Barlow and Camera apaptor

adam_in_perth (Adam) · #1 11-11-2013, 03:39 PM

I have recently purchased an 8" colapsable dobsonian Skywatcher telescope. I was hoping to connect my camera to it and get some moon shots to start with. Unfortunately I didnt manage to get the camera to focus. ( using a DSLR with a Tmount) After doing some reading some people said they used a barlow Lens and then managed to get the camera to focus.

I was looking at getting a barlow lens anyway and after looking through these forums I am going to go for a Bintel 2X ED 2". I then realised I need an adaptor to screw the T-mount on. so I was going to buy one from Bintel aswell (http://www.bintel.com.au/Astrophotog...oductview.aspx).

Does the barlow go straight into the telescope and then this adaptor attach to the end of the barlow lens which then enables me to screw the T-mount on the end?

Any help is greatly appreciated as I dont want to order these from over east and them to be wrong.

barx1963 (Malcolm) · #2 11-11-2013, 04:18 PM

Before ordering just check one thing. I assume the problem is that you are unable to wind the focus in enough? If it is just out of reach you can try unwinding the collimation knobs to move the primary mirror up the tube or even replace the knobs and springs with longer ones.

Another option is eyepiece projection. Bintel have an EP for this job see
http://www.bintel.com.au/Eyepieces-a...2/catmenu.aspx

Malcolm

Forgey (Paula) · #3 11-11-2013, 08:22 PM

Hi Adam, I have 12" goto collapsible skywatcher. Ive attached a pic of how I connect my DSLR.

adam_in_perth (Adam) · #4 12-11-2013, 09:59 AM

Hi Paula, That is how I connected mine. It is completely blurry though, I cant even nearly get focus. Looking at the moon is just a white blur of light. I presume it must be something to do with the camera.

Hi Malcolm, I am a complete Newb when it comes to my telescope. I wouldn't know how to move the primary mirror, and probably wouldnt want to try in case I made things worse and then couldn't use it for viewing at all.

I have a 2" eyepiece holder that is kind of like an extender, I haven't used it at all, not really sure what use it is as all my eyepieces are small and go into the adapter that attaches straight to the scope. I did try attaching the camera to it but still had the same result.

Legin (Nigel) · #5 05-12-2013, 11:35 PM

I had the same problem. The issue is the prime focus on my telescope is not long enough to meet the back of the camera (sensor) when I attach the camera.

So I figured I would try eyepiece projection. I had the same trouble it seems the afocal adapter extended the focus to much as well.

So I got a relatively low cost Plossl (13mm) and unscrewed the silver tube bit. So the eyepiece had no tube bit (if you can imagine). Then I screwed that straight into the prime focus bit of the afocal adapter I had (it allowed for either afocal or prime focus).

Then I added an extension tube and attached it to my camera via a Tmount.

I could then perform eyepiece projection. It works ok but I have to warn you to keep the eyepiece clean. Any dust will show up big time via this method.

I imagine you can replace the eyepiece with a Barlow and unscrew the end of it and attach etc. Never really tried it but you get the idea. As long as it fits inside the afocal adapter. Hmmm you would need to adjust the length of the projection to match the length of the Barlow etc. But it could work (possibly).

The other real alternative is to cut an inch or two off my telescope tube. But I am not 100% comfortable doing this to my scope at this time.

So what I use now is a 13mm Plossl eyepiece and a Afocal adapter. You can get them from most telescope shops (I got mine from Bintel just for the record). You then use the no-piece bit which is the bit that fits into the telescope it should screw off the afocal adapter. Unscrew the shiny tube off the eyepiece and screw it into the no-piece adapter. Wallah an eyepiece that fits inside an extension tube for your camera.

A bit of messing about but relatively easy enough if you get an eyepiece that fits. The Plossl's do. You can try other focal lengths to get different magnifications. But a suggestion is to keep the projection as short as possible to reduce the required exposure. The light drops off fast as you get longer projection lengths. Not really a problem most of the time but you will reach a limit where the image gets very hard to focus, if you can at all.

Not all eyepieces will work for eyepiece projection. I have had a lot of luck with a 13mm and 6mm. Just hold a piece of paper behind the eyepiece while pointing the scope at something bright, like the moon. If it projects a bit then it will likely work. You should see the image on the paper.

I hope this helps as I had to try a few different things to get an kind of photography, other than afocal digiscoping, out of my scope.

Just for the record CCD camera's will work as they have a shorter distance to the sensor. But it will cost money to get one (or at least a decent one). Then you will probably end up purchasing a Barlow anyway.

But alas like I said I hope it helps. I had a bit of an adventure through various tubes and adapters to get a combination that worked. Short of physically cutting my telescope tube that is, which will be a story for another day.

knightrider · #6 09-12-2013, 05:27 PM

Hello Adam. I'll link you my experience with the GSO/Bintel 2" ED Barlow.
http://www.iceinspace.com.au/forum/s...d.php?t=107743

Just for clarification, because its not mentioned in my thread, for my canon DSLR I use the t-adapter directly into the focuser without the 2" eyepiece adapter to reach prime focus.

The T-adapter also makes doubling the focal length by inserting it into the Barlow easy.