanks Chris for the video
You are very welcome! Clear skies!!
Great video the most comprehensive explanation I’ve seen, now I understand, thank you I just love these videos, I’m working my way through them all. Please keep them coming, a real must for beginners and the experienced.
I'm really happy that my videos are of any help. Clear skies!!
I love these videos they are so easy to understand, I’m slowly working my way through them all, a real must for both the novice and experienced. Keep up the good work.
Thanks for your encouraging words 😉👍 clear skies!!
What an awesome video series. I’m just getting started in astrophotography and in astronomy in general. These videos have answered so many questions
Thank you very much for your encouraging words!! Clear skies!
thanks man this was the most helpful video i found about camera attaching!
Cool! Glad the video was of any help!! Clear skies!!
To more experienced astrophotographer - I'm still getting my basics down and using fairly inexpensive equipment and am trying to figure out how I can solve a focus problem I'm having with my Astromaster EQ130 and my Canon EOS4000D - I've been able to attach the camera for Prime focus and got the EQ mount balanced and everything, but I'm finding I can't get the sensor close enough to the secondary mirror to get the best focus. I presume it's because the telescope just isn't designed for this use, but was curious if there was a corrective lens to help or if I'm better off saving my money for a higher end telescope.
the video is done well
but, at minute 1:55 the formula for the equivalent focal length is a distance from the Posterior Principal Plane, and not the distance from the first lens!
the distance represented in the video appears to be:
f_L2 (m + 1) + f_L3,
where "m" is the magnification of the telescope.
Your opinion on it would be interesting! Thank you
Thanks for the refinement. Very much appreciated. Clear skies!!
I use a baarder eyepiece it has threads and screws straight into my T2 adaptor 8mm and 22mm with front lenses off
Uhhh that's a neat feature! Does it work well and if so can you provide us with some images? Clear skies!
It's the Planetarian range you pull the rubber shroud off and there is a thread u need a baarder thread adaptor to fit T2 I think they are the only company that have this feature I been using it for 7 years on a refractor just got a PDS 150 Skywatch er I have tried it on a land object so not seen the moon yet sinse I got it 2 weeks ago
Thank you for these excellent videos. Exactly what a newbie like me needs.
Thanks Dave, glad you liked it! Clear skies!
0:08 yea bro Hubble is my first scope 😎
Would be awesome, wouldn't it? ;-)
@@catchingphotons awesome? I would be speechless!
May I ask where did you get the arm to hold the digital camera? Thanks...
You may. I can't exactly remember but i would presume that it was the "big online shopping center".
@@catchingphotons thank you...
I want to ask, can i use a mirrorless like fujifilm XT1 and SvBony MK105 to take prime focus photo with 3x barlow to take a good planetary photo? I mean clear and decently detailed?
The astronomy tools website shows it'll be small, but i think i can crop the video using PIPP.
I'm used to take afocal photo usign my phone, but it's still not that clear, it's still presentable tho.
Clear skies!
Planetary all comes down to
A) ... good seeing conditions and that's just luck, nothing you can do on this front but being persistent.
B) ... A good optics and optical resolution. This is why you need at least a medium quality Barlow lens and.... Aperture helps :-)
C) frame rate! This is the reason why planetary cameras are basically webcams. You don't need bomber resolution because going with full frame will only result in 95% crop and an overwhelming amount of data. What you need is something like 60fps go capture JUST the right frames during your 60 seconds caption round. That's really key.
So: theoretically yes if your camera can record something like 60,80,120fps at something like raw data :-)
Just remember: you don't want to capture one single frame but thousands and thousands and let Autostakkert or similar programs fetch the best ones.
@catchingphotons thank you for the insights :D
Thanks for the video! This will help me pace myself and focus on learning before spending!
That said, do you think it is possible to reach prime focus using a focal reduction lenses? DSLR camera sensor is still too far from secondary mirror and was wondering if a focus reducer lenses could help reduce that distance. Thanks!
Thanks for your encouraging words!
