Firstly just wanted to say Hi, very new to Astronomy (4 days), and picked myself up a 10" Saxon Collapsible Dobsonion telescope which I absolutely love already. Saturn and the Moon so far - I will post a Hi in one of the other threads shortly.
So I also picked up a Saxon 1.25" Variable Project Camera Adapter as I'm a very keen photographer and appropriate T-Ring for my Canon 5d. So last night as a bit of practice I setup my scope and could see the moon in all its beauty and then swapped over to the adapter with a 25mm lens inside. All good except I couldn't for the life of me get it to ever focus. I tried extending the tube on the adapter, shrinking, refocusing in many different positions but it would never focus.
Any suggestions on what I could be doing wrong here?
Hi Mobbie, Firstly, your projection adaptor will work, but the scope [unless it is the computerised Go To version] is not usable for EP
projection. Because it can't track objects, even at the scope's native
focal length of 1200mm, max exposures are fractions of a second. Even the motorised version would only allow exposures of a few seconds using projection.
You can attach a DSLR directly to the focuser with a T-ring and use it for
lunar or solar[ with a proper solar filter] imaging. Just unscrew the tube
that your eyepiece slides into from the flat plate that fits into the focuser, and screw the T-ring onto the male thread that projects from the
aforementioned flat plate. The large black collar [about 50-55mm long
with a bevel on one end is only needed when using 2" diameter
eyepieces, otherwise leave it in the box.]
raymo
Hi Mobbie, Firstly, your projection adaptor will work, but the scope [unless it is the computerised Go To version] is not usable for EP
projection. Because it can't track objects, even at the scope's native
focal length of 1200mm, max exposures are fractions of a second. Even the motorised version would only allow exposures of a few seconds using projection.
You can attach a DSLR directly to the focuser with a T-ring and use it for
lunar or solar[ with a proper solar filter] imaging. Just unscrew the tube
that your eyepiece slides into from the flat plate that fits into the focuser, and screw the T-ring onto the male thread that projects from the
aforementioned flat plate. The large black collar [about 50-55mm long
with a bevel on one end is only needed when using 2" diameter
eyepieces, otherwise leave it in the box.]
raymo
Thanks Raymo,
Completely understand on the long exposures are not possible at this stage unless GoTo or similar but at the moment just want to photograph what I see on the moon/planets where 1/250 at around 1600iso works. I just don't understand that when I have a lets say 25mm eyepiece inside the tube no matter what I do I can't get it to focus. Are you saying I don't use an eyepiece at all?
So see the picture below, lets assume they are items A to C from left to right, I only need A and C? Do I still put a eyepiece inside the tube?
Ie I was hoping to still use the eyepiece as it will control my 'zoom' so to speak.
Firstly, do you know the collar I referred to in my post? It has a bevelled end which fits into the focuser, and the other end has two chrome knobs on the side which stop a 2" eyepiece from falling out. You called it the 2" to 1.25" adaptor. It should say on the side of it " 2" eyepiece adaptor". Put this back in the box. Unscrew the 1.25" tube that your eyepiece slides into from the flat plate which fits directly into the focuser. Fit the T-ring to your camera and screw the flat plate into the female thread on the T-ring.
Hold the camera up to the focuser and tighten the knobs on the side of the focuser. You can now do prime focus imaging with a focal length of 1200mm. [good for the moon]. You can double the focal length by
using a barlow, but no room here to describe the method.
The projection adaptor is of no use to you as you can't focus without
an EP in it, so it serves no purpose, as the camera fits directly on the
focuser. Get this working first. The correct focus will be with the focuser
about 12mm from the fully in position.
raymo
Screw C directly to the focuser & attach camera
With the dob you don't need the other stuff
I have one of those projection things and only need it for refractor's
David
Screw C directly to the focuser & attach camera
With the dob you don't need the other stuff
I have one of those projection things and only need it for refractor's
David
Thanks both Raymo and David, yes worked it out finally based on Raymo's earlier post and took my first photos of the moon.
So is there any way to use the 'other stuff' so you can use an eyepiece and utilise it's zoom etc? - Reason I ask is the kids wanted to take to school a photo of what they could see in the eyepiece of Saturn, but can't see any way to do that? - I would think that a 1/250th exposure at ISO 1600 should be able to pickup what the eye can see of Saturn?
