A bit confused

[Maclean156]

Hi. I've got an edge hd 8 and I've bought the edge hd 8 t adaptor so I can connect my dslr to it for taking pictures of planets. But pictures look so small so I need to somehow connect a barlow to the imagining train in prime focus. How do I do that? What barlow will fit the edge hd specific t adapter? 

All very confusing lol. 

[Maclean156]

Anyone? 

[jacko61]

I'd say, if you're going to be using a Barlow you'd need to use the standard visual back and 2" or 1.25" clamp.  

Graeme

[Maclean156]

Ok......so what's the point of the specific edge t adapter then......seems pointless if I need something else.....even more confused now

[jacko61]

You'd use the SCT adaptor to connect your camera directly to the tube to take photos at prime focus. As I understand it, your EDGE has a built in field flattener so to get the best out of that, the camera focal plane has to be at an exact distance from the tube thread.  here's a link - Considerations on EHD Back Focus Under Limited Seeing Conditions (innovationsforesight.com)

This is especially important when taking deep sky images where you want the stars at the edges to be as round as the stars in the centre of the frame.

With planetary imaging, you're probably not as bothered by stars at the edge so you're using a barlow to get as big a planetary image as possible - using the barlow messes up the calculations for the flattener backfocus but the planet will be at the centre of the image (which you might be cropping anyway) so it won't be affected by distortion at the edges. 

Graeme

 

 

[jacko61]

Just to add, if you do use your Barlow you would need a short nosepiece that screws into the camera's T adaptor - Astro Essentials 2" T Mount Camera Nosepiece Adapter | First Light Optics

Apologies if you already know this

Graeme

[Owmuchonomy]

Hi, what targets are you trying to image?  Your target will specify what equipment you need to attach.  A DSLR has a relatively large chip too.  If you are trying to image Jupiter for example you will need to crop your sensor right down.

[Maclean156]

If you look at my photo you will see the edge hd has a t adaptor that is specific to the edge hd 8. It is designed to give perfect back focus for a dlsr. It can also unscrew part of it so the 0.8 reducer can fit on and back focus stays the same. The answer I want is How do I connect a barlow or whatever to increase my image size with the celestron edge hd specific t adaptor? I do not want to buy a different adapter as the one I have is specifically made for the edge hd 8.

https://www.harrisontelescopes.co.uk/acatalog/celestron-t-adaptor-for-edgehd-8.html?gclid=EAIaIQobChMIncfZy9X58wIVy513Ch0h4QOREAQYAiABEgLy9PD_BwE. 

This is the t adapter I have. 

[jacko61]

As you say, the adaptor you have will give the exact back focus for your DSLR - this is for prime focus imaging and ensures that your star field is not distorted across the whole frame. This is the best set up for deep sky imaging.  If  however, you want to get planetary close ups by using a barlow (or an eyepiece for that matter), you are no longer doing prime focus imaging so the set up will be different. 

In order to use your barlow, You have to use a standard visual back, NOT the celestron T adaptor.  You would have a short nosepiece on your Camera EOS T adaptor which would then fit into the barlow.   

It looks like that celestron adaptor is in 2 halves.  If you split them, does the camera end fit into your normal visual back? (I suspect it won't as most 8" SCTs come with a 1 1/4 " visual back. ) in which case you would have a 1 1/4" barlow and a 1 1/4" nosepiece in your eos T ring such as this one - Telescope Camera Adapter 1.25 Inch (harrisontelescopes.co.uk)

You would have to make sure the thread on the adaptor matches the one on your eos T ring. 

Graeme

 

 

 

 

[Maclean156]

Ah I see what you mean. So my edge adapter is for dso. Imagining via prime focus. 

So for planets I need a t adaptor for 1 1/4 that fits my nikon(obviously I already have the nikon adaptor) . This then fits into my diagonal with the barlow. ....correct?

So my next question is what barlow and what t adapter will fit together? 

 

Thanks for all help so far guys

[Maclean156]

Oh and my t adapter when split the end won't fit into the visual back like you thought

[jacko61]

Sorry - I didn't spot the big white NIKON in your photo otherwise I'd not have mentioned EOS

The T adaptor I posted above would fit in any 1 1/4" Barlow - Telescope Camera Adapter 1.25 Inch (harrisontelescopes.co.uk)

As to what Barlow you get - WELL that's a whole different subject that I'm not equipped to answer really and I suppose a lot depends on how deep your pockets are.  I've stopped using 1 1/4" accessories and have a 2" baader clicklock visual back on my C8. My only barlow is a  2" Revelation astro 2x.  I guess you might want to browse through the forum using the search function for Barlow recommendations. 

Another option might be to use a zoom eyepiece instead - many of those have a removable rubber that reveals the 'T' thread that'll fit your Nikon adaptor. 

Graeme

 

[Maclean156]

Thanks so much. Things are a lot more clearer now. 

[catburglar]

Do you know how big the pixels are in your camera? As a rule of thumb, you want you should aim for an f-ratio between 3-5 times your pixel size….So your native f-ratio is f/10 and I’m guessing you’ve got approx 4-5micron pixels, so a decent 2x or 2.5x ED barlow should be OK- skywatcher, revelation and explore scientific are all OK in my experience. I wouldn’t bother with a 2 inch format personally unless you want to try and standardise on the larger format- I never barlow a 25mm+ eyepiece because I prefer native fl eyepieces until I get below 10mm or so and there aren’t too many short eyepieces that use the 2 inch format…

[jacko61]

13 hours ago, catburglar said:

. I wouldn’t bother with a 2 inch format personally unless you want to try and standardise on the larger format- I never barlow a 25mm+ eyepiece because I prefer native fl eyepieces until I get below 10mm or so and there aren’t too many short eyepieces that use the 2 inch format…

In case there's any misunderstanding, I wasn't suggesting using 2".  In fact my reply was excusing myself from the 1 1/4" barlow debate BECAUSE I use 2". 

Hope this clarifies matters

Graeme