It's the other way around:
If the DSLR sensor is too far away (from focal point not from secondary) than you need the focal length of your scope to be longer than before. Thereby you'd need a Barlow lens.
Other option: shorten the tubus aka distance prime/secondary with a saw. Than the focal point moves out of your scope as well.
Clear skies!!
Great vid! Got a question. When u do prime focus with a dslr, with a T2 adapter to a 1.25" eyepiece holder, considering the sensor of the camera is larger than the T2 adapter, won't there be a circle as seen in 0:43?
If the light path gets obstructed in any way there will be vignetting on your image. If the sensor is big enough and the adapter small enough there will be "circles" for sure. Even without direct obstructions light intensity drops at the edges due to imperfections. Such things need to be accounted for using "flat frames" after imaging.
Please be aware that it's not the total diameter of adapter and sensor that counts but if/if not the conical light path is obstructed during the path though your optical system.
Using normal T2 adapters and normal cameras (even full frame) won't trouble you though. Clear skies!!
@@catchingphotons thx for the info! Clear skies!
Hey man what is the name of the afocal adapter.I saw the celestron one but it’s way to expensive.any suggestions?
I used the >> Omegon Camera adapter 1.25"
Very interesting! Would it make sense to use the eyepiece projection method to shrink down the secondary mirror? You could place the secondary in the focal point and make the obstruction roughly as small as the sensor of your camera, right? Wouldn't that be perfect for very small sensors and rather dim objects?
I don't think you need the eyepiece projection to use your method. You can always move mirror-parts to achieve certain things. But if you move the secondary back you will also increase the tube length with all the troubles that come with that (instability, wind vulnerability). I think there must be a sweet spot of tube length/mirror size.
Clear skies!!
@@catchingphotons Thanks for the explanation! I'm a bit of a tinkerer so I'm always wondering, what I could try to build :-)
I have read that in the case of eye piece projection also the distance between the sensor and eyepiece increases the magnification. How does that work?
Around 6:37 I talk about the focal projection method. Base line: alter the distance eyepiece and sensor and you need to adjust the distance eyepiece and main lens to still get focus on the sensor.
Thereby you differ the entire magnification of the system. Cheers!
@@catchingphotons Thank you for the answers :)
@@catchingphotons Do you know if there is a limit to the amount of focal lenght which can be achived by eyepiece projection? I took pictures of the moon which fitted the whole frame with a 25mm eyepiece and 650mm telescope. When adjusted the focus er on the telescope the moon never really reached complete focus. Do you know why?
I have a canon 20d. How do i make sure my image is correctly focused without live view. Do I need to look at the viewfinder.
Does your 20d have a display at the back for live view? If so I might not fully understand your question. Cheers!!
@@catchingphotons No just a viewfinder
Great video as always! Does dust become a problem for dslr cameras? Seeing the sensor exposed like that makes me nervous.
Thanks Chair!
When I detach the DSLR lens you can only see the mirror for the optical finder. The sensor is hidden behind the mirror BUT when imaging the mirror will flip back and expose the sensor to the light of the stars. So it's possible that small dust particles will settle on the sensor. Same is true for dedicated astro cameras without any protecting mirrors. So as time goes by you will find more and more dust particles on your sensor. That is even more true when using an "open" system like the Newtonians. Refractor telescopes shield the sensor from incoming light. Newtonians don't. But luckily there is a row of good tricks:
1) Blow the dust away with dry and compressed air (not your breath!).
2) Use light-frames to subtract the dust particles from your final image. Light frames are taken at daylight and contain any errors in your light path. With them you can get rid of nearly any dust errors.
Hope this covers your question!
Clear skies to you my friend!
-Chris
@@catchingphotons Yeah that covers it thanks. That's bad news for newtonians. Dry air sounds ok but I'm surprised there are no special protectors for that purpose. I guess filters do that indirectly but you might not be using one.
Check my channel Lumix g85 eyepiece projection
Thanks for the overview. I have a Sony A7iii full frame camera and got a very small image of Jupiter using a 2x Barlow and the "prime" method. Is it worth going for a 5x televue powermate for planetary imaging or will I just be magnifying abberations?
I have a 254mm f/5 dobsonian.
With 1200mm and 2x Barlow you can expect some decent planets.
Don't buy another Barlow but a dedicated planetary cameras. I recommend trying the "ZWO ASI120 MCS -Colour" - it's cheap (150 bucks??) and you'll get good first results.
Trick is: planets are small! So you need just a small sensor. But seeing is everything so you will need a high frame rate (small and fast). A DSLR is de facto the opposite. Large and slow.
Taking thousands of frames you than stack them in Autostakker3! to extract the best images and stack those.
I did a video about that difference:
th-cam.com/video/RvLl936NG5U/w-d-xo.html
Clear skies!!
@@catchingphotons Thanks for the reply.
The camera I'm using is a mirrorless which has some of the drawbacks of DSLRs (big sensor full-frame sensor isn't necessary here) but I wouldn't characterise it as slow- framerates of 120fps at 1080p at 100Mb/s and no binning I think are decent specs. How would a planetary camera compare?
@@ishanr8697 Ah, interesting. Few things:
A) can you record in something like a raw video format? Even though you should be able to achieve results without - the planetary webcams in combination with SharpCap do store the video data uncompressed in order not to loose any data.
B) Your resolution will make processing the data a pain because of the huge sensor size. Planetary webcams tend to have a small sensor because you are only interested in the "core" parts.
C) The pixel-size of your DSLR is relatively large (6um) and you want to have a finer angular resolution for planets. My ASI has 3.5um I belive.
D) Normal dedicated astro webcams can be interfaced with dedicated astro-software. SharpCap is your first choice here.
E) The frame-rate of yours sounds cool!! My ASI "only" gets up to 60fps and that't totally fine for me.
F) Do you have any results to show us? I would be highly interested in what is doable with a DSLR! Very much appreciated.
Clear skies!! -Chris
@@catchingphotons I'm afraid I went ahead and got the 5x Powermate before your original reply so I guess we'll find out :) I plan to observe Saturn and Jupiter tonight and will get back to you with results. Ultimately, I may need a smaller sensor/dedicated cam but this might work just fine? I am a complete beginner in astro but I have some basic knowledge of photography, optics and physics which, along with your guides, I hope will see me through my second capture. Wish me luck!
@@ishanr8697 I do wish you the best and I am eager to see the results! Don't forget to post it - you can link me @ twitter or insta, than I will get alerted.
In the end: the sensor size is "just" a matter of processing time. If every other criteria is met, the sensor size doesn't matter. It is wasted though, but so what.
Clear skies!
I tried prime focusing the other night and with zero results. I got no where close to being able to focus the camera. The camera had the t-ring combined with the piece to slide into the 2” focuser. I wasn’t sure what setting I should have set on the camera, iso, white balance, manual, live or auto focus. So many variables.
Oh, and I did try my cell phone but when I got close to getting the moon in the camera, then all of a sudden it was no where to be seen. I was wondering if the phone automatically switched to a different lense.
Hey! Focus and all that stuff needs some practice and such. Try the moon first - this is a very easy target for all cameras.
For your prime-focus camera: Focus on something bright (moon) - set the ISO to the lowest and the exposure to get the best brightens. This works for the moon.
For DSO (but this needs another level of dedication anyway): the highest exposure you can get out of your mount and then rise the ISO until your image is bright enough.
I doubt it that your phone switches lenses (although who knows). Have you accidentally shaken the tripod?
Cheers and clear skies!
-Chris
Isnt the eyepiece projection method the ideal one for begginer astrophotography? i have an 8 inch dob which clearly isnt suited for that but cant i using the eyepiece projection method and with lots of short exposures have descent results with dso's?
Hey!
For beginners the afocal projection is best suited. There a simple smartphone in front of an eyepiece can give you cool first results even on DSOs. See my latest video about smartphone photography.