Also thanks again too and sorry for all the newbie questions!
You can try, but using an eyepiece that will pretty much duplicate what
you see, will probably necessitate you using a higher ISO than 1600 in order to give a shutter speed fast enough to freeze the planet. The planet being small, you will probably struggle to get good focus. Does your DSLR have "Live View"? if so you can magnify the planet 5 or 10 times to make focussing easier.
To do eyepiece projection put the appropriate eyepiece into the proj. adaptor, attach the adaptor to the T- ring slide the adaptor into the tube that you would normally slide an eyepiece into, and click away,[after
focussing, of course]. Leave the 2" to 1.25" adaptor in it's box.
raymo
You can try, but using an eyepiece that will pretty much duplicate what
you see, will probably necessitate you using a higher ISO than 1600 in order to give a shutter speed fast enough to freeze the planet. The planet being small, you will probably struggle to get good focus. Does your DSLR have "Live View"? if so you can magnify the planet 5 or 10 times to make focussing easier.
To do eyepiece projection put the appropriate eyepiece into the proj. adaptor, attach the adaptor to the T- ring slide the adaptor into the tube that you would normally slide an eyepiece into, and click away,[after
focussing, of course]. Leave the 2" to 1.25" adaptor in it's box.
raymo
Hi Raymo,
Thank you that's what I've thought and tried, and can get it close to in focus if I have the focuser all the way in but it seems like it needs to go a little further in to make it focus. That was my query from the start, I cant' understand why I can't get it to focus as soon as I put an eyepiece into it.
I would like to try to get it to focus even though I might not be able to take many photos until I have a goto or similar - something to save up for
The focusers on Skywatcher Newts are all the same, so the problem must lie with your adjustable adaptor. Mine is not adjustable, On mine when "A" is screwed into "B" the distance from the open end of the chrome
plated tube to the lip inside "B" that the eyepiece butts up against is 60mm. What is that dimension on yours when it is adjusted to it's minimum length? Alternatively you can as you said earlier remove the
tube from the focuser and screw the open end of "B" directly onto the
focuser; this brings the eyepiece much closer to the focuser.
raymo.
The distance between the chrome plated bit of 'A' through to the lip is about 50mm. I think I tried the other night with just 'B' screwed into the focuser but I'll try that and see what happens - I'm pretty sure that was the way I had it to get it to focus at all the way in.
Thanks for all the advise and help too, appreciate it.
You can of course mess about during the day by using something in the far distance to focus on, like a street lamp.
You will be limited to exposures of around 30 secs or less even with a Go To Dob, due to a phenomenon called field rotation. You would need an
equatorial mount for exposures longer than that.
raymo
Hi Andreas and Raymo,
Hope you don't mind me entering the conversation.
Andreas, when a target is in focus in your 'scope's e.p. the focal point/plane of your telescope is coincident on the focal plane of the e.p. In this way, the rays emitted from the e.p. are parallel and so you can obtain a projected image. An eyepiece is designed so that the light rays being emitted when focussed are parallel, that way the eye is totally relaxed and focussed on infinity. (Very important for people who spend a lot of time looking through a microscope e.p.)
Suggest you try and determine where the focal plane is on your telescope by pointing it at say, the moon and placing apiece of card at the e.p. end and finding where you have to put it to get a sharp image. This is the point at which your e.p. should also focus an image if say, for example, you allowed an image of the moon to focus on a piece of card. You should now know the correct spacing between e.p. and scope to achieve focus. Fiddle with the tubes etc. that you have to accomplish this.
Hope that's of help.
Robert
It is definitely starting to become a bit of trial and error, interesting enough when I used A+B+C on a 'distant' object just now (about 150m away) I could actually get the camera to focus, so I think as you say Robert I need to play with a card rather than connecting and disconnecting the camera until I can work it out on a card.
What I tried so far is separated B into it's two parts and looked at the EP until I got it to focus then added the camera and adjusted slightly, which is similar to the card suggestion.
- I will post a Hi in one of the other threads shortly.