Eyepiece-projection onto the bare sensor can be used but since you need a naked sensor and adapters you can as well use a t-ring adapter and hop into prime focus
This will give you better results because of the reduced numbers of lenses.
With an 8" dob of say 1200FL and a DSLR you could try ultra short but high (!!) ISO snaps of DSOs and stack them. Though the short sub-exposure time will limit you. See my video about stacking for more info!
Anyway: clear skies!!!
@@catchingphotons Thank you for the quick and helpful reply, I appreciate it! My concern is if I will be able to achieve the desirable zoom for DSOs with just using the t-ring and achieving prime focus. You definately earned a sub!
Thanks a lot!!
Main thing about DSO: the objects are gigantic but faint. So high magnification is mainly not adviced.
Example: with my native 750mm FL using a Canon 700D at prime focus the Orion Nebula just barely fits the FOV, North America nebula is WAY too big and Andromeda is cut in half. For this I'd need something like 450mm FL or in other words a 0.5x reducer.
So: shorter is often better for DSO. Totally the opposite direction for planetary though. So if you don't have a Barlow lens and want to image you might use eyepieces projection.
Clear skies!!
With the afocal method - one can control magnification - and thus have more options for different types of targets, even though the captured images do not have the same quality as prime focus.
With prime focus, magnification is fixed and is typically very high. Often times in the order of 130x This degree of magnification makes it extremely difficult to center on an object.
With prime focus it is almost impossible to center an object using simple visual object finder devices such as a 9x50 scope, red-dot or Telrad finder. Prime focus really requires precise computerized goto mount. And in most cases - people use plate solving to accurately center on objects.
So a significant difference between afocal and prime-focus - is that prime-focus typically requires a significant personal investment in learning complex softwares, and the use of higher priced equipment.
But people often get spoiled by what they are able to see with Prime focus! :-D
Thanks for your input DW.
Personally I wouldn't agree with the statement of prime focus magnification. This really depends too much on your focal length (300mm refractor Vs 5000mm SCT) and your sensor (planetary camera Vs full frame sensor). So there is no given magnification.
You are right that the field of view can't be changed and hence you are limited to a certain set of objects.
But on three other hand image quality is on another level. Finding objects mainly depends on that object. Deep sky objects are normally very dim but no matter the projection method.
Clear skies!!
@@catchingphotons Thanks! Great summary!
With a focal lenght of 650 what would My field of view be if I used prime focus?
That totally depends on you imaging sensor. The two factors must be calculated together. Download "Stellarium" for PC and enter your FL and your sensor data. Stellarium shows you the field of view. Very helpful.
Clear skies!!
Do you know if there is a limit to the amount of focal lenght which can be achived by eyepiece projection? I took pictures of the moon which fitted the whole frame with a 25mm eyepiece and 650mm telescope. When adjusted the focus er on the telescope the moon never really reached complete focus. Do you know why?
Normally there shouldn't be a limit to focal length. For every given focal length there is a pair of distances (main lens eyepiece | eyepiece sensor). It might (!) be that your focus drawer can't reach (eyepiece sensor) distance but I've never heard of that.
What do you mean with: not in focus? Can you defocus in both directions or is the moon just blurry by itself? Second reason might just be bad seeing.
I'm looking forward to hearing from you.
Clear skies!!
9+ :) I wish you a mega happy night ~
Thanks!
dear Chris,
thank you for the video. can you help me clarify my problem. I use the Starsense 102mm refractor telescope, focal length is 660mm, camera i used is DSLR Canon EOS T3i, APS-C sensors, I can use prime focus for taking picture of the moon with extend tube (the tube same with tube in your video) but I can not use eyepiece projection method (i used 25mm eyepiece) i can not see any thing in my camera live view. what is wrong with my system.
Hey,
what eyepiece adapter do you use?
Did you try to use the system at prime focus using a dedicated Barlow lens?
Clear skies to you!
Chris
dear Chris,
sorry for late reply. i have found solution for my problem, it is because i removed the diagonal mirror btw telescope and eyepiece. last night i tried again with diagonal mirror then i can get focus for both eyepiece and barlow lens 2x. thank you again for your suggestion.
How do i attach my canon 700d to bresser skylux 70/700 refractor
If you scope has 1 1/4" eyepieces than you need a t-ring adapter for the canon and a t-2 to 1 1/4" adapter for attaching the camera to the eyepiece holder.
Please don't expect miracles from this scope. My advice:
Rather than plug the canon to the scope invest into a proper smartphone holder and take snaps or videos of planets and the moon with your phone though the eyepieces. I think this might be a good first entrance into this field!
Attaching the Canon will increase weight too much and probably destabilise the mount.
Clear skies!!
How do you get prime focus with just a t ring? I have heard that it's almost impossible to get focus with just a DSLR and a Newtonian.
That's normally true. If you buy a Newton scope you need to be aware wether it's made for Astrophotography or not.
The photography-Newtons are shorter - so focal point lays further outside of the focuser. Downside: you have to use simple adapters to use eyepieces but that's not too bad.
Clear skies!!
@@catchingphotons oh so you have a Newtonian made for astrophotography?
Yep it's the Skywatcher 750 150 PDS Explorer and it's shortened to fit Astrophotography. Clear skies!!
I have attached my camera with a barlow lens 2,25x to my telescope (130, 900mm) How do I know how zoomed in I am? Am I only going to be able to take planet photos? I've only used eyepiece projection before but I was never able to pick up anything from things other than planets. Will this "new" way just give me similar results? I wanted to have nothing but the barlow is the only way I can get it to attach.
Hey Adolphus,
900mmFL and 2x Barlow equals 1800mmFL and that is quite long!! So as a result the field of view is rather small.
What is the sensor size of your camera?
You can download Stellarium and enter your specs to see what the resulting field of view is. I have a tutorial for Stellarium, check it out.
Tltr: 1800mm FL is best used for tiny galaxies (super high precision tracking and super solid= expensive mount required) or for planetary (no high end mount necessary).
Clear skies!!
@@catchingphotons ok, thank you! sensor size is 13.2mm x 8.8mm, it's from 2012 and a cheap one so I think I have to get a new one.
I took a look in stellarium, I can see my field of view is way too small for large galaxies and nebulae. Finally I got an understanding of the scale, always was something I felt I missed
What's the brand name of the cam?
Great that you looked Stellarium up! Having an idea if scale is super important! You knew that Andromeda is 4-5x the full moon??? It blew my mind when I read that :-D
Clear skies!!
I don't know if anyone can help but I have tried the second method and I can't get "close" enough with the focus wheel and don't know how to fix this
Are you using a Newtonian telescope?
@@catchingphotons no it's a celestron astromatser 76
As said in the video: not every scope is built for photographic usage. Hence the rather long focal length of the eyepiece needs to intercept the focal point of the scope, the focus wheel can't be inserted enough to make prime focus possible.
There is nearly no way around:
A) use a Barlow lens BUT this will highly alter your field of view... Not best choice.
B) flex the tube shorter.... If you dare.
C) Use this scope for planetary anyway because this is what you can use your score for and just take an eyepiece and clip your phone in front. See my video about smartphone photography on my channel for more information. This is the method I'd choose.
Cheers and clear skies!
@@catchingphotons thanks this is very useful
This is a image stack of Saturn I used with an ED wide angle 15mm eyepiece and a DSLR. puu.sh/Jg0MV/e395b8d48b.png You're correct about eyepiece enhanced imaging. The eyepieces have to be of high quality or the image will indeed suffer.
Your image looks great! The quality of the optical light path is of great importance. Even with prime focus with additional Barlow you'll notice the quality of the Barlow right away (achromat Vs Apochromatic).
Thanks for sharing your result!
Cheers!
Hi, When i try to use eyepiece projection with my Canon T5i , and a 10mm super plossl the image is always completely dark, EXCEPT for the moon. Everything else is complete darkness. Any idea on what is wrong? thank